102 マイクロピッチングの発生機構に関する考察(OS02-1 歯車の強度I)

Abstract

In earlier report, the authors carried out surface durability test with carburized steel roller and carburized steel roller with shot peened by two different methods. After examination, some micropitting were occurred on contact surface. In this study, we clarified the generation mechanism of micropitting by measuring the geometry of micropitting in detail. The object of the geometry measurement is a width of pit and the maximum depth of micropitting, and an angle that contact surface and crack formed. As a result of measurement, the maximum depth of micropitting was match shallower than the depth that predict by column to column contact of test rollers. Further, a strong correlation was confirmed the maximum depth of micropitting and the damage width along tool mark. Also, the damage width that vertical direction to tool marks was depending on tool mark width which increases along with the contact load. It is thought that micropitting was caused by asperity contact of contact surface after running-in process. Shapes in the contact asperity point were guessed by measurements of micropitting width and depth. The stress analysis was carried out for obtained asperity shape, and stress direction was calculated. Then, the stress that caused micropitting was determined by comparing stress direction and crack propagation angle. As a result, micropitting was caused by maximum shearing stress that increases along with high friction coefficient, and moves to contact surface.