Shear band localisation in ductile fracture via phase-field models: a comparative analysis of volumetric locking mitigation techniques

This work addresses the phenomenon of shear band localisation within the framework of ductile fracture, employing the phase-field approachas a nonlocal modelling strategy. 
A key computational challenge in this class of problems is the volumetric locking arising from plastic incompressibility, whose inadequate treatment severely compromises the prediction of failure patterns.
A comparative study is presented for two well-established locking alleviation techniques: the B-Bar formulation and the Enhanced Assumed Strain (EAS) method. Both are incorporated into phase-field ductile fracture models featuring damage activation thresholds, coupled with the von Mises (J2) plasticity model.  The analysis is complemented by a detailed energy-based examination of the system, providing insight into the governing mechanisms of shear band nucleation and propagation.
Through a set of representative benchmark problems, the influence of each formulation on the morphology and orientation of shear bands is assessed, revealing significant discrepancies in the predicted failure patterns depending on the adopted scheme. The results demonstrate the efficiency and applicability of both formulations, while highlighting the critical role of the locking mitigation strategy in determining the overall model response.

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