Mode Based Prediction of Vibrations in Complex Automotive Structures, A Review of Shortcomings

Noise, vibration and harshness (NVH) comfort in automotive and other transportation vehicles is becoming increasingly important for customers and passengers and thus also for manufacturers. Accurate numerical prediction methods are thus of great practical interest, especially for designs where high damping materials or multilayer treatments are included. Traditionally, mode based techniques are used for prediction of vibrations in automotive structures. This is motivated by the possibility of using reduced modal models instead of very detailed FE models. Unfortunately, for highly damped structures, the effect of reduced model size on the accuracy of predicted NVH response levels is often not known.

In this paper, conventional modal vibration theory, along with two simple damped Oberst beam examples, are used to highlight problems with the application of modal methods towards highly damped materials, systems and multilayer treatments.