Fatigue Limit Stress — A New and Superior Criterion for Life Rating of Rolling Bearing Materials

In this work is indicated how it could be possible to evaluate the limit stress of the thermo-elastic phase of deformation by thermo-analysing the surface of the specimen during a static traction test. Adding the temperature curve measured on a small area of the surface (the hottest) to the classic stress-strain curve, it is possible to evaluate a limit temperature T0 coincident with the beginning of the non linear trend of the curve. The corresponding stress value is coincident with the fatigue limit of the analyzed component. As an example, the results of traction tests performed on two notched specimens, where the change of linearity in the temperature curve during static traction test was evident, are reported.

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A preliminary assessment of high speed tool steels manufactured from powder for rolling bearing materials

Wear ◽

10.1016/0043-1648(75)90061-7 ◽

1975 ◽

Vol 34 (2) ◽

pp. 149-158 ◽

Cited By ~ 4

Author(s):

D. Scott ◽

J. Blackwell

Keyword(s):

High Speed ◽

Rolling Bearing ◽

Tool Steels ◽

Preliminary Assessment ◽

Bearing Materials

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Influence of Mean Stress on the Fatigue Behavior of 304L SS in Air and PWR Water

Volume 1: Codes and Standards ◽

10.1115/pvp2005-71064 ◽

2005 ◽

Cited By ~ 9

Author(s):

H. D. Solomon ◽

C. Amzallag ◽

A. J. Vallee ◽

R. E. De Lair

Keyword(s):

Fatigue Limit ◽

Fatigue Behavior ◽

Secondary Hardening ◽

304L Stainless Steel ◽

Mean Stress ◽

Cycle Fatigue ◽

Different Temperatures ◽

Limit Stress ◽

Conventional Models ◽

Stress Models

Load-controlled experiments on 304L stainless steel were run in Air and PWR water, at 150°C and 300°C, with and without a mean stress of 100MPa. These experiments were run to determine the influence of temperature, environment, and mean stress on the 107 Cycle Fatigue Limit stress amplitude. A 100MPa mean stress was found to have different effects at the different temperatures and environments. In contrast to all the conventional models used to describe the effects of mean stress, when the testing was done at 300°C (for both air and PWR water), a 100MPa mean stress was found to raise the 107 Cycle Fatigue Limit relative to that observed without a mean stress. This was ascribed to the effect of the hardening due to the initial straining and to secondary hardening, both of which are more pronounced at 300°C than at 150°C. The increased initial and secondary hardening resulted in the development of less non-elastic strain, thereby improving the fatigue behavior. In PWR water at 150°C, a 100MPa mean stress reduced the 107 Cycle Fatigue Limit by more than that predicted by conventional mean stress models, but in air at 150°C, the decrease in the endurance limit was more in keeping with the predictions of these models. This difference was ascribed to the effect of the PWR water, in the absence of significant initial straining and secondary hardening.

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A Micromechanical Fatigue Limit Stress Model of Fiber-Reinforced Ceramic-Matrix Composites under Stochastic Overloading Stress

Materials ◽

10.3390/ma13153304 ◽

2020 ◽

Vol 13 (15) ◽

pp. 3304

Author(s):

Longbiao Li

Keyword(s):

Fatigue Life ◽

Fatigue Limit ◽

Stress Level ◽

Ceramic Matrix Composites ◽

Fatigue Loading ◽

Cyclic Fatigue ◽

Fiber Reinforced ◽

Cycle Number ◽

Fiber Fraction ◽

Limit Stress

Fatigue limit stress is a key design parameter for the structure fatigue design of composite materials. In this paper, a micromechanical fatigue limit stress model of fiber-reinforced ceramic-matrix composites (CMCs) subjected to stochastic overloading stress is developed. The fatigue limit stress of different carbon fiber-reinforced silicon carbide (C/SiC) composites (i.e., unidirectional (UD), cross-ply (CP), 2D, 2.5D, and 3D C/SiC) is predicted based on the micromechanical fatigue damage models and fatigue failure criterion. Under cyclic fatigue loading, the fatigue damage and fracture under stochastic overloading stress at different applied cycle numbers are characterized using two parameters of fatigue life decreasing rate and broken fiber fraction. The relationships between the fatigue life decreasing rate, stochastic overloading stress level and corresponding occurrence applied cycle number, and broken fiber fraction are analyzed. Under the same stochastic overloading stress level, the fatigue life decreasing rate increases with the occurrence applied cycle of stochastic overloading, and thus, is the highest for the cross-ply C/SiC composite and lowest for the 2.5D C/SiC composite. Among the UD, 2D, and 3D C/SiC composites, at the initial stage of cyclic fatigue loading, under the same stochastic overloading stress, the fatigue life decreasing rate of the 3D C/SiC is the highest; however, with the increasing applied cycle number, the fatigue life decreasing rate of the UD C/SiC composite is the highest. The broken fiber fraction increases when stochastic overloading stress occurs, and the difference of the broken fiber fraction between the fatigue limit stress and stochastic overloading stress level increases with the occurrence applied cycle.

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