Fracture assessment of ferritic steel components under dynamic loading

This paper summarizes recent studies on application of the Weibull stress model to predict cleavage fracture of structural components under dynamic loading. Two pressure vessel steels, the strongly rate-sensitive A515-70 steel and the moderately rate-sensitive Euro material (22NiMoCr37), are considered in the investigation. The results, based on independent calibrations at different loading rates, demonstrate that the Weibull modulus (m) is invariant of loading rate for both materials. While m remains a constant for each material, σu decreases and σw–min increases with higher loading rates. The studies also show that dynamic loading reduces constraint loss, i.e., it drives the response towards the small-scale yielding configuration, and this rate effect tends to saturate at higher loading rate. The demonstrated loading rate invariance of m, when combined with the Master Curve for dynamic loading, can provide a practical approach which simplifies the process to estimate σu as a function of loading rate.