Simulation and experimental investigation of the spall fracture of 304L stainless steel irradiated by a nanosecond relativistic high-current electron beam

The results of numerical and experimental investigations of the shock-wave induced spall fracture of bulk samples with thickness up to 10 mm made of 304L stainless steel irradiated by a nanosecond relativistic high-current electron beam with duration of ∼ 45 ns, electron energy of 1.35 MeV, and peak power density of 34 GW/cm 2 are presented. By a mathematical model developed for numerical simulation of the shock-wave dynamics, it was found that a quasi-planar shock wave with duration of ∼ 0.2 μ s , and initial amplitude of 17 GPa was formed in the irradiated samples. The effects of orientation of δ -ferrite interlayers in the austenitic matrix relative to the shock wave direction on the spall fracture were experimentally investigated. It was found that spallation was carried out by mixed ductile–brittle fracture. For the transversal orientation of δ -ferrite, the contribution of a brittle fracture mode in the spallation is higher than that for the longitudinal orientation. In both cases, the spalled layer thickness increased almost linearly with the increase of the target thickness, which was in good agreement with literature data. By the comparison of experimental data with simulation results, it was revealed that the spall strength can be estimated as 6.1 GPa at strain rate 0.48 μ s - 1 and 3.4 GPa at strain rate 0.18 μ s - 1 , for samples with the longitudinal and transversal orientation of δ -ferrites, respectively. The comparison of the obtained spall strength values with literature data is considered.