Research Of Wheel Loader Speed Reducer's Fatigue Reliability

Loaders are important equipments of construction machinery which play an essential role inthe production of buildings, roads, mines and docks. In the loader's working life,fatigue failure isthe main failure mode.Main speed reducer is key component of wheel loader's transmissionsystem. And as Main speed reducer's core component, bevel gears sustain alternating load whichincluding bending stress and contact stress. It can cause fatigue failure easily and make a loaderunusable. So the research of wheel loader main speed reducer's fatigue reliability is the key ofimproving quality and safety performance.As the research object, ZL50wheel loader main speed reducer's fatigue reliability has beenstuded by dynamics testing and finite element analyse. The main contents are as follow:1) The ZL50loader's loading history was obtained by dynamics testing, then spikes wereexcluded by gradient threshold detection and variance threshold detection. And invalid amplitudeswere removed by setting a threshold which value was5%.2) The main failure mode of speed reducer was analysed, and results showed that the mainfailure reason was bevel gears' Fatigue failure. Then bevel gears' contact state and failure modewere analysed based on finite element analyse, results showed that bevel gears' contact fatiguefailure in single teeth meshing stage and driven bevel gear's bending fatigue failure should beconsidered in speed reducer's fatigue reliability calculating.3) The load spectrum was obtained by rain-flow counting method. Then this paper analysedthree distributions'(normal distribution, lognormal distribution, Weibull distribution) fittingdegree of load spectrum and effect on the fatigue reliability. Results show that the highest fittingdegree of distribution function should be used to fit load spectrum, which can reduce the error instructural fatigue reliability prediction.4) Main speed reducer's stress distribution function and strength distribution function werecalculated. Then, speed reducer's fatigue reliability was carred out by stress-strength interference theory. At last, bevel gears' fatigue life was calculated based on Miner's linear cumulativedamage theory of fatigue.The research work Supported by Important Technology Project of Technology Office inZhejiang province (Grant No.2009C11111)...