Study On The Dynamic Characteristic And Experiments Of Permanent Deformation Failure Of Mining Vibrating Screen Springs

Coal is China's principal energy,and coal washing and processing is an effective way to reduce the impurity content in coal,to improve utilization ratio.Mining vibrating screen is one of the key equipment in the coal washing and processing,which is widely used in coal classification,dewatering,medium-removal,desliming,etc.Spring is the key component of mining vibrating screen,which directly affects mining vibrating screen working performance.The spring stiffness will change when the spring permanent deformation failure occur,which causes structural damage and depress the screening efficiency of the mining vibrating screen.It is an urgent problem to diagnose the spring permanent deformation failure.Therefore,the spring permanent deformation failure is the study object in this paper,the influence rules of the spring stiffness change for mining vibrating screen vibration characteristics caused by permanent deformation failure are studied,the failure feature information are researched,in order to provide the theory basis for permanent deformation failure diagnosis.The main achievements and research conclusions obtained in this paper are summarized as follows:The dynamic characteristics of the plane motion of the mine vibrating screen are studied.?1?The dynamics model of mining vibrating screen for planar motion is built based on the dynamics theories of the rigid mechanical system,and the vibration differential equation is established based on the D'Alember principle to reveal the relations of the mine vibrating body and the eccentric block mass,spring stiffness,excitation force and amplitude.The dynamics analysis is made on the dynamics model of mining vibrating screen for planar motion and the three working states of the mining vibrating screen are obtained,the results show that the ultra-resonance stage is suitable for the mining vibrating screen to proceed long-term and stable screening operation.However,the spring may occur permanent deformation failure after a long time alternating load,resulting in the spring stiffness change,and the motion of the mining vibrating screen is transformed from planar motion into complex spatial motion,and the excitation force cannot guarantee that its line of action goes through the center of mass of the screen body in most cases,under such circumstance,the dynamics model of mining vibrating screen for planar motion is no longer applicable.?2?The dynamic characteristics of the spatial motion of the mine vibrating screen are studied.The dynamics model of mining vibrating screen for spatial motion is built based on the dynamics theories of the rigid mechanical system,and the vibration differential equation is established in the method of Lagrange.The numerical simulations are carried out on the mass center of the rigid body vibration based on Newmark-?algorithm,respectively to get ideal state and spring permanent deformation failure state curves of the mass center of vibration,the results show that the proposed mining vibrating screen spatial motion can fully represent the relationship among the dynamics parameters in the process of system dynamics model vibration.The spring stiffness variation coefficient and amplitude variation coefficient are proposed,and six kind of spring failure are selected,different kinds of spring failure mining vibrating screen space motion dynamics model are established for the simulation analysis,the simulation results show that the amplitude change law of all spring site in x,y,z direction can effectively reflect the spring permanent deformation failure,thus the theoretical basis to diagnose mining vibrating screen spring permanent deformation failure is established.However,the mining vibrating screen is a large mechanical structure which made from thin plates and beams combination,the space motion will lead to local structural deformation,therefore,the finite element method is adopted to model and analyze mining vibrating screen.The finite element method is used to model and analyze mining mine vibration screen.?1?The mining vibrating screen three-dimensional model is built in ANSYS,the shell elements and beam elements are used to build the main structure,the degrees of freedom coupling and constraint adding are used to simulate bolt for structure assembling,the spring elements are used to the simulate spring groups,the Point Mass is used to simulate the exciter mass for adding harmonic load.?2?Statics analyses are carried out,the structural displacement and stress distribution in stop condition are obtained,remove the spring seat displacement is equivalent to the amount of spring compression,the results show that the whole structure stress is less than the structural material's allowable stress.?3?The modal analyses are carried out,the first to twelfth order natural frequencies and their modes are obtained,the results show that the natural frequencies are less than the working frequency,and the resonance will not occur during mining mine vibration screen stable working state.?4?The harmonic response analysis are carried out,the vibration amplitudes and the dynamic stress distribution rules are obtained.The results show that the overall structure amplitudes distribution of mining vibrating screen are symmetrical.On account of the model error and local structure elastic deformation,the whole structure amplitude slightly go beyond the theoretical design scope,which still comply with the prescribed standards.The results also show that the overall dynamic stress of mining vibrating screen are symmetrical,and the maximum dynamic stress meets the standard.Therefore,the finite element model of mining vibrating screen can effectively simulate the dynamic characteristics of mining vibrating screen,providing effective model for researching the influence rules of spring permanent deformation failure on the state parameters of mining vibrating screen.The influence rules of spring permanent deformation failure on the parameters of mining vibrating screen are studied.?1?Through the static analysis,the four spring compresson amounts are obtained,and the influence rules of the single spring permanent deformation failure and spring permanent deformation failures on spring compresson amounts are studied respectively.The results show that the spring compresson amounts increase or decrease in different change rate.?2?Through the harmonic response analysis,the amplitudes of mining vibrating screen four spring seats in x,y,z diections are obtained,and the influence rules of the single spring permanent deformation failure and two spring permanent deformation failures on amplitudes are studied respectively.The results show that the spring compresson amounts increase or decrease in different change rate.The results show that the spring stiffness change has greater influences on the amplitude of the mining vibrating screen in Direction z,but fewer influences in Directions x and y.In order to meet the national standard when single single spring permanent deformation failure occur,the?35?k₁ and?35?k₃ should be less than 30%,and the ₁??₃?should be less than 29.5624 mm,as well as,the?35?k₂and?35?k₄ should be less than 10%,and the ₁?and ₃?should be less than 30.8891mm.When two single spring permanent deformation failures occur,the?35?k₁,?35?k₂,?35?k₃,?35?k₄ should be less than 10%,the?₂ should be less than 30.8891 mm when k₁,k₂ are fail,the?₂ and?₄ should be less than 28.1899 mm when k₁,k₃are fail,the ₄?should be less than 30.4278 mm when k₁,k₄ are fail,the ₂?and ₄?should be less than 30.3080 mm when k₂,k₄ are fail.According to the influence rules of spring permanent deformation failure,the basis are providesd for the diagnosis of the vibrating screen spring permanent deformation failure.The experiments of the dynamic characteristics of mining vibrating screen for the spring permanent deformation are studied.?1?In view of of jinzhuang coal group,The experiments of single spring failure and two spring failure of the straight vibrating screen SLK3661W are carried out in ChengZhuang coal mine of JinMei Group.The mining portable vibration data recorder and mining vibration sensors are used to measure the mining vibrating screen spring seat vibration acceleration data,and the acceleration data processing software for computing the vibration amplitude data are designed based on LabVIEW.?2?According to the analysis of mining vibrating screen spring seat amplitude data,the dynamics research method of mining vibrating screen spring permanent deformation is verified.The rigid model simulation data,the finite element model simulation data,and experimental measurement data were analyzed,the results show that the finite element model is more accurate and effective than the rigid model,verifing the finite element model and analysis is effective to realize mining vibrating screen spring permanent deformation failure diagnosis.