THE APPLICATION OF FAILURE ASSESSMENT DIAGRAMS (FADs) TO ENVIRONMENTAL ASSISTED CRACKING PROPAGATION

摘要

The environmental working conditions of structural steels, as in the cases of energy and oil installations, established the need to find appropriated methodologies for characterising their cracking resistance. The characterization of the environmental assisted cracking behaviour of the very tough steel actually used has been resolved after a methodology that determines the kinetics of cracking as a function of the parameters which control this process, both in elastic and elastic-plastic domains. Based on these parameters and microstructure and mechanical characteristics of the materials, the crack propagation process has been modelled in order to identify the dominant micromechanisms, either intergranular or transgranular, up to the final fracture. The application to such modellisation to the structural scale is the objective of this paper. A FAD (Failure Assessment Diagram) type analysis has been used to define the zones of the hydrogen assisted cracking processes dominance by different micromechanisms in two different microalloyed steels.