木材干燥过程中应力与应变检测方法初探

Preliminary Exploration on the Detection Method of Stress and Strain in the Process of Wood Drying

[目的]探索木材干燥过程中应力与应变的检测方法。[方法]根据数字散斑相关方法的原理设计一种非接触式检测木材干燥应力的方法,用应变速率表示木材干燥过程中应力状态,研究木材表面测点位移与干燥时间、温度和含水率的关系。[结果]木材测点位移平均速率有一个峰值,温度越低,峰值出现得越晚,说明应变滞后于应力;同一材料、同一温度的平均位移曲线,端部的峰值先于中部出现。木材表面测点位移与干燥时间存在对数关系,与含水率变化呈线性关系。随着时间的推移,干燥速率下降,应变速率变小。[结论]影响木材干燥应力的主要因素有干燥应变速率、干燥温度、含水率梯度和温度梯度。

[Objective] The study aimed to explore the detection method of stress and strain in the process of wood drying.[Method] Based on the principles of digital speckle correlation method,a non-contact detection method of wood drying stress was designed.The straining velocity was used to represent the stress state in the process of wood drying and the relationship between the displacement of measured point on the surface of wood and drying time and temperature and water content was studied.[Result] The average displacement velocity of measured point on the wood had a peak value,the lower the temperature was,the later the peak value appeared,indicating that strain lagged stress.On the average displacement curve of the same material at the same temperature,the peak value of the end appeared before that of the middle.The displacement of measured point on the surface of wood had logarithmic relationship with drying time and linear relationship with the change of water content.As the time extended,the drying velocity decreased and the straining velocity diminished.[Conclusion] The main factors influencing wood drying stress were drying straining velocity,drying temperature,water content grads and temperature grads.