The Theory And Numerical Analysis Of Gun Barrel Safety Problem

Based on the research project of national defense science and industry, safety problems of gun barrel are studied by the combination of fatigue, fracture and probability theory. The primary work and remarks of the paper are as follows:(1)Stress intensity factors of gun barrel under inner pressure are obtained by finite element method. The accuracy of displacement method and stress method are compared. Some patterns of dynamic stress intensity factor are studied.(2)Considered the strain hardening and Bauschinger effect of gun barrel material, autofrettaged residual stresses are calculated and compared with autofrettaged residual stresses under elastic-perfectly plastic behavior of material of gun barrel.(3)The forms of fatigue cracks in bore of gun barrel are considered as edge cracks and semi-elliptical cracks. The stress intensity factors of gun barrel are calculated using a weight function method under the autofrettaged residual stress, thermal stress and assemblage stress.(4)A circulating loading experimental apparatus is designed. Experiment of fatigue cracks growth are done in the thick wall cylinder samples. And the experimental methods are provided. Growth parameters of fatigue cracks of the thick wall cylinder samples are calculated.(5)A reliability analysis method for critical crack depth and fatigue life of autofrettaged gun barrel, which is based on probabilistic fracture mechanics theory and Monte Carlo simulation, is given in the research of safety of gun barrel. Considered probability of working conditions and material properties of gun barrel, samples of critical crack depth and fatigue life of autofrettaged gun barrel are generated by Monte Carlo simulation. The best fit of distribution of samples is determined by parameter estimation and distribution test. The research on some influence of autofrettaged degree, initial crack depth and thermal stress on gun barrel safety is also done in the thesis.This research is significant to secure gun barrel safety and avoid disastrous accident.