Plastic Flow in Rollers Loaded above the Yield Point

A Multiscale Overview of Modelling Rolling Cyclic Fatigue in Bearing Elements

During service, bearing components experience rolling cyclic fatigue (RCF), resulting in subsurface plasticity and decay of the parent microstructure. The accumulation of micro strains spans billions of rolling cycles, resulting in the continuous evolution of the bearing steel microstructure. The bearing steel composition, non-metallic inclusions, continuously evolving residual stresses, and substantial work hardening, followed by subsurface softening, create further complications in modelling bearing steel at different length scales. The current study presents a multiscale overview of modelling RCF in terms of plastic deformation and the corresponding microstructural alterations. This article investigates previous models to predict microstructural alterations and material hardening approaches widely adopted to mimic the cyclic hardening response of the evolved bearing steel microstructure. This review presents state-of-the-art, relevant reviews in terms of this subject and provides a robust academic critique to enhance the understanding of the elastoplastic response of bearing steel under non-proportional loadings, damage evolution, and the formation mechanics of microstructural alterations, leading to the increased fatigue life of bearing components. It is suggested that a multidisciplinary approach at various length scales is required to fully understand the micromechanical and metallurgical response of bearing steels widely used in industry. This review will make significant contributions to novel design methodologies and improved product design specifications to deliver the durability and reliability of bearing elements.

Elastic Hysteresis and a Catastrophic Wear Mechanism for Polymers

It is now accepted that hysteresis loss in sub-surface regions plays a major role in rolling friction; however, its influence upon wear has received little consideration. Similarly, the temperatures generated by frictional heating have been analysed only in terms of those mechanisms of sliding friction that result in heat generation at the surface. It is shown that hysteresis loss can cause significant increases in the sub-surface temperatures of rolling bodies with catastrophic consequences for their wear and damage. This mechanism of failure may apply to a wide range of engineering situations including nylon cams, automobile and aircraft tyres and the fibre-filled supercalender rolls used in paper mills.

Residual stresses in rolling contact

The paper reports an experimental investigation into the residual strsses induced into cylndrical discs by the action of rolling-contact loads sufficiently high to cause some plastic deformation in the near-surface layers.

A general method is first described for finding both circumferential and axial components of residual stress in cylindrical bodies in circumstances where the stresses vary with the radial co-ordinate only. This method is believed to be an improvement on previous methods for separating the two components of residual stress, particularly where only specimens of restricted length are available. For example, the method could be applied to thick-walled tubes.

Measurements have been made of the residual stresses due to rolling contact, in pure rolling and in combined rolling and sliding. In all cases both components of residual stress were compressive and reached a maximum value below the surface at about the depth of the maximum Hertz shear stress. The measured residual stresses in the sub-surface region were roughly in agreement with the theoretical predictions of Merwin, Johnson, and Jefferis.

A subsidiary peak of compressive stress was found at the surface itself. Neither the surface nor the subsurface stresses were found to be greatly influenced by the presence of friction forces when sliding accompanied rolling.