木质功能材料温压成形本构方程与数值模拟

发布时间：2018-05-24 02:33

  本文选题：木质功能材料 + 温压成形　； 参考：《中南林业科技大学》2017年硕士论文

【摘要】：自二战以来随着新技术革命的兴起,石化资源被过度开采、森林资源与植被遭到严重破坏,木材匮乏国度不计其数,高值清洁利用农林剩余物等廉价资源制备木质功能复合材料是缓解资源、环境问题的有利手段。本文以速生白杨剩余物为基材,在研究木质功能材料原料粉末基本性能及其温压成形工艺的基础上,采用理论与实践相结合的方法构建了木质功能材料温压成形本构方程;采用有限元法对木质功能材料温压成形过程进行了数值模拟。研究成果可作为木质功能材料批量生产工艺制订的理论依据,并可作为木质功能材料温压成形机理分析及失效成因分析的理论判据。完成的主要工作如下:1)研究了木质功能材料原料粉末的密度、压缩性、流动性和孔隙度等基本性能,发现木质功能材料原料粉末越细,其孔隙率越小、松装密度和振实密度越大、流动性越差、压缩性越好,但变化趋势不明显。(2)在小于220℃温度环境下,对基材杨木粉末及其温压压坯与木质功能材料进行了热失重分析,发现杨木粉末与其温压压坯的热失重处于同一水平,分别为7.26%、7.19%;木质功能材料的热失重率为5.01%,说明木质功能材料具有一定的耐候性能。(3)以木质功能材料原料粉末粒度、成形温度、成形压力为影响因子,以木质功能材料表面硬度、静曲强度、内结合强度、弹性模量为考查指标,对木质功能材料温压成形工艺进行了研究,获得了最优工艺参数组合,即:原料粉末粒度-60目、成形温度160℃、成形压力60MPa。基于最优工艺制备的木质功能材料微观组织塑化充分,断口具有明显韧性断裂特征,体现出良好的综合性能(表面硬度77.3 kg/mm2、静曲强度为78.14MPa、内结合强度7.44MPa、弹性模量5.52GPa)。(4)基于川北公式和木质功能材料温压成形应力应变试验数据,采用模拟退火优化算法反演模型参数,构建了木质功能材料温压成形过程本构方程;通过对本构方程的模拟,发现该方程能较好的描述木质功能材料温压成形过程中的应力应变关系;借助BP神经网络法拟合木质功能材料温压成形应力应变试验数据,预测了木质功能材料温压成形本构关系,预测结果与试验数数据基本吻,证明采用BP神经网络法研究木质功能材料温压成形过程本构关系切实可行。(5)借助MSC.Marc软件对木质功能材料温压成形过程进行了数值模拟。针对压坯温度场及成形压力与成形温度对压坯相对密度的影响进行了数值模拟,发现:压坯温度场由外及里呈递减梯度分布;压坯相对密度随着压力的增加明显增大,当成形压力达到60MPa时压坯的相对密度增幅减缓,最终趋于稳定;压坯相对密度从上至下单向递减呈梯度分布;压坯的相对密度随成形温度升高而增加,当达到160℃后,其相对密度增幅明显减小。模拟结果与单向模压成形试验情况吻合。
[Abstract]:Since World War II, with the rise of new technological revolutions, petrochemical resources have been overexploited, forest resources and vegetation have been severely damaged, and there are countless countries where timber is scarce. High value clean use of cheap resources such as agricultural and forestry residues to prepare wood functional composites is a good means to alleviate the problem of resources and environment. In this paper, based on the study of the basic properties of wood functional material powder and its warm compaction forming process, the constitutive equation of wood functional material warm compaction forming was established by combining theory with practice. The forming process of wood functional material was simulated by finite element method. The research results can be used as the theoretical basis for the mass production process of wood functional materials, as well as the theoretical criteria for the analysis of warm compaction mechanism and failure cause analysis of wood functional materials. The main work accomplished is as follows: (1) the density, compressibility, fluidity and porosity of the raw powder of wood functional material are studied. It is found that the finer the powder of wood functional material, the smaller the porosity. The greater the density of loosening and the density of vibration, the worse the fluidity, the better the compressibility, but the less obvious the changing trend is.) the thermogravimetric analysis of poplar powder, its warm compacted blank and wood functional material is carried out under the temperature of less than 220 鈩，

本文编号：1927346