52 E. Altuntop et al. Fig. 6.6 First five mode shapes of the continuous plate from FEA (a) f1 D4.41Hz, (b) f2 D19.15Hz, (c) f3 D27.64Hz, (d) f4 D60.48Hz, (e) f5 D75.43Hz Table 6.2 Comparison of natural frequencies coming from experiment and finite element model Natural frequencies of the continuous plate [Hz] Mode number Experimental FEM Absolute error [%] 1 4:41 4:42 0:14 2 18:42 19:15 3:96 3 27:28 27:64 1:30 4 58:87 60:48 2:73 5 75:57 75:43 0:19 6.6 Discussion and Conclusions In this study, the FEM of a continuous plate is constructed and modal tests are performed to obtain a valid model. After the material properties of the plate and mass values of accelerometers are optimized, another plate having six rivets is manufactured. Experiments are also repeated on the riveted plate to get resonance frequencies. Rivets are modeled as bushing elements in ANSYS® having six stiffness values correspond to six degrees of freedom and these values are determined using the Optimization Toolbox in MATLAB. Having obtained a good agreement between the resonance frequencies coming from the modal test and FEA is established, stiffness values are then recorded.
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