Constitutive Equation And Numerical Simulation Of Warm Compaction Of Poplar Powders

Since the Second World War,with the rise of the new technological revolution,the fossil fuel resources have been over exploited,the forest resources and vegetation have been seriously damaged,and the lack of wood land too many to count.It is a good way by using cheap wood resources such as farming and forestry surplus to produce a certain function of wood composite material to alleviate the problems of resources and environment.In this paper,the residue of fast-growing poplar was used as base material,based on the study of the basic properties of the wood powder functional materials and the forming process of warm compaction,to simulate wood functional materials process of warm compaction process by finite element method.The results can provide theoretical guidance for development of warm compaction technology of wood functional materials,and can be used as the mechanism analysis and theoretic criterion for failure of warm compaction of wood functional materials.The main tasks are as follows:(1)The basic properties of the powder of wood functional material,such as density,compressibility,fluidity and porosity,were studied.The results show that the finer the powder,the smaller the porosity,the greater the apparent density and tap density of powder,the greater the density and the density of the solid,the worse the fluidity and the better the compressibility,but the change trend is not obvious.(2)Under the 220? or less environmental temperature,the thermal gravimetric analysis of poplar wood powder,warm compaction and wood functional materials were carried out,the poplar powder is.at the same thermo-gravimetric index as that of the warm compaction,were 7.26%and 7.19%respectively;The weight loss rate of wood functional material was 5.01%,the results show that the wood functional material has certain weather resistance.(3)The woodiness powder granularity,forming temperature and forming pressure of the functional materials as impact factor,the performance test indicators is about the surface hardness,static bending strength,internal bonding strength and elastic modulus of wood functional materials,the warm compaction process of wood functional materials was studied,the optimum forming process parameters of warm compaction of wood functional materials were obtained:powder size is 60 mesh,the forming temperature is 160?,the forming pressure is 60MPa.Based on the optimal preparation process of wood microstructure of functional materials plasticizing fully,fracture morphology has obvious characteristics of ductile fracture,it shows good comprehensive performance(surface hardness 77.3 kg/mm2,static bending strength78.14MPa,internal bond strength 7.44MPa,elastic modulus 5.52GPa).(4)Based on chuanbei formula and function of woodiness material temperature pressure forming stress and strain test data,inversion of model parameters using simulated annealing optimization algorithm,the constitutive equations of the warm compaction process of wood functional materials were constructed;Based on the simulation of the constitutive equation,it is found that the equation can be used to describe the stress-strain relationship of the process of warm compaction;With the aid of the BP neural network fitting function of wooden material temperature forming stress and strain test data,predict the constitutive relation of the warm compaction of wood functional materials,the predicted results agree well with the experimental data,it is proved that the BP neural network method is feasible to study the constitutive relation of the warm compaction process of wood functional materials.(5)Numerical simulation of warm compaction process of wood functional materials by MSC.Marc software.The numerical simulation analysis of the temperature field of the model and the influence of pressure and temperature on the relative density of compacts were simulated.The results show that The temperature field of the compaction is reduced from the outside to the inside;With the increase of pressure,the relative density of compacts increases obviously,and the relative density of the compacts is gradient distribution from top to bottom,the relative density increases when the forming pressure reaches 60MPa,and finally becomes stable;The relative density of compacts increases with the increase of temperature,the relative density increases when the temperature reaches 160?.The simulation results are in good agreement with the experimental results.