Propagation of Elasto-Plastic Stress Waves in Cylindrical High-Pressure Sections

An analysis is made of the axisymmetric elastic and plastic stresses and deformations in thick-wall cylindrical shells subjected to internal dynamic pressures. The study utilizes a direct numerical approach called the discontinuous-step analysis. This analysis is based on the direct use of the boundary conditions and the applicable physical laws to propagate dynamic changes in the cylinder by finite steps. Reflection of stress waves from both inner and outer boundaries is automatically generated. The validity of the method is checked by comparison of numerical results in the elastic range with published results for thick-wall cylinders. Comparison is made with experimentally measured strains from the high-pressure section of a hypervelocity launcher. This analysis assumes that the work hardening of the material is independent of the strain rate and is constant for a large variation of plastic strain. Stress-strain relationships are derived for the condition of plane strain in the cylinder which is held to be representative of the actual conditions in the launcher high-pressure section. The digital computer program developed from this study predicts the distribution of dynamic stress and strain throughout the cylinder, the internal radial growth, the distribution of particle displacement, the distribution of yield stress in an autofrettaged cylinder, and the residual stress.