Fretting damage is caused by small relative displacement between two bodies. It can result in loosening of fasteners or fatigue cracks. The traditional mode of fretting fatigue loading is to add a fixed normal load on the fretting pad and a corresponding fatigue load on the free end of the specimen. A new fretting fatigue loading method is proposed to simulate the actual working condition of spline coupling. A 3D finite element model is implemented to simulate the contact state in the process of bending fretting fatigue. The influence of cyclic bending load on the stress and strain of contact surface is studied. The new model is proved to be correct and effective.
The metamaterial with negative Poison’s ratio is widely used due to its special mechanical and physical properties. Based on the theory of periodic solution and bifurcation of nonlinear dynamics, we mainly focus on the nonlinear vibration behaviors and parameter control of a simply supported concave hexagonal composite sandwich plate with negative Poisson’s ratio in auxetic honeycombs subjected to in-plane and transverse excitation. The Melnikov function is improved by introducing the curvilinear coordinate frame and Poincaré map to detect the existence and number of the periodic solutions. The effects of the forcing excitation coefficient on nonlinear dynamics as well as the parameter control conditions are presented. Numerical method is performed to obtain the phase portraits of the number and corresponding positions of multiple periodic orbits.
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