Journal of Solid MechanicsJournal of Solid Mechanics
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Feed provided by Journal of Solid Mechanics. Click to visit.Analysis of Viscoelastic Functionally Graded Sandwich Plates with CNT Reinforced Composite Face ...
http://jsm.iau-arak.ac.ir/article_668608_1132799.html
In this article, bending, buckling, and free vibration of viscoelastic sandwich plate with carbon nanotubes reinforced composite facesheets and an isotropic homogeneous core on viscoelastic foundation are presented using a new first order shear deformation theory. According to this theory, the number of unknown’s parameters and governing equations are reduced and also the using of shear correction factor is not necessary because the transverse shear stresses are directly computed from the transverse shear forces by using equilibrium equations. The governing equations obtained using Hamilton’s principle is solved for a rectangular viscoelastic sandwich plate. The effects of the main parameters on the vibration characteristics of the viscoelastic sandwich plates are also elucidated. The results show that the frequency significantly decreases with using foundation and increasing the viscoelastic structural damping coefficient as well as the damping coefficient of materials and foundation.Sat, 30 Nov 2019 20:30:00 +0100Temperature-Dependent Buckling Analysis of Functionally Graded Sandwich Cylinders
http://jsm.iau-arak.ac.ir/article_670341_0.html
This study is limited to study of buckling analysis of a sandwich cylindrical shell with functionally graded face sheets and homogenous core. High-order sandwich plate theory is improved by considering the in-plane stresses of the core that usually are ignored in the analysis of sandwich structures. Assume that all properties of the face sheets and the core are temperature dependent. Strain components are obtained by using the nonlinear Von-Karman type relations. The equilibrium equations are derived via principle of minimum potential energy. Analytical solution for static analysis of simply supported sandwich conical shells with functionally graded face sheets under axial in-plane compressive loads and in the temperature environments is performed by using Navier’s solution. The results show the critical dimensionless static axial loads are affected by the configurations of the constituent materials, compositional profile variations, temperature and the variation of the sandwich geometry. The comparisons show that the present results are in the good agreement with the numerical results.Sat, 04 Jan 2020 20:30:00 +0100Dispersion of Torsional Surface Wave in a Pre-Stressed Heterogeneous Layer Sandwiched Between ...
http://jsm.iau-arak.ac.ir/article_668609_1132799.html
The study of surface waves in a layered media has their viable application in geophysical prospecting. This paper presents an analytical study on the dispersion of torsional surface wave in a pre-stressed heterogeneous layer sandwiched between a pre-stressed anisotropic porous semi-infinite medium and gravitating anisotropic porous half-space. The non-homogeneity within the intermediate layer and upper semi-infinite medium is assumed to rise up, because of quadratic variation and exponential variation in directional rigidity, pre-stress, and density respectively. The displacement dispersion equation for the torsional wave velocity has been expressed in the term of Whitaker function and their derivatives. Dispersion relation and the closed-form solutions have been obtained analytically for the displacement in the layer and the half-spaces. It is determined that the existing geometry allows torsional surface waves to propagate and the observe exhibits that the layer width, layer inhomogeneity, frequency of heterogeneity in the heterogeneous medium has a great impact on the propagation of the torsional surface wave. The influence of inhomogeneities on torsional wave velocity is also mentioned graphically by means plotting the dimensionless phase velocity against non-dimensional wave number for distinct values of inhomogeneity parameters.Sat, 30 Nov 2019 20:30:00 +0100Vibration Analysis of Rotary Tapered Axially Functionally Graded Timoshenko Nanobeam in Thermal ...
http://jsm.iau-arak.ac.ir/article_670258_0.html
In this paper, vibration analysis of rotary tapered axially functionally graded (AFG) Timoshenko nanobeam is investigated in a thermal environment based on nonlocal theory. The governing equations of motion and the related boundary conditions are derived by means of Hamilton’s principle based on the first order shear deformation theory of beams. The solution method is considered using generalized differential quadrature element (GDQE) method. The accuracy of results are validated by other results reported in other references. The effect of various parameters such as AFG index, rate of cross section change, angular velocity, size effect and boundary conditions on natural frequencies are discussed comprehensively. The results show that with increasing angular velocity, non-dimensional frequency is increased and it depends on size effect parameter. Also, in the zero angular velocity, it can be seen with increasing AFG index, the frequencies are reducing, but in non-zero angular velocity, AFG index shows complex behavior on frequency.Wed, 01 Jan 2020 20:30:00 +0100Analysis of Thermal-Bending Stresses in a Simply Supported Annular Sector Plate
http://jsm.iau-arak.ac.ir/article_668610_1132799.html
The present article deals with the analysis of thermal-bending stresses in a heated thin annular sector plate with simply supported boundary condition under transient temperature distribution using Berger’s approximate methods. The sectional heat supply is on the top face of the plate whereas the bottom face is kept at zero temperature. In this study, the solution of heat conduction is obtained by the classical method. The thermal moment is derived on the basis of temperature distribution, and its stresses are obtained using thermally induce resultant moment and resultant forces. The numerical calculations are obtained for the aluminium plate in the form of an infinite series involving Bessel functions, and the results for temperature, deflection, resultant bending moments and thermal stresses have been illustrated graphically with the help of MATHEMATICA software.Sun, 29 Dec 2019 20:30:00 +0100Size Dependent Nonlinear Bending Analysis of a Flexoelectric Functionally Graded Nano-Plate ...
http://jsm.iau-arak.ac.ir/article_670598_0.html
The effects of flexoelectricity on thermo-electro-mechanical behavior of a functionally graded electro-piezo-flexoelectric nano-plate are investigated in this paper using flexoelectric modified and the Kirchhoff classic theories. Moreover, using the variation method and the principle of minimum potential energy for the first time, the coupled governing nonlinear differential equations of the nano-plate and their associated boundary conditions are obtained. The functionally graded nano-plate is modeled using a power law equation along the plate thickness direction. The nano-plate behavior is analyzed under mechanical, electrical, and thermal loadings with different boundary conditions. It should be noted that the direct and reverse flexoelectric effects under different loading conditions were investigated. Finally, the important quantities such as: the nano-plate deflection, the induced electrical voltage for different values of the length parameter, the power index related to the functionally graded behavior model and the geometric ratio parameter are determined. The results indicate that in the presence of flexoelectricity, the rigidity of the nano-plate increases. Also, the deflection and the generated electric potential along nano-plate thickness decreases. Finally, induced polarization decreases as a linear temperature variation is applied on the nano-plate.Sun, 12 Jan 2020 20:30:00 +0100Investigating the Effect of Joint Geometry of the Gas Tungsten Arc Welding Process on the ...
http://jsm.iau-arak.ac.ir/article_668764_1132799.html
Although a few models have been proposed for 3D simulation of different welding processes, 2D models are still more effective in design goals, thus more popular due to the short-time analysis. In this research, replacing "time" by the "third dimension of place", the gas tungsten arc welding process was simulated by the finite element method in two dimensions and in a short time with acceptable accuracy in two steps (non-coupled thermal and mechanical analysis). A new method was proposed for applying initial conditions using temperature values calculated in the preceding step of the solution; this trick reduces nonlinear effects of birth of elements and considerably reduces analysis time. A new parameter was defined for determining thermal boundary conditions to determine the contribution of the imposed surface and volumetric thermal loads. The effect of weld joint geometry on residual stresses and distortion was studied based on a validated simulation program. Results suggest that changing the joint geometry from V-into X-groove, the maximum values of residual stress and distortion are reduced by 20% and 15%, respectively.Sun, 29 Dec 2019 20:30:00 +0100Hygrothermal Creep and Stress Redistribution Analysis of Temperature and Moisture Dependent ...
http://jsm.iau-arak.ac.ir/article_670302_0.html
In this article, the time-dependent stress redistribution analysis of magneto-electro-elastic (MEE) thick-walled sphere subjected to mechanical, electrical, magnetic and uniform temperature gradient as well as moisture concentration gradient is presented. Combining constitutive equations of MEE with stress-strain relations as well as strain-displacement relations results in obtaining a differential equation in which there are the creep strains. At the first step, discounting creep strains in the mentioned equation, an analytical solution for the hygro-thermo-magneto-electro-elastic behavior is achieved at the initial state. After that, the creep stress rates can be achieved by keeping only the creep strains in the differential equation for the steady-state condition. The analysis is done by applying the Prandtl-Reuss equations as well as Norton’s law in creep behavior modeling. Finally, the history of stresses, displacement as well as magnetic and potential field, at any time, is achieved using an iterative method. Results show that the increase in tensile hoop stress resulted from creep progress must be considered in design progress. Also, the effect of hygrothermal loading is more extensive after creep evolution.Fri, 03 Jan 2020 20:30:00 +0100Semi-Active Pulse-Switching SSDC Vibration Suppression using Magnetostrictive Materials
http://jsm.iau-arak.ac.ir/article_668829_1132799.html
One of the best vibration control methods using smart actuators are semi-active approaches which are as strong as active methods and need no external energy supply such as passive ones. Compared with piezoelectric-based, magnetostrictive-based control methods have higher coupling efficiency, higher Curie temperature, higher flexibility to be integrated with curved structures and no depolarization problems. Semi-active methods are well-developed for piezoelectrics but magnetostrictive-based approaches are not as efficient, powerful and well-known as piezoelectric-based methods. The aim of this work is to propose a powerful semi-active control method using magnetostrictive actuators. In this paper a new type of semi-active suppression methods using magnetostrictive materials is introduced which contains an equipped vibrating structure with magnetostrictive patches wound by a pick-up coil connected to an electronic switch and a capacitor. The novelty of the proposed damping method is switching on the coil current signal using mentioned switch and capacitor which is briefly named SSDC (synchronized switch damping on capacitor). In this paper the characteristics of the semi-active pulse-switching damping technique with magnetostrictive materials are studied and numerical results show significant damping for almost all types of excitations. Sun, 29 Dec 2019 20:30:00 +0100Method of Green’s Function for Characterization of SH Waves in Porous-Piezo Composite ...
http://jsm.iau-arak.ac.ir/article_670426_0.html
An approach of Green’s function is adopted to solve the inhomogeneous linear differential equations representing wave equations in piezo-composite materials. In particular, transference of horizontally polarised shear (SH) waves is considered in bedded structure comprising of porous-piezo electric layer lying over a heterogeneous half-space. Propagation of SH-waves is considered to be influenced by point source, situated in the heterogeneous substrate. A closed form analytical solution is obtained to establish the dispersion relation. Remarkable influence of different parameters (like elastic constant, piezoelectric constant, heterogeneity parameter, initial stress and layers thickness) on the phase and group velocity are shown graphically. Moreover, a special case of present study is shown by replacing the porous piezoelectric material with piezoelectric material. Some numerical examples are illustrated by taking the material constants of Lead Zirconate Titanate (PZT-1, PZT-5H and PZT-7) for the porous piezoelectric layer where the phase velocity of SH waves is high rather than that of piezoelectric layer.Tue, 07 Jan 2020 20:30:00 +0100Pull-In Instability of MSGT Piezoelectric Polymeric FG-SWCNTs Reinforced Nanocomposite ...
http://jsm.iau-arak.ac.ir/article_668611_1132799.html
In this paper, the pull-in instability of piezoelectric polymeric nanocomposite plates reinforced by functionally graded single-walled carbon nanotubes (FG-SWCNTs) based on modified strain gradient theory (MSGT) is investigated. Various types of SWCNTs are distributed in piezoelectric polymeric plate and also surface stress effect is considered in this research. The piezoelectric polymeric nanocomposite plate is subjected to electro-magneto-mechanical loadings. The nonlinear governing equations are derived from Hamilton's principle. Then, pull-in voltage and natural frequency of the piezoelectric polymeric nanocomposite plates are calculated by Newton-Raphson method. There is a good agreement between the obtained and other researcher results. The results show that the pull-in voltage and natural frequency increase with increasing of applied voltage, magnetic field, FG-SWCNTs orientation angle and small scale parameters and decrease with increasing of van der Waals and Casimir forces, residual surface stress constant. Furthermore, highest and lowest pull-in voltages are belonging to FG-X and FG-O distribution types of SWCNTs.Sun, 29 Dec 2019 20:30:00 +0100Studying the Mechanical and Thermal Properties of Polymer Nanocomposites Reinforced with ...
http://jsm.iau-arak.ac.ir/article_670256_0.html
In this study, the mechanical and thermal behavior of the nano-reinforced polymer composite reinforced by Montmorillonite (MMT) nanoparticles is investigated. Due to low cost of computations, the 3D representative volume elements (RVE) method is utilized using ABAQUS finite element commercial software. Low density poly ethylene (LDPE) and MMT are used as matrix and nanoparticle material, respectively. By using various geometric shapes and weight fractions of nanoparticle, the mechanical and thermal properties such as Young’s modulus, shear modulus, heat expansion coefficient and heat transfer coefficient are studied. Due to addressing the properties of interfacial zone between the matrix and nanoparticle, finite element modeling is conducted in two ways, namely, perfect bonding and cohesive zone. The results are validated by comparing with experimental results reported in literature and a reasonable agreement was observed. The prediction function for Young’s modulus is presented by employing Genetic Algorithm (GA) method. Also, Kerner and Paul approaches as theoretical models are used to calculate the Young’s modulus. It was finally concluded that the magnitude of the Young’s and shear modules increase by adding MMT nanoparticles. Furthermore, increment of MMT nanoparticles to polymer matrix nanocomposite decrease the heat expansion and heat transfer coefficients.Wed, 01 Jan 2020 20:30:00 +0100Impact of Initial Stress on Reflection and Transmission of SV-Wave between Two Orthotropic ...
http://jsm.iau-arak.ac.ir/article_668613_1132799.html
Reflection and transmission of plane waves between two initially stressed thermoelastic half-spaces with orthotropic type of anisotropy is studied. Incidence of a SV-type wave from the lower half-space is considered and the amplitude ratios of the reflected and transmitted SV-wave, P-wave and thermal wave are obtained by using appropriate boundary conditions. Numerical computation for a particular model is performed and graphs are plotted to study the effect of angle of incidence of the wave and the initial stress parameters of the half-spaces. From the graphical results, it is found that the modulus of reflection and transmission coefficients of the thermal wave is very less in comparison to reflection and transmission coefficients of P- and SV-waves. It is also observed that for vertical incidence of SV-wave we have only reflected and refracted SV-waves and there is no reflected or refracted P and thermal waves, whereas for horizontal incidence of SV-wave there exists only reflected SV-wave and no other reflected or transmitted wave exists. Moreover, it is found that all the reflection and transmission coefficients are strongly affected by the initial stress parameters of the both half-spaces.Sun, 29 Dec 2019 20:30:00 +0100Determination of the Effective Parameters for Perforated Functionally Graded Plates with ...
http://jsm.iau-arak.ac.ir/article_670386_0.html
This paper investigates the moments and stress resultants from infinite FG laminates with different polygonal cutouts subject to uniaxial tensile load. The analytical solution used for the calculation of stress resultants and moments is the basis of the complex-variable method and conformal mapping function. The impact of various factors, namely cutout orientation angle, cutout aspect ratio as well as the cutout corner curve on stress distribution and moment resultants is studied. The effect of the aforementioned parameters around triangular, square, pentagonal and hexagonal cutout is analyzed. The mechanical characteristics of the graded plates are hypothesized to vary throughout the thickness exponentially. Finite element numerical solution is employed to examine the results of the present analytical solution. This comparison showed a favorable agreement level among the acquired analytical and numerical outcomes.Mon, 06 Jan 2020 20:30:00 +0100Efficient Higher-Order Shear Deformation Theories for Instability Analysis of Plates Carrying a ...
http://jsm.iau-arak.ac.ir/article_668763_1132799.html
The dynamic performance of structures under traveling loads should be exactly analyzed to have a safe and reasonable structural design. Different higher-order shear deformation theories are proposed in this paper to analyze the dynamic stability of thick elastic plates carrying a moving mass. The displacement fields of different theories are chosen based upon variations along the thickness as cubic, sinusoidal, hyperbolic and exponential. The well-known Hamilton’s principle is utilized to derive equations of motion and then they are solved using the Galerkin method. The energy-rate method is used as a numerical method to calculate the boundary curves separating the stable and unstable regions in the moving mass parameters plane. Effects of the relative plate thickness, trajectories radii and the Winkler foundation stiffness on the system stability are examined. The results obtained in this research are compared, in a special case, with those of the Kirchhoff’s plate model for the validation. Sun, 29 Dec 2019 20:30:00 +0100Free Vibration Analysis of Nonlinear Circular Plates Resting on Winkler and Pasternak Foundations
http://jsm.iau-arak.ac.ir/article_670254_0.html
Dynamic behaviour of nonlinear free vibration of circular plate resting on two-parameters foundation is studied. The governing ordinary differential equation is solved analytically using hybrid Laplace Adomian decomposition method. The analytical solutions obtained are verified with existing results in literature. The analytical solutions are used to determine the influence of elastic foundation, radial and circumferential stress on natural frequency of the plate. Also, the radial and circumferential stress determined. From the results, it is observed that, increase in elastic foundation parameter increases the natural frequency of the plate. It is recorded that the modal radial and circumferential stress affect the extrema mode of the plate. It is hoped that the present study will contribute to the existing knowledge in the field of vibration analysis of engineering structures.Wed, 01 Jan 2020 20:30:00 +0100Static Bending Analysis of Foam Filled Orthogonally Rib-Stiffened Sandwich Panels: A ...
http://jsm.iau-arak.ac.ir/article_668614_1132799.html
The current study presents a mathematical modeling for sandwich panels with foam filled orthogonally rib-stiffened core using Heaviside distribution functions. The governing equations of the static problem have been derived based on classical lamination theory. The present model contains three displacement variables considering all of the stiffness coefficients. A closed form solution using Galerkin’s method is presented for simply supported sandwich panels with foam filled orthogonally rib-stiffened core subjected to uniform lateral static pressure. Compared to previous researches, the present work is comprehensive enough to be used for symmetric, unsymmetric, laminated or filament wound panels with orthogrid stiffeners. The accuracy of the solution is checked both through comparisons with previous works, and the results of simulation with ABAQUS software.Sun, 29 Dec 2019 20:30:00 +0100Natural Frequency of Rotating Single-Walled Carbon Nanotubes with Considering Gyroscopic Effect
http://jsm.iau-arak.ac.ir/article_670376_0.html
This paper investigates the bending vibration of rotating single-walled carbon nanotubes (SWCNTs) based on nonlocal theory. To this end, the rotating SWCNTs system modeled as a beam with a circular cross section and the Euler-Bernoulli beam theory (EBT) is applied with added effects such as rotary inertia, gyroscopic effect and rotor mass unbalance. Using nonlocal theory, two coupled sixth order partial differential equations that govern the vibration of rotating SWCNTs are derived. To obtain the natural frequency and dynamic response of the nanorotor system, the equation of motion for the rotating SWCNTs are solved. It is found that there are two frequencies in the frequency spectrum. The positive rootintroduced as forward whirling mode, while the negative root represents backward whirling mode. The detailed mathematical derivations are presented while the emphasis is placed on investigating the effect of the several parameters such as, tube radius, angular velocity and small scale parameter on the vibration behavior of rotating nanotubes. It is explicitly shown that the vibration of a spinning nanotube is significantly influenced by these effects. To validate the accuracy and efficiency of this work, the results obtained herein are compared with the existing theoretical and experimental results and good agreement is observed. To the knowledge of authors, the vibration of rotating SWCNTs considering gyroscopic effect has not investigated analytically yet and then the results generated herein can be served as a benchmark for future works.Mon, 06 Jan 2020 20:30:00 +0100The Effects of Forming Parameters on the Single Point Incremental Forming of 1050 Aluminum ...
http://jsm.iau-arak.ac.ir/article_668616_1132799.html
The single point incremental forming (SPIF) is one of the dieless forming processes which is widely used in the sheet metal forming. The correct selection of the SPIF parameters influences the formability and quality of the product. In the present study, the Gurson-Tvergaard Needleman (GTN) damage model was used for the fracture prediction in the numerical simulation of the SPIF process of aluminum alloy 1050. The GTN parameters of AA 1050 sheet were firstly identified by the numerical simulation of tensile test and comparison of the experimental and numerical stress-strain curves. The identified parameters of the GTN damage model were used for fracture prediction in the SPIF process. The numerical results of the fracture position, thickness variation across the sample and forming height were compared with the experimental results. The numerical results had good agreement with the experimental ones. The effect of SPIF main parameters was investigated on the formability of samples by the verified numerical model. These parameters were tool rotation speed, tool feed rate, tool diameter, wall angle of the sample, vertical pitch, and friction between the tool and the blank.Sun, 29 Dec 2019 20:30:00 +0100A Comparative Study of Tooth Wear, Mechanical Power Losses and Efficiency in Normal and High ...
http://jsm.iau-arak.ac.ir/article_670276_0.html
The surface tooth wear which occurs at the gear contact region due to inadequate contact strength of the tooth is one of the predominant modes of gear failures. Currently, higher contact ratio spur gears are increasingly used in power transmission applications such as aircraft, wind turbine, automobiles and compact tracked vehicles due to their high load carrying capacity. In this work, the direct design is found to be one of the efficient gear design methods to reduce the tooth surface wear on high contact ratio asymmetric spur gears. Asymmetric gear tooth is defined as one whose tooth geometry of the drive and coast sides is not symmetric. Asymmetry between tooth sides is achieved by providing two different pressure angles at the respective coast and drive side pitch circles. The area of existence diagrams for normal and high contact ratio gears have been developed to select suitable design solution with the given variables of gear ratio, contact ratio and teeth number. The contact load capacity, wear resistance, power losses and mechanical efficiency have also been deduced for directly designing normal and high contact ratio asymmetric spur gears.Wed, 01 Jan 2020 20:30:00 +0100FEM Implementation of the Coupled Elastoplastic/Damage Model: Failure Prediction of Fiber ...
http://jsm.iau-arak.ac.ir/article_668617_1132799.html
The coupled damage/plasticity model for meso-level which is ply-level in case of Uni-Directional (UD) Fiber Reinforced Polymers (FRPs) is implemented. The mathematical formulations, particularly the plasticity part, are discussed in a comprehensive manner. The plastic potential is defined in effective stress space and the damage evolution is based on the theory of irreversible thermodynamics. The model which is illustrated here has been implemented by different authors previously but, the complete pre-requisite algorithm ingredients used in the implicit scheme implementation are not available in the literature. This leads to the complexity in its implementation. Furthermore, this model is not available as a built-in material constitutive law in the commercial Finite Element Method (FEM) softwares. To facilitate the implementation and understanding, all the mathematical formulations are presented in great detail. In addition, the elastoplastic consistent operator needed for implementation in the implicit solution scheme is also derived. The model is formularized in incremental form to be used in the Return Mapping Algorithm (RMA). The quasi-static load carrying capability and non-linearity caused by the collaborative effect of damage and plasticity is predicted with User MATerial (UMAT) subroutine which solves the FEM problem with implicit techniques in ABAQUS.Sun, 29 Dec 2019 20:30:00 +0100A New Three-Dimensional Sector Element for Circular Curved Structures Analysis
http://jsm.iau-arak.ac.ir/article_670319_0.html
In this research paper, the formulation of a new three-dimensional sector element based on the strain approach is presented for plate bending problems and linear static analysis of circular structures. The proposed element has the three essential external degrees of freedom (Ur, Vθ and W) at each of the eight corner nodes. The displacements field of the present element is based on assumed functions for the different strains satisfying the compatibility equations. The effectiveness of the present element is applied through several tests related to plate bending problems and linear static analysis of circular structures. The results of the developed element have been compared with analytical and other numerical solutions available in the literature. The obtained results show the excellent performances and precision of the present element. It is found that the new three-dimensional sector element is more accurate and efficient than the three-dimensional classical element based on displacement approach.Sat, 04 Jan 2020 20:30:00 +0100Chip Formation Process using Finite Element Simulation “Influence of Cutting Speed Variation”
http://jsm.iau-arak.ac.ir/article_668618_1132799.html
The main aim of this paper is to study the material removal phenomenon using the finite element method (FEM) analysis for orthogonal cutting, and the impact of cutting speed variation on the chip formation, stress and plastic deformation. We have explored different constitutive models describing the tool-workpiece interaction. The Johnson-Cook constitutive model with damage initiation and damage evolution has been used to simulate chip formation. Chip morphology, Stress and equivalent plastic deformation has been presented in this paper as results of chip formation process simulation using Abaqus explicit Software. According to simulation results, the variation of cutting speeds is an influential factor in chip formation, therefore with the increasing of cutting speed the chip type tends to become more segmented. Additionally to the chip formation and morphology obtained from the finite element simulation results, some other mechanical parameters; which are very difficult to measure on the experimental test, can be obtained through finite element modeling of chip formation process.Sun, 29 Dec 2019 20:30:00 +0100The Dynamic and Vibration Response of Composite Cylindrical Shell Under Thermal Shock and Mild ...
http://jsm.iau-arak.ac.ir/article_670342_0.html
In this article, the vibration and dynamic response of an orthotropic composite cylindrical shell under thermal shock loading and thermal field have been investigated. The problem is that the shell is initially located at a first temperature, and some tension caused by a mild heat field is created, then the surface temperature of the cylinder suddenly increases. The partial derivative equations of motion are in the form of couplings with the heat equations. First, the equations of motion are derived by the Hamilton principle, here first-order shear theory and considering strain-shift relations of Sanders are used. Then, the equation system including the equations of motion and energy equations by the Runge–Kutta fourth-order methodare solved. In this study, the effects of length, temperature, thickness and radius parameters on natural frequencies and intermediate layer displacement are investigated. The results show that the increase in external temperature decreases the natural frequency and increases the displacement of the system. Also, the results of radial transitions were evaluated with previous studies and it was found that it is in good agreement with the results of previous papers.Sat, 04 Jan 2020 20:30:00 +0100An Axisymmetric Contact Problem of a Thermoelastic Layer on a Rigid Circular Base
http://jsm.iau-arak.ac.ir/article_668619_1132799.html
We study the thermoelastic deformation of an elastic layer. The upper surface of the medium is subjected to a uniform thermal field along a circular area while the layer is resting on a rigid smooth circular base. The doubly mixed boundary value problem is reduced to a pair of systems of dual integral equations. The both system of the heat conduction and the mechanical problems are calculated by solving a dual integral equation systems which are reduced to an infinite algebraic one using a Gegenbauer’s formulas. The stresses and displacements are then obtained as Bessel function series. To get the unknown coefficients, the infinite systems are solved by the truncation method. A closed form solution is given for the displacements, stresses and the stress singularity factors. The effects of the radius of the punch with the rigid base and the layer thickness on the stress field are discussed. A numerical application is also considered with some concluding results.Sun, 29 Dec 2019 20:30:00 +0100Nonlocal Dispersion Analysis of a Fluid – Conveying Thermo Elastic Armchair Single Walled ...
http://jsm.iau-arak.ac.ir/article_670303_0.html
In this work, the nonlocal elastic waves in a fluid conveying armchair thermo elastic single walled carbon nanotube under moving harmonic load is studied using Eringen nonlocal elasticity theory via Euler Bernoulli beam equation. The governing equations that contains partial differential equations for single walled carbon nanotube is derived by considering thermal and Lorenz magnetic force. The small scale interactions induced by the nano tubes are simulated by the non-local effects. The time domain responses are obtained by using both modal super position method and Newmarks’s direct integration method. The effect of nonlocal parameter, thermal load, magnetic field of the moving harmonic load on the dynamic displacement of SWCNT is discussed. The results obtained show that the dynamic displacement of fluid conveying SWCNT ratio is significantly affected by the load velocity and the excitation frequency. This type of results presented here, will provide useful information for researchers in structural nano science to understand the small scale response of elastic waves coupled with thermo elasticity and some field forces.Fri, 03 Jan 2020 20:30:00 +0100Rigidity and Irregularity Effect on Surface Wave Propagation in a Fluid Saturated Porous Layer
http://jsm.iau-arak.ac.ir/article_668621_1132799.html
The propagation of surface waves in a fluid- saturated porous isotropic layer over a semi-infinite homogeneous elastic medium with an irregularity for free and rigid interfaces have been studied. The rectangular irregularity has been taken in the half-space. The dispersion equation for Love waves is derived by simple mathematical techniques followed by Fourier transformations. It can be seen that the phase velocity is strongly influenced by the wave number, the depth of the irregularity, homogeneity parameter and the rigid boundary. The dimensionless phase velocity is plotted against dimensionless wave number graphically for different size of rectangular irregularities and homogeneity parameter with the help of MATLAB graphical routines for both free and rigid boundaries for several cases. The numerical analysis of dispersion equation indicates that the phase velocity of surface waves decreases with the increase in dimensionless wave number. The obtained results can be useful to the study of geophysical prospecting and understanding the cause and estimating of damage due to earthquakes.Sun, 29 Dec 2019 20:30:00 +0100An Axisymmetric Torsion Problem of an Elastic Layer on a Rigid Circular Base
http://jsm.iau-arak.ac.ir/article_670327_0.html
A solution is presented to a doubly mixed boundary value problem of the torsion of an elastic layer, partially resting on a rigid circular base by a circular rigid punch attached to its surface. This problem is reduced to a system of dual integral equations using the Boussinesq stress functions and the Hankel integral transforms. With the help of the Gegenbauer expansion formula of the Bessel function we get an infinite algebraic system of simultaneous equations for calculating the unknown function of the problem. Both the two contact stresses under the punch and on the lower face of the layer are expressed as appropriate Chebyshev series. The effects of the radius of the disc with the rigid base and the layer thickness on the displacements, contact stresses as well as the shear stress and the stress singularity factor are discussed. A numerical application is also considered with some concluding results.Sat, 04 Jan 2020 20:30:00 +0100Temperature Effect on Mechanical Properties of Top Neck Mollusk Shells Nano-Composite by ...
http://jsm.iau-arak.ac.ir/article_668662_1132799.html
Discovering the mechanical properties of biological composite structures at the Nano-scale is much interesting today. Top Neck mollusk shells are amongst biomaterials Nano-Composite that their layered structures are composed of organic and inorganic materials. Since the Nano indentation process is known as an efficient method to determine mechanical properties like elastic modulus and hardness in small-scale, so, due to some limitation of considering all peripheral parameters; particular simulations of temperature effect on the atomic scale are considerable. The present paper provides a molecular dynamics approach for modeling the Nano-Indentation mechanism with three types of pyramids, cubic and spherical indenters at different temperatures of 173, 273, 300 and 373K. Based on load-indentation depth diagrams and Oliver-Far equations, the findings of the study indicate that results in the weakening bond among the bilateral atoms lead to reduced corresponding harnesses. Whenever, the temperature increases the elastic modulus decrease as well as the related hardness. Moreover, within determining the elastic modulus and hardness, the results obtained from the spherical indenter will have the better consistency with experimental data. This study can be regarded as a novel benchmark study for further researches which tend to consider structural responses of the various Bio-inspired Nano-Composites.Sun, 29 Dec 2019 20:30:00 +0100Clamped-Free Non Homogeneous Magneto Electro Elastic Plate of Polygonal Cross-Sections with ...
http://jsm.iau-arak.ac.ir/article_670324_0.html
In this article, the influence of hydrostatic stress and gravity on a clamped- free non homogeneous magneto electro elastic plate of polygonal cross sections is studied using linear theory of elasticity. The equations of motion based on two-dimensional theory of elasticity are applied under the plane strain assumption of prestressed and gravitated magneto electro elastic plate of polygonal cross-sections composed of non homogeneous isotropic material. The frequency equations are obtained by satisfying the boundary conditions along the irregular surface of the polygonal plate using Fourier expansion collocation method. The complex roots of the frequency equations are obtained by secant method. The numerical computations are carried out for triangular, square, pentagon and hexagon cross sectional plates. Graphical representation is given for the various physical variables via gravity and different edge boundaries and its characteristics are discussed. This result can be applied for optimum design of concrete plates with polygonal cross sections.Sat, 04 Jan 2020 20:30:00 +0100Wave Reflection and Refraction at the Interface of Triclinic and Liquid Medium
http://jsm.iau-arak.ac.ir/article_668914_1132799.html
A Mathematical model has been considered to study the reflection and refraction phenomenon of plane wave at the interface of an isotropic liquid medium and a triclinic (anisotropic) half-space. The incident plane qP wave generates three types of reflected waves namely quasi-P (qP), quasi-SV (qSV) and quasi-SH (qSH) waves in the triclinic medium and one refracted P wave in the isotropic liquid medium. Expression of phase velocities of all the three quasi waves have been calculated. It has been considered that the direction of particle motion is neither parallel nor perpendicular to the direction of propagation in anisotropic medium. Some specific relations have been established between directions of motion and propagation. The expressions for reflection coefficients of qP, qSV, qSH and refracted P waves with respect to incident qP wave are obtained. Numerical computation and graphical representations have been performed for the reflection coefficient of reflected qP, reflected qSV, reflected qSH and refraction coefficient of refracted P wave with incident qP wave.Sun, 29 Dec 2019 20:30:00 +0100A New Numerical Study Method of Thermal Stress Distribution and Tortuosity Effectiveness in an ...
http://jsm.iau-arak.ac.ir/article_670278_0.html
A fuel cell is an electro-chemical tool capable of converting chemical energy into electricity. High operating temperature of solid oxide fuel cell, between 700oC to 1000oC, causes thermal stress. Thermal stress causes gas escape, structure variability and cease operation of the SOFC before its lifetime.The purpose of the current paper is to present a method that predicts the thermal stress distribution in an anisotropic porous anode of planar SOFC. The coupled governing non-linear differential equations, heat transfer, fluid flow, mass transfer, mass continuity, and momentum are solved numerically. A code based on computational fluid dynamics (CFD), computational structural mechanics and finite element method (FEM) is developed and utilized. The code uses the generated data inside the porous anode in order to detect the temperature and the stress distribution using the Darcy’s law and the Navier-Stokes equations. The numerical results used to govern the areas of high values of stresses were higher than the yield strength of materials. The results show that a highest thermal stress occurs at lower corners of the anode. The concentrated temperature occurs at the middle of the electrolyte-anode whereas the maximum pressure occurs at the middle of the upper and lower section of the anode.Wed, 01 Jan 2020 20:30:00 +0100