颗粒流润滑力链演变及动力学状态的研究
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摘要
为了研究颗粒流润滑状态下的力链演变及动力学状态,基于非连续介质力学的离散单元法理论建立了剪切平行板间颗粒流润滑的分析模型,并利用该分析模型研究了颗粒流润滑的接触力分布规律、力链网络的演变规律及动力学状态、力链的分布及对颗粒流润滑系统的影响。数值分析结果表明,颗粒润滑介质间的法向接触力、切向接触力和接触力分布均按幂函数规律变化,颗粒流润滑系统的承载和动力学特性主要受法向接触力的影响;颗粒润滑介质的动力学状态可以转变为阻塞态、准静态流、慢速流和快速流4种状态,在4种不同的动力学状态下,总力链的大小在阻塞态、准静态流和慢速流时较大,而在快速流时则较小;在颗粒润滑介质的动力学状态从快速流转变为慢速流和准静态流时,弱力链的数目明显减少,超强力链和强力链的数目明显增加,与此同时,颗粒润滑介质的流动速度和力链解构与重构的速度则明显减缓。
To reveal the force chain evolution and dynamic state under granular flow lubrication,an analytical model of granular flow lubrication between sheared parallel plates is established based on the discrete element theory of continuum mechanics.Using this analytical model,the contact force distribution rule,the force chain evolution rule and dynamic state,as well as the force chain distribution and its influence on the granular flow lubrication system,are studied.Numerical analytical results show that the probability distributions of normal contact force,tangential contact force,and contact between granular lubrication medium all obey the power law;the load bearing and dynamic characteristics of granular lubrication system are mainly influenced by normal contact force;and the dynamic state of granular lubrication medium can be transformed into four states of jamming state,quasi-static state,slow flow and fast flow.Under these four flow states,the magnitude of total force chain is large in the jamming state,quasistatic state and slow flow state,but small in the fast flow state.When the dynamic state of granular lubrication medium transforms from fast flow state to slow flow state or quasi-static state,the number of weak force chains is deceased and the number of strong and super force chains is increased.And in the meantime,the flow speed of granular lubrication medium as wellas the deconstruction and reconstruction speeds of force chains slows down.
To reveal the force chain evolution and dynamic state under granular flow lubrication,an analytical model of granular flow lubrication between sheared parallel plates is established based on the discrete element theory of continuum mechanics.Using this analytical model,the contact force distribution rule,the force chain evolution rule and dynamic state,as well as the force chain distribution and its influence on the granular flow lubrication system,are studied.Numerical analytical results show that the probability distributions of normal contact force,tangential contact force,and contact between granular lubrication medium all obey the power law;the load bearing and dynamic characteristics of granular lubrication system are mainly influenced by normal contact force;and the dynamic state of granular lubrication medium can be transformed into four states of jamming state,quasi-static state,slow flow and fast flow.Under these four flow states,the magnitude of total force chain is large in the jamming state,quasistatic state and slow flow state,but small in the fast flow state.When the dynamic state of granular lubrication medium transforms from fast flow state to slow flow state or quasi-static state,the number of weak force chains is deceased and the number of strong and super force chains is increased.And in the meantime,the flow speed of granular lubrication medium as wellas the deconstruction and reconstruction speeds of force chains slows down.
引文
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[2]王伟,刘小君,焦明华,等.颗粒运动和形位参数对颗粒流润滑特性的影响规律[J].机械工程学报,2009,45(7):101-107.WANG Wei,LIU Xiaojun,JIAO Minghua,et al.Influences of several slider’s parameters on particles flow lubrication characteristics[J].Journal of Mechanical Engineering,2009,45(7):101-107.
[3]TIMMA K,MYANT C,SPIKS H A,et al.Particulate lubricants in cosmetic applications[J].Tribology International,2011,44(12):1695-1703.
[4]IORDANOFF I,BERTHIER Y,DESCARTES S,et al.A review of recent approaches for modeling solid third bodies[J].Journal of Tribology,2002,124(10):725-735.
[5]HESHMA H.The rheology and hydrodynamics of dry powder lubrication[J].Tribology Transactions,1991,34(3):433-439.
[6]王伟,孔俊超,顾伟,等.温成形摩擦界面粉末润滑层宏微观特性的试验研究[J].摩擦学学报,2016,36(2):233-239.WANG Wei,KONG Junchao,GU Wei,et al.Experimental study on macro and micro characteristics of powder lubricant layer in frictional warm interface[J].Tribology,2016,36(2):233-239.
[7]孟凡净,刘焜,王伟.颗粒润滑界面的流态和润滑特性的研究[J].中国机械工程,2014,25(19):2562-2567.MENG Fanjing,LIU Kun,WANG Wei.Flow pattern and lubrication features in particulate lubrication interface[J].China Mechanical Engineering,2014,25(19):2562-2567.
[8]WANG W,LIU Y,ZHU G Q.Using FEM-DEM coupling method to study three-body friction behavior[J].Wear,2014,318(1/2):114-123.
[9]ELKHOLY K N,KHONSARI M M.Experimental investigation on the stick-slip phenomenon in granular collision lubrication[J].Journal of Tribology,2008,130(2):021302.
[10]孙其诚,王光谦.静态堆积颗粒中的力链分布[J].物理学报,2008,57(8):4667-4674.SUN Qicheng,WANG Guangqian.Force distribution in static granular matter in two dimensions[J].Acta Physica Sinica,2008,57(8):4667-4674.
[11]SAZZAD M M,SUZUKI K,RAZAVI A M F.Macro-micro responses of granular materials under different b values using DEM[J].International Journal of Geomechanics,2012,12(3):220-228.
[12]CUNDALL P A,STRACK A.A discrete numerical model for granular assemblies[J].Geotechnique,1979,29(1):47-65.
[13]曹秒艳,董国疆,赵长财.基于离散元法的固体颗粒介质传力特性研究[J].机械工程学报,2011,47(14):62-69.CAO Miaoyan,DONG Guojiang,ZHAO Changcai.Research on pressure-transfer characteristics in the solid granule medium forming based on the discrete element method[J].Journal of Mechanical Engineering,2011,47(14):62-69.
[14]GU X Q,YANG J,HUNAG M S.DEM simulations of the small strain stiffness of granular soils:effect of stress ratio[J].Granular Matter,2013,15(3):287-298.
[15]CAMPBELL C S.Granular material flows-an overview[J].Powder Technology,2006,162(3):208-229.