Fracture and Fatigue of High Hardness Bearing Steels Under Low Tensile Stresses

Tensile stresses in bearing components, particularly in rings, may be caused by conditions of manufacturing, mounting, or operation. During bearing operation, when a condition to cause tension is present, the stress cycle varies rapidly between compression when the Hertz contact stress is applied and tension when the contact stress has passed. Analysis of 14 bearing failures indicates that tensile stresses as low as 140 to 200 MPa (20 to 30 ksi) are sufficient to cause cracks to grow in fatigue. When tensile stresses drive the crack in a radial direction, fracture rather than spalling will occur.