Since pressure vessels do not always present fragible failure.it is not on the safe side to assess pressure vessels only by using the Kic criterion of linear elastic fracture mechanics. Tn view of the above

this paper presents a two-criteria approach with its origin and development and its basic concept and application are discussed. A number of specimens with cracks were tested by this approach for crack initiation. stable crack growth and the maximum load

the results of which show that the failure assessement curve of the two-criteria approach is the lower limit of the failure assessment points and can be used to evaluate the safety of cracked pressure vessels.