2019 Volume 54 Issue 2 Pages 123-134
Rolling bearing produces an eruption of vibration owing to its own rotation. When such rolling bearings were set in a mechanical system, external vibration arising from another rotating shaft and load variation works on the rolling bearings. In past days and under such running circumstances, lifetime calculation for rolling bearing had been made by multiplying a load factor, which was influenced by the working situation of the mechanical system, to dynamic equivalent load of the bearing. However, the load factor is grouped under three values and quantitative condition to select one value out of three values is not described. A designer for the mechanical system intends to over-estimate the load factor for safety. This tendency will cause an excess specification, cost increase and growing in machine size. In the previous paper, with considering a mechanical vibration of automobile and factory automation (FA) equipment, several endurance tests were performed by applying radial vibrations having a frequency of 24.75Hz and vibration acceleration up to 10m/s2. As a result, abnormal increase of vibration were not observed for up to three times of basic dynamic life. In this paper, endurance tests for more stringent condition (up to 49.5Hz and 15m/s2) than the previous ones were performed and the influence of external vibration to increase of vibration of the bearing itself was studied. As a consequence, it was clarified that the wear at the load area of outer ring became larger when the applied external vibration increased, and the external vibration had an influence on the damage of the bearing. Although flaking is not observed, it is not required to set a mechanical coefficient such as the load factor larger than 1, under the condition of this research.
