A universal statistics-based material inhomogeneity “fingerprint” governing spontaneous adiabatic shear bands in thick-walled cylinders

It is unclear whether material inhomogeneity plays a significant role in the formation of spontaneous adiabatic shear bands (ASBs) in axisymmetric structures under high-strain-rate loading when property fluctuations are significantly present. The absence of a reliable method for quantifying material inhomogeneity has hindered the understanding of ASBs. This study proposes a universal material inhomogeneity statistics (UMIS) model to quantify material inhomogeneity and establishes an integrated numerical framework for simulating ASB evolution. The UMIS model is defined by three physically measurable statistical descriptors: the amplitude of property fluctuation, the Moran’s index describing spatial autocorrelation, and the characteristic length defining the spatial resolution. A high-density Vickers hardness testing method is introduced to quantify the UMIS descriptors. A probability-driven random placement algorithm, a fracture phase-field finite element method, and a modified Johnson-Cook flow stress model are integrated to reconstruct material inhomogeneity and capture ASB initiation and evolution. The UMIS model and the integrated framework are validated against the thick-walled cylinder (TWC) experiments, showing excellent agreement in overall ASB morphology, local features, and statistical characteristics, and outperforming the conventional random model. The UMIS-based simulations reveal clustering behavior of spontaneous ASBs in terms of length and spacing and clarify how amplitude and spatial autocorrelation govern ASB evolution, serving as a unique “fingerprint” of material inhomogeneity. The results further underscore that material inhomogeneity plays a pivotal role in the transition from spontaneous to forced ASB patterns, while maintaining consistent macroscopic properties. The UMIS model provides an accurate characterization and statistical reconstruction of material inhomogeneity.