The detrimental influence of inclusions on rolling contact fatigue behaviour of bearing steel is well known and empirically described. Yet only a few publications exist where the effect of inclusions is investigated analytically. This paper presents a new method to describe the influence of inclusions based on a mechanical analysis.

From this analysis some general effects of inclusions on material stress and behaviour in rolling contact fatigue were concluded. The actual “notch effect” of inclusions is qualitatively independent on their specific properties, even if they are more pliable or stiffer than the matrix. Only the amount of the notch effect is — to a certain extent — dependent on their respective properties. Many discrepancies between classical theory of Hertzian contact and damage analysis of rolling element bearings can be explained by this analysis.

The correct appraise of compressive residual stresses in rolling contact fatigue is strongly bound to the consideration of inclusions. It is shown that compressive residual stresses have the greatest benefit if they are about 15% of the applied Hertzian pressure. Exceeding this value may be detrimental.

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