Study On Dynamic Characteristics And Structural Optimization Of Double-layer Linear Vibrating Flip-flow Screen

At present,coal still plays a dominant role in China’s energy reserves,types of energy,and composition of energy consumption structure.It is related to national energy security and is the lifeline of the national economy.In the context of the national strategy of "carbon peaking" and "carbon neutrality",the clean and efficient use of coal has a higher standard.Flip-flow screen is widely used in the classification,dehydration,and desliming processes of raw coal due to its high screening efficiency and non clogging.However,under multiple loads such as excitation force,inertia force,and material impact force,the flip-flow screen is prone to failure behaviors such as poor stability of the screen frame and cracking of the side plate.The traditional static design method is difficult to meet the increasing performance requirements of the flip-flow screen.In response to these issues,this thesis adopts a combination of mechanical dynamics theory and finite element analysis to conduct parameter calculation,finite element simulation,and structural optimization research on the double-layer linear vibrating flip-flow screen.The main research work is as follows:Firstly,the working principle and structural composition of the double-layer linear vibrating flip-flow screen are introduced,and the working parameters of the flip-flow screen are selected and calculated according to the screening requirements;Based on the concentrated mass method,a mechanical model of the flip-flow screen is established.The vibration differential equation is constructed using Newton’s second law and numerically solved to obtain the spring stiffness,third-order natural frequency,and amplitude frequency characteristic curve.The rationality of the working parameters of the flip-flow screen is verified;Numerical simulation was conducted on the vibration system of the flip-flow screen using Simulink to obtain the time-domain characteristic curve of the flip-flow screen and verify that the amplitude of the flip-flow screen meets the working requirements.Considering the weakening effect of bolts on the stiffness of the flip-flow screen,a simplified modeling method for the bolt joint is introduced into the finite element analysis of the flip-flow screen.A finite element model of the double-layer linear vibrating flip-flow screen is established and Modal analysis is conducted to obtain the fourteenth order vibration mode and natural frequency,verifying that the flip-flow screen will not resonate;By analyzing the Harmonic Response,the deformation and stress distribution of the flip-flow screen and key components were obtained,verifying that the screen structure meets the strength requirements.Based on the mathematical expression of thread geometry,a simplified finite element model of the excitation beam and side plate bolt connection structure is established using node editing method;Perform vibration finite element simulation on the excitation beam bolts under lateral harmonic loads,analyze the stress,strain,residual preload,slip curve,and contact stress of the bolts,and verify that the bolts can meet the working requirements;In view of the loosening problem of the bolts of the excitation beam,the Control variates is used to discuss the loosening law of the bolts of the excitation beam under different initial preload,vibration amplitude,friction coefficient and vibration frequency.Based on the theory of structural optimization design and combined with the usage of the flip-flow screen,an optimization mathematical model is established with the weight of the flip-flow screen,the stress of the side plate and the stiffening beam as the objective functions;On the basis of the modal and statics simulation of the flip-flow screen,taking the section size of the side plate and beam and the position size of the stiffening beam as the design variables,the central combination design method is adopted for the experimental design,and the response surface is obtained by quadratic polynomial fitting;Perform local sensitivity analysis and response surface analysis on the output variables to obtain the response relationship between the design variables and the objective function;Using multi-objective genetic algorithm for response surface optimization solution,the weight of the flip-flow screen was reduced by 6.10%,and the stress of the side plate and stiffening beam was reduced by 26.49% and 33.31%,respectively,after optimization,achieving the expected optimization goals well.There are 100 figures,15 tables,and 120 references in this thesis.