Cancellation of mass-loading effects of transducers and evaluation of unmeasured frequency response functions

The problem of the cancellation of mass-loading effects of transducers in experimental structural dynamic analysis is addressed. A generalized solution based upon dynamic coupling and uncoupling of substructures is presented. It is shown that it is possible to solve the problem, no matter where the extra loading masses are located, by means of a series of relatively straightforward calculations. It is also shown that one can obtain frequency response functions (FRFs) without having to undertake the corresponding measurements. Up to now, the problem of obtaining the dynamic properties of all the structure FRF curves has only been considered possible provided the complete FRF matrix has been measured. The purpose of this paper is to contribute to solving this problem. In fact, the technique developed for cancellation of mass-loading effects is shown to also allow for the evaluation of the complete FRF matrix. A simple numerical example is presented to illustrate the good theoretical performance of the method. The same example is extended to incorporate noise, simulating an experimental situation, and it is shown that the technique is highly sensitive to measurement inaccuracies and that further work is necessary in order to solve this difficulty. A possible solution to improve the results is presented and discussed. (C) 2000 Academic Press.