A new ductile failure criterion for micro/meso scale forming limit prediction of metal foils considering size effect and free surface roughening
A new ductile failure criterion for micro/meso scale forming limit prediction of metal foils considering size effect and free surface roughening
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DOI：
10.1016/j.ijplas.2022.103406
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发表时间：
2022-08
影响因子：
9.8
通讯作者：
Lihuang Zheng;Kun Wang;Yuanyuan Jiang;M. Wan;B. Meng
中科院分区：
文献类型：
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作者：
Lihuang Zheng;Kun Wang;Yuanyuan Jiang;M. Wan;B. Meng
为了建立可靠的微细观成形工艺，准确地预测不同变形路径下金属箔的成形极限是至关重要的。然而，现有的非耦合延性破坏准则不能在成形极限曲线(FLC)的整个应变路径范围内准确地预测受尺寸效应影响的金属箔的微细观成形极限。针对这一问题，基于尺寸效应对空洞形核、长大和合并的影响，以及自由表面粗化对金属箔临界损伤的影响，提出了一种新的延性失效判据。给出了延性破坏准则与修正的Yld2000屈服准则相结合的材料参数识别方法，并讨论了所提出的延性破坏准则对微细观尺度FLC的尺寸效应。此外，采用不同厚度和晶粒度的SUS304和纯铜箔的成形极限应变来揭示新的延性破坏准则的预测能力。与实验结果的对比表明，该失效准则能够准确地预测金属箔在单向拉伸和等双向拉伸之间的尺寸效应对成形极限的影响。为了进一步验证所提出的失效准则在实际微细观成形过程中的预测能力，将新的失效准则与有限元方法相结合，对SUS304铝箔微通道液压成形的极限拉深比和局部最大成形高度进行了预测，并与实验结果进行了比较。对比研究表明，所提出的塑性破坏准则能够准确预测金属箔在实际微细观成形过程中受尺寸效应影响的成形极限。
For the establishment of reliable micro/meso scale forming processes, it is essential to accurately predict the forming limits of metal foils under different deformation paths. However, existing uncoupled ductile failure criteria cannot accurately forecast the micro/meso scale forming limits of metal foils affected by size effect in the whole strain path range of forming limit curve (FLC). To deal with the issue, a new ductile failure criterion is proposed in this paper based on the theoretical analyses of size effect affected void nucleation, growth, and coalescence, as well as free surface roughening affected critical damage of metal foils. A method for identifying the material parameters of the proposed ductile failure criterion coupled with a modified Yld2000 yield criterion is provided, and the size effect on micro/meso scale FLCs forecasted by the proposed ductile failure criterion is discussed. In addition, the forming limit strains of SUS304 and pure copper foils with different thicknesses and grain sizes are employed to reveal the prediction capability of the new ductile failure criterion. Comparisons between the experimental results and the FLCs constructed by the proposed failure criterion demonstrate that the proposed failure criterion can accurately predict the forming limits of metal foils affected by size effect between uniaxial tension (UT) and equi-biaxial tension (EBT). To further show the prediction capability of the proposed failure criterion in actual micro/meso scale forming processes, the limit drawing ratio of a SUS304 foil and local maximum forming heights in micro-channel hydroforming for pure copper foils are predicted using the new failure criterion combined with the finite element method, and the predicted results are compared with experimental results. Comparative research demonstrates that the proposed ductile failure criterion can accurately forecast the forming limits of metal foils affected by size effect in actual micro/meso scale forming processes.