Normal-mode force appropriation-theory and application

Normal-mode force appropriation is a method of physically exciting and meas uring the undamped natural frequencies and normal-mode shapes of a structur e which is distinct from the more common phase separation approaches. In th is paper, the theory of normal modes and force appropriation is reviewed an d a comparison made of a number of common force appropriation techniques. B oth simulated and experimental data are used to highlight the relative meri ts of the different approaches, and comparisons to phase separation results are presented. Further advancements and applications of normal-mode testin g-to non-proportionally damped structures, non-linear structures and consid eration of the optimal exciter placement problem-are also discussed. (C) 19 99 Academic Press.