Study On The Mechanism Of Rock And Load Reconstruction Of Shearer

The research on the rock breaking mechanism of shearer picks and load characteristics of shearer is the theoretical basis of drum structure optimization design,and it is also one of the key issues in analyzing the dynamic characteristics of shearer system.Although a lot of work has been done on related research at home and abroad,the process of crushing coal by shearer drums has not been completely mastered.Therefore,in this paper,the combination of theoretical modeling,numerical simulation and experimental verification has been used to deeply study the process of elastic deformation-plastic deformation-breaking of coal under the action of picks,and the pick load reconstruction has been performed.The main research contents of the paper are as follows:Aiming at the problem that the elastic-plastic-brittle physical characteristics of coal has not been involved in the existing coal cutting models of shearer picks,based on elasticity,plasticity,and fracture mechanics,during the elastic deformation stage,the shape of the shearer picks is appropriately simplified and is viewed as rigid bodies,the coal is regarded as an infinite half-space elastic body,then the calculation formula of the cutting force of the shearer picks and the formula of the stress and displacement of the coal are obtained when the shearer picks interact with the coal wall;during the plastic deformation stage,by applying generalized Mises yield conditions and considering the cohesion and internal friction force of coal body material that are unique and different from that of metal materials,the pick cutting mechanics model is constructed in the process of the coal body undergoing plastic deformation during interaction between the shearer picks and the coal body;during the brittle fracture stage,according to the form of the crack,the expressions of the stress and displacement around the fracture are obtained by means of the complex variable method;the stress cloud diagrams of the fracture area are formulated according to the formula,and the 3 cutting load models of shearer picks corresponding to 3 states are constructed by considering the influence of the cutting angle of shearer pick,the models are validated by experiments,which reveal the coal cutting mechanism of shearer picks under the influence of the elastic-plastic-brittle physical properties.According to the structural characteristics of the shearer drum and the characteristics of the cutting process,the influencing factors affecting the drum cutting load are analyzed.Using the geometry and mechanical system kinematics theory,the kinematics models of shearer picks under four conditions of normal,end slope,special,oblique cutting feeding are established,the three-direction trajectory of pick is obtained;combining the cutting mechanism model,and taking the arrangement of picks,drum speed,shearer traction speed into consideration,the mechanical model of drum-cutting coal is constructed;the numerical solution route for the drum load was designed,the time history curve of the drum load was obtained,the influence law of the hardness of the coal rock,the walking traction speed,and the drum speed to drum load characteristics were studied by using mathematical statistics;the results show that the average value and peak value of the three-direction force of the drum increase with the increasing of the traction speed,and the influence of the traction speed on the fluctuation coefficient of the cutting resistance and traction resistance is small,but the influence to the fluctuation coefficient of lateral resistance is greater;the influence of the sequential arrangement of picks to the average and peak value of the three-direction force of the drum is biggest,the hybrid pick arrangement smaller,the chessboard arrangement smallest;the influence of the hybrid arrangement of picks to the fluctuation coefficient is biggest,the chessboard arrangement smaller,the sequence pick arrangement smallest;the average value and the peak value of the drum three-direction forces decrease with the increasing of the rotation speed of the drum,and the fluctuation coefficient increases with the rotation speed of the drum.Based on the 1:1 simulating coal mining underground fully mechanized equipment experimental platform,the three-direction load sensor of pick was designed,the pick load test under the normal,oblique cutting and end slope cutting conditions of shearer was completed.Aiming at the problem of a large amount of noise in the experimental data,a signal de-noising method based on improved wavelet threshold was proposed to remove the interference noise signal and retain the mutation information in the original signal.The more realistic cutting load of drum under three working conditions was obtained and compared with the drum cutting load model,and the validity of the model is verified.The research results in this paper provide theoretical support for the rock breaking load analysis of shearers,roadheaders and similar drilling equipment,and provides theoretical support for the design and optimization of the drum,the dynamic characteristics and reliability analysis of the shearer system,and has certain engineering value and theoretical significance.