Engineering practices have indicated that surface textures and topography greatly affect the mechanical performance of contact interfaces. The effect of machined surface morphologies on the contact performance results, including average surface gap, contact area ratio, and the volume of plastically deformed material, is investigated. Depending on the machined parameters, the studied surfaces are generated using computer simulation. The elasto-plastic contact of rough surfaces is analyzed by means of semi-analytical method (SAM) and minimization of complementary energy. Results indicate that with increasing the interval of texture, average surface gap remains invariant while contact area ratio and the volume of plastically deformed material decreases.

When the load acting on a mechanical structure is greater than the yield strength of the material, the contact surface will undergo plastic deformation. Cumulative plastic deformation has an important influence on the lifespan of mechanical parts. This article presents a three-dimensional semi-analytical model based on the conjugate gradient method and fast Fourier transform algorithm, with the aim of studying the characteristic parameters of the contact region between a rigid ellipsoid and elasto-plastic half-space. Moreover, normal forces and tangential traction were considered, as well as the contact pressure resulting from various sliding speeds and friction coefficients. The contact pressure, effective plastic strain, von Mises stress, and residual stress were measured and shown to increase with increasing sliding velocity. Finally, when the friction coefficient, contact pressure, and effective plastic strain are increased, the von Mises stress is also shown to increase, whereas the residual stress decreases.

Helical tube steam generators are often used in nuclear power plants because of their compact structure and high heat transfer efficiency. The impact of the internal fluid causes the vibration of the tube bundle, which leads to the failure of the integrity of the safety structure. Aiming at flow-induced vibration (FIV) of helical tube arrays, a finite element model of the helical tube was established to consider the constraint of the support structure. The computational fluid dynamics (CFD)/computational structural dynamics (CSD) coupling calculation method based on the superposition of three modes was used to study the FIV characteristics of helical tube arrays at different flow velocities. The influence of adjacent helical tubes’ vibration on the vibration of the target tube was also investigated. The results show that when FIV occurs in the helical tube, with the increase of inlet velocity, the axial amplitude will be greater than the radial at the same velocity. When some tubes vibrate, the vibration of the target tube will be enhanced; while adjacent tubes vibrate, it will weaken the impact of the fluid on the target tube and obviously weaken the vibration of the target tube.

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