Characterization of stable ductile crack propagation by CTOA: Review of theory and applications

摘要

Fracture toughness is a crucial material property in structural design with metallic materials. For resistance against crack initiation, the crack-tip opening displacement (CTOD) (or, equivalently, the J integral) is well established. For resistance against crack extension, the "resistance curve" (J as a function of crack size) may be used for limited amounts of crack growth. However, for crack increments much larger than the material thickness, the most useful criterion for toughness characterization is the crack-tip opening angle (CTOA). During the past three decades, standards have been introduced to enable reproducible measurement of CTOA. Simultaneously, improved computer-aided photographic methods have been developed to measure surface CTOA during the fracture process, and analysis of the mechanics of bend specimens has enabled deduction of the CTOA from load and displacement. Elastic-plastic finite-element analyses using a constant-CTOA fracture criterion have been used to simulate fracture of laboratory specimens and structural components and to transfer the properties measured from laboratory-scale specimens to structural applications. This paper reviews the state of the art in measurement and application of CTOA.