| Loader have been widely used in construction,mine,railway and other construction in modern society.The study of energy saving and consumption reduction has become an important issue in the design and optimization of loader.In the whole working cycle of the loader,the energy consumption of the shovel is the largest,and the energy consumption of the shovel is mainly from the reaction force of the working medium to the loader during the operation.Therefore,reducing working resistance is the most direct way to realize energy saving and emission reduction of loader.At present,most scholars use discrete element method to analyze the working resistance of loader,and the material characteristic parameter is the basic data of discrete element simulation analysis,and its accuracy is an important factor that affects the simulation result,in order to obtain the more accurate analysis result,this paper mainly studies the characteristic parameters of typical material in loader operation.The main tasks are as follows:(1)First,according to different factors,the materials for loader operation are classified.Secondly,the physical and mechanical properties and contact characteristics of the material are analyzed.Thirdly,the friction mechanism of granular materials is analyzed by friction theory.Finally,a reasonable simulation scheme of orthogonal test is designed.The sensitivity of contact parameters is analyzed by using range analysis method,and the influence of each parameter on the simulation results of operation resistance is mainly analyzed.The results show that the static friction coefficient has the greatest influence on the simulation results,followed by the rolling friction coefficient and the collision recovery coefficient,and the simulation results obtained by the combination of different parameters have obvious differences.Therefore,it is necessary to measure the contact parameters of different materials according to their true characteristics,which provides a theoretical basis for the further study of contact parameters of materials.(2)The contact parameters of crushed stone were studied.First,according to Coulomb's law and inclined plane principle,a new experimental device for static friction coefficient is designed and improved.,and its feasibility is verified,the influence of particle size,shape and contact material on the static friction coefficient is analyzed.It is concluded that the main and secondary order of the influence of the three factors on the static friction coefficient is contact material,shape and particle size.Secondly,based on the law of conservation of energy and the principle of mutual conversion of dynamic energy,the rolling friction coefficient and collision recovery coefficient of gravel arestudied experimentally.It will provide some basis for future analysis of work resistance.(3)Taking anthracite,cassava and sugarcane as an example,the contact parameters of other typical materials for loader operation were studied.First,the static friction coefficient and rolling friction coefficient of the three materials are measured by experiments.Secondly,the test method of collision recovery coefficient of different shape materials is studied.Based on kinematics equation principle,a test device for collision recovery coefficient is designed,and the collision recovery coefficient of three kinds of materials is measured separately.It will provide some basis for future analysis of work resistance.(4)First,anthracite is taken as an example to verify the feasibility of the method of collision restitution coefficient by comparing the results of the rest angle test with the simulation results.Secondly,taking gravel material as an example,by comparing the experimental results and simulation results of the rest angle,the simulation accuracy of contact parameters in the direct default software and the contact parameters measured in this paper is analyzed.It will provide some references for the simulation analysis of discrete element in future. |
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