Constraint Effect—How to Link Between Structural Integrity Assessment and Fracture Toughness Evaluation

Abstract

The difference in the degree of plastic constraint in the vicinity of a pre-existing crack brings about difficulty in the evaluation of fracture performance of weldments when using fracture toughness obtained by conventional fracture toughness test results. The constraint controlling factors can be divided into two main areas, geometrical and material factors. The effect of both factors on the stress/strain behavior in the vicinity of a crack tip is discussed systematically based on previous research and numerical analyses. It is clarified that the common fracture parameters such as J and CTOD do not always represent material constants because of the change of stress/strain behavior as a result of the difference in plastic constraint. The possibility of evaluation based on the local approach is discussed in order to link between structural integrity assessment and fracture toughness evaluation.