IN-SITU CRACK PROPAGATION OF PEARLITIC RAIL STEEL SUBJECTED TO LARGE SHEAR DEFORMATION

Paper i proceeding, 2025

A first attempt was made to characterise crack growth and paths in relation to the aligned microstructure in axial-torsion pre-deformed pearlitic rail steel. Small notched tensile specimens in two orientations were extracted from pre-deformed and undeformed material. Pulsating loading was applied in-situ in a scanning electron microscope at a maximum stress of 125% of the yield stress (R = 0.1). Initial plastic straining occurred, with larger strains in undeformed material, followed by ratchetting to failure. The fracture surfaces showed partly ductile, partly brittle trans-granular cleavage, and the crack propagation in the last loading cycle differed markedly between the material states.