THE BEHAVIOR OF SMALL CORNER CRACKS IN A FERRITIC PEARLITIC STEEL - EXPERIMENTS AND ANALYSIS

An experimental investigation into the growth and closure behaviour of small corner cracks has been conducted on a low carbon steel (ASTM A516 Grade 70). This ferritic/pearlitic steel has been chosen to investigate the complexities of small crack behaviour in the dual phase material. Innovative procedures are used for compliance measurement and opening load determination. The closure and growth behaviour of the small corner cracks are presented in terms of shape and size. The results are divided into two stages, the first pertaining to the ''stationary crack'', and the second dealing with the crack as it grows. The cracks are shown to exhibit an irregular growth rate, which is in part, shown to correspond with microstructural features of the material. In the short crack regime, the linear fracture mechanics parameter, Delta K does not correlate with the data and the use of a Delta K-eff based on the effective applied load provided little improvement.