技術レポート 制振材料とその性能測定について 11

When the loss coefficient measurement data is plotted with Young's modulus on the horizontal axis and the loss coefficient on the vertical axis, the data aligns in an inverted "U" shape. This plot position remains the same regardless of the reference temperature T ₀, and the better the measurement accuracy of the loss coefficient, the more the plot points align along the inverted U shape. Here, the inverted U curve is drawn based on the curve fitting results of Young's modulus, so if the curve fitting is not successful, the correlation with the measurement data (plot) will be poor. Therefore, the data should not be read from the inverted U plot, but rather using the equivalent frequency nomogram. The inverted U plot is useful for verifying the accuracy of the curve fitting of Young's modulus and the measurement accuracy of the loss coefficient and resonance frequency of the test specimen.

The loss coefficient - as an approximation formula for the conversion frequency, it is fitted to a curve as shown in Figure 10. The following formula will be used as the approximation.

Type 13

Here, k is,

Type 14

Loss coefficient parameters (8 items)

：Slope on the left side of the loss coefficient peak
Slope on the right side of the loss coefficient peak
The common logarithm of the maximum value of the loss coefficient.
L: Common logarithm of the conversion frequency at which the loss coefficient is maximized
c: Curvature
Q _h: Bending strength on the right side of the loss coefficient
η _h: Loss coefficient at maximum conversion frequency
: Right side of the loss coefficient bending conversion frequency

Young's modulus - Fit a curve to the characteristic of the approximate formula for conversion frequency, as shown in Figure 11 below.

The following expression will be used as an approximation formula.

Type 15

○ Young's modulus parameters (4 items)

Q: Slope of the central part of the elastic modulus
E _m: Median of the elastic modulus
f _m: Equivalent frequency of the central part of the elastic modulus
E _l: Elastic modulus at the minimum equivalent frequency

By determining the curve fitting parameters for the loss coefficients (8) and Young's modulus (4) in this way, it becomes possible to express the loss coefficients and Young's modulus in a formula that only includes frequency, excluding temperature, which is expected to facilitate adaptation to simulation software such as finite element methods.