Response DOF selection for mapping experimental normal modes-2016 update

Abstract

A modified Guyan reduction strategy for response degree-of-freedom (DOF) selection to map experimental normal modes is described and demonstrated. The method employs static load patches, rather than point loads, in regions defined by 3-D elastic elements and other problematic zones on a highly detailed finite element model (FEM). Three key benefits are realized by the methodology, namely (1) definition of a well-posed test-analysis mass (TAM) matrix, (2) application of a previously published residual kinetic energy matrix for definition of appropriate measurement DOFs, and (3) elimination of irrelevant modes from the measured mode set. Improved qualities of the modified Guyan reduction strategy are demonstrated with a problematic spacecraft-type FEM, which cannot be readily treated using classical Guyan reduction methodology.