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In this study, the effects of heat treatment of aluminum alloy on the tube bending process were investigated in the rotary draw bending process. As two experimental and numerical simulation methods were used to determine the wall-thinning, ovality, and spring back for extruded, annealed, and aged AA6063 aluminum alloy tubes in different bending angles and bend radii. Numerical simulations were done by the finite element method with Abaqus software. The results indicated that in comparison with annealed and extruded parts, wall-thinning reduced whereas the amount of ovality and spring-back increased in the aged tubes. Also, in each case, the percentage of wall-thinning decreased with increasing bend radius, and the effect of bend radius was greater in the reduction of ovality from the bending angle. Investigations showed that the spring-back rate also decreased with an increasing bending angle.

In this paper, passive and active vortex-induced vibration control of a circular cylinder that oscillates freely in longitudinal and transverse directions is investigated by utilization of nonlinear energy sink. The nonlinear energy sink is composed of a mass, a damping and a nonlinear spring that attaches inside of vibrating cylinder. The vibrational energy of the main cylinder is transferred to the adsorbent mass, thereby reducing the cylinder oscillations. The effectiveness of the proposed control method, numerical results are presented for four Reynolds numbers located in the lock-in region, Re = 85, 90, 95, 100. According to the numerical simulations, the optimized parameters for the passive nonlinear energy sink are considered equal to ... . It can be seen that at all Reynolds numbers, active nonlinear energy sink perform better than passive energy absorbers in reducing vortex-induced vibrations.