Journal of Applied and Computational Mechanics
https://jacm.scu.ac.ir/
Journal of Applied and Computational Mechanicsendaily1Sat, 01 Jul 2023 00:00:00 +0330Sat, 01 Jul 2023 00:00:00 +0330Electrochemical and Mechanical Properties of Ni/g-C3N4 Nanocomposite Coatings with Enhanced Corrosion Protective Properties: A Case Study for Modeling the Corrosion Resistance by ANN and ANFIS Models
https://jacm.scu.ac.ir/article_17241.html
This work investigates the effect of electrolysis bath parameters on the corrosion, micro-hardness, and wear behavior of Ni coatings. The characterization of synthesized Graphitic carbon nitride (g-C3N4) was done by Fourier transform infrared, Raman spectroscopy, and transmission electron microscope. The surface morphology of coated samples with various amounts of current density was studied by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The corrosion prevention effect of Ni/g-C3N4 nanocomposite coatings was investigated by EIS and polarization techniques. The experimental outcome demonstrates that an electrolysis bath of 0.3 g/L g-C3N4 and 0.1 A.cm-2 presents a Ni coating with the highest corrosion protection, wear resistance, and microhardness. The corrosion current densities of Ni/g-C3N4 coatings obtained by electrochemical tests were used for training two machine learning techniques (Artificial neural network (ANN) and adaptive neuro-fuzzy inference system (ANFIS)) based on current density, g-C3N4 concentration, and plating time as an input. Various statistical criteria showed that the ANFIS model (R2= 0.99) could forecast corrosion current density more accurately than ANN with R2= 0.91. Finally, due to the robust performance of ANFIS in modeling the corrosion behavior of Ni/g-C3N4 nanocomposite coating, the effect of each parameter was studied.Temperature Effect on Moving Water Droplets at the Channel of PEMFC by Multi-component Multiphase Lattice Boltzmann Method
https://jacm.scu.ac.ir/article_17253.html
In this paper, a multi-component multiphase pseudopotential Lattice Boltzmann method with multi relaxation time (MRT) collision operator is presented to examine the dynamic behavior of liquid droplets movement and coalescence process in the gas channel of PEMFC. In the numerical method, the forcing term is improved to achieve a high-density ratio and thermodynamic consistency. First, the density ratio, Laplace law, and contact angle are validated with previous studies. Then, different parameters, such as operating temperature, pressure difference, surface contact angle, the radius of droplets, and distance between two droplets on the droplet movement and coalescence process are studied. The results revealed by rising temperature from 30 to 80 degrees, the speed of drop increases around 6 percent. The simulation results indicated that the rising of pressure gradient increases the gas flow velocity on the channel and leads to increasing the shear force and eventually faster movement of the droplet on the gas channel. Also, investigation of various contact angles shows that a hydrophilic surface causes a resistance force between the droplet and the wall and delays the removal of droplets. Moreover, droplet coalescence is useful for droplet movement because of increasing the velocity gradient on top of the droplet; consequently, the shear force on the droplet is raised during coalescence.Power Law Nanofluid through Tapered Artery based on a Consistent Couple Stress Theory
https://jacm.scu.ac.ir/article_17303.html
Based on couple stress theory, this study investigated non-Newtonian power-law nanofluid flows in converging, non-tapered, and diverging arteries. In addition to excluding gravity effects artery, geometry included mild stenosis. The momentum equation is solved via the Galerkin method, and the results are compared with experimental and classical findings. Although the power-law couple stress theory&rsquo;s relations are first used in the analysis of non-Newtonian blood flow, the results of this theory are far more consistent with experimental results than classical results. Comparison of the results of the study of blood flow velocity profiles in a non-tapered artery without stenosis by the mentioned theory with experimental and classical theory results shows the difference in velocity at the center of the artery between the experimental results and the results of the classical theory is 36%, while this value has been reduced to 14% for the results of the couple stress theory. The variations in velocity profile with the power-law index (n=0.8 and n=0.85) and the dimensionless Darcy number (Da=10-10 and Da=10-7) in all three geometries indicated a flat velocity distribution with the increase in the power-law index while increasing the velocity profile with increased Darcy number. Mass transfer and energy equations are solved using the extended Kantorovich method. The solution convergence is evaluated, and the influence of parameters such as Prandtl number, Schmidt number, and dimensionless thermospheric and Brownian parameters on concentration and temperature profiles is obtained.Stress-driven Approach to Vibrational Analysis of FGM Annular Nano-plate based on First-order Shear Deformation Plate Theory
https://jacm.scu.ac.ir/article_17712.html
Vibrational behavior of small-scale functionally graded annular plate based on the first-order shear deformation theory, and non-local stress-driven model is investigated. For the first time, generalized differential quadrature rule is utilized to solve the governing equation and related boundary conditions. The convergence, accuracy, and efficiency of the generalized differential quadrature rule are investigated using problem-solving for different situations. The effects of parameters such as size parameter, inhomogeneity coefficient of functionally graded materials, thickness to outer radius ratio, inner radius to outer radius ratio, and boundary conditions on the natural frequency of the structure have been investigated. Results show that, unlike the strain-driven model, the non-local stress-driven theory predicts the same behavior for all boundary conditions and increasing the size parameter has led to a stiffening behavior and an increase in the natural frequency of the structure.Time Distance: A Novel Collision Prediction and Path Planning Method
https://jacm.scu.ac.ir/article_17889.html
In this paper, a new fast algorithm for path planning and a collision prediction framework for two dimensional dynamically changing environments are introduced. The method is called Time Distance (TD) and benefits from the space-time space idea. First, the TD concept is defined as the time interval that must be spent in order for an object to reach another object or a location. Next, TD functions are derived as a function of location, velocity and geometry of objects. To construct the configuration-time space, TD functions in conjunction with another function named "Z-Infinity" are exploited. Finally, an explicit formula for creating the length optimal collision free path is presented. Length optimization in this formula is achieved using a function named "Route Function" which minimizes a cost function. Performance of the path planning algorithm is evaluated in simulations. Comparisons indicate that the algorithm is fast enough and capable to generate length optimal paths as the most effective methods do. Finally, as another usage of the TD functions, a collision prediction framework is presented. This framework consists of an explicit function which is a function of TD functions and calculates the TD of the vehicle with respect to all objects of the environment.2D Planar Simulation of Collisions between Liquid Droplets and Solid Particles in a Gas
https://jacm.scu.ac.ir/article_17907.html
Here we present a 2D planar simulation of the collisions between liquid droplets and solid particles that are most often used in industrial applications. The collisions are modeled using a combination of Volume of Fluid and Level Set methods. We study the impact of the particle-to-droplet size ratio and the shape of solid particles on the collision behavior and interaction regimes. The findings are presented in the form of collision regime maps. The interaction regimes are also distinguished for binary droplet collisions: deposition, separation, and disintegration. We show the impact of density, viscosity, and surface tension on the droplet collision regime maps as well as on the number of secondary fragments. The practical value of the research comes from the newly established differences of collision regimes between droplets and particles of different shapes and sizes.Even and Uneven Porosities on Rotating Functionally Graded Variable-thickness Annular Disks with Magneto-electro-thermo-mechanical Loadings
https://jacm.scu.ac.ir/article_17908.html
This paper investigates the porosity effect on rotating functionally graded piezoelectric (FGP) variable-thickness annular disk. Even and uneven porosity distributions for the disk are approximated. The porous annular disk is subjected to the influence of electromagnetic, thermal, and mechanical loadings. Material coefficients are graded and described as a power law in the radial direction of the annular rotating disk. The resulting differential equation with boundary conditions is solved using the semi-analytical technique. Two cases are studied for the porous annular disk, circular disk, and mounted disk. The effectiveness of the porosity factor and grading index on the temperature, stresses, and displacement are reported. Comparisons between non-porous and porous annular disks for even and uneven porosity are executed and discussed. The obtained results are presented to conclude the important role of porosity on the rotating variable-thickness annular disk for the purpose of engineering mechanical design.Local Thermal Non-equilibrium Analysis of Cu-Al2O3 Hybrid Nanofluid Natural Convection in a Partially Layered Porous Enclosure with Wavy Walls
https://jacm.scu.ac.ir/article_17926.html
A numerical study is performed to investigate the local thermal non-equilibrium effects on the natural convection in a two-dimensional enclosure with horizontal wavy walls, layered by a porous medium, saturated by Cu-Al2O3/water hybrid nanofluid. It is examined the influence of the nanoparticle volume fraction, varied from 0 to 0.04, the Darcy number (10-5 &le; Da &le; 10-2), the modified conductivity ratio (0.1 &le; &upsih; &le; 1000), the porous layer height (0 &le; Hp &le; 1), and the wavy wall wavenumber (1 &le; N &le; 5) on natural convection in the enclosure. Predictions of the steady incompressible flow and temperature fields are obtained by the Galerkin finite element method, using the Darcy-Brinkman model in the porous layer. These are validated against previous numerical and experimental studies. By resolving separately the temperature fields of the working fluid and of the porous matrix, the local thermal non-equilibrium model exposed hot and cold spot formation and mitigation mechanisms on the heated and cooled walls. By determining the convection cell strength, the Darcy number is the first rank controlling parameter on the heat transfer performance, followed by N, Hp and &gamma;. The heat transfer rate through the hybrid nanofluid and solid phases is highest when N = 4 at a fixed value of nanoparticle volume fraction.Impact Dynamics of Nonlinear Materials: FE Analysis
https://jacm.scu.ac.ir/article_17928.html
The paper presents an experimentally validated 3D finite element modelling impacts of viscoelastic and natural materials. It considers, in particular, the material set of ash wood and rubber in the context of the impact between the bat (the &ldquo;hurley&rdquo; made of ash wood) and the ball (the &ldquo;sliotar&rdquo; made of polyurethane-cork composite) in the Irish game of hurling. The hurley is highly anisotropic in its mechanical properties and this impact system therefore presents a unique modelling challenge. The FE models do not rely on either the assumption of linear materials models or on calibrated materials models. The FE models are able to take all three geometric, status and material nonlinearities into account yielding a close correlation with real-world impact scenario. The reported FE results were validated against experimental measurements showing an excellent correlation of more than 91% in term of maximum ball deformation.Prediction of the Supersonic Flow Base Pressure by Axisymmetric Direct Numerical Simulation
https://jacm.scu.ac.ir/article_17929.html
Axisymmetric direct numerical simulation (DNS) has been carried out to predict supersonic base flow behavior. Substantially fine grid has been used to perform calculations for the flow with Reynolds number up to 106. Optimal grid resolution was established through test calculations for affordable run time and solution convergence determined by the vorticity value. Numerical scheme provides fourth-order approximation for dissipative, fifth-order for convective and second-order for unsteady terms of conservation equations. Reynolds Averaged Navier-Stokes (RANS) approach has been employed to obtain input flow profiles for DNS calculations. Series of calculations have been carried out for Mach number 1.5 with Reynolds numbers 104, 105, 106 and for Mach number 2.46 with Reynolds number 1.65&times;106. It has been found that local base pressure coefficient calculated by DNS is a bit overestimated in a zone close to symmetry axis in comparison with experiment while integrated base drag coefficient shows good agreement with experimental data and noticeably better than one obtained by RANS approach.A Bridge Vibration Measurement Method by UAVs based on CNNs and Bayesian Optimization
https://jacm.scu.ac.ir/article_17936.html
A bridge vibration measurement method by Unmanned Aerial Vehicles (UAVs) based on a Convolutional Neural Network (CNN) and Bayesian Optimization (BO) is proposed. In the proposed method, the video of the bridge structure is collected by a UAV, then the reference points in the background of the bridge and the target points on the bridge in the video are tracked by the Kanade-Lucas-Tomasi (KLT) optical flow method, so that their coordinates can be obtained. The BO is used to find the optimal hyper-parameter combination of a CNN, and the CNN based on BO is used to correct the bridge displacement signal collected by the UAV. Finally, the natural frequency of the bridge is extracted by processing the corrected displacement signals with Operational Modal Analysis (OMA). Moreover, a steel truss is used as the experimental model. The number of reference points and the shooting time of the UAV with the optimal correction effect of the BO-based CNN are obtained by two groups of comparative experiments, and the influence of the distance between structure and reference points on the correction effect of the BO-based CNN is determined by another group of comparative experiment. The static reference points are not required for the proposed method, which evidently enhances the applicability of UAVs; the conclusion of this paper has great guiding significance for the actual bridge vibration measurement.Multilevel Modeling of 1-3 Piezoelectric Energy Harvester Based on Porous Piezoceramics
https://jacm.scu.ac.ir/article_18008.html
The paper presents a computer analysis of the properties of a piezoelectric composite consisting of porous piezoceramic rods regularly arranged in an elastic matrix (piezocomposite with a connectivity of 1-3). The porous piezoceramic PZT-4 is used based on porous piezoceramics as an active material. The calculation of material properties is carried out based on a multilevel approach. First, the effective moduli of porous piezoceramics are determined, and then a 1-3 piezocomposite with rods having the calculated homogeneous properties is analyzed. The simulation uses the homogenization method based on the Hill lemma and the finite element method, as well as approximate analytical models. The effective properties of 1-3 composite are determined for various percentages of porosity of piezoceramic rods, which are a composite of 3-0 connectivity. Calculations were performed in the software package ACELAN-COMPOS. The calculated properties are used in finite element models to evaluate the effectiveness of composite materials in sensors and energy harvesting devices. Two cases of stiffness of an isotropic matrix are considered, which correspond to the stiffness of a porous composite at 50% and 80% porosity. The electromechanical properties, such as electro-mechanical coupling coefficient and output potential, for different transducers models made from the proposed composite are analyzed.Smart Gas Sensors: Materials, Technologies, Practical Applications, and Use of Machine Learning – A Review
https://jacm.scu.ac.ir/article_18013.html
The electronic nose, popularly known as the E-nose, that combines gas sensor arrays (GSAs) with machine learning has gained a strong foothold in gas sensing technology. The E-nose designed to mimic the human olfactory system, is used for the detection and identification of various volatile compounds. The GSAs develop a unique signal fingerprint for each volatile compound to enable pattern recognition using machine learning algorithms. The inexpensive, portable and non-invasive characteristics of the E-nose system have rendered it indispensable within the gas-sensing arena. As a result, E-noses have been widely employed in several applications in the areas of the food industry, health management, disease diagnosis, water and air quality control, and toxic gas leakage detection. This paper reviews the various sensor fabrication technologies of GSAs and highlights the main operational framework of the E-nose system. The paper details vital signal pre-processing techniques of feature extraction, feature selection, in addition to machine learning algorithms such as SVM, kNN, ANN, and Random Forests for determining the type of gas and estimating its concentration in a competitive environment. The paper further explores the potential applications of E-noses for diagnosing diseases, monitoring air quality, assessing the quality of food samples and estimating concentrations of volatile organic compounds (VOCs) in air and in food samples. The review concludes with some challenges faced by E-nose, alternative ways to tackle them and proposes some recommendations as potential future work for further development and design enhancement of E-noses.Impact of Microbial Activity and Stratification Phenomena on Generating/Absorbing Sutterby Nanofluid over a Darcy Porous Medium
https://jacm.scu.ac.ir/article_18021.html
The present article discusses the impact of microbial activity by considering Sutterby nanofluid over a stretching surface with the Brownian motion and porous medium. Thermophoretic effects are the measure concerned to balance the temperature of the fluid to generate the improved results. We include these effects in our model with some other parameters like Brownian motion and microbial activity. The stratification phenomenon is considered for the evaluation of heat generation/absorption over the horizontal sheet in the Sutterby nanofluid. The porous medium and chemical reaction with microbial activity is further analyzed in an incompressible Sutterby nanofluid. With the help of some suitable similarity transformations, the initial boundary conditions and the governing partial differential equations of our model are converted into the coupled structure of ordinary differential equations and final boundary conditions. The Spectral quasilinearization method (SQLM) is used to numerically solve these ordinary differential equations to evaluate the impacts of various parameters taken in our model. The graphical representation of different parameters is analyzed for the flow, temperature, solutal and microbial distribution. The coefficients of physical interest are also analyzed and show good results in favor. The rise of nanofluid parameters declines the flow profile of the fluid while enhancing the temperature profile and falling for the thermal stratification phenomenon. The Sutterby nanofluid model also incorporates the behavior of dilatant solutions and pseudoplastic which is helpful in various engineering processes and industries. This model is ideal for polymeric melts as well as high polymer resolutions.Investigation of Driving Torques at the Joints of Industrial Robot Arms based on the Topology Optimization Technique
https://jacm.scu.ac.ir/article_18028.html
This paper presents an investigation on the driving torques of industrial robot arm joints using the structural optimization method for Upper Arm (UA) link. The optimal criteria mention reducing the mass of UA link. The static and dynamic analysis problems are considered when robot moves in the vertical plane and in space. Results of these problems are used to perform the optimization of UA link structure. Stress and displacement values in static and dynamic analyses of the optimized link with a weight reduction of 39% and over 45% in volume show that it ensures to meet the set optimal criteria. A mathematical model of 6 degrees of freedom (DOF) robot is established to determine the kinematic and dynamic equations. The inverse kinematic and dynamic problems solving the algorithm of the redundant robot is effectively applied to determine the input values with the given motion trajectory of the end-effector point in the workspace with two different trajectories in a plane and space. The analysis results show that there is a change in driving torque values in a direction favorable for the operation of the joints for any trajectory when the mass of robot reduces. This is also verified by a simple 2DOF robot model presented in the Appendix with three different optimization methods. The reported results have essential implications for application of various topology optimization issues in order to positively change the driving torques at joints while well ensuring the functionality of robot arm.Stability Analysis of an Inflated, Axially Extended, Residually Stressed Circular Cylindrical Tube
https://jacm.scu.ac.ir/article_18023.html
Residual stress may have an important influence on the mechanical response of residually stressed materials. This paper is concerned with the effects of residual stress on the stability of inflated, axially extended, residually stressed circular cylindrical tube. To this end, the theory of small incremental deformations superimposed on a large underlying finite deformation is used. Asymmetric and axisymmetric types of bifurcation are considered. It is found that for residual stress parameter &gamma; of the same sign the effect of the residual stress is different depending on the type of bifurcation. For example, for asymmetric bifurcations with mode number m = 1 and with positive &gamma; inclusion of residual stress makes the tube more stable, on the other hand, for axisymmetric bifurcations inclusion of residual stress, corresponding to positive residual stress parameter &gamma;, leads to increase of instabilities. In all cases, residual stress with positive and negative residual stress parameter &gamma; leads to a symmetric character of bifurcation curves.Efficacy of a Modulated Viscosity-dependent Temperature/nanoparticles Concentration Parameter on a Nonlinear Radiative Electromagneto-nanofluid Flow along an Elongated Stretching Sheet
https://jacm.scu.ac.ir/article_18039.html
The purpose of the present communication is to investigate the flow of a radiative electromagnetic-Casson nanofluid past a stretching sheet under the impacts of a chemical reaction and nonlinear thermal radiation. To enrich the blood flow, a modulated viscosity/thermal conductivity dependent temperature/nanoparticles concentration parameter is included in the governing equations. The system of PDEs is transformed to ODEs by invoking similarity transformations and then solved numerically by the well- known fourth-order Runge-Kutta integration scheme based on shooting approach. The main factors affecting the Casson fluid&rsquo;s temperature profiles are revealed.Vibration Analysis of Shear Deformable Cylindrical Shells Made of Heterogeneous Anisotropic Material with Clamped Edges
https://jacm.scu.ac.ir/article_18044.html
The vibration behavior of moderately-thick inhomogeneous orthotropic cylindrical shells under clamped boundary conditions based on first-order shear deformation theory (FOSDT) is investigated using an analytical approach. The basic relationships for cylindrical shells composed of inhomogeneous orthotropic materials are established, and then partial differential equations of motion are derived in the framework of FOSDT. The analytical expression for frequency is found for the first time using the special approach for clamped boundary conditions. After checking the accuracy of obtained expressions, the effects of shear stress, orthotropy ratio and inhomogeneity on frequency values are examined in detail.Shape Optimization of Slotted Steel Plate Dampers using the Simulated Annealing Algorithm
https://jacm.scu.ac.ir/article_18062.html
This paper reports a procedure for maximizing the energy dissipation capacity (EDC) of a slotted steel plater damper by changing its initial geometrical shape. The methodology uses a simulated annealing algorithm to iteratively vary the slots' disposition, number, and geometry while improving the EDC. This capacity is computed for each tested configuration from a finite element analysis in ABAQUS, considering a cyclic displacement protocol. Five initial sections are enhanced, with the optimal one evoking a sand clock shape with two symmetric slots. The EDC increment is higher than 300%. It is observed that the objective function is multi-modal, and the optimal solution depends on the initial design. The proposed procedure is computationally easy to implement and requires less than fifty iterations to guarantee convergence in all cases.A Nonlinear Lagrangian Model for Plane Frames Pre-design
https://jacm.scu.ac.ir/article_18063.html
We propose a nonlinear lagrangian model that takes into account the dynamic interactions between the soil and a n-storey plane frame, which may be subjected to a seismic excitation through the soil. First, the interaction of the soil with the structure is modeled through a combination of springs and dampers representing the characteristics of the soil. In this model, the masses and stiffnesses of the structure elements are condensed to facilitate the analysis. Second, the Euler-Lagrange equations of the system are formulated and generalized for n floors. Third, these equations are discretized using the finite difference method to solve them using the Newton-Raphson method at each time step, during and after the seismic excitation, thus, determining the positions of each concentrated mass of the system. In addition, a linearization of the governing equations is performed in order to compare these results with those of the nonlinear model. Finally, the nonlinear model is used for the analysis of a 10-storey building, which has already been designed for linear geometric and material behaviors. For this analysis, the corrected acceleration record of the 2016 Pedernales (Ecuador) earthquake is used.Mathematical Model of Fluid Flow and Solute Transport in Converging-diverging Permeable Tubes
https://jacm.scu.ac.ir/article_18087.html
This article presents a mathematical model for fluid and solute transport in an ultra-filtered glomerular capillary. Capillaries &lrm;are assumed to be converging-diverging tubes with permeable boundaries. According to Starling's hypothesis, ultrafiltration is &lrm;related to the variations in hydrostatic and osmotic pressures in the capillary and Bowman's space and takes place along the &lrm;length of the capillary. The governing equations of fluid flow for the case of axisymmetric motion of viscous incompressible &lrm;Newtonian fluid have been considered along with the solute transfer equation. The non-uniform geometry has been mapped &lrm;into a finite regular computational domain via a coordinate transformation. Correspondingly, the governing equations are &lrm;transformed to the computational space and solved to get the velocity and pressure values. The solute transfer equation is &lrm;also solved numerically using a finite difference scheme. The solutions provide the predictions of the axial distribution of &lrm;hydrostatic pressure and osmotic pressure, velocities, and concentration profiles at various points along the axis and solute &lrm;clearance quantities along the capillary. The current results are in good agreement with the earlier findings in limiting cases of &lrm;cylindrical tubes with a constant radius. It is found that there is a significant effect of osmotic pressure on the solute &lrm;concentration. Using a set of data, the influence of various physiological parameters on the velocity components and solute &lrm;concentration are presented and discussed through graphs to correlate with physiological situations. The generic structure of &lrm;the current model also provides an acceptable approach to exploring fluid exchange in organs apart from the glomerular &lrm;capillary.&lrm;Hemispherical Resonator of a Rate-integrating Gyroscope: A Novel Method for Determination of Eigenfrequencies and Eigenforms in Presence of Imperfections
https://jacm.scu.ac.ir/article_18111.html
This paper investigates the problem of free vibrations of a hemispherical shell resonator of a rate-integrating gyroscope. A new realization of the approximate Ritz method for determining the frequencies and forms of free vibrations of an elastic hemisphere is proposed. Based on comparison with the results of direct finite-element modeling, it is shown that the proposed approach provides significantly greater accuracy in solving the spectral problem as compared to the solution based on analytical Rayleigh expressions for the forms of pure bending of the hemispherical surface. The importance of considering the potential energy of stretching of the mid-shell surface for the exact determination of frequencies and resonators waveforms for typical geometric parameters is noted. The degree of influence of the introduced refinements into the resonator&rsquo;s mathematical model on the values of frequency splitting associated with gyroscopic forces and mass imperfections is investigated.Analysis of Particulate Systems with Numerical Inverse Laplace Transform
https://jacm.scu.ac.ir/article_18112.html
The technique of numerical inversion of the Laplace transform is applied to solve the population balance equation (PBE). The model considers the dispersed phase systems in which nucleation and heterogeneous condensation are present. The studied phenomena model corresponds to a nonlinear integro-partial-differential equation. Test cases are solved considering two different collision mechanisms, the first-order removal mechanism and the effect of simultaneous coagulation and growth. Numerical results are compared with the analytical solution and with the literature. Based on these results, the technique applied in this work demonstrates to be a tool to solve problems in particulate systems, particularly for aerosol modeling where coagulation is the most important inter-particle mechanism affecting the size distribution.Delamination Analysis of Multilayered Functionally Graded Beams which Exhibit Non-linear Creep Behavior
https://jacm.scu.ac.ir/article_18143.html
General solution of the time-dependent strain energy release rate for delamination cracks in multilayered functionally graded load-bearing beam structures which exhibit non-linear creep is derived. The material is functionally graded along the length of layers. The Ramberg-Osgood stress-strain relation is used by assuming that the material in each layer behaves differently in tension and compression. The second term in the Ramberg-Osgood relation includes time dependence to treat the non-linear creep. The solution derived holds for multilayered functionally graded beams with arbitrary number of layers which have different width and material properties. The solution is applied for a delamination in a multilayered beam with a built-in end. An analysis is performed also by considering the balance of the energy in the multilayered beam configuration for the sake of verification. The effect of time is also studied. It is found that the strain energy release rate grows with the time. The results obtained here are useful for understanding the time-dependent delamination in multilayered functionally graded structural components subjected to non-linear creep.A Study on Effects of Thermal Radiative Dissipative MHD Non-Newtonian Nanofluid above an Elongating Sheet in Porous Medium
https://jacm.scu.ac.ir/article_18144.html
In this article, the ways where thermal radiation, besides other sources of heat, influence the magnetohydrodynamic stream of a Jeffery nanofluid across a widening sheet is investigated. To recover the accuracy of the nanofluid model, the effects of viscous indulgence, chemical response, Brownian motion, and thermophoresis have all been incorporated. The mathematical model of this system is first determined in PDEs format and then turned into ODEs format by similarity process. The numerical simulation of the ensuing nonlinear ODEs with subsequent periphery conditions is established by employing the Runge-Kutta fourth-order integration scheme with the shooting technique. The role of various stream considerations on stream, temperature, nanoparticle concentration, skin friction coefficient, Nusselt and Sherwood quantities are conveyed and explored in graphs and tables. In a limiting sense, the legitimacy of computational outcomes is assessed by comparing them to previously published data. The stream distribution quickens as the Deborah quantity accumulates, whereas the temperature and concentration profiles reflect the downward pattern.Comparative Study of the Spectral Method, DISPERSE and Other Classical Methods for Plotting the Dispersion Curves in Anisotropic Plates
https://jacm.scu.ac.ir/article_18181.html
This paper presents a comparative study of different methods for obtaining the dispersion curves of ultrasonic guided waves in anisotropic media. First, we present the classical algorithms used to find zeros and propose some improvements. Next, the spectral method is explained for modeling the guided waves in anisotropic materials while presenting a technique that can distinguish the modes present in the structure. The dispersion curves are plotted using a Matlab program and the results are compared with those of the DISPERSE software. In addition, a comparison with the results obtained by Nayfeh&rsquo;s works in the field of Nondestructive testing by ultrasonic guided waves is included. Then a discussion is developed to highlight the strengths of the spectral method. For proper non-destructive testing, we need reliable information about the modes that propagate in our waveguide. Both analytical and spectral approaches have limitations in obtaining the exact displacement and stress profiles in a plate media. To remedy this, normalization by the acoustic power is essential. Next, the displacement and stress fields obtained from the spectral method of the modes that can propagate in the plate are compared to those obtained analytically. A very good concordance is then noticed. Based on the results obtained, the spectral method presents a very good alternative for obtaining dispersion curves. It is a convergent method, stable, easy to implement with a very low calculation time.Buckling Behavior of Nanocomposite Plates with Functionally Graded Properties under Compressive Loads in Elastic and Thermal Environments
https://jacm.scu.ac.ir/article_18184.html
The buckling behavior of functionally graded carbon nanotube (FG-CNT) reinforced polymer-based moderately-thick plates subjected to in-plane biaxial compressive loads in elastic and thermal environments in the framework of first-order shear deformation plate theory (FSDPT) is investigated. First, the temperature-dependent properties of CNTs and nanocomposites are defined and their constitutive relations are established, then the stability and strain compatibility equations in elastic media are derived in the framework of the FSDPT. Then, by applying the Galerkin method to the basic equations, a closed-form solution is obtained for the critical biaxial compressive loads. The specific numerical analyzes and interpretations are made for various plate sizes and CNT patterns on the Winkler elastic foundation and in thermal environments within FSDPT and classical plate theory (CPT).Theory and Experiment in Predicting the Strength of Hybrid Fiber Metal Laminates
https://jacm.scu.ac.ir/article_18185.html
This article consists of three methodological stages. In the first one, a 3D numerical model of hybrid fiber metal laminates (FML) is developed inside ANSYS Workbench Explicit Dynamics modulus and used to predict their strengths according to the ASTM D3039M-17 standard. In the second stage, hybrid FMLs are produced according to the 4/3 stacking order in the laboratory environment, in line with the numerical model. Pure epoxy resin is initially used then reinforced with, 0.2% clay, GNP and SiO2 nanoparticles: comparative tensile tests are carried out according to the above-mentioned standards. At the final stage, experimental data, computer and theoretical (analytical) models of nanocrack formation processes in 7075-T6 Al matrix nanoparticle-filled hybrid nanocomposite materials under the influence of high-speed and quasi-static deformation regimes are investigated. It is observed that there is a 5% difference between results from simulation and experiment.Prediction of Interface Shear Strength of Heat Damaged Shear-keys using Nonlinear Finite Element Analysis
https://jacm.scu.ac.ir/article_18190.html
Push-off samples are simulated using nonlinear finite element analysis (NLFEA) to evaluate the effects of increased temperatures on the interface shear strength. Firstly, a control shear-key model is created, calibrated, and confirmed against independently published experimental data. Twenty-four NLFEA models are then created with different variables, including temperature (23&deg;C (Room Temperature), 250&deg;C (Raised temperature), 500&deg;C, and 750&deg;C and the number of steel stirrups (none, 1, 2, 3, 4, and 5). The NLFEA results demonstrate that the decreased fracture opening and slide in the damaged shear keys compared to the intact control sample represent the amazing effect of the number of steel stirrups. In addition, it has been revealed that the longitudinal shear force and slide, mode of failure, rigidity, and toughness are all significantly impacted by the degree of heat damage. In particular, a simplified approach is proposed for calculating the shear strength of push-off samples subjected to higher temperatures.Effect of Magnetic Field on Viscous Flow through Composite Porous Channel using Boundary Element Method
https://jacm.scu.ac.ir/article_18193.html
In this paper, we investigate the effect of magnetic field on two-dimensional flow of a viscous, incompressible fluid through composite porous channel using non-primitive boundary element method (BEM). We consider a rectangular channel consisting of two packings that are filled with fully saturated porous medium. It is assumed that both the porous regions are homogenous and isotropic with different permeabilities. Brinkman equation governs the fluid flow through porous media. We analyze the effect of Hartman number, stress-jump coefficient, Darcy number, thickness parameter, electrical conductivity ratio, and viscosity ratio on fluid mechanics. We present the effect of stress-jump coefficients on the interfacial velocity of the fluid against the thickness parameter and observe that the interfacial velocity increases with increasing stress-jump coefficients. We notice that for a fixed value of thickness parameter, the magnitude of vorticity (at lower and upper walls) increases with increasing Darcy number. Moreover, we observe that the magnitude of vorticity at the lower wall decreases and increases at the upper wall with increasing thickness parameter. We compute the Brinkman layer thickness near the interface of the composite porous channel in terms of several flow parameters and observe that the Brinkman layer thickness is strongly depend on the Hartman number, Darcy number, viscosity ratios, and stress-jump coefficient, respectively.Fluid-dynamic Simulations for Assessment of Dimensioning Methodologies of Pelton Turbine Buckets Considering the Initial Torque Overcoming
https://jacm.scu.ac.ir/article_18208.html
The growing demand for energy resources highlights the need to optimize traditional energy transformation systems. Pelton-type turbines, which are extensively used in micro-generation systems, can be designed using different methodologies, however, no consensus has been reached on which methodology guarantees greater efficiency. This work aims to compare the fluid-dynamic behavior at the first-time instants of Pelton turbines for micro-generation dimensioned by three different methodologies, namely, OLADE, Nechleba, and Thake, evaluating their capacity to overcome the initial torque. The results show that OLADE methodology leads to the best fluid-dynamic performance, whereas Nechleba fails to overcome the prescribed torque. In the Thake methodology, the impact of water on the back face of buckets and the formation of reverse pressure gradients can counter the turbine rotation.Multimode Fatigue Criteria for Filled Non-crystalizing Rubber under Positive R Ratios
https://jacm.scu.ac.ir/article_18220.html
Antivibration isolators are made from both crystalizing rubbers and non-crystalizing rubbers. Their fatigue resistance is different. Although the recently developed effective tensile stress criterionhas been validated in crystalizing rubber under different R ratios (the ratio between the minimum stress value and the maximum stress value), its application to non-crystalizing rubbers has never been verified. In this study, this criterion was tested against a non-crystalizing rubber using two types of samples under R &ge; 0 conditions for 168 fatigue cases with different loading modes. Considering that a shape change may also cause fatigue damage, a new shear stress criterion was derived and subsequently tested. The unified S-N curves (2&times;102 - 3&times;106 cycles) obtained have achieved narrow bands with a scatter factor of 1.35 with a correlation coefficient R2 &ge;&nbsp; 0.90 using these two criteria. This potential novel approach could be more effective than the current methods, which use fitting functions with adjustable parameters determined from an additional experiment. This offers greater choices and flexibility to engineers in their selection of the most appropriate suited criteria for their design in anti-vibration applications.&nbsp;&nbsp;&nbsp;