Abstract
The effective case depth (ECD) plays an important role in the meshing strength of internal gear transmissions. Carburizing quenching heat treatment is commonly used to enhance gear strength and wear resistance. However, the different ECDs in internal and external gears caused by heat treatment significantly affect the meshing strength, causing vibration, reducing gear service life, and hastening malfunction in internal gear transmission. In this study, we conducted an investigation of different ECDs by the heat treatment of carburized gear pairs by numerical simulation with the finite element method (FEM) and experiment tests. We analyzed three different carburized layer models, with the ECD in the internal gear being greater than, less than, and equal to the ECD in the external gear. In addition, we investigated the ability to distinguish between hardness gradients in gear teeth by dividing the carburized depth into seven layers to improve modeling accuracy. Results revealed that the meshing strength of internal gear transmission could be significantly enhanced by adopting the model with the ECD in the internal gear being less than the ECD in the external gear, and moreover, the shear stress of carburized gears initially increased and then decreased along with depth direction, and the maximum value appeared in the middle of the lower surface.
Highlights
With the overall development of science and technology, gear transmission has been progressively developed toward light weight, high load capacity, and low energy consumption
The external gear was fixed on a pedestal and the internal gear connected to a steel frame
The stress and displacement distribution of the carburized gear pair in any position can be achieved through transient analysis of the finite element method (FEM) models of the carburized gear pair using (1) to (19)
Summary
With the overall development of science and technology, gear transmission has been progressively developed toward light weight, high load capacity, and low energy consumption. Carburizing and quenching heat treatment have been widely adopted to enhance gear strength and wear resistance. The use of a carburizing process in gear transmission systems is an important means of achieving a lightweight gear design because the carburized gear teeth usually acquire sufficient toughness, hardness, and wear resistance [1, 2]. It is well known that the increase of carburizing depth can improve the strength of gears and prevent failure. The increases in production and energy consumption may result from carburizing depths that are too large, which may lead to highdifficulty processes and the growth of the process cycle. ECD is closely related to the meshing strength and reliability of gears; the design of an optimum ECD can improve the strength of gears and avoid high cost and wasted energy
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