1987-04-28

Analytical Method of Tracked Vehicles Hull Interior Noise Evaluation 870998

A major cause of tracked military vehicles interior noise and vibration is the interaction between the track shoes and the suspension system i.e., idler wheels, sprocket wheels and roadwheels. This interaction causes impact forces and dynamic track tension fluctuations that are transmitted to the hull structure which in turn vibrates and radiates noise.An analytical method has been developed to predict the interior noise of tracked military vehicles. Complete validation of the method is currently in progress. The method is useful in determining the change in interior noise due to variation in track and suspension characteristics, hull stiffness, damping, etc. Evaluating these variations experimentally is very costly and difficult; however, with this analytical method, noise and vibration performance of vehicle hull structures can be predicted analytically in the vehicle design stage.A finite element computer model of the hull is used to predict the force-to-noise transfer functions of the tracked vehicle. These force-to-noise transfer functions are then used to predict the absolute interior noise of the vehicle, once the dynamic force inputs to the hull at the idler, sprocket, and roadwheel locations are calculated. The finite element method has been applied in the automotive industry to model the entire structural-acoustic vehicle system (1)*.For tracked military vehicles, the coupled model of the track-suspension and hull is not necessary as the track-suspension interaction due to the chordal impact and track tension fluctuations has negligible feedback from the vehicle hull vibrations.The computer program ANSYS (2) is used for the finite element model of the hull and for the eigen-solution of the model. The computer program NOISE (3) and other preprocessors are then used to calculate the noise-to-force transfer functions. The NOISE program uses modal response of each major structural element to calculate the one-third octave band interior noise-to-force transfer functions.A computer program such as TRAXION (4) models the track and suspension and can predict the dynamic force input to the hull at a given vehicle speed. The force input is then combined with the noise transfer functions to obtain the absolute interior noise.

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