Study On On-line Detecting Technique Of Wood Drying Stress

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.