Comparing Studies Between Stress-Wave And Ultrasonic In Inner Defect Wood

Wood defects have different impacts on the quality of wood products, which may cause reduction of wood value, or even serious destruction so that they can not be used any more. For many years, people are always dedicated in studying some quick and accurate testing method to detect wood defects in order to save our limited wood resources and elevate utilization efficiency of wood. Therefore, the research on testing the wood inner defects has meaningful significance and practicable value.The sensitivity, reliability and application of wood defects testing are influenced by wood properties and external conditions when using stress-wave testing and ultrasonic testing. Hence, it is necessary to do deep studies on the comparison of the two testing methods.The wood samples are from main species in the Northeast of China, and some defects like holes, decay and crevices are artificially made in woods without any defects. The testing equipments are respectively ARBOTOM stress-wave testing equipment imported from Germany and RSM-SY5 ultrasonic testing equipment made in Institute of Rock and Soil Mechanics, Chinese Academy of Science, Wuhan.The variations of transmission parameters and dynamic elastic modulus of good woods and defect woods under different species and conditions by using stress-wave equipment and ultrasonic equipment are mainly studied in the thesis. The variations of disseminating parameters are closely relevant to the extent of wood defects. According to the principle, the comparison between good woods and defect woods by the analytical software SPSS 10.0 is preceded. Meanwhile, the influences of some factors such as different density, water content, and inner holes with different size and inner decay with different extent, inner knots with different size and cleft with different depth on transmission parameters and dynamic elastic modulus are systematically analyzed. The comparison results show that the testing reliability, application sapects of the two methods is diffierent under different wood properties and inner defect types. Ultrasonic testing is sensitive to wood density, and the testing results of inner decay, inner holes and knots are better than that of stress-wave testing. Stress-wave testing is greatly inflenced by water content of woods, which is suitable to test big size defects of woods. Finally, image of the section acquired from stress-wave testing equipment is digitally preceded and filtering processing is done on the signals captured by ultrasonic using Matlab software. The corresponding changes of images and wave lines can directly reflect the inner defects of wood samples, and the reliability of combination of the testing methods can be further improved.The studies will provide reference for better application of stress-wave tesing and ultrasonic testing in woods and wooden structure.