28 B. Moldenhauer et al. Fig. 3.5 Finite element subsystem mesh Fig. 3.6 Bonded contact areas defined in the FEM properties, including elastic modulus and Poisson’s ratio, were tuned via a guess and check method until good agreement was found between test and FEM frequencies. Final values of 10,150 kpsi for elastic modulus and 0.33 for Poisson’s ratio were found. An average density of 0.1 lb/inˆ3 was set from mass values measured from the physical components. Also, a point mass of 0.03 lb was added to the beam tip to account for accelerometer weight. The contact between the aluminum plates was also optimized. This involved varying the size of the bonded contact area around each bolt hole. The final contact areas, shown above in Fig. 3.6, extend approximately 1/2 to either side of the bolt hole. Setting the open area between bonded zones to various states of contact was found to only degrade results, thus these zones were left free of a defined contact property.
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