【作者】 安磊；

【导师】 高建民；

【作者基本信息】 北京林业大学 ， 木材科学与技术， 2007， 硕士

【摘要】 木材干燥应力是干燥过程中产生干燥缺陷的主要因素。本文根据数字散斑相关方法(DSCM)检测应力的原理设计出了一种非接触式无损检测木材干燥过程中应变的方法。干燥过程中应变值最大时并不能代表木材干燥应力最大，传统的木材干燥应力检测方法是在应力发生后进行检测的，而不能检测应力发生时的值，具有一定的局限性。本文试图用木材干燥表面测点位移的变化速率即应变速率来表示木材干燥过程中应力状态，初步提出了建立木材干燥应力评价体系的设想。研究结果表明：木材表面测点位移与时间存在着对数关系，与含水率变化量则呈线性关系；木材干燥应力切片法得到的应力指数有很大的误差，其原因一方面是环境温湿度的影响，另一方面切片不易制作；影响木材干燥应力的主要因素有应变速率、干燥温度、含水率梯度、温度梯度。为了更为精确的证实这个观点，本文还设计了干燥应力与其主要影响因素的数据自动采集系统，初步系统可以完成应变速率和平均含水率的数据自动采集；改进后的系统则可实现自动记录应变速率、木材含水率、含水率梯度、温度梯度与应力的关系。更多还原

【Abstract】 The drying stress is the main reason that causes the drying defects. This essay contains a design which can measure the changes of drying stress. The design is according the digital speckle correlation method (DSCM), which special characters are untouched the surfaces of the drying wood and unnecessary to destroy the wood. The traditional measuring method is a little limited that can not detect the number of stress in the very beginning. In the paper, it is the first time to mention how to build up a judging system by straining velocity which is represented the drying stress. The results of this study show that: the displacement of the testing point has a logarithm relationship with the time of drying; however, it has a linear relationship with the changing of moisture content. The mean errors of stress-section method are huge. There are two reasons; one is the infection of the environmental temperature and moisture content, the other is it is difficult to produce stress-sections. The main reasons which are able to infect the wood drying stress are the straining velocity, the drying temperature, the gradient of moisture, the gradient of temperature. In corroding to prove these, the essay also concludes a design of auto-collecting digital system, which is about the drying stress and its infecting reasons. The system can basically collect the strain velocity and moisture. The improved system also can measure the relationships between the drying stress and the strain velocities, the moisture content, the gradient of moisture, the gradient of temperature.更多还原