مقالات رزومه دکتر مهران کدخدایان

In this work, mechanical vibration analysis of rotating bi-directional functionally graded Euler-Bernoulli nanobeams is investigated, which has not already been studied deeply based on the latest authors’ knowledge. Material properties vary along the thickness and axis directions based on power-law distribution. The nonlocal elasticity theory of Eringen (NET) is utilized for modeling small-scale effects. Different boundary conditions are considered as clamped-clamped (C-C), clamped-simply (C-S), and clamped-free (C-F). Governing equations and associated boundary conditions are derived based on minimum total potential energy, and the generalized differential quadrature (GDQ) method is employed for the solution process. Convergence and verification studies are accomplished to affirm this work, and in the continuation, the effects of various parameters, namely hub ratio, rotation speed, and power indexes along x and z directions on the dimensionless natural frequencies, are investigated. It is revealed that the decrement made by the different values of  in the natural frequency, parameter is more effective than the reduction caused by the , especially for the higher rotation speed.

In this research, two new methods that improve the drawing depth of deep-drawing processes have been introduced. In the first technique, by creating ridges on the punch surface, the stress concentration is decreased on the blank near the punch edge, in turn increasing the drawing depth. The second method is based on the principle of reducing resistant force in the flange area between the die, the blank-holder and the blank that can decrease the required forming energy. By using the ridges on the flange surfaces of die and blank-holder, the contact surface is reduced, which in turn can decrease the force required for blank forming. The simulation results of finite elements are compared to the experimental data. It is found that the ridged punch may delay the blank rupture and significantly raise the drawability.

In this paper, the energy absorption features of tri-layer explosive-welded deep-drawn cups subjected to quasi-static axial compressive loading are investigated numerically and experimentally. To produce the cups, tri-layer blanks composed of aluminum and stainless steel alloys were fabricated by an explosive-welding process and formed by a deep drawing setup. The quasi-static tests were carried out at a rate of 2 mm/min. Based on the structure of the tri-layer cups and to calculate the energy absorption features of these structures, a numerical model was established and validated by experimental findings. Moreover, based on a surrogate model and using non-domain sorting genetic algorithm II, multi-objective optimizations were performed on specific energy absorption and initial peak load. The results indicated that the total absorbed energy and mean crush force of the pure stainless steel tri-layer cup were about 5.8 and 5.7 times the values of those for the pure aluminum specimen, respectively.