激光冲击参数对7050铝合金残余应力场的影响

Effect of laser shocking parameters on residual stress field of 7050 aluminium alloy

采用仿真与试验结合的方法,研究了激光冲击参数(光斑直径、激光特性以及峰值压力)对7050合金残余应力场形成机制的影响。结果表明:平顶光加载φ2、φ3和φ4 mm光斑时,最优峰值压力为1500 MPa;高斯光加载时,φ2 mm光斑峰值压力优解为1500 MPa,φ3 mm光斑峰值压力优解为2000 MPa,φ4 mm光斑峰值压力优解为3000 MPa;当峰值压力为1500 MPa时,平顶光冲击后所得最大残余压应力较高斯光增加约10%;当峰值压力大于2000 MPa时,平顶光冲击后的最大残余压应力值受表面汇聚波影响数值较高斯光小。平顶光冲击时,峰值压力实际优解与理论优解保持一致,为1500 MPa;高斯光冲击时,峰值压力实际优解随光斑直径的增加逐渐增加;峰值压力超过2000 MPa后,残余压应力不再有显著增加,且残余应力洞等应力缺陷更容易出现。

Effect of laser shocking parameters(spot diameter,laser characteristics and peak pressure)on the formation mechanism of residual stress field of 7050 alloy were studied by means of simulation and experiment.The results show that the optimum peak pressure is 1500 MPa when the flat-topped laser is loaded with facula diameter of 2 mm,3 mm and 4 mm.When the Gauss laser is loaded,the optimum peak pressure is 1500 MPa,2000 MPa and 3000 MPa with facula diameter of 2 mm,3 mm and 4 mm,respectively.And the maximum residual stress after the flat-topped laser shock is increased by about 10% than Gauss laser when the peak pressure is 1500 MPa.When the peak pressure is greater than 2000 MPa,affected by surface convergence wave,the maximum residual compressive stress after shocking by flat-topped laser is less than that of Gauss laser.When shocked by the flat-topped laser,the actual optimal solution of peak pressure is consistent with the theoretical optimal solution,which is 1500 MPa.In the case of Gauss laser shocking,the actual optimal solution of peak pressure increases gradually with the increase of the spot diameter.When the peak pressure exceeds 2000 MPa,the residual compressive stress no longer increases significantly,and stress defects such as residual stress holes are more likely to occur.