Analysis of the effectiveness of the damping of resonance gear oscillations based on the dynamic contact problem by FEM

Аuthors

Vysotskii A. V.^*, Alekseev D. N.^*

Gas turbine engineering research and production center Salyut, 16, Budennogo av., Moscow, 105118, Russia

*e-mail: kbpr@salut.ru

Abstract

In modern conditions of engine manufacturing the high demands for quality, reliability and durability are produced to the accessory gearboxes that provide the basic systems of the engine and the aircraft. The design of the accessory gearboxes should ensure its efficiency over the entire range of engine operation, from startup to maximum mode during the entire flight, including the possible evolution of the airplane. In this regard, the design of gears in addition to providing strength characteristics of the gears is also necessary to eliminate the possibility of resonant oscillations in the operating range.

If for some reason to get rid of the resonant modes is not possible, some special damping devices are used, limiting the resonance amplitude and stress level in the gear due to the work of the friction forces and the dissipation of energy fluctuations.

Experience in the use of dampers in mechanical engineering is quite limited due to the complexity of the analytical evaluation of their effectiveness by traditional methods and difficulties in manufacturing.

After the widespread introduction of numerical methods in the design of the gears in the 90 years of the 20th century the process of detuning was conducted much more accurate and efficient, and the direction of solution of resonance damping problems was weakly developed and now emerging techniques are in the making.

Therefore, in response to emerging operational requirements in FSUE «SMC of GTE «Salut» on the basis of the finite element method (FEM) the method of estimation of efficiency of the damper in the conditions of occurrence of resonant gear oscillation was developed and tested.

The main idea of the work is the realization of the possibility of the direct simulation of resonance oscillations of «gear-damper» system taking into account the friction on the surface of the contact interaction. The paper discusses the resonance vibrations of bevel gear with circular teeth for mode with two nodal diameters.

To achieve this goal, it was decided several intermediate objectives:

1. Creation a physically correct model of dynamic loading gear with solution of the contact problem in the gearing (the definition of the contact patch change);

2. Creation a contact model of the «gear-damper» system, which is optimized in terms of accuracy and dimension to perform labor-intensive dynamic calculations;

3. Determination of the new value of the resonant frequency of the «gear-damper» system on the mode shape under consideration by solving a dynamic problem with a special impact force causing the damped oscillations of the system in the interesting mode shape;

4. Carrying out dynamic analysis of the «gear- damper» system with excitement in its resonant oscillations, as well as the selection of the axial mounting gap on a damper that provides the necessary down force, in which there is no increase in the amplitude of resonant vibrations.

As a result of this work the new method was formed that allows to simulate the resonant vibrations of gears, to design and optimize various damping devices, preserving the amplitude of oscillation of the system to a safe level. Currently, the results of the implementation of the method was pilot-tested.

Keywords:

damper, resonance, vibration frequency, contact, dynamic analysis, gear

References

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