Plastic Analysis of the Instability of Pressure Vessels Subjected to Internal Pressure and Axial Load

Abstract

Future advances in rocket engine-case design are aimed at exploiting the capabilities of new high-strength steels. One mode of failure of such pressure vessels occurs due to plastic instability. This paper presents the results of analyses of the plastic instability behavior of pressure vessels made of Ladish D6A C steel using three methods of analysis of varying degrees of refinement. The Mises flow rule and associated flow equations are used to analyze the instability conditions for three ratios of the axial to the circumferential stress: 1/2 , 1, 2. The results of the analysis are compared with experimental data. The most precise method of analysis which includes the elastic strain gives instability pressures which agree with experiments with errors of less than 3 1/2 per cent.