جستجوی مقالات مرتبط با کلیدواژه « Finite Element Method » در نشریات گروه « مکانیک »

Composite materials are of great interest due to their exceptional strength, hardness-to-density ratio, high corrosion resistance, and low weight. One of the suitable methods for making composite pipes is using the extrusion process. Extrusion is a plastic deformation process that due to the compressive state of stress in extrusion, materials with low plasticity can be formed by this method. This article deals with the experimental-numerical investigation of extrusion, from various methods of forming process. Extrusion is done on a composite tube using aluminum and magnesium alloys. Aluminum is used due to its strength compared to high weight, excellent malleability, and magnesium due to the lightest structural metal, the lowest density among structural materials, machining, welding and casting capabilities, as well as high specific strength. The mentioned process was tested at different extrusion ratio, temperature and speed, and the effect of different process parameters on the properties of the extruded product was investigated. Then the process was simulated in the software and the experimental results obtained from the laboratory work and the numerical results obtained from the simulation were compared and validated with each other and the error percentage between the graphs of the experimental and numerical results was examined.

In this study, an analytical solution has been developed to examine the mechanical behavior of an incompressible functionally graded hyperelastic cylinder subjected to simultaneous extension and torsion. The recently proposed exp-exp strain energy density is employed to predict the behavior of hyperelastic material, and its related material parameters are assumed to vary along the radial direction in an exponential fashion. Finite element analysis is conducted by preparing a user-defined UHYPER subroutine in ABAQUS to evaluate the proposed analytical solutions. FEM results and those of the analytical solution are in good agreement for various stretches and twists and reveal that the form of stress distributions and the maximum stress depend on the exponential power in the material variation function. In contrast to axial stretch, the effect of twist on the distribution of longitudinal stress is more complicated, and for large twists, two extrema in the stress distribution plot are observed, which move toward the center and outer surface of the cylinder on further twisting. Moreover, the longitudinal stress controls the variation of von-Mises and strain energy density throughout the radial direction. Additionally, considering an axial stretch, a point is identified where the axial force arising from torsion is compressive for stretches below this value, and it brings about the cylinder to elongate under twisting. However, this part of the total axial force varies from a tension state to a compression one for larger stretches, i.e., by increasing the twist, the cylinder first tends to shorten and then elongates on further twisting.

Ionic Polymer-Metal Composite (IPMC) strips are very thin actuators in the form of a sandwich composite with an electroactive polymer in the core and two metal electrodes on its sides. In this paper, a multi-scale electrochemical-mechanical analysis of actuation time response of an IPMC composite strip is performed. First, the electrochemical response of IPMC primary motion stemming from electrostatic force, viscous force of ionic cluster motion in the polymer matrix solvent, and diffusive force caused by the concentration potential are obtained by a hydraulic model. The solution methods in the space domain include finite element numerical analysis based on Glerkin's formulation, and Euler's integration method in the time domain. Then, the solvent transport equation is written, and the rate of eigen strain and bending moment of the IPMC actuator is obtained. By extracting the amount of cluster concentration in the boundary layer of cathode and anode, the displacement response of the end of the beam is determined. The results of the model are validated with previous available studies. The results show a reasonable fit between the response of the IPMC actuator and the electrical excitation, and confirm that the presented model provides the prediction of the fast response of IPMC strip.

the one-of-a-kind properties of series 7xxx aluminum alloys such as high strength, relatively low density, good formability, and good resistance to stress corrosion cracking have made this class of materials a good choice for aerospace, automobile, and marine industries. Watertight, low weight, and fast procedure are the reason why welding is used in many industries. The heat that welding produce causes many problems like softening in the heat-affected zone. In this research with the use of a 3-D finite element model, the heat transfer of the Al-7075-T6 is investigated and verified by comparing them with the experimental model and the reduction of hardness in the heat-affected zone of the aluminum was predicted with good precision. In the next step, the softening of HAZ due to welding was measured with microhardness. With the use of the FEM model kinetic of over-aging was measured. The results show hardness of the alloy has two sources i.e. age-hardening and work-hardening. It seems welding eliminates the effects of age-hardening but has no effect on the hardness that comes from work hardening. Also, the decrease in the hardness of the solution-annealed area can be recovered through proper heat treatment. However, it is unrecoverable in the over-aged area.

Heart diseases are one of the most important causes of death in the world, and their treatment is very important from a medical and financial perspective. One of the effective ways that can be very useful in the treatment of cardiovascular diseases is computational modeling which can help medical professionals to better understand the human heart and provide more effective therapeutic approaches. The mechanical characteristics of the myocardium of human heart, known as a nonlinear and anisotropic tissue, are the most important part of the heart because it plays a key role in myocardial response to loading and unloading during heart cycle. In this study, the orthotropic hyperelastic and isotropic viscoelastic properties of the human heart were modeled by taking into account the effect of active stress on myocardium and using an idealized left ventricular geometry. Simulation results showed that the viscoelastic property cause the myocardium deformation to be damped and reduces the amount of torsion that experienced by the tissue. Also, myocardium tissue in viscoelastic case showed the hysteresis phenomenon which is found in clinical observations of heart mechanics. The Model is entirely implemented in COMSOL Multiphysics finite element software and can be used in heart electromechanical models in future studies.