Case study: The effect of running distance on the microstructure and properties of railroad axle bearings

Fatigue life prediction of high‐speed train bearings based on the generalized linear cumulative damage theory

“…Moreover, the elongations ( δ ) of the bearing steel with 0 km, 1.2 million km, and 2.4 million km are 1.85% and 1.31%, and 1.10%, respectively. It is noticed that the strength and plasticity of the bearing steel decrease with improving the operating mileage of high‐speed train (as shown in Figure 3B), which are further verified by Ma et al and Guo et al for high‐speed train bearings 17,18 …”

“…We can get where D cr is the critical fatigue damage. Contact stress σ = 900 MPa would be marked as the critical residual strength R (n) = 0 in this study through the line load spectrum test and finite element analysis of high‐speed train bearings 17 . Additionally, the residual strength of high‐speed train bearing steel by Guo et al 17 and Ma et al 18 are also displayed in Figure 8A.…”

Statistical analysis on rolling contact fatigue in railroad axle bearing steel

“…It is broadly accepted that rolling contact fatigue (RCF) is the primary mechanism responsible for the failure of most bearings. Fatigue cracking may initiate from either the contact surface or subsurface, and cracks can be resulted from contaminated lubricants, or foreign particles entrained in the moving elements of the bearing produce wear or denting of the bearing surfaces . Several types of test methods are applied to evaluate the RCF of bearings, including the four‐ball–rolling tester, the five‐ball–rolling tester, the v‐groove/ball tester, the rolling‐element‐on flat tester and the three‐contact‐point tester .…”

“…Voskamp mentioned that the bearing steel would lead to a steady‐state condition after 1000 to 2000 revolutions. Guo studied bearing steels at different operation distances, and observed clear grain refinement and an inhomogeneous hardness distribution. Strengthening mechanisms in martensitic steel usually involve solid solution, dislocation, grain boundary, and precipitation strengthening .…”

“…Fatigue cracking may initiate from either the contact surface or subsurface, and cracks can be resulted from contaminated lubricants, or foreign particles entrained in the moving elements of the bearing produce wear or denting of the bearing surfaces. 1 Several types of test methods are applied to evaluate the RCF of bearings, including the four-ball-rolling tester, 2 the five-ball-rolling tester, 3 the v-groove/ball tester, 4 the rolling-element-on flat tester 5 Nomenclature: U drive , speed of drive roller; U driven , speed of driven roller; E 1 , Young's modulus of driven roller; E 2 , Young's modulus of drive roller; ν 1 , Poisson ratios of driven roller; ν 2 , Poisson ratios of drive roller; R 1 , radius of driven roller; R 2 , radius of drive roller; P, load of contact line; L, length of contact line; l, crack length; l 1 , crack extension length after one cycle; r, maximum half-width; h 0 , crack opening displacement; h 1 , crack opening displacement after one cycle; a, angle between the direction of frictional force and crack; _ α, angular opening velocity of crack; α 0 , crack growth angle; γ, deflection angle; d 1 , crack depth; d max , maximum crack depth; μ, friction coefficient; p(x), hydrodynamic pressure; η, kinematic viscosity of bearing grease; ρ, density of grease; F , resultant force per unit length; K I , Mode I stress intensity factor; K II , Mode II stress intensity factor; τ max , Maximum shear stress; K τ (γ), stress intensity factor of shear stress; K σ (γ), stress intensity factor of tensile stress; ΔK σth , threshold of stress intensity factor; σ ys , 0.2% offset yield stress; w, average grain size and the three-contact-point tester. 6 Materials with distinct constitutive behaviour were considered by different groups [7][8][9][10] to connect the rolling behaviour with mechanical properties, in particular how the hardening behaviour of the materials would affect the RCF of those bearings.…”