Two-dimensional Imaging Technique Of Wood Defects Based On Stress Wave

The internal defects of woods, such as decay and holes, will seriously affect physical andmechanical properties of woods. Those defects which are the important parts in wood inspectioncould reduce quality and downgrade of woods. There are many ancient wooden structures inChina which have important historical significance. The nondestructive detection technologiesand equipments, which caused no original structural damage, were used in repairment andprotection of ancient wooden structures. Therefore, nondestructive detection technologies forwood internal defects have aroused widespread attention.In all the detection methods of wood property, stress wave nondestructive testingtechnology has become the focus of domestic and foreign research because of its longtransmission distance, easy to use, reliable, fast and other characteristics. But in the patentprotection and technology blockade, there were no domestic stress wave detection products, sothe expensive imported equipments were needed. It is important to develpe the domestic stresswave detection products to reduce the research and production cost of academy and forestryenterprise. It will also improve wood nondestructive testing technology.Stress wave detection for physical and mechanical properties and internal defects of woodswere comprehensive analyzed, also the propagation law and detection methods of stress wave inwoods were widely studied. Furthermore, based on travel time, distance and the velocity of stresswave, a points velocity algorithm, a lines velocity algorithm and a weighting lines velocityalgorithm were proposed and established. A large number of actual measurement data were usedto test the validity of the three algorithms, which measured by FAKOPP and obtained from mainhall and opisthodomos hall in sea god temple of ShanHaiGuan. It was shown that the pointsvelocity algorithm and lines velocity algorithm could indicate the basic characterization of woodinternal defects. and the results of weighting lines velocity algorithm was as same as FAKOPP. A stress wave nondestructive detection equipment was developed, also a control softwareand man-machine interface for the equipment were programed. A practical tests were carried outbased on the wooden disc specimens, to compared the characteristics of the equipment andFAKOPP. It is found that the equipment not only can detect travel time and speed of stress wavein wood effectively and accurately, but also obtain a two-dimensional image of internal defectsof wood which was as same as FAKOPP. The equipment has the advantages of high precision,low cost, easy operation, and a certain market competition.A wood defect two-dimensional imaging technique based on stress wave, which has madea better test results, was established after the above theory research and actual equipmentdevelopment. Compared with foreign equipment, the equipment developed by this technique hada lower price and higher performance. It will be able to obtain good social and economic benefitsif the equipment can achieve mass production..