INVESTIGATION INTO THE FATIGUE AND FRACTURE TOUGHNESS -BEHAVIOUR OF HAZ IN RAIL WELDNIENTS

Abstract

The fatigue crack growth and fracture toughness behaviour in the heat' .effected zone (HAZ) of thermit welded medium manganese rail steel, has been investigated. Experiments were carried out on specimens taken out from both head and web portion of the HAZ. Hardness and tensile properties have also been investigated. It has been observed that the HAZ of medium manganese thermit weldment is having higher yield and tensile strength lower crack growth rates in the AK range 15-4.0 MPa lm, and higher fracture toughness values (Kq) as compared to the unwelded base material of the same grade rail steel. Fracture toughness (K al values for HAZ have also been found to be higher as compared to that of many other grades of rail steels. A fracture mechanics model has been developed satisfactorily for fatigue life prediction of full section rail component having transverse head crack.