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題 名 | Detection of Internal Holes in Swietenia mahagoni Disks Using a Stress Wave Device=以應力波儀偵測桃花心木圓盤內部孔洞之研究 |
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作 者 | 許富蘭; 李金梅; 黃國雄; 黃彥三; | 書刊名 | 臺灣林業科學 |
卷 期 | 27:2 2012.06[民101.06] |
頁 次 | 頁191-200 |
分類號 | 436.18 |
關鍵詞 | 偵測解析度; 非破壞試驗; 應力波; 桃花心木; 穿透時間; 音速; Detection resolution; Nondestructive test; Stress wave; Swietenia mahagoni; Transit time; Sound velocity; |
語 文 | 英文(English) |
中文摘要 | 本研究旨在探討以雙偵測器之應力波儀器預測樹幹內孔洞大小及位置之可行性,此外,更試圖探討此技術之解析度。為模擬自然界中內含腐朽空洞之樹幹,將桃花心木(Swietenia mahagoni)圓盤上鑿取三種不同位置之人工孔洞,並逐漸增加孔洞直徑,分別以應力波技術進行評估,以探究不同位置及大小之孔洞對於應力波在圓盤內傳遞表現之影響。試驗結果顯示,隨著孔洞直徑的增加,應力波穿透圓盤所需的時間亦隨之增加。應力波穿透缺陷材與健全材之相對時間比(RT)亦隨孔洞佔健全材之相對直徑比(RD)而明顯增加,此趨勢在徑向十分明顯,在弦向則深受孔洞位置影響:當孔洞位接近兩偵測器時,RT隨RD增加而增加;當孔洞位置遠離兩偵測器時,RT與RD呈不相關,意即徑向RT可做為預測孔洞大小之判斷指標,而弦向RT穿透時間率可做為預測孔洞位置指標而加以定位。由於音速降低10%為樹木腐朽之基準,故定義相對音速比(RV)達0.9時之孔洞為應力波的解析度,由結果得知對於中央孔洞之圓盤,應力波的解析度為相對直徑0.29(相對面積8.4%)。此外,由於RD達0.7時為危木之基準,故建議當被測樹之RV小於0.66時,該樹應列為危木並受適當管理。本試驗證實,雙偵測器應力波技術提供一可檢視立木內部缺陷存在與否、形態大小及定位之非破壞檢測法,且可作為樹木風險評估的有效工具。 |
英文摘要 | The objectives of this study were to evaluate the feasibility of detecting different sizes and positions of hidden defects in trees using a 2-sensor stress wave device. In addition, we attempted to evaluate the detection resolution of the stress wave method which was rarely discussed previously. Artificial holes were created in Swietenia mahagoni disks to imitate natural decay in a trunk and were then detected using stress waves. The results revealed that as the diameter of the artificial hole increased, the radial transit time of the disk increased. This increasing tendency was repeated in the relationship between the radial relative transit time (RT) and the relative hole diameter (RD) and was discordant in the tangential direction. The tangential RT was greatly influenced by the position of the hole: it was highly related to the RD when the hole was near the 2 sensors; while it is not related to the RD when the hole was far from the 2 sensors. We also found that detection resolutions of stress waves, defined as the diameter or area ratio when the radial velocity had decreased by 10%, were 0.29 and 8.4%, respectively. A tree was considered to be decayed when the relative velocity (RV) was < 0.9 and was considered hazardous when the RV was < 0.66 with a central hole. On the basis of the results obtained, it appears that a 2-sensor stress wave device allows the nondestructive inspection of the presence, size, and location of defects in trees and could be a cost-effective way to perform tree risk assessments. |
本系統中英文摘要資訊取自各篇刊載內容。