新型光斑搭接对平顶激光冲击钛合金力学性能的影响

针对平顶光束的特点，为简化工艺，提高加工效率，提出了一种简化加工过程的搭接率工艺方法。采用一种纵向25%、横向56.5%的搭接率工艺，并对该搭接率下的残余应力、显微硬度、高周疲劳极限等力学性进行验证，对比其与传统50%搭接率下的性能差异。结果表明：在新型搭接率下，平顶激光冲击钛合金表面产生的残余压应力均值为-564.5 MPa，影响深度达0.82 mm；在传统搭接率下，表面产生的残余压应力均值为-559.2 MPa，影响深度达0.81 mm。在新型和传统两种搭接率下，平顶激光冲击钛合金表面重叠次数多的位置，显微硬度平均值分别为570.9和562.6 HV_0.3，重叠次数少的显微硬度平均值分别为432.1和453.4 HV_0.3；钛合金截面上的硬化层深度均为0.4 mm。在新型和传统两种搭接率下，平顶光束冲击钛合金的疲劳极限分别为256.3和264.6 MPa。基于平顶光束，与传统工艺相比，简化的新型搭接率工艺可以获得较好的力学性能，并提高加工效率，降低加工成本。

Effects of Novel Overlapping on Mechanical Properties of Flat-topped Laser Shock Peening Titanium Alloy

To simplify the process and improve the efficiency, a novel overlapping method was proposed. The novel overlapping rate was set as longitudinal 25% and lateral 56.5%. The residual stress, micro-hardness, and high cycle fatigue limit of the titanium alloy after laser treatment with this overlap were investigated. The comparison of the above mentioned mechanical properties between the new overlap and the traditional 50% overlap was also studied. Results show that the mean value of surface compressive residual stress induced by laser shock peening (LSP) is -564.5 MPa with the new overlap, and the influenced depth reaches 0.81 mm. With the traditional overlap, the surface compressive residual stress induced by LSP is -564.5 MPa and the depth of compressive residual stress is 0.82 mm. The surface micro-hardness of titanium alloy after LSP at more overlapping regions are 570.9 and 562.6 HV_0.3 and that at less overlapping regions are 432.1 and 453.4 HV_0.3, respectively. The layer of compressive residual stress after LSP are both 0.4 mm. The high cycle fatigue limit of titanium alloy after LSP are 256.3 and 264.6 MPa with the new and traditional overlapping rates, respectively. Based on the flat-toped laser beam, the mechanical properties of the titanium alloy after LSP with this novel simplified overlapping rate process can be obtained as same as that with 50% overlapping rate. The processing efficiency increases and the cost is reduced.