【作者】 于贵文；

【导师】 顾继友； 胡英成；

【作者基本信息】 东北林业大学 ， 木材科学与技术， 2013， 博士

【摘要】 木塑板材作为木塑复合材料中的一种型材,广泛地应用在建筑、装潢、交通运输、园林等行业中。为了节约木材和石油资源,加强人们对该类产品的力学性能及使用安全性的了解,扩展这种经济、环保且可回收利用的木塑板材的应用领域,本文研究了多种规格聚乙烯基木纤维(或木粉)增强的木塑板材的力学性能的无损检测、可靠性分析及预测,并分析了两种木塑结构体系的可靠性。在木塑板材的无损检测试验中,分别是以新的和回收的高密度聚乙烯为基体木纤维增强的有无加强筋的木塑板材、高密度聚乙烯为基体木粉增强的不同厚度和密度木塑板材为实验材料。运用了纵波传播、纵向共振和弯曲振动三种无损检测方法及三点弯曲试验方法,分别获得上述各种木塑板材的动态和静态弹性模量,并分别对各种试件的动态和静态弹性模量进行回归分析。结果表明：它们的动态和静态弹性模量分别具有较强的相关性,三种无损检测方法均适合检测上述各种木塑板材的动态弹性模量；新的和回收的高密度聚乙烯基木塑板材的动态和静态弹性模量的均值几乎相等,回收高密度聚乙烯适合生产木塑板材；木塑板材的厚度或加强筋均能提高木塑板材的动态和静态弹性模量,并且,其动态和静态弹性模量之间的回归曲线近似于同一直线；提高密度能够改善木塑板材的力学性能,但动态和静态弹性模量之间的回归曲线呈非线性关系。以三种高密度聚乙烯基木粉增强的木塑板材为试验材料,通过三点弯曲试验获得相应试件的最大弯曲力和静曲强度,使用一次二阶矩法、改进一次二阶矩法、蒙特卡罗法和验算点展开有限元法分别计算各类木塑板材的可靠性。结果表明：四种可靠性分析方法均适合评价木塑板材的可靠性；基于一次二阶矩法不同密度木塑板材的可靠度分别为99.95%和98.46%；基于一次二阶矩法不同厚度木塑板材的可靠度分别为99.916%和85.31%；基于改进一次二阶矩法木塑板材的可靠度为99.9767%；基于验算点有限元法木塑板材的可靠度为98.461%；基于蒙特卡罗法木塑板材的可靠度为83.90%。基于验算点展开随机有限元法木塑板材的可靠度为98.461%。在木塑悬臂梁结构的可靠性分析中,通过对任意j点和A点功能函数的相关性分析,得到两个功能函数具有强的相关系,获得影响木塑悬臂梁结构可靠性的功能函数,运用一次二阶矩法计算其可靠度,悬臂梁的可靠度为99.7882%。在单跨双层木塑框架结构的可靠性分析中,塑性铰的个数为14个,利用失效树分析法确定了8个主要失效机构,建立8个机构的功能函数,并计算各功能函数的可靠性指标及失效概率,通过相关性分析确定该结构体系失效的代表机构,运用概率性网络评价技术计算其失效概率该单跨双层木塑框架结构的可靠度为91.098%。以两种高密度聚乙烯为基体木粉增强的木塑板材为实验材料,通过上述动态和静态试验方法分别获得两种试件的动态弹性模量最大弯曲力和静曲强度。通过对第1组试件的动态弹性模量和最大最大弯曲力的回归分析,获得最大弯曲力的预测模型,并预测其它相同试件的最大弯曲力,运用一次二阶矩法计算其可靠度。结果表明：预测最大弯曲力略大于检测最大弯曲力,基于预测最大弯曲力的可靠度也略大于基于检测最大弯曲力的可靠度。通过对第1组试件的动态弹性模量和静曲强度的回归分析,获得静曲强度的预测模型,并预测其它相同试件的静曲强度,运用改进一次二阶矩法计算其可靠度,结果表明：预测和检测的静曲强度几乎相同,基于预测和检测的静曲强度的可靠度值也近似相等。综上所述,三种无损检测方法均适合检测相应的木塑板材的动态弹性模量；四种可靠性分析方法均可用以评价木塑板材在实际应用中的安全性能；通过建立动态和静态力学性能之间的预测模型,其它相同木塑板材的可靠性可以通过无损检测的方法进行预测；木塑结构体系的可靠性也可以运用有关理论和方法进行分析和评价。更多还原

【Abstract】 Wood-plastic plank (WPP) as a profile in the wood-plastic composites (WPC) is widely used in the field of construction, decoration, transportation and garden. In order to save timber and oil resources, to understand the mechanical properties and security in use of WPP, and to expand the scope of application of economic, environmental and recyclable WPP, this paper has carried out nondestructive testing (NDT) of mechanical properties, reliability analysis and prediction of a variety of WPP, and analyzed reliabilities of the two types of wood-plastic structural system.In the NDT, whether the stiffener WPP that wood fiber (or wood flour) reinforced new and recycled high density polyethylene (HDPE), and the different thickness (or density) WPP of wood flour reinforced HDPE as the test materials, respectivily, using three NDT methods (longitudinal transmission, longitudinal vibration and flexural vibration) and three point bending test metod, respectivily, the dynamic and static modulus of elasticity (MOE) of above WPP were measured, and the regression analysis between dynamic and static MOE was carried out, respectively. The results show that has a strong correlation between the dynamic and static MOE of WPP of new and recycled HDPE reinforced by wood fiber, and the mean values of dynamic and static MOE are almost same, so, the recycled HDPE is suitable for the production of WPP. The thickness and stiffener can improve the dynamic and static MOE of WPP, and the Regression curve between dynamic and static MOE of them is proportional relationship, respectively. The density of specimen can also improve the dynamic and static MOE of WPP, but, the Regression curve between dynamic and static MOE of different density specimens is not proportional relationship.Three WPP of wood flour reinforced HDPE as the test materials, the maximum bending force and modulus of repture (MOR) of specimens were obtained by the three point bending test, the reliabilities of different WPP were analyzed by first order second moment (FOSM) method, improved FOSM method, Monte Carlo method and checking point stochastic finite element method, respectively. The results showed that above four methods of reliability analysis are suitable to evaluate the reliabilities of three WPP, respectively. The reliabilities of different density WPP based on the FOSM method are99.95%and98.46%, respectively. The reliabilities of different thickness WPP based on the FOSM method are99.916%and85.31%, respectively. The reliability of WPP based on the improved FOSM method is99.9767%. The reliability of WPP based on the Monte Carlo method is83.90%. The reliability of WPP based on the checking point stochastic finite element method is98.461%.In the reliability analysis of wood-plastic cantilever structure, two performance functions of any j point and A point has a correlation coefficient through correlation analysis between them, the performance function was got, which impacted reliability of wood-plastic cantilever structure, the reliability of wood-plastic cantilever structure based on the FOSM method is99.7882%. In reliability analysis of single span double wood-plastic frame structure, the number of plastic hinges were14,8main failure institutions were determined by the fault tree analysis method, and the performance functions of8main failure institutions were established, then, reliability indexes and failure probabilities of these performance functions were calculated by the improved FOSM, the representative institutions were determined by correlation analysis between performance functions, finally, the failure probability of single span double wood-plastic frame structure was calculated by probabilistic network evaluation techniques, the reliability of single span double wood-plastic frame structure is91.098%.Two WPP of wood flour reinforced high density polyethylene as the test materials, the dynamic MOE, maximum bending force and MOR of specimens were obtained by the above dynamic and static test methods. The prediction model of maximum bending force was getted by regression analysis of the dynamic MOE and maximum bending force of specimens in Group1, the maximum bending forces of orther same specimens was predicted, and the reliability of orther same specimens was calculated by the FOSM method. The results showed that the predicted maximum bending force is slightly larger than the measured maximum bending force, and the reliability based on predicted maximum bending forces is also slightly larger than that based on measured maximum bending forces. The prediction model of MOR was also obtained by regression analysis between dynamic MOE and static MOR of specimens in Group1, the MOR of other same specimens was predicted by the prediction model, and the reliability of orther same specimens was calculated by the improved FOSM method, the results show that the predicted and measured MOR are almost same, and the reliabilities based on the predicted and measured MOR are approximately equal.In summary, three NDT methods are suitable for the measurement of the dynamic MOE of WPP. Four methods of reliability analysis can be used to evaluate the performance of WPP in the practical application. Through the establishment of the prediction model between dynamic and static mechanical properties of WPP, the reliability of other same WPP can be predicted by three NDT methods. The reliability wood-plastic structural system can also be evaluated using the theory and methods.更多还原