Abstract
Rolling bearing elements develop structural changes during rolling contact fatigue (RCF) along with the non-proportional stress histories, evolved residual stresses and extensive work hardening. Considerable work has been reported in the past few decades to model bearing material hardening response under RCF; however, they are mainly based on torsion testing or uniaxial compression testing data. An effort has been made here to model the RCF loading on a standard AISI 52100 bearing steel with the help of a 3D Finite Element Model (FEM) which employs a semi-empirical approach to mimic the material hardening response evolved during cyclic loadings. Standard bearing balls were tested in a rotary tribometer where pure rolling cycles were simulated in a 4-ball configuration. The localised material properties were derived from post-experimental subsurface analysis with the help of nanoindentation in conjunction with the expanding cavity model. These constitutive properties were used as input cyclic hardening parameters for FEM. Simulation results have revealed that the simplistic power-law hardening model based on monotonic compression test underpredicts the residual generation, whereas the semi-empirical approach employed in current study corroborated well with the experimental findings from current research work as well as literature cited. The presence of high compressive residual stresses, evolved over millions of RCF cycles, showed a significant reduction of maximum Mises stress, predicting significant improvement in fatigue life. Moreover, the predicted evolved flow stresses are comparable with the progression of subsurface structural changes and be extended to develop numerical models for microstructural alterations.Graphic
Highlights
Rolling element bearings are designed to enable smooth rotation during service
It should be noted the non-linear isotropic and kinematic hardening (NIKH) residual stress profile presented in Fig. 10 corresponds to a test with 37.5 million rolling contact fatigue (RCF) cycles at 3980 MPa maximum contact stress so it could fall somewhere between 10 million and 100 million RS profiles obtained from deep groove ball bearings (DGBB) test
A comprehensive finite element model has been developed for evolved bearing material elastoplastic response, prediction of plasticity-induced deep zone residual stresses and subsequent effects on microstructure
Summary
Pmax Maximum Hertzian Pressure σy Yield/flow stress n Strain hardening index F Axial load FR Resultant/Normal load HIT Instrumentation hardness A Area of Indenter HV Vickers hardness α Effective cone angle E Young Modulus S Stress vector q Back stress −pl Accumulated plastic strains yo Instantaneous yield strength Q Isotropic hardening z/b Normalised centreline depth β Rate of isotropic expansion q′ Increment in back stress C Initial kinematic modulus γ Rate of decreasing C (∆σy)max Maximum change in yield surface NIKH Non-linear isotropic kinematic hardening z Centreline depth from contact track S12 Orthogonal shear stress PEEQ Equivalent plastic strains. 1 3 a Semi-major axis b Semi-minor axis σ22 Residual stress in circumferential direction RS Mises residual stress Smax Maximum amplitude of alternating stress Smin Minimum amplitude of alternating stress
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