Analysis on dynamic shear fracture based on a novel damage evolution model

Dynamic shear experiments and relevant numerical simulations are crucial for comprehensively understanding shear fracture mechanisms under diverse strain rates. In numerical simulations, damage evolution models are important for accurately capturing fractures and for guiding engineering applications under impact loading. To better predict dynamic fractures, a novel dynamic fracture model based on statistic damage mechanics is proposed. Based on the two-dimensional phase-field theory, the acceleration of void deformation is introduced into the void number continuity equation from the mesoscale. As fracture surfaces are formed by void evolution, a novel damage level is defined as the ratio of the statistical cross-sectional area of voids to the cross-sectional area of representative elements. Combining the void number continuity equation and the abovementioned damage level, a novel damage model is established based on void nucleation and ellipsoidal void growth. Based on percolation theory, a damage-softening function suitable for such a model is derived to characterize the effect of void coalescence on damage. Subsequently, dynamic shear tests are conducted at different strain rates using Split Hopkinson Pressure Bar (SHPB) and double-shear specimens with different shear zone widths. Two groups are defined to perform the dynamic shear experiments. One group is used to obtain the numerical model parameters and the other is used to investigate the fracture and void evolution. Scanning electron microscopy (SEM) tests are performed to analyze the effect of strain rate on void evolution. Moreover, the damage evolution model is used in the numerical simulation and its reliability is verified. The numerical results are consistent with the experimental results in terms of the strain signals and void number distributions. The effects of strain rate on fracture and void evolution are investigated via numerical simulations. All the results indicate that the proposed model can accurately predict dynamic shear fractures under different strain rates, thus serving as a useful reference for engineering design.