Research On Characteristics Of The APU Rubber Vibration Isolator

Auxiliary Power Unit (APU) is the main equipment to ensure the aeroengine can restart aftershutting down in the air, so it has a direct influence on flight safety. Besides, APU also providespower and air to the air conditioning system comforting the cabin when plane is on the ground.Because of what mentioned above and the APU isolators’ performances will affect the comfortness ofthe passengers and their selection of plane types，the APU isolator becomes one of the most importantcomponents of the plane.The main research work and results of this paper were listed as follows:1. The linear viscoelastic models were described, including Maxwell model, Kelvin-Voigt modeland three elements solid model. Stress-strain analysis, relaxation and creep analysis, as well asresponse analysis under sinusoidal excitating were analyzed on these models. A new rubber model,which was friction model and fractional derivative model, was proposed to replace the previousrubber model for the limitations of them.2. Parameters of the friction model were obtained by the amplitude correlation experiments andstudying solving method of the friction model. The experiment results show that the friction modelcould express the rubber’s amplitude correlation very well.3. The methods of simplification and numerical analysis for the fractional derivative model wereobtained form the integer derivative model. The fractional derivative model was applied to theviscoelastic model, and the methods, which were introduced in detail, could eliminate effect offriction and mass for experimental data processing. The parameters of the fractional derivative wereobtained by frequency correlation experiments of viscoelastic stress and data processing. The fractionderivative model could express the frequency correlation of the rubber very well according to thecomparison between fitting results and the experimental data.4. Experiments were carried out to verify the model with known parameters of newmodels.Results of the experiments consist with that of the calculations very well.This paper was a fundamental study of the vibration characteristics of APU isolator, which couldsupply theoretical support for the design, manufacture and application of APU isolator.