薄壁Ti6Al4V管件采用不同车削参数加工引起的表面残余应力的测量

切削加工引起的金属零件的表面残余应力，其性质和大小对零件的服役性能产生很重要的影响。在测量车削加工Ti6Al4V薄壁管件引起的表面残余过程中，由于边缘效应的存在，使得零件的长度对测量精度有严重的影响。由于管件的壁厚很薄，当去除一应力层时会对剩余部分的残余应力的重新分布产生重要的影响，因此必须对剥层后X射线法测得的应力值进行修正补偿才能得到其初始应力值。传统的修正方法其计算比较复杂，对零件和应力都有特别的要求，而且在某些情况下其修正精度还达不到要求。同时考虑测量精度、测量可行性以及节约材料诸多方面的问题，本文运用有限元验证的方法确定零件合适的长度。同时本文运用精度较高的基于有限元分析的修正方法结合X射线法测量Ti6Al4V管件车削加工引起的表面残余应力，分析不同切削参数以及退火处理对表面残余应力的影响。结果显示：切削速度、进给量以及切削深度在指定范围内增大时会导致表面切削和进给方向的压应力增大，退火处理会使得表面两个方向的残余应力减小将近85%。

Measurement of surface residual stresses generated by turning thin-wall Ti6Al4V tubes using different cutting parameters

The surface residual stresses generated by machining, depending on their sign and magnitude, significantly affect the service life of the machined parts. In the measurement of the surface residual stresses induced by turning thin-wall Ti6Al4V tubes, the edge effect makes the length of the tube critical to the accuracy of the results. Moreover, owing to the thinness of the wall of the tube, the removal of the stress layers results in significant redistribution of the residual stresses in the remaining part of the workpiece. The stresses measured by the X-ray diffraction (XRD) method therefore require correction to determine the correct initial stresses. However, the traditional correction method is complex and requires some very strict conditions for the workpiece and residual stresses, and its accuracy is also insufficient for certain purposes. Hence, in this study, finite element analysis (FEA) was used to determine the optimal required length of the workpiece, taking into consideration factors such as accuracy, convenience, and material saving. A new and highly accurate FEA-based correction method involving simple calculations is proposed in this paper. The method was used in conjunction with XRD to determine the surface residual stresses of sample Ti6Al4V tubes and observe the effects of different turning parameters and annealing. It was found that both the compressive residual stresses in the cutting and feed directions increased with increasing cutting velocity, feed, and depth of cut within specific ranges, and that annealing produced approximately 85% stress relaxation near the surface in both directions.