Nondestructive Measurement of Residual Stresses in Anti-Friction Bearings using Magnetic Methods

Higher performances from gas turbines by increasing turbine speeds, loads and temperature place increased emphasis on the operation and reliability of engine components such as bearings and gears. The fatigue lives of such components are severely reduced by the presence of residual tensile stresses, introduced by the grinding and finishing processes during component manufacture. There is acute need for nondestructive methods which can perform routine inspections of these components and detect these near-surface stresses reliably and accurately. Three different magnetic methods for the nondestructive measurement of residual stresses in rolling element bearings are proposed. These methods consist of the Barkhausen Noise Analysis (BNA, also called MBE for Magnetic Barkhausen Emission), the Magnetically Induced Velocity Change (MIVC) and the Stress Induced Magnetic Anisotropy (SMA) measurement techniques. These three methods along with other candidate technologies will be evaluated in the process of developing prototype instrumentation for stress measurement.