| Scraper conveyor is the key equipment of underground fully mechanized mining face.As an indispensable coal bearing component of scraper conveyor,the service life and reliability of middle trough are related to the production efficiency and economic benefits of the whole enterprise.In recent years,with the popularization of mechanized mining,more scraper conveyors has been widely used.The service life and reliability of the middle trough have become more and more prominent.The multi-body impact and friction of the middle trough are the main reasons for the failure of the middle trough.Therefore,it is of great significance to study the multi-body impact and friction characteristics of the middle trough.In this paper,the impact and friction effects of coal,scraper and scraper chain on the middle trough are studied in detail by combining theory,simulation and experiment,which provide some guidance for the study of material strengthening and wear-resistant treatment methods of the middle trough of scraper conveyor.In this paper,based on the particle characteristics and wear theory,the friction pair of the middle groove is taking as the research object.From the point of view of theoretical calculation,the following are analyzed: the impact and wear characteristics of coal to the middle groove during coal drop,the friction and wear characteristics of coal to the middle groove during transportation,the factors affecting the wear of the middle groove under two working conditions are obtained.Then,based on bulk mechanics,the cross-sectional distribution characteristics of coal particles in the middle trough are analyzed.Based on this,the running resistance of coal,scraper and scraper chain caused by friction is calculated.In order to further study the impact and friction effects of coal on the middle trough,EDEM discrete element simulation software was used to establish the friction pair model of the middle trough and irregular coal particles.Through the analysis of the normal and tangential accumulative contact energy of the middle trough,it is found that the impact wear of coal on the middle trough mainly occurs in the middle trough of the falling coal area,while the friction and wear caused by the tangential slip of coal are all over the falling coal area and the transportation area.Using the method of controlling variables,the force and wear characteristics of the middle trough in the falling coal area and the transportation area under different chain speeds,different mining heights and different coal particle shapes are studied respectively,and the relevant conclusions about the influence of different working conditions on the wear characteristics of the middle trough are obtained.Through the joint simulation of EDEM-Ansys,it is concluded that the maximum deformation of the middle trough in the falling coal area and the transportation area occurs on the top and middle of the trough.In the middle part of the plate,the maximum stress occurs at the joint between the groove and the plate.In order to study the impact and friction effects of scraper and scraper chain on the middle groove,a data testing system for the middle groove was built.The impact loads of scraper and scraper chain on the middle groove were measured at different chain speeds under no-load condition.It is concluded that the impact load of the scraper and scraper chain on the middle groove changes periodically under the characteristics of step function,and the impact load at the side chain of the coal mining in the middle groove is relatively large.In order to further study the friction and wear effects of scraper and scraper chain on the middle trough,the micro-wear tests were carried out to simulate the friction and wear of the middle groove.The variation laws of friction coefficient and wear rate of four kinds of middle trough materials under different sliding velocities and loads were analyzed.It is found that the wear rates of the other three materials except weartuf 450 increase with the increase of load,while the wear rates of the four materials decrease with the increase of sliding speed. |
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