【作者】 林文树；

【导师】 王立海；

【作者基本信息】 东北林业大学 ， 森林工程， 2005， 硕士

【摘要】 木材缺陷使木材材质受到不同程度地影响,降低甚至完全失去其使用价值。为了节约木材资源,提高木材的利用率,几十年来人们一直在致力于研究一些迅速而准确的探测木材缺陷的方法。因此,对木材内部缺陷的研究有着十分重要的实际意义。 应力波和超声波在对木材进行缺陷检测时,由于受到木材特性和外部条件的影响,对缺陷的敏感度、缺陷检测可靠性及应用范围有所不同。因此,为更好地应用应力波和超声波对木材内部缺陷进行检测,有必要对这两种检测方法做深入的对比研究。 研究的木材试件是由我国东北林区的主要树种制成,并对部分无缺陷木材通过人工加工做成孔洞、腐朽和裂缝试件。检测设备采用德国进口的ARBOTOM应力波测试仪和武汉岩土力学研究所生产的RSM-SY5型超声波检测仪。 本文系统地研究了在不同的树种和不同条件下,应力波和超声波在无缺陷木材和缺陷木材检测中波传播参数和动态弹性模量的不同变化。通过应用SPSS统计软件对检测结果进行比较,主要是通过波在木材中传播参数的相应变化来判断木材内部是否有缺陷以及缺陷的严重程度,同时得出不同因素如:①木材密度;②含水率;③内部孔洞大小;④腐朽程度;⑤节子大小;⑥裂缝深度,对两种波的传播参数及动态弹性模量有不同程度的影响。对比结果表明:两种波在不同的木材特性和木材内部缺陷类型的检测中检测可靠性和应用范围有所不同。超声波对木材密度的变化较敏感,它在对木材内部缺陷类型如腐朽、孔洞和节子的判别中效果比应力波好;应力波受木材含水率的影响较大,它适用于检测尺寸较大的木材内部腐朽和孔洞(如原木)。最后,利用Matlab软件对应力波检测的截面图进行数字图像处理,使木材内部缺陷的形状变得更加清晰。同时,对超声波检测的信号进行了滤波处理,使波形幅值的变化更加明显。通过图形和波形的相应变化来分析木材内部缺陷,进一步提高了木材内部缺陷检测的可靠性。 本文的研究结果为应力波和超声波检测技术在木材及木制构造物的内部缺陷检测中的进一步应用奠定了实践基础。更多还原

【Abstract】 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.更多还原