用离散元方法研究颗粒外形对摩擦机理的影响
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摘要
为了揭示颗粒外形对无粘性散体摩擦机理的影响,将无粘性颗粒材料之间的摩擦作用分解为颗粒间宏观咬合和微观咬合摩擦,运用不规则外形颗粒离散元建模方法,进行撞击模拟和自然安息角模拟,研究颗粒外形对微观咬合摩擦和宏观咬合作用的影响.数值计算结果表明,不规则外形颗粒集料摩擦因数近似为接触面摩擦因数的2倍,椭球体集料摩擦因数与接触面摩擦因数近似相等;颗粒外形不同使得颗粒运动状态呈现出滑动或滚动特征,并影响其宏观咬合特性及颗粒集料的摩擦性能.
In order to reveal the effects of particle shape on friction mechanism,frictions among non-viscous particles were decomposed into the macro biting-force and the mesoscopic biting-force.Impact and angle-of-repose(AOR) numerical tests were conducted to study the effects of particle shape on macro biting-force and mesoscopic biting-force by modeling irregular shape particles using discrete element method.The results of numerical tests show that the friction coefficient of irregularly shaped particles is nearly two times its interface friction coefficient,while the friction coefficient of ellipsoid particles is approximately equal to the interface friction coefficient.Meanwhile,different particle shapes endowed the particles with rolling or slipping characteristics,and influence the macro biting-force and the granular friction behavior.
In order to reveal the effects of particle shape on friction mechanism,frictions among non-viscous particles were decomposed into the macro biting-force and the mesoscopic biting-force.Impact and angle-of-repose(AOR) numerical tests were conducted to study the effects of particle shape on macro biting-force and mesoscopic biting-force by modeling irregular shape particles using discrete element method.The results of numerical tests show that the friction coefficient of irregularly shaped particles is nearly two times its interface friction coefficient,while the friction coefficient of ellipsoid particles is approximately equal to the interface friction coefficient.Meanwhile,different particle shapes endowed the particles with rolling or slipping characteristics,and influence the macro biting-force and the granular friction behavior.
引文
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[4]杨庆华,姚令侃,杨明.地震作用下松散堆积体崩塌的颗粒流数值模拟[J].西南交通大学学报,2009,44(4):580-584.YANG Qinghua,YAO Lingkan,YANG Ming.Particleflow numerical simulation of landslip of loose slopeunder seismic loading[J].Journal of Southwest JiaotongUniversity,2009,44(4):580-584.
[5]LU M,MCDOWELL G R.The importance of modellingballast particle shape in the discrete elementmethod[J].Granular Matter,2007,9(1/2):69-80.
[6]XIA M,ZHOU K P.Particle simulation of the failureprocess of brittle rock under triaxial compression[J].International Journal of Minerals,Metallurgy andMaterials,2010,17(5):507-513.
[7]CHO N,MARTIN C D,SEGO D C.Development of ashear zone in brittle rock subjected to direct shear[J].International Journal of Rock Mechanical and MiningSciences,2008,45(8):1335-1346.
[8]TOMOFUMI K,LANRU J.Effects of model scale andparticle size on micro-mechanical properties and failureprocesses of rocks-A particle mechanics approach[J].Engineering Analysis with Boundary Elements,2007,31:458-472.
[9]COETZEE C J,ELS D N J,DYMOND G F.Discreteelement parameter calibration and the modelling ofdragline bucket filling[J].Journal of Terramechanics,2010,47(1):33-44.
[10]李仕雄,姚令侃,蒋良潍.临界状态下沙堆大规模坍塌的机制[J].西南交通大学学报,2004,39(3):366-370.LI Shixiong,YAO Lingkan,JANG Liangwei.Mechanism of sandpile avalanche in critical state[J].Journal of Southwest Jiaotong University,2004,39(3):366-370.
[11]杜欣,曾亚武,高睿,等.基于CT扫描的不规则外形颗粒三维离散元建模[J].上海交通大学学报,2011,45(5):711-715.DU Xin,ZENG Yawu,GAO Rui,et al.3-Dmodelling of irregular shape particles for discreteelement method based on X-ray tomography[J].Journal of Shanghai Jiaotong University,2011,45(5):711-715.
[12]DU Xin,ZENG Yawu,GAO Rui,et al.Modellingmethods and error analysis of deformable and non-deformable real particles[J].Advanced MaterialResearch,2011(217/218):642-646.
[13]CUNDALL P A.A computer model for simulatingprogressive,large scale movements in blocky rocksystems[C]∥Proceedings of the InternationalSymposium on Rock Mechanics.Nancy:[s.n.],1971:129-136.
[14]CUNDALL P A,STRACK O D L.A discrete elementmodel for granular assemblies[J].Geotechnique,1979,29(1):47-65.
[15]CUNDALL P A,HART R.Numerical modeling ofdiscontinua[J].Engineering Computations,1992,9(2):101-113.
[16]WU Aixiang,SUN Yezhi.Granular dynamic theoryand its applications[M].New York:Springer-VerlagGmbh Berlin Heidelberg,2007:98-106.
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