基于斜面法原理的7075-T651铝合金板材内部三维残余应力分布

为提高飞机性能与可靠性、减轻质量，越来越多的铝合金整体结构件被采用。毛坯初始残余应力是引起铝合金整体结构件加工变形的主要原因之一，对毛坯内部三向残余应力的分布规律进行高效精确的测量显得尤为重要。针对传统剥层法操作繁琐、效率低的问题，提出一种新的测量毛坯三向残余应力方法——斜面法。实验以7075-T651铝合金预拉伸板为研究样件，分别利用剥层法和斜面法对其内部三向残余应力进行测量。对测量结果进行修正，以减小斜坡加工引起的残余应力测量误差。结果表明：传统剥层法与修正后的斜面法测量结果沿深度方向的分部规律均呈M形；与传统剥层法相比，斜面法测量效率提高10倍；残余应力经修正公式修正后的斜面法测量结果误差90%在6 MPa以内；新方法不仅可以精确高效地测量毛坯全厚度的残余应力，还能够对表层20 μm深度的残余应力进行检测。

Slope Measurement Method for Three-dimensional Residual Stress in 7075-T651 Aluminum Alloy Plate

In order to improve the performance and reliability of airplane and reduce its weight，the aluminum alloy monolithic structure parts are increasingly used in the aviation industry. The initial residual stress (IRS) is a crucial factor influencing the machining deformation of aluminum alloy monolithic structure parts. The effective research on deformation depends on the accurate and efficient measurements of IRS. The traditional layer-removed method for the residual stress measurement is time consuming as it requires the repeated gluing and removing of strain gauge. An innovative slope method is proposed to measure the three-dimensional IRS of the pre-stretched aluminum alloy plate. The measured results must be modified in order to reduce the measurement errors. The profiles of residual stress measured by two methods are like double M type curves. The slope method raises the measurement efficiency by tenfold compared with the traditional layer-removed method. About 90% of all the absolute errors of residual stress corrected by two methods are within 6 MPa. The slope method is used to measure the residual stress across the thickness of workpiece, and also abtain the residual stress of subsurface within 20 μm.