Research On The Dynamic Features Of The Critical Structures On The Road-header Based On Vibration Measurements Undergroud

Road-header,or called as Tunnel-Boring Machines(TBM)in some area,is a kind of large mechanical equipment that take charge of several functions such as cutting,loading,transportation,travel,spraying,dusting and so on in comprehensive tunneling undergraound in coal industry.Its work performance and effeciancy highly affects the coal mining production.On the other hand,usually the working condition underground for coal mining is tough and complicated;leading to the complex load on the road-header which makes the machine vibrates intensely.Therefore,it is often happened that some critical components of the road-header damaged unpredictably,and which impacted the tunneling speed and brings huge economic losses.According to the observation underground in coal mining tunnel,the intense vibration of the machine has a destructive impact on the machine.The vibration may result to the damage of the rotary table,the oil cylinder and other components frequently,which decreases the effeciancy of the whole tunneling job and increases the costs.Consequently,the research on the dynamic features of the critical structures on the road-header is necessary and valuable;it is of great significance to improve the efficiency of the machine,as well as to improve the stability of the whole machine.This thesis focuses on the dynamic features of the critical components on the machine,such as the cutting arm and the rotary table.Different methods were used and different aspects of the topic were considered.Specifically,Finite Element Modeling(FEM)was used to analysis the force conditions of different components during work,as well as the vibration modal;Experimental Model Analysis(EMA)was used to analysis the vibration modal of the cutting arm and the rotary table;the vibration test of different parts of the road-header was carried out when it was working underground,the acquired vibration data were studied in steps to discover the dynamic characters of the machine.All the forementioned works involved in this thesis are as following:(1)The 3-D models of the cutting arm and rotary table of the EBZ160 road-header were created respectively and then reasonalbly assembled together.The load calculated based on the real measured state variables of the machine during tunneling was used on the model,in order to carry out the stress analysis and dynamic simulation of those critical components.The 3-D models of the cutting arm and rotary table of the EBZ160 road-header were created respectively and then reasonalbly assembled together using Pro/E,followed by assembly calculation,interference inspection(including both static and motion interference).In the Finite Element Modeling(FEM)and modal analysis,the sub-components of the cutting arm were treated as flexible bodies in the simulation and created the cutting arm as a coupled vibration model.The load was added onto the head of the model of cutting arm therefore to launch to vibration simulation.The used load was obtained by calculation which carried out by our group members based on previous local measurements of the state variables of the tunneling machine.The simulation results presented the main vibration modals of the cutting arm and their participations in the vibration.The vibration response power spectrum and frequency response analysis were also carried out.For the rotary table of the EBZ160 road-header,the static analysis was conducted,and the locations on the rotary table that endure largest stess were pointed out,followed by strength verification.The top sixth-order modal frequencies and corresponding vibration modal were obtained by modal analysis.(2)The Experimental Model Analysis(EMA)of the cutting arm and rotary table from the EBZ160 road-header were designed and complished.The preparence of the Experimental Model Analysis(EMA)before real experiment is significant.It includes the selection of test equipments and methods,the construction of the test system and debugging,the setting of the test points for adding stimulations or responses,chosing the suitable stimulation form,and acquirance of the stimulation and response data,and so on.The acquired data were loaded into DASP,with which the model of the structure was built using the coordinates of the test points.According to the requirements of the modal test method MIMO,the stimulation and response data are needed for correlational analysis.Different modal identification algorithms were used in DASP for obtaining the top several modal frequencies and cooresponding vibration modes.The comparison betweent the modal indentifications from FEM and from EMA replies that for the rotary table,there are differences but there also exist identical vibration modes from both.For the cutting arm,there differences in between are obvioursely,the possible reason behind lies on two aspects.Firstly,the constraints condition in FEM for the cutting arm is different from the supporting way that used in the EMA;Secondly,the cutting arm is composed by several sub-components,while in EMA,it was treated as a whole body,which is quite different in FEM.How to execute physical parameters correction in FEM for the cutting arem according to the test results based on EMA is a topic that needs further investigation in this paper.(3)Implemented the local vibration test of the working road-head and the followed data proceesing and analysis.The working conditions in the comprehensive tunneling are complex and tough,the used local measurement equipments are required to be electric explosion-proof,which usually makes the related measurements underground more difficult.In this thesis,a set of electric explosion-proof vibration signal acquirsition that developed by our research group was applied.The measured vibration signals were firstly proceesed to analysis the vibration strength on the different components on the machine when the machine was doing different cutting jobs.Besides,dimensionless parameter of the vibration signals were considered to reflects the variability of the vibrations.Those basical signal analyses are useful and necessary for the machine,for example to discover possible mechanical faults at the initial stage.(4)Frequnecy domain and Time-Frequency domain analysis were both implemented through out the acquired vibration signals to figure out the vibration sourses and other characteristic frequencies that contained in the signal.From the Frequnecy domain analysis,it was found out that most of the vibration compoments are resulted by the running of the reducer.For example,the main frequnencies emaged in the vibration include: the fundamental and 2~6 times of the rotate frequency of the first-order mesh gears in the reducer;the fundamental and 2~5 times of the rotate frequency of the second-order mesh gears in the reducer.From the Time-Frequnecy domain analysis,it is shown that there exit other dominant frequencies beyond the working frequencies of the reducer as the vibration varies as time goes.Such as 629.8Hz,767.3Hz emaged at different moments along the vibration signals from the cutting arm;or the frequencies values 573Hz~577Hz,773.6Hz emaged at different moments along the vibration signals from the rotary table.Those mentioned dominant frequencies could be considered as the responds against certain load during tunneling and are valuable in the study on the load spectrum,as well as working modal identification.(5)Pilotly impleted the vibration signals in the operational modal identification of the cutting arm.The modal analysis only based on response signals is how the operational modal identification works.It is commonly used for huge and comlex structures that stimulation signals are difficult to creat or to obtain.As it is introduced before,this kind of analysis only takes the response signals for proceesing,which,is just the situation in this thesis that only the vibration signals were acquired in the experiment.Therefore,for excavating more information from the obtained vibration signals,this thesis attempted to identify vibration modals of the cutting arm following the theoretical guidance of typical proceesing used in operational modal identification works,such as the STD method.The results showed that this procedure is feasible for complex structure like the road-header.It is worth to try other typical procees such as the ARMA,the SSI as well as other popular signal proceesing methods like the HHT or EDA in the operational modal identification for the road-header.