Attenuation Tomography Of Living Trees Internal Decay Based On Ultrasonic Wave

Timber non-destructive testing (NDT) technology gradually rises after the age of 60 in the 20th century. This technology is mainly used in the testing of growth characteristics of timber as well as physical properties, mechanical properties and detects of timber and timber components.The current majority testing methods of living trees quality are still in qualitative or semi-quantitative level, it is difficult to give quantitative results. Therefore, considering inherent limitations of testing methods, this paper introduces the ultrasonic-wave attenuation tomography (UAT) technology to quality testing of logs. This method means images can be accurately and completely reflect the internal structure of chromatography surface, and has obvious advantages compared with traditional method. Experimental study is carried out on ray tracing, inversion algorithm, velocity inversion and identify detects of attenuation inversion, in order to CT technology has a better application in log non-destructive testing. The cross section of sample tree is tested using the Arbotom stress-wave testing system, and the system gives two-dimensional (2D) images. According to 2D images, we can find out the cross sections of sample trees that meet the requirements. And then considering these cross sections as similar to standard circular, even selecting six testing points in the circumference, using RSM-SYS intelligent ultrasonic-wave testing instrument that produced by Wuhan Institute of Rock and Soil Mechanics in carrying out transverse testing of cross section, and 30 ultrasonic signals are received. The formatting signal is taken de-noising processing adopting wthcoef function of wavelet analysis of MATLAB software for improving the accuracy of interpretation of data, as data-processing capacity of ultrasonic testing system is limited. Finally, attenuation imaging data is extracted.This paper mainly studies the algorithm of application of ultrasonic CT tomography for Living trees internal tomography. The ray tracing algorithm is introduced to tomography algorithm in view of refraction, diffraction and other phenomena that occurs in spread of ultrasound in the Living trees, and ultrasonic-ray distance matrix is taken applying C language program based on beeline tracing algorithm. Then coefficient matrix c and travel-time matrix t are come out using the MATLAB matrix calculation method based on distance matrix.The data from ultrasonic testing for the Living trees has characteristics of incompletion, interference factors and large error. This article adopts SIRT algorithm for image reconstruction, to obtain the equation of amplitude attenuation method, increased attenuation method and travel-time imaging method. Finally,2D images of attenuation imaging and travel-time imaging are obtained by numerical simulation, and compare with 2D images of Arbotom stress-wave testing system, the results showed that the proposed testing method and reconstruction algorithm for ultrasonic attenuation tomography for Living trees is feasible, and achieve a good image reconstruction results.