非破壞試驗技術應用於原木材質評估之可行性研究

Feasibility of the Evaluation of Log Quality by Using Nondestructive Test Method

黃彥三(Yan-San Huang) ； 陳欣欣(Shin-Shin Chen) ； 漆陞忠(Shen-Chung Chi)

《林業試驗所研究報告季刊》 8卷1期 (1993/03) Pp. 85-98

https://doi.org/10.7075/BTFRI.199303.0085

摘要

木材之強度性質雖無法以非破壞方式直接測定，但可利用其與比重、彈性係數、缺點等之相關性加以推定。由於大部分非破壞試驗係用於板材、柱材等製材品上，少有應用在原木上的。因原木品質與製材品質有密切關連，若能就原木作非破壞試驗，並將結果應用於製材作業，則能提高製材品質，增加木材利用率，達到適材適用，充分利用木材資源之目標。因此，本計畫以蓮花池分所20年生杉木造林木為試材，以超音波法及打音頻譜分析法進行非破壞試驗，探討原木直徑、試材長短、割裂長度及孔洞大小等對測值之影響。本試驗之結果顯示以非破壞方式探測原木之性質具有可行性，其主要結果如下：
1.經由原木斷面橫向超音波穿透時間之測定，可探知原木內部腐朽或孔洞之有無並加以定位。
2.原木斷面直徑方向之超音波穿透時間隨內部腐朽或孔洞之存在而增加，其增加率與孔洞直徑之相對大小(d/D)成比例關係。
3.不論原木或板材均可利用打音法測出音速或彈性係數，但為避免頻譜出現雜訊，造成判讀困難，原木的長徑比或板材的長寬比宜在5以上為佳。

關鍵字

打音 ； 音速 ； 頻譜分析儀 ； 非破壞試驗 ； 動彈性係數 ； 超音波穿透時間

並列摘要

Although, the strength property of wood could not be determined directly by the nondestructive test method, but, it can be predicted satisfactorily from the relations among this reading and specific gravity, elastic modulus or defects of wood tested.
The most nondestructive test has been applied for determining the quality of lumbers, poles and other sawing wood, and rarely used for logs, When using the data obtained from the nondestructive test carried out from the logs for the sawing operation, the quality of sawed lumber, its yield and the effectiveness of using wood resources would be promoted and increased since the quality of logs has been proved highly correlated with the quality of lumber produced.
This project therefore, using a type of nondestructive test ultrasonic wave and tap tone method to investigate and to clarify the influence of log diameter, its length, the length of check and the size of rote or hole on the quality of 20 years old China fir sampled from the plantation in Lien-hua-chih.
The results revealed that the using of this method to determine the log quality was a quite feasible. The main results are:
1. The rote or hole and its location inside the logs can be detectd by the transmitting time of ultrasonic wave from log transverse direction.
2. The time of transverse transmission of ultrasonic wave increased by the increasing of interior rote or hole size. Its increasing rate and the relative size of rote or hole(d/D) tend to be closely related.
3. Either the logs or the lumbers, the sound speed and elastic modulus can be determined from the tap tone method. However, the ratios of length to diameter of log and length to width of lumbers should be kept greater than 5.

並列關鍵字

Tap tone, Sound velocity ； Spectrum analyzer ； Nondestructive test ； Dynamic modulus of elasticity ； Ultrasonic wave transmitting time