Effects of Difference in Roller Hardness on Rolling Contact Fatigue : Vibration, Control Engineering, Engineering for Industry

抄録

Rollers made from 0.45% carbon steel with hardnesses in the range of 190 to 500 HB were used as test pieces. The rollers were rotated under rolling with sliding conditions. The sum of the initial surface hardnesses of the rollers was made greater than the theoretical oil film thickness, in most cases. Not a single pit occurred on the 190 HB rollers at a Hertzian pressure of 1.30 GPa (132.7 kgf/mm²) when the hardness differences were less than 40 HB units. However, pits occurred at the same Hertzian pressure before 1.5×10⁶ revolutions on the slower rollers (follower) with hardnesses of 220, 250 and 300 HB when these rollers were rotated with the faster rollers of higher hardness, giving hardness differences greater than 10 HB units. By measuring the duration of full EHL conditions, the friction coefficients, etc., it was clearly shown that the reason why an unexpectedly small hardness difference can cause pitting failure is attributed to the insufficient running-in which occurs when the hardness difference is greater than a certain limit.