Research Projects

Aeroengine bearings are heavily loaded components that are subjected to Hertzian contact pressures greater than their uniaxial yield strength. Ultra-high-strength through-hardened bearing steels, such as AISI 52100 and M50, are the current material for aerospace bearings due to their high fatigue life and martensitic steel microstructure. However, the increasing demand for faster aircraft and vehicles requires stronger and tougher bearings. The residual stress distribution within the subsurface of these steels influences the intensity of plastic deformation in the subsurface, affecting the bearings' life. Introducing compressive residual stresses via surface heat-treatments and surface mechanical treatments can improve the fatigue life of bearings. Studying the effects of heat-treatment and shot-peening parameters on residual stress distribution in bearing steels can optimize processing parameters for achieving a customized residual stress profile. Evaluating residual stresses in heat-treated and shot-peened bearing steels and measuring the evolution of residual stresses with fatigue cycles can lead to structural health monitoring of the bearings. This project systematically investigates residual stress evolution in bearing steels after various manufacturing processes, including industrially used heat-treatment cycles for through-hardened AISI 52100 and case-hardened AISI 8620 steels, shot peening on through-hardened steel, and shot peening on case-hardened steel. The effects of these parameters will be simulated using a Johnson-Cook constitutive model implemented on Commercial Finite Element Analysis software (ANSYS R20). High-cycle fatigue experiments will be conducted on heat-treated and shot-peened specimens to determine the effect of stress amplitude and cycles on residual stress relaation behavior.