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http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/20776
標題: | 光彈性顆粒流剪應力場分析之創新影像處理演算法 A novel image processing algorithm to measure shear stress field in a photoelastic granular flow |
作者: | Cheng-DA Yang 楊承達 |
指導教授: | 楊馥菱(Fu-Ling Yang) |
關鍵字: | 顆粒流,應力量測,光彈材料,光彈條紋角度演算法,梯度平方法, granular flow,photoelastic gradient square method,fringe angle of stress chain,stress measurements, |
出版年 : | 2020 |
學位: | 博士 |
摘要: | 為了描述顆粒流體內部的流變行為,流場內應力與運動行為的關連是最重要的資訊,而研究學者常透過顆粒碰撞、或摩擦的微觀行為來解讀其巨觀的動量傳遞現象,而本論文將利用光彈材料特有的性質來探討摩擦所生成的部分。我們使用光彈薄圓盤作為顆粒流的材料,準備了BCC與FCC堆積的靜態顆粒,在垂直與傾斜的狀態下拍攝光彈條紋,除了利用特有的梯度平方法(G^2)來度量正向應力。此外,由於觀察到光彈條紋的分布角度與側向應力有密切關係,本論文進一步發展影像處理方法以有效量測光彈條紋相對切向應力的條紋角度,首度完成光條紋方向與切向應力關係的濾定。 我們將所發展的影像處理方法與應力-條紋校正關係應用在光彈儲槽釋放實驗,以估算流場內部的正向應力與切向應力,再進一步應用於內摩擦係數的估算,首度完成一內應力的非接觸性量測。 To understand granular flow rheology, we need detailed information on the internal stress that can result from inter-particle collision or friction. In this work, we use photoelastic disks to create a static granular packing and a silo discharging flow. The fringe patterns developed in the loaded disks are exploited to estimate the bulk stress field from frictional contacts. We modified the gradient square method (G^2) in literature for normal stress measurement and developed a through image analysis routine to estimate a bulk fringe direction angle for tangential stress evaluation. As the fringe pattern is sensitive to the loading configuration, special efforts were made here to calibrate the fringe-based stress measurement techniques under static BCC and FCC packing. As a result, the normal and the tangential stress can be evaluated in terms of the fringe light intensity, fringe direction angle, and the packing solid volume fraction. The technique is applied to a granular silo flow to concurrently extract the normal and the tangential stress field due to inter-particle friction. This allows us to achieve an indirect measurement of frictional bulk friction coefficient for the first time in the literature. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/20776 |
DOI: | 10.6342/NTU202004080 |
全文授權: | 未授權 |
顯示於系所單位: | 機械工程學系 |
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檔案 | 大小 | 格式 | |
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U0001-1908202013593000.pdf 目前未授權公開取用 | 6.22 MB | Adobe PDF |
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