Construction of Deep Contact Fatigue Curves for Surface-Hardened Gear Wheels

Abstract

Laws of fatigue resistance changes of surface-hardened toothed gears are established. It is shown that the main criterion of serviceability of gear wheels of transmissions of power-saturated machines is deep contact pitting of active surfaces of teeth. Dependence is investigated between the number of cycles before the deep contact destruction of material and the maximal tension of cycle with taking into account the mechanical characteristics and structural parameters in the critical zones of the diffusion layers of the teeth, in which fatigue processes of deep contact destruction of material are developed. Lines of deep contact fatigue of teeth material are constructed by the criterion of equality of hardness value and structural parameters in the zones of fatigue processes development under cyclic contact loading. It is shown, that the deep contact fatigue of gear wheels hardened to a considerable degree is determined by hardness value and structural components of local volumes of teeth subsurface layers. Slope index of the deep contact fatigue lines of gear wheel material have been determined. Correlation coefficients and equations of linear regression have been obtained for each deep contact fatigue line depending on hardness value in the subsurface dangerous zone of the diffusion layer, in which formation and development of fatigue processes occur, leading to the limit state of the highly stressed gear wheels.

Keywords

• gear wheels
• surface hardening
• deep contact pitting
• deep contact fatigue lines
• slope index
• linear regression equations