Journal of Applied and Computational MechanicsJournal of Applied and Computational Mechanics
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Feed provided by Journal of Applied and Computational Mechanics. Click to visit.An Efficient Implementation of Phase Field Method with Explicit Time Integration
http://jacm.scu.ac.ir/article_14725_1889.html
The phase field method integrates the Griffith theory and damage mechanics approach to predict crack initiation, propagation, and branching within one framework. No crack tracking topology is needed, and complex crack shapes can be captures without user intervention. In this paper, a detailed description of how the phase field method is implemented with explicit dynamics into LS-DYNA is provided. The displacement field and the damage field are solved in a staggered approach and the phase field equation is solved every Nth time step (N is refered to as calculation cycle) to save computational time. An N value smaller than 1/400 of the total time step numbers is suggested. Several simulations are presented to demonstrate the feasibility of this solving scheme.Tue, 30 Jun 2020 19:30:00 +0100Finite Element Analysis of Low Velocity Impact on Carbon Fibers/Carbon Nanotubes Reinforced ...
http://jacm.scu.ac.ir/article_14510_1889.html
An effort is made to gain insight on the effect of carbon nanotubes (CNTs) on the impact response of carbon fiber reinforced composites (CFRs) under low velocity impact. Certain amount of CNTs could lead improvements in mechanical properties of composites. In the present investigation, ABAQUS/Explicit finite element code (FEM) is employed to investigate various damages modes of nano composites including matrix cracking, fiber damage and delamination by employing Hashin’s criterion and cohesive zone modeling. The obtained results for 0, 0.5, 1, 2 and 4% CNTs demonstrate that by including CNTs in composite plates, damage could be reduced. However, adding further CNTs causes sudden reduction of impact tolerance capability of the composite plates, particularly, damage due to delamination.Tue, 30 Jun 2020 19:30:00 +0100Simple Two Variable Refined Theory for Shear Deformable Isotropic Rectangular Beams
http://jacm.scu.ac.ir/article_14620_1889.html
In this paper, a displacement-based, variationally consistent, two variable refined theory for shear deformable beams is presented. The beam is assumed to be of linearly elastic, homogeneous, isotropic material and has a uniform rectangular cross-section. In this theory, the beam axial displacement and beam transverse displacement consist of bending components and shearing components. The assumed displacement field of this theory is such that, bending components do not take part in the cross-sectional shearing force, and shearing components do not take part in the cross-sectional bending moment. This theory utilizes linear strain-displacement relations. The displacement functions give rise to the beam transverse shear strain (and hence to the beam transverse shear stress) which varies quadratically through the beam thickness and maintains transverse shear stress-free beam surface conditions. Hence the shear correction factor is not required. Hamilton’s principle is utilized to derive governing differential equations and variationally consistent boundary conditions. This theory involves only two governing differential equations of fourth-order. These governing equations are only inertially coupled for the case of dynamics and are decoupled for the case of statics. This theory is simple and has a strong resemblance with the Bernoulli-Euler beam theory. To demonstrate the efficacy of the present theory, illustrative examples pertain to the static bending and free vibrations of shear deformable isotropic rectangular beams are presented.Tue, 30 Jun 2020 19:30:00 +0100Vibration Analysis of Different Types of Porous FG Conical Sandwich Shells in Various Thermal ...
http://jacm.scu.ac.ir/article_14572_1889.html
Vibration behavior of different types of porous functionally graded (FG) conical sandwich shells are investigated based on a modified high order sandwich shells theory for the first time. Sandwich shell includes FG face sheets covering a homogeneous core and the second one includes homogeneous face sheets and a FG core. Power law rule modified by considering two types of porosity distributions is used to model the functionally graded materials. All materials are temperature dependent and uniform, linear and nonlinear temperature distributions are used to model the effect of the temperature variation in the sandwiches. Governing equations are obtained by the Hamilton's energy principle and solved with Galerkin method. To verify the results, they are compared with ones achieved by finite element method obtained by Abaqus software for special cases with the results in literatures.Tue, 30 Jun 2020 19:30:00 +0100Heat Transfer Analysis of Nanofluid Flow with Porous Medium through Jeffery Hamel ...
http://jacm.scu.ac.ir/article_14616_1889.html
In this paper, flow and heat transfer of nanofluid through a converging or diverging channel with porous medium is investigated. The fluid constantly flows under the effect of magnetic field through the channel. The diverging/converging fluid motion is modeled using the momentum and energy equations. The influence of some parameters such as opening channel angle, Reynolds number and Darcy’s number when the nanofluid flows through the non-parallel plates are studied. It is seen that high Reynolds number enhances the fluid viscosity while decreases velocity. Similarly, heat transfer reduces at high Darcy’s number owing to decreased flow consequently internal friction reduces. The obtained results in comparison with the similar studies in the literatures show satisfactory agreement.Tue, 30 Jun 2020 19:30:00 +0100On Green and Naghdi Thermoelasticity Model without Energy Dissipation with Higher Order Time ...
http://jacm.scu.ac.ir/article_14668_1889.html
In the present work, a modified model of heat conduction including higher order of time derivative is derived by extending Green and Naghdi theory without energy dissipation. We introduce two phase lag times to include the thermal displacement gradient and the heat flux in the heat conduction and depict microscopic responses more precisely. The constructed model is applied to study thermoelastic waves in a homogeneous and isotropic perfect conducting unbounded solid body containing a spherical cavity. We use the Laplace transform method to analyze the problem. The solutions for the field functions are obtained numerically using the numerical Laplace inversion technique. The results are analyzed in different tables and graphs and compared with those obtained earlier in the contexts of some other theories of thermoelasticity.Tue, 30 Jun 2020 19:30:00 +0100Thermal Buckling Analysis of Functionally Graded Euler-Bernoulli Beams with ...
http://jacm.scu.ac.ir/article_14742_1889.html
Thermal buckling behavior of functionally graded Euler-Bernoulli beams in thermal conditions is investigated analytically. The beam with material and thermal properties dependent on the temperature and position is considered. Based on the transformed-section method, the functionally graded beam is considered as an equivalent homogeneous Euler-Bernoulli beam with an effective bending rigidity under an eccentric thermal load. Then, the thermal elastic buckling equation associated with the bending deflection about the neutral axis is established. The easily usable closed-form solutions for the critical thermal buckling temperature of functionally graded beams under uniform and non-linear temperature rise are obtained and used to calculate the thermal buckling temperature. Some results are evaluated and compared with those by other investigators to validate the accuracy of the presented method. The effects of material compositions, temperature-dependent material properties, slenderness ratios and restraint conditions on thermal buckling behaviors are discussed. It is believed that the proposed model provides engineers and designers an easy and useful method to investigate the effects of various parameters affecting the thermal buckling characteristics of functionally graded beams.Tue, 30 Jun 2020 19:30:00 +0100Stability Assessment of the Flexible System using Redundancy
http://jacm.scu.ac.ir/article_14741_1889.html
In this study, dynamic behavior of a mooring line in a floating system is analyzed by probability approaches. In dynamics, most researches have shown the system model and environments by mathematical expression. We called this process as the forward dynamics. However, there is a limit to define the exact environments because of uncertainty. To consider uncertainty, we introduce the redundancy in flexible system, mooring line. For verifying the effectiveness and stability of the mooring line, criterion of axial breaking load of the mooring line is applied to joint reaction forces according to the various path of the mooring line. To cover the limits for defining the non-linearity of the environments, various responses of the mooring line along the redundancy that is used in Robotics, are derived by probability distribution. By using the Newton-Euler formulation, the inverse kinematics and the linear acceleration theorem to get joint displacements, velocities and accelerations, the joint reaction forces and moments are calculated and probability distribution of the mooring about stability and compatibility is investigated. Lastly, we simulate the flexible systems in various null motions, calculated each joint torque and force, and evaluated failure probabilities using the Monte-Carlo method.Tue, 30 Jun 2020 19:30:00 +0100Emotional Learning Based Intelligent Controller for MIMO Peripheral Milling Process
http://jacm.scu.ac.ir/article_14664_1889.html
During the milling process, one of the most important factors in reducing tool life expectancy and quality of workpiece is the chattering phenomenon due to self-excitation. The milling process is considered as a MIMO strongly coupled nonlinear plant with time delay terms in cutting forces. We stabilize the plant using two independent Emotional Learning-based Intelligent Controller (ELIC) in parallel. Control inputs are considered as forces Ux and Uy in two directions x and y, which are applied by the piezoelectrics. The ELIC consists of three elements; Critic, TSK controller and the learning element. The results of the ELIC have been compared with a Sliding Mode Controller (SMC). The simulation for the nominal plant shows better performance of the ELIC in IAE and ITSE values at least 86% in the x-direction and 79% in the y-direction. Similar simulation for an uncertain plant also shows an improvement of at least 89% in the x-direction and 97% in the y-direction.Tue, 30 Jun 2020 19:30:00 +0100A FEM Multiscale Homogenization Procedure using Nanoindentation for High Performance Concrete
http://jacm.scu.ac.ir/article_14634_1889.html
This paper aims to develop a numerical multiscale homogenization method for prediction of elasto-viscoplastic properties of a high performance concrete (HPC). The homogenization procedure is separated into two-levels according to the microstructure of the HPC: the mortar or matrix level and the concrete level. The elasto-viscoplastic behavior of individual microstructural phases of the matrix are identified from nanoindentation data using an inverse identification method. The micromechanical results are then used as input parameters for numerical elasto-viscoplastic homogenization at microscale. The mortar level is analyzed with numerical homogenization by using the finite element simulation to predict the overall elasto-viscoplastic properties of HPC. The results are compared with macroscopic experimental and analytical results from the literature showing a good agreement.Tue, 30 Jun 2020 19:30:00 +0100Using the Finite Element Analysis Method to Study the 3-point Bending Test for the ...
http://jacm.scu.ac.ir/article_14755_1889.html
An elastic finite element analysis was conducted to evaluate the stress distribution in the initiation zone of the adhesive rupture during the 3-point bending test. This test is used to measure the adherence between a polyepoxy adhesive and aluminum alloy with different surface treatments. The purpose is to compare, in the high stress concentration areas, the stress fields calculated using finite element method with the experimental data obtained in different configurations. Focusing on the load level at crack initiation, on the localization and the size of adhesive failure initiation, a local criterion for adhesive fracture is proposed based on the value of the stress normal to the interface.Tue, 30 Jun 2020 19:30:00 +0100Modelling of Love Waves in Fluid Saturated Porous Viscoelastic Medium resting over an ...
http://jacm.scu.ac.ir/article_14702_1889.html
The present article is devoted to a theoretical study on Love wave vibration in a pre-stressed fluid-saturated anisotropic porous viscoelastic medium embedded over an inhomogeneous isotropic half-space influenced by gravity. The expression of dispersion has been achieved with the help of mathematical tools such as variable separable method and Whittaker’s function’s expansion under certain boundary conditions. After that, the obtained result has been coincided with the pre-established classical equation of Love wave, as shown in the section of particular case and validation. The substantial influence of various affecting factors like gravity, initial stress, porosity, viscosity and inhomogeneity on dispersion curves of Love wave has been investigated extensively by means of graphical depictions and discussions accomplished by numerical results.Tue, 30 Jun 2020 19:30:00 +0100Numerical Scrutinization of Three Dimensional Casson-Carreau Nano Fluid Flow
http://jacm.scu.ac.ir/article_14411_1889.html
This study presents the computational analysis of three dimensional Casson and Carreau nanofluid flow concerning the convective conditions. To do so, the flow equations are modified to nonlinear system of ODEs after using appropriate self-similarity functions. The solution for the modified system is evaluated by numerical techniques. The results show the impacts of involving variables on flow characteristics and the outcomes of the friction factors are evaluated as well. In this study, the outcomes to local Nusselt number and Sherwood numbers are evaluated. Favourable comparison is performed with previously available outcomes. The achieved results are similar to solutions obtained by other researchers. The results are presented for flow characteristics in the case of Casson and Carreau fluids. Velocities are reduced for the growing values of permeability and velocity slip parameters in case of Casson and Carreau nanofluids. Temperature field enhances with the hike in the estimations of thermophoresis parameter and the thermal Biot number in case of Casson and Carreau nanofluids. Enhancing values of velocity slip parameter results in decrease in the skin friction coefficients and the rate of heat transfer, and rise in the rate of mass transfer in case of Casson and Carreau nanofluids.Tue, 30 Jun 2020 19:30:00 +0100Sealing Performance of the End Fitting of a Marine Unbonded Flexible Pipe under Pressure Penetration
http://jacm.scu.ac.ir/article_14570_1889.html
The sealing performance of end fittings is very important for offshore oil and gas pipelines. To investigate the sealing behavior of a ring-shaped wedge seal, global and local numerical models of the ring–pipe interaction have been developed based on the finite-element method. First, the sealing process of the ring under pressure is simulated. Second, a criterion for the penetration of fluid pressure is applied in these models to assess how the sealing capacity changes along the contact surface. Finally, the contact magnitude of interference and the shape of the sawtooth heaves on the sealing ring are predicted and compared. The results show an interesting concentration of von Mises stress in the sealing ring and also that the peak contact pressure appears in the sealing zone. However, the penetration of fluid pressure has obvious effects on the distributions of von Mises stress and contact pressure. The best sealing performance is when the axial displacement of the sealing ring is 1.4 mm and the contact magnitude of interference is 0.3 mm. Given the sawtooth heave of sealing ring, semicircular heave gives the better sealing capacity compared with trapezoidal heave.Tue, 30 Jun 2020 19:30:00 +0100Effect of Tool Shoulder and Pin Cone Angles in Friction Stir Welding using Non-circular Tool Pin
http://jacm.scu.ac.ir/article_14534_1889.html
In friction stir welding frictional heat is generated by the rotating tool, sliding over the stationary plate along the weld centre. Tool being the only source of heat producing member, its geometrical design influences the heat generation rate. In this present work, effects of variation in tool shoulder and tool pin taper angles on thermal history during joining are analysed. Tools with triangular and hexagonal tool pins are used to understand the influence of tool pin shape on process temperature. An analytical heat input model is developed for tools with non-circular tool pins and a comparative study is carried out between the hexagonal and triangular tool pins on temperature distribution using a three dimensional Matlab model. Proposed model is validated through experimental analysis. Apart from this, regression model based comparative study is carried out on the variation in temperature response to the change in tool pin shape, tool shoulder and tool pin taper angle.Tue, 30 Jun 2020 19:30:00 +0100Impact of Blood Vessel Wall Flexibility on the Temperature and Concentration Dispersion
http://jacm.scu.ac.ir/article_14536_1889.html
The analysis of solute and thermal dispersion in pulsatile flow through the stenotic tapered blood vessel is presented. The present problem is an extension of the work done by Ramana et al. who considered the time-invariant arterial wall. In the present model, the flexible nature of the arterial wall through the obstruction (called stenosis) is considered and it is achieved with the help of period trigonometric function. In the present study, the impact of the time-dependent arterial wall on the blood flow dynamics is discussed in details. The rheology of the blood is modeled as a couple stress fluid. The proposed fluid model is the isothermal inclusion of temperature-sensitive drug coated Titanium dioxide Nano-particles in the couple stress fluid for examining the concentration and temperature dispersion. The effects of the catheter and permeability of the stenosis are considered in the model. Care has been taken to model the thermo-physical properties of the fluid with the immersed nanoparticle, e.g., TiO2, Ag and Cu. The modeled non-linear and coupled equations are solved by using the Homotopy Perturbation Method. The temperature and concentration dispersion effects are in the flexible stenotic arterial vessel under the pulsatile physiological pressure gradient are studied and reported in details. The alterations in the axial velocity, resistance to the flow, and wall shear stress are studied and found out that the high intense vortex regions are identified in the stenotic region. The model has direct applications in the pharmaceutical industry in design and developing the drug to treat stenotic conditions.Tue, 30 Jun 2020 19:30:00 +0100Prediction of Entrance Length for Magnetohydrodynamics Channels Flow using Numerical simulation ...
http://jacm.scu.ac.ir/article_14420_1889.html
This paper focuses on using the numerical finite volume method (FVM) and artificial neural network (ANN) in order to propose a correlation for computing the entrance length of laminar magnetohydrodynamics (MHD) channels flow. In the first step, for different values of the Reynolds (Re) and Hartmann (Ha) numbers (600<ReL increases.Tue, 30 Jun 2020 19:30:00 +0100A Hybrid Particle Swarm Optimization and Genetic Algorithm for Truss Structures with Discrete ...
http://jacm.scu.ac.ir/article_14429_1889.html
A new hybrid algorithm of Particle Swarm Optimization and Genetic Algorithm (PSOGA) is presented to get the optimum design of truss structures with discrete design variables. The objective function chosen in this paper is the total weight of the truss structure, which depends on upper and lower bounds in the form of stress and displacement limits. The Particle Swarm Optimization basically modeled the social behavior of birds on the basis of the fact that Individual birds exchange information about their position, velocity, fitness, and on the basis that the behavior of the flock is then influenced to increase the probability of migration to other regions with high fitness. One of the problems of PSO is that it is easily trapped at the local point due to its non-uniform movement. The present study uses the mutation, random selection, and reproduction to reach the best genetic algorithm with the operators of natural genetics. Therefore, only identical chromosomes or particles can be converged. In other words, PSO and GA algorithm goes from one point in the search space to another point, interacting with each other. In this way, this helps them to find the optimum design by means of deterministic and probabilistic rules. The present study merged the two algorithms together in order to design several benchmark truss structures, and then the results of the new algorithm compared to those of other evolutionary optimization methods.Tue, 30 Jun 2020 19:30:00 +0100Multivariate Jeffrey Fluid Flow past a Vertical Plate through Porous Medium
http://jacm.scu.ac.ir/article_14579_1889.html
An analysis is suggested to study the impact of Hall currents in Jeffrey fluid which is chemically reactive through a porous medium limited by a semi-infinite vertical permeable plate within the existence of heat generation. An evenly distributed magnetic field turns vertically on the porous surface which absorbs the Jeffrey fluid with a changed suction velocity with time. The analytical expressions are solved by means of three terms harmonic and non-harmonic functions. Statistical calculations are carried out for the point of resultant outcomes which are shown graphically and the impacts of the parameters velocity, temperature and concentration are listed. In addition, the results of skin-friction coefficient (τ), Nusselt number (Nu) and Sherwood number (Sh) are taken in to consideration. It is revealed that the impact of the Hall parameter on the channel velocities and skin friction coefficient is subjected to the estimation of the wall suction parameter.Tue, 30 Jun 2020 19:30:00 +0100On the Six Node Hexagon Elements for Continuum Topology Optimization of Plates Carrying in ...
http://jacm.scu.ac.ir/article_14535_1889.html
The need of polygonal elements to represent the domain is gaining interest among structural engineers. The objective is to perform static analysis and topology optimization of a given continuum domain using the rational fraction type shape functions of six node hexagonal elements. In this paper, the main focus is to perform the topology optimization of two-dimensional plate structures using Evolutionary Swarm Intelligence Firefly Algorithms (ESIFA) and three-dimensional shell structures using optimality criteria. The optimization of plates carrying in plane loading is performed with minimum weight as objective. Two different types of shell structures are optimized using maximum strain energy as criteria. The optimal distribution of the material in the design domain obtained using six node hexagon elements is compared with the optimal distribution of material obtained using quadrilateral elements. A few problems from the literature have been solved and this study has proved that hexagon element gives better results over traditional quadrilateral elements.Tue, 30 Jun 2020 19:30:00 +0100Fluid Flow and Heat Transfer over Staggered ꞌ+ꞌ Shaped Obstacles
http://jacm.scu.ac.ir/article_13989_0.html
The inclusion of complex obstacles within solar channels is the aim of this article. Two obstacles of the form ꞌ+ꞌ interlaced within a two-dimensional and rectangular channel are the subject of our study. The fluid is Newtonian, turbulent, incompressible and has constant properties. The Reynolds number varies from 12,000 to 32,000 with a constant temperature along the upper surface of the channel. The thermal and dynamic analysis of the channel's internal structure has been carefully processed. Different fields of speed and heat, with various profiles of frictions and heat exchange coefficients, have been included in this research. Future work will involve more complex geometries and using nanofluids to assess the optimum conditions for heat transfer enhancements.Fri, 14 Dec 2018 20:30:00 +0100Effects of Non-uniform Suction, Heat Generation/Absorption and Chemical Reaction with ...
http://jacm.scu.ac.ir/article_14765_1889.html
In the present investigation, the magnetohydrodynamic Falkner-Skan flow of tangent hyperbolic nanofluids over a stretching/shrinking wedge with variable suction, internal heat generation/absorption and chemical reaction with activation energy have been scrutinized. Nanofluid model is composed of “Brownian motion’’ and “Thermophoresis’’. Transformed non-dimensional coupled non-linear equations are solved by adopting the fourth-order R-K method along with the shooting technique. A comprehensive analysis of nanofluid velocity, the relative temperature, and its concentration profiles has been addressed. The major outcomes of the current study include that augmentation in the Weissenberg parameter, Hartmann number along with suction impede fluid flow and the shrinkage of the related boundary layer while internal heating develops an ascending thermal boundary layer for static and moving (stretching/shrinking) wedge. An increment in reaction rate undermines the nanoparticle concentration while that of activation energy exhibits a reverse trend.Tue, 30 Jun 2020 19:30:00 +0100Non-similar Solutions of MHD Mixed Convection over an Exponentially Stretching Surface: ...
http://jacm.scu.ac.ir/article_14133_0.html
In this paper, an analysis of magnetohydrodynamic (MHD) mixed convection over an exponentially stretching surface in the presence of a non-uniform heat source/sink and suction/injection is presented. The governing boundary layer equations are transformed into a set of non-dimensional equations by using a group of non-similar transformations. The resulting highly non-linear coupled partial differential equations are solved by using the implicit finite difference method in combination with the quasilinearization technique. Numerical results for the velocity, temperature and concentration profiles, as well as the skin friction coefficient, wall heat transfer and mass transfer rates are computed and presented graphically for various parameters. The results indicate that the velocity profile reduces, while the temperature profile increases in presence of the effects of magnetic field and suction at the wall. The velocity ratio parameter increases the skin-friction coefficient and the Schmidt number decreases the wall mass transfer rate. The temperature profile increases for the positive values of Eckert number and space as well as temperature dependent heat source/sink parameters, while the opposite behavior is observed for negative values of same parameters.Mon, 18 Feb 2019 20:30:00 +0100Effect of Chemical Reaction on Bioconvective Flow in Oxytactic Microorganisms Suspended Porous ...
http://jacm.scu.ac.ir/article_14811_1889.html
In this paper, the bioconvective flow in a porous square cavity containing oxytactic microorganism in the presence of chemical reaction is investigated. The bioconvection flow and heat transfer in porous media are formulated based on the Darcy model of Boussinesq approximation. The governing partial differential equations are solved using the Galerkin finite element method. The computational numerical results are exhibited by the streamlines, isotherms, isoconcentrations of oxygen, isoconcentrations of microorganisms, average Nusselt number, average Sherwood numbers of oxygen concentration and microorganisms. The effects of key parameters such as bioconvection Rayleigh number (Rb), chemical reaction parameter (Kr) and thermal Rayleigh number (Ra) are presented and analyzed. It can be deduced that the chemical reaction reduces the strength of isoconcentrations of both oxygen and microorganisms. It has been revealed that the chemical reaction has a greater effect on the swimming of the microorganisms, average Nusselt number, and average density number.Tue, 30 Jun 2020 19:30:00 +0100Nonlinear Buckling and Post-buckling of Shape Memory Alloy Shallow Arches
http://jacm.scu.ac.ir/article_15083_1889.html
In this work, the nonlinear buckling and post-buckling behavior of shallow arches made of Shape Memory Alloy (SMA) is investigated. Arches are susceptible to large deflections, due to their slenderness, especially when the external load exceeds the serviceability limit point. Beyond this, loss of stability may occur, the famous snap-through buckling. For this reason, curved beams can be used in passive vibration control devices for seismic response mitigation, and the geometrically nonlinear analysis is needed for the accurate prediction of their response. Thus, in this research effort, the assumptions of the Euler-Bernoulli beam theory are considered, and the Von Karman strain field is employed to account for large deflections. The formulation of the problem is displacement-based regarding the axial (tangential) and transverse (normal) displacements, while the two governing equations are coupled and nonlinear. In order to introduce the SMA constitutive law, the stress-strain experimental curves described in the literature are employed together with a fiber approach at specific control cross-sections along the beam. The numerical solution of the longitudinal problem is achieved using the Analog Equation Method (AEM), a Boundary Element Method (BEM) based technique, and the iterative procedure is based on a Newton-Raphson scheme by using a displacement control algorithm to trace the fully nonlinear equilibrium path and overcome the limit points. Several representative examples are studied, not only to validate the proposed model but also to investigate the nonlinear buckling and post-buckling of SMA shallow arches.Tue, 30 Jun 2020 19:30:00 +0100Laplace Variational Iteration Method for Modified Fractional Derivatives with Non-singular Kernel
http://jacm.scu.ac.ir/article_15045_1889.html
A universal approach by Laplace transform to the variational iteration method for fractional derivatives with the nonsingular kernel is presented; in particular, the Caputo-Fabrizio fractional derivative and the Atangana-Baleanu fractional derivative with the non-singular kernel is considered. The analysis elaborated for both non-singular kernel derivatives is shown the necessity of considering the modified Caputo-Fabrizio fractional derivative and the analogous modifications for the Atangana-Baleanu fractional derivative with non-singular Mittag-Leffler kernel in order to satisfy the initial conditions for some fractional differential equations.Tue, 30 Jun 2020 19:30:00 +0100The Density-Driven Nanofluid Convection in an Anisotropic Porous Medium Layer with Rotation and ...
http://jacm.scu.ac.ir/article_15222_1889.html
In this study, a numerical examination of the significance of rotation and changeable gravitational field on the start of nanofluid convective movement in an anisotropic porous medium layer is shown. A model that accounts for the impact of Brownian diffusion and thermophoresis is used for nanofluid, while Darcy’s law is taken for the porous medium. The porous layer is subjected to uniform rotation and changeable downward gravitational field which fluctuates with the height from the layer by linearly or parabolic. The higher-order Galerkin technique is applied to obtain the numerical solutions. The outcomes demonstrate that the rotation parameter TD, the thermal anisotropy parameterh and the gravity variation parameter λ slow the beginning of convective motion, whereas the mechanical anisotropy parameter ξ, the nanoparticle Rayleigh-Darcy number Rnp, the modified diffusivity ratio NAnf and the modified nanofluid Lewis number Lenf quick the start of convective motion. For instance, by rising the gravity variation parameterfrom zero to 1.4, the critical nanofluid thermal Rayleigh-Darcy number Rnf,c and the critical wave numberboost maximum around 133% and 7%, respectively for linear variation of the gravity field, while it were 47% and 2.8% for parabolic variation of the gravity field. It is also observed that the system is more unstable for the parabolic variation of the gravity field. Tue, 30 Jun 2020 19:30:00 +0100Designing and Creating a Mouse Using Nature-Inspired Shapes
http://jacm.scu.ac.ir/article_14621_0.html
Human beings have always made their tools and instruments they need using patterns in nature. Mimicking nature has become the foundation of a new science called Biomimetics. In the present article, multiple forms and levels in nature were utilized to design and create a mouse. The rivers are a good source for choosing the shape of a mouse with lots of stones abraded through the centuries which also have smooth surfaces. In this research, a significant number of stones fitted to hand size were collected and then the best ones were scanned by an optical scanner. The point cloud model obtained was used to design and create the mouse and determine the geometric parameters of the mouse. After extracting the 3D model of the point cloud using a rapid prototyping technique with the Fused Deposition Modeling (FDM) method, some mouse models were designed ambidextrously for left-handed and right-handed people. Considering the results of the mouse evaluation by 30 people who were provided with the mouse, it can be concluded that the created mouse provided a high rate of satisfaction.Sat, 27 Jul 2019 19:30:00 +0100Numerical Simulation of Unsteady Flow toward a Stretching/Shrinking Sheet in Porous Medium ...
http://jacm.scu.ac.ir/article_14641_0.html
The purpose of this study is to present simulation and numerical solutions to the unsteady flow and heat transfer near stagnation point over a stretching/shrinking sheet in porous medium filled with a hybrid nanofluid. Water (base fluid), nanoparticles of titania and copper were considered as a hybrid nanofluid. It is worth mentioning that evaluating the heat transfer enhancement due to the use of hybrid nanofluids has recently become the center of interest for many researchers. The coupled non-linear boundary-layer equations governing the flow and heat transfer are derived and reduced to a set of coupled non-dimensional equations using the appropriate transformations and then solved numerically as a nonlinear boundary value problem by bvp4c scheme from MATLAB. To validate the modeling of hybrid nanofluid and also numerical procedure, the value of the skin friction and the heat transfer rate for the limited cases of pure water, titania/water and copper/water is obtained and compared with previously reported results that demonstrate an excellent agreement. In the present investigation, the thermal characteristics of hybrid nanofluid are found to be higher in comparison to the base fluid and fluid containing single nanoparticles, respectively. It can be concluded that both skin friction coefficient and local Nusselt number enhance almost linearly with increasing the copper nanoparticle volume fraction (as second nanoparticle). Besides, the porosity and the magnetic effect amplify heat transfer rate, while the unsteadiness parameter has a reducing effect on heat transfer rate in problem conditions.Sat, 03 Aug 2019 19:30:00 +0100Multiple Solutions for Slip Effects on Dissipative Magneto-Nanofluid Transport Phenomena in ...
http://jacm.scu.ac.ir/article_14645_0.html
In the present paper, a numerical investigation of transport phenomena is considered in electrically-conducting nanofluid flow within a porous bed utilizing Buongiorno’s transport model and Runge-Kutta-Fehlberg fourth-fifth order method. Induced flow by non-isothermal stretching/shrinking sheet along with magnetic field impact, dissipation effect, and slip conditions at the surface are also included. The numerical results show the existence of two branches of the solution for a selected range of the governing parameters. The physical significance of both branches of solutions is ensured by performing a stability analysis in which a linearized eigenvalue problem is solved. The multiple regression analysis with the help of MATLAB LinearModel.fit package has also been conducted to estimate the dependence of the parameters on Nusselt number.Thu, 08 Aug 2019 19:30:00 +0100Dynamic Analysis of the Biomechanical Model of Head Load Impact Using Differential Transform Method
http://jacm.scu.ac.ir/article_14666_0.html
The dynamic analysis of the biomechanical model of the head load impact using the Differential Transform Method is presented in this paper. In many parts of the world, the problem of traumatic brain injuries (TBI) has led to neurodegenerative dementing disorders and diseases as a result of head load impact from sporting activities, accidents involving the head, etc. have serious effects on humanity. The head load impact and its control have been modeled as a rigid linkage head-neck manipulator. This rigid link manipulator is governed by a system of nonlinear ordinary differential matrix equations with three degrees of freedom which requires special techniques for its solution. The system of equations was solved using Differential Transform Method (DTM) and the results were compared with results obtained in earlier studies and validated with the fourth-order Runge-Kutta numerical method (RK4). Good agreements are reached in all these results. From the model, the effects of head loads, head mass, neck mass, upper and lower linkage lengths, head and neck moments of inertia were investigated. As the head loads increased, there were increases in both axial and angular displacement of the head motion and the neck region. The study provides a theoretical basis for the design and understanding of the effects of head load carriage on vital organs that are susceptible to pains, damages, and even failure.Tue, 20 Aug 2019 19:30:00 +0100Comprehensive Investigating on the Aerodynamic Influences of the Wheel Contact Patch
http://jacm.scu.ac.ir/article_14700_0.html
Computational fluid dynamics is implemented to investigate the influence of the wheel contact patch on the global car aerodynamics. Two main aspects of the problem are the contact step and patch shape. Three important parameters: step height, cut angle, and tire tread shape are taken into consideration. For validations of the numerical results, the experimental data are also considered. The obtained results show that the step height may not significantly affect the global flow field. But when the cut angle increases, the flow separations on the two sides of the front wheel patch will be suppressed successively, which generates two critical points and a sudden drag decrease is achieved. Besides, tiny differences in tread shape can effectively change the flow rate of the underbody and make a huge drag discrepancy in the results. In conclusion, the cut angle and tire tread shape carefully must be dealt with in aerodynamic applications of automotive engineering.Wed, 28 Aug 2019 19:30:00 +0100Experimental and Numerical Buckling Analysis of Carbon Fiber Composite Lattice Conical ...
http://jacm.scu.ac.ir/article_14704_0.html
In this research, the numerical and experimental analysis of the carbon fiber composite lattice conical structure has been performed to assess the buckling stability of the structure before and after the lateral impact. In the experimental analysis, the carbon fiber composite lattice conical structure was constructed with the winding method and using elastic molds and metal mandrel. In order to investigate the buckling stability of the structures before each lateral impact, they are subjected to be compressive-axial loading. The rest of the structures first subjected under the axial-compressive loading, then in the next step, a compressive loading is applied to determine the effect of the impact on the compressive strength of the damaged structures. In the numerical analysis, the Abaqus software is used to modeling and performing the mentioned analysis. Finally, the comparison of the results shows that the effect of the lateral impact causes how many reductions will be occurred in the buckling strength. So, it should be considered during the design of the applied structures. On the other hand, the low difference between the numerical and experimental simulations shows that the experimental and numerical methods can be used to analyze the structures with different geometric characteristics and material.Sat, 31 Aug 2019 19:30:00 +0100Optimization of the Prismatic Core Sandwich Panel under Buckling Load and Yield Stress ...
http://jacm.scu.ac.ir/article_14740_0.html
In this study, weight optimization of the prismatic core sandwich panel under transverse and longitudinal loadings has been independently investigated. To solve the optimization problems corresponding to the mentioned loadings, a new Improved Constrained Differential Evolution (ICDE) algorithm based on the multi-objective constraint handling method is implemented. The constraints of the problems are buckling load and yield stress. By comparing the results of the ICDE with those obtained by the other evolutionary algorithms based on the penalty function method in the previous studies, it is discerned that the results of the transverse loading obtained in this study are equal to those of the previous works, but the results of the ICDE in the longitudinal loading are better.Thu, 12 Sep 2019 19:30:00 +0100Mechanics of 2D Elastic Stress Waves Propagation Impacted by Concentrated Point Source ...
http://jacm.scu.ac.ir/article_14748_0.html
Green’s function, an analytical approach in inhomogeneous linear differential equations, is the impulse response, which is applied for deriving the wave equation solution in composite materials mediums. This paper investigates the study of SH wave’s transmission influenced by concentrated point source disturbance in piezomagnetic material resting over heterogeneous half-space. Green function approach is used to solve differential equation and obtain the dispersion relation in determinant form and match with existing classical Love wave equation for the authenticity for the article. The properties of SH wave throughout the considered framework and their state of relying on varied geometrical and physical parameters are scrutinized. The simulated outcomes of disparate physical quantities viz., dimensionless phase velocity, elastic parameter, group velocity, initial stress, piezomagnetic/heterogeneity parameter and stress distribution of SH wave in the considered structure are investigated and used to regulate the behavior of dispersion characteristics of smart material waveguides.Fri, 13 Sep 2019 19:30:00 +0100Three Dimensional Non-linear Radiative Nanofluid Flow over a Riga Plate
http://jacm.scu.ac.ir/article_14751_0.html
Numerous techniques in designing zones happen at high temperature and functions under high temperature are in a way that involves non-linear radiation. In weakly conducting fluids, however, the currents induced by an external magnetic field alone are too small, and an external electric field must be applied to achieve an efficient flow control. Gailitis and Lielausis, devised Riga plate to generate a crossed electric and magnetic fields which can produce a wall parallel Lorentz force in order to control the fluid flow. It acts as an efficient agent to reduce the skin friction. So, in this paper, we start the numerical investigation on the three-dimensional flow of nanofluids with the inclusion of non-linear radiation past a Riga plate. To this end, the numerical investigation is conducted on the three-dimensional flow of nanofluids with the inclusion of non-linear radiation past a Riga plate. Water (H2O) and Sodium Alginate (NaC6H9O7) are the base fluids, whereas Magnetite (Fe3O4) and Aluminium oxide (Al2O3) are the nanoparticles. The mathematical formulation for Sodium Alginate base fluid is separated through the Casson model. Suitable transformations on governing partial differential equations yield strong non-linear ordinary differential equations. Numerical solutions for the renewed system are constructed by fourth-order Runge-Kutta method with shooting technique. Various deductions for flow and heat transfer attributes are sketched and discussed for various physical parameters. Furthermore, the similarities with existing results were found for the physical quantities of interest. It was discovered, that the temperature ratio parameter and the radiation parameter enhance the rate of heat transport. Moreover, the NaC6H9O7 - Al2O3 nanofluid improves the heat transfer rate. Likewise, H2O-Fe3O4 nanofluid stimulates the local skin friction coefficients.Sat, 14 Sep 2019 19:30:00 +0100Experimental Study of the Heat Transfer Enhancement in Concentric Tubes With Spherical and ...
http://jacm.scu.ac.ir/article_14754_0.html
In the current research project, the thermal performance of a series of newly designed mixers has been investigated. Each mixer has two concentric cylinders comprising two annular slot flow channels around a solid cylindrical rod at the center. In each mixer, the first cylinder around the central solid rod has either spherical or pyramidal protrusions throughout the outer surface. It has been observed that with varying mass flow rate of cold and hot water (1 kg/m3-sec to 5 kg/m3-sec), 17% increase in rate of heat transfer for cold water & 73% for hot water has been observed with a variation in mass flow rate of 1-3 kg/m3-sec with all combination of angles of holes in spherical protrusions. In the case of pyramidal protrusions, the rate of heat transfer has been raised from 16% for cold water & 88% for hot water at varying a mass flow rate of 1-3 kg/m3-sec in all combinations of angles of the top vortex in each protrusion. The effect of imparting the centrifugal force has raised the rates of heat transfer in the range of 24-36% at varying rpm from 60-180 rpm of the central cylinder, with the highest with 120 rpm. A comparison of the heat transfer rates reveals that with increasing the mass flow rates, rpm, angle of the holes in spherical protrusions and angle of the traversed angle at the top corner of each pyramidal protrusion didn’t contribute linearly in terms of rising in the rate of heat transfer.Sun, 15 Sep 2019 19:30:00 +0100Traveling Wave Solutions of 3D Fractionalized MHD Newtonian Fluid in Porous Medium with Heat ...
http://jacm.scu.ac.ir/article_14757_0.html
In the present paper, we get exact solutions of Magnetohydrodynamic (MHD) of the fractionalized three-dimensional flow of Newtonian fluid with porous and heat transfer through the traveling wave parameter. The governing equations are produced dependent on established Navier-stokes equations which can be diminished to ordinary differential equation by wave parameter ξ=ax+by+nz+Utα/Γ(α+1). The new exact solutions are established for three various cases. In special cases the solution for Newtonian fluid with and without MHD and porous effects can also be found from the general solution by putting M+Φ→0 and solutions for simple Newtonian fluid can also be obtained by putting α→1 in general solutions. Finally, the effect of the parameter of interest on the stream motion, as well as difference among the Newtonian fluids is examined by 2D and 3D graphical interpretations. Tue, 17 Sep 2019 19:30:00 +0100Magnetohydrodynamics Fluid Flow and Heat Transfer over a Permeable Shrinking Sheet with Joule ...
http://jacm.scu.ac.ir/article_14759_0.html
A laminar, two dimensional, steady boundary layer Newtonian conducting fluid flow passes over a permeable shrinking sheet in the presence of a uniform magnetic field is investigated. The governing equations have converted to ordinary nonlinear differential equations (ODE) by using appropriate similarity transformations. The main idea is to transform ODE with infinite boundary condition into other sets of variables in a way that infinite boundary condition becomes a finite boundary condition. The effects of physical parameters affecting the velocity and temperature are shown. The results show that with increasing the magnetic and suction parameters, the normal velocity component of fluid increases over the sheet whereas the tangential velocity component of fluid decreases. Moreover, when the suction parameter, the Prandtl and Eckert numbers increase, the rate of the heat transfer increases. However, when the magnetic parameter increases, the rate of heat transfer reduces. Finally, the solution shows that the results of the analytical method using a special technique have an excellent agreement with numerical solutions.Wed, 18 Sep 2019 19:30:00 +0100Dufour and Soret Effects on Unsteady Heat and Mass Transfer for Powell-Eyring Fluid Flow over ...
http://jacm.scu.ac.ir/article_14762_0.html
In the present analysis, the Dufour and Soret effects on unsteady heat-mass transfer of a viscous incompressible Powell-Eyring fluids flow past an expanding/shrinking permeable sheet are reported. The fluid boundary layer develops over the variable sheet with suction/injection to the non-uniform free stream velocity. Under the symmetry group of transformations, the governing equations along with three independent variables, are converted into a system of PDEs with two independent variables. Finally, by employing the order-reduction technique the PDEs are transformed into ODEs, which are then solved numerically. The results are presented graphically and analyzed. The main advantage of this technique is that without any prior knowledge, one can easily find the scaling transformations, expanding velocity, suction/injection velocity, and free-stream velocity. From computed numerical results many important findings are obtained. Most importantly, thermal and concentration overshoots are found for larger values of Dufour and Soret numbers, respectively. Also, thermal and concentration crossing over found for different values of Soret and Dufour numbers, respectively.Sat, 21 Sep 2019 20:30:00 +01003D Optimization of Gear Train Layout Using Particle Swarm Optimization Algorithm
http://jacm.scu.ac.ir/article_14764_0.html
Optimization of the volume/weight in the gear train is of great importance for industries and researchers. In this paper, using the particle swarm optimization algorithm, a general gear train is optimized. The main idea is to optimize the volume/weight of the gearbox in 3 directions. To this end, the optimization process based on the PSO algorithm occurs along the height, length, and width of the gearbox to achieve the smallest possible gearbox. The constraints are divided into three types named geometrical, design and control constraints. The optimization process is presented for two and three-stage gear trains and by choosing different values for the gear ratio, input power and hardness of gears. The practical graphs for the optimum value of the weight/volume and all necessary design parameters of gearbox such as the number of stages, position, modulus of gears, face width of gears, and diameter of shafts are also presented. The results are validated by comparing with the results reported in the previous publications.Sun, 22 Sep 2019 20:30:00 +0100On Approximate Stationary Radial Solutions for a Class of Boundary Value Problems Arising in ...
http://jacm.scu.ac.ir/article_14788_0.html
In this paper, we consider a non-self-adjoint, singular, nonlinear fourth order boundary value problem which arises in the theory of epitaxial growth. It is possible to reduce the fourth order equation to a singular boundary value problem of second order given by w''-1/r w'=w^2/(2r^2 )+1/2 λ r^2. The problem depends on the parameter λ and admits multiple solutions. Therefore, it is difficult to pick multiple solutions together by any discrete method like finite difference method, finite element method etc. Here, we propose a new technique based on homotopy perturbation method and variational iteration method. We compare numerically the approximate solutions computed by Adomian decomposition method. We study the convergence analysis of both iterative schemes in C^2 ([0,1]). For small values of λ, solutions exist whereas for large values of λ solutions do not exist.Fri, 27 Sep 2019 20:30:00 +0100Optimum Design of Liquified Natural Gas Bi-lobe Tanks using Finite Element, Genetic Algorithm ...
http://jacm.scu.ac.ir/article_14801_0.html
A comprehensive set of ten artificial neural networks is developed to suggest optimal dimensions of type ‘C’ Bi-lobe tanks used in the shipping of liquefied natural gas. Multi-objective optimization technique considering the maximum capacity and minimum cost of vessels are implemented for determining optimum vessel dimensions. Generated populations from a genetic algorithm are used by Finite Element Analysis to develop new models and find primary membrane and local stresses to compare with their permissible ranges using PYTHON coding. The optimum design space is mathematically modeled by training ten artificial neural networks with design variables generated by the Taguchi method. The results are compared with actual design data and the 93% achieved accuracy shows the precision of the developed design system.Sun, 06 Oct 2019 20:30:00 +0100Torsional Aeroelasticity of a Flexible VAWT Blade using a Combined Aerodynamic Method by ...
http://jacm.scu.ac.ir/article_14789_0.html
The present research investigates the torsional aeroelasticity of the blade of an H-type vertical axis wind turbine subject to stall and post-stall conditions in various Reynolds regimes, which is experienced by the blade in a full revolution. In order to simulate the aerodynamics, a new model based on a combination of the Double Multi Streamtubes (DMST) model and the nonlinear multi-criteria Cl-a equations, which is depended on the local Reynolds number of the flow, has been proposed. The results indicate that using of multi-criteria function dependent on the Reynolds number for the Cl-a curve has improved the prediction of the torsional behavior of the blade in azimuthal rotation of the blade compared to using single-criterion functions and linear aerodynamics. The blade’s aeroelastic torsion has been studied for various TSR values.Sat, 28 Sep 2019 20:30:00 +0100Influence of Temperature Pulse on a Nickel Microbeams under Couple Stress Theory
http://jacm.scu.ac.ir/article_14800_0.html
In this paper, the vibration of microbeams due to a temperature pulse has been investigated. The thermoelastic coupled equations for microbeam resonator have been derived via the modified theory of couple stress in connection with the generalized thermoelasticity with relaxation time. The analytical expressions for studied fields due to modified couple stress for the microbeam have been obtained by applying the Laplace transform method. In addition, some comparisons have been displayed in graphs to estimate the effects of different parameters such as the couple stress parameter and pulse of temperature on the considered fields. Numerical conclusions demonstrate that the estimation of deflection expected by the new theory is lower than that of the classical one. Comparisons are made with the results of different models in the absence and presence of couple stress theory. Particular cases of interest are also derived.Wed, 02 Oct 2019 20:30:00 +0100Numerical Solution of Caputo-Fabrizio Time Fractional Distributed Order Reaction-diffusion ...
http://jacm.scu.ac.ir/article_14803_0.html
In this paper, we derive a novel numerical method to find out the numerical solution of fractional partial differential equations (PDEs) involving Caputo-Fabrizio (C-F) fractional derivatives. We first find out the approximation formula of C-F derivative of function tk. We approximate the C-F derivative in time with the help of the Legendre spectral method and approximation formula of tk. The unknown function and their derivatives in spatial direction are approximated with the quasi wavelet-based numerical method. We apply this newly derived method to solve the nonlinear distributed order reaction-diffusion in which time-fractional derivative is of C-F type. The accuracy and validity of the proposed method is exhibited by giving a solution to some numerical examples. The obtained numerical results are compared with the analytical results and conclude that our proposed numerical method achieves accurate results. On the other hand, the method is easy to apply on higher-order fractional partial differential equations and variable-order fractional partial differential equations.Tue, 08 Oct 2019 20:30:00 +0100MHD Casson Nanofluid Past a Stretching Sheet with the Effects of Viscous Dissipation, Chemical ...
http://jacm.scu.ac.ir/article_14804_0.html
The effects of viscous dissipation, chemical reaction and activation energy on the two-dimensional hydromagnetic convective heat and mass transfer flow of a Casson nanofluid fluid over a stretching sheet with thermal radiation, have been discussed in detail. The formulated highly nonlinear equations for the above-mentioned flow are converted into first-order ordinary differential equations (ODEs). The shooting method along with Adams-Bash forth Moulton method is used to solve the BVP by using the Fortran language program. The numerical results are computed by choosing different values of the involved physical parameters and compared with earlier published results and excellent validation of the present numerical results has been achieved for local Nusselt number and local Sherwood number. The graphical numerical results of different physical quantities of interest are presented to analyze their dynamics under the varying physical quantities. From the results, it has been remarked that the heat transfer rate escalates for the large values of radiation parameter, viscous dissipation for the Casson nanofluid.Tue, 08 Oct 2019 20:30:00 +0100Variational Principle for the Generalized KdV-Burgers Equation with Fractal Derivatives for ...
http://jacm.scu.ac.ir/article_14813_0.html
The unsmooth boundary will greatly affect motion morphology of a shallow water wave, and a fractal space is introduced to establish a generalized KdV-Burgers equation with fractal derivatives. The semi-inverse method is used to establish a fractal variational formulation of the problem, which provides conservation laws in an energy form in the fractal space and possible solution structures of the equation.Fri, 11 Oct 2019 20:30:00 +0100Heat Transfer of Hybrid-nanofluids Flow Past a Permeable Flat Surface with Different Volume ...
http://jacm.scu.ac.ir/article_14842_0.html
Nowadays, the preparation, characterization, and modeling of nanofluids are deliberated in plenty to improve the heat transfer effects. Therefore, this paper centers on the heat transfer effects of three separate hybrid nanoparticles such as Al2O3-SiO2, Al2O3-TiO2, and TiO2-SiO2 with a base fluid such as water to gratify the advances. Analytical investigations for the Marangoni convection of different hybrid nanofluids over the flat surface for the cases such as suction, injection and impermeable were analyzed. A validation table for the comparison between analytical and numerical studies is tabulated. The influence of the hybrid nanoparticles solid volume fraction and the wall mass transfer parameter are mentioned through graphs at the side of the heat transfer rate tabulation. The impact of solid volume fraction decelerates the velocity distribution and raises the temperature distribution for all the three hybrid nanofluids in the cases of suction, impermeable, and injection. While relating the surface velocity and heat transfer rate of the three hybrid nanofluids, Al2O3-SiO2/water has a higher surface velocity, TiO2-SiO2/water has a higher heat transfer rate and Al2O3-TiO2/water has lower surface velocity and heat transfer rate for the increment of wall mass transfer parameter.Tue, 15 Oct 2019 20:30:00 +0100Stress Intensity Factor Expression for Welded Butt Joint with Undercut and Inclined Lack of ...
http://jacm.scu.ac.ir/article_14847_0.html
In this paper, the stress intensity factor (SIF) expression for defected butt welds containing undercut and inclined lack of penetration (LOP) subject to far-field tensile stress is derived. Some of the standards such as ISO 5817 and BS EN 25817 have specified allowable limits for the length of the undercut and LOP defects and for the height of the weld. In addition, EN 29692 standard has determined an acceptable range for the groove angle. In this paper, the effect of these acceptable geometries on stress intensity factor (SIF) of butt welded joint is investigated through following steps: i) elastic analyses to predict crack tip stress intensity (KI, KII) and shape factors, ii) approximation of shape factors by Response Surface Method (RSM). These expressions provide design guidelines for welded butt joint containing unavoidable undercut and inclined lack of penetration (LOP) defects.Wed, 16 Oct 2019 20:30:00 +0100The Optimal Design of Heat Sinks: A Review
http://jacm.scu.ac.ir/article_14852_0.html
Heat sinks are used in industrial equipment to dissipate the excess heat from their heat-generating parts to the ambient. In the last few years, efforts on manufacturing electronic or mechanical devices with less weight, space, and lower cost were spent. Heat dissipation from the heat sink is stalling a big problem which many researchers are trying to solve. The aim of this study is to brief the previous investigation attempted enhancing the heat sinks thermal performance and to provide help to understand the cooling ability of their specific geometries. The various enhancement techniques used for optimizing the hydrothermal design of a pin fin, flat fin, micro-channel, and topology optimized heat sinks were summarized. The way in which the heat sinks’ thermal performance is affected by orientation, shapes, perforation, slot, interruption, and space between fins and their arrangement under free and forced convection condition also reviewed.Sat, 19 Oct 2019 20:30:00 +0100Free Vibration Analysis of Functionally Graded Beams with Cracks
http://jacm.scu.ac.ir/article_14878_0.html
This study introduces the free vibration analysis of multilayered symmetric sandwich Timoshenko beams, made of functionally graded materials with two edge cracked, using the finite element method and linear elastic fracture mechanic theory. The FG beam consists of 50 layers, located symmetrically to the neutral plane, whose material properties distribution change along the beam thickness, according to power and exponential laws. The constituent of each layer of the beam is different, but each layer is isotropic and homogeneous. Natural frequency values of a cantilever beam are calculated using a developed MATLAB code. There is good agreement between the present results and the published results from the literature. A detailed study is carried out to observe the effect of crack location, crack depth ratio, power law index and material distribution on the first four natural frequencies.Wed, 23 Oct 2019 20:30:00 +0100Topology Optimization of Laminated Composite Plates and Shells using Optimality Criteria
http://jacm.scu.ac.ir/article_14895_0.html
Laminated composite materials have the advantage of desired properties and are vastly replacing the existing traditional materials in Civil Engineering construction. In the present study, it is aimed to extend the study on the analysis of laminated composites plates and shells towards structural optimization. Topology optimization is performed using two different objective functions namely strain energy and fundamental frequency. The results of optimization have shown clearly that the distribution of material is dependent on the laminae. The optimal arrangement of material is obtained after using a cut-off relative density. It is confirmed to be a well-connected grid and is examined in detail. The results have shown that the optimal arrangement of material for a simply supported plate carrying a uniformly distributed load is at the centre of the edges and not towards the corners, Hence, the optimal arrangement of beams using strain energy is to align by joining the centre of the edges similar to plus (+) sign.Sat, 09 Nov 2019 20:30:00 +0100Thermal Buckling Analysis of Circular Bilayer Graphene Sheets Resting on an Elastic Matrix ...
http://jacm.scu.ac.ir/article_14896_0.html
In this article, the thermal buckling behavior of orthotropic circular bilayer graphene sheets embedded in the Winkler–Pasternak elastic medium is scrutinized. Using the nonlocal elasticity theory, the bilayer graphene sheets are modeled as a nonlocal double–layered plate that contains small scale effects and van der Waals (vdW) interaction forces. The vdW interaction forces between the layers are simulated as a set of linear springs using the Lennard–Jones potential model. Using the principle of virtual work, the set of equilibrium equations are obtained based on the first-order shear deformation theory (FSDT) and nonlocal differential constitutive relation of Eringen. Differential quadrature method (DQM) is employed to solve the governing equations for simply-supported and clamped boundary conditions. Finally, the effects of the small scale parameter, vdW forces, aspect ratio, elastic foundation, and boundary conditions are considered in detail.Mon, 11 Nov 2019 20:30:00 +0100Finite Element Analysis of Functionally Graded Skew Plates in Thermal Environment based on the ...
http://jacm.scu.ac.ir/article_14898_0.html
Functionally graded materials are commonly used in thermal environment to change the properties of constituent materials. The new numerical procedure of functionally graded skew plates in thermal environment is presented in this study based on the C0-form of the novel third-order shear deformation theory. Without the shear correction factor, this theory is also taking the desirable properties and advantages of the third-order shear deformation theory. We assume that the uniform distribution of temperature is embedded across the thickness of this structure. Both the rule of mixture and the micromechanics approaches are considered to describe the variation of material compositions across the thickness. Numerical solutions and comparison with other available solutions suggest that this procedure based on novel third-order shear deformation theory is accuracy and efficiency.Wed, 13 Nov 2019 20:30:00 +0100Spectral Quasi-linearization for MHD Nanofluid Stagnation Boundary Layer Flow due to a ...
http://jacm.scu.ac.ir/article_14899_0.html
This article concentrates on the effect of MHD heat mass transfer on the stagnation point nanofluid flow over a stretching or shrinking sheet with homogeneous-heterogeneous reactions. The flow analysis is disclosed in the neighborhood of stagnation point. Features of heat transport are characterized with Newtonian heating. The homogeneous-heterogeneous chemical reaction between the fluid and diffusing species is included in the mass diffusion equation. The MHD stagnation boundary layer flow is explored in the presence of heat generation/absorption. Numerical convergent solutions are computed via the spectral quasi-linearization method (SQLM). The physical aspects of different parameters are discussed through graphs. Thu, 14 Nov 2019 20:30:00 +0100Evaluating the Delamination in the Drilling Process of a Melamine Coated Medium Density ...
http://jacm.scu.ac.ir/article_14900_0.html
Medium density fiberboard (MDF) is an engineering product that is used in many industrial and general applications such as the furniture industry and kitchen cabinets. Generally, MDF products are generated by screw joints using the drilling process. However, the drilling process of the MDF panels leads to the delamination at the entrance and exit of the drill bit that should be controlled. In this work, the effect of the processing parameters including the feed rate and cutting speed on the delamination of melamine coated MDF is investigated. For this, two different tools with different tool geometry (a brad point drill bit and a commonly used twist drill bit) are examined. Image processing is used to measure the conventional delamination factor together with a new delamination factor referred to as area delamination factor for the drilled holes. It that the delamination value decreases with increasing cutting speed and increases with increasing feed rate. Though, there were some fluctuations in the results. The trend of changing the delamination respect to the investigated parameters was the same for both applied drill bits; however, the smaller value of delamination is obtained using the twist drill bit. Using the proposed area delamination factor, the effect of process parameters on the delamination is presented with higher magnitudes but with the same behavior. This, together with the ability of characterization of the water absorption of drilled holes has made the area delamination factor a more appropriate parameter to evaluate the delamination. The overall results are consistent with previously published works.Thu, 14 Nov 2019 20:30:00 +0100Effects of Inclined Magnetic Field and Porous Medium on Peristaltic Flow of a Bingham Fluid ...
http://jacm.scu.ac.ir/article_15007_0.html
The current paper aims to explain the peristaltic mechanism of a Bingham fluid with varying viscosity. The fluid is considered to flow within a porous medium and subjected to a magnetic field with significant inclination. Heat transfer characteristics are studied with convective conditions and variable thermal conductivity. The solution is obtained by the perturbation technique, where small values of variable liquid properties are utilized. The graphs plotted indicate that variation in viscosity as well as thermal conductivity actively contribute to reduce the pressure gradient. Further, for a higher radius of the plug flow region, a higher pressure rise occurs. The magnetic parameter and Grashof number influence the trapping phenomenon by reducing the dimensions of the bolus.Mon, 25 Nov 2019 20:30:00 +0100Numerical Analysis of an Edge Crack Isotropic Plate with Void/Inclusions under Different ...
http://jacm.scu.ac.ir/article_15010_0.html
In the present work, the effect of various discontinuities like voids, soft inclusions and hard inclusions of the mixed-mode stress intensity factor (MMSIF), crack growth and energy release rate (ERR) of an edge crack isotropic plate under different loading like tensile, shear, combine and exponential by various numerical examples is investigated. The basic formulation is based on the extended finite element method (XFEM) through the M interaction approach using the level set method. The effect of single and multi voids and inclusions with position variation on MMSIF and crack growth are also investigated. The presented results would be applicable to enhancing the better fracture resistance of cracked structures and various loading conditions.Tue, 26 Nov 2019 20:30:00 +0100Numerical Solution of the Time Fractional Reaction-advection-diffusion Equation in Porous Media
http://jacm.scu.ac.ir/article_15019_0.html
In this work, we obtained the numerical solution for the system of nonlinear time-fractional order advection-reaction-diffusion equation using the homotopy perturbation method using Laplace transform method with fractional order derivatives in Liouville-Caputo sense. The solution obtained is very useful and significant to analyze many physical phenomenons. The present technique demonstrates the coupling of homotopy perturbation method and the Laplace transform technique using He’s polynomials, which can be applied to numerous coupled systems of nonlinear fractional models to find the approximate numerical solutions. The salient features of the present work is the graphical presentations of the numerical solution of the concerned nonlinear coupled equation for several particular cases and showcasing the effect of reaction terms on the nature of solute concentration of the considered mathematical model for different particular cases. To validate the reliability, efficiency and accuracy of the proposed efficient scheme, a comparison of numerical solutions and exact solution are reported for Burgers’ coupled equations and other particular cases of concerned nonlinear coupled systems. Here we find high consistency and compatibility between exact and numerical solution to a high accuracy. Presentation of absolute errors for given examples are reported in tabulated and graphical forms that ensure the convergence rate of the numerical scheme.Tue, 26 Nov 2019 20:30:00 +0100Optimum Design of Nano-Scaled Beam Using the Social Spider Optimization (SSO) Algorithm
http://jacm.scu.ac.ir/article_15044_0.html
In this research study, the optimum cross-sectional dimensions of nano-scale beam elements are investigated under different load conditions. Euler-Bernoulli beam model based on nonlocal elasticity theory is utilized for the analysis of the beam. Two types of nano-scaled beams are modeled; carbon nanotubes (CNTs) and Boron nitride nanotubes (BNNTs). The novel meta-heuristic based optimization algorithm called Social Spider Optimization (SSO) algorithm is employed to find the beam designs with the objective of minimizing the cross-sectional area. Furthermore, the obtained optimum cross-sectional dimensions, critical stress and displacement values of the beams are compared according to the material type, beam length, and load conditions.Fri, 29 Nov 2019 20:30:00 +0100Distributed-parameter Dynamic Modeling and Bifurcation Analysis of a Trapezoidal ...
http://jacm.scu.ac.ir/article_15085_0.html
In this paper, the effect of the bimorph profile on the nonlinear dynamic behavior and performance of a vibratory piezomagnetoelastic energy harvester is investigated. The proposed model is composed of upper and lower piezoelectric layers on a trapezoidal cantilever beam with one attached tip magnet as well as two external magnets. The magnetic field of two external magnets generates magnetic forces and moment on the tip magnet. The bimorph structure is considered as a distributed-parameter system, and the external forces are obtained by analyzing the magnetic field of the external magnets. Equations of motion are obtained using electromagnetic Lagrange equations based on the generalized Hamilton principle and the Euler-Bernoulli beam theory. The proposed model for the bimorph and magnetic forces is validated by previously published experimental results. In order to compare the nonlinear behavior of the rectangular and trapezoidal beam profiles, the bifurcation diagrams are depicted for various control parameters such as the separation distances of the magnets, beam root width, and beam tip width. Verification of the bifurcation diagrams is performed by the phase plane portraits and Poincare maps. Also, the harvested power level is compared for different profiles of the bimorph. Moreover, the simultaneous effects of exciting frequency and bifurcation parameters on the system performance are investigated by the waterfall diagrams. The obtained results show that the trapezoidal beam profile with a lower tip width has higher performance than the rectangular beam. In trapezoidal beam profiles, the subharmonic and chaotic motions have relatively higher output powers than periodic motions.Thu, 05 Dec 2019 20:30:00 +0100Analysis of Entropy Generation in Hydromagnetic Micropolar Fluid Flow over an Inclined ...
http://jacm.scu.ac.ir/article_15138_0.html
A numerical analysis is performed on entropy generation in a radiative and dissipative hydromagnetic micropolar fluid prompted by a nonlinearly stretching sheet with the impact of non-uniform heat source/sink, variable magnetic field, electrical conductivity, and dynamic viscosity. The main equations are computationally solved via shooting techniques in the company with Runge-Kutta algorithms. The impact of the prominent controlling parameters is graphically checked on the velocity, temperature, microrotation, entropy generation, and Bejan number. An excellent relationship exists between the results obtained with related studies previously reported in the literature in the limiting conditions. More so, it is revealed by the findings that the irreversibility due to heat transfer is dominant over viscous dissipation irreversibility as the radiation parameter advances while the trend changes with the Brikman number parameter.Mon, 09 Dec 2019 20:30:00 +0100Nonlinear Convective Flow of Maxwell Fluid over a Slendering Stretching Sheet with Heat Source/Sink
http://jacm.scu.ac.ir/article_15143_0.html
In this study, the features of Maxwell fluid flow through a stretching sheet (variable thickness) with heat source/sink and melting heat transfer are analyzed. Leading equations of the course are transmuted with suitable similarity transmutations and resolved the subsequent equations mathematically with shooting technique. The effects of the valid parameters on the regular profiles (velocity, concentration, temperature) are elucidated through graphs in two cases (presence and absence of melting). And also, friction factor, transfer rates (mass, heat) are examined with the same parameters and the outcomes are presented in tabular form. A few of the findings are (a) the elastic parameter upsurges the velocity (b) heat source parameter raises the temperature (c) mass transfer rate is lowered by chemical reaction.Thu, 12 Dec 2019 20:30:00 +0100Poiseuille Flow with Couple Stresses Effect and No-slip Boundary Conditions
http://jacm.scu.ac.ir/article_15238_0.html
In this paper, the problem of Poiseuille flow with couple stresses effect in a fluid layer using the linear instability and nonlinear stability theories is analyzed. Also, the nonlinear stability eigenvalue problems for x,z and y,z disturbances are derived. The Chebyshev collocation method is adopted to arrive at the eigenvalue equation, which is then solved numerically, where the equivalent of the Orr-Sommerfeld eigenvalue problem is solved using the Chebyshev collocation method. The difficulties which arise in computing the spectrum of the Orr-Sommerfeld equation are discussed. The critical Reynolds number Rc, the critical wave number ac, and the critical wave speed cc are computed for wide ranges of the couple stresses coefficient M. It is found that the couple stresses coefficient M has great stabilizing effects on the fluid flow where the fluid flow becomes more unstable as M increases.Tue, 24 Dec 2019 20:30:00 +0100Investigation of Rousselier Model and Gurson-Tvergaard-Needleman Model in Ductile Fracture of ...
http://jacm.scu.ac.ir/article_15239_0.html
In this research, the micromechanical Rousselier damage model, which is not available in commercial software is accomplished with a subroutine in Abaqus finite element analysis software. Ductile fracture behavior of API X65 steel is evaluated by simulation of tensile test of smooth and round notch bar specimens of base metal in hoop direction and weld metal. The Rousselier model and its parameters of this model are determined for API X65 steel based on experimental data. In this work, the Rousselier and Gurson damage model is compared for API X65 steel. Results of the tensile test and simulation for the Gurson model show inaccuracy in the final stage of the load-displacement plot. This is because in the Gurson model it is assumed that the fracture surface is flat and shear fracture does not occur in specimens, but in the Rousselier model, the shear fracture is considered. The Rousselier model shows more accurate results compared with experimental data in the final stage of loading. Furthermore, the Rousselier model shows little error comparing with the experiment around maximum load since the void growth due to nucleation is ignored in this model. Also, the Rousselier model shows better convergence when the grooving radius of tensile test specimen increasing but the Gurson model behaves differently.Tue, 24 Dec 2019 20:30:00 +0100Miscellaneous Modeling Approaches and Testing of a Satellite Honeycomb Sandwich Plate
http://jacm.scu.ac.ir/article_15240_0.html
The honeycomb sandwich structures are commonly and efficiently adopted in the development of light mass satellite structures as a result of their inherent high stiffness and strength properties. Through a comprehensive study, the equivalent finite element modeling of honeycomb sandwich structures utilizing miscellaneous modeling approaches is introduced. For the sake of validating results, both theoretical analysis and experimental modal testing are implemented upon a honeycomb sandwich plate utilizing free-free boundary conditions. Based on the results, the sandwich theory and its related shell-volume-shell approach introduce a good match with the experimental results. The aforementioned approach is utilized extensively during the process of satellite structural design and modeling. In addition, a parametric study is executed so as to relate the geometric and material variations to the resonant modal frequencies. The study results indicate a crucial influence of both honeycomb core and facing sheets thicknesses on the modal frequency values.Wed, 25 Dec 2019 20:30:00 +0100Polymeric Dissipative Convection Flow from an Inclined Plane with Chemical Reaction: Numerical Study
http://jacm.scu.ac.ir/article_15241_0.html
An analytical model is developed to study the effects of viscous dissipation and chemical reaction in viscoelastic convection from an inclined plate as a simulation of electro-conductive polymer materials processing. The Jeffery’s viscoelastic model is deployed to describe the non-Newtonian characteristics of the fluid and provides a good approximation for polymers, which constitutes a novelty of the present work. The normalized nonlinear boundary value problem is solved computationally with the Keller-Box implicit finite-difference technique. Extensive solutions for velocity, surface temperature and concentration, skin friction, heat, and transfer rates are visualized numerically and graphically for various thermophysical parameters. Validation is conducted with earlier published work for the case of a vertical plate in the absence of viscous dissipation, chemical reaction, and non-Newtonian effects. The boundary layer flow is accelerated with increasing Deborah number whereas temperatures and concentrations are decelerated slightly. Temperatures and concentration are boosted with increasing inclination parameter whereas velocity is lowered. A reverse trend is seen for increasing Richardson number. Increasing chemical reaction reduces velocity and concentration whereas it enhances temperature. Increasing the viscous dissipation parameter is found to enhance velocity and temperature whereas it suppresses concentration.Wed, 25 Dec 2019 20:30:00 +0100Numerical Study on Subsurface Stress in Hertzian Contacts under Pure Sliding Conditions
http://jacm.scu.ac.ir/article_15243_0.html
In this study, the two-dimensional numerical simulation on the subsurface stress field in Hertzian contact under the pure sliding condition for different speeds and coefficients of friction is presented. The Hertzian contacts are represented by a dry contact between a rigid flat surface and an elastic cylinder with radius R=12.5 mm. Simulation is carried out through two steps, the first one is for applying normal load and the second one is for applying angular speed for the cylinder. The results of subsurface stress filed for pure sliding are compared to non-moving Hertzian contact. The results show that pure sliding speed has a major effect on the value of maximum von Mises stress in the subsurface of contact. The effect of sliding speed is attributed to tangential forces and elastic deformation in the contact. On the other hand, the coefficient of friction has a primary effect on the position of maximum stress and the shift of the contact region. Indeed, when pure sliding motion is introduced with a low value of friction coefficient, the shift of the contact region is negligible compared to non-moving Hertzian contact. The study is extended to investigate the effect of contact geometry on subsurface stress for Hertzian contact in the cam-follower interface. The shape of the follower has a significant effect on the value and distribution of Hertzian stress, thus, the fatigue life of rubbing surfaces of the cam-follower interface.Sat, 28 Dec 2019 20:30:00 +0100Reduction in Space for Dynamic Finite Element Analysis of Assemblies of Beam-columns when the ...
http://jacm.scu.ac.ir/article_15244_0.html
In 2008, a technique was proposed to reduce run-times in analysis of semi-discretized equation of motion against dynamic excitations available in digitized format. Later, the technique was successfully adapted to reduce numbers of degrees of freedom in finite element analysis of assemblies of beam-columns subjected to static digitized loads. In this paper, attention is paid to dynamic finite element analysis of assemblies of beam-columns. It is shown that, when the mass is available in digitized format, after small modifications in the original technique, the adaptation can simplify the analysis, regardless of the models' sizes, their linearity or non-linearity, and whether the damping is classical or non-classical. The reductions in run-time and in-core memory are considerable, while the changes in accuracy can be negligible.Sat, 28 Dec 2019 20:30:00 +0100Entropy Analysis of a Radiating Magnetic Liquid Film along a Slippery Inclined Heated Surface ...
http://jacm.scu.ac.ir/article_15252_0.html
The hydromagnetic flow of a Newtonian incompressible and electrically conducting variable-viscosity liquid film along an inclined isothermal or isoflux hydrophobic surface is investigated numerically. It is assumed that the fluid is subjected to a convective cooling at the free surface in the presence of a transversely imposed magnetic field. We incorporated in the energy equation, the viscous dissipation, Joule heating due to the magnetic field and the local radiative heat flux term for optically thick gray fluid reported by Roseland approximation. The governing non-linear differential equations are obtained and solved numerically using the shooting method coupled with a fourth-order Runge-Kutta method. The effects of some parameters on velocity and temperature profiles, skin friction, Nusselt number entropy generation rate, and the Bejan number profiles are analyzed graphically and discussed.Mon, 30 Dec 2019 20:30:00 +0100A Hybrid SVM-RVM Algorithm to Mechanical Properties in the Friction Stir Welding Process
http://jacm.scu.ac.ir/article_15253_0.html
The friction stir welding method is one of the solid-state welding methods for non-homogeneous metals. In this study, the 5XXX series aluminum sample and pure copper are subjected to four passes friction welding process and then the mechanical and metallurgical properties of the welded samples are compared with the prototype. For this purpose, the effect of welding parameters including rotational speed, forward speed and pin angle of the tool is tested by the full factorial method. In this process, hardness estimation and tensile testing are based on input process parameters in order to obtain mechanical properties is an important issue. For this purpose, a mathematical model of mechanical properties must be defined based on the input process parameters. Due to the complex nature of the effect of input process parameters on mechanical properties, this modeling is a complex mathematical problem in which the use of supervised learning algorithms is considered as an efficient alternative. In this paper, a new combination of Relevance Vector Machine (RVM) and Support Vector Machine (SVM) is presented which has a higher degree of accuracy.Mon, 30 Dec 2019 20:30:00 +0100Numerical Simulations of Unsteady 3D MHD Micropolar Fluid Flow over a Slendering Sheet
http://jacm.scu.ac.ir/article_15260_0.html
The purpose of the present analysis is to explore the numerical investigation on the time-dependent 3D magnetohydrodynamic flow of micropolar fluid over a slendering stretchable sheet. The prevailing PDEs are rehabilitated into coupled non-linear ODEs with the aid of appropriate similarity variables and then numerically calculated by applying the 4th RKM incorporate with shooting scheme. The contributions of various interesting variables are shown graphically. Emerging physical parameters on velocity, microrotation, and the surface drag coefficient are portrayed graphically. It is noticed that the microrotation profiles highly influenced by the vortex viscosity parameter and the micro-inertia density parameter. It is also concluded that the microrotation profiles (h2) are promoted by increasing the spin gradient viscosity parameter. Excellent accuracy of the present results is observed with the formerly published as a result of a special case.Wed, 08 Jan 2020 20:30:00 +0100Heating Capacity of an Earth to Air Heat Exchanger in Arid Regions - Experimental Investigation
http://jacm.scu.ac.ir/article_15262_0.html
Heating capacity of an earth to air heat exchanger EAHE equipped with an exterior fan in the arid region like the Southwest of Algeria is investigated experimentally. In-situ measurement of annual undisturbed subsoil vertical temperature profile is shown that it was 28°C at a depth of 1.5 meters. The EAHE made of 66 meters of PVC tube is demonstrated a heating capacity of 13°C and a cooling capacity of 7°C and a big dependence on local climate conditions. Great potentials and thermal comfort with less energy consumption are represented by earth to air or air-ground heat exchanger in the arid regions like the South of Algeria.Sat, 11 Jan 2020 20:30:00 +0100The Method of Lines Analysis of Heat Transfer of Ostwald-de Waele Fluid Generated by a ...
http://jacm.scu.ac.ir/article_15263_0.html
In this article, it is aimed to address one of Ostwald-de Waele fluid problems that either, has not been addressed or very little focused on. Considering the impacts of heat involving in the Non-Newtonian flow, a variant thickness of the disk is additionally considered which is governed by the relation z = a (r/RO+1)-m. The rotating Non-Newtonian flow dynamics are represented by the system of highly nonlinear coupled partial differential equations. To seek a formidable solution of this nonlinear phenomenon, the application of the method of lines using von Kármán’s transformation is implemented to reduce the given PDEs into a system of nonlinear coupled ordinary differential equations. A numerical solution is considered as the ultimate option, for such nonlinear flow problems, both closed-form solution and an analytical solution are hard to come by. The method of lines scheme is preferred to obtain the desired solution which is found to be more reliable and in accordance with the required physical expectation. Eventually, some new marvels are found. Results indicate that, unlike the flat rotating disk, the local radial skin friction coefficients and tangential decrease with the fluid physical power-law exponent increases, the peak in the radial velocity rises which is significantly distinct from the results of a power-law fluid over a flat rotating disk. The local radial skin friction coefficient increases as the disk thickness index increases, while local tangential skin friction coefficient decreases, the local Nusselt number decrease, both the thickness of the velocity and temperature boundary layer increase. Sun, 12 Jan 2020 20:30:00 +0100Size-dependent Nonlinear Forced Vibration Analysis of Viscoelastic/Piezoelectric Nano-beam
http://jacm.scu.ac.ir/article_15269_0.html
In this paper, the nonlinear forced vibration of isotropic viscoelastic/ piezoelectric Euler-Bernoulli nano-beam is investigated. For this purpose, the consistent couple stress theory is utilized for modeling the viscoelastic/piezoelectric nano-beam. Hamilton’s principle is also employed to obtain the governing equations of motion. Further, the Galerkin method is used in order to convert the governing partial differential equations to a nonlinear second-order ordinary differential one, and then multiple scale method is used to solve motion equation.Mon, 13 Jan 2020 20:30:00 +0100Magnetohydrodynamic Bio-convective Casson Nanofluid Flow: A Numerical Simulation by Paired ...
http://jacm.scu.ac.ir/article_15273_0.html
A study on the effects of gyrotactic microorganism and nanoparticles in the bio-convection magnetohydrodynamic flow of Casson fluid at the nonlinear stretching boundary is investigated. Irregular heat source/sink, Joule and viscous dissipations, Brownian motion, and thermophoresis are included in the energy equation. The model outlining the flow system is non-dimensionalised and retained in the same form. The equations are worked out by pairing, i.e. first pair momentum and gyrotactic micro-organism density equation and second pair energy and nanoparticle concentration equation. This technique is termed as a paired quasilinearisation method (PQLM). Convergence and accuracy of PQLM are shown. Obtained numerical results are depicted in graphs in order to observe further insight into the flow pattern. Interesting aspects of various controlling parameters in flow, heat, nanoparticle concentration and microorganism density are discussed.Tue, 14 Jan 2020 20:30:00 +0100Investigation of Jeffery-Hamel Flow for Nanofluid in the Presence of Magnetic Field by a New ...
http://jacm.scu.ac.ir/article_15275_0.html
In this article, numerical study of nanofluid flow between two inclined planes is carried out under the influence of magnetic field. Water-based nanofluid with nanoparticle of Copper (Cu) is taken into consideration for the present investigation. An efficient numerical method namely Optimal Homotopy Analysis Method (OHAM) is employed to get an approximate series solution for the related governing differential equation. A new approach is proposed to determine the convergence controller parameters used in OHAM. For the validation of the proposed technique, the convergence of the obtained results is shown for different values of involved parameters. Moreover, residual errors for the different number of terms in the obtained series solution are represented graphically. Obtained numerical results from the proposed method are incorporated with the previous results and they are found to be in very good agreement. Impacts of involved parameters like nanoparticle volume fraction, Hartmann number and Reynolds number on non-dimensional velocity are also discussed.Tue, 14 Jan 2020 20:30:00 +0100Design, Analysis, and Manufacturing of a Bone Cutting Ultrasonic Horn-Tool and Verification ...
http://jacm.scu.ac.ir/article_15307_0.html
Horn is one of the main components of ultrasonic cutting systems. The most important characteristics of the horn design are its resonant frequency and amplification factor. Closed-form equations can be used only for the design of simple horns and do not apply to more complex shapes like surgical tools. This paper presents a designing technique based on the finite element method and experimental tests. It can improve conventional design methods and facilitate designing a high performance surgical ultrasonic horn for bone cutting tools. The new and complex bone cutting tool has both the knife-edge and toothed-edge which could cut the bone easily and accurately. The investigations of cutting forces applied to the tool edges show less force in the toothed edge than the knife edge.Sat, 01 Feb 2020 20:30:00 +0100Third grade fluid flow of stretching cylinder with heat source/sink
http://jacm.scu.ac.ir/article_15316_0.html
This research investigated the impact of heat transfer on mixed convection steady third grade fluid flow over an impermeable stretching cylinder with heat source. The investigation of mixed convection with non-Newtonian fluid is significant in geophysical and engineering fields. Appropriate transformations are alleged to obtain ordinary differential equations, which are later computed by using an analytical approach called the homotopy analysis methodology (HAM) and the interval of convergence is computed. Local Nusselt number and coefficient of skin friction values are computed numerically for novel parameters.Mon, 03 Feb 2020 20:30:00 +0100Numerical solution of time fractional cable equation via the Sinc-Bernoulli collocation method
http://jacm.scu.ac.ir/article_15318_0.html
An important equation usually used in modeling neuronal dynamics isthe cable equation. In this work, a numerical method for the fractionalcable equation which involves two Riemann-Liouville fractionalderivatives is proposed. Our computational technique is based ona collocation idea where a combination of Bernoulli polynomialsand Sinc functions are used to approximate the solution to this problem. The constructed approximation by our method convert the fractional cable equation into a set of algebraic equations. Also, we provide two numerical examples to confirm the accuracy and effectiveness of the present method.Fri, 07 Feb 2020 20:30:00 +0100Fractional Sumudu decomposition method for solving PDEs of fractional order
http://jacm.scu.ac.ir/article_15348_0.html
In this paper, the fractional Sumudu decomposition method (FSDM) is employed to handle the time-fractional PDEs and system of time-fractional PDEs. The fractional derivative is described in the Caputo sense. The approximate solutions are obtained by using FSDM, which is the coupling method of fractional decomposition method and Sumudu transform. The method in general is easy to implement and yields good results. Illustrative examples are included to demonstrate the validity and applicability of the proposed technique.Mon, 17 Feb 2020 20:30:00 +0100Structural Strength Analysis and Fabrication of a Straight Blade for a H-Darrieus Wind Turbine
http://jacm.scu.ac.ir/article_15352_0.html
Small H-Darrieus wind turbines have become popular in the wind power market because of their many advantages, which include simplicity of design, low construction costs and they are thought to represent an adequate solution even in unconventional installation regions. The blade is generally considered as the most important component of the wind turbine system because it controls the efficiency of the turbine. The blade structure must be designed to support the difficult environmental conditions (e.g., wind, and snow) encountered during the operational life of the wind turbine. This current study uses three-dimensional (3D) modelling and structural strength analysis to fabricate two straight blades (aluminum and galvanized steel) for a small H-Darrieus wind turbine. The 3D modelling of the blade structure is performed using SolidWorks, a computer aided design (CAD) software package and the structural strength analysis uses finite element analysis (FEA) technique to identify the stiffness, resistance and reliability of the blade structure. The simulation results obtained indicate that no structural failures are predicted for either of the two structures tested because the factors of safety are larger than 1 and the all maximum deflections are within the allowable deformation limits for the materials. Manufacturing processes for the two structures are described.Wed, 19 Feb 2020 20:30:00 +0100Thermoelastic Model with Higher-order Time-derivatives and Two Phase-lags for an Infinitely ...
http://jacm.scu.ac.ir/article_15353_0.html
In this work, a generalized higher-order time-derivatives model with phase-lags has been introduced. This model is applied to study the thermal heat problem of a homogeneous and isotropic long cylinder due to initial stress and heat source. We use the Laplace transform method to solve the problem. The numerical solutions for the field functions are obtained numerically using the numerical Laplace inversion technique. The effect of the higher-order parameters, the initial stress, the magnitude of the heat source and the instant time on the temperature field, the displacement field, and the stress fields have been calculated and displayed graphically and the obtained results are discussed. The results are compared with those obtained previously in the contexts of some other models of thermoelasticity.Wed, 19 Feb 2020 20:30:00 +0100Investigation on the crack effect in the cylinder and matrix on the backscattering field ...
http://jacm.scu.ac.ir/article_15354_0.html
A novel method to determine the health of the industrial parts is using the ultrasound scattering waves. Any changes in the structure of the scattering object or in the boundary conditions will cause a change in the scattering field. The frequency spectrum of the scattering time signal has valuable information, which is studied by resonant ultrasound spectroscopy (RUS). Since any defect, property changes or changes in boundary conditions can affect on the scattering field,the possible defects in the piece can, therefore be detected by using the response of the scattering field.One possible defect in the fiber-reinforced composites is the existence of crack in the matrix or fibers. The present study investigated the effect of crack on the far field backscattering amplitude spectrum using the finite element method (FEM).To this end, the effect of the crack’s direction in the cylinder and matrix on the form function has been studied.The results show that the Rayleigh frequency modes are more sensitive to the cracks existing in the epoxy matrix than the Whispering-gallery frequency modes. Also,the existence of the crack in the aluminum cylinder has the most effect on the Whispering-gallery frequency modes. In addition, the existence of horizontal crack in the aluminum cylinder leads to a large reduction in these frequency modes.The validation of the research was determined by comparing the steel cylinder form function obtained from the finite element method’s information and the analytical and experimental form functions and also the comparison of the aluminum cylinder form function and reference form function.Wed, 19 Feb 2020 20:30:00 +0100Numerical calculation of an air centrifugal separator based on the SARC turbulence model
http://jacm.scu.ac.ir/article_15362_0.html
The numerical results of mathematical modeling of a two-phase swirling turbulent flow in the separation zone of a centrifugal apparatus are presented. The motion of the carrier gas flow was modeled using the averaged Navier - Stokes equations, for the closure of which the well-known turbulence model by Schur and Spalart was used, the amendment to the Spalart-Allmaras SARC model. Based on the obtained field of averaged velocities of the carrier medium, taking into account turbulent diffusion. The article compares the results taking into account the influence of the solid phase on the dynamics of the air environment and without taking it into account with experimental data.Sat, 29 Feb 2020 20:30:00 +0100Numerical Modeling of Heat Transfer and Hydrodynamics in Compact Shifted Arrangement Small ...
http://jacm.scu.ac.ir/article_15391_0.html
Numerical modeling of heat and hydrodynamics processes in the channels of compact small diameter tube bundles with different transverse shifted arrangement is carried out. The fields of velocities, temperatures and pressures in the tube bundle channels were obtained and their influence on heat transfer conditions and hydraulic losses were analyzed. The calculation of the thermohydraulic efficiency for different constructions of the tube bundles had been carried out and their results with data of well-known tube bundles of different geometry are compared.Sun, 01 Mar 2020 20:30:00 +0100Mathematical analysis of Poiseuille flow of Casson fluid past porous medium
http://jacm.scu.ac.ir/article_15394_0.html
This article investigates the influence of microstructure in the Casson fluid flow through porous medium, by extending the Buckingham-Reiner’s one dimensional model to plane-Poiseuille flow and Hagen-Poiseuille flow geometries. While analyzing the flow characteristics in single channel/pipes or multiple channels/pipes of different width/radius, four different probability density functions are used to model the pores widths/radii distributions. It is found that when the pressure gradient increases, the Buckingham-Reiner function raises slowly in the plane-Poiseuille flow, whereas in Hagen-Poiseuille flow, it rises rapidly. In all kinds of distribution of pores, the fluid’s mean velocity and porosity of the flow medium are considerably higher in the Hagen-Poiseuille flow than in the plane-Poiseuille flow and this behavior is reversed for the permeability of the flow medium. The fluid’s mean velocity, porosity and permeability of the flow medium increases appreciably with the rise of the channel width and pipe radius. The porosity of the flow medium slumps with the rise of the period of the channels and pipes distribution from 1 to 2 and it decreases very slowly with the further rise of the period H of the channels and pipes from 2 to 11.Mon, 02 Mar 2020 20:30:00 +0100Comparative Study of Mixed Convective MHD Cu-Water Nanofluid Flow over a Cone and Wedge using ...
http://jacm.scu.ac.ir/article_15395_0.html
The steady Cu-water nanofluid flow in presence of magnetic field is investigated numerically under the effects of mixed convection, thermal radiation and chemical reaction. For investigating the nanofluid flow, the flow over two different geometries, cone and wedge have been considered. The Tiwari and Das nanofluid model is implemented together with Buongiorno nanofluid model. Thermal and concentration diffusion are studied using the Cattaneo-Christov double diffusion model. At the boundary of the surface, no slip and zero mass flux condition are implemented to control the nanoparticle volume fraction at surface. Constitutive laws of flow are obtained in form of ordinary differential equations by the use of similarity transformation. The modeled flow problem is solved numerically by the Runge-Kutta-Fehlberg method and shooting scheme. Variation in flow properties due to parameters involved is presented graphically and through tabular values. The effect of thermal radiation and thermal relaxation parameter is to increase heat transfer. The temperature of nanofluid and drag force at surface increases due to enhanced magnetic field. The nanoparticles are found to be concentrated near the surface of cone and wedge but concentration decreases with chemical reaction parameter and Schmidt number as fluid moves towards far field.Mon, 02 Mar 2020 20:30:00 +0100Hybrid Solution for the Analysis of MHD Micropolar Fluid Flow in a Vertical Porous ...
http://jacm.scu.ac.ir/article_15397_0.html
In this paper, we analyze the transient magnetohydrodynamic (MHD) flow of an incompressible micropolar fluid between a porous parallel-plates channel. The fluid is electrically-conducting subjected to radiation described by the Cogley-Vincent-Gilles formulation and with convective thermal boundary conditions at the plates. The solution methodology employed is the hybrid numerical-analytical approach known as the Generalized Integral Transform Technique (GITT). The consistency of the integral transform method in handling such a class of problem is illustrated through convergence analyses, and the influence of physical parameters such as radiation, and micropolar parameters, and Hartman number. The wall shear stress, the coupled stress coefficient, and heat flux at the walls were also calculated, demonstrating that increasing the gyroviscosity decreases the wall stresses magnitudes. Furthermore, the results show that increasing the radiation heat transfer decreases the fluid temperature distribution. Additionally, the velocity is damped, and the angular velocity is increased by the Lorentz force in the presence of a magnetic field.Mon, 02 Mar 2020 20:30:00 +0100Thermal Performance of Oscillating Blade with Various Geometries in a Straight Channel
http://jacm.scu.ac.ir/article_15420_0.html
In this study, the effect of stationary and oscillating blades on the forced convection heat transfer in a channel are studied numerically. Simulations are performed in a fully-developed, laminar, unsteady, and incompressible flow with Reynolds number and Prandtl number equal to 100 and 1, respectively. The effects of blade geometry, oscillating speed and oscillation angle on heat transfer and pressure drop are studied. The results are presented in terms of time averaged Nusselt number, temperature and vorticity distribution and the pressure drop. The results indicate that the oscillation angle and oscillating speed of the blade and the number of the blades, affect the thermal performance of the channel. For most cases, it was observed that the effect of the oscillation angle is more than that for the oscillating speed on heat transfer enhancement. However, increasing the number of blades does not necessarily help to enhance the heat transfer, but it can slightly decrease the pressure drop.Mon, 09 Mar 2020 20:30:00 +0100Buckling and vibration analysis of a double-layer Graphene sheet coupled with a piezoelectric ...
http://jacm.scu.ac.ir/article_15421_0.html
In this article, the vibration and buckling of a double-layer Graphene sheet (DLGS) coupled with a piezoelectric nanoplate through an elastic medium (Pasternak and Winkler models) are under consideration. DLGS are subjected to biaxial in-plane forces and van der Waals force existing between each layer. Polyvinylidene fluoride (PVDF) piezoelectric nanoplate is subjected to an external electric potential. For the sake of this study, sinusoidal shear deformation theory of orthotropic plate expanded with Eringen’s nonlocal theory is selected The results indicate that nondimensional frequency and nondimensional critical buckling load rise, when the ratio of width to thickness increases. Furthermore, incrementing the effect of elastic medium parameter results in increasing the stiffness of the system and, consequently, rising nondimensional frequency and critical buckling load.Mon, 09 Mar 2020 20:30:00 +0100Computational Fluid Dynamic Analysis of Amphibious Unmanned Aerial Vehicle
http://jacm.scu.ac.ir/article_15424_0.html
Unmanned Aerial Vehicles (UAVs) are becoming popular due to its versatile maneuvering and high pay load carrying capabilities. Military, navy and coastal guard makes crucial use of the amphibious UAVs which includes the working functionalities of both hover craft and multi-rotor systems. Inculcation of these two systems and make it as amphibious UAV for water quality monitoring, sampling and analysis is essential to serve the human-kind for providing clean water. On this note, an amphibious UAV is designed for carrying a water sampler mechanism with an on-board sensor unit. In order to examine the stability of designed UAV under diverse wind load conditions and to examine the aerodynamic performance characteristics, computational fluid dynamic analysis (CFD) is performed. For various flight conditions such as pitch, roll, yaw and hovering, the flow characteristics around the vehicle body is examined. The aerodynamic phenomenon at the rotor section, vortex, turbulent regions, wake and tip vortex are identified. In addition, CFD analysis are conducted to determine the thrust forces during forward and hovering conditions through varying the wind speed 3 to 10 m/sec and speed of rotor 2000 to 5000 rpm. The effect of non-dimensional parameters such as advance ratio and induced inflow ratio on estimating the thrust characteristics are studied. Simulation results suggested that at 5° angle of attack and 8 m/sec wind speed condition, the aerodynamic performance of the vehicle is superior and stable flight is guaranteed. The amphibious UAV with flying and gliding modes for collecting water samples in remote water bodies and also in-situ water quality measurement can be well utilized for water quality monitoring.Wed, 11 Mar 2020 20:30:00 +0100Validation of Model-Based Real-Time Hybrid Simulation for a Lightly-Damped and Highly-Nonlinear ...
http://jacm.scu.ac.ir/article_15427_0.html
Hybrid simulation (HS) is a cost-effective alternative to shake table testing for evaluating the seismic performance of structures. HS structures are partitioned into linked physical and numerical substructures, with actuators and sensors providing the means for the interaction. Load application in conventional HS is conducted at slow rates and is sufficient when material rate-effects are negligible. Real-time hybrid simulation (RTHS) is a variation of the HS method, where no time-scaling is applied. Despite the recent strides made in RTHS research, the body of literature validating the performance of RTHS, compared to shake table testing, remains limited. In the few available studies, the tested structures and assemblies are linear or modestly nonlinear, and artificial damping is added to the numerical substructure to ensure convergence and stable execution of the simulation. The objective of this study is the validation of a recently proposed model-based RTHS framework, focusing on lightly-damped and highly-nonlinear structural systems; such structures are particularly challenging to consider using RTHS. The boundary condition in the RTHS tests are enforced via displacement and acceleration tracking. The modified Model-Based Control (mMBC) compensator is employed for the tracking action. A two-story steel frame structure with a roof-level track nonlinear energy sink (NES) device is selected due to its light damping, high nonlinearity, and repeatability. The complete structure is first tested on a shaking table, and then substructured and tested via the RTHS method. The model-based RTHS approach is shown to perform similar to the shake table method, even for lightly-damped and highly-nonlinear structures.Sun, 15 Mar 2020 20:30:00 +0100Theoretical and Experimental Investigation on Mechanical Behavior of Aluminum to Aluminum ...
http://jacm.scu.ac.ir/article_15433_0.html
The combination of mechanical and bonded joints creates a new connection type, called hybrid joint which has the benefits of both mechanical and bonded joints. In this research, the mechanical behavior of the tubular bonded lap joint between aluminum tubes subjected to pure torsion has been investigated experimentally and numerically, and the results have been compared. The mechanical behavior of the hybrid (rivet/bonded) joint has been investigated numerically and the outcomes have been compared. The adhesive and rivets have cohesive elements and bushing connector elements, respectively. The results from the hybrid joints and the damage mechanism show that the rivets change the interface shear stress and the stress distribution of the joint, and affect the joint’s torque capacity and strengths. It has been observed that for specimens with overlap lengths close to effective length, the hybrid joint is more effective.Sun, 15 Mar 2020 20:30:00 +0100Nanostructure, Molecular Dynamics Simulation and Mechanical Performance of PCL Membranes ...
http://jacm.scu.ac.ir/article_15466_0.html
Recently, the application of porous bio-nanocomposites has been considered by many researchers for orthopedic application. Since experimental tests for obtaining the mechanical and physical properties of these nanostructured biomaterials are very expensive and time-consuming, it is highly recommended to model and simulate these bio-nanoscale materials to predict their mechanical and physical properties. In this study, three-phase porous bio-nanocomposite membranes were fabricated with Titanium oxide (TiO2), Hydroxyapatite (HA) and Polycaprolactone (PCL) polymer. HA and TiO2 are both biocompatible and biodegradable. The samples were fabricated with various amounts of titanium oxide and the materials characterization has been performed on selected sample. The molecular dynamics technique (MD) have been used to predict the mechanical performance of the nanocomposite models. The MD simulations were performed for single phase material and the developed for two phases equivalent components as a new approach in using MD simulation results. The results indicated the close relationship between the experimental data and simulation values for the selected sample. Moreover, phase and morphology of these nanostructures have been investigated using SEM results. Therefore, based on the proposed approach, MD simulation can be applicable for predicting the properties of porous bio-nanocomposite membrane.Thu, 26 Mar 2020 19:30:00 +0100A Note on the Hydromagnetic Blasius Flow with Variable Thermal Conductivity
http://jacm.scu.ac.ir/article_15467_0.html
: This paper unravels the influence of transverse magnetic field on the development of steady flow regime for an incompressible fluid in the boundary layer limit of a semi-infinite vertical plate. The sensitivity of real fluids to changes in temperature suggests a variable thermal conductivity modelling approach. Using appropriate similarity variables, solutions the governing nonlinear partial differential equations are obtained by numerical integration. The approach used here is based on using shooting method together with Runge-Kutta-Fehlberg integration scheme. Representative velocity and temperature profiles are presented at various values of the governing parameters. The skin-friction coefficient and the rate of heat transfer are also calculated for different parameter values. Pertinent results are displayed graphically and discussed. It is found that heat transfer rate improves with an upsurge in magnetic field but lessens with an elevation in the fluid thermal conductivity.Sun, 29 Mar 2020 19:30:00 +0100Explicit and Implicit Finite -Volume Methods for Depth Averaged Free-Surface Flows
http://jacm.scu.ac.ir/article_15468_0.html
In recent years, much progress has been made in solving free-surface flow variation problems in order to prevent flood environmental problems in natural rivers. Computational results and convergence acceleration of two different (explicit and implicit numerical techniques) finite-volume based numerical algorithms, for depth-averaged subcritical and/or supercritical, free-surface, steady flows in channels, are presented. The implicit computational model is a bi-diagonal, finite-volume numerical scheme, based on MacCormack’s predictor-corrector technique and uses the semi-linearization matrices for the governing Navier-Stokes equations which are expressed in terms of diagonalization. This implicit numerical scheme puts primary emphasis to solution convergence using non-orthogonal local coordinate system. The explicit formulation uses volume integrals to solve the governing flow equations. Computational results and convergence performance between the implicit and the explicit finite-volume numerical schemes, for incompressible, viscous, depth-averaged free-surface, steady flows are presented. Implicit and explicit computational results are satisfactorily compared with available measurements. The implicit bi-diagonal technique yields fast convergence compared to the explicit one at the expense of programming effort. Iterations require to achieve convergence solution error of less than 10-5, can be reduced down to 90.0 % in comparison to analogous flows with using explicit numerical technique.Sun, 29 Mar 2020 19:30:00 +0100Experimental and Finite Element Study to Determine the Mechanical Properties and Bond Between ...
http://jacm.scu.ac.ir/article_15470_0.html
The separation between repair mortars and the concrete substrate is one of the serious problems in repairing concrete structures. One of the main causes of this separation is the lack of proper curing and consequently excessive shrinkage of the repair mortar which reduces the bond strength between the concrete substrate and the repair layer and has a negative impact on the compressive and tensile strength of the repair mortars. This paper investigated the mechanical properties, shrinkage of repair mortars, as well as their shear and tensile bond strength on the concrete substrate of different ages under the curings of "abandoned in the laboratory space", "water-submerged" and "curing agent". In-situ "friction-transfer" and "pull-off" methods were used to measure adhesion. Furthermore, the relationships between compressive strength, tensile strength, and readings obtained from "friction-transfer" and "pull-off" methods on repair mortars and the stress distribution method used in the above-mentioned methods are presented using nonlinear finite element analysis (Abaqus/CAE). The results indicate a significant effect of curing method on shrinkage and mechanical properties of repair mortars; as a result, effective curing increases the shear and tensile bond strength at the substrate and repair layer joint boundary. It was also observed that there was a linear relationship between the experimental results obtained from the two methods used in this study with a high correlation coefficient, highly consistent with the results obtained from nonlinear finite element analysis. Thus, they can be used as in-situ methods for determining the compressive and tensile strength of repair mortars.Fri, 03 Apr 2020 19:30:00 +0100Unsteady Stokes Flow through a Porous Pipe with Periodic Suction and Injection with slip Conditions
http://jacm.scu.ac.ir/article_15478_0.html
The problem of unsteady Stokes flow of certain Newtonian fluids in a circular pipe of uniform cross section is discussed. The pipe is uniformly porous. The unsteady Navier-Stokes equations for the system in cylindrical polar coordinates have been solved analytically to obtain a complete description of the flow. The solution of the flow equations subject to the slip boundary conditions leads to the detailed expressions for axial and radial components of velocity and the pressure distribution depending on position coordinates and time. As a special case we have presented the situation when no-slip boundary conditions are implemented. The velocity profile is analyzed for different values of the flow parameters.Thu, 09 Apr 2020 19:30:00 +0100