Multi Physical Field Damage Modeling And Simulation Analysis Of Autofrettaged Barrel

The autofrettage process is applied to the gun barrel to improve the working stress of the barrel by using residual stress,thereby improving the strength and fatigue life of the barrel.A finite element simulation model with initial damage for a autofrettaged barrel was established,involving multiple physical field coupling loading conditions such as bore pressure and temperature,as well as macro and micro scale simulation analysis.Taking cracks as the main damage condition,the crack propagation,fracture limit load,and mesoscale cracking were analyzed,and various factors were comprehensively considered to analyze and evaluate the safety of barrel.The main research contents are as follows:(1)According to the distribution of residual stress of autofrettaged barrel under different autofrettage degree,theoretical calculation and simulation calculation were conducted,and the variation of residual stress in the barrel after rifling was also simulated and analyzed.(2)The stress intensity factors of the inner surface cracks of the barrel under different working conditions were calculated,indicating that the residual stress can effectively reduce the stress intensity factors of the barrel cracks under the same loading conditions,and reduce the crack growth rate;The influence of temperature load on the stress of the barrel is analyzed.The thermal stress generated by temperature load during the action period is compressive stress on the crack,which subsequently generates tensile stress in a certain area of the inner surface of the barrel,promoting the propagation of the surface crack along the radial direction;The self enhancing process has little impact on the contact pressure between the barrel and the projectile,and has a poor suppression effect on the expansion of horizontal lines on the surface of the barrel.Therefore,under the thermal pressure coupling and the mechanical action of the barrel and the projectile,the male line of the autofrettaged barrel is more prone to transverse cracks.(3)Based on the fracture design theory of the barrel,the critical crack size of the barrel is calculated,and the effects of various factors on the ultimate load of the barrel during fracture are analyzed.Temperature and the presence of pressure on the crack surface make the barrel more prone to fracture.Residual stress increases the ultimate load of the barrel,and the crack location also has an impact on the barrel fracture.(4)A multi scale simulation model of gun steel material under macro and micro conditions was established to calculate the stress and strain of the barrel during autofrettage process using a crystal plastic finite model;The fatigue germination of intergranular cracks was simulated using a cohesive element model.