Stress analysis of an autofrettaged thick-walled pressure vessel containing an external groove

Abstract

Stress analysis of an autofrettaged thick-walled pressure vessel containing an external groove and subjected to internal pressure is described. From the equivalence of thermal and autofrettage residual stress fields, the autofrettage residual stress distributions of the external grooved thick-walled pressure vessel were simulated using an equivalent thermal loading. Thermal stresses due to the simulated thermal loadings for various degrees of autofrettage overstrain level were computed using finite element methods. Very high stress concentration factors due to internal pressure and autofrettage loadings (3·9–4·65) were obtained at the external groove root that contained a sharp root radius. This sharp root radius location was considered as the most vulnerable location for fatigue crack formation and growth. Experimental measurement of residual stresses for a fully autofrettaged thick-walled pressure vessel using an equivalent saw cut method resulted in very close agreement with the theoretical autofrettage residual stress distributions. The stress analysis results indicate that lower autofrettage overstrain and a groove geometry change is desirable for enhanced durability.