Dynamic analysis of vibrating flip-flow screen based on a nonlinear model of shear spring

Vibrating flip-flow screen provides an effective solution for the dry screening of wet and fine coal,and the dynamic characteristics of shear spring largely affects its dynamic response and screen performance. In order to study the amplitude and frequency dependency of shear spring equipped in vibrating flip-flow screen,a nonlinear model of shear spring is established based on a superposition of elastic force,friction force and fractional derivative force. In the proposed model,the nonlinear elastic force describes the static nonlinear elasticity of shear spring,the friction and frac- tional derivative forces predict the amplitude and frequency dependency of shear spring’s dynamic characteristics,re- spectively. Then the experimental results of dynamic test of shear spring is used to compare with the simulation results of the proposed model. The results show that when the amplitude dependency is described,the mean squared errors and mean errors of dynamic stiffness and lag angle between experimental results and the simulation of the proposed model are 0. 525 and 0. 007,and 0. 323% and 5. 58% ,respectively. When the frequency dependency is described,the mean squared errors and mean errors of dynamic stiffness and lag angle between experimental results and the simula- tion of the proposed model are 0. 041 and 0. 011,and 0. 107% and 5. 26% ,respectively. The results demonstrate that the proposed model is capable to describe the dynamic characteristics of shear spring. Furthermore,the proposed model is used in the dynamic analysis of the vibrating flip-flow screen,and the dynamic response of vibrating flip-flow screen is calculated under different parameters using Newmark algorithm. Results show that as shear spring exhibits ampli- tude-and frequency-dependent dynamic characteristics,in the system’s second resonance zone,with the increase of the shear spring’s damping,the peak value in the resonance area decreases while the resonance frequency increases,and an increase of excitation force results in the increase of the peak value in the resonance area and the decrease of reso- nance frequency. Therefore,the effect of the dynamic characteristics of shear spring on the system should be considered when the dynamic response of vibrating flip-flow screen is analyzed.