Two-dimensional evolution of temperature and deformation fields during dynamic shear banding: In-situ experiments and modeling

Abstract

Adiabatic shear band (ASB) is a significant failure mechanism observed in metals and alloys under impact loading. Though ASB formation has been widely assumed to be a one-dimensional thermo-mechanically-coupled instability problem, it is crucial to recognize that adiabatic shear banding is essentially a two-dimensional propagating event in space. However, it is challenging to perform in-situ characterization of temperature-deformation fields during ASB formation due to the extremely small spatial and temporal scales involved. To obtain the two-dimensional features of ASB evolution, a newly developed plane-array infrared imaging system and microspeckle-based digital image correlation (DIC) technique are synchronized with the Kolsky bar system. By incorporating interrupted tests, “quasi-synchronous” characterization of temperature-deformation-microstructure evolution during ASB formation in hat-shaped specimens of Ti–6Al–4V is achieved. A phase-field model incorporating energy-based shear banding criteria and independently calibrated model parameters is established to simulate the dynamic shear failure process, which is demonstrated to be able to well reproduce experimentally observed temperature and deformation evolution. Based on experimental characterization and simulation results, the two-dimensional features and thermo-mechanical aspects of ASB formation are presented. Energy dissipation of shear banding is estimated based on the measured temperature field, demonstrating good agreement with the calibrated values in the phase-field model. The “propagation” and “percolation” modes along the band are analyzed, which can be predicted by the introduction of a shear band process zone. The influences of thermal and microstructural softening on shear failure are also clarified through a comprehensive analysis of temperature and microstructure evolution.