Papers by Keyword: Rolling Contact Fatigue

Abstract: Bearings have been used in various environments. Recently, small and light-weight bearings are developed in order to downsize mechanical components. Polymer bearings, such as PEEK (Poly-Ether-Ether-Ketone), PTFE (Poly-Tetra Fluoro-Ethylene) and PPS (Poly-Phenylene-Sulfide-Resin), are designed because of advantages of light weight, high corrosion resistance and self-lubricating. However, industrial design standards of these bearings have not been established yet, i.e., the relation between working conditions, shape, geometry, and lives of bearing components under RCF (Rolling Contact Fatigue) is not fully understood as well as crack propagation, wear and/or failure. In this study, we focused on the manufacture process of groove curvature decreasing contact stress, and observed cracks and flaking failures on groove surfaces and cross sections. Based on these observations, we investigated the relation between the groove geometry and lives of all-PEEK thrust bearings in water.

Abstract: One important method to improve the material properties is refinement of the prior austenite grain size. Repeated quenching is used as a grain refinement method. In the present work, samples of SUJ2 steel were furnace quenched once and thrice in order to investigate the effect of repeated quenching on rolling contact fatigue (RCF) strength. After the RCF tests, maicrostructure observations, Vickers hardness and retained austenite measurements, RCF life evaluation using the Weibull distribution were carried out. It was found that the dispersion of the life population was reduced by repeatedly quenching.

Abstract: Particle analysis methodology is presented, together with the morphology of the wear debris formed during rolling contact fatigue. Wear particles are characterised by their surface topography and in terms of wear mechanism. Rail-wheel materials are subjected to severe plastic deformation as the contact loading progresses, which contributes to a mechanism of major damage in head-hardened rail steel. Most of the current methodologies involve sectioning of the rail-wheel discs to trace material damage phenomena such as crack propagation and plastic strain accumulation. This paper proposes methodology to analyse the development of the plastically deformed layer by sectioning wear particles using the focussed ion beam (FIB) milling method. Moreover, it highlights the processes of oxidation and rail surface delamination during unlubricated rolling contact fatigue.

Abstract: The operational degradation of surface layers due to a rolling contact process was simulated for Hadfield steel by a special testing rig. A specific limited state based on cumulative depletion of plasticity was achieved.Precise evaluation of the surface layer's mechanical parameters is necessary for a service life prediction. Very low depth of localized dislocation hardening process doesn ́t allow the standard mechanical testing. The comparative instrumented indentation tests using Vickers and cylindrical indenter were used for evaluation of defined stage of surface degradation process. The intensity and reach of deformation hardening are partially limiting for particular methodology. The yield stress of surface layers was estimated according to an analytical model of uniaxial vs. indentation plastic flow ratio.

Abstract: Due to the advantage on low coefficient and self-lubricant, PPS races-PTFE retainer hybrid polymer bearings can offer better service performance under certain condition. In our previous study, the relationship between friction coefficient and rotation speed was investigated, and formation of black layer was found. In the present study, EPMA was introduced to investigate the component and thickness of the black layers. Based on the observations, the relationship between friction coefficient, solid lubricant layer and thrust load was also discussed.

Abstract: Presented paper deals with ratcheting prediction in the field of line rolling contact. The main aim is to simulate the wear process due to the contact fatigue on inductively hardened sample of R7T material. For the stated purposes, the authors have used the wear model based on shear band cracking mechanism and non-linear kinematic and isotropic hardening rule of Chaboche and Lemaitre. Obtained results are subsequently compared with experimental data as well as with metallographic analysis.

Abstract: A single-ball RCF testing machine was used in order to investigate crack initiation of SUJ2 material at early stage of fatigue. This machine enables observation of a full cross section by sectioning the specimen only once. The RCF tests were carried out under a Hertzian stress of 5.3 GPa, at 3000 rpm. All of the cracks initiated from non-metallic inclusions on 300 mm² sized area were counted, and the relation between the number of cracks and their initiation depths was drawn. Furthermore subsurface shear stress distribution was calculated. Empirical data of the crack distributions and subsurface stress distribution was compared. It was found that the crack starts growing during 3.3×10⁴ - 1.0×10⁵ cycles by the subsurface shear stress.

Abstract: Rolling contact fatigue twin-disc tests were performed on rail/wheel steels from Spanish high velocity trains (AVE). Residual stress profiles were determined using X-ray diffraction before and after cyclic loading. The evolution of residual stress profiles, due to cyclic loading, was analysed in order to study how they affect the rolling contact fatigue behaviour of these materials. This study is included in a major project where other related phenomena and materials’ properties have been studied.

Abstract: In our previous studies, a new surface modification method by combination of ceramic coating and heat treatment, named “substrate quenching after coating” was developed. The thrust type rolling contact fatigue tests were carried out for TiN coated steels and CrAlN coated steels processed by substrate quenching after coating, and the effects of the type of ceramic coating (TiN or CrAlN) and the quenching methods (by furnace quenching or by laser quenching) on the flaking initiation life were investigated. For the specimens quenched by furnace, the flaking life of CrAlN coated specimen was longer than that of TiN coated specimen. This reason could be explained by the difference of the oxidization of CrAlN and TiN in their furnace quenching process. For CrAlN coated specimens, the flaking life of the specimens quenched by laser was longer than that of the specimens quenched by furnace. This reason could be explained by the difference of the process time of the furnace quenching and the laser quenching. It is considered that laser quenching after coating could be an effective way to improve the flaking initiation life under rolling contact fatigue.

Abstract: There were two procedure about surface failure in rolling contact fatigue (RCF), wear and crack propagation. In our previous study, it was concluded that the main reason for PPS bearings failure in water was flaking due to surface crack propagation. The relationship between wear loss, rotation speed and thrust load of PPS bearings under RCF in water was investigated. In this study, the detailed surface profiles under heavy load were studied by using both LCM and two-dimensional measurement sensor to study the process of flaking failure.