基于輪廓法測(cè)試模鍛鋁合金7050-T74內(nèi)部殘余應(yīng)力Residual stress measurement in die forging of 7050-T74 aluminum alloy using contour method

針對(duì)鋁合金航空整體結(jié)構(gòu)件的加工變形問題，采用輪廓法研究模鍛鋁合金結(jié)構(gòu)梁7050-T74材料內(nèi)部的殘余應(yīng)力。應(yīng)用電火花加工技術(shù)切割試樣截面，精確測(cè)量切割面的變形輪廓，擬合由于殘余應(yīng)力釋放導(dǎo)致的切割面變形輪廓，將變形輪廓值作為位移邊界條件進(jìn)行彈性有限元分析，得到垂直于切割面的二維殘余應(yīng)力分布。采用鉆孔法測(cè)試試樣表層的殘余應(yīng)力，并與輪廓法測(cè)試結(jié)果進(jìn)行比較分析。結(jié)果表明：材料內(nèi)部殘余應(yīng)力主要源自拉彎工藝。模鍛件T型截面的內(nèi)部殘余應(yīng)力分布為外區(qū)受拉，內(nèi)區(qū)受壓。輪廓法能夠精確高效地測(cè)試材料截面的殘余應(yīng)力分布，邊緣區(qū)域的測(cè)試誤差可以依據(jù)表面殘余應(yīng)力測(cè)試技術(shù)進(jìn)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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