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The New Technologies Developed from Laser Shock Processing
摘要： Laser shock processing (LSP) is an advanced material surface hardening technology that can significantly improve mechanical properties and extend service life by using the stress effect generated by laser-induced plasma shock waves, which has been increasingly applied in the processing fields of metallic materials and alloys. With the rapidly development of modern industry, many new technologies developed from LSP have emerged, which broadens the application of LSP and enriches its technical theory. In this work, the technical theory of LSP was summarized, which consists of the fundamental principle of LSP and the laser-induced plasma shock wave. The new technologies, developed from LSP, are introduced in detail from the aspect of laser shock forming (LSF), warm laser shock processing (WLSP), laser shock marking (LSM) and laser shock imprinting (LSI). The common feature of LSP and these new technologies developed from LSP is the utilization of the laser-generated stress effects rather than the laser thermal effect. LSF is utilized to modify the curvature of metal sheet through the laser-induced high dynamic loading. The material strength and the stability of residual stress and micro-structures by WLSP treatment are higher than that by LSP treatment, due to WLSP combining the advantages of LSP, dynamic strain aging (DSA) and dynamic precipitation (DP). LSM is an effective method to obtain the visualized marks on the surface of metallic materials or alloys, and its critical aspect is the preparation of the absorbing layer with a designed shape and suitable thickness. At the high strain rates induced by LSP, LSI has the ability to complete the direct imprinting over the large-scale ultrasmooth complex 3D nanostructures arrays on the surface of crystalline metals. This work has important reference value and guiding significance for researchers to further understand the LSP theory and the new technologies developed from LSP.
关键词： laser shock processing,stress effect,warm laser shock processing,laser shock marking,laser shock imprinting,laser shock forming
更新于2025-09-23 15:19:57
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Numerical simulation of the surface morphology and residual stress field of IN718 alloy by Gaussian mode laser shock
摘要： Laser shock processing (LSP) is a new surface modification technology that can improve mechanical properties and extending fatigue life. The numerical simulation was utilized in this work, the IN718 alloy was treated by Gaussian mode laser with the laser pulse energy of 3?7 J, laser pulse width of 12 ns and laser spot in diameter of 3 mm. And the effects of laser pulse energy on the surface morphology and residual stress field of material was investigated. The numerical simulation results showed that after the treatment of LSP, the plastic deformation and compressive residual stress layer with a certain depth is formed on the near surface of material. The amount of the plasticity deformation of material was increased with the laser pulse energy. And the compressive residual stress in surface and the direction of depth are increased with the laser pulse energy too. With the laser pulse energy from 3?7 J, the maximum compressive residual stresses are appeared at the center of the surface corresponding to the laser spot. When the laser pulse energy is increased from 3 J–7 J, the plastic deformation in depth is increases from 0.50 μm–1.86 μm, and the maximum compressive residual stress is increased from 362 MPa–742 MPa. In conclusion, LSP can improve mechanical properties of IN718 significantly, and the laser pulse energy is the most important factor to affect the LSP effect. This work can provide a certain theoretical guidance for researchers to study the IN718 alloy treated by LSP.
关键词： Residual stress,Gaussian mode laser,Surface morphology,Laser shock processing,IN718 alloy,Laser pulse energy,Numerical simulation
更新于2025-09-23 15:19:57
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Effect of pulsed laser parameters on deformation inhomogeneity in laser shock incremental forming of pure copper foil
摘要： The dependence of deformation inhomogeneity on the pulsed laser parameters in laser shock incremental forming (LSIF) of pure copper foil was studied based on finite element simulation. The formed depth, angle, profile and limiting fluctuation value were adopted to evaluate the forming deviation of parts. The digital microscope was employed to examine the bottom surface morphology of formed parts. The effect of pulsed laser energy, spot diameter and overlapping rate on the deformation inhomogeneity in LSIF was investigated. It is revealed that there are variances in the shape and dimension of formed parts along both the shock and travelling directions owing to the local loading history of LSIF. The formed depth and angle are different in various positions of formed parts along the shock direction, while the formed profile presents a periodic variation along the travelling direction. The appropriate enhancement of laser energy can improve the deformation inhomogeneity along both the shock and travelling directions. The deformation profiles along the shock and travelling directions depend on the adopted spot diameter. The rebound effect may occur while too small spot diameter is employed, resulting in the degradation of forming accuracy. The overlapping rate has a major impact on the surface morphology of formed parts. As the overlapping rate increases to 80%, the limiting fluctuation values along the travelling direction become large due to the distortion at the free end. Under the given process conditions, the laser energy of 1100 mJ, the spot diameter of 2.5 mm and the overlapping rate of 60% are recommended to achieve straight-line channels with high forming quality.
关键词： Forming quality,Laser parameter,Deformation inhomogeneity,Numerical simulation,Laser shock incremental forming
更新于2025-09-23 15:19:57
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On the application of laser shock peening for retardation of surface fatigue cracks in laser beam-welded AA6056
摘要： The present study aims to investigate the extent to which the fatigue behaviour of laser beam-welded AA6056-T6 butt joints with an already existing crack can be improved through the application of laser shock peening. Ultrasonic testing was utilized for in situ (nondestructive) measurement of fatigue crack growth during the fatigue test. This procedure allowed the preparation of welded specimens with surface fatigue cracks with a depth of approximately 1.2 mm. The precracked specimens showed a 20% reduction in the fatigue limit compared with specimens without cracks in the as-welded condition. Through the application of laser shock peening on the surfaces of the precracked specimens, it was possible to recover the fatigue life to the level of the specimens tested in the as-welded condition. The results of this study show that laser shock peening is a very promising technique to recover the fatigue life of welded joints with surface cracks, which can be detected by nondestructive testing.
关键词： fatigue crack,aluminium alloys,laser beam welding,ultrasonic crack tip diffraction,residual stress,laser shock peening
更新于2025-09-23 15:19:57
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Research on a new laser path of laser shock process
摘要： In most laser shock process experiments, the traditional typical laser path is usually in use. However, the surface residual stress induced by laser shock process distribute unbalance. The residual stress released from the minimum axis, the effective of the laser shock process would lose. To solve it, a new laser path produced, the horizontal and vertical reciprocating (HVR). With the new path, the residual stress distribution unbalance reduced. The laser shock process efficiency improved. The traditional laser path induced stress unbalance produced by the time different between the laser pulse and stress pulse. The stress would overlay to the direction of the laser path, it’s the main reason that the material surface stress distribution unbalance. The laser pulse is 12-20ns for most cases, but the stress pulse is 3 times of it. The results of the simulation shows the traditional laser path X axis stress is 25% larger than the Y axis, but the HVR path is nearly the same. The experiments of the results not only show the two laser path stress distribution different but also the laser shock area different affect the stress distribution. The laser path different affect stress distribution unbalance reason is because the overlay, and the laser shock area affect stress distribution different reason is the resilience.
关键词： laser shock process,laser path,HVR path,residual stress,stress distribution
更新于2025-09-23 15:19:57
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Numerical study of microscale laser bulging based on crystal plasticity
摘要： Microscale laser bulging is an innovative and promising micro metal forming technology and is widely used in the micro electronics industry. With the image-based Voronoi tessellations, the three-dimensional finite element models of disk-shaped polycrystalline aggregates with different initial grain sizes were established to simulate the processes of microscale laser bulging of pure copper foil. The temporal-spatial-distributed laser shock wave pressure was employed to deform the polycrystalline aggregates of pure copper foil. A size-dependent unified constitutive model of crystal plasticity, incorporating the thermally-activated and viscous drag-dominated stages of dislocation motion, was developed and implemented into the finite element codes to describe the plastic deformation behavior at a wide range of strain rates. In the cases of different laser shock wave pressures and initial grain sizes, the predicted maximum bulging heights of pure copper foil are in good agreement with the experimental data, and the resultant thickness and surface roughness also correlate well with the corresponding experiment observations. The simulated equivalent plastic strains and Mises stresses of residual stress components were analyzed by the cross comparisons, and the effect of grain boundary on laser shock wave was further discussed in detail.
关键词： laser shock wave,numerical simulation,polycrystalline aggregates,crystal plasticity,microscale laser bulging
更新于2025-09-23 15:19:57
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Effect of laser shock peening on mechanical and microstructural aspects of 6061-T6 aluminum alloy
摘要： Laser shock peening (LSP) of 6061-T6 aluminum alloy was performed and parametric effects post LSP on mechanical aspects and microstructural evolution are meticulously studied using various means of characterization techniques such as residual stress analysis, surface roughness, Vickers microhardness, tensile testing, X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM) and electron back scattered diffraction (EBSD). Work hardened layer of ~1500 μm depth is obtained with significant improvement in cross-sectional microhardness up to 33.04%. Beneficial compressive residual stress of maximum magnitude up to -273 MPa was induced in laser peened specimens concentrating its overall effect around the depth of 100 μm along the effective depth region. Second phase Mg5Si6 (β?) precipitates were observed post LSP while analyzing XRD profiles along with the peak broadening and peak shifting towards higher 2θ angle justifying the results obtained in microhardness profile. High angle grain boundaries (HAGBs) fraction was increased in LSPed specimens and its effect is noticed in residual stress profile. Mg5Si6 (β?) precipitates are attributed as contributing precipitates in improving the mechanical properties of LSPed specimens along with the dense dislocation density caused by severe plastic deformation during LSP. The collective contribution of strain hardening, second phase precipitates, peak broadening, dislocation density and increased fraction of HAGBs is observed in mechanical and microstructural aspects of LSPed specimens. The results are discussed in detailed and are strongly correlated with each other.
关键词： EBSD,Aluminum alloy,cosα method,TEM,XRD,Laser shock peening
更新于2025-09-23 15:19:57
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Effects of laser shock peening on microstructure and fatigue behavior of Tia??6Ala??4V alloy fabricated via electron beam melting
摘要： Laser shock peening (LSP) is a post-treatment process that is widely used to modify the surface microstructure and mechanical properties of parts constructed by additive manufacturing (AM). In this study, the influence of LSP on the microstructure and fatigue behavior of Ti–6Al–4V alloy manufactured via electron beam melting (EBM), a popular method of AM, was investigated. The microstructure of the EBM sample consisted of the β phase (~6 vol%) and α lamellar phase. Grain refinement of the α phase occurred via both dislocation evolution and deformation twinning during LSP. A theoretical description of the microstructural evolution, particularly the distribution of deformation twins, was developed. The fatigue strength and micro-hardness of the EBM samples increased by approximately 17% and 11% after LSP treatment, respectively. The fatigue fracture morphologies at three defined damage stages (crack initiation, crack propagation, and instantaneous rupture) were examined for EBM samples before and after LSP. The dominant mechanism of fatigue strength enhancement by LSP was discussed. The effects of residual compressive stress assistant with adiabatic temperature increase and grain refinement of the α phase produced by LSP reduced the pre-existing crack size, suppressed crack initiation, and increased the required work for fatigue fracture.
关键词： Laser shock peening,Electron beam melting,Ti–6Al–4V titanium alloy,Fatigue behavior,Microstructural characterization
更新于2025-09-23 15:19:57
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Surface Integrity and Oxidation of a Powder Metallurgy Ni-Based Superalloy Treated by Laser Shock Peening
摘要： Laser shock peening (LSP) is a mechanical surface treatment which can induce large compressive residual stresses and microstructural changes in a material by using repetitive shocks from laser pulses. In this work, the surface integrity (surface microstructure, topography, hardness and residual stress) of a LSP-treated powder metallurgy Ni-based superalloy was investigated for the first time. LSP treatment introduced large plastic deformation especially at a depth of about 100 lm from the surface, which increased the local hardness. The residual stress from the surface to the interior of the sample was investigated by synchrotron x-ray diffraction. The maximum compressive stress reached 400 MPa at the surface, while the depth of the compressive stress is about 0.7 mm. Lastly, the oxidation behavior of the treated and untreated samples was evaluated by thermal exposure at 700°C for 312 h. The LSP treatment decreased the thickness of the oxide layer, thereby showing improved oxidation resistance.
关键词： Oxidation resistance,Surface integrity,Powder metallurgy,Ni-based superalloy,Laser shock peening
更新于2025-09-23 15:19:57
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Atomic Diffusion Behavior and Interface Waveform on the Laser Shock Welding of Aluminum to Nickel
摘要： Atomic diffusion behavior and interface waveform characteristics and formation mechanism during laser shock welding were investigated by using a molecular dynamics (MD) model and smooth particle hydrodynamics (SPH) modeling. The MD simulation showed that the diffusion coef?cient of Al atom was larger than that of the Ni atom. Ni atom is easily diffused deeply into the Al lattice during impact welding. The SPH simulation showed that the wavelength and amplitude of the welding interface increased with loading speed, and SPH simulations at different loading speeds demonstrated that the movement direction of the Ni wave peak is the same as the welding direction, whereas the movement direction of the Al wave peak is opposite to the welding direction. The effective plastic strain and temperature were mainly distributed at the interface waveform. The shear stress of the composite and substrate foil is in opposite direction near the collision point, and the pressure near the collision point was as high as about 10 GPa. Energy-dispersive spectroscopy line scanning analysis showed the presence of a 2.5-lm-thick element diffusion layer at the wavy interface between Al and Ni, verifying the element diffusion between Al and Ni in the MD simulation.
关键词： laser shock welding,molecular dynamics,smoothed particle hydrodynamics,welding characteristics
更新于2025-09-23 15:19:57