Helicopter designers are constantly seeking ways to improve the gear performance and reliability whilst reducing the manufacturing and maintenance costs. Contact fatigue is one to the most significant causes of damage to gears. Among its influential parameters, attention should be drawn in particular to material data (such as composition, thermochemical treatment, surface finishing), working conditions (lubrication, load, rolling and sliding speeds) or gear geometry. Modelling tools of ever increasing power and simplified contact fatigue tests are making a fullfledged contribution to study this phenomena. The FZG gear test reproduces the working conditions found on helicopters most effectively. However, it is laborious and expensive. Hence our desire is to develop more practical tools. Herein we shall consider disk tests reproducing rolling or rolling-sliding conditions observed on gear flanks. Moreover, we shall present an extremely practical ball on plane method. A finite element analysis is used in order to simulate the behaviour of parts undergoing testing. Coupled with multiaxial fatigue criteria, these models provide a method of estimating fatigue life which takes into account pertinent experimental parameters. Theoretical predictions and experimental results show a strong correlation in terms of both lifetime and damage location. It establishes that the pertinent parameters for contact fatigue haue been taken into account. This method, a finite element analysis, can entail a considerable reduction in both time and cost when choosing the optimum parameters for manufacture, such as gear characteristics (specific dimensions, corrections), nature and operating parameters for thermochemical treatments or surface finishing according to the working conditions considered (loading, lubrication,...).
Lifetime prediction of helicopter gears: experimental investigations and computer modelling
2000
6 Seiten, 10 Bilder, 9 Quellen
Aufsatz (Konferenz)
Englisch
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