An evaluation of the fatigue crack growth and fracture toughness characteristics of rail steels

Abstract

The fatigue crack growth and fracture toughness characteristics of six rail steels have been evaluated. The overall test program included tensile testing, the determination of the longitudinal residual stresses, fatigue crack growth tests, and static and dynamic fracture toughess determinations. In addition fatigue crack growth was studied in rail heads with the effects of residual stress taken into account. The six rails differed in processing histories as well as composition and consisted of a standard carbon rail, a fully heat-treated rail, two Cr-Mo rails, a Cr-V rail, and a head-hardened rail. With the exception of the head-hardened rail, residual tensile stresses were present in the head and base of all other rails. The residual stress in the head of the head-hardened rail was compressive which was beneficial to fatigue and fracture resistance in full section. The Cr-V steel exhibited the lowest level of fracture toughness. It was noted that as the tensile ductility increased there was also a general tendency for the fracture toughness to increase as well.