基于Fourier拟合曲面的X射线焊缝缺陷检测

针对在强噪声、低对比度及复杂背景特征下X射线焊缝图像的缺陷检测问题,提出了去噪处理、焊缝边缘分割及缺陷检测的方法.用快速离散Curvelet变换和循环平移相结合的方法,对焊缝图像进行滤波去噪,同时对图像列灰度曲线用最大类间方差法提取焊缝区域.在图像预处理后,采用三阶Fourier曲线对图像列灰度曲线进行拟合并扩展到三维空间,构造出自适应阈值面,最后利用原图像与构造曲面三维灰度图的灰度值差异,准确分割背景与缺陷区域.结果表明,与传统缺陷检测算法相比,该方法能准确提取出焊缝缺陷,漏检率和误判率低,准确率可达95%.     

基于X射线图像处理的单搭接焊缝缺陷识别

钢板单搭接焊缝区厚度的变化,使其对应的X射线图像灰度连续变化。这给基于图像阈值分割处理的缺陷识别带来困难。为了解决这一问题,文中给出一种基于X射线图像背景去除的缺陷识别方法。首先对待处理的X射线数字化图像进行噪声抑制,并利用模拟图像背景获得前景图像;然后对前景图像进行基于迭代阈值法的图像分割,提取缺陷目标;最后采用数学形态学处理,实现缺陷自动识别。结果表明所提方法能有效识别钢板单搭接焊缝中的气孔缺陷。     

焊缝X射线图像的数学形态学分析

焊接过程中产生的缺陷影响焊缝质量,X射线无损探伤是常用的检测技术手段。针对焊缝X射线图像的缺陷提取问题,提出使用数学形态学分析的技术方案。先用低帽变换处理原始图像,降低背景灰度的同时凸显缺陷区域,然后设置固定阈值分离缺陷区域,最后使用开运算去除干扰,实现缺陷的自动提取。实验结果表明,提出的技术方案合理可行,能够准确分离焊缝X射线图像上的缺陷区域。     

基于有监督过渡区的焊缝X射线图像分割

针对X射线焊缝检测图像中存在大量背景冗余信息,焊缝和缺陷难于准确检测提取的问题,提出一种基于先验知识的有监督过渡区域提取及阈值分割方法.根据焊接图像本身的特点,通过先验知识对样本图像进行训练,确定某个区间来估算图像过渡区域的灰度范围,按照模糊子集理论,给出一种新的加权算子来描述局部窗口内灰度级的变化,从而能充分考虑到局部窗口内灰度级变化的频率和幅度,通过计算过渡区域像素的灰度均值,将其作为阈值对图像进行分割.结果表明,该方法能准确地将目标缺陷从焊缝X射线图像中分割出来,具有良好的适应性.     

基于Faster-RCNN的船舶焊缝X射线缺陷图像检测技术应用

将目标检测网络Faster-RCNN应用在船舶焊缝X射线缺陷图像检测中,探讨了Faster-RCNN在X射线焊缝缺陷检测中的效果。针对船舶工业中的X射线焊缝图像,首先采用CLAHE方法对焊缝X射线图像进行预处理,并将焊缝中存在的气孔、裂纹、未熔合等5种具有典型特征的缺陷作为识别目标进行标注并对数据进行增强。在目标识别上,采用ResNet-50作为主干网络来减少梯度弥散现象提高模型准确率,并针对焊缝缺陷目标小的特点对RPN网络锚点参数进行改进优化,同时引入FPN网络提取缺陷特征。最后与其他检测算法进行对比,试验结果表明,该数据集在模型上的m_AP值达到96.33%,可以满足X射线焊缝缺陷自动化辅助检测要求。     

焊缝X射线胶片数字化图像低对比度细长线缺陷的检测

焊缝X射线数字化图像中像素宽度不超过3个像素的细长线缺陷,其对比度低,常有间断,常规的X射线焊缝缺陷检出算法难以有效检出。针对此类缺陷,提出了在滤波降噪的基础上,采用逐列自适应阈值法对图像中细长线缺陷进行初步分割,然后应用改进的局部霍夫变换剔除初步分割结果中的大量噪点,准确分割出细长线缺陷。试验结果表明,所提出的方法能够适应不同灰度范围的X射线图像、克服噪声及缺陷间断的影响,有效检测出低对比度细长线缺陷。     

基于视觉注意机制的射线图像缺陷检测方法

针对铸件、焊缝等缺陷在复杂背景射线图像中提取准确度较低的情况,提出一种基于视觉注意机制的射线图像缺陷检测方法。根据缺陷的不同性质,将射线图像按照区域或者线段划分成若干子区域;通过模拟视觉注意机制,利用中央-周边差算子分割出可疑区域;设置显著性阈值排除图像其他部分的干扰,并极大减少了算法处理量,然后以阈值法即可准确提取出各类缺陷。实验结果表明:该方法可在复杂背景下的射线图像中准确高效提取出缺陷,准确率可达94.6%,且适应性强、通用性好。     

基于信息融合优化搜索的X射线焊缝缺陷检测

提出一种基于信息融合优化搜索技术的X射线图像焊缝缺陷检测方法.在对X射线焊缝图像进行预处理的基础上,使用垂直焊缝方向投影的波形分析法进行焊缝区域分割,采用图像信息融合技术,综合不同判据获得启发式状态空间优化搜索的启发信息,对搜索过程进行优化,从而快速准确地检测出X射线图像中的缺陷区域.试验结果表明,提出的算法能够快速有效地检测出焊缝X射线图像中的缺陷,取得较好效果.     

一种焊缝X射线数字图像的缺陷提取算法

准确提取焊缝X射线图像中的缺陷是图像自动识别的主要问题。针对这一难题,提出了一种以邻域灰度平方差变换为基础,结合灰度级形态学重构和边缘检测,辅之边缘保持滤波和已标注连接分量图像融合的缺陷提取新算法。该方法能可靠地提取出低对比度X射线数字图像中的焊缝缺陷部分。     

X射线焊缝图像的缺陷检测与识别技术

针对目前无损检测主要采用人工方式存在的主观不一致、检测效率低、操作复杂等问题,设计了一套焊缝缺陷自动检测系统。提出基于Otsu双阈值分割的缺陷区域自动提取、图像的降噪和灰度增强的图像预处理方法;通过SUSAN算法检测焊缝缺陷目标,并结合形态学孔洞填充算法修正缺陷目标;计算焊缝缺陷目标特征参数,并结合所设计的深度为4的二叉树分类识别逻辑流程,实现了较好的焊缝缺陷的检测结果。     

Image segmentation of small defects in precision weldments with complex structure

In this paper, the X-ray nondestructive test method of small defects in precision weldments with complex structure was presented. To resolve the difficulty of defect segmentation in variable grey image, the image processing based on Visual Basic programming method was adopted. The methods of automatic contrast and partial grey stretch were used to enhance the X-ray detection image which has relatively low contrast, then automatic threshold method was carried out to segment the two high intensity zones, and weld zones which contain the small defects was extracted. Smoothing and sharpen processing were proceeded on the extracted weld zones, and small defects in X-ray detection image of weldments with complex structure were segmented by using the method of background subtraction in the end. The effects of raster were eliminated, and because of that the image processing was only proceeded on the extracted weld zones, the calculated speed using the above provided algorithm was improved.     

基于X射线数字化图像处理的双面焊焊缝缺陷检测

对双面焊焊缝的缺陷自动检测,提出了对焊缝重叠区边缘区与非边缘区分别进行处理、非细长缺陷与细长缺陷分别进行处理的思路.在逐列灰度波形分析检出焊缝外边缘和两焊缝重叠区边缘的基础上,对于非细长缺陷,采用大模版中值与均值滤波相结合模拟背景,然后对消除背景后图像采用分区域阈值检出焊缝缺陷,对于细长缺陷,提出了基于逐列自适应二值化和改进霍夫变换的缺陷分割算法.结果表明,所提出的方法能够在有效地避免两焊缝重叠区边缘处误检的同时,检出微弱线缺陷.     

基于FGT-FBP重构算法的焊接缺陷检测

针对焊接过程产生的缺陷,提出一种磁光成像传感的模糊灰度变换和滤波反投影(FGT-FBP)重构检测方法. 研究焊接缺陷的几何特征,通过分析裂纹和未熔合两种不同焊接缺陷在交变磁场励磁下的磁光成像特征,设计模糊规则,对磁光图像进行模糊灰度变换. 增强磁光图像对比度,使焊接缺陷形态趋势可视化,实现描述磁光成像焊接缺陷细节的无参考型图像评估方法. 对FGT处理的焊接缺陷磁光图进行旋转投影,并经过快速傅里叶变换和改进的滤波器进行滤波去噪,消除伪影后进行反投影变换实现焊接缺陷图像的重构. 利用滤波反投影重构算法进行去噪,可有效突出焊接缺陷特征. 最后结合阈值分割和边缘检测实现焊接缺陷检测. 结果表明,该方法能较准确检测裂纹和未熔合两种焊接缺陷.     

Research on segmentation and distribution features of small defects in precision weldments with complex structure

In order to study the segmentation and quantitative problem of small defects in precision weldments with complex structure, an automated image processing system was setup based on the Visual Basic 6.0 development environment. The weld zones were extracted by adopting the method of twice automatic threshold, and the small defects were segmented successfully by using sharpen, smoothing processing and background subtraction in the extracted weld zones. To determine the spatial distribution features of small defects, calculation formula of defects depth and deviation were deduced individually, and the projection distance of small defects can be extracted automatically also. The image processing system can achieve the goal of small defects segmentation and automatic extraction of projection distance. The depth and deviation of small defects can be obtained through the above deduced formula, and the longitudinal distribution of small defects can be obtained from the detection image, then the spatial distribution features of small defects can be determined.     

Flaw detection in radiographic weldment images using morphological watershed segmentation technique

In this paper, the concept of application of morphological multistage watershed segmentation for detection of flaws in radiographic weld images is discussed. It is simple and intuitive and always produces a complete division of the image. The multistage watershed segmentation used here reduces the problem of over segmentation besides generating boundaries with very less deviation from their original position. Two-stage water segmentation is implemented here. At the first stage, watershed transform is applied to an X-ray image and the resultant mosaic image pattern is further thresholded by Otsu's thresholding method and converted into the binary image. Then, morphology and top-hat transformation is applied on binary image to separate partially overlapping objects. Euclidean distance map is calculated for each basin to label resultant segments uniquely and to separate ridges. This follows the second stage of watershed segmentation to obtain better-defined boundaries while removing over-segmented regions. Watershed segmentation algorithm has been able to detect flaws like slag inclusions and wormholes-type weld flaws. It shows all defects with reasonable accuracy having close contours. Similarly, small cavities are also highlighted successfully.     

基于局部曲面重构的焊缝X射线图像缺陷分割技术

背景消除是焊缝X射线自动检测中缺陷分割的常用方法,其核心是焊缝背景图像的获取。由于焊缝的多样性,常用的低通滤波和曲线拟合方法所得到的背景不够准确,造成较多误检率。研究了基于局部曲面重构的背景消除法,先对焊缝列灰度进行分析,获取潜在的缺陷区域,再对该区域进行曲面重构,获得焊缝背景图像。试验表明,该方法可有效减少误检和漏检,并获得良好的焊缝缺陷形貌。