Abstract
In order to demonstrate clearly the damaging mechanism on rail surfaces at the joint subjected to impact blows by train wheels, cyclic impact blow tests and low cycle fatigue tests have been performed using 0.75% C rail steel with different hardness valuse and microstructures.
The results are summarized as follows:
(1) Under cyclic impact blows, a cyclic softening occurs at an early deformation stage in tempered martensite, but only a hardening occurs following surface cracking afterward in pearlite.
(2) Under low cycle fatigue conditions, a cyclic softening at a small strain amplitude gives place to a hardening as the strain amplitude increases in pearlite, although only a cyclic softening occurs more extensively in tempered martensite.
(3) The fact that dislocation structures formed under cyclic impact blows correspond to the structural changes observed under cyclic plastic straining suggests that the fatigue behavior under impact blows can be roughly estimated using low cycle fatigue tests.
