Papers by Author: Deng Hui Wei

Abstract: Micro-scale laser shock peening (μLSP) is a flexible and precise process that can potentially be applied to metallic structures in micro devices to improve strength and reliability performance. In order to understand the mechanism of μLSP process, a typical experiment was carried out for copper foils specimen with various process parameters. Surface morphology, deformation and hardness of the specimens were observed and characterized by 3D microscope system and situ nano-mechanical test system respectively. It was found that overlapping rate of laser spot has a little effect on microscopic deformation depth which increases slowly with the increasing of laser energy, and micro-hardness of the laser treated specimens was improved significantly.

Abstract: Microscale laser shock peening (μLSP) can generate beneficial compressive stress distribution in the targets, as the used beam diameter in μLSP is at the order of micron equivalent with grain size, the treated material must be considered as anisotropic and inhomogeneous, this causes an asymmetrical distribution of residual stress. In this paper, shape factor σSF was introduced and defined to characterize the asymmetrical distribution of stress, optimum conditions of factors and the influence degree were explored based on Taguchi design with the optimal object of stress characterization values. The results show that shape factor is a significant characteristic of residual stress induced by μLSP, crystal orientation is the most important influence factor, but laser energy and peening number have significant influence on stress characterization values.

Abstract: After the mechanisms of laser peen forming (LPF) were analyzed, the effect of sheet metal’s thickness on LPF was discussed in theory. The analysis model that residual stresses brought sheet bending was established, and the relationship between thickness and arc height of sheet metal was obtained. The process of laser shock wave loading during LPF was modeled, and then the residual stresses and deformation of the peened sheet were simulated by ABAQUS software. The results indicated that LPF use bending moments caused by residual stress to induce deformation, which was agreed with the theory analysis. The curvature of sheet metal induced by LPF decreased as the thickness increased, the arc height formed by bending was inversely proportional to thickness square of sheet metal on the whole. This research also has significance for the control of LPF and the investigation of further experiment

Abstract: Micro-scale laser shock peening (μLSP) is a novel surface modification technique utilizing mechanical effect of shock wave induced by high intensity pulsed laser with micron spots. μLSP can introduce the beneficial residual compressive stress distribution in surface layers of metal with micron-level spatial resolution, and thus enhance wear resistance and fatigue performances of metallic micro-structures. The characteristics and influence factors of μLSP were briefly introduced, and progress in μLSP research fields was reviewed and presented, including laser induced shock pressure, material constitutive relation, changes of mechanical properties and microstructure evolution of materials. Finally, proposals on further investigations of μLSP were brought forward. The systematical characterization will lay the ground work for better understanding the effect of μLSP in microlength level and developing a more practical simulation method.