The Simulation And Optimization Of The Hot-pressing Progress Of Producing Fast-growing Poplar Laminated Veneer Lumber(LVL)

The study uses the fast-growing poplar as basic material,and simulate the hot-pressing progress of producing laminated veneer lumber(LVL)by numerical simulation analysis method.Through the MOE and MOR values of the laminated material,it can directly reflect the simulation result,then using experiments tests the results,comparing the experimental results with the simulation results verifies the accuracy of the simulation.Finally,in order to improve the simulation degree of optimization model.,the paper studies the relationship between simulation results and experimental results.This study provides a new method to study the hot-pressing process of LVL,this method reduces the amount of experiment needed in the research process and the workload of the experimental data analysis.The main conclusions of this study are as follows:(1)The basic properties of the fast-growing poplar were measured by experiments,it gets data of the basic density?nine elastic constants?specific values of thermal conductivity and specific heat capacity,the basic density is 0.464 g/cm3;elastic modulus in three directions EL?ER?ET are 13884.4MPa?1069.2MPa and 807.7MPa;Poisson's ratio in three directions ?LR??LT??RT are 0.358?0.457 and 0.668;shear modulus of elasticity in three directions GLR?GLT?GRT are 131.4MPa?90.5MPa and 73.7MPa,Coefficient of thermal conductivity and specific heat are 0.095W/(m·?)and 1.635kJ/(kg·?)(2)the paper builds a finite element model of the hot-pressure process of LVL by the basic material properties of fast-growing poplar,using this model to simulate gets the temperature distribution and stress compression of each board.The heating rate of each board is mainly affected by the hot-pressure temperature,The temperature of surface board is increased linearly,reachs the max temperature at 100s,the temperature of other boards presents increasing linearly and then slow curve grow;Material compression ratio is related to hot-pressing pressure,the surface board compression rate is the largest,and the internal boards compression rate gradually decreases.Board firstly goes through elastic deformation stage before 300s,and then board goes through plastic deformation stage after 300s.(3)Through the experimental verification,there is a certain deviation between the experimental value and the simulation value,most of the experimental value is larger than the simulation value,the difference of MOE between the simulation value and the experimental value is 144MPa?1332MPa,the accuracy rate is 87.6%?98.1%;the difference of MOR between the simulation value and the experimental value is 10.46MPa?26.27MPa,the accuracy rate is 65.9%?83.2%.It shows that the simulation results of MOE are similar to experimental value compared with those of MOR.(4)According to the relationship between MOE and MOR's simulation value and experimental value,it gets the equation of linear regression to optimize the simulation value and tests this equation,the equation of linear regression optimizing the result of MOE and MOR are y=1.1163x-246.16 and y=1.0307x+13.069,the coefficient of correlation R2 are 0.7427 and 0.6218.Using it to optimize the simulation results.(5)The optimization results are verified by experiments,it shows that the simulation values of MOE are improved by 664.8MPa and 604.6MPa respectively,the accuracy rate are improved by 7.64%and 7.11%,reaches 97.64%and 93.22%;The optimization of MOR changes more significant,the simulation values of MOR improved by 14.91MPa and 14.55MPa,the accuracy rate are improved by 16.48%and 20.93%,reaches 82.75%and 90.40%.It shows that the method of linear regression can be used to optimizing.