Research On Dynamic Analysis Of Coal Plow And Influence On Reliability Of Plow Chain

Coal resource is abundant in China. But thin coal seam mining has not been realized mechanization, workload of workers is large and rate of resources recovery is low. Coal plow is the coal mining machinery for thin and medium seams. Coal plow is developed by the way of high power, high plow body velocity, high strength and automatization. With the development of the coal plow dynamic problem is more obvious during the working of the coal plow and its influences on the reliability of plow chain need research and discussion imminently and deeply. It provides theoretical foundation for coal plow running and improvement of the reliability of plow chain, and it is important to accelerate the development of coal plow in China. Therefore, in this paper, dynamic problem of coal plow and reliability of plow chain under dynamic load are studied deeply and systemically with theoretical analysis, numerical simulation and experimental methods. Research works include:1. According to actual working conditions of the coal plow, and considering the factors of forces of coal, pretension force of plow chain and sprocket polygon effect, nonlinear dynamic model of the coal plow is presented. Single-degree-of-freedom (single-DOF) dynamic model is presented for primary study and simple analysis of the coal plow. Then, multi-degree-of-freedom (multi-DOF) dynamic model considering various factors is presented for detailed research and analysis of various dynamic problems of the coal plow, and difference between single drive and double drive is considered.2. Nonlinear dynamic equation of coal plow is solved and simulated. Under the particular conditions, single-DOF dynamic equation can be simplified. Methods of multiple scales and equivalent linearization are used to obtain approximate analytical solution of the single-DOF nonlinear dynamic equations under determinate and stochastic forces of coal separately. Considering various factors, numerical method is used to solve and simulate single-DOF and multi-DOF dynamic equations under determinate and stochastic forces of coal separately.Simulation results show that influences of forces of coal and pretension force of plow chain are obvious on plow body velocity and chain tension, influence of sprocket polygon effect is less. And stochastic forces of coal reduce the influence of sprocket polygon effect. When double drive is used, mean value of tension in the plow chain is less than single drive, and then load of chain is reduced. Comparing single-DOF dynamic model with multi-DOF dynamic model, it shows that single-DOF dynamic model can be as reference for simple analysis of coal plow, but multi-DOF dynamic model accords with actual working conditions more.3. Factors which have effect on reliability of plow chain are analyzed, and fatigue failure is one of the important factors. Stochastic forces of coal, pretension force of plow chain and sprocket polygon effect make plow chain under high dynamic stress. Rain flow counting method and linear Miner fatigue cumulative damage model are used to predict fatigue life of plow chain. Through simulation, fatigue life of plow chain can be got under different stochastic forces of coal, different pretension forces of plow chain and different number of sprocket teeth. The simulation results show that stochastic forces of coal and pretension force of plow chain have obvious effects on fatigue life of plow chain, but influence of sprocket polygon effect is less. It provides theoretical references for coal plow running and chain maintenance. Measures to improve reliability of plow chain are presented. 4. A self-developed coal plow test-bed is used to test tension in the plow chain. Changes of chain tension are obtained under different cutting depths. Compared with simulation results of multi-DOF dynamic model under stochastic forces of coal, simulation curves are in accord with testing curves basically. Analyzing testing data of chain tension, fatigue cumulative damage change of the plow chain is got under different cutting depths, and it accords with fatigue cumulative damage change of plow chain by simulating dynamic model. It provides references for reliability analysis of plow chain.