Formability Test for Characterizing the Mode II–III Fracture Transition

Abstract:

The transition between different shear fracture modes is still not well understood, especially in the case of mode II to mode III fracture. While transitions involving mode I have been investigated in previous studies, the interaction between in-plane and out-of-plane shear fracture remains largely unexplored. This work presents an ongoing study aimed at analysing this transition through a newly proposed formability test based on the compression of a thick sheet. The test is intended to investigate the transition region between the shear fracture forming limit (SFFL) and the out-of-plane shear fracture forming limit (OSFFL), associated with fracture mechanics modes II and III, respectively. A new specimen geometry was developed by combining features of existing configurations designed to activate each fracture mode separately. Finite element simulations were carried out to support the design of the specimen and to provide an initial analysis of the strain loading paths in the ligament region. Preliminary numerical results indicate that the proposed test can promote in-plane shear, out-of-plane shear, as well as mixed fracture mechanisms. The predicted fracture initiation sites and corresponding strain paths were examined in the effective strain–stress triaxiality space to provide initial insight into the role of stress state on fracture behaviour. The influence of notch orientation on the resulting fracture mode is discussed, highlighting the potential of the proposed approach for studying mixed shear fracture conditions.

• Periodical: Solid State Phenomena (Volume 388)
• Pages: 171-178
• DOI: https://doi.org/10.4028/p-Hp3vb8
• Online since: April 2026
• Authors: Inês M. Almeida*, João P.G. Magrinho, Paulo A.F. Martins, Maria Beatriz Silva
• Keywords: Fracture Forming Limits, Sheet Compression Test, Sheet-Bulk Forming

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