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Technical Paper

Application of X-Ray Measurement to Bearing Failure Analysis

X-ray measurement is a very useful tool for bearing failure analysis. Compressive residual stress is created under the bearing raceway if bearings are used under a contact stress higher than the critical value. Residual stress distribution measurement of a used bearing enables to presume contact stress in service. Half height breadth of diffracted X-rey also changes with the fatigue of the material. Therefore X-ray measurement may estimate the degree of fatigue of a used bearing. Fracture surface of a fractured bearing has sometimes a high tensile residual stress at the surface, from which we can presume the fracture toughness of the material and then calculate the fracture stress. X-RAY diffraction is a very useful tool for bearing failure analysis, because X-ray diffraction technique can detect sensitively macro and microscopic lattice changes of a surface layer of crystalline materials.
Technical Paper

Influence of Various Material Factors of One Percent Chromium Carburizing Steel Upon Rolling Contact Fatigue Life

Chromium and chromium-molybdenum carburizing steels are widely used for small- and medium- sized rolling bearings or gears, in Japan. Using a cylinder-to-ball type rolling contact fatigue rig, influence of various material factors such as chemical compositions, oxygen content, retained austenite and grain size in 1 % chromium carburizing steel was investigated. Life level of 1 % chromium steel has been increased gradually since 1968 when the test began. The increase in life level is mainly due to reduction in oxygen content by the improvement of steel-making technique. Manganese content increases the life and 1 % Cr steel with 1 % Mn has high reliable life. Prior austenite grain size does not seem to influence the rolling contact fatigue life.