In many technical fields there are applications, which are based on or utilise mechanical wave propagation and resulting vibrations. For example, there are sensors, which use ultrasonic waves as a measurement principle, but the resulting vibrations, which often occur, are unwanted, as in car acoustics. In this area, often called NVH (Noise Vibration Harshness), there are many well-proven theories and simulation techniques. Depending on the particular method, these are valid for a maximal frequency of 500 Hz to 5 kHz. In a new application in the field of passive car safety, there is a much higher frequency range of interest. The structure-born sound based crash detection uses the structural vibration of the car. Typically, the dynamic behaviour of a structure and the wave propagation is investigated with simple beam and plate theories and corresponding finite element analysis. But for the high frequency range up to 20 kHz there are many uncertainties in these theories and simulation models. This article briefly outlines the well known errors of finite elemental analysis and the difference in the performance of Euler-Bemoulli and Bresse-Timoshenko beams, respectively. The main focus lies in a problem, which only arises when the high frequency dynamical behaviour of thin walled beams is in question. Here, the eigenfrequencies of the thin wall dominate the dynamic response of the beam. Based on this, the tremendous difference between simple beam simulations and the reality can be seen. This leads to challenges in the simulation of high frequency structure-born sound propagation in car structures and similar problems.
Inadequacies of beam theories and elements for the description of high frequency bending wave propagation in car structures
2008
11 Seiten, 8 Bilder, 22 Quellen
Aufsatz (Konferenz)
Englisch
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