Dynamic Characteristics And Vibration Compaction Mechanism Of The Single And Double Frequencies Mechanical System Driven By Four Vibrators

For vibrator self-synchronization theory,most of previous work has focused on the study of self-synchronous vibration systems driven by single frequency,lacking the analysis of the effects of external load characteristics(e.g.material particle flow effects)on the single frequency and dual frequency mechanical systems.In addition,as a representative of the new type of building industrialization,prefabricated buildings have been vigorously promoted throughout the country under the impetus of China’s "the Belt and Road Initiative" and "the 14th five-year plan".But so far,there are still many defects in the production of precast concrete components as the main material of prefabricated buildings,such as uneven compaction,long forming cycles,etc.The main reason of this is the lack of in-depth study on the dynamic system characteristics and compaction mechanism of prefabricated component manufacturing equipment.Therefore,to improve the compaction quality and efficiency of prefabricated components and to promote the development of large-scale compacting equipment,In this paper,considering the particle flow effect of external load,combing the four-vibrator driving vibration system with the compaction mechanism,the research topic of "Dynamic Characteristics and Vibration Compaction Mechanism of the Single and Double Frequencies Mechanical System Driven by Four Vibrators" is proposed,based on the study of the synchronous stability of the system vibration,etc.,the study of the dense mechanism is carried out.The details are as follows:(1)Under the condition of single and dual frequency,considering concrete particle flow effect,a nonlinear dynamical model driven by four reversed rotating vibrators,is established to study the synchronous stability,dynamic characteristics and the vibrating compaction mechanism of the corresponding system.Based on the averaging method,the Hamilton principle,the asymptotic method and the Routh criterion,the theoretical criterions of synchronization and stability of the system under the condition of single and dual frequency,are obtained respectively.Follow the rule of differential element method,the compaction mechanism of concrete particle flow is discussed and studied.In response to the aforementioned theoretical results,the influence of key parameters on the dynamics and kinematic properties of the system is analysed numerically and qualitatively,and then the system is verified by quantitative simulation using the Runge-Kutta methods.On the basis of the above theoretical numerical studies,the discrete element analysis of concrete compaction results is carried out by using EDEM to reveal the state changes of the concrete particle flow during the vibratory compaction process under the conditions of single frequency and double frequency.Finally,the results of the study under single-frequency and dual-frequency conditions are compared to conclude the best system parameter matching rules that are conducive to concrete densification(2)A nonlinear dynamical model of two rigid frames with limit devices driven by four reversed rotating vibrators are proposed to explore the vibration synchronization theory,dynamic characteristics and compaction mechanism.Firstly,the stiffness of gap rubber spring is disposed to equivalent linearization by using the asymptotic method.Then,the synchronization criterion and the stability criterion for system is obtained by the average method and Hamilton principle,and the vibration compaction mechanism of concrete particle flow is established analytically based on the differential element method.In aspect of numerical value,the numerical qualitative analysis on the above theory is carried out.Then,based on the method of Runge-Kutta and discrete element,the vibration quantitative simulation verification and the discrete element simulation analysis are proceed.At the same time,this chapter provides a vector expression for the motion of the concrete particle flow,and introduces the concept of mixing uniformity.While the state of motion of the concrete particles during vibration and the degree of mixing is researched,and the ideal working area and conditions for this vibrating system is determined.(3)Likewise,considering the nonlinear effect caused by concrete particle flow,the model of dynamic of three rigid frames separate driven by four vibrators is taken as the research obj ect,and the synchronous stability and compaction mechanism of the system are studied theoretically,numerically and simulatively.Compared with the previous research,the separate drivenmethod is used in vibrator is adopted in this chapter.In theory,two theoretical conditions satisfying the synchronous and stable operation of the system are deduced,and then,the compaction mechanism of concrete particle flow is analyzed theoretically on the premise that the system could realize the vertical linear movement.Finally,the above theories are qualitatively analyzed and verified by simulation,and the optimal parameter matching region of the system for better concrete compaction are derived.In the end,a summary of the work done in this paper is presented,together with an indication of the problems that still need to be investigated in the future.