Understanding the fatigue crack growth phenomenon in railheads requires a study of driving forces such as the crack tip opening and sliding displacements, under repeated rolling contact. Finite element simulations, allowing elastic-plastic deformation, and mixed-mode crack growth laws were utilized to demonstrate that the fatigue crack growth rates display a minimum after a finite amount of crack advance. These results have implications in designing strategies for optimum grinding or wear rates to limit fatigue crack growth, and thereby prolong rail life. During the simulations, the crack was allowed to advance, permitting residual deformations and stresses to be retained from cycle to cycle. The opening and closure of crack surfaces, under forward and reverse slip and stick conditions were monitored. Normal pressures of 1500 MPa and 2000 MPa, along with shear traction ratios in the range of -0.4 to 0.4 were investigated for a varying crack size of 3 to 15 mm. An interesting finding was that the crack tip opening displacements decreased while the crack tip sliding displacements increased with increasing crack length.
The stress–strain history and the crack initiation lives of bainitic and head‐hardened pearlitic rail steels were determined under rolling contact loading by implementing the semi‐analytical Jiang–Sehitoglu rolling contact model that incorporates both ratchetting and multiaxial fatigue damage. The calculations revealed that the bainitic steel withstands higher loads than the pearlitic steel at low shear tractions, however; both materials behave in an increasingly similar manner as the shear tractions increase. Furthermore, maximum damage occurs in both steels when ratchetting and fatigue damage coincide on the surface. In addition to shedding light on the rolling contact fatigue (RCF) performance of bainitic and pearlitic rail steels, the current work also establishes a methodology for the realistic prediction of crack initiation under RCF.
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