فهرست مطالب آرش نعیمی آبکناری

Designing the suspension systems has been investigated as a major challenge to eliminate the undesired effects in the vehicles. Dynamic analysis of a nonlinear six degree of freedom (DOF) suspension is investigated in the present paper. Dynamic equation of motions of the wagon which is consisted of the wagon main body and two bogies were obtained using Lagrange method and then the primary resonance mode frequency response equation under external excitation is derived by solving nonlinear equations through multiple time scale method considering six DOF for wagon vertical movement. A dynamic vibration absorber system is used to passively control and minimizing the primary resonance vibrations of nonlinear system. The frequency response equations of the system were then compared either with or without dynamic absorber. Using a genetic algorithm, which is based on a random driven process, the best performance of the dynamic absorber suspension of the wagon in a six DOF system is investigated. During the process of solving nonlinear equations and optimization, a harmonic input with very small amplitude was assumed as input exerted on one of the wheels.

The wings of projectile is one of the important components for correct controlling and navigation. In this study, in order to consider the vibration behavior of the wing, the governing equations of the opening process of the wing system until collision was derived using analytical method. Also, numerical method using ADAMS software and experimental set up are adopted to compare and verify the analytical analysis. This collision lead to an unwanted excitation of the wing which cause to it vibrates. For decreasing the amplitude of vibration of the wing in better manner, in this research a dynamic absorber is designed and made of Teflon as a damper. The dynamic behavior of the wing with the absorber is studied using analytical and numerical methods and the effect of many parameters such as friction coefficient, material properties of the wing pin and contact area is investigated to optimize its behavior. Obtained results demonstrate that increase in the friction coefficient decrease the returning angle and oscillation amplitude of the wing.

Today, composite material and sandwich plate structures are used more and more due to the unique properties such as a high ratio of strength to weight, corrosion resistance and energy or sound absorption ability. Corrugating sandwich structures is an effective method to reinforce mechanical properties of the composite materials. In this paper, dynamic analysis of these corrugated structures was carried out for a desired performance in the vibratory condition. One of the most important damages in the composite material layers is an inter-layer crack and also the separation between two layers. Vibration analysis of the trapezoidal corrugated sandwich plate was accomplished with ANSYS software using the finite element method. Simulated sandwich plate is a new model of corrugated sandwich plate which has a soft corrugated foam core and a cover of composite layers made from epoxy/glass. In order to validate the vibration behavior of the simulated sandwich plate, the results of experimental modal analysis were compared to the finite element method. The geometry and location effects of inter-layer crack on natural frequencies of the plate were investigated. It was found that with increasing crack dimensions the natural frequencies of the plate decreases and also depth of crack causes decreasing the natural frequencies which are promising results compared to the other references. The changes in vibration characteristics of the sandwich plate can produce comprehensive data to be used in training and designing of the artificial neural network for a promising approach in fault detection and prediction field.