Study On Vibration Friction Dynamic Characteristics And Experiments Of Some Vibrating Machine Systems

As a new subject, vibration utilization engineering is closely associated with people life and production. Professor Wen Bangchun and his team did a lot of work in this field. So far, vibration utilization engineering has been a necessary mechanism in human producting and life. As an important branch of it, vibration friction is still on research or in the beginning. With the increasing requirements for engineering technology, people have realized the benefit for human life with its widely application. The practice shows that vibration can reduce friction coefficient and friction force between two objects, lighten abrasion of objects, reduce energy consumption and increase greatly working efficiency, which can create huge economical and social benefits for our country.Based on the relationship of vibration and friction, Professor Wen Bangchun proposed the new subject-’Vibration Friction Science’, which is the most worthy of studying and developing deeply. At present, there are many machines which include friction between two objects and friction within granular materials, such as vibratory roller, vibratory pile driver and vibratory conveyor. But until now, the mechanism of friction in vibration is still not fully revealed. There are not detailed and definite methods to further use the benefit brought by vibration. Therefore, it is most valued in academic and actual significance by making the best use of it.This paper is directed by the concept of vibration friction proposed by Professor Wen Bangchun. Taking the vibration friction systems that widely used in engineering as research objects, on the basis of nonlinear dynamics, granular dynamics, tribology and granule materials dynamics, the nonlinear dynamic characteristics and mechanisms of vibration friction system coupling with granules are studied by means of theory, simulations and experiments. The contents in this paper include:the vibratory law and mechanism of granular materials in vibration; nonlinear dynamic characteristics and vibration friction mechanism in the process of vibration compaction; nonlinear dynamic characteristics and vibration friction in vibratory pile-soil system. This work is supported by National Nature Science Foundation and the Fundamental Research Funds in the Central Universities for excellent PhD paper.Concrete contents are as follows:(1) As a special phenomenon, granules vibration is most value of engineering application. So far, it is not well studied in domestic and abroad because the traditional methods have not been suitable for it. In this paper, the Discrete Element Method (DEM) and granular materials program are studied to analyze the motion of granular materials in vibration. By the theories of granular dynamics and nonlinear dynamics, the discrete element model of granular materials in vibration working plane is established and the motion equation is solved. Proper analysises are given for friction between granule material and the vibration working plane and in granules.(2) By the international software for discrete element method-EDEM, the motion of granules on vibration working plane is simulated. The parameters model for granules in vibration is established. The motion law of granules is got by discrete element method. With different vibration amplitude and vibration frequency, velocity of granules is discussed. The simulation results show that the velocity curves of single granule and granular materials are different. That is the result of interation in granules. The velocity curve of granular materials is steadier than single granule when they are in the steady stage. In this paper, with the increasing of vibration frequency and amplitude, the velocity of single granule and granular materials are both improved in some extent and gradually go to their separated steady value. All of the results show that there is an optimum value of vibration parameters for granules. It is not for the biggest parameter in the range when the velocity gets the maximum value. It is also related to other factors.(3) For the study on granules vibration by high speed photography, researchers always did work on the tracks but not on the motion deeply. In this paper, a number of experiments are done by the international leading hign speed photography instrument to study the motion of granular materials on the vibration working plane. Taking single particle and granular materials as subjects, the characteristics of motion for granules and some experiment phenomenons are analyzed. The results of experiments are indentical with simulation solution, which strongly prove that the simulation is correct. Therefore, the study on granular materials in vibration by discrete element method is exactly proper. It is also showed that the study on granular materials in vibration using the hign speed photography is successful. This provides not only a new approach for granules vibration but also guides and references for vibration friction mechanism coupling with granules.(4) Combinign with granules dynamic theory, particle materials dynamics and nonlinear dynamics, from the perspective of granular dynamics and particle materials dynamics, vibration friction mechanism and the nonlinear dynamic characteristics of vibration compaction system are studied. By PFC3D-a type of3dimensions particle materials software, the model of vibration compaction system with soil is established based on the granular materials theory. The laws of void ratio and contact force chain network in soil are studied by changing different vibration amplitude and frequency. The void ratio directly reflects the effect of vibration compaction. The contact force chain network is an important idea about materials compation process which can decide mechanical characteristics by its characteristics. Therefore, it is very significant to study on them for proposing microscopic theory of vibration friction system coupling with granules. Results of the void ratio in this paper are identical with the law of contact force chain in soil, which strongly prove that the study on granules vibration by PFC3D software is successful.(5) From the view of soil dynamics and property, the stress-strain relationship in vibration pile process is analyzed. Through the interaction of pile and soil, the mechanisms of vibration friction and vibratory liquefaction are studied. According to the hysteretic characteristics of soil, the nonlinear vibration pile-soil system model is established considering friction force. The equivalent stiffness and damping coefficient are calculated. The resonance and non-resonance responses are both got by approximation method. Nonlinear dynamic characteristics of vibration-pile system are given in the simulation with different exciting force amplitude, vibration frequency and soil stiffness.