The 3D needled C/SiC brake materials modified with graphite were prepared by a combined process of the chemical vapor infiltration,slurry infiltration and liquid silicon infiltration process.The microstructure and fri...The 3D needled C/SiC brake materials modified with graphite were prepared by a combined process of the chemical vapor infiltration,slurry infiltration and liquid silicon infiltration process.The microstructure and frictional properties of the brake materials were investigated.The density and open porosity of the materials as-received were about(2.1±0.1)g/cm3and(5±1)%,respectively.The brake materials were composed of 59%C,39%SiC,and 2%Si(mass fraction).The content of Si in the C/SiC brake materials modified with graphite was far less than that in the C/SiC brake materials without being modified with graphite,and the Si was dispersed.The braking curve of the 3D needled C/SiC modified with graphite was smooth,which can ensure the smooth and comfortable braking.The frictional properties under wet condition of the 3D needled C/SiC modified with graphite showed no fading.And the linear wear rate of the C/SiC modified with graphite was lower than that of the C/SiC unmodified.展开更多
The discrete element method(DEM) has been widely used to simulate microscopic interactions between particles.Screening is a deeply complicated process when considering the law of motion for the particles,themselves.In...The discrete element method(DEM) has been widely used to simulate microscopic interactions between particles.Screening is a deeply complicated process when considering the law of motion for the particles,themselves.In this paper,a numerical model for the study of a particle screening process using the DEM is presented.Special attention was paid to the modeling of a vibrating screen that allows particles to pass through,or to rebound,when approaching the screen surface.Inferences concerning screen length and vibrating frequency as they relate to screening efficiency were studied.The conclusions were:three-dimensional simulation of screening efficiency along the screen length follows an exponential distribution;when the sieve vibrates over a certain frequency range the screening efficiency is stable;and,higher vibration frequencies can improve the handling capacity of the screening machine.展开更多
Three-dimensional tracking of submicron particles in flows in a micro-channel was carried out using in-line holographic microscopy.A fixed single 0.5 μm fluorescent particle was identified and isolated from dust part...Three-dimensional tracking of submicron particles in flows in a micro-channel was carried out using in-line holographic microscopy.A fixed single 0.5 μm fluorescent particle was identified and isolated from dust particles or overlapped particle pair using the laser induced fluorescent(LIF) method.Then in-line microscopic holograms of the fixed single particle were obtained at different positions on the optical axis,i.e.the defocus distances.The holograms of the single particle were used as the model templates with the known defocus distances.The particles in the in-line microscopic holograms of flow in the microchannel were then identified and located to obtain their two-dimensional positions.The defocus distances of those particles were determined by matching each hologram pattern to one of the model templates obtained in the single particle test.Finally the three-dimensional position and velocity of each particle were obtained.展开更多
基金Project(46-QP-2009)supported by the Research Fund of State Key Laboratory of Solidification Processing(NWPU),ChinaProject supported by the Program for Changjiang Scholars and Innovative Research Team in Chinese University
文摘The 3D needled C/SiC brake materials modified with graphite were prepared by a combined process of the chemical vapor infiltration,slurry infiltration and liquid silicon infiltration process.The microstructure and frictional properties of the brake materials were investigated.The density and open porosity of the materials as-received were about(2.1±0.1)g/cm3and(5±1)%,respectively.The brake materials were composed of 59%C,39%SiC,and 2%Si(mass fraction).The content of Si in the C/SiC brake materials modified with graphite was far less than that in the C/SiC brake materials without being modified with graphite,and the Si was dispersed.The braking curve of the 3D needled C/SiC modified with graphite was smooth,which can ensure the smooth and comfortable braking.The frictional properties under wet condition of the 3D needled C/SiC modified with graphite showed no fading.And the linear wear rate of the C/SiC modified with graphite was lower than that of the C/SiC unmodified.
基金Project 2006HZ0002-2 supported by the Special Topic Fund of Key Science and Technology of Fujian Province
文摘The discrete element method(DEM) has been widely used to simulate microscopic interactions between particles.Screening is a deeply complicated process when considering the law of motion for the particles,themselves.In this paper,a numerical model for the study of a particle screening process using the DEM is presented.Special attention was paid to the modeling of a vibrating screen that allows particles to pass through,or to rebound,when approaching the screen surface.Inferences concerning screen length and vibrating frequency as they relate to screening efficiency were studied.The conclusions were:three-dimensional simulation of screening efficiency along the screen length follows an exponential distribution;when the sieve vibrates over a certain frequency range the screening efficiency is stable;and,higher vibration frequencies can improve the handling capacity of the screening machine.
基金Supported by the National Natural Science Foundation of China (50736002,61072005)Changjiang Scholars and Innovative Team Development Plan (IRT0957)
文摘Three-dimensional tracking of submicron particles in flows in a micro-channel was carried out using in-line holographic microscopy.A fixed single 0.5 μm fluorescent particle was identified and isolated from dust particles or overlapped particle pair using the laser induced fluorescent(LIF) method.Then in-line microscopic holograms of the fixed single particle were obtained at different positions on the optical axis,i.e.the defocus distances.The holograms of the single particle were used as the model templates with the known defocus distances.The particles in the in-line microscopic holograms of flow in the microchannel were then identified and located to obtain their two-dimensional positions.The defocus distances of those particles were determined by matching each hologram pattern to one of the model templates obtained in the single particle test.Finally the three-dimensional position and velocity of each particle were obtained.
