Notch vs. Crack Effects on Impact Toughness and Fracture Behavior of a Duplex Steel Weldments

This paper presents the effect of stress concentration due to notch or cracks on the impact toughness of duplex steel S32750. This analysis is based on the results obtained by Charpy instrumented pendulum, enabling the separation of total energy into crack initiation, E_i, and crack propagation energy, E_p. The crack sensitivity factor (CSF) was determined, defined here as the ratio of total impact energy (KV value), obtained by testing standard ISO-V specimens, and KV1 value, obtained on a same type of specimen but with 1-mm long fatigue cracks: CS = KV/KV1. Testing was conducted in accordance with standard EN ISO 148-1:2017 at different temperatures: +20°C, −40°C, −60°C, and −80°C. Fatigue crack lengths ranged from 1 to 5.5 mm, as measured from the notch root on ISO-V specimen. Based on KV vs. crack length diagrams, KV1 values are obtained by interpolation of all results, providing data for CSF determination. Fractography was also done to clarify the fracture behavior of notched and cracked specimens under impact loading and different temperatures.