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

Tolerances in machining and assembly often result in gaps in engineering structures. Under strong dynamic loading, gap jets may form within these gaps, 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 research. Based on a two-stage light gas gun, hypervelocity impact loading experiments were conducted on tungsten samples with gaps. 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. 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. By adjusting the flyer velocity, gap width, and gap half-angle in the numerical model, the effects of these three factors on the formation of the gap jet were studied. The variations in the gap jet head velocity and mass with respect to these factors were obtained, and the limitations of the steady-state jet model were analyzed. Based on the findings from numerical simulations, an empirical model was developed to predict the jet head velocity and mass. 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 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.