主催: The Japan Society of Mechanical Engineers
会議名: 動力・運動伝達系国際会議MPT2017
開催日: 2017/02/28 - 2017/03/03
Today, proofs of system reliability for plant components such as gear units or complete mechanical systems are in increasing demand in various sectors of the power transmission industry. However, there has been no common language to interpret the reliability for each component, for example, gear engineers prefer the term ‘safety factor' while bearing engineers use the service life. A component's safety factor or its calculated service life is actually nothing else than a statement of its reliability. But only if the reliability of the individual parts is known, then the reliability of the mechanical system as a whole can be determined.
Stating a system's reliability is also more comprehensible than listing safety factors for those people without detailed knowledge in mechanical engineering. A statement such as "the probability that gear unit X will fail during its guaranteed service life of 50,000 hours is less than 0.02%." is much easier to understand than "the safety factors of all the gears in gear unit X, calculated for an operating time of 50,000 hours, are all bigger than 1.6.", although both statements mean the same thing.
This paper describes how the probability of failure of the basic gearbox components (shafts, bearings, gears) can be derived from the component's service life as specified in the standards, according to the Weibull failure criterion. In order to determine system reliability, the gear unit elements are classified according to their significance: if an element fails, does it directly cause the failure of the entire gear unit? Or are redundancies present? The total reliability of the entire system can then be determined by mathematically combining the reliability of the individual components. This method can be applied to all ISO-, DIN- or AGMA-standard calculations that use S-N curves (Woehler lines), either with nominal loads or with load spectra.
