Tribological study of piston–cylinder interface of radial piston pump in high-pressure common rail system considering surface topography effect

Based on the theory of thermal fluid dynamic lubrication, the Reynolds equation and energy equation of the average flow of a piston–cylinder interface of a radial piston pump in a high-pressure common rail system are established, considering the surface topography effect. The tribological properties of the piston–cylinder interface are calculated by solving the Reynolds equation and energy equation. A surface wear model is established and the wear distribution and trend of the piston–cylinder interface are studied. The wear characteristics of the piston–cylinder interface are verified through experiment, and the wear lubrication of the piston–cylinder interface is discussed. The surface topography effect has a considerable influence on the characteristics of the piston–cylinder interface film. Different surface morphologies change the film characteristics of the piston–cylinder interface, yielding different wear behaviors on the mating surface. The wear of the piston–cylinder interface first decreases along the film outlet to the inlet and then rises. The cylinder surface mainly exhibits abrasive, cavitation, and micro-convex scratch wear, whereas the piston surface mainly shows cavitation wear. The results obtained in this study are of considerable significance as they reveal the tribological properties of the piston–cylinder interface under the surface topography effect.

Oblique Incidence of Seismic Wave Reflecting Two Components of Design Ground Motion

The wave field on the artificial boundary was separated into the free field without local topography effect and scattering field induced by local topography effect. The simulation of the free field under obliquely incident waves was conducted. Based on the assumption that the components of design ground motion were treated as the coincidence of oblique P wave and oblique SV wave, the relationship between the oblique input waves and the design ground motion was established in the free field. Further, the contributions to the two components of design ground motion of obliquely incident waves were discussed. The calculation model in time domain was achieved by the combination of the propagation characteristics of obliquely incident waves and the artificial boundary in the free field. The seismic response to the design ground motion was produced on the free surface. The verification of the 2D half-space model under oblique input waves indicated that the wave input method can accurately reflect the design ground motion on the free surface. Application of an earth-rock dam showed that oblique incidence of seismic waves results in significantly different dynamic response compared with the normal incidence. The proposed method can also be employed in the seismic analysis of large span structures with nonuniform ground motion input.