複合式非破壞檢測佐探類岩材料於單刀與雙刀貫切之破壞機制

Monitor Fracture Characteristics of Rock-Like Material under Single and Double Indentation by Coupled Nondestructive Techniques

胡光宇(Kuang-Yu Hu)

指導教授 ： 陳立憲

國立臺北科技大學/工程學院/土木與防災研究所/碩士(2007年)

https://doi.org/10.6841/NTUT.2007.00317

摘要

台灣由於山多平地少，人口主要分佈於平原區，發展至今，已漸趨飽和，因此地下隧道開挖工程與日俱增。惟其機械式掘削開挖過程之力學機制仍屬渾濛，因此本研究以建立一正向楔型貫切破壞試驗（normal wedge indentation fracture test）並佐以電子點紋干涉術（Electronic Speckle Pattern Interferometry, ESPI）為主；及聲射（Acoustic Emission, AE）技術為輔之複合非破壞檢測，進行類岩接觸破壞機理之探求，俾為工程實務之佐參。
於無圍壓系列實驗中，以裂縫開口位移（Crack Opening Displacement, COD）之量測作為油壓伺服器封閉迴路（closed-loop）之回饋控制信號，藉此穩定試驗過程之峰後行為；求得完整加載歷程曲線與相對應之非破壞檢測數據進行研析。
研究面向計分三大主軸：（a）探討鑽刀幾何形狀與材料之顆粒尺寸（grain size）在不同應力場狀況下，對破壞力學之破壞缺陷長度（intrinsic flaw length）之關聯性進行探討。藉電子點紋干涉術所得干涉影像，確認變形不連續之初裂發生位置乃在臨界彈-塑性界面上，並由發生瞬間之影像推判破壞力學中材料之破壞缺陷長度，再與線彈性破壞力學（Linear Elastic Fracture Model, LEFM）之張裂模式（opening mode）之理論做一比對，求得楔型刀角之增加，使最大貫切力因之增大；而相對應之臨界貫切深度反而減小，但刀角對材料破壞之缺陷尺寸之影響甚微。因缺陷尺寸為材料破壞力學中之材料參數，與材料本身的顆粒尺寸（grain size）存在正相關；（b）承襲前人文獻對單一刀頭貫切之探討，進而施作雙刀頭貫切試驗，期能理解刀頭與刀頭間之互制行為，並進而分析比較巨微觀尺度裂縫行為之一致性。由實驗得知，隨刀頭間距之縮短，裂縫之初裂方位，會偏離原垂直之貫切軸，偏離之角度隨間距之縮短而增加，而裂衍路徑朝朝側向自由偏離之趨勢而得以觀察。因此，由研究得知，適當之刀距安排有助於機械開挖效率之提升；（c）同步化整合電子點紋干涉術與聲射技術兩項非破壞檢測以探求貫切試驗之破壞機制，過程中，先分別於變形連續階段探討彈-塑性界面以驗證複合非破壞檢測之可行與一致；再於變形不連續階段對裂端微塑性區（process zone）進行適確性之探討。
綜計三大研究主軸之實驗成果與相對應之理論比對解析，求得頗為一致之趨勢。

關鍵字

電子點紋干涉術 ； 聲射 ； 貫切破壞 ； 裂縫開口位移 ； 破壞缺陷長度 ； 裂端微塑區

並列摘要

Nowadays, extensive uses of full-faced mechanical boring method in recent years. But the relationship between mechanical indenter and rocks in cutting process is still not clear, so, this study set up normal wedge indentation fracture test combines with electronic speckle pattern interferometry (ESPI) and acoustic emission (AE) for nondestructive test to monitor the contact fracture characteristics of rock material, in order to get some data for in situ.
To control the post-peak stability to obtain a complete loading curve, and to investigate nondestructive techniques data, the crack opening displacement (COD) is used to be a close-loop control unconfinement case. This study can divide three parts: (a) By varying wedge angle of cutter and grain size of rock-like materials, experimental observation of intrinsic flaw length was made. Furthermore, the intrinsic flaw length of fractured material was monitored by optical interferometry and then compared with the analytical solution based upon the opening mode of linear elastic fracture model (LEFM). We found that the blunter wedge angle of indenter, the larger the maximum indentation force. In addition, the indentation pressure and the critical indentation depth would decrease as increasing wedge angle. Because, intrinsic flaw length is treated as a material property in fracture mechanics. (b) Follow previous paper about single indenter, in order to understand double indenters behavior, we do double indenters and analysis the relation between micro and macro crack behavior. Testing results indicate the distance of indenters decreases with direction of crack initiation deviate from original vertica line, deviate angle increases with the distance of indenters decreases. So, proper indenter distance contribute to machinery excavate has help about the improvement of cutting efficiency. (c) Synchronize electronic speckle pattern interferometry and acoustic emission to investigate fracture characteristics of indentation test, first, monitor the radius of elasto-plastic interfacial to prove coupled nondestructive techniques is fine to work in displace-continuity, second, monitor the process zone about fitting and proper in displace-discontinuity.
We get rather unanimous trend in experiment achievement compared with corresponding theory.

並列關鍵字

Electronic speckle pattern interferometry ； Acoustic emission ； Indentation fracture ； Crack opening displacement ； Intrinsic flaw length ； Process zone

參考文獻

【1】 李昶佑，「應用電子點紋干涉術探討岩石貫切過程之破壞演化及破裂特徵」，碩士論文，國立台北科技大學土木工程系，台北，2006。

【10】Butters, J. N. and Leendertz, J. A., “Holographic and video techniques applied to engineering mesurements,” Trans. Inst. Meas. Control, vol.4, pp.349-354, 1971.

initiation under an indentor,” In P. Rossmanith (Ed.), Proc. 2nd Int. Conf. On Mechanics of Jointed and Faulted Rock (MJFR-S), Vienna, Austria, 1995.

【14】Gabor, D., “A enw microscopic principle,” Nature, vol.161, pp.777-778, 1948.

【15】Hertz, H. H., “Hertz's miscellaneous papers,” London: Macmillan, 1896.