It is well known that direct application of fracture toughness values measured from standard laboratory specimens to structural components without matching constraint conditions may lead to over-conservative results for structural integrity assessment. In some cases, this may lead to unnecessary repairs or even to an early retirement of the structural component. This is particularly true for structural components operating at late life. For this reason, inclusion of constraint effects on fracture toughness in structural integrity assessment is of great importance. Research on the constraint effects has been very fruitful and is generating standardized methods and procedures that are suitable for engineering applications. This paper provides a review of constraint effects on fracture toughness for structural integrity assessment in fitness-for-service codes.

Several fitness-for-service codes (API 579-1/ASME FFS-1, BS 7910, R6, SINTAP/FITNET) have code provisions for including the constraint effects on fracture in ductile-brittle transition region. This paper reviews the two fracture toughness adjustment methods as implemented in the 2019 Edition of BS 7910 and the 2021 Edition of API 579-1/ASME FFS-1. We present the results from a comparative study of the two adjustment methods using four sets of test data recently published in the literature.

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