Significance of the small crack growth law and its practical application

• Published in: Metallurgical and materials transactions. A, Physical metallurgy and materials science Physical metallurgy and materials science, 2000-08, Vol.31 (8), p.2005-2013
• Main Authors: KAWAGOISHI, N, CHEN, Q, NISITANI, H
• Format: Article
• Language: English
• Subjects: Applied sciences; Crack propagation; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Fatigue cracks; Fatigue failure; Fracture mechanics; Materials science; Mechanical properties; Metals. Metallurgy; Parameters; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics; Precipitation; Solid-phase precipitation
• ISSN: 1073-5623; 1543-1940
• DOI: 10.1007/s11661-000-0228-6

The effects of microstructure and specimen size on the fatigue crack growth rate of an annealed 0.42 C steel were investigated under uniaxial fatigue loading in air. Although a dramatic fluctuation of crack growth rate was found in the propagation process of microstructurally small cracks, the mean value of crack growth rate can be evaluated by a simple mechanical parameter, σanl (l, crack length; n, constant), under high stress levels where small-scale yielding conditions are exceeded. This parameter is also effective for cracks larger than 1 to 2 mm under high stress levels, as long as the finite boundary effect of a specimen on the driving force of crack propagation is considered. The crack growth rate of the alloy was described as a function of stress amplitude and crack length in terms of two mechanical parameters, σanl and ΔK. The applicable conditions of the two parameters were discussed and manifested.