The assessment of damping capacity of the disk-shaped damper for the conical gear of gearbox of gas-turbine engines

Аuthors

Yakovkin V. N.^*, Besschetnov V. A.

Kompani “Aviadvigatel”, 93,Komsomolsky Prospect, Perm, 614990, Russia

*e-mail: jakovkin88@mail.ru

Abstract

The breakdowns of a conical gear of gearbox sometimes occur in service of gas-turbine engines, resulting in shutting down the aircraft engine during the flight. The results of the study of one of these cases showed that the destruction has the fatigue nature. Usually the maximum vibratory stresses, located in gear, take place in modal oscillations with three or four nodal diameters. Detuning from resonance by changing the geometry variables is not always possible for this type of cog-wheels. The solution for this problem was suggested as the increase of the damping capacity of an element by adding a disk-shaped dry friction damper.
The contact interaction on surfaces with friction creates a nonlinearity of the problem, which is caused by the presence of coulomb friction. Modern design packages allow to take into account nonlinear contact interaction of full-scale models. However, contact problems, which deal with constrained or damped oscillations, still require a lot of computing resources. So, the main emphasis in the work was put at methods, allowing to evaluate the damping capacity of the structure more accurately.
The method of rapid assessment is based on a linear approximation of the sustained forced oscillations. The algorithm is implemented by calculating the eigen mode (modal analysis). The simulation of friction force is reproduced by the use of tangential springs. The level of damping of construction was calculated by the expended friction work.
The method of rapid assessment revealed the following: the optimum application force for the damper depending on the level of stress and the coefficient of friction; the stiffening effect of the damper on the damping capacity. The analysis of comparison study of the rapid computational assessment results with the experimental results showed the capability of achieving the satisfactory fit selecting the coefficient of dry friction and specifying the decrement of the gear oscillations without the damper.
The modified damper, damping capacity of which is considerably higher than in typical designs dampers, is also suggested in work. The effectiveness of the modified damper is demonstrated by the method of forced oscillations in transient analysis by taking to the account nonlinear contact interaction.

Keywords:

coulomb-friction damper, conical gear, disk-shaped damper

References

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