Fracture toughness estimation for high-strength rail steels using indentation test

In this paper, tensile properties and mode I critical stress intensity factor (K-Ic) are measured on the railhead of six types of high-strength rail steels using standard testing methods. An instrumented ball indentation testing method is then developed to estimate fracture toughness for the six rail steels based on continuum damage mechanics. Critical damage parameter, determined by combining repeated loading-unloading tensile tests and a ductile damage model, is used to characterize a critical contact depth under indentation that is used to calculate the specific indentation energy, and thus the fracture toughness for indentation (K-Ind). Comparison between K-Ind and K-Ic for the six high-strength rail steels suggests that the current indentation testing method can successfully rank the six high-strength rail steels for their fracture toughness.