GRAIN BOUNDARY RESPONSE OF ALUMINUM BICRYSTAL UNDER MICRO SCALE LASER SHOCK PEENING

摘要

Micro scale laser shock peening (μLSP) is a process in which compressive residual stresses are induced in a material surface to improve fatigue life and wear resistance under cyclic loading. Since the diameter of the laser spot used during the process is the same order of magnitude as grain size, the effects of anisotropy and heterogeneity have to be explicitly taken into account. In this study experimental and analytic work have been done in order to investigate the bicrystal aluminum response under Gaussian loading. Effects of heterogeneity under μLSP are studied through applying laser shocks onto the grain boundary of the aluminum bicrystal. μLSP on reference single crystals have also been performed for the purpose of comparison. The orientations of the crystals in the bicrystal as well as the reference single crystals have been chosen such that an approximate plane strain condition is achieved. A finite element model has also been developed based on single crystal micromechanics and a cohesive zone interface model. Simulation results are compared with experimental findings. The potential benefit of μLSP as a surface treatment for improvement of fatigue life is also discussed.