ABSTRACT
This chapter focuses on approaches for computing the fracture driving force in structural components that contain cracks. It focuses on fracture initiation and instability in structures made from linear elastic and elastic–plastic materials. The chapter covers only quasistatic methodologies, but such approaches can be applied to rapid loading and crack arrest in certain circumstances. Analyses based on linear elastic fracture mechanics (LEFM) apply to structures where crack tip plasticity is insignificant. Laboratory fracture toughness specimens usually contain idealized cracks, but naturally occurring flaws in structures are under no obligation to live up to these ideals. Some design codes for structures such as pressure vessels and piping refer to load-controlled stresses as primary and displacement-controlled stresses as secondary. The original Crack tip opening displacement (CTOD) design curve was based on correlations with flat plates loaded in tension. If linear superposition were applicable, the reference stress for combined membrane and bending loads could be inferred simply by summing the contributions from each.
