Double Masses Vibration Mill Dynamics Modeling And Parameter Optimization On Ultrafine Comminution

The operation principle of vibration mill is that the grinding media in the barrel produce impact, friction and shear to materials. Thevibration motor is used to replace excitation machine of eccentric vibration mill and its position deviates from the body center, which makes the body produce an elliptic motion and strengths the friction and impact. As a complex vibration system with rigid body and discrete elements, dynamic response and media motion status of vibration mill are always hot and also difficult points. It is often inefficient and hard to understand if the conventional theoretical methods are used to model. Furthermore it is hard to choose the excitation parameters, and there would be problems about particle refinement and agglomeration.Therefore the efficient analysis of system’s dynamic response and the reasonable modeling of grinding media are the key and basic factors for realizing the parameter optimization and ultrafine powder. At the same time there are the main research contents in the present dissertation. Dynamics modeling and parameter optimization of the double masses vibration mill are researched while using the methods of simulation and experiment, which can be summarized as follows:Firstly,dynamic equations with 6 freedoms based on Lagrange equation are established. Then the dynamic response of double mass vibration grinding is obtained using numerical analysis method and the model is proved to be effective by vibration test. Besides, the relationships between dynamic characters of vibration mill and radius of gyration as well as rotation speed are studied with the help of established model. And it is shown that the vibration intensity would increase while the rotation speed gets fast or radius increases, but the amplitude of vibration would shrink while rotation speed increases.Secondly, the model of grinding media in the barrel of vibration mill is established with the help of DEM. And testing the validity of model is done. Besides, the optimum filling rate and size of media are researched while using the parameters about displacement, speed, force and energy which are gained in simulation.Again, considering the limit of particle refinement and agglomeration in processing, the crushing mechanism of vibration mill is further researched. And the relationships between grinding and vibration amplitude as well as vibration frequency are studied based on the established discrete element model. It is discovered that increasing amplitude could improve efficiency of grinding apparently, but increasing frequency could only improve efficiency to a certain extent. On the basis of these conclusions, the weaknesses are researched when vibration mill works under the certain excitation frequency. Then the optimization scheme about changing excitation frequency is proposed. And the frequency range is determined by modal analysis, including the way of changing.Finally, the engineering application study on ultrafine comminution of vibration mill under changing rotationspeed is carried out on a small laboratory prototype. The results of powder testing prove that the method of changing excitation frequency used on vibration mill is feasible. Besides, valuable experience for field application is accumulated.