Kikuo Maeda

Flaking failure in rolling contact fatigue caused by indentations on mating surface (I): Reproduction of flaking failure accompanied by cracks extending bi-directionally relative to the load-movement

The crack growth in rolling contact fatigue has been investigated with a newly devised testing rig. A surface crack normally extends in the direction of the load-movement, and flaking failures accompanied by cracks extending in the direction opposite to the load-movement are rarely observed. However, in some situations, cracks extending in the opposite direction appear with an as not as yet clarified mechanism. In this study, a double-roller type rolling contact fatigue testing rig has been devised to reproduce the opposite-direction crack growth. Equally spaced artificial indentations are marked on the surface of one roller, while the other roller surface is defect-free. In that set-up, a flaking accompanied by cracks extending bi-directionally to the load-movement almost always occurs on the defect-free roller surface. The appearance of the flaking is consistent throughout the tests, but the cycles to failure vary according to test conditions such as (1) contact load, (2) additional tangential force between the rollers, (3) the number of artificial indentations, (4) whether the defect-free roller is operated as the driver or the follower, (5) rotational speed, and (6) size of artificial indentations.

The inclination of cracking in the peeling failure of a ball bearing steel and its relation to the inclination of the principal residual stress

Abstract Peeling is a mode of surface fatigue failure which is produced by rolling contact under specific conditions. X-ray measurements of the residual stress on a peeled surface using the 0–45° method revealed that the stress values in the rolling direction and in the direction opposite to rolling were different, i.e. 2θ−sin2ψ figures for the two measuring directions do not coincide and no linear relation exists between 2θ and sin2ψ. The relation between the inclination of cracking in peeling failure and the residual stress state was investigated by the integral method. The inclination of cracking is explained by the residual tensile stress acting perpendicularly to the principal residual compressive stress.

Flaking failure in rolling contact fatigue caused by indentations on mating surface (III): Mechanism of crack growth in the direction opposite to the load-movement

In rolling contact fatigue, we have discovered that a flaking failure accompanied by cracks extending bi-directionally relative to the load-movement occurs on a defect-free surface due to the influence of indentations on a mating surface. We have also demonstrated, using stress analysis, the initiation of incipient cracks in the subsurface region resulting from indentations on the mating surface. In the present study, we focus on the stage of crack extension in the direction opposite to the load-movement. Firstly, mode II fatigue crack growth properties are investigated by conducting mode II fatigue testing, which has been previously presented. Subsequently, stress intensity factors at a subsurface crack are calculated by using a finite element method for the case of an indentation on the mating surface moving through the contact area. In this calculation, the configuration of the modeled crack is very similar to cracks actually observed. Based on the results of both the stress analysis and the cracking seen in actual tests, the mechanism for the development of opposite-directional cracking is proposed to be a mode II extension of an incipient subsurface crack.

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.

New retainer material for high speed and high temperature cylindrical roller bearing

Cylindrical roller bearings are being developed which can operate over 300°C and greater than three million DN for innovative gas-generators. Under such severe conditions, it is necessary for retainers to be frictionless, lightweight and strong. After preliminary testing, SiC particle reinforced aluminum alloy composite appeared to have good friction and wear properties. Its specific gravity is about one-third of the present material in use, silver-coated SAE4340. In the course of the study, two different friction and wear tests were conducted to investigate the optimum volume fraction of SiC. The results indicated that the most efficient volume fraction was 20vol%. The tensile strength of Al-20vol%SiC was about 140MPa at 300°C. Based on the results of FEM analysis, 140MPa is considered sufficient to endure any stress concentration caused by tensile hoop stresses up to four million DN. Presented at the 54th Annual Meeting Las Vegas, Nevada May 23–27, 1999