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Ball motions in a planetary ball mill with liquid media were simulated using the DEM. The distributions of ball impact energy were calculated from the simulation. Then，the cumulative value of the impact energy (E) and median of the impact energy at one collision (e1/2) were calculated. Grinding tests were examined and relationships between particle sizes and the specific impact energy multiplied by grinding time (Ewt*) were evaluated. At higher acceleration， particle sizes of ground powders decreased faster. However, from the viewpoint of the impact energy，the energy efficiency got worse. With increase of ball sizes, e1/2 increased but the number of collisions decreased. As results, using the smaller balls，particle sizes decreased faster and the energy efficiency was also better. The amount ofEwt required to obtain 0.5 pm mean diameter (Ewt*(0.5 pm)) was calculated for each test condition. The fitting curve was applied for the relation of Ewt*(0.5vs e1/2. [ABSTRACT FROM AUTHOR]

A new method to determine both the coefficients of particle and rolling friction in distinct element method (DEM) was proposed. The coefficients are two of the most important parameters which have great effect on particle behavior in DEM. However, it is difficult to determine the values of the coefficients, which is applicable to multiple behaviors, from an experiment. We proposed the method to determine the two coefficients uniquely so that two indicators correspond to experimental results. As the indicators of static and dynamic behaviors, the angle of repose and the discharge flow rate were adopted, respectively. The values of the coefficients which can represent both static and dynamic behaviors of particles were determined by means of the method. The particle behavior in a rotating drum at three different rotational speed was simulated by using the determined coefficients in order to verify the applicability of them to dynamic behavior of particles under various conditions. The simulated behaviors for spherical particles corresponded to the experimental ones. The determined coefficients by means of the proposed method could be applied to the behavior of spherical particles at all of the rotational speeds. On the other hand, the simulated behaviors for irregularly shaped particles did not correspond to the experimental ones, in particular at higher rotational speed. It would be because the rolling friction of irregularly shaped particles depends on the particle velocity in a rotating drum. [ABSTRACT FROM AUTHOR]

Ball motions in wet ball milling with a tumbling ball mill were simulated using the discrete element method (DEM). Results of DEM simulation were compared with the results of ball motions and real grinding tests in wet ball milling. In observation of wet ball milling phenomena, ball media slipped in pure water remarkably, but ball motions were clearly activated by the addition of low content of fine particles. In DEM simulation, calculated ball motions were adjusted to observed motions with change of friction coefficient. Then, impact energy of ball media was calculated as a key factor of grinding. Results of grinding tests of wet ball milling were well related to the impact energy. At the grinding tests with various rotation speed, all plots of particle size (d50) of ground product vs cumulative impact energy agreed to just one curve. [ABSTRACT FROM AUTHOR]

A new simulation model to deal with metal powders was developed. The feature of the proposed model is to express plastic deformation behavior of metal powders. The model is based on Advanced Distinct Element Method (ADEM), which can represent deformation behaviors of elastic materials. The change of the proposed model from ADEM is interaction force of primary particles. In order to confirm the validity of the new model, compression tests and drop tests have been carried out in experiment and simulation. In compression tests, test tablets were thinly stretched and the deformation was maintained. In drop tests, a dimple was formed on the tablet when an iron ball collides. Characteristic behaviors of metal material such as stretching the tablets and forming a dimple were also confirmed in simulation. Therefore, it is identified that the proposed model could express the behavior of metal material. [ABSTRACT FROM AUTHOR]

A new model for estimating macroscopic permittivity was proposed to predict dispersion states of filler particles in a particulate composite material. In the model, the estimation targets are random packed composite materials. The composite materials were represented as a cluster of unit cells. The unit cells were connected by a proposed layer structure model. The macroscopic permittivity was estimated by calculating a synthetic capacity of the cluster. The proposed model was validated by comparisons between estimated and measured macroscopic permittivity of several particulate composite materials. In addition, it was identified that the proposed model could estimate the permittivity more accuracy than an existing theoretical equation's one due to considering the effects for the dispersion states of filler particles. Furthermore, it was indicated that the proposed model could also estimate the dispersion states of filler particles by the measured permittivity. The applicability of the method was confirmed by comparisons between estimated and experimental dispersion states of filler particles. [ABSTRACT FROM AUTHOR]

A new simulation approach using Advanced Distinct Element Method (ADEM) was proposed to predict the compression behavior and the characteristic of the compact. Relationship between compression load and compressive strength of compact have been analyzed. The breakage behavior and discrete motion of particles during compression was simulated by ADEM. ADEM parameters represent the property of samples, it was determined to fit the experimental results of load-displacement curve obtained by single particle compression test. Internal structure of compact was measured by X-ray CT imaging, information of particle breakage and density distribution was obtained. High density compact could make as a result of high compression load, on the other hand, compressive strength of compact decrease when the compression load was much high. There was optimum condition to obtain the tough compact. Simulation analysis could visualize the compression behavior of compact, fine powder ratio suggest the optimum compression load for powder compact. [ABSTRACT FROM AUTHOR]