GOALI/Collaborative Research: Reliable Prediction of Endurance Life of Ultra-High-Strength Aerospace Rolling-Element Bearings

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Rolling-element bearings are key precision components used for rotor support in nearly all machinery. The annual revenue associated with bearings is a substantial $50.5 billion worldwide. Future demands on high performance rotor support for advanced aircraft engines, wind turbines and high-speed rail require bearings to survive thousands of hours and consequently billions of Rolling Contact Fatigue (RCF) cycles under severe operating conditions. A new generation of high strength bearing steels with graded material properties has been designed to meet these challenges. Existing life prediction methodologies rely on empirical models dating back to the 1940s, resulting in a large discrepancy between observed and predicted life, for the new generation of materials. This Grant Opportunity for Academic Liaison with Industry (GOALI) collaborative researh project aims to predict reliable service life and structural integrity of new generation bearing materials based on novel experimental and computational procedures for understanding material degradation due to RCF at the micro and nanometer scale. The results will translate to the design of other components with large economic impact such as transmission gears, cams, railway wheels and tracks, and manufacturing tooling. This research is an effort to bring back an academic focus to manufacturing-related research to campuses and to better assist US industries. The project will contribute to the education and training of future manufacturing research workforce and leaders.This collaborative GOALI project involves developing a novel physics-based material-specific life prediction model rooted in fundamental understanding of local material properties of as-manufactured and RCF-affected materials from sub-micrometer/nanometer to macroscopic length scales. The project will develop: 1) quantifiable measures for subsurface graded material response as a function of load, temperature and RCF cycles; 2) computational approaches for understanding the influence of microstructural features on the material cyclic response, resultant stress and strain fields, and fatigue damage; and 3) a material-specific RCF life prediction methodology based on enhancements to the existing Lundberg-Palmgren empirical approach by the evolving elastic-plastic subsurface stress and strain fields. Methodologies for tracking RCF material damage in the giga-cycle regime will become available for reliable life prediction, which are of considerable importance with applications to broader areas of tribology and heterogeneous materials for future component design. Intellectual significance of the project comprises of two novel contributions: 1) it will aid development of a new material-specific RCF life prediction model, particularly beneficial to accelerated design of new bearing materials, and 2) it will result in a methodology to model cycle-specific material property evolution in rolling contacts, with direct relevance to design of gears, cams, railway wheels and tooling.