Influence of white etching layer on rolling contact behavior at wheel-rail interface

Abstract

The existence of narrow and brittle white etching layers (WELs) on the rail surface is often linked with the formation of rail defects such as squats and studs, which play the key roles in rail surface degradation and tribological performance. In the present study, a systematic investigation on stress/strain distribution and fatigue life of the WEL during wheel-rail rolling contact was conducted based on a numerical model considering the realistic wheel geometry. This is the first study considering the influence of rail materials, loading pressure, frictional condition, WEL geometry (a/b), and slip ratio (Sr) in the practical service conditions at the same time. The results revealed much higher residual stress in WEL than in rail matrix. Stress changes along the rail depth matched with the previously reported microstructure evolutions. The current work revealed that the maximum difference in contact stress between the wheel passages of rail matrix and the WEL region (noted as stress variation) rises with the increase of loading pressure, the value of a/b, and Sr; but drops with the friction coefficient (μ). In addition, a critical length-depth ratio of 5 for a/b has been found. The fatigue parameter, FP, of the WEL decreased quickly with the length-depth ratio when it was less than 5 and then increased slightly when it was larger than 5. This study also revealed that the fatigue life of the WEL was reduced for high strength head hardened (HH) rail compared with standard carbon (SC) rail.

Formation Mechanisms and Crack Propagation Behaviors of White Etching Layers and Brown Etching Layers on Raceways of Failure Bearings

“…The hardness increase may also be caused by severe plastic deformation (work hardening effect), but the flow structure only appears in some local areas (in Figure 5d), which cannot explain the high hardness values of the entire BEL regions. Interestingly, on rail surfaces, the BEL cannot exist alone [1,14,43] and is generally located in the middle of the WEL and the matrix [7,8], which is opposite to the existence alone of the BEL in this study. However, the feature of high hardness values of the BEL on bearing raceways is similar to the WEL of railway surfaces.…”

“…A schematic (Figure 7) shows the differences in the structure of the surface layer of the tw samples. alone [1,14,43] and is generally located in the middle of the WEL and the matrix [7,8 which is opposite to the existence alone of the BEL in this study. However, the feature o high hardness values of the BEL on bearing raceways is similar to the WEL of railwa surfaces.…”

“…Even so, there is still no unified formation mechanism that can be widely accepted. The accepted formation mechanisms of the WEL and BEL are stress-induced effect [7,[13][14][15], thermal-indued effect [16][17][18], or the interaction of the two effects [9]. However, these explanations are responsible for their characteristic results.…”

Influence of White Etching Bands Formation on Integrity of Rolling Element Bearings

“…The study of rolling contact fatigue (RCF) induced subsurface microstructure alterations in bearing steels has been investigated for decades [1][2][3], amongst which 'white etching matters' has been a common feature in several microstructural alterations including white etching layer (WEL) [4], white etching crack (WEC) , butterflies and white etching bands (WEBs) [1,3,5,6]. Of the features, WECs and butterflies are 'localized' microstructural alterations.…”

Homogenization based macroscopic model of phase transformations and cyclic plasticity in pearlitic steel

“…Simulations of local heating in railway wheels caused by braking are another example, cf. [21][22][23][24][25][26]. Even though the prime focus may differ, common for all these examples is that the material modeling is one of the most challenging and crucial aspects for the fidelity of the simulation results.…”