基于輪廓法測試模鍛鋁合金7050-T74內部殘余應力Residual stress measurement in die forging of 7050-T74 aluminum alloy using contour method

針對鋁合金航空整體結構件的加工變形問題，采用輪廓法研究模鍛鋁合金結構梁7050-T74材料內部的殘余應力。應用電火花加工技術切割試樣截面，精確測量切割面的變形輪廓，擬合由于殘余應力釋放導致的切割面變形輪廓，將變形輪廓值作為位移邊界條件進行彈性有限元分析，得到垂直于切割面的二維殘余應力分布。采用鉆孔法測試試樣表層的殘余應力，并與輪廓法測試結果進行比較分析。結果表明：材料內部殘余應力主要源自拉彎工藝。模鍛件T型截面的內部殘余應力分布為外區受拉，內區受壓。輪廓法能夠精確高效地測試材料截面的殘余應力分布，邊緣區域的測試誤差可以依據表面殘余應力測試技術進行修正。

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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