Noriyuki Tsushima

Influence of Surface Roughness Skewness on Rolling Contact Fatigue Life

Rolling element bearings operating under mixed or boundary lubrication conditions experience a higher metallic contact ratio (MCR) between the surfaces, and a corresponding decrease in rolling contact fatigue life. This paper evaluates the effects of randomly distributed small indentations, or pits, on the lubricating properties when operating under these mixed or boundary lubrication conditions. Rings and needle rollers were textured with randomly distributed small indentations, or pits, for evaluation. Skewness (Sk) was used as a measure of surface finish to characterize the degree to which the material of these modified parts was above the mean line, a positive value, or below the mean line, a negative value. Fatigue life tests were conducted on these rolling elements, whose skewness ranged from −1.2 to −2.0, under mixed or boundary lubrication conditions. Test results showed rolling bearing fatigue life to increase with a decrease in skewness as related to the depth, width, and distribution of the sur...

Improvement of Rolling Bearing Fatigue Life Under Debris-Contaminated Lubrication by Decreasing the Crack Sensitivity of the Material

Rolling contact fatigue life under debris- (or foreign particle-) contaminated lubrication is less than one-tenth the life under non-contaminated lubrication when the contaminating debris is hard, large particles (0.1 mm). A small “crevasse-type” crack initiates at the forward or backward side of a debris Particle indentation and grows into fatigue flaking. The size of the initial crack can be described by a parameter of the material called “crack sensitivity” in this paper. Relation between heat treatment conditions and the crack sensitivity of the ball bearing steel was investigated. The heat treatment which decreased crack sensitivity increased rolling contact fatigue life significantly not only under debris contaminated lubrication but also under noncontaminated lubrication. Presented at the 36th Annual Meeting in Pittsburgh, Pennsylvania, May 11–14, 1981

Crack Propagation of Rolling Contact Fatigue in Ball Bearing Steel Due to Tensile Strain

Crack propagations or failure modes in rolling element bearings, which had been difficult to explain via conventional crack propagation mechanisms such as the orthogonal shear stress mechanism, were discussed from the viewpoint of a tensile strain mechanism. Contact stresses are compressive in three axes, whose values differ from each other; then strain can be tensile in one of these directions, acting at a right angle to the direction of maximum compressive stress. A crack is considered to propagate by this tensile strain. When contact stress is small, a crack produced by some cause can propagate by this elastic tensile strain. When contact stress is large, residual tensile strain is produced by plastic deformation, which can also influence the crack propagation. Several failure modes of rolling element bearings, which had been difficult to explain, were explained by tensile strain.

Improvement of Rolling Contact Fatigue Life of Carburized Tapered Roller Bearings

Amelioration de la resistance de fatigue de contact roulant des roulements a rouleaux coniques cementes

Investigation on the Fatigue Fracture of Core in Carburized Rollers of Bearings

Progress in rolling-contact fatigue life of bearing steels encourages the reduction in size of bearings. This can lead to situations in which the bearing suffers from excessive loading. Core fracture of carburized rollers of bearings by excessive loading was investigated. The higher the core hardness, the less the core fracture happens. The critical stress amplitude at the center of the core for the core fracture was obtained in relation to core hardness. Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference in San Diego, California, October 22–24, 1984

New steels now in use for automotive rolling element bearings

With the development of clean steels, the influence of retained austenite on the rolling contact fatigue (RCF) life has changed. Under clean oil lubrication, the favorable influence of retained austenite disappeared, Utilizing th is phenomenon, a long life material for high temperature was developed with the use of the element Si which improves the heat resistance of steel. With the continuous casting becoming common steel making process, alloying elements should better be minimized because they cause segregation. From this point of view, a medium carbon through hardening steel which has competing RCF life with SUJ2 was developed. Under debris contaminated lubrication, retained austenite has ever favorable effect on RCF life. For these reasons, surface modification is important. Long life bearings under debris contaminated lubrication were developed by carbonitriding a through hardening steel or a carburizing steel, respectively.

Application of X-ray Measurements to Rolling Bearing Technology

ABSTRACT As examples of the applications of X-ray diffraction measurements to rolling bearing technology, estimation of the applied load on failed bearings, estimation of the degree of fatigue for non-failed bearings and analysis of the fractured bearing surfaces are described. Because rolling bearing steels are heat-treated to high surface hardness and are subjected to high contact stresses during operation, the residual stress change during operation due to plastic deformation, and the change in half-height breadth due to plastic deformation or temperature rise during operation, are significantly large. X-ray measurements of the residual stress and half-height breadth on the raceways of used bearings or on the fracture surfaces of fractured bearings provide quantitative information on the operating conditions of the bearings.