Modeling the Influence of Microstructure in Rolling Contact Fatigue

Abstract

Crack nucleation, first spall generation, and spall growth in rolling contact fatigue (RCF) are known to be highly sensitive to the heterogeneity of the microstructure. Yet the current state-of-the-art in the design of high performance bearing materials and microstructures is highly empirical requiring substantial lengthy experimental testing to validate the reliability and performance of these new materials and processes. We have laid the groundwork necessary to determine the influence of microstructure in RCF to aid in the development and processing of bearing steels. Microstructure attributes that may control the fatigue behavior are explicitly modeled in a 41xxx steel. The methodology is demonstrated by studying the role of an aluminum oxide inclusion embedded in a matrix of tempered martensite and retained austenite. The matrix is represented by crystal plasticity, which provides more realistic accumulations of localized plastic strains with cycling compare to homogenized J2 plasticity. As a demonstration of the approach, the relative influence of the volume fraction of retained austenite on RCF is evaluated.

Performance and Characterization of TWIP Steels for Automotive Applications

“…3. Displacive transformations, or twinning, as they are analogous, can be incorporated as additional slip systems [85][86][87][88] or through an alternative flow rule using the multiplicative decomposition of the deformation gradient that now includes three components: elastic, plastic, and a part representing the transformation or twinning [89][90][91]. When incorporated as additional slip systems, as has been done successfully by others for TWIP steels [27,28,34,85,87], the plastic velocity is modified; for example [85],…”

Work hardening response of M50-NiL case hardened bearing steel during shakedown in rolling contact fatigue

“…When the kinematic hardening material is subjected to a stress cycle with positive mean stress, the resistance to plastic deformation at the higher stress level increases progressively, while the resistance at the lower stress level decreases. This tends to promote fully reversed strain cycles with gradually reducing forward flow and ratcheting during rolling sliding contact 10 – 12. In contrast, either elastic–perfectly plastic behaviour or isotropic hardening produces a balanced stress cycle and an unbalanced non-fully reversed plastic strain cycle with ratcheting, which is a distinctly different behaviour 10 – 12.…”

“…10,11 High strength bearing steels typically exhibit kinematic hardening. 11,12 When the kinematic hardening material is subjected to a stress cycle with positive mean stress, the resistance to plastic deformation at the higher stress level increases progressively, while the resistance at the lower stress level decreases. This tends to promote fully reversed strain cycles with gradually reducing forward flow and ratcheting during rolling sliding contact.…”

“…This tends to promote fully reversed strain cycles with gradually reducing forward flow and ratcheting during rolling sliding contact. [10][11][12] In contrast, either elastic-perfectly plastic behaviour or isotropic hardening produces a balanced stress cycle and an unbalanced non-fully reversed plastic strain cycle with ratcheting, which is a distinctly different behaviour. [10][11][12] A combined model incorporating non-linear isotropic expansion with non-linear kinematic shift can be used to simulate elastic shakedown, plastic shakedown and ratcheting with non-linear strain accumulation, depending on the model parameters chosen.…”

“…The shakedown limit is a function of the material's cyclic shear yield strength, constitutive relations and shape of the contact area 10 10,11. High strength bearing steels typically exhibit kinematic hardening 11 11,12. When the kinematic hardening material is subjected to a stress cycle with positive mean stress, the resistance to plastic deformation at the higher stress level increases progressively, while the resistance at the lower stress level decreases.…”