Rolling Contact Fatigue (RCF) is a phenomenon that occurs in mechanical components relating to rolling/sliding contact, such as railways, gears, and bearings.[2] It is the result of the process of fatigue due to rolling/sliding contact.[2][3] The RCF process begins with cyclic loading of the material, which results in fatigue damage that can be observed in crack-like flaws, like white etching cracks.[2] These flaws can grow into larger cracks under further loading, potentially leading to fractures.[2][4]
In railways, for example, when the train wheel rolls on the rail, creating a small contact patch that leads to very high contact pressure between the rail and wheel.[2] Over time, the repeated passing of wheels with high contact pressures can cause the formation of crack-like flaws that becomes small cracks.[2] These cracks can grow and sometimes join, leading to either surface spalling or rail break, which can cause serious accidents, including derailments.[2][4]
RCF is a major concern for railways worldwide and can take various forms depending on the location of the crack and its appearance.[2] It is also a significant cause of failure in components subjected to rolling or rolling/sliding contacts, such as rolling-contact bearings, gears, and cam/tappet arrangements.[5] The alternating stress field in RCF can lead to material removal, varying from micro- and macro-pitting in conventional bearing steels to delamination in hybrid ceramics and overlay coatings.[5]
Testing for RCF involves several methods, each designed to simulate the conditions that cause RCF in a controlled environment. Here are some of the methods used:
Twin-Disc Stands: This method uses two discs to simulate the wear the occur for rails and wheels.
Scaled RCF Tests: These tests use two discs of different diameters.[6]
Three-Ball-on-Rod Tester: This is an economical RCF proof of concept test. It is performed to evaluate the influence of heat treatment, material, lubricant, and coatings on fatigue life.[6]
Lundberg-Palmgren Theory and ISO 281 Based Method: This method evaluates RCF reliability considering the contact load, the geometric parameters of contact pairs, the oscillation amplitude, the RCF reliability, and the material properties.[7]
↑Curd, M. E.; Burnett, T. L.; Fellowes, J.; Donoghue, J.; Yan, P.; Withers, P. J. (2019-08-01). "The heterogenous distribution of white etching matter (WEM) around subsurface cracks in bearing steels". Acta Materialia174: 300–309. doi:10.1016/j.actamat.2019.05.052. ISSN1359-6454. Bibcode: 2019AcMat.174..300C.