| In the contemporary era of increasingly intense energy use,the development of biomass energy plays an increasingly important role.As a unique perennial thicket plant in Inner Mongolia,the study object of this paper is characterized by high calorific value and rejuvenation,but its raw materials in the natural state,the density is low,and the production area is scattered,which leads to high transportation costs.Therefore,the research on the compact molding technology of Salix psammophila has practical significance.At present,the research of compact molding technology is mostly based on a method,which uses biomass as a continuous finite element.Analyze or analyze the compact molding process of biomass from the perspective of particles based on discrete element theory.The actual process is the change of the internal mechanism on the meso-scale and the macroscopic phenomenon occurs.In addition,the quality of the molding block is poor and the equipment is severely worn.The problem also needs to be solved urgently.In view of the above problems,this paper analyzes the visco-elastoplastic mechanics changes of the dense compaction molding process from the discrete element and finite element graduate students,and builds a mechanical model of the compact molding process,which provides the development of biomass compact molding Theoretical basis.Firstly,from the perspective of multi-scale analysis of the biomass compact forming process,the macro based on the finite element method,equivalent to the biomass forming block as a solid,based on the continuum mechanics theory,the explicit analysis solver was analyzed using a quasi-static loading method.In the unidirectional molding process,the stress changes in the early,middle,middle and late stages of pressing are selected to analyze the stress changes,and the stress is gradually increased from zero,and the stress is concentrated on the upper surface from the beginning to the upper half to the entire material column.The conclusion of the distribution.Based on the discrete element method,the biomass is classified into soft matter,and the compact molding process of biomass is analyzed based on the theory of bulk mechanics.Particles and contact force are analyzed at four moments: initial loading,elastic deformation start,plastic deformation start and end.And the transmission mechanism and law of the velocity field,the particle distribution is loose to dense,the contact force distribution is disordered to form a rhombus,then to a large ring,and finally to a small triangular stable structure.The velocity field undergoes vertical downwards,forming a separation zone.Move down until the conclusion disappears.Secondly,in order to obtain a more accurate and reliable mold stress and strain cloud map,give full play to the advantages of discrete elements and finite elements,the discrete elements and finite elements are coupled for simulation,and the force and position information calculated by discrete elements are used as finite elements Input,analyze the force and deformation of the external mold,solve the problem that the traditional finite element analysis can not predict the accurate load distribution,and draw the conclusion that the mold force and deformation gradually increase from top to bottom along the central axis.Finally,according to the discrete element simulation results,the dense molding process of Salix psammophila is divided into four stages of feed preloading,viscoelasticity,viscoplasticity,and stress relaxation in turn using the pressure difference method,and the simulation components are used according to the different characteristics of each stage Establish mechanical models and mechanical equations separately,and fit the data to find unknown parameters,and analyze the internal mechanism of unknown parameter changes.The four-stage mechanical equations are obtained,and the parameter changes are mainly due to the fact that the gap between the particles decreases as the loading progresses,it is not easy to be compressed,and the temperature increases,and the lignin softens. |
