木材應力波非破壞計測技術之研發及應用

Application and Development of Stress Wave Nondestructive Measuring Technique in Wood

黃彥三(Yan-San Huang) ； 陳欣欣(Shin-Shin Chen)

《中華林學季刊》 37卷3期 (2004/09) Pp. 317-323

https://doi.org/10.30064/QJCF.200409.0007

摘要

與木材材質有關之因數如含水率、比重、木理走向、彈性係數等可藉破壞或非破壞方法來測定或推定。而所謂非破壞試驗法係指藉由非破壞的方法來評估材料的性質或內部構造而言。本研究旨在研發兩種新的應力波計測技術，其一為利用應變規來測定兩標點間之應力波傳遞時間差及試材之共振頻率，藉以計算試材之音速及動彈性係數，其二為利用三向動力計來測定試材之共振頻率。試驗時採用六種實大尺寸試材，共振頻率之測定係利用FFT頻譜分析儀。結果顯示兩種方法所測得之試材共振頻率均與由打音法測得者完全相同，故可用來取代打音法。此二新方法於測試時不受周遭環境噪音之影響，故適於應用在工廠內生產線上。另於實大材上挖削榫槽，探討榫槽數對共振頻率之影響。結果顯示，共振頻率隨榫槽數之增加僅略為減少。此一結果將有助於對老舊建材彈性留存率之評估，有助於此等建材之有效再利用。

關鍵字

打音 ； 三向動力計 ； 應變規 ； 應力波 ； 非破壞試驗

並列摘要

The basic properties of wood such as moisture content, density, grain direction and modulus of elasticity can be measured nondestructively. In this project, two novel nondestructive stress wave methods were developed. Firstly, the strain gauge method was used to measure the time difference of stress wave passing through two gauges adhered on the surface of test piece and also their main frequencies Secondly, a 3-component dynamometer was used to measure the resonant frequency of timber Six kinds of full size timber were used for test. A FFT spectrum analyzer was used to measure the resonant frequency. The results showed that the resonant frequencies measured by the strain gauge method and the 3-component dynamometer were exactly the same as those measured by the tap tone method. The advantage of the two new methods is free from the affection of environmental noise experienced in the tap tone method. So that, the two new methods can be applied in the factory. In addition, mortise holes were made on the full-size timber, and resonant frequencies measured sequently. The results showed that the resonant frequency decreased slightly with increased number of mortise holes.

並列關鍵字

Tap tone ； 3-component dynamometer ； Strain gauge ； Stress wave ； Nondestructive test