Automated residual stress quality management of aerospace bearings

Bearings are a critical part of a modern aircraft propulsion system; everything rotates about a bearing. In an effort to minimize size, reduce weight, and increase load carrying capability, current bearing technology makes extensive use of carburized steels such as M50NiL or Pyrowear™ 675 for inner and outer rings and occasionally rolling elements. The carburizing process produces a hard, metallurgically graded microstructure from the surface down to the fracture tough core thus creating a residual stress profile that is advantageous to minimizing crack growth. Subsequent metal removal processing via grinding and honing produce a large near surface compressive residual stress which further prevents surface crack formation. The resultant residual stress profiles from the various manufacturing processes have a significant impact on the performance of bearings. Today, residual stress measurements are contractually required for each production lot of a bearing component (inner and outer rings) as part of the quality management process. This is a significant burden on bearing suppliers and can add upwards of 1-2 weeks on product delivery. This program will develop a novel, automated residual stress measurement test system for quality management of bearing components.