Development of constraint-based fracture mechanics methodologies for structural integrity assessments and fatigue life predictions

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Safe operations of high performance engineering structures, such as those in nuclear pressure vessels, gas pipelines, offshore and aerospace industries, are of practical significance. To assure the structural integrity, it is essential that fracture mechanics analyses considering the behavior of defects are conducted to assess the safety margins over the service life spans of these components. Conventional fracture mechanics are based on the assumption that a single parameter (e.g. J, K or CTOD) uniquely characterizes the crack tip stress and strain fields. However, it is now well understood that a single parameter generally cannot completely characterize the crack tip stress strain fields. This gives rise to the so-called constraint effect. Significant research progress has been made over the past 18 years in characterization of constraint effects. Methods of quantifying the in-plane constraint effects using an additional fracture parameter have been well-established.