전달율 측정에 의한 점탄성재료의 복소탄성계수 추출시의 민감도 분석

Abstract

The complex Youngs modulus of a viscoelastic material can be obtained as a function of frequency from the measurements of relative motion between the two ends of a bar-type specimen. Non-resonance method is usually used to obtain the complex Youngs modulus over wide range of frequency including resonance points, while in resonance method information at resonance frequencies only is used. However, the complex Youngs modulus obtained by the non-resonance method is often unreliable in the anti-resonance frequency regions because of the measurement noise problems. In this study, the effects of the random measurement errors on estimating the complex Youngs modulus are studied in the aspect of sensitivity, and how to obtain the reliable frequency region for a given measurement error level is shown. The usable frequency regions in determining the complex Youngs modulus are represented by a non-dimensional parameter formed with the wave length and specimen length.