Fig. 8: Typical plot of measured natural frequencies to the specimen lengths (Triawan et al. 2010)
4.3.
Results Comparison of Static and Dynamic Tests
All measurement results are summarized in Table 3. As seen in the table, the measured Ef ’s demonstrate small value of standard deviation of less than 13% for
every test and every foam material. For the static bending test, this means that the improvements introduced in the test effectively reduced the error generated by the local-deformation effect; meanwhile, for the dynamic test, this means that the elastic moduli are confirmed to be independent of the measured flexural vibration
modes. Furthermore, Ef ’s measured by the static tests are also found to exhibit good correlation with those measured by the dynamic test, as denoted by small standard deviation of less than 5.4%. This indicates that we successfully improved the measurement accuracy of the conventional three- and four-point bending tests in measuring the elastic bending modulus.
Fig. 9: Measured Ef of Foam B plotted to the specimen lengths (Triawan et al. 2010)
vol.19 no.3
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