ROTATIONAL DEGREES OF FREEDOM FOR STRUCTURAL COUPLING ANALYSIS VIA FINITE-DIFFERENCE TECHNIQUE WITH RESIDUAL COMPENSATION

Abstract This paper views the experimental derivation of rotational degree of freedom (rdof) parameters (i.e. either modal or response) from a new viewpoint. Although using a well-known technique—the finite-difference formulation—what is important here is not the technique itself but to establish the best rotational data to be used as input in structural coupling analysis. For this, the residual compensation in the rdofs derivation has to be considered carefully, together with the best order of the approximation to use. The finite-difference technique can be used considering either FRFs or modes. Although each has its own advantages and drawbacks, what is normally considered a problem when using this technique is how to establish the spacing between the accelerometers and the order of the approximation to use. Little attention is paid to the residual problem which comes as a consequence of eliminating the noise incorporated into the experimental data. So, in this paper, the use of the finite-difference technique to obtain rotational dofs for structural coupling analysis is revisited, however, with the intention of establishing the best rotational input data to be used for that application, with emphasis to the residual compensation. Examples are shown to validate the conclusions.