Dominant deformation mechanisms in single point incremental forming (SPIF) and their effect on geometrical accuracy
Dominant deformation mechanisms in single point incremental forming (SPIF) and their effect on geometrical accuracy
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DOI：
10.1016/j.ijmecsci.2017.12.053
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发表时间：
2018-02-01
影响因子：
7.3
通讯作者：
Bambach, Markus
中科院分区：
文献类型：
--
作者：
Maqbool, Fawad;Bambach, Markus
通过渐进板料成形形成的零件的最终几何精度取决于在零件中产生的变形机制和残余应力。在这方面，一些研究已在文献中报道，其中调查的单点渐进成形（SPIF）过程的形成机制。根据不同的条件和实验装置，不同的研究小组揭示了膜拉伸，弯曲或剪切变形模式占主导地位。目前的文件向前迈进了一步，量化的各自的贡献，即膜拉伸，弯曲，通过厚度剪切，参与SPIF过程和几何精度和占主导地位的变形mechanisni之间的依赖关系。为此，SPIF过程的验证的数值模型用于记录相应的变形历史，即应力/应变分量。使用的分析方法，在SPIF过程中消耗的塑性能量分裂作为膜拉伸，通过厚度剪切和弯曲变形模式中消耗的能量的贡献。此外，基于有限元模拟的参数研究被用来分析变形机制的敏感性SPIF工艺变量，即工具直径，工具步降，摩擦，板厚度和壁角。数值和分析方法的结果进行了验证实验。结果表明，在用SPIF成形的零件的几何形状上的任何位置处，变形总是这三种模式的组合。一种变形模式对其他两种变形模式的主导作用取决于工艺变量，例如，弯曲变形模式在较大的工具直径下占主导地位，剪切变形模式在增加板厚度时占主导地位。的患病率的每个变形模式作为SPIF过程变量的函数进行了讨论。此外，通过数值模拟证明了主导变形模式对几何精度的实际影响。在弯曲变形模式中能量耗散的减少导致较低的残余力矩。因此，通过增加节距和减小工具直径，由于弯曲变形模式的贡献减少和残余力矩降低，实现了几何精度的增加。(C)2018爱思唯尔有限公司版权所有
The final geometrical accuracy of a part formed by incremental sheet forming depends on the deformation mechanisms and the residual stresses created in the part. In this regard, several studies have been reported in the literature, which investigate the forming mechanisms of the single point incremental forming (SPIF) process. Depending on the condition and experimental set-up, different research groups revealed that either membrane stretching, bending or shear deformation modes prevail. The current paper moves a step forward and quantifies the respective contribution of each forming mechanism, i.e. membrane stretching, bending, through-thickness shear, involved in the SPIF process and the dependence between geometrical accuracy and the dominant deformation mechanisni. For this purpose, a validated numerical model of the SPIF process is used to record the respective deformation histories i.e. stress/strain components. Using an analytical approach, plastic energy dissipated during SPIF is split as a contribution of energies dissipated in membrane stretching, through-thickness shear and bending deformation modes. Further, a parametric study based on FE simulations is used to analyse the sensitivity of deformation mechanism to SPIF process variables, i.e. tool diameter, tool step-down, friction, sheet thickness and wall angle. The results of the numerical and analytical approach are validated by experiments. The results indicate that at any location on the geometry of a part formed with SPIF, the deformation is always a combination of these three modes. Dominance of one deformation mode over the other two depends on the process variables, for example, the bending mode of deformation dominates at larger tool diameters and shear dominates at increasing sheet thickness. The prevalence of each of the deformation modes as a function of the SPIF process variables is discussed. Further, the practical consequence of the dominant deformation modes on the geometrical accuracy is demonstrated by numerical simulations. A decrease of the energy dissipation in the bending deformation mode leads to lower residual moments. Hence, by increasing pitch and decreasing the tool diameter, an increase in the geometrical accuracy is achieved due to the decreased contribution of the bending deformation mode and lower residual moment. (C) 2018 Elsevier Ltd. All rights reserved.