In order to design robust and reliable micro forming processes for composite metal foils, it is crucial to accurately forecast their forming limit under various strain paths. To date, however, there are few criteria that can effectively predict the forming limit of composite metal foils influenced by size effect. To solve this problem, a new uncoupled failure criterion is developed in this study, which considers the effects of interfacial layer, free surface roughening, grain size and strain path of heterogeneous materials, based on the deformation characteristic and failure mechanism of composite metal foils. Subsequently, it is presented the methodology for calculating the material constants of the proposed failure model. Additionally, the experimental forming limit strains of Ni/Cu clad foils with various grain sizes are utilized to show the prediction capability of the proposed model. To further confirm the application capability of the new failure criterion in practical micro forming, the finite element method incorporating the proposed criterion is employed to predict the failure behavior of Ni/Cu clad foil micro-channels in rubber pad forming. Comparisons indicate that the proposed model can accurately capture the forming limit of the composite metal foils influenced by size effect. This work provides a new scientific basis for determining the forming limit of composite metal foils.

中文翻译：

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预测复合金属箔细观/微观尺度成形极限的新失效准则

为了设计稳健可靠的复合金属箔微成形工艺，准确预测其在各种应变路径下的成形极限至关重要。然而，迄今为止，很少有标准能够有效预测受尺寸效应影响的复合金属箔的成形极限。为了解决这一问题，本文基于复合金属箔的变形特征和失效机理，提出了一种新的非耦合失效准则，该准则考虑了异质材料的界面层、自由表面粗糙化、晶粒尺寸和应变路径的影响。随后，提出了计算所提出的失效模型的材料常数的方法。此外，利用不同晶粒尺寸的Ni/Cu复合箔的实验成形极限应变来显示该模型的预测能力。为了进一步证实新失效准则在实际微成形中的应用能力，采用结合该准则的有限元方法来预测橡胶垫成形中Ni/Cu复合箔微通道的失效行为。比较表明，该模型能够准确捕捉受尺寸效应影响的复合金属箔的成形极限。该工作为确定复合金属箔的成形极限提供了新的科学依据。