Estimating the lifetime of gear lubricants

The main goal of this paper is to present methods on how to take oil degradation into account in reliability modeling. Therefore mineral oil based gear lubricant was artificially aged in an oven and reliability data was gathered from exemplary selected tests. For testing the aged oil, three tests were selected: two simple test benches (Brugger test apparatus and a four-ball roller test) and a gear test bench. To include oil aging into the transmission´s system reliability, two possibilities were considered: -as a machine component and -the lubricant and its deterioration as an influence on component life. The gathered reliability data from the test results were used to derive statistical life models according to the proposed possibilities. The presented work leads to a more realistic reliability model of transmissions which considers the influence of oil degradation besides mechanical and electronic failure modes.