Effects of loading pressure and gap dimension on the formation of gap jet under strong dynamic loading

Tolerances in machining and assembly often result in gaps within engineering structures. Under strong dynamic loading, gap jets may form within these gaps, thereby posing a threat to the reliability and safety of the structure. However, the formation mechanism of gap jets differs from that of traditional high-speed metal jets, and its formation process still requires systematic study. Hypervelocity impact loading experiments on tungsten samples with gaps were conducted using a two-stage light gas gun, and the formation and evolution of the gap jet were recorded using a high-speed framing camera. A numerical model for predicting the formation of gap jets was established using ANSYS Autodyn, and the applicability of the numerical simulation method was validated by comparing the numerical results with the jet morphology and head velocity history data obtained from a representative experiment. The effects of flyer velocity, gap width, and gap half-angle on the formation of the gap jet were investigated by adjusting these parameters in the numerical model, and the variations in the gap jet head velocity and mass with respect to these factors were obtained. The limitations of the steady-state jet model were analyzed, and an empirical model was developed to predict the jet head velocity and mass based on the findings from numerical simulations. The results show that the numerical model based on the Eulerian method can accurately predict the formation of the gap jet under strong dynamic loading. Loading pressure is found to be the main factor controlling the jet head velocity and mass; as the loading pressure increases, both the jet head velocity and mass increase accordingly. The gap width and half-angle have little effect on the jet head velocity, but the mass increases linearly with the gap width and half-angle. Due to significant errors in estimating the gap closing velocity, the steady jet model fails to accurately predict the formation of the gap jet. In contrast, the developed empirical model shows good agreement with the numerical results.