不同典型结构激光冲击强化的疲劳差异性研究

Study on the differences of typical structure after laser shock peening

激光冲击强化不同典型结构对各结构疲劳寿命的影响均有所差异,本文基于ABAQUS模拟典型结构小孔φ2.6、圆角R3和圆棒(小径φ20)的激光冲击强化过程,并提取出各路径的残余应力分布(峰值压力分别为4、5、6、8GPa),同时对各典型结构TC4-DT钛合金双联试样进行激光冲击与疲劳拉伸试验。结果表明:在应力水平385MPa、应力比R=0.1下,经激光冲击的圆角与小孔的疲劳增益均较大,且圆角最大疲劳增益为238.4%(功率密度为12.75GW/cm^2),小孔疲劳增益为243.3%(功率密度为22.67GW/cm^2)。圆棒结构在应力水平600MPa下的疲劳负增益均较大(功率密度22.67GW/cm^2时的疲劳增益减小至-94.1%)。经激光冲击强化的圆角根部、圆角边缘处及小孔孔角残留较大的残余压应力,使该典型构件的应力集中处的疲劳寿命得到显著提升,但圆棒内部残留的残余拉应力使其在拉伸载荷下极易出现疲劳裂纹。对于圆棒等旋转体而言,激光冲击虽然提高了表面疲劳性能,但在拉伸载荷下容易疲劳断裂。该研究对各典型结构的激光冲击强化具有指导意义。

The different structures of aircraft have different effects on the fatigue life under laser shock peening.Based on the ABAQUS simulation,the residual stress distribution after laser peening on hole φ2.6,fillet R3 and round bar(Min- diameter φ20)with different power density is analyzed.The laser peening and tensile fatigue tests were performed on the corresponding TC4-DT titanium alloy specimens.The results show the fatigue gain of fillets and corners are larger at Max-stress 385 MPa and stress ratio R=0.1.The fatigue gain of fillet is 238.4 % at 12.75 GW/cm^2,and hole′s fatigue gain is 243.3 % at 22.67 GW/cm^2.The fatigue gain of the bar is negative(the gain is reduced to -94.1 % at 22.67 GW/cm^2).The laser shock peening fillet and hole greatly improve the fatigue life of its weak region,which makes the fatigue gain more of the structure.Laser shock peening on the rotating body under tensile load may have a large negative impact,and the results have guiding significance for laser shock enhancement of characteristic structure.