Failure analysis of a pressure vessel subjected to an internal blast load

The objective of the current work is to model a stainless steel (SA 316L) autoclave explosion and rupture that occurred during a research laboratory experiment designed to study the thermal decomposition of ammonium tetrathiomolybdate in the presence of dimethylsulfoxide (DSMO) in the autoclave. A finite element analysis is conducted to better understand the cause of failure of the autoclave and with the objective to investigate whether the incident was caused by static overpressure or an internal blast load. The empirical CONWEP blast loading model is used to model the internal blast load. The constitutive behavior of the autoclave material is modelled using the Johnson-Cook (JC) plasticity and material failure model, which both account for the effect of strain rate and temperature. By conducting uniaxial tensile tests and tests on notched ring specimens cut from the autoclave, the true stress-strain curve and the ductile failure locus of the autoclave material are established, respectively, which are used to obtain the constants of the JC plasticity and failure model, respectively. The result of the finite element analysis revealed that a blast load from an equivalent TNT charge of 0.042 kg, which resulted from the decomposition of DMSO at high temperature, predicted markedly well the structural response and subsequent failure of the autoclave observed in the post-incident investigation.