3-D Scanning Vibrometry Enables Efficient Experimental Modal Analysis of Large and Complex Structures for NVH-Optimised Vehicles

In the design and development of modern cars with respect to comfort, silence and safety, state of the art experimental modal analysis is one of the essential development tools. Due to the large amount of degrees of freedom of such a large and complex system like a car with all its components, a complete simulation by FEM can not be realised easily and requires an enormous expenditure of work and calculations. In addition the simulations are based on assumed system parameters and thus the vibration behaviour of the resulting prototypes often is not completely identical to the simulated model. In contrast to conventional measurements with accelerometers, the 3-D Scanning Vibrometer enables fast and efficient non-contact measurements of the in-plane and out-of-plane vibration behaviour at all optical accessible surfaces. The method easily allows to increase the number of measured points to obtain a high measurement point density. In addition the correlation with FEM results is facilitated, as the measurements do not add mass or stiffness to the measured structure. Furthermore the measurement can be performed exactly at the nodes of the FE model. MIMO analysis is as well possible as measurements on rotating surfaces or measurements via mirrors. The powerful capability of 3-D Scanning Vibrometer measurements is presented by the example of two industrial applications. The first example describes the measurement of a complete car body at Daimler Chrysler, the second example shows the measurement of brake systems integrated in the design optimisation process at Continental Teves, to avoid brake noises.