Influence of mixed mode I/III loading on dynamic fracture toughness of mild steel at room and low temperatures

The effect of loading angle, ϕ, on the dynamic fracture toughness at room and low temperatures (−60 and −196 °C) as well as the effect of temperature on mode I and mixed mode I/III dynamic fracture toughness for mild steel was studied using a modified Charpy test specimen. The dynamic fracture toughness was found to increase with increasing loading angle or increasing mode III loading component at all three test temperatures. The mode I as well as mixed mode I/III dynamic fracture toughness was also found to decrease with decrease in temperature below room temperature. The results were explained on the basis of the operative fracture mechanisms and the nature of stress field ahead of crack under mode I and mixed-mode loading.