冲击波传播方式对激光冲击7050铝合金残余应力分布的影响
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摘要
目的针对高斯光冲击下,冲击波传播方式对激光冲击7050铝合金残余应力分布的影响,调节参数以获得材料表面良好的力学性能。方法通过改变激光光斑直径,借助有限元软件ABAQUS,分别模拟了球面波、平面波传播方式对7050铝合金残余应力分布的影响,并借助X射线衍射残余应力仪对模拟结果进行验证。结果当冲击压力为2 GPa时,光斑直径为2 mm呈球面波,光斑直径为4 mm呈平面波。变化冲击压力能够改变冲击波在材料内部的传播形式,当冲击峰值为2 GPa时,3 mm光斑由球面波向平面波转变,冲击压力达到3 GPa时,完全转化为平面波。球面波对表面残余应力、深度方向残余应力的影响均较平面波小,影响层深差为50μm。模拟结果与测试结果误差在15%以内,具有较好的一致性。结论采用3 mm光斑进行冲击时,合理利用冲击压力对传播方式的影响能够获得较同样条件下平顶光冲击时更均匀的表面应力分布,其影响层深及最大残余应力情况与平顶光冲击时的差异较小。
The work aims to adjust parameters to obtain good mechanical properties of material surface in view of the effect of laser shock wave propagation mode on the residual stress distribution of 7050 aluminum alloy under the Gaussian laser. The finite element software ABAQUS was used to simulate the effect of spherical wave and plane wave on residual stress distribution of 7050 aluminum alloy by changing the diameter of laser spot. X ray residual stress detector was used to verify the simulation results. When the shock pressure was 2 GPa, the spot diameter was 2 mm with spherical wave, and the spot diameter was 4 mm with plane wave. The shock pressure could change the propagation mode of the shock wave in the material. When the shock peak is 2 GPa, the spot with a diameter of 3 mm changed from spherical wave to plane wave, and when the shock pressure reached 3 GPa, the spherical wave completely transformed into plane wave. The effect of spherical wave on surface residual stress and residual stress in depth direction was smaller than that of plane wave, and the depth difference was 50 μm. The error between simulation results and test results was less than 15%, and the results are in good agreement. When 3 mm spot is used for shock, more uniform surface stress distribution can be obtained by reasonable use of the shock pressure on the propagation mode than that under the same conditions of flat-top laser, and the difference of the depth of the affected layer and the maximum residual stress is small.
The work aims to adjust parameters to obtain good mechanical properties of material surface in view of the effect of laser shock wave propagation mode on the residual stress distribution of 7050 aluminum alloy under the Gaussian laser. The finite element software ABAQUS was used to simulate the effect of spherical wave and plane wave on residual stress distribution of 7050 aluminum alloy by changing the diameter of laser spot. X ray residual stress detector was used to verify the simulation results. When the shock pressure was 2 GPa, the spot diameter was 2 mm with spherical wave, and the spot diameter was 4 mm with plane wave. The shock pressure could change the propagation mode of the shock wave in the material. When the shock peak is 2 GPa, the spot with a diameter of 3 mm changed from spherical wave to plane wave, and when the shock pressure reached 3 GPa, the spherical wave completely transformed into plane wave. The effect of spherical wave on surface residual stress and residual stress in depth direction was smaller than that of plane wave, and the depth difference was 50 μm. The error between simulation results and test results was less than 15%, and the results are in good agreement. When 3 mm spot is used for shock, more uniform surface stress distribution can be obtained by reasonable use of the shock pressure on the propagation mode than that under the same conditions of flat-top laser, and the difference of the depth of the affected layer and the maximum residual stress is small.
引文
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[2]PEYRE P,FABBRO R.Laser shock processing:a review of the physics and applications[J].Optical&quantum electronics,1995,27(12):1213-1229.
[3]余天宇,戴峰泽,张永康,等.平顶光束激光冲击2024铝合金诱导残余应力场的模拟与实验[J].中国激光,2012,39(10):25-31.YU Tian-yu,DAI Feng-ze,ZHANG Yong-kang,et al.Simulation and experimental study on residual stress field of 2024 aluminum alloy induced by flat-top laser beam[J].Chinese journal of lasers,2012,39(10):25-31.
[4]FABBRO R,FOURNIER J,BALLARD P,et al.Physical study of laser-produced plasma in confined geometry[J].Journal of applied physics,1990,68(2):775-784.
[5]JOHNSON J N,ROHDE R W.Dynamic deformation twinning in shock-loaded iron[J].Journal of applied physics,1971,42(11):4171-4182.
[6]FABBRO R,PEYRE P,BERTHE L,et al.Physics and applications of laser-shock processing[J].Journal of laser applications,1998,10(6):155-164.
[7]BALLARD P,FOURNIER J,FABBRO R.Residual stresses induced by laser-shocks[J].Journal de physique IV,1991,1:C3-487.
[8]李应红.激光冲击强化理论与技术[M].北京:科学出版社,2013.LI Ying-hong.Theory and technology of laser shock processing[M].Beijing:Science Press,2013.
[9]PEREIRA P,SANTOS A A.Influence of anisotropy generated by rolling on the stress measurement by ultrasound in7050 T7451 aluminum[J].Experimental mechanics,2013,53(3):415-425.
[10]LIU Q C.An effective extension technology for 7xxx series aluminum alloys by laser shock peening[M].Sydney:Australian Government Department of Defence,2008.
[11]FAN Y,WANG Y,VUKELIC S,et al.Wave-solid interactions in laser-shock-induced deformation processes[J].Journal of applied physics,2005,98(10):461-192.
[12]PEYRE P,FABBRO R,MERRIEN P,et al.Laser shock processing of aluminum alloys.applications to high cycle fatigue behavior[J].Materials science&engineering A,1996,210(1-2):102-113.
[13]ZHENG C,ZHANG X,ZHANG Y,et al.Effects of laser power density and initial grain size in laser shock punching of pure copper foil[J].Optics&lasers in engineering,2018,105:35-42.
[14]REN X D,ZHOU W F,REN Y P,et al.Dislocation evolution and properties enhancement of GH2036 by laser shock processing:Dislocation dynamics simulation and experiment[J].Materials science&engineering A,2016,654:184-192.