铝合金冲击凹坑残余应力显微压痕测定方法

Measurement of Residual Stress at Impact Pit of Aluminum Alloy by Micro Indentation Method

金属结构的表面缺陷(如冲击、刮蹭等造成的损伤)可能会严重影响到其疲劳寿命,缺陷处的局部残余应力测定对缺陷处起裂寿命评估具有重要参考意义。采用有限元方法模拟了2A12铝合金冲击凹坑缺陷的产生和凹坑处的显微压痕试验,以此为依据评估了采用Lee模型计算缺陷处残余应力的精度。结果表明:凹坑底部残余应力(接近等轴情况)估算值与有限元模拟的标准值相比误差在6%以内;而凹坑边缘的残余应力(非等轴情况)估算值与有限元模拟的标准值之间的误差接近25%,通过对非等轴Lee模型进行修正,可将凹坑边缘残余应力的估算误差缩小到8%之内。

Defects on surface of metal structures(such as damage caused by impact or scraping)may seriously affect their fatigue life.The measurement of local residual stress at defects is of great significance to the assessment of initial crack fatigue life.The finite element(FE)method was used to simulate the processes of impact pit defects generation in aluminum alloy 2 A12 and micro indentation experiments at typical points of the pit.Based on the FE simulation,the accuracy of the residual stress calculation at the defect using the Lee model was evaluated.The results show that the error of estimated value of residual stress at the bottom of the pit(in equiaxial condition approximately)is less than 6%compared with the standard value obtained from finite element simulation,and the error of estimation of the residual stress on the edge of the pit(in non-equiaxial condition)is close to 25%.By correcting the Lee model,the error of estimation on the pit edge is reduced to less than 8%.