| Nowadays,green and energy-saving is the development goal of various industries.To improve the green and energy-saving performance of belt conveyor in mechanical industry,it is necessary to reduce the total running resistance.For horizontal long-distance belt conveyor,the main resistance dominates and for inclined long-distance belt conveyor,the main resistance is second only to lifting resistance.And among the main resistance,the proportion of indentation rolling resistance(IRR)is the largest.Therefore,it is the focus of research to accurately predict and reduce the IRR and determine the artificial friction coefficient according to the working conditions.In this paper,the method of combining theoretical analysis with finite element simulation and experimental verification is carried out.The main results are as follows:Because the generalized Maxwell model contains 2N+1 elements which can fully characterize the viscoelasticity of the material,the generalized Maxwell model is selected to represent the viscoelasticity of the rubber material of the conveyor belt.And the mathematical model of IRR is established by combining with the Winkler model.The content of this section is divided into two parts.In the first part,starting from the deformation of the contact area when the belt passes through the idler,the mathematical model of IRR is established by the parameters of the generalized Maxwell model.And then the model is simplified so that the final mathematical model can directly reflect the influence law of the parameters for working condition.In the second part,the mathematical model is established with the help of the storage modulus and loss modulus of rubber material for conveyor belt by means of mathematical lemma.According to the mathematical model,it can be known that the parameters affecting IRR mainly include vertical load,belt speed,idler radius,bottom cover thickness of belt and material viscoelastic paramters.In use,the generalized Maxwell model is embodied for numerical analysis.In this paper,the generalized Maxwell model is solidified into a three-element Maxwell solid model and a three-element Kelvin solid model.The mathematical models of the IRR are established respectively.In this process,the environmental temperature is fully considered,which makes the mathematical models more profect.The mathematical models of IRR based on the three-element Kelvin solid model and the three-element Maxwell solid model are different,but the two have the same features,that is,they are all represented by parameters such as ambient temperature,belt speed,idler radius,bottom cover thickness of belt and vertical load.The influence of the ambient temperature on the IRR is specifically expressed as the influence of the ambient temperature on the elastic moduli and the viscosity coefficient.Their expressions are based on the dynamica displacement loading theory and tests of the rubber material of conveyor belt.According to the different mathematical models of IRR,the effects of working conditions on the IRR are analyzed in detail.The results are not same,mainly in the influence of belt speed and temperature on IRR.In order to verify the correctness,finite element simulation and experimental test are carried out.The finite element simulation test is completed by ANSYS workbench software.The two-parameter model of Mooney-Rivlin is used to define the cover material of belt.Based on the ambient temperature,three sets of finite element simulations at different temperatures are carried out for the bottom cover layer model of conveyor belt and fabric core conveyor belt model.The results show that the theoretical results of the three-element Kelvin solid model are similar to the finite element simulation.At the same time,it is proved that the belt skeleton material has little influence on IRR,so it is often neglected in the analysis.In order to fulfill the test verification,a domestic advanced test system for IRR of belt conveyor is designed and developed.The system has an ambient temperature control room,and the temperature range is-25??50? in order to simulate the ambient temperature of belt conveyor in engineering.A series of experiments are accomplished with ambient temperature and belt speed as variables.The results show that when other working conditions are kept constant,the IRR decreases with the increase of temperature.When the belt speed is the only variable,IRR increases with the increase of belt speed in a certain range.In order to precisely determine the value of artificial friction coefficient of belt conveyor,a comprehensive test system for artificial friction coefficient is established.By using the system,the determination of artificial friction coefficient can be realized under any combination of working conditions such as different loads,idler diameters,groove angles of idler group and belt speeds.Experiments are carried out with vertical load,belt speed and groove angle of idler group.The results show that artificial friction coefficient increases with the increases of the three parameters.The artificial friction coefficients are not same under different working conditions.Obtaining the actual artificial friction coefficient provides a strong guarantee for the green and energy-saving development of belt conveyor undoubtedly. |
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