JOURNAL OF SIMULATION AND ANALYSIS OF NOVEL TECHNOLOGIES IN MECHANICAL ENGINEERING (JOURNAL OF SOLID MECHANICS IN ENGINEERING)
Year:2012 | Volume:5 | Issue:1 (11)|Papers Count:6

In the present study the effect of phase volume fraction of reinforcement on microstructure and tensile properties of composite extrusion process Al6061/SiC has been studied. For this purpose, the base alloy Al6061 using pure aluminum ingots, silicon, of Al-50% Mg, Al-10% Cr and a thin copper rod was prepared. Next, the composite Al6061/5% SiC, Al6061/10% SiC, Al6061/15% SiC and Al6061/20% SiC through the addition of various amounts of silicon carbide particles was prepared by cast stirring. Composite samples containing different volume fractions of the reinforcing SiC, hot extrusion operation was performed. Evaluation of microstructure using light and electron microscope was performed. During the study, it is shown that with increasing amount of reinforcement, porosity and pores in the microstructure is increased. The extrusion process reduces the amount of porosity as well as creating fine reinforcement. In order to investigate effect of extrusion process on the mechanical properties composite, tensile test were used. the results showed that, with increasing SiC up to 5 by weight percent, it will increased ultimate tensile strength of composite. In addition, it is shown that extrusion process will result particles homogenous distribution which in turn the tensile stress were improved.

In this paper, effect of elastic foundation on out of plane displacement of functionally graded circular plates using differential transform method is presented. Differential transform method is a semi-analytical-numerical solution technique that is capable to solve various types of differential equations. Using this method, governing differential equations are transformed into recursive relations and boundary conditions are changed into algebraic equations. Since the problem of plates on elastic foundation have a great practical importance in modern engineering structures and Winkler foundation model is widely used, plate is assumed on Winkler elastic foundation. In this article functionally graded plate is considered in which material properties vary through the thickness direction by power-law distribution. Analysis results of out of plane displacement of plate on elastic foundation under uniform transverse load are obtained in different terms of foundation stiffness, material properties and boundary conditions. To illustrate correctness and accuracy of the solution technique, obtained results are compared with the results of the finite element method (FEM).

In shot peening process the work piece surface is struck by a large number of balls and compressive residual stress is generated on the surface. So, mechanical properties such as fatigue strength, stress corrosion resistance, smooth shape and. .. will improve. In this paper, the balls with a speed of 100 to 200 m/s were struck on the steel samples and fatigue strength compared with specimens without shot peening. The results included a significant increase in fatigue strength. Also the balls deep changes in the samples were calculated by the software ANSYS and compared with experimental results. The results show that, if the ball speed is 100 m/s, it leads 25% increase in fatigue strength while the residual stress will increase to 250 MPa. Furthermore, if the ball speed is 200 m/s, fatigue strength and residual stress increase up to 40% and 300 MPa, respectively. It is also concluded that the stress in the balls is twice the work piece surface residual stress.

Actual applications of the energy absorbers show that actual loads are not applied in the form of pure axial compression, pure bending or pure torsion. In reality, an energy absorber component may be subjected to combined loading of compression, bending and torsion. A few previous articles have investigated the behavior of energy absorbers under oblique loading. In such works, the oblique load was considered as 2D load determined with one angle parameter to the profile of specimen. However, in reality, it is possible that the energy absorber component be under a 3D oblique load whit three spatial components determined by two angle parameter in 3D space. In current article, crashworthiness behavior of thin walled tubes is experimentally analyzed under 3D oblique load. To this respect, a fixture was designed and installed on universal tensile and compression testing machine. All tests were conducted in quasi-static form and finally a diagram of force and displacement and crushing modes were extracted and the effect of oblique load aspects on energy absorbing characteristics was investigated.

Semi-solid forming processes are now used for producing near net shape parts especially in automotive and aircraft industries. Non Newtonian rheology of semisolid alloys and its dependence on various parameters such as reheating cycle, method used to produce non-dendritic structure, thermo-shear history and etc. have made the simulation of the flow behavior of semisolid material a difficult mater in engineering. One of the semi-solid forming processes is thixoforging process. Thixoforming takes place between liquidous and solidous temperature and liquid phase and solid one exist at the same time. The significant parameters in this method can be strain rate, friction and temperature terms. In this research, the simulation of thixoforging process is done with Deform-3D software on the friction factor, process temperature and rams speeds. In order to verify the model, thixoforging tests were conducted with various parameters and under isothermal conditions on the A356 Alloy. The comparison of numerical results at the different solid fractions with experimental data is shown that, these simulations can provide an accurate model of the process. Also the simulation results had shown the effects of all parameters. The results showed that by increasing mould temperature, causes more inhomogeneous microstructure and therefore the hardness and forming force decreased %12.5 and %20.6 respectively.

In the past few years, extensive improvements have been accomplished in reinforcing the structures through using shape memory alloys (SMAs). These materials absorb or dissipate energy through establishing a reversible hysteresis loop during a cyclic mechanical loading. This unique characteristic of the SMAs has made them appropriate for sensing, actuation, absorbing the impact energy, andvibration damping applications. Instantaneous and local variations of the phases of the SMA wire in the successive loading and unloading events of the vibration have not been accurately investigated by the workspublished thus far. In the present paper, vibrations of composite plates reinforced by SMA wires are investigated, employing an algorithm that overcomes the mentioned shortcomings. Governing equations are derived based on Hamilton’s principle and the first-order shear-deformation plate theory. Furthermore, Brinson’s constitutive equations are used to model material properties of the SMA and the time-dependent partial deferential equations are solved using Newmark’s numericaltime integration method. The governing equations are solved by a finite element code written in MATLA software. In the present research, influence of the instantaneous variations of the volume fraction of the martensitevolume fraction due to variations of the stress components on the material properties of the SMA, hybrid composite, and the recovery load is considered for the first time. Finally, effect of the volume fraction of the SMA wires of each layer and influence of the amplitude of the abruptly applied load on vibration behavior of the composite plate is investigated, too.