Papers by Keyword: Laser Shot Peening

Abstract: The laser shot peening has the widely application prospect in aircraft structural parts repairment. The influence of laser shot peening parameters on the surface hardness and surface roughness has guiding significance for laser shot peening process. The variation law of surface hardness and surface roughness in the peening area of 7075 aluminum alloy were obtained based on the experiment research. The results show that the surface hardness improves effectively after laser shot peening, and the maximum hardness is 205.4HV, which is improved by 19.49% compared with the original hardness. Besides, the surface roughness of the rough specimen decreases; whereas, those of the smooth specimen increases after laser shot peening. However, both the surface hardness and surface roughness tend to be saturated when the impact times exceeds 3 times or the overlap rate exceeds 50%. Therefore, a good repairment effect can be obtained with 3 impact times and 50% overlap rate for the 7075 aluminum alloy specimen.

Abstract: For comparative study of the influence of laser shock peening and ultrasonic shot peening on the mechanical property of superalloy K403, untreated, ultrasonic shot peening with 850°C heat preservation, laser shock (heat preservation, Hp), the fatigue testing of samples under four states were conducted at room temperature, and the analysis of two techniques’ influence on the mechanical properties of K403 was done by hardness tester, profile tester, scanning electron microscopy (SEM). The results indicated that LSP with Hp, LSP, USP with Hp can improve the fatigue life of K403 respectively for 2.4, 2.25, 1.4 times more longer than untreated sample; the increase of micro-hardness gradient after LSP were smaller than after USP. The SEM studies showed that the γ' phase distortion was elongated and the plastic deformation of samples by LSP was larger than by USP.

Abstract: Based on finite element method, the FEA model used for analyzing fatigue properties of sample treated by laser shot peening (LSP) was established. In order to research the influence of material intensity on LSP effect, two kinds of wrought magnesium alloys AZ31B and ZK60 with different intensity were chosen as object, the compressive residual stress and fatigue life after LSP were analyzed. After spring back analysis the elastic strain is released in material inner, the value of compressive residual stress was reduced; after LSP with 3 times, the fatigue life gains of AZ31B and ZK60 were 105% and 163%, respectively. The results show that strengthening effect of high intensity material treated by LSP is better than that of low intensity material.

Abstract: Residual stress field induced by laser shot peening (LSP) was simulated using Box-Behnken experimental design. Compressive residual stress field intensity (S) was introduced to estimate the effect of compressive residual stress field on fatigue performance. The effect of laser process parameters (such as laser shock wave peak pressure, spot diameter and peening number) on S was analyzed by response surface analysis (RSA), quadratic regression predicting model for S was established, and the rationality of that was verified. Finally, the optimal combination of laser process parameters oriented to anti-fatigue manufacture was optimized. The results indicated statistical analysis results agreed well with those of simulation, RSA for parameter optimization of LSP is feasible.

Abstract: In order to enhance mechanical property and restrain crack growth of 6061-T6 aluminum alloy, laser shot peening (LSP) was employed to induce compressive residual stress and plastic deformation on the surface of metal. The FEA code ABAQUS and MSC. Fatigue were used to simulate crack growth of Compact tension (CT) specimens treated by LSP. The numerical simulation results showed that LSP can effectively inhibit the crack growth, decrease the crack growth rate as well as increase the final crack size, and as a consequence, fatigue life was extended. Adding peening times could get deeper compressive residual stress field which strengthen material surface and restrain crack growth, but the fatigue stress intensity factor threshold decreases.

Abstract: Laser shot peening (LSP) has recently received more and more attention as a viable laser processing technology, since it can obtain the desirable residual compressive stress to improve fatigue life of the material by precisely controlling laser parameters. The purpose of this paper is mainly to explore the optimal residual compressive stress in the surface layer during LSP by statistical optimization algorithm. Based on the finite element analysis software ANSYS, Multi-island Genetic Algorithm (MIGA) is adopted to find the best solution of design requirements, the control parameters are laser pulse energy and spot diameter, while the aim parameters are residual compressive stress and deformation values, respectively. The results indicate that the optimal residual compressive stress obtained by integrated optimization technique can significantly improve the mechanical properties of the target after LSP. It provides a guiding importance for parameters optimization in future experimental research and practical application.

Abstract: A numerical analytical model for both-side laser shot peening (LSP) of specimen with center-hole was established, the influence of the center-hole on peening effect was investigated, and the 3D residual stress distributions of ZK60 specimen after one-side and both-side LSP were analyzed. The results showed that compressive residual stresses were obtained at the both sides of specimen after both-side LSP, with a stress value of -179.41MPa on the bottom surface, much larger than that of one-side LSP. The typical experiment of LSP for ZK60 specimen was carried out and the experimental data were well correlated with the simulated results.

Abstract: Numerical study on fatigue life of ZK60 magnesium alloy plate before and after laser shot peening (LSP) was carried out in this paper. Based on the FEA model, residual stress field induced by LSP was analyzed, the fatigue life and position of weak area were predicted with ABAQUS software and MSC.Fatigue code, respectively, and the processing parameters were optimized. The results show that the fatigue life of ZK60 sheet metal by single LSP with one side and both sides increased by 72.9% and 78.5% compared with the untreated sample respectively. The size and depth of compressive residual stress increase with the increment of peening number, but when the peening number gets to a certain value, the residual stress reaches saturation and the fatigue life increase no longer significantly.

Abstract: The laser peen forming (LPF) uses high-power pulsed laser beam replacing the tiny medium balls to peen the surface of plate and generate compressive stress near the surface, the metals respond to this residual stresses by elongating at the peened surface and effectively bend the overall shape. In this paper, the deforming process of metal plate induced by repetitive pulsed laser was discussed from theory firstly, and the bending mechanism of LPF was investigated. Then a mathematical model of bending curvature concerning the depth of residual stress was presented, the influence of residual stresses on the deformation of plate was analyzed. Lastly, the line-track-peening experiment for SUS 304 plate was carried out to evaluate the reasonability of the theoretical analysis model.

Abstract: Laser shot peen-forming of sheet metal(or LasershotSM Peening) is a new plastic forming technique for metallic materials, which uses high-power pulsed laser replacing the tiny balls to peen the surface of sheet metal. When the pressure of shock waves induced by laser impresses an inhomogeneous residual stresses distribution in a given depth on the surface of sheet, it responds to the stress by elongating at the peened surface and effectively bending the sheet. In order to investigate the mechanism of laser shot peen-forming, the narrow strip peen-forming experimental of aluminum alloy 6061-T6 was carried out by using a pulsed Nd:glass laser with 0.5Hz repetition-rate. Here, under some given laser energy, laser pulse width, laser beam diameter and pulse repetition frequency and so on, the influence of shot strip interval and shot times on surface residual stresses and the deformation of the sheet is analyzed. The results show that the bending forming of the sheet metal can be found, and the peened surface of sheet metal becomes convex. That the bending increases with shot strip interval increase is not obvious, but it increases with the shot times increase in a proper range of shot times. Besides, because laser shot peen-forming generates compressive residual stresses on the surface, it offers many desirable characteristics in shaped metals and is a valuable technique for producing components for a range of industries.