Numerical Investigation of Residual Formability and Deformation Localization During Continuous-Bending-Under-Tension
Numerical Investigation of Residual Formability and Deformation Localization During Continuous-Bending-Under-Tension
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连续拉伸弯曲过程中残余成形性和变形局部化的数值研究
DOI：
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发表时间：
2012
期刊：
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通讯作者：
Y. Korkolis
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作者：
C. Nikhare;B. Kinsey;Y. Korkolis
一个普遍存在的实验来表征金属板的可成形性是标准的单轴拉伸试验。过去的研究[1-3]已经表明，如果材料在该测试期间反复弯曲和不弯曲（称为张力下连续弯曲，或CBT），则断裂伸长率百分比显著增加（例如，对于AISI 1006钢，从22%到290%[1]）。然而，过去的实验已经用CBT装置的固定行程进行，这限制了可成形性的改善。这种现象在工业中也已被经验性地观察到;通过拉延筋的板的破坏应变（即，在进入模具之前已经弯曲和展开三次）比原始片材的那些高。因此，材料在特定数量的CBT道次之后的剩余可成形性是令人感兴趣的，以确定多个拉延筋在该过程中是否有益。同样令人感兴趣的是加工过程中变形的局部化，因为这将为观察到的改善的可成形性提供更好的物理理解。在本文中，数值模拟来评估这些影响。结果表明，CBT过程中的成形性取决于材料的单轴响应，直到超过标准断裂伸长率。CBT过程可能会超过此限制。然而，一旦CBT过程终止，就会发生故障。此外，在CBT过程中，变形在整个标距上分布更均匀，这导致观察到的伸长率增加。Copyright © 2012 by ASME
A ubiquitous experiment to characterize the formability of sheet metal is the standard uniaxial tension test. Past research [1–3] has shown that if the material is repeatedly bent and unbent during this test (termed Continuous-Bending-under-Tension, or CBT), the percent elongation at failure increases significantly (e.g., from 22% to 290% for an AISI 1006 steel [1]). However, past experiments have been conducted with a fixed stroke of the CBT device, which limits the formability improvements. This phenomenon has also been empirically observed in industry; the failure strains of a sheet which is passed through a drawbead (i.e., that has been bent and unbent three times before entering the die) are higher than those of the original sheet. Thus, the residual formability of the material after a specified number of CBT passes is of interest, to determine if multiple drawbeads would be beneficial in the process. Also of interest is the localization of the deformation during the process as this will provide a better physical understanding of the improved formability observed. In this paper, numerical simulations are presented to assess these effects. Results show that the formability during CBT is dictated by the uniaxial response of the material until the standard elongation at failure is exceeded. This limit can be exceeded by the CBT process. However, failure then occurs as soon as the CBT process is terminated. Also, the deformation is more uniformly distributed over the entire gauge length during the CBT process which leads to the increased elongations observed.Copyright © 2012 by ASME