At the end of its development cycle, a new truck variant is exposed to vibration tests, both in laboratory conditions by means of a 4-shaker test rig and in real road tests on a proving ground. The idea is to extend the use of these test data by applying Operational Modal Analysis and by being able to correlate the analysis results with Finite Element predictions. Basically, the only feasible way to perform a modal analysis experiment on a complete truck is by using test rig or real road excitation. In both cases the forces introduced in the structure are not available or difficult to measure and, hence, Operational Modal Analysis needs to be applied. This paper will investigate the feasibility of applying Operational Modal Analysis to test rig data. Direct FEM calculations, time-domain simulations and real measurements will be compared.
A second application discussed in this paper is the design of a silent truck oil pan. Hereto, an evaluation of the
dynamic properties in operational conditions is of great interest. Especially the damping ratios are important
factors in the noise emission. This paper discusses the use of Operational Modal Analysis for experimentally
determining the eigenfrequencies, damping ratios and mode shapes of a vibrating structure. The paper discusses both the theory and practical aspects of applying Operational Modal Analysis to engine run-up data.
