Effects of Ultrasonic Detection Modes on the Longitudinal Ultrasonic Wave Transmission in Domestic Plantation Lumber

超音波檢測方法對國產造林木材縱向音速傳遞之影響

葉民權(Min-Chyuan Yeh) ； 劉錦坤(Chin-Kun Liu) ； 林玉麗(Yu-Li Lin)

《台灣林業科學》 22卷1期 (2007/03) Pp. 57-68

https://doi.org/10.7075/TJFS.200703.0057

摘要

本研究以柳杉及杉木材，評估超音波檢測方法對木材縱向音速傳遞之影響，結果顯示木材以40~1000 kHz範圍之換能器所測得之縱向音速，在直接法中沒有顯著之差異，平均分別為5074及6003ms^(-1)。表面法及半直接法則在500及1000kHz條件下，木材縱向音速會呈明顯下降。在不同檢測模式中，以40kHz換能器所測得之縱向音速均有良好之迴歸正相關，R^2介於0.92~0.94之間。利用不同形狀換能器及不同耦合模式所測得之縱向音速，亦有良好之迴歸正相關，R^2介於0.95~0.99，其中平式換能器較錐形換能器測得之縱向音速高8.8~11.1%。利用不同檢測方法所測得之超音波縱向音速與木材之彈性模數間皆有極高之正相關，R^2介於0.79~0.85，期望可提供未來超音波檢測與推估木材容許應力之應用。

關鍵字

超音波檢測技術 ； 縱向音速 ； 柳杉 ； 杉木 ； 彈性模數

並列摘要

The performances of different ultrasonic detection applications on the longitudinal wave propagation in Japanese cedar (Cryptomeria japonica) and China fir (Cunninghamia lanceolata var. lanceolata) lumber were evaluated in the study. Results showed that insignificant differences among longitudinal ultrasonic wave velocities measured by transducers from 40 to 1000 kHz were found using the direct transmission method. The average wave velocities were 5074 and 6003 m s^(-1) for Japanese cedar and China fir, respectively. The longitudinal ultrasonic wave velocity obviously decreased with both the surface transmission method and semi-direct transmission method under 500-and 1000-kHz conditions. Good correlations, i.e., R^2 values of between 0.92 and 0.94, among the measured longitudinal ultrasonic wave velocities in the 3 detection methods with a 40-kHz transducer were obtained. Longitudinal ultrasonic wave velocities of wood measured with the different-shaped transducers and coupling methods also had good correlations, with R^2 values of between 0.95 and 0.99. The velocity measured with the flat transducer was 8.8~11.1% higher than that with the tapered transducer. The modulus of elasticity of wood can be estimated using longitudinal ultrasonic wave velocities measured by the 3 different detection methods with R^2 values of between 0.79 and 0.85 for Japanese cedar and China fir. It is expected that ultrasonic detection can be applied to the derivation of allowable strengths of structural lumber from Taiwanese plantations and for field inspections.

並列關鍵字

ultrasonic detection technique ； longitudinal ultrasonic wave velocity ； Japanese cedar ； China fir ； modulus of elasticity