Sharif Digital Repository

Three deformation routes for recently invented severe plastic deformation (SPD) method named tube channel pressing (TCP) have been introduced in this paper. The effects of routes, back pressure and friction have been investigated on deformation behavior of commercially pure (CP) aluminum tubes. Utilizing finite element analysis provides a broader understanding of these effects through different deformation routes. Due to the large values of strains accumulated in TCP, modified Estrin-Tóth-Molinari-Brechet (METMB) constitutive model has been employed in finite element analysis program to consider a realistic flow stress of the material in TCP. Employing experimental procedures confirms the... 

Stabilization of slopes is considered as the aim of the several geotechnical applications such as embankment, tunnel, highway, building and railway and dam. Therefore, evaluation and precise prediction of the factor of safety (FoS) of slopes can be useful in designing these important structures. This research is carried out to evaluate the ability of Monte Carlo (MC) technique for the forecasting the FoS of many homogenous slopes in the static condition. Moreover, the sensitivity of the FoS on the effective parameters was identified. To do this, the most important factors on FoS, such as angle of internal friction (Formula presented.), slope angle (Formula presented.) and cohesion (Formula... 

Stabilization of slopes is considered as the aim of the several geotechnical applications such as embankment, tunnel, highway, building and railway and dam. Therefore, evaluation and precise prediction of the factor of safety (FoS) of slopes can be useful in designing these important structures. This research is carried out to evaluate the ability of Monte Carlo (MC) technique for the forecasting the FoS of many homogenous slopes in the static condition. Moreover, the sensitivity of the FoS on the effective parameters was identified. To do this, the most important factors on FoS, such as angle of internal friction (∅) , slope angle (α) and cohesion (C) were investigated and used as the... 

The behavior of hot extruded Al-6Mg during hot deformation has been studied using hot compression test. The tests were performed at temperatures of 350, 450, and 550°C and strain rates of 0.001, 0.1, and 1s -1. Due to the effects of friction and adiabatic heating generated during compression, the attained true stress-true strain curves have been corrected. After correction of friction effect, the virtual work hardening has been removed from stress-strain curves. The flow stress increases and reaches a steady state after correction of adiabatic heating effect. Corrected curves and microstructural examinations exhibit the occurrence of dynamic recovery during hot compression of the alloy. The... 

In this study, a general methodology has been developed to design the proper bearing in order to eliminate the curvature of the final product in extrusion process. Three smooth curved (advanced-surface) dies with non-symmetric T-shaped sections and different off-centricities have been studied. For each die, the proper bearing has been designed and physical and numerical modeling have been performed to validate the design. The design procedure is as follows: A formulation, based on Bezier curves, has been used to determine the exit velocity profile. Since the result of Bezier method is different from the actual velocity profile, the Chitkara corrective function has been modified and applied... 

In this paper, the stick-slip motion of a microrobot with two perpendicular vibrational actuators is studied. This motion is based on the friction drive principle. To determine the effective parameters in the motion of microrobot, the equations of motion of the microrobot are derived. To simplify the equations for determining the design parameters, the vibrational actuators are modeled with two perpendicular harmonic forces. To study the motion dynamics of the microrobot, its equation of motion is derived in a nondimensional expression by defining the nondimensional effective parameters. The Fourier expansion (F.E.) method is used to analyze the numerical results and it showed some...