No abstract

No abstract

The small crack problem is addressed within the applicability of Linear Elastic Fracture Mechanics as the result of crack closure phenomenon. The variation of crack closure stress intensity factory Kop as a function of crack length, a, was determined in two materials, namely a A508 steel and a 2024A1 alloy. These results were obtained on two-dimensional small cracks (a 3 0.1 mm) which were machined from long fatigue cracks. These measurements of Kop in addition to data published in the literature on a nodular cast iron and a 9Cr-1Mo steel yield to a unique characteristic function: K,,/K, = 1 -exp(-ka) in which k is the only parameter to characterize the small crack effect. A prediction of the threshold behaviour of small and long cracks on A508 steel is made using the results of crack closure measurements.