A review on Fracture Toughness; concepts and test methods

Fracture toughness is usually used as a generic term for measures if materials resistance to expansion of a crack in engineering applications such as petrochemical industries and oil and gas pipelines. The concept of fracture toughness received profound importance in engineering design and applications, after the destruction of liberty ships in the World War II. In this paper, fracture toughness test methods, evaluation and standardization of metal materials are reviewed based on linear elastic and elastic-plastic fracture mechanics. The general principles and methods of testing developed by the American Society for Testing and Materials are explained. The main parameters of fracture mechanics such as elastic energy release rate (G), stress intensity factor (K), J integral, crack tip opening displacement (CTOD) and crack tip opening angle (CTOA) are defined. Finally, the scientific and computational foundations of the two factors (K) and CTOD, as the most widely used industrial factors will be examined in detail.