ELASTIC PLASTIC FRACTURE-MECHANICS FOR PRESSURE-VESSEL DESIGN

The project has been concerned with the verification of the J-philosophy for initiation and growth of cracks on laboratory type specimens as well as on larger surface cracked plates. The analysis of the experiments involved extensive fully three-dimensional finite element calculations. It was found that the initiation events for the six surface cracked plates occurred at approximately the same J-value. A corresponding relation to the laboratory type specimen was less successful, mainly because of the short-comings of current methods for J(IC)-evaluations. A somewhat puzzling feature of the surface crack experiments was that unstable crack growth occurred immediately after crack growth initiation in four out of six tests, while some amount of stable crack growth was evident in the remaining two and in all of the laboratory type specimens. An evaluation of the surface experiments by a type of R6-analysis was also performed. Using as K(cr) the mean value from the surface crack experiments, it was found that the R6-method yielded conservative predictions.