The Contact Mechanics of Novikov’s Surface-Hardened Gearing during Running-in Process

Alexey Beskopylny,Nikolay Onishkov,Viktor Korotkin

doi:10.1155/2018/9607092

Alexey Beskopylny, Nikolay Onishkov + Show 1 more

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https://doi.org/10.1155/2018/9607092

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Abstract

The article is devoted to the analysis of the state of the contact surfaces of the higher kinematic pair in the general case of relative motion, that is, in the presence of rolling, sliding, and twisting, which is characteristic of Novikov’s circular-screw gears. The purpose of the work is to assess the impact of friction forces, the state of contact surfaces after tool processing, and the localization of the instantaneous contact spot on the level of contact—fatigue durability of gears. Power contact in the presence of geometric slippage of the mating surfaces leads to a significant change in the initial geometry and the mechanical properties of surface layers. In the existing methods of calculations of contact strength, the effect of running-in is investigated insufficiently, which leads to an incorrect result, especially for gear with high hardness of the teeth. In this work, the conditions of contact interaction close to the real requirements are studied on the basis of experimental material, numerical solution of the contact problem, determination of the terms of the contact areas of slip, and adhesion within the instantaneous spot. The shape of the instant contact spot has asymmetry and can be approximated by an ellipse with the introduction of a correction factor. The running-in period is of a plastic nature with cold deformation and reduction of the roughness of surfaces. As a result of the run-in period, the area of actual contact (tooth height) is increased by 2 or more times. It is not desirable to spread the area of contact at the area of adhesion that initiates the formation of pitting. The presence of defective surface area on the level of contact strength does not have significant influence, because of the running-in period, but increases the risk of spalling and brittle fracture.

Highlights

Running-in is the process of transition of the properties of the contacting surfaces of the parts from the initial to the operational
For Novikov’s transmissions, this process is of particular importance, because due to its initial point contact passes into contact on the surface, which is due to a sharp increase in the contact strength of such transmissions
The burnishing process is influenced by many factors—geometric, kinematic, power, lubricant properties, and contact surfaces

Summary

Introduction

Running-in is the process of transition of the properties of the contacting surfaces of the parts from the initial to the operational. There is a change in size and macro - and microgeometry, as well as physical and mechanical properties of the material of the interacting surfaces to optimize their parameters in a relatively short period. For Novikov’s transmissions, this process is of particular importance, because due to its initial point contact passes into contact on the surface, which is due to a sharp increase in the contact strength of such transmissions. The burnishing process is influenced by many factors—geometric, kinematic, power, lubricant properties, and contact surfaces. It is clear that instantaneous contact spots, both calculated and determined experimentally, differ significantly (Figure 1)

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