Investigation of Contact Fatigue of High Strength Steel Gears Subjected to Surface Treatment

• Published in: Journal of materials engineering and performance Vol. 18; no. 7; pp. 939 - 946
• Main Authors: Dimitrov, L., Michalopoulos, D., Apostolopoulos, Ch. Alk, Neshkov, T.D.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01-10-2009; Springer Nature B.V
• Subjects: Characterization and Evaluation of Materials; Contact; Corrosion and Coatings; Crack initiation; Engineering Design; Fatigue (materials); Fatigue failure; Gear teeth; Materials Science; Mathematical analysis; Mathematical models; Quality Control; Reliability; Safety and Risk; Shot peening; Tribology; residual stress; shot peening; surface treatment; contact fatigue; thermal treatment
• ISSN: 1059-9495; 1544-1024
• DOI: 10.1007/s11665-008-9321-6

In this paper the contact fatigue resistance of gearwheel teeth, subjected to shot-peening treatment, was investigated experimentally and analytically. The main objective was the evaluation and prediction of fatigue crack initiation, propagation, direction, and rate. A specially designed experimental rig was used to test a number of spur gears with the following characteristics: (a) unhardened, thermally untreated unpeened surfaces, (b) thermally treated unpeened surfaces, (c) unhardened peened surfaces, and (d) thermally treated peened surfaces. The theoretical model assumed initiation and propagation of surface cracks of gears operating in the elastohydrodynamic lubrication regime while loading was due to simultaneous rolling and sliding. Finite element modeling was used for the calculation of the stress field at the gear teeth. Comparison of the experimental and analytical results showed considerable improvement in the contact fatigue strength of thermally treated gear teeth and especially those that underwent shot peening, which increased surface durability. The residual stresses induced by shot peening are mainly effective in stopping microcrack propagation. When shot peening is applied on thermally untreated gear teeth surface, it increases the contact fatigue life of the material by 17% at 7 × 10
5
loading cycles. If shot peening is applied on carburized gear teeth surfaces, it increases the surface fatigue life by approximately 8% at 10
6
cycles. Contact fatigue and eventual pitting are treated as a normal consequence of the operation of machine elements. To study this failure process different types of testing machines have been designed. The purpose of this paper is the presentation and evaluation of a new design experimental rig for studying contact fatigue damage of gear teeth subjected to different load patterns.