基于超声线列阵的钢坯孔洞缺陷检测层析成像技术研究

Research on Imaging Detection Technology of Billet Hole Defects Based on Ultrasonic Linear Array

为实现钢坯内部孔洞缺陷的精准检测,提出了一种超声透射层析成像技术与超声线列阵全方位扫描技术相结合的方法。首先,设计了阵列超声检测方案,建立超声波传播路径的层析成像方程,给出求解方式。其次,通过有限元仿真对比分析了钢坯在有无缺陷情况下的走时,验证超声透射法采集缺陷走时信号方法的有效性,接着通过参数化设置实现线列阵扫描功能,将仿真的走时数据通过迭代算法重建横截面的灰度图,然后利用三次样条插值细化、中值滤波及图像增强的处理,分割提取图像中的缺陷,验证了该成像方法的可行性。最后,搭建了实验系统,通过实验进一步验证该方法的有效性。通过仿真和实验发现,采用所提方法重建的缺陷图像不仅形态完整,而且与实际缺陷轮廓对比,计算出相对误差仅为3%左右,分辨率可达1 mm,表明该方法的有效性和优越性。

In order to accurately detect the holes in steel billets,a method combining ultrasonic transmission tomography and ultrasonic line array omni⁃directional scanning is proposed.Firstly,the array ultrasonic detection scheme is designed,the tomographic imaging equation of ultrasonic propagation path is established,and the solution method is given.Secondly,through finite element simulation anal⁃ysis of the billet walking in cases of with and without defects,the validity of the ultrasonic transmission method to collect defect signals is verified.Then,through parametric setting,the function of linear array scanning are analyzed travel time data of simulation is realized,the through iterative algorithm to reconstruct the greyscale image of cross section,and the defects in the image are segmented by using the cubic spline interpolation refinement,median filtering and image enhancement processing,verifying the feasibility of this imaging method.Finally,an experimental system is built to verify the effectiveness of the proposed method.The results of simulation and experi⁃ment show that the reconstructed defect image by using the proposed method is complete in shape,furthermore,compared with the actual defect contour,the calculated relative error is only about 3%,and the resolution can reach 1 mm,which shows the effectiveness and su⁃periority of ththe proposed method.