Forensic Analysis of Surface Indentations in Rolling Contact

The presence of debris particles in rolling element bearings can pose a major risk for premature fatigue damage on modern bearing components made from clean steels. A clear understanding of surface indentation characteristics and the associated particle that inflicted the indentation is essential for assessing the impact of surface dents on bearing fatigue life performance and for prevention of surface damage from harmful particles. A method for characterizing indentations on contact surfaces is proposed in this paper. The method allows for virtual regeneration of indentations on bearing raceway surfaces based on pseudorandom surface mapping of limited sample areas. The regenerated surface indentations maintain statistical signatures identical to the mapped samples and can be used directly as the input for high-fidelity fatigue life assessments. A set of forensic tools was developed from extensive finite element analysis (FEA) modeling on surface indentation processes and from simple particle entrainment geometry. These tools allow inference of the size of each and every particle responsible for surface indentations without requiring the full knowledge of the material properties and frictional conditions of the particles and counter-faces. The current results presented herein agree with both published test results and prior art modeling results. In addition, examples of applications are discussed to illustrate the usefulness of the tools.