Papers by Keyword: Laser Peen Forming

Abstract: The aviation industry demands thin-walled structures of high dimensional accuracy. Varying radii and individual use-cases, e.g. for repair purpose, require flexible forming techniques. Laser peen forming (LPF) represents such a forming process providing precise energy input by a pulsed laser over a wide energy range. Among adjustable parameters such as laser intensity and focus size, the spot shape, i.e. square and circular, is usually fixed for a specific laser system. As the spot shape is a crucial parameter, this work focuses on the effect of the spot shape on structural deformation after LPF application. Therefore, models for laser peen forming of thin-walled Ti-6Al-4V strips for LPF systems with circular and square focus shapes are set up. Geometric conditions on both focus shapes ensure equal energy input during the laser processing. The numerical simulation relies on the so called eigenstrain method, leading to a cost-efficient calculation of resulting deformation after the dynamic LPF process. Square-based peening pattern exhibit higher deflection. For increasing spot size, the deflection difference between square and circle-based patterns increase slightly.

Abstract: In order to study the effect of laser spot superposition on aluminum alloy sheet forming by laser peening, the finite element analysis method was introduced to simulating the forming of 7075 aluminum alloy with different spot superposition case. The results showed that the forming effect and stress distribution of the metal sheet was effected by the laser spot superposition modes. The forming effect of transverse spot superposition mode was better than the other three spot superposition modes.

Abstract: Laser peen forming, is a purely mechanical forming method achieved through the use of laser energy to form metal plate with small curvatures. Experiments were performed to investigate the effect of pre-bending on the plate bending deformation induced by laser peen forming. The pre-bending of plate was accomplished by a fixture with the cambered top surface. The pre-bending curvature radius is calculated and is used to design cambered surface. The LPF experiments are performed with Nd: YAG laser with overlapping laser spots. It is found that the convex deformation can be induced after laser shocks. And its curvature radius in the elastically elongated direction can be greatly increased by applying pre-bending, while in the perpendicular direction, the curvature radius is decreased.

Abstract: Laser peen forming is an emerging novel process of metal plate bending, which uses laser-induced shock wave pressure to generate an unbalanced residual stress field in the target, the moment of the residual stress causes metal plate to develop plastic bending deformation. The mechanism of laser shock induced residual stress was introduced firstly, then the deforming process of metal plate induced by residual stresses was discussed and the depth of the residual compressive stress was proposed. Effects of processing parameters on the residual stress distribution and plate bending deformation were numerical analyzed. The results indicated that the bending deformation of sheet was relative to laser peening numbers, peening coverage and thickness of plate, the magnitude and distribution of residual stresses could be precisely controlled by adjusting laser processing parameters.

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: The principle of laser peen forming (LPF) is introduced, the loading model of laser shock wave is established. This paper focuses on applying finite element analyses, instead of a complicated experimental procedure, to predict the development, magnitude and distribution of residual stresses induced by laser impacts on a metal plate, and dynamic process of laser continuous peen forming is realized with the FEM code ABAQUS. Based on the numerical analysis, the laser processing parameters can be optimized and the deformation contour of metal plate can be analyzed. The results calculated by the finite element method are correlated well with the available experimental results. The simulated results also reveal that adjusting the laser energy appropriately can result in an anticipated shape of plate in LPF process.