Direct measurement of J integral – A retrospective

Abstract

Direct measurement of J integral has been presented as a retrospective of more than 40 years of experience. Early efforts and experiments on welded wide plates and pressure vessels are presented and analysed in respect to the effect of material heterogeneity. Physical meaning of the J integral values obtained by direct measurements on a pressure vessel is explained to clarify its appli- cation. Different boundary conditions are also considered, to investigate options for simplified measurements. The possibility of applying simplified direct measurement of J integral for pressure vessel integrity assessment has been considered. Finally, it is noted that the measurement of strains by digital image correlation instead of strain gauges can make a new life of this technique.