Thermal behavior at wood and composite wood surfaces

当用白炽灯照射表面时，端面吸收的热量是边缘纹理表面的1.2倍。测定了不同颜色和密度的木材和复合木材在白炽灯照射下的表面温升速率，模拟了人体皮肤与复合木材界面处的热行为。建立了基于有限差分数值方法的传热模型，分析了换热器各层的温度和传热速率的变化。该模型可用于估算人的手掌与木材表面接触时所感受到的感觉温度。利用软木树种的节子与周围组织的热特性差异，采用热像法检测节子。用白炽灯照射木材表面，测量表面温度的变化率。结果表明，结粒区的温度上升速率最小，其次是裂粒区。从加热开始后60s的热像图上可以检测到节结的尺寸，热是根据缺陷部位应力-应变曲线上的磁滞回线的能量损失产生的。通过反复弯曲的热像可以检测出裂纹和某些缺陷。

The end surfaces absorbed 1.2 times more heat than did these of edge-grained surfaces when the surfaces are irradiated with incandescent lamps. The rate of surface temperature rise for various wood and composite wood with various colors and densities was determined when they were irradiated with incandescent lamps.Thermal behavior at a boundary between human skin and wood composites was simulated. The thermal transfer model based on numerical method with finite differences was proposed to analyze the changes in temperature and rate of heat transfer at the interfeaces. The model was valuable to estimate the sensory warmth felt by man's palm in conact with the wood surface.The thermogaphic method was applied to detect the knots, using with a difference in thermal properties of knot from the surrounding tissues for softwood species. The lumber surface was radiated with incandescent lamps and the rate of change in surface temperature was measured. As the results the rate of temprature rise was the lowest on the knot, follwed by distored grain region. From the thermograph at 60s after commencement of heating it has been found that the knot sizes could be detected.Heat is generated according to the energy loss of hysteresis loops which is obs erved at stress-strain curves of defect portions. Cracks and some kinds of defects could be detected by chermal images with repeated bending.