Mixed mode fracture toughness of R260Mn rail steel using Compact Tension Shear specimens

Being able to describe the fracture condition of a railway rail, after a fatigue crack has initiated, is crucial for safety assessment. Rails are loaded in mixed mode. This paper concerns an experimental investigation into the mixed-mode fracture toughness of used R260Mn rail steel. Fracture toughness experiments are carried out using compact tension shear specimens. This setup allows for testing fracture in mixed mode load condition (Mode-I and Mode-II). Results are compared in terms of maximum equivalent and maximum Mode-I fracture toughness. Contrary to the commonly adopted mixed mode failure criterion of Richard (Richard et al. (2004)) it appears that mixed mode failure is best described by the maximum Mode-I stress intensity factor component for the steel grade of study. The average fracture toughness of 51 MPa √m is obtained, for 10 mm thick specimens.