不同形狀及摩擦係數之顆粒物質受束制壓力負載之力學分析; Effects of Particle Friction and Particle Shape on the Mechanical Response of Granular Solid under Confined Compression

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題名:	不同形狀及摩擦係數之顆粒物質受束制壓力負載之力學分析;Effects of Particle Friction and Particle Shape on the Mechanical Response of Granular Solid under Confined Compression
作者:	彭瀚弘;Peng,Han-hong
貢獻者:	機械工程學系
關鍵詞:	應力;束制壓力負載實驗;顆粒體;摩擦係數;顆粒形狀;stress;confined compression test;granular material;coefficient of friction;particle shape
日期:	2013-07-22
上傳時間:	2013-08-22 12:15:34 (UTC+8)
出版者:	國立中央大學
摘要:	本研究主旨在探討具不同摩擦係數及形狀的顆粒物質在壓克力罐體容器中受束制壓力負載之力學行為。利用廣義虎克定律將三個不同高度位置所量測的應變計算應力值，分析在不同高度下不同顆粒摩擦係數及形狀之力學行為。本研究選擇五種不同生鏽程度之鋼球探討顆粒摩擦係數對顆粒體與罐體間力學行為之影響；此外，選擇球形、二款橢圓形、藥丸型、雙球形共五種不同形狀之ABS顆粒進行束制壓力實驗，並將實驗結果分別依不同顆粒形狀、顆粒長寬比、顆粒角數進行比較分析以探討其在束制壓力條件下之力學響應。實驗結果顯示，在束制壓力條件下，增加顆粒之摩擦係數會提升顆粒體內部的互鎖效應，導致顆粒不易水平側向位移或擠壓罐壁，也提升顆粒體與罐壁間的摩擦效應，而隨著顆粒摩擦係數增加，顆粒體內的孔隙率也會隨之增加。將球形、橢圓形、藥丸形顆粒之實驗結果進行比較，藥丸形顆粒擁有較明顯之互鎖效應，使得整體顆粒體之剛性較大，同時接觸壁面的顆粒不易產生滑動，造成整體壁面與顆粒體摩擦力量降低。而相較於球形及藥丸形顆粒，橢圓形顆粒之側向壓力係數較大，代表橢圓形顆粒在束制壓力條件下較其他兩種顆粒形狀易側向移動。針對橢圓形顆粒增加其長寬比不僅提升整體顆粒體之初始填充密度及剛性同時也提升其側向壓力係數。另一方面，在束制壓力負載下，增加顆粒角數會提升顆粒體內部的互鎖效應，使得顆粒不易滑動及轉動，導致初始孔隙率較大且水平應力以及側向壓力係數較小，但由於增加顆粒角數使得初始孔隙率較大，造成其整體剛性只有些許提升。 The purpose of this study is to investigate the effects of particle friction and shape on the interaction between a granular assembly and an acrylic cylinder and the relevant mechanical responses at various positions under a confined compression condition. Variations of wall strains are measured through strain gages at three given axial positions and used to calculate the relevant stresses through a generalized Hooke’s law. Steel spheres of five rust levels are selected to characterize the effect of particle friction. In addition, the experimental results of five selected particle shapes, namely spherical, ellipsoidal I, ellipsoidal II, cylindrical, and paired ABS particles, are compared to characterize the effects of particle shape, aspect ratio, and particle angularity. Experimental results show that an increase in particle friction causes a greater interlocking effect between particles, resulting in a greater difficulty for particles in the granular assembly to move and press laterally under a confined compression condition. In addition, the frictional force between particles and cylindrical wall also increases as the particle friction increases. The initial assembly height increases with increasing particle friction. For spherical, ellipsoidal, and cylindrical particles, cylindrical particles have a greater interlocking effect, resulting in a greater stiffness of the granular assembly. In addition, a larger extent of decrease in the bulk wall friction is observed for the cylindrical particles indicating a smaller extent of mobilization of the particles beside the cylinder wall. Compared with spherical and cylindrical particles, ellipsoidal particles have a greater lateral pressure ratio. It indicates a greater extent of lateral movement for ellipsoidal particles under confined compression loading. An increase in the aspect ratio of ellipsoidal particles not only causes a higher packing density and a greater stiffness of the granular assembly, but also increases the extent of lateral movement of particles and induces a greater lateral pressure ratio. On the other hand, a higher particle angularity results in a greater interlocking and a greater difficulty for the particles in the granular assembly to slide and rotate. It increases the initial porosity of the assembly and lateral pressure ratio to a small extent under a confined compression condition. Due to a larger initial porosity in the particles of a greater angularity, the stiffness of the granular assembly of paired particles only increases slightly in comparison with the spherical particles
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