Research On Several Key Problems Of Large Suspension Inertial Vibration Machine

In this paper, a large suspension inertial vibration equipment—plansifter is as research subject. Aiming at the harmful vibrations and structural damage during plansifter operation, the key issues, such as the nonlinear elastic properties of flexible suspender, the overall dynamics of the system, the multi-field coupling transient process during the starting period and stopping period are in-depth studied and explored using nonlinear elasticity theory, AC motor transient analysis theory and numerical simulation techniques. The results can provide a theoretical basis for the dynamic analysis, reducing harmful vibrations and the design of inertial exciter of suspension inertial vibration machinery. The main contents are as follows:1. The nonlinear beam mechanics model of flexible suspender with large deformation and axial force is established. Considering the beam axis extensible, geometric nonlinearity due to large deflection and large deformation, and the force balance equation based on the large deformation configuration of beam, the nonlinear differential equations of beam with large deformation and axial force is obtained. Through numerical simulation, the laws of influence of the axial force, lateral force and the boundary conditions at the both ends of beam on the deformation of beam are analyzed, and the nonlinear elastic characteristic curve of lateral and axial deformation on the free end of the flexible suspender are obtained. The results provide a theoretical basis for dynamic modeling of suspension vibration equipment.2. The rigid-flexible coupling dynamic modeling of planifter is proposed. The relationship of geometric constraints between the deformation of four groups of suspender and the rigid body movement of sieve is analyzed, a nonlinear dynamic model of inertial vibration device is built, and the calculation of the steady-state amplitude and the low natural frequency are deduced. By using FEM, the first10modes and the displacement response are obtained from the normal mode analysis and the transient response analysis respectively. The steady state operation of sieve has been tested, the experimental results verify the theoretical analysis.3. To eliminate the resonance during starting period in plansifter, the multi-field coupling transient process with a self-adjustable inertial exciter are studied. Considering the nonlinear of lateral stiffness on the free end of the flexible suspender, transient starting of asynchronous motor and the friction of bearing, the rigid, soft and electric multi-field coupling mathematical model during starting period is established. The generation, development and decay of the starting transient resonance is analyzed based on original exciter, and the inhibition mechanism of the transient resonance is revealed. Based on in-depth analysis of the influence of each parameter of self-adjustable inertial exciter on the starting transient, a new inertial exciter with variable stiffness is invented, which not only to further reduce the maximum amplitude of the starting transient resonance, but also to reduce the sensitivity of the absorbing effect of the relevant parameters, and to improve the robust of vibration absorbing.4. The method of numerical computation is employed to design a inertial exciter whose eccentric distance is self-adjustable for eliminating resonance in square plansifter during the stopping process. Considering the mechanical characteristic of three-phase asynchronous motor and the friction of bearing, the mechanism of the stopping transient resonance is analyzed based on original exciter, and the inhibition mechanism and the influence factors of the transient resonance are revealed. The transient process of the stopping period in plansifter with a new exciter is researched. By the new exciter, the transient resonance, including starting period and stopping period, are better absorbed. The results provide a new idea for reducing transient resonance of inertial vibration machine.5. The dynamic strength and dynamic design methods of plansifter are investigated. The FEM is employed to establish structure dynamic model for obtaining dynamic response. The main reasons of structural damage are found. Furthermore, the effects of various factors on stresses of three dangerous positions are calculated and analyzed. The various measures are proposed to improve the structural strength, and these measures have been proven to be effective in co-operation projects. The structural design method with better dynamic strength in large-scale development of plansifter is analyzed.By the above studies, a set of modeling theories and dynamic design methods for large-scale development and high reliability of plansifter are formed eventually.