Experimental and Numerical Investigation of the Influence of Process Parameters in Incremental Sheet Metal Forming on Residual Stresses
Experimental and Numerical Investigation of the Influence of Process Parameters in Incremental Sheet Metal Forming on Residual Stresses
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DOI：
10.3390/jmmp3020031
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发表时间：
2019-06-01
影响因子：
3.2
通讯作者：
Bambach, Markus
中科院分区：
文献类型：
--
作者：
Maqbool, Fawad;Bambach, Markus
本研究的目的是分析单点增量成形（SPIF）成形零件的几何精度与材料中残余应力的分布之间的相互关系，这是SPIF成形过程中不同工艺参数的函数。通过改变SPIF的工艺参数，即刀具直径、刀具降压和壁角，对锥体锥台进行了研究。采用钻孔应变计法测定了加工锥体的残余应力。此外，用激光从金字塔上切割出小条，并测量这些小条的曲率。带材的曲率是残余应力强度和分布的结果，而残余应力又取决于所选的工艺参数值。通过验证的SPIF数值模型，确定了夹紧状态、未夹紧状态和修剪状态下带材切割中心平行和垂直于刀具运动方向的残余应力。进一步，计算了在解夹和修剪时发生的带材弯矩变化。实验和数值研究表明，壁面角是影响残余应力积累和几何精度降低的最重要参数。解夹时，残余应力和弯矩变化最大，刀具降压最大，刀具直径最大。切边后，沿刀具运动的横向，残余应力和弯矩的大小随刀具降压幅度的增大而变化最大，随刀具直径的减小而变化最大。切边时，刀具运动横向壁面角较大时，几何偏差最大。总的来说，改变工艺参数对残余应力状态和几何精度的影响在刀具运动的横向上更为明显。
The aim of this study is to analyze the co-relation between the geometrical accuracy of parts formed by single-point incremental forming (SPIF) and the resulting distribution of the residual stresses induced in the material as a function of the different process parameters of the SPIF process. The study was performed for a pyramidal frustum manufactured by varying the process parameters of SPIF, i.e., tool diameter, tool step-down, and wall-angle. The hole-drilling strain gage method was used to determine the residual stresses in the manufactured pyramids. Further, small strips were laser cut from the pyramids, and the curvature of the strips was measured. The curvature of the strips is a result of the intensity and distribution of the residual stresses, which in turn depends on the selected values of the process parameters. A validated numerical model of SPIF was used to determine the residual stresses parallel and perpendicular to the direction of tool motion at the center of a strip cut from the numerical model in clamped, unclamped, and trimmed states. Further, the change in the bending moment of a strip that occurred upon unclamping and trimming was calculated. Experimental and numerical investigations reveal that the most significant parameter in residual stress build-up and the reduction of geometrical accuracy is the wall angle. Upon unclamping, the highest change in the residual stresses and bending moment occurred with the largest tool step-down and tool diameter. Upon trimming, the magnitude of the residual stresses and bending moment changed the most with the largest tool step-down in both directions, whereas the change was highest with the smallest tool diameter in the transverse direction of the tool motion. Furthermore, upon trimming, the geometric deviations were highest with the large wall angles in the transverse direction of the tool motion. Overall, the effect of changing process parameters on the residual stress state and geometrical accuracy was more pronounced in the transverse direction of the tool motion.