白桦模拟缺陷材的电阻层析成像规律探究

以白桦圆盘为对象,人工设计各种空洞缺陷,研究电极传感器数量、内部缺陷面积、轮廓形状以及位置等因素在利用电阻层析成像检测缺陷准确性方面的影响。结果表明:电阻层析成像技术可以通过电阻率的分布直观地显示木材内部缺陷,但是其图像显示的缺陷面积和缺陷轮廓受诸多因素影响; 圆形缺陷面积从5.69%上升到40.48%时,电阻层析成像系统显示的缺陷面积与实际缺陷面积的相对误差率从4.14下降到0.02; 增加电极传感器的数量可以提高检测准确率; 缺陷轮廓形状对电阻层析成像有一定的影响,狭长形缺陷容易被检测出来,但近圆形缺陷的面积准确率高; 缺陷位置对电阻层析成像有一定的影响,缺陷面积一定时,边材处的空洞比心材处的空洞更容易被检测出来,而且缺陷面积的准确率也高。
In order to improve the feasibility of wood nondestructive testing methods, electrical resistance tomography as a new and developing technology was chosen for the detection of wood internal defects. Fifteen pieces of artificial discs of Betula platyphylla Sukaczev in total with average diameter of 15 cm and thickness of 5 cm respectively were selected as the experimental samples. With designed varieties of artificial simulating cavity defects, the discs were tested by means of electrical resistance tomography. The different detecting images were acquired from the different detecting conditions. For the investigating and analyzing requirements, different number of sensors, different defect area, defect position, and outlook of simulated cavity defects were used as the detection of defects accuracy for electrical resistance tomography. The results showed that the relative error of graph defect area and real defect area drop from 4.14 to 0.02 with the rate rose from 5.69% to 40.48%. In the case of adjacent sensors without mutual interfered, the increasing numbers of sensors could improve the detection accuracy. Outline shapes of defects have certain effect on detection of defects. Compared with other cavity defect shapes, long and narrow shape defect could be easily detected. On the contrary, the area and outlook of accuracy of circular defect detection accuracy is highest. The defect position also has certain effect on the detection of defects. Within the same defect area, the center of cavity defects located at sapwood could be easier detected with higher detection accuracy than those located at heartwood. Electrical resistance tomography could visually display the internal defects of wood by resistivity distribution, but the precision and outlook of tomographic image are closely related to a wide range of factors, including the number of sensors, defect area, defect position and outlook of simulated cavity defects, all of which would have an effect on accuracy of test results. It is necessary to modify the test results when judge the actual defect with electrical resistance tomography