Research On Dynamics Starting Process To Belt Conveyor Based On Traveling Wave Propagation Method

Belt conveyor has become the most important bulk materials continuous conveying equipment and been widely used in metallurgy, mining, port, food and chemical industry. As a result of the conveyor dynamics load of acceleration or deceleration (starting or shutdown process), especially for large loading capacity, long distance and high velocity belt conveyor, system reliability and components of strength design are directly affected so the dynamics analysis is becoming particular importance.For a one-dimensional viscoelastic extensional vibration system of belt conveyor, dynamics equation was established and dynamics force and velocity, in dynamics operational process of belt conveyor, are respectively equivalent to force traveling wave and velocity traveling wave passed in the two opposite directions along the conveyor line based on the Wave Propagation Method. Dynamics force traveling wave and velocity traveling wave were connected with characteristic parameter wave impedance. Attenuation constant was brought in to describe the influence of running resistance related to velocity in dynamics operational process of belt conveyor and belt viscosity deformation loss. Equivalent velocity by concentrated resistance was brought in to describe the influence of running resistance not related to velocity. For a belt conveyor model with single drive at head or two drives at head and tail, traveling wave solution equations were derived. At the head or the tail, there are excitation equations of drive waves, reflection equations, and refraction equations of traveling waves. On the conveyance lines, there are reflection and attenuation equations of traveling waves. Wave propagation process in dynamics operational process of belt conveyor was described. And then, the overall wave superposition model of belt conveyor, including dynamics force waves and velocity waves, was obtained. By the discrete element method, the belt conveyor was divided into many finite structural elements and a discrete computational model solved by computer, coupled with head, tail and the conveyance lines, contained of dynamics force wave and velocity wave, was established. The computer algorithm and MATLAB simulation program was written. A belt conveyor model with single drive at head or two drives at head and tail was solved and analyzed by driving force input method or the controlling start-up velocity input method. Numerical solutions of dynamics force and velocity at any point on the conveyor belt with respect to time of transient motion process were obtained.For a belt conveyor model with single drive at head, the characteristics of wave propagation was analyzed. Through the superposition curves of tension waves and velocity waves of conveyor belt, the obtained results and change rules of belt tension and velocity, and the differences between starting time of head and tail of conveyor in starting process are coincident with the factual situation. The tension calculations values of head and tail were correspond to the results of theory calculations. For an actual belt conveyor model with single drive at head, the different situations, full load and no-load, starting with different start times, and starting with different starting controlling curves, were simulated and analyzed. For an actual belt conveyor model with two drives at head and tail, the situations of starting together or not together with starting controlling curves were simulated and analyzed. Throughout start-up dynamics process analysis with different conditions, the dynamics tension, velocity with respect to time of start-up at any point on the conveyor belt were obtained. Tension-time-displacement three-dimensional diagram of belt, the velocity-time-displacement three-dimensional diagram, tension-time, velocity-time, tension-displacement, velocity-displacement, two-dimensional diagram based on different given dynamics variables were output. The obtained results and change rules of belt tension and velocity are coincident with the factual situation and the numerical data are in good agreement with the theoretical calculation, which demonstrates the validity of the calculation method and the results. The change of the propagation period of tension was discussed. The factors and variables which effect the propagation period of tension wave is not only related to propagation time in conveyor lines, but is also related to wave propagation lagging affected by running resistance.