Effect of Milling Parameters on DEM Modeling of a Planetary Ball Mill

The effects of the milling parameters involving shape of powder particles, rotation speed, and ball-to-powder diameter (BPDR) on DEM modeling in the planetary ball mill were investigated. BPDR was varied from 1 to 10. The results revealed that the size and shape of the powder particles do not give a significant change in simulation results when BPDR attains maximum value of 10. The increasing of BPDR leads to the increase of simulation time and size. Hence, the effect of change of the powder particle shape on the calculated data size is not significant. The results also revealed that the increasing rotation speed increases impact energy between powder particles.

Discrete Element Simulation of Asphalt Pavement Milling Process to Improve theUtilization of Milled Old Mixture

In order to improve the utilization of milling materials,save stone resources and reduce milling energy consumption,the aged Styrene-butadiene-styrene(SBS)modified asphalt was used as a binder to prepare AC-16 asphalt mixture to simulate old asphalt pavement materials.First,the test and discrete element simulation results of uniaxial compression tests were used to calibrate the parameters of the parallel bonding contact model between asphalt mortar and aggregates.On this basis,a microscopic model of the asphalt mixture was established to simulate the old asphalt pavement.Then,the discrete element software PFC(Particle Flow Code)was used to simulate the milling process of the old asphalt pavement.Analyzed the force of the cutting tool and the utilization rate of milling materials,and the optimal milling speed and milling depth were determined.Finally,the energy consumption in the milling process was measured.It is concluded that in the process of milling the old asphalt pavement,using a cutting angle of 42°,milling speed of 0.5 m/s and milling depth of 20 mm can reduce the wear of the cutting tool.In this case,the direct utilization rate of milling materials is 85.3%,and the rate of energy consumption reduction is 33.53%.After parameter optimization,the utilization rate of milling materials can be increased by 17.4%.

Experiment and finite element analysis of micromilling force

For predicting the milling force in process of micromilling aluminum alloy, the law for micromilling force changing under different milling parameters was studied. The elastic-plastic finite elelent model of micromilling was found using general commercial software. During modeling, the Johnson-Cook＇ s coupled thermal- mechanical model was used as workpieee material model, the Johnson-Cook＇ s shear failure principle was adopted as workpiece failure principle, and the coupled thermal-mechanical hexahedron strain hybrid modules and serf-adaptive grid technology based on the updated Lagrange formulation were used to mesh the workpiece＇ s elements, while the friction between tool and workpiece obeys the modified Coulomb＇ s law that combines with the sliding friction and the adhesive friction. By means of finite element analysis, the law for micromilling force changing under different milling parameters was obtained, and the results were analyzed and compared. Finally micromilling experiments were carried out to validate the results of simulation.

A Facile Way to Large-scale Production of Few-layered Graphene via Planetary Ball Mill

Abstract In the field of polymer/graphene nanocomposites, massive production and commercial availability of graphene are essential. Exfoliation of graphite to obtain graphene is one of the most promising ways to large-scale production at extremely low cost. In this work we illustrate a facile strategy for mass production of few-layered （≤ 10） graphene （FLG） via the newly explored ball milling. The achieved FLG concentration was determined by UV/Vis spectroscopy. The formation of FLG was proved by measuring the flake thickness by atomic force microscopy （AFM）. Further Raman spectral studies indicated that the crystal structure of exfoliated flakes was preserved satisfactorily during this shear-force dominating process. To increase the maximum concentration obtainable, it＇s critical to make a good parameter assessment. N-methylpyrrolidone （NMP） was used as a dispersing medium and the effect of milling parameters was systematically and quantitatively investigated, thus providing a criterion to optimize the milling process. We established the optimal values for solvent volume and initial weight of graphite. As for milling time, the production of FLG was enhanced with continuous milling according to the power law, but not linearly with increasing milling time. Moreover, the possible mechanism involved in milling process was also explored. Our work provides a simple method for graphite exfoliation and has great potential for improving thermal and electrical conductivity of polymer composites in the fields of engineering.