摘要
【目的】采用数学方法实时描述LOM薄木层积热压过程中的温度变化,探讨热压工艺参数与温度场分布梯度的关系,为满足成型零件胶合质量与加工精度需求提供参考。【方法】以木材传热理论为基础,根据能量守恒定律,建立LOM薄木层积热压过程的传热控制方程和边界方程,通过基本假设简化模型,将层积热压过程的三维非稳态导热问题简化为一维非稳态传热问题。采用向前差分法对控制方程和边界条件进行离散,利用MATLAB软件实时模拟层积热压过程中零件内部的温度场,观察温度场变化。对不同深度层的温度分布曲线进行分析,解释层积热压过程中温度随层数变化的规律,并根据仿真所得数据绘制二维折线图。【结果】由MATLAB仿真结果和薄木层积热压温度曲线数学模型可知,随着叠加层数增加,热压板对薄木层温度的影响不断减弱。靠近热压板的薄木层温度变化显著,是因为当热压板工作时,薄木层与热压板之间产生强烈的对流换热,薄木层温度上升,当热压层数为15层时,靠近热压板的首层薄木层温度为113.07℃。沿薄木层积垂直方向,随着薄木层深度增加,热压板对薄木层温度的影响不断减弱,是因为离开热压板后低温空气进入并与薄木层进行对流换热,薄木层温度迅速下降,第3层温度为99.61℃,由第1层到第3层,间隔1层,温度下降近14.00℃。在一定深度以下或接近底板的薄木层,温度变化较为缓慢,第13层温度为77.50℃,第15层即靠近底板的薄木层温度为75.64℃,第13层到第15层,间隔1层,温度下降不到2.00℃。【结论】模型中模拟数据与试验数据拟合优度较高,模型对LOM制造工艺具有较强指导作用。本研究所建数学模型与LOM机床工作过程相吻合,所编程序可用于分层实体制造过程中温度场的实时模拟,MATLAB仿真过程可计算模型各点温度变化历程,对提高薄木黏结质量十分重
【Objective】Laminated object manufacturing(LOM)technology stacks layer by layer to produce the required parts.In order to meet the requirements of bonding quality and machining precision of the forming workpiece,the LOM process flow was optimized and improved to solve the influences of the heat affected area on the physical properties of hot melt adhesive in laser cutting process.A mathematical method was used to describe the real-time temperature changes in the laminated hot-pressing process,and the influences of hot-pressing process parameters and temperature field distribution gradient were also discussed so as to provide a reference for ensuring the good adhesion of forming workpiece.【Method】Based on the heat transfer theory of wood and the energy conservation equation,the heat transfer control equation of laminar thermal pressure process was established.By simplifying the model through basic assumptions,the three-dimensional unsteady heat conduction problem of laminar thermal pressure process had been simplified to the one-dimensional unsteady heat transfer problem.The forward difference method was used to discretize the governing equation,and MATLAB software was used to simulate the temperature field in the process of laminar hot-pressing.In addition,the temperature distribution curves of different depth layers were analyzed.According to the data obtained from the simulation,the two-dimensional line graph was drawn to explain the influence rule of temperature changing with the number of layers in the hot-pressing process.【Result】According to the MATLAB simulation results and the mathematical model of the laminated hot-pressing temperature curve,the influences of hot-pressing plate on the temperature of thin wood layer was decreased with the increase of the number of layers.The temperature of the thin wood layer close to the hot-pressing plate was changed significantly.The reason was that when the hot-pressing plate worked,there was a strong convective heat transferred between the thin wood layer
作者
杨春梅
宁礼佳
刘清伟
缪骞
马岩
刘九庆
Yang Chunmei;Ning Lijia;Liu Qingwei;Miao Qian;Ma Yan;Liu Jiuqing(College of Mechanical and Electrical Engineering, Northeast Forestry University,Harbin 150040;School of Astronautics, Harbin Institute of Technology,Harbin 150001)
出处
《林业科学》
EI
CAS
CSCD
北大核心
2021年第10期120-127,共8页
Scientia Silvae Sinicae
基金
广东省重大专项研发计划项目(2020B020216001)
中央高校基本科研业务费专项资金项目(2572020DR12)。
关键词
分层实体制造(LOM)
温度场
实时模拟
控制方程
laminated object manufacturing(LOM)
temperature field
real-time simulation
governing equation
