應力波法與橫向打擊共振法於杉木立木材質評估之應用

Evaluation of Standing Tree Quality of China Fir by Stress Wave Technique and Lateral Impact Vibration Method

羅立偉(Li-Wei Luo) ； 趙偉成(Wei-Cheng Chao) ； 鄭雅文(Ya-Wen Cheng) ； 林振榮(Cheng-Jung Lin) ； 楊德新(Te-Hsin Yang)

《林產工業》 36卷1期 (2017/03) Pp. 13-23

https://doi.org/10.6561/FPI.2017.36(1).2

摘要

本研究主要係結合應力波法與斷面影像技術、橫向打擊共振法，並透過生長錐樹芯取樣分析40 株生長於中興大學實驗林管理處惠蓀林場52 年生之杉木立木材質，並建立其與杉木立木材質之相關性，以作為未來應用非破壞技術評估立木材質之基礎。研究結果指出，透過應力波斷面影像技術計算杉木立木之橫向應力波速時，40 株杉木立木之最高應力波速為1544~2835 m/s，平均值為2222 m/s，變異係數為12%；而在最低應力波速方面則為532~1699m/s，平均值為1204 m/s，變異係數為27%，顯示具有缺陷之杉木之應力波速具有較大之變異，進一步以徑弦向應力波速比（VR/VT）檢視材質之健全度時，指出當VR/VT 低於0.86 時，可視為內部具有缺陷。此外，以橫向打擊共振法評估40 株杉木立木，可以發現腐朽之杉木之頻率與直徑之乘積（FD 值）為181，亦明顯較低於健全者（FD 值為253）。

關鍵字

杉木 ； 應力波斷面影像技術 ； 橫向打擊共振法 ； 抗壓強度

並列摘要

The objectives of this study were to investigate the methods of detecting the internal qualities of standing trees, which were sampled from a 52-year-old China fir (Cunninghamia lanceolata) plantation in Huisun Experimental Forest Station, Experimental Forest Management Office of National Chung Hsing Univ., by using stress-wave method, stress-wave based tomographic technology, tapping resonance method and increment core sampling and to establish the relationships among the wood qualities and nondestructive testings. The experimental results showed that the maximum stress-wave velocity of China fir standing trees ranged from 1544~2835 m/s, the average velocity and coefficient of variation (CV) were 2222 m/s and 12%, respectively. However, the values of minimum stress-wave velocity, average velocity and CV of China fir standing trees were 532~1699 m/s, 1204 m/s and 27%, the experimental results also indicated that lower average velocity and higher variation were found in the decayed trees. In addition, the experimental results also indicated that internal quality of standing trees could be determined, while the V_R/V_T ratio lower than 0.86. Among the 40 sample trees, the average FD (product of the tree diameter and the resonance frequency obtained by lateral impact vibration) values in healthy trees and decayed trees were 253 and 181, respectively. Results also showed that the FD values of decayed trees were significantly lower than those of the healthy trees.

並列關鍵字

China fir ； Stress wave tomography ； Lateral impact vibration method ； Compression strength