基于轮廓法测试模锻铝合金7050-T74内部残余应力Residual stress measurement in die forging of 7050-T74 aluminum alloy using contour method

针对铝合金航空整体结构件的加工变形问题，采用轮廓法研究模锻铝合金结构梁7050-T74材料内部的残余应力。应用电火花加工技术切割试样截面，精确测量切割面的变形轮廓，拟合由于残余应力释放导致的切割面变形轮廓，将变形轮廓值作为位移边界条件进行弹性有限元分析，得到垂直于切割面的二维残余应力分布。采用钻孔法测试试样表层的残余应力，并与轮廓法测试结果进行比较分析。结果表明：材料内部残余应力主要源自拉弯工艺。模锻件T型截面的内部残余应力分布为外区受拉，内区受压。轮廓法能够精确高效地测试材料截面的残余应力分布，边缘区域的测试误差可以依据表面残余应力测试技术进行修正。

In order to study the machining distortion of aluminum monolithic structures in the aerospace industry, the internal residual stresses in monolithic die forging beam of aluminum alloy 7050-T74 were measured by using contour method. Electrical discharge machining was performed to cut the cross section of the specimen and the cut surfaces were measured by using laser scanner. The measured contours were fitted by using a 3D cubic spline based algorithm and then applied as an initial displacement boundary condition normal to the cut plane in the FE model but in the opposite direction. A linear elastic finite element analysis was then undertaken to calculate the corresponding distribution of residual stress normal to the cut face. In addition, the hole drilling method was employed to measure the surface residual stress of specimen, and its results were compared with those by the contour method at the same locations. The results indicate that the residual stresses in the specimen can be attributed to the stretch bending craft. The T-shaped cross section residual stress distribution shows a typical bending distribution of compression near the convex zone balanced by tension in the concave zone. Contour method efficiently provides accurate residual stress distribution in the test material. The test error at the edge area can be modified in compliance with surface residual stress measurement techniques.

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