Papers by Keyword: Laser Shock Processing (LSP)

Abstract: Laser shock processing is a technique similar to shot peening that imparts compressive residual stresses in materials for improved fatigue resistance. Finite element analysis techniques have been applied to predict the residual stresses from Laser shock processing. The purpose of this paper is to investigate of the different sheet thickness interactions on the stress distribution during the laser shock processing of 7050-T7451 aluminum alloy by using the finite element software. The results indicate that the sheet thickness has little effects on the compression stress in the depth of sheet, but great impacts on the reserve side.

Abstract: Laser shock processing (LSP) is a new technique for surface strengthening of fastener holes. The process of LSP before hole-drilling was adopted. A finite element model was established to study the effects of laser shock parameters on the residual stress field of aluminum alloy7050T7451 with Fastener Holes. The results indicate that increasing the laser power density until a fixed value results in a large peak in the hole-edge surface residual compressive stress. The hole-edge surface residual compressive stress and the depth of residual compressive stress are both increased with the increase of laser pulse width. Multiple laser shock processing can improve the residual compressive stress greatly, and with the increasing number of shot, the strengthening effect is gradually diminished.

Abstract: The ultra-high plastic deformation behavior by laser shock processing on the LY12 aluminum alloy had been investigated. The morphology of the materials had been analyzed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). It was found that the grain refinement layer was formed in the thickness of about 100μm .The dislocation density of LY12 aluminum alloy should be large increased after laser shocking because the accumulation of dislocation was appeared on the grain boundary. With the laser energy density increased there formed subgrain structure and eventually generate ultra-fine grain. Hardness test results also show that the surface hardness obtains a big growth about 60% after laser shock processing. The results showed that the formation of ultra-high plastic strain can improve the surface hardness of LY12 aluminum alloy, and thus effectively improve the comprehensive mechanical properties.

Abstract: The strain-rate sensitivity of LY2 aluminum (Al) alloy subjected to laser shock processing (LSP) was investigated according to the fracture morphology at strain-rates ranging from 0.00001 s-1 to 0.1 s-1. The fracture morphology was observed by the scanning electron microscopy (SEM). Fracture morphology at different strain-rates suggested that LY2 Al alloy after LSP seemed to evolve towards a more ductile dimple fracture mode with increasing the strain-rates. The relations underlying the fracture morphology and strain-rate sensitivity were also addressed.

Abstract: Through phrase transformation analysis on ceramics samples after applied laser shock wave, study was made on micro-structure and mechanical performance transformation and transformation laws. Thus conclusions were drawn through analysis as follows: tensile stress was caused on back surface of TZP ceramics sample by laser shock wave, and further transformation was generated under tensile stress in a way that about 48% tetragonal phrases t-ZrO2 transformed into monoclinic phrases m-ZrO2, which expanded volume of and gave rises to micro-cracks, and relief stress and micro-cracks caused will absorb the energy of main cracks, which can impede expansion of main cracks and realize the aim of phrase transformation toughening.

Abstract: Welding residual stress is one of the main factors that affect the strength and life of components. In order to explore the effect on residual stress of welding line by laser shock processing, finite element analysis software ANSYS is used to simulate the welding process, to calculate the distribution of welding residual stress field. On this basis, then AYSYS/LS-DYNA is used to simulate the laser shock processing on welding line. Simulation results show that residual stress distributions of weld region, heat-affected region and matrix by laser shock processing are clearly improved, and the tensile stress of weld region effectively reduce or eliminate. The simulation results and experimental results are generally consistent, it offer reasons for parameter optimization of welding and laser shock processing by finite element analysis software.

Abstract: In this paper, an experiment of fatigue crack propagation in 7050 aluminum alloy was presented. Laser shock processing (LSP) is used to shock the crack surface. Compared with the specimen without LSP, the fatigue life after LSP increased greatly. The simulation of the fatigue crack growth in 7050 aluminum alloy is implemented in FRANC2D. Simulating result is in accordance with the result of the experiment well. Laser shock processing increases the fatigue life and reduce fatigue crack growth rate, it has good prospect on the study of crack arrestment.

Abstract: In the present investigation, the effects of processing parameter on three-point bending fatigue pergormance of TC4 alloy are examined, particular emphasis is devoted to the question of appropriate LSP processing parameters for improving the fatigue properties. Based on cyclic deformation and stress/life (S/N) fatigue behavior, it was found that there was the optimal shock number of overlapped spots for three-point bending fatigue pergormance of TC4 alloy. By comparing with the as-received specimen, the fatigue performance of TC4 alloy has the most obvious improvement by LSP with two impacts.

Abstract: Effects of laser power and spot diameter on residual stress and micro-hardness of the welding of ship plate (ASTM A 131) by laser shock processing (LSP) has been investigated. While laser power is 45.9J, spot diameter less thanφ3 mm, the distribution of residual stress in welding line occurs obvious variation, which residual stress compressive increase obviously with spot diameter decrease. When power density is bigger than 1.2×1010 W/cm2, the surface residual stresses and micro-hardness of the welded specimen occur change by LSP. The results show that mechanical properties of the welded joints will be improved by LSP. Laser shock processing produced a residual compressive stress layer on the surface of the target, which is an effective method for protecting the welded steel structures against stress corrosion.

Abstract: Laser shock processing (LSP, also known as Laser shock peening) is applied by using a high energy pulsed laser to create a high amplitude stress wave or shock wave on the surface to be treated. LSP is proved to be superior to conventional treatments such as shot peening in many engineering products. This paper focuses on Laser shock processing and its effects on mechanical properties of material AISI 8620 alloys steel. Experiment results indicated that compared with base material, the surface hardness increased by 13.8%, and compressive residual stress increased by 521%. Statistical method was introduced to analyze hardness and residual stress change before and after the LSP.