Analyses of Crack Propagation under Thermo-Mechanical Coupling Conditions in Typical Small-Caliber Gun Barrels

This study investigates the propagation pattern of barrel matrix cracks by analyzing the morphology and dimensions of radial cracks in barrels at different stages of life. A finite element numerical model was established for a chrome-plated barrel with an internal radial crack under thermal load, gas pressure load, and coupled load effects, capturing the stress response at the crack tip within the barrel bore under cracked conditions. Incorporating the results of crack morphology analysis, a relationship between the internal crack size and the number of projectiles fired was established, and an empirical model for crack propagation was developed. The critical crack size and the crack expansion life of the barrel at the dangerous cross-section were analyzed and compared. The results indicate that the most hazardous location of the barrel is at the rear part, which is subjected to high gas loads and has a thinner wall thickness. When the maximum chamber pressure exceeds 450 MPa, the theoretical safe service life of the barrel has decreased to a level comparable to the life required to maintain ballistic accuracy, at which point the safety of the barrel can no longer be assured.