110 S. Tilmann Fig. 12.8 FilterDiff comparison of rectangular coupons second bending mode Table 12.2 Filter comparisons Point Strain gage Measured strain peak-peak (με) 7mmO, 7mm geo magnitude (με) 7mmO, 15mm geo magnitude (με) 10mmO, 7mm geo magnitude (με) 10mmO, 15mmgeo magnitude (με) 15mmO, 7mm geo magnitude (με) 15mmO, 15mmgeo magnitude (με) 86 1 235.2 295.8 278.6 285.9 270.9 272.0 260.4 267 2 229.5 263.1 255.8 253.7 243.8 245.8 234.6 445 3 225.3 231.1 231.4 229.4 227.7 228.6 225.6 622 4 229.5 235.7 231.2 234.7 229.2 235.6 231.1 796 5 234.0 275.1 262.6 268.4 258.3 259.1 252.2 removed while the bottom number represents the geometry filter used to process the data. The filter appeared to have a much greater effect on the outer points while the inner points values only varied by a couple percent depending on the filter. The final filter settings chosen were based on deviation from measured strain and qualitative assessment of the FilterDiff and GeoDiff outputs from the strain processing software. The settings that obtained the best measurements were a vibration filter of 15 mm with a geometry filter of 15 mm. 12.4.3 Displacement A triangular grid pattern was used to collect data for the strain calculations. The velocity data was banded from 239 to 240.5 Hz around the second bending mode frequency of 239.9 and the strain processing software was applied using the filters specified in the previous section. The displacement results for the coupon can be seen in Fig. 12.9. These displacement results were used by the strain calculator to determine strain at each point.
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