This letter presents a thin plate structure with an acoustic black hole (ABH) sub-unit to reorient the flexural wave. Different from the previously reported flexural wave metasurface, ABH sub-units are introduced into thin plates in this work, which can control the group velocity of flexural waves and realize their efficient transmission. According to generalized Snell's law, the mechanism of phase shift of transmitted waves across subwavelength sub-units is theoretically revealed. An analysis of the ABH sub-units is established by the finite element method. The deflection and focusing effect of flexural waves are demonstrated. Furthermore, adjusting the black hole section can quickly obtain the transmission phase response in the range of 2π, and it can accurately predict the phase shift and amplitude of the transmitted wave. The results show that the ABH beam-plate structure can effectively control the propagation direction of flexural waves, which provides a modern design idea and method for the manipulation and energy harvesting of the flexural wave.

Fretting wear phenomenon has a non-negligible impact on the reliability of the contact parts of mechanical power systems. The impact of temperature increases in actual working conditions is taken into consideration in order to increase the accuracy of fretting wear prediction. Temperature-dependent wear coefficients were added to the energy dissipation wear model, and the UMESHMOTION subroutine was created. A temperature-displacement-coupled finite element model of fretting wear is established based on a cylinder/plane fretting test of Ti-6Al-4V alloy materials. The model takes into account the interaction between temperature, stress, and wear. The effects of the plastic deformation of materials, temperature, number of cycles, fretting velocity, and variable normal load on wear and temperature rise are explored. The results show that the wear amount is small when the temperature rises, and the plastic deformation of materials is not considered. The wear profile is no longer a smooth Hertzian shape when the plastic deformation of materials is considered. The amount of wear increases with the fretting speed and the number of cycles. Meanwhile, the temperature of the contact area and the surface near the contact area increases with the increase in fretting speed. Peak temperature rise of the contact surface increases with the number of cycles, and its horizontal position moves with the cylinder specimen. Furthermore, the wear profile is less smooth under the variable normal load, but the two variable normal loads in the same phase have similar wear profiles and temperature rise distributions. The theoretical resources provided by the research work can be used to design control strategies and optimize mechanical power systems.

A large amount of heat is generated during the friction of joint surfaces, which has a significant influence on the contact characteristics of surfaces, causing deformation or failure of key components. A two-dimensional friction-thermal structure coupling contact model of cylinder/plane was established in ABAQUS. The effects of roughness under different fractal parameters, tangential load amplitude and cycle number on the temperature rise distribution of a contact surface under normal cyclic loading were studied. The results show that with the increase of roughness and tangential load amplitude, the area of thermal effect becomes more obvious and the temperature rise of the contact surface increases. It is also found that the heat affected zone is mainly distributed near the surface of the contact area with a high-temperature field generated, while the temperature rise amplitude decreases gradually along the depth direction. In addition, the contact surface nodes have a similar temperature rise distribution process and the farther away from the contact center (x = 0.3 mm), the smaller the temperature rise, which is consistent with the simulation results of the published literature. For the same tangential load amplitude, the surface temperature rise amplitude under the normal cyclic load is lower than that of the normal constant load. The temperature rise of the surface increases with the increase of the number of fretting cycles.