Journal of Applied and Computational MechanicsJournal of Applied and Computational Mechanics
http://jacm.scu.ac.ir/
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http://jacm.scu.ac.ir/
Feed provided by Journal of Applied and Computational Mechanics. Click to visit.Using the Matrix Method to Compute the Degrees of Freedom of Mechanisms
http://jacm.scu.ac.ir/article_12712_1522.html
In this paper, some definitions and traditional formulas for calculating the mobility of mechanisms are represented, e.g. Grubler formula, Somov - Malyshev formula, and Buchsbaum - Freudenstei. It is discussed that there are certain cases in which they are too ambiguous and incorrect to use. However, a matrix method is suggested based on the rank of the Jacobian of the mechanism and its application is investigated. It is shown that the matrix method will definitely lead to a correct answer; however, it is lengthy and consumes more computational effort. It is shown that in the cases the traditional formulas give a wrong answer and the matrix method gives the correct mobility. To compare the methods, several examples are given including the four bar planar linkage, the augmented four bar linkage, University of Maryland manipulator, Cartesian parallel manipulator (CPM), delta robot, orthoglide robot, and H4 parallel robot.Mon, 31 Jul 2017 19:30:00 +0100VOC level control by ventilation improvement of Flexography printing room using CFD modeling
http://jacm.scu.ac.ir/article_12721_1522.html
Using Computational Fluid Dynamics (CFD) technique, the dispersion contours and the exposure rate of Flexographic printing workers to VOCs in a printing department is evaluated. Firstly, VOCs distribution is determined in the printing room due to the existing ventilation system. Through next steps, 4 scenarios for lowering VOCs concentration and its exposure rate to workers are analyzed. Concentration distributions of ethylene glycol (MEG) as a representative of VOCs are determined for 4 scenarios. The results show that, regarding the existing ventilation, the concentration of MEG at the breathing height is 1×10-5 mg/m3 and it is higher than the standard permissible level. Finally, the findings of this study lead to lowered VOCs concentrations to 13.87×10-9 mg/m3 via changing the ventilation system for the Flexography Printing Room. Mon, 31 Jul 2017 19:30:00 +0100Investigating the Ultrasonic Assistance in the Tube Hydroforming Process
http://jacm.scu.ac.ir/article_12738_1522.html
The purpose of introducing ultrasonic vibrations in the tube hydroforming process is to create more formability by obtaining a lower corner radius, improve thickness distribution of the wall and provide good tribological conditions at the tube and the die interface. Vibrations imposed on the die create alternating gaps which improve the formability in the tube hydroforming process in the presence of ultrasonic vibrations. Therefore, we attempted to understand the processing mechanism of the ultrasonic tube hydroforming in the square die using the finite element method. Abaqus software was used in these simulations and the die was considered as a deformable element.Mon, 31 Jul 2017 19:30:00 +0100Haar Wavelet Collocation Method for Thermal Analysis of Porous Fin with Temperature-dependent ...
http://jacm.scu.ac.ir/article_12702_1522.html
In this study, the thermal performance analysis of porous fin with temperature-dependent thermal conductivity and internal heat generation is carried out using Haar wavelet collocation method. The effects of various parameters on the thermal characteristics of the porous fin are investigated. It is found that as the porosity increases, the rate of heat transfer from the fin increases and the thermal performance of the porous fin increases. The numerical solutions by the Haar wavelet collocation method are in good agreement with the standard numerical solutions.Mon, 31 Jul 2017 19:30:00 +0100Multi-boiling Heat Transfer Analysis of Convective Fin with Temperature-Dependent Thermal ...
http://jacm.scu.ac.ir/article_12637_0.html
In this study, heat transfer in a longitudinal rectangular fin with temperature-dependent thermal properties and internal heat generation under multi-boiling heat transfer where the local heat transfer coefficient is considered to vary with a power-law function of temperature has been analyzed using finite volume method. The coexistence of all the boiling modes is considered in this study. The developed heat transfer models and the corresponding numerical solutions were used to investigate the effects of various thermo-geometric parameters on the thermal performance of the longitudinal rectangular fin. From the results, it shows that the fin temperature distribution, the total heat transfer, and the fin efficiency are significantly affected by the thermo-geometric parameters of the fin. The results obtained in this analysis serve as basis for comparison of any other method of analysis of the problem and they also provide platform for improvement in the design of fin in heat transfer equipment.Wed, 15 Feb 2017 20:30:00 +0100Modified U-Slot Stacked Microstrip Patch Antenna for Ultra Wideband Applications in S Band, C ...
http://jacm.scu.ac.ir/article_12638_0.html
U-slot microstrip patch antennas were originally developed for bandwidth broadening applications. This paper presents a transmission line fed modify U-slot stacked rectangular microstrip patchantenna for Ultra Wide Band (UWB) communications, modified antenna have U cut loaded with parallel slit and corner slots and is printed on a dielectric substrate of FR4 with relative permittivity (εr)of 4.4, thickness of 1.59 mm & tangent loss of 0.025. The results show that the proposed antenna achieves an impedance bandwidth of 11.5 GHz (2.1 – 13.65 GHz) with Return Loss < (-10)dB. This antenna can be employed for ultra wideband applications in S Band, C Band & X Band. The proposed patch antenna is designed and simulated using IE3D 14.0 software. Simulation results are presented interms of Resonant Frequency, Return Loss, VSWR, Impedance Bandwidth and Impedance Matching.Wed, 31 May 2017 19:30:00 +0100Thermal-Hydraulics analysis of pressurized water reactor core by using single heated channel model
http://jacm.scu.ac.ir/article_12706_1522.html
Thermal hydraulics of nuclear reactor as a basis of reactor safety has a very important role in reactor design and control. The thermal-hydraulic analysis provides input data to the reactor-physics analysis, whereas the latter gives information about the distribution of heat sources, which is needed to perform the thermal-hydraulic analysis. In this study single heated channel model as a very fast model for predicting thermal hydraulics behavior of pressurized water reactor core has been developed. For verifying the results of this model, we used RELAP5 code as US nuclear regulatory approved thermal hydraulics code. The results of developed single heated channel model have been checked with RELAP5 results for WWER-1000. This comparison shows the capability of single heated channel model for predicting thermal hydraulics behavior of reactor core. Mon, 31 Jul 2017 19:30:00 +0100Effect of variable thermal expansion coefficient and nanofluid properties on steady natural ...
http://jacm.scu.ac.ir/article_12714_0.html
Steady state natural convection are numerically investigated in an enclosure using variable thermal conductivity, viscosity and thermal expansion coefficient of Al2O3–water nanofluid. Study has been conducted for a wide range of Rayleigh numbers (103≤ Ra ≤ 106), concentrations of nanoparticles (0% ≤ Φ ≤ 7%), enclosure aspect ratios (0.5 ≤ AR ≤ 2) and temperature differences between the cold and the hot walls (1≤ ∆T≤ 30). The main idea in this study is about the effect of temperature on natural convection pattern of nanofluid by changing nanoparticles concentration. Also changing thermal expansion coefficient with temperature is considerd in this study which will have significant effects on natural convection and has not been considerd before. In low Rayleigh numbers (Ra= 103) and for cavities with AR≥1, the pattern shown in the average Nusselt number versus volume fraction of nanoparticles diagram deteriorates by increasing ∆T.Thu, 23 Mar 2017 19:30:00 +0100Vibration and Static Analysis of Functionally Graded Porous Plates
http://jacm.scu.ac.ir/article_12716_1522.html
This research deals with free vibration and static bending of a simply supported functionally graded (FG) plate with the porosity effect. Material properties of the plate which are related to its change are position-dependent. Governing equations of the FG plate are obtained by using the Hamilton’s principle within first-order shear deformation plate theory. In solving the problem, the Navier solution is also used. In this study, the effect of the porosity and material distribution parameters on the static and vibration responses of the FG plate is presented and discussed.Mon, 31 Jul 2017 19:30:00 +0100The effect of small scale on the vibrational behavior of single-walled carbon nanotubes with a ...
http://jacm.scu.ac.ir/article_12740_1522.html
In this paper, free and forced vibration of simply-supported Single-walled carbon nanotube is investigated under the moving nanoparticle by considering nonlocal cylindrical shell model. To validate the theoretical results, modal analysis of nanotube is conducted using ANSYS commercial software. Excellent agreement is exhibited between the results of two different methods. Furthermore, the dynamic response of SWCNT under moving nanoparticle is also studied. It is assumed that the nanoparticle travels along the center of nanotube with constant velocity and the van der Waals force between CNT and particle is taken into account. The dynamic response of the SWCNT under the influence of C60 particle obtained using dynamic Green’s function and modal expansion. The obtained results show that the nonlocal scale effect decreases the natural frequency and dynamic displacement of the CNT.Mon, 31 Jul 2017 19:30:00 +0100FLOW AND HEAT TRANSFER ANALYSIS OF SODIUM ALGINATE CONVEYING COPPER NANOPARTICLES BETWEEN TWO ...
http://jacm.scu.ac.ir/article_12773_0.html
The steady incompressible flow of a non-Newtonian sodium alginate (SA) fluid conveying copper nanoparticles (Cu) flowing past two vertical parallel plates is considered in this paper, using the homotopy perturbation analytical scheme to solve the coupled nonlinear ordinary equations arising from the mechanics of fluid. The developed analytical solutions are used to investigate the effect of fluid flow and heat transfer parameters such as nanoparticle concentration, non-Newtonian parameter and viscosity variation parameter. Obtained analytical results when compared to existing works in literature are in satisfactory agreements. Also results obtained from this paper can be used to further the study of the behavior of sodium alginate in applications such as food processing, chemical and pharmaceutical industries.Thu, 20 Apr 2017 19:30:00 +0100Analytical predictions for the buckling of a nanoplate subjected to non-uniform compression ...
http://jacm.scu.ac.ir/article_12806_1522.html
In the present study, the buckling analysis of the rectangular nanoplate under biaxial non-uniform compression using the modified couple stress continuum theory with various boundary conditions has been considered. The simplified first order shear deformation theory (S-FSDT) has been employed and the governing differential equations have been obtained using the Hamilton’s principle. An analytical approach has been applied to obtain exact results from various boundary conditions. Due to the fact that there is not any research about the buckling of nanoplates based on the S-FSDT including the couple stress effect, the obtained results have been compared with the molecular dynamic simulation and FSDT papers which use the Eringen nonlocal elasticity theory. At the end, the results have been presented by making changes in some parameters such as the aspect ratio, the effect of various non-uniform loads and the length scale parameter.Mon, 31 Jul 2017 19:30:00 +0100The Finite Element Analysis for CFST Columns under Blast Loading
http://jacm.scu.ac.ir/article_12816_0.html
Concrete-filled steel columns have been extensively used in the world due to having all suitable characteristics of concrete and steel, more ductility, increasing concrete confinement using steel wall, large energy-absorption capacity and appropriate fire behavior. In the present paper, concrete-filled steel square columns have been simulated under the influence of blast load using ABAQUS software. The responses will be compared for scaled distances based on the distance to source and weight of the explosive material. As a result, it can be seen that although concrete deformation has been restricted using steel tube, the inner layer of concrete has been seriously damaged and column displacement is decreased by increasing scaled distance. We also concluded that concrete-filled steel columns have high ductility and blast resistance.Sun, 07 May 2017 19:30:00 +0100Bending, Buckling and Vibration of a Functionally Graded Porous Beam Using Finite Elements
http://jacm.scu.ac.ir/article_12817_0.html
This paper presents the effect of porosity on mechanical behaviors of power distribution functionally graded beam. The Euler-Bernoulli beam is assumed to describe the kinematic relations and constitutive equations. Because of technical problems and particle size shapes and micro-voids are created during the fabrication, which should be taken into consideration. Two porosity models are proposed. The first model describes properties in explicit form as linear functions of the porosity parameter. The second is a modified model which presents porosity and Young’s modulus in an implicit form, where the density is assumed as a function of the porosity parameter and Young’s modulus as a ratio of mass with porosity to the mass without porosity. The modified proposed model is more applicable than the first model. The finite element model is developed to solve the problem using MATLAB. Numerical results are presented to show the effects of porosity on mechanical beahviors of functionally graded beams.Sun, 07 May 2017 19:30:00 +0100Buckling analysis of micro sandwich plate with nano coating using modified couple stress theory
http://jacm.scu.ac.ir/article_12863_0.html
Present work investigates buckling of thick sandwich plate under biaxial nonuniform compression using modified couple stress theory with various boundary conditions. For this purpose, the top and bottom faces are orthotropic graphene sheets and for central core the isotropic soft materials have been investigated. The simplified first order shear deformation theory (S-FSDT) has been employed and the governing differential equations are obtained using Hamilton’s principle and considering the Von-Karman’s nonlinear strains. An analytical approach was applying to obtain exact results with different boundary conditions. Due to the fact that there are not any researches in stability of micro/nano sandwich plates based on S-FSDT including couple stress effect, so, obtained results have been compared with the FSDT papers which uses Eringen nonlocal elasticity.Tue, 16 May 2017 19:30:00 +0100Experimental Investigation on Radial Ball Bearing Parameters using Taguchi Method
http://jacm.scu.ac.ir/article_12993_0.html
In this work characteristics of various Ball Bearing parameters are studied under different loads and rotational speeds. By using Dimensional Analysis (DA) dimensionless parameters are computed which provides solution for group of parameters. This analysis can be accomplished by using Buckingham π-theorem. DA leads to reduction of the number of independent parameters involved in a problem. These independent parameters get expressed as dimensionless groups. These dimensionless groups are always ratios of important physical quantities involved in the problem of interest. In modeling and experimentation, its main function is to reduce the amount of independent variables, to simplify the solution and generalize the results. It becomes an effective method, especially if a complete mathematical model of the investigated process is not known. The present work also attempts the application of Buckingham π-theorem to find the influencing parameter π5 by using Taguchi Method.Thu, 15 Jun 2017 19:30:00 +0100Ritz method application to bending, buckling and vibration analyzes of Timoshenko beams via ...
http://jacm.scu.ac.ir/article_13028_0.html
Bending, buckling and vibration behaviors of nonlocal Timoshenko beams are investigated in this research using a variational approach. At first, governing equations of nonlocal Timoshenko beams are obtained and then weak form of these equations is outlined in this paper. Ritz technique is selected to investigate the behavior of nonlocal beams with arbitrary boundary conditions along them. To find the equilibrium equations of bending, buckling and vibration of these structures, an analytical procedure is followed. In order to verify the proposed formulation, the results for nonlocal Timoshenko beams with four classical boundary conditions are computed and compared, wherever possible. Since the Ritz technique can efficiently model the nano-sized structures with arbitrary boundary conditions, two types of beams with general boundary conditions are selected and new results are obtained.Fri, 23 Jun 2017 19:30:00 +0100A Method for Determination of the Fundamental Period of Layered Soil Profiles
http://jacm.scu.ac.ir/article_13034_0.html
In this study, a method is proposed for the determination of the fundamental period of layered soil profiles. A model considering the layered soil as shear type structure is used for the proposed method. Initially, the soil profile is divided into substructures. Then the stiffness matrices of the substructures that are considered as equivalent shear structures are assembled according to the Finite Element Method. Thereinafter, the stiffness matrices of the substructures are transformed into the Modified Finite Element Transfer Matrices, which take part in the literature. Finally, the system matrix is assembled using matrices of the substructures. The proposed method provides reduction in the size of the matrix. Therefore, analysis time is remarkably reduced. At the end of the study, the accuracy of the method is presented by the examples. Consequently, the proposed method offers a practical method for determination of the fundamental period of the soil.Sat, 01 Jul 2017 19:30:00 +0100Buckling and Vibration Analysis of Tapered Circular Nano-plate
http://jacm.scu.ac.ir/article_13035_0.html
In this paper, buckling and free vibration analysis of a circular tapered Nano-plate subjected to in-plane forces were studied.The linear variation of plate thickness was considered in radial direction. Nonlocal elasticity theory was employed to capture size-dependent effects. Raleigh Ritz method and differential transform method were utilized to obtain the frequency equations for simply supported and clamped boundary conditions. To verfy accuracy of Ritz method, differential transform method (DTM) also used to drive the size dependent natural frequencies of circular nano-plates. both methods reported good results.The validity of solutions was performed by comparing present results with those of the literature for both classical plate and nano plate. Effect of nonlocal parameter, mode number and taper parameter on the natural frequency were investigated. Results showed that Increasing the taper parameter causes increasing of buckling load and natural frequencies and its effects on the clamped boundary condition is more than simply support.Mon, 03 Jul 2017 19:30:00 +0100Reducing retrieval time in Automated Storage and Retrieval System with gravitational conveyor ...
http://jacm.scu.ac.ir/article_13038_0.html
The main objective of this study is to reduce the retrieval time of a list of products, by choosing, each time, the best combination of storage and retrieval rules.This is why we begin by implementing some storage rules in an Automated Storage/Retrieval System (Automated Storage and Retrieval System: AS/RS) fitted with a gravity conveyor. Some of these rules are dedicated to storage, the others to retrieval. The system is seen as a Multi-Agent System (MAS), where the produced agents are reactive agents that can interact to achieve a behavior (organizing the store). Our MAS is characterized by a decentralized control, which means that there is no preset plan. Each product merely applies a set of behavioral rules. This aims to choose the best product to be retrieved, in the shortest possible time. The product-type agents have no cognitive ability, but still perform complex tasks.Sun, 09 Jul 2017 19:30:00 +0100Investigation on the ultrasonic tube hydroforming in the bulging process using Finite element method
http://jacm.scu.ac.ir/article_13039_0.html
In ultrasonic tube hydroforming, the tube is hydro formed while the ultrasonic vibration is applied to the die. Prior studies provide experimental proof that ultrasonic tube hydroforming reduces corner radius, improves lubrication and uniform thickness. Use of ultrasonic vibration can decrease friction at the tube-die interface. Few attempts have been made to analyze the wire drawing while the ultrasonic vibrations were also applied during the processes. A detailed analysis and understanding of the mechanism of improvement is not possible with conventional experimental observation because the ultrasonic vibration processing phenomenon occurs at high speed. Therefore, we attempt to understand the processing mechanism of ultrasonic tube hydroforming using the finite element method (FEM).ABAQUS was used for the FEM. Forming force and formability in tube hydroforming analyzed. From these studies, we quantitatively clarified the mechanism of improved formability characteristics, such as decreased forming load and increasing bulging diameter.Sun, 09 Jul 2017 19:30:00 +0100Quasi-static transient thermal stresses in an elliptical plate due to sectional heat supply on ...
http://jacm.scu.ac.ir/article_13045_0.html
The paper is an attempt to determine quasi-static thermal stresses, in a thin elliptical plate which is subjected to transient temperature on the top face with zero temperature on the lower face and the homogeneous boundary condition of the third kind on the fixed elliptical curved surface. The solution to conductivity equation is elucidated by employing a classical method. The solution of stress components is achieved by using Goodier’s and Airy’s potential function, involving the Mathieu and modified functions and their derivatives. The numerical results obtained are accurate enough for practical purposes for the better understanding the underlying elliptic object and for the better estimates of the thermal effect of the thermoelastic problem. Conclusions emphasise the importance of better understanding the underlying elliptic structure, improved understanding of its relationship to circular object profile, and better estimates of the thermal effect of the thermoelastic problem.Thu, 13 Jul 2017 19:30:00 +0100Vibration Analysis of Material Size Dependent CNTs Using Energy Equivalent Model
http://jacm.scu.ac.ir/article_13086_0.html
This study presents modified continuum model to investigate vibration behavior of single and multi-CNTs. Two parameters are exploited to consider size dependence, one derived from energy equivalent model and the other from modified couple stress. The energy equivalent model that derived from the basis of molecular mechanics is exploited to describe size-dependent material properties for both zigzag and armchair structures of CNTs. A modified couple stress theory is proposed to capture the microstructure size effect by assisting material length scale. A modified kinematic Timoshenko nanobeam including shear deformation and rotary inertia effects is developed. The analytical solution is shown and verified with previously published works. A parametric study is performed to study the influences of length scale parameter, translation indices of the chiral vector, and CNTs orientation on the vibration behaviors of SWCNTs. The effect of number of tube layers on the fundamental frequency of CNTs is also presented.Tue, 01 Aug 2017 19:30:00 +0100Thermal Analysis of Convective-Radiative Fin with Temperature-dependent Thermal Conductivity ...
http://jacm.scu.ac.ir/article_13087_0.html
In this paper, Chebychev spectral collocation method is applied to the thermal analysis of convective-radiative straight fin with temperature-dependent thermal conductivity. The developed heat transfer model was used to analyse the thermal performance, establish the optimum thermal design parameters and also, investigate the effects of thermo-geometric parameters and thermal conductivity (nonlinear) parameters on the thermal performance of the fin. The study reveals that the rate of heat transfer from the fin increases as convective, radiative and magnetic parameters increases. The study established good agreements between the results obtained using Chebychev spectral collocation method and the results obtained using Runge-Kutta with shooting, homotopy perturbation and Adomian decomposition methods.Thu, 03 Aug 2017 19:30:00 +0100Study of Parameters Affecting Separation Bubble Size in High Speed Flows using k-ω Turbulence Model
http://jacm.scu.ac.ir/article_13088_0.html
Shock waves generated at different parts of vehicle interact with boundary layer over the surface at high Mach flows. The adverse pressure gradient across strong shock wave causes the flow to separate. At separation and reattachment points, peak loads are generated. The size of separation bubble in shock boundary layer interaction flows depends on various parameters. Reynolds-averaged Navier-Stokes equations using standard two-equation k-ω turbulence model is used in simulations for hypersonic flows over compression corner. Different deflection angles, ranging from 15o to 38o are simulated at Mach 9.22, to study its effect on separated flow. This is followed by a variation of Reynolds number based on boundary layer thickness, Re from 1x105 to 4x105. Simulations at different constant wall conditions Tw of cool, adiabatic and hot are also performed. Lastly, the effect of free stream Mach numbers M∞ in the range of 5 to 9 on interaction region is studied. It is observed that an increase in parameters,, Re and Tw results in an increase of separation bubble length, Ls and an increase in M∞ results in a decrease of Ls.Mon, 14 Aug 2017 19:30:00 +0100Transient natural convection in an enclosure with variable thermal expansion coefficient and ...
http://jacm.scu.ac.ir/article_13099_0.html
Transient natural convection are numerically investigated in an enclosure using variable thermal conductivity, viscosity and thermal expansion coefficient of Al2O3–water nanofluid. Study has been conducted for a wide range of Rayleigh numbers (103≤ Ra ≤ 106), concentrations of nanoparticles (0% ≤ ϕ ≤ 7%), enclosure aspect ratio (AR =1) and temperature differences between the cold and the hot walls (∆T= 30). Transient parameters such as development time and time–average Nusselt number along the cold wall are also presented as nondimentional form. Increasing Rayleigh number shorten non-dimensional time of initializing stage. By increasing the volume fraction of nanoparticles, the flow development time shows different behaviors for various Rayleigh numbers. Non-dimensional development time decreases by enhancing nanoparticles concentration.Tue, 15 Aug 2017 19:30:00 +0100