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論文中文名稱:分離元素法於接觸破壞之刀刃磨耗與雙刀效應之模擬暨耦合有限差分法之數值初探 [以論文名稱查詢館藏系統]
論文英文名稱:Distinct Element Approach to the Effect of Wear Flat and Doubled- indenters on Contact Fracture and the Study of Coupled Numerical Method Using Distinct/Finite Different Element [以論文名稱查詢館藏系統]
院校名稱:臺北科技大學
學院名稱:工程學院
系所名稱:土木與防災研究所
出版年度:97
中文姓名:王紹宇
英文姓名:Shaw-Yu Wang
研究生學號:95428028
學位類別:碩士
語文別:中文
口試日期:2008-07-22
論文頁數:132
指導教授中文名:陳立憲
口試委員中文名:林世聰;陳堯中;壽克堅
中文關鍵詞:分離元素法有限差分法數值耦合貫切破壞粒間微裂
英文關鍵詞:Distinct element methodFinite element methodNumerical coupleIndentation fracture testMicro-crack
論文中文摘要:邇來台灣地區利用機械式開挖所遭遇之地質狀況愈趨困難、複雜且工程尺度規模日增,是故對於隧道機械式開挖之安全性與可行性亟需加強瞭解。故本研究以分離元素法(Distinct Element Method)之二維數值軟體PFC2D為本;進行模擬楔形刃口正向貫入岩材之接觸破壞行為,以數值耦合(PFC2D&FLAC)之方式,先就單壓及巴西試驗作校驗,再應用於貫切破壞之模擬,並比對貫切行為之理論模式與相關實驗數據,俾能提供隧道工程與地下管道機械開挖之安全性與施工效率探討之佐證。
本研究採用高強度岩類之花崗岩進行數值模擬,求算貫切破壞之力學特徵,藉由改變:(1)楔形刃口之磨耗(Wear Flat)特徵,以模擬切削刀具之耗損現象;(2)雙楔形刃口之影響間距,以模擬雙削刀同時掘挖時之互制效應。本研究並於國內首次使用分離元素法軟體PFC2D與有限差分法軟體FLAC兩二維數值軟體進行貫切破壞之數值耦合運算,利用耦合概念加速分析之運算速度,兩軟體之連結透過力與速度之交換傳遞。先以(1)單壓試驗(Uniaxial Compression Test);及(2)巴西試驗(Brazilian Test)校驗耦合機制之適確性後,始應用於(3)貫切試驗之解析。
由數值模擬之結果得知,當楔尖磨耗增加時,岩材產生脆性破壞之初裂貫切力隨之增加,而其對應之臨界貫入深度則亦微幅增加,故磨耗效應確會干擾岩材脆性破壞機制之形成;而由雙刀效應之模擬,可知兩貫切刀楔互制影響之破壞裂縫生、衍行為,當雙刀相對刀距 為 時,岩材之破壞特徵有明顯變化,即定義此為臨界相對刀距,並探討其產生脆性破壞所需初裂貫切力之變動範圍及應力重疊區,由此得知適當之刀距安排將有助於減少能量之耗損。
於數值耦合之部分,經由單壓與巴西試驗之模擬,並比對單一數值軟體PFC2D模擬之結果,求算得知單壓強度、張力強度皆相吻合;且具相符之裂縫生、衍趨勢,將此耦合機制運用於貫切試驗,並與理論解進行比對後亦得良好之對應,證實耦合機制之可行性。
此一實驗室尺度之貫切破壞模擬所建立之模組概念,未來應可進一步應用於工程尺度之隧道開挖實例,以期將此構想落實運用於地下開挖之實務。
論文英文摘要:Recently some cases of underground mechanical excavations encountered the complex structural geological conditions become of difficulty in Taiwan. To obtain both construction security and the feasibility in tunnel engineering, and to understand the contact mechanism in these complex cutting cases, this numerical approach simplifies normal wedge cutter(s) indented into intact rock for simulating the process of fragmentation using a two-dimensional tool of distinct element method, so-named PFC2D. This numerical simulation uses the high strength granite to carry on the indentation fracture process to investigate two key effects: (1) wear flat of indenter due to cutting abrasion, (2) doubled-indenters on the failure characteristics such as maximum indentation force, the critical elastoplastic radius as well as the crack initiation/propagation.
To observe global/local failure in macro- and micro-scope respectively, and to speed up numerical approach for some cases, this research also tries to combine PFC2D software with the finite difference method of FLAC code to carry out three issues: (1) uniaxial test; and (2) Brazilian test to assess this linking/coupling numerical algorism, then (3) indentation fracture test in rock by a single-cutting tool.
This analytical approach shows that, as increasing the wear flat of indenter, the maximum indentation force needed to develop critical plastic zone increases and its corresponding critical penetration depth also increases slightly, Note that the effect of wear flat will affect rock fracture behavior. In addition, regarding the simulation of the effect of doubled-indenters, result shows that two adjacent indenters may interact each other as reaching the transient/critical relative space between indenters (Sr,c) of 2~3. It dicpicts that a proper spacing arrangement between indenters may enhance a efficient mechanical cutting due to the less required maximum indentation force and energy dissipation.
By coupling numerical approach of PFC2D and FLAC to simulate both uniaxial test and Brazilian test, the results are agree with theoretical solutions in terms of elastoplastic interface, and also match to the results performed from PFC2D simulation in terms of the comparison of the uniaxial compressive strength (qu) , tensile strength (σt), and the pattern of crack propagation. It means that the feasibility of this numerical coupling algorism to the indentation problem is verified in this study.
To sum up, the numerical model to indentation fracture mechanism was established in the laboratory scale, future works to simulate tunnel excavation in field could be conducted following this conceptual numerical model in the future.
論文目次:中文摘要 i
英文摘要 iii
誌謝 v
目錄 vi
表目錄 x
圖目錄 xi
第一章 緒論 1
1.1 研究動機與目的 1
1.2 研究方法及範圍 1
1.3 論文架構與分章概述 3
第二章 文獻回顧 5
2.1 分離元素法之介紹 5
2.2 拉格朗日分析法之介紹 6
2.3 貫切行為之特徵及研究發展 7
2.3.1 延性破壞-廣義孔洞擴展模式 11
2.3.2 脆性破壞-線彈性破壞力學之破壞模式 16
2.4 貫切破壞之影響因素 19
2.4.1 磨耗效應之影響 19
2.4.2 雙刀效應之影響 22
2.5 數值耦合之相關研究 23
第三章 數值模擬分析方法 26
3.1 PFC2D之軟體概述 26
3.1.1 PFC2D之基本功能與特性 27
3.1.2 PFC2D之基本假設 28
3.1.3 PFC2D之運算邏輯 28
3.2 PFC2D之參數種類 29
3.2.1 顆粒元素參數 29
3.2.2 鍵結力參數 31
3.2.3 牆面元素參數 33
3.2.4 微觀參數檢核之步驟 34
3.3 PFC2D模型材料生成程序 35
3.4 FLAC之概述 40
3.4.1 FLAC之運算原理 41
3.4.2 FLAC之組合律模式 42
3.5 數值耦合之概述與運算邏輯 42
3.5.1 數值耦合之概述 43
3.3.2 數值耦合之運算邏輯 45
第四章 數值模擬與分析:單一數值軟體PFC2D 47
4.1 模型幾何參數之探討 50
4.1.1 試體外幾何條件之探討 50
4.1.2 試體內幾何(顆粒元素)條件之探討 50
4.1.3 微巨觀參數之校驗 52
4.2 貫切試驗之參數說明 55
4.3 貫切試驗之模擬檢核 58
4.3.1 貫切力曲線與巨觀破壞行為 58
4.3.2 彈-塑性區界面發展之探討 60
4.3.3 數值結果與理論解析之核驗 68
4.4 楔尖磨耗效應之影響 69
4.4.1 磨耗效應於貫切力曲線及能量之探討 70
4.4.2 彈-塑性界面發展之探討 71
4.4.3 數值與理論解之核驗 76
4.5 雙刀效應之影響 77
4.5.1 雙刀貫切於貫切力及能量之探討 78
4.5.2 雙刀效應之裂縫生、衍模式探討 80
第五章 數值模擬與分析:數值耦合PFC2D&FLAC 93
5.1 數值耦合之形式 93
5.2 單壓試驗之模擬驗證 94
5.2.1 單壓試驗之單一數值軟體模擬:PFC2D 95
5.2.2 單壓試驗數值耦合之模擬:PFC2D&FLAC 96
5.3 巴西試驗之模擬驗證 101
5.3.1 巴西試驗之單一數值軟體模擬:PFC2D 102
5.3.2 巴西試驗之數值耦合之模擬:PFC2D&FLAC 105
5.3.3 巴西試驗模擬結果之校驗比對 107
5.4 貫切試驗之模擬驗證 108
5.4.1 貫切試驗之單一數值軟體模擬:PFC2D 108
5.4.2 貫切試驗之數值耦合之模擬:PFC2D&FLAC 108
5.4.3 貫切試驗模擬結果之校驗比對 115
第六章 結論與建議 116
6.1 結論 116
6.2 建議 119
參考文獻 120
附錄 委員意見回覆表 126
符號對照表 129
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