Dynamic Research And Dynamic-gradual Coupling Reliability Analysis Of The Transmission System Of A Shearer Cutting ARM

As shearer has become one of the most important equipment in the comprehensive mechanized coal mining face,its development level represents the level of the entire coal industry of China.The transmission system of a shearer cutting arm is a power transmitting component of the shearer's cutting unit,which determines whether the shearer can operate safely,reliably and efficiently or not.In order to analyze the reliability of the transmission system,the transmission system of MG300/700-WD type shearer cutting arm is taken as a research object.Then the load spectrum,dynamic characteristics,gear contact fatigue reliability and dynamic-gradual coupling reliability of the system are studied in this paper.Finally,the reliability robust optimization design of the system is finished to improve the weak parts and sensitive design parameters of the whole system.The concentrates drawn from the study can be summarized as follows:(1)To solve the load calculation problem of the cutting unit of a drum shearer under deep and dangerous mining condition,the finite element model of a small single pick cutting test bed is built in LS-DYNA software.Then the cutting process under simple mining condition is simulated in LS-DYNA software and the tool forces are obtained,which are verified by both the experiment results and the results of classical theory models.Additionally,with the consideration of the characteristics of the deep mining condition,the cutting process is simulated and tested by applying lateral pressure on the rock to simulate the high ground stress.Then the relationship between the pick's cutting force and the lateral pressure is researched.Combining the simulation results with the linear regression analysis of classical theory models,the mathematical model of a pick's cutting force under deep dangerous mining condition is built.Finally,the resultant forces and moments of a drum can be computed by the superposition of every pick's cutting force,the results of which have good coincidence with experiment results.(2)To solve the dynamic calculation problem of the transmission system of MG300/700-WD type shearer cutting arm under random load,a dynamic model of the system is built,which can take the influence of planetary gear transmission,parallel shaft spur gear transmission,transmission shaft,bearing and lumped mass of shaft sleeves and nuts into account.By solving the dynamic response of the system,the dynamical contact stresses and tooth root stresses of the gears can be obtained.The results are not only helpful for the reliability analysis and optimization design of the system,but also conducive to predict the failure of the system.(3)To focus on the gear contact fatigue reliability issue of the system,an explicit expression between the dynamical contact stress amplitude of failure gears and basic random variables of the system is obtained by using Latin hypercube sampling method and BP neural network method.According to the stress-strength interference model,the gear contact fatigue reliability of both the parallel shaft spur gear transmission subsystem and the planetary gear transmission subsystem can be calculated.Then the reliability of the entire system can be analyzed with consideration of the failures of the two subsystems being independent and dependent respectively.The results show that the dependent failure analysis of the system is more accurate when the system's reliability is high.Moreover,the results are verified by Monte Carlo method and the second order narrow reliability bonds theory.(4)Taking the transmission system of MG300/700-WD type coal shearer cutting arm as research object,the reliability problem of the system with several random parameters,which is subjected to dynamic load and gradual failure due to strength deterioration,is studied in this paper.Then the sensitive design parameters can be confirmed and optimized by the dynamic-gradual coupling reliability analysis,reliability sensitivity analysis and reliability-based robust optimization design of the system.The results are helpful to designers,manufacturers and users of coal shearers.