A new failure criterion for predicting meso/micro-scale forming limit of composite metal foils

Abstract

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.