NORMAL-MODE FORCE APPROPRIATION––THEORY AND APPLICATION

Normal-mode force appropriation is a method of physically exciting and measuring the undamped natural frequencies and normal-mode shapes of a structure which is distinct from the more common phase separation approaches. In this paper, the theory of normal modes and force appropriation is reviewed and a comparison made of a number of common force appropriation techniques. Both simulated and experimental data are used to highlight the relative merits of the different approaches, and comparisons to phase separation results are presented. Further advancements and applications of normalmode testing––to non-proportionally damped structures, non-linear structures and consideration of the optimal exciter placement problem––are also discussed.