耐疲劳堆焊焊接缺陷

焊接材料 母材：碳钢 焊材：铁基堆焊材料焊接方法 堆焊耐疲劳堆焊焊接缺陷@郭力力$哈尔滨焊接研究所!150080 @于捷$哈尔滨焊接研究所!150080 @孙秀芳$哈尔滨焊接研究所!150080     

线聚焦超声波法焊接缺陷识别

针对常规超声TOFD(time of flight diffraction,衍射时差)法存在超声衍射声场能量低、检测回波信号弱的问题,提出一种线聚焦超声TOFD焊接缺陷识别方法. 基于几何声学理论,根据所需主轴声线折射角度及聚焦深度,设计线聚焦超声TOFD法所用的声楔块. 通过铝合金板人工缺陷试件的检测,研究线聚焦法的检测灵敏度;通过铝合金板搅拌摩擦焊试件的检测,验证线聚焦法的有效性. 结果表明,和常规方法相比较,相同测试条件下线聚焦超声TOFD法的检测灵敏度更高,采集的图像具有更好的对比度,同时能较好地保持图像边缘. 所提新方法在改善缺陷分辨力、提高缺陷检出率及降低漏检等方面具有很好的使用价值.     

基于时频判别特征的焊缝超声检测缺陷分类

根据超声检测信号的瞬变特性,针对焊缝检测的缺陷分类问题,提出用判别追踪算法提取缺陷信号的局部时频判别特征,并结合概率神经网络实现了焊缝超声检测信号的缺陷分类.在提取时频判别特征时,提出考虑新选原子与已选原子的相关性的判别基提取方案,以降低特征之间的冗余,使提取出的特征能更有效地鉴别不同类别的缺陷.用该方法对一电子束焊缝试块中的缺陷进行了分类,结果表明,时频判别特征适合超声信号的缺陷分类,并能有效地抑制晶粒噪声的影响,考虑判别原子间相关性后可获得更高的分类正确率.     

基于DR数字射线成像技术的铝合金焊缝缺陷检测

利用DR(Digital radiography)数字射线检测方法对不同透照厚度的铝合金焊缝进行射线检测试验,优化管电压、管电流、曝光时间、放大倍数等工艺参数,使其检测灵敏度满足标准要求。在此基础上分别对铝合金熔焊缝和搅拌摩擦焊缝进行数字射线检测和常规胶片射线检测对比试验,获得典型缺陷检测图像,并对缺陷的形貌分布、尺寸、性质等进行了对比分析,分析数字射线检测的缺陷检出能力,验证数字射线检测结果的可靠性。结果表明,数字射线检测灵敏度优于标准要求,且缺陷的检出能力与常规胶片射线检测基本一致,尺寸误差小于5%。     

Weld defect detection using PPM EMAT generated shear horizontal ultrasound

Austenitic welds are inspected using PPM EMAT generated shear horizontal (SH) waves. Results are compared to measurements taken using a 1D piezoelectric phased array using the total focusing method (TFM). For the first time there is clear experimental evidence of the SH wave method demonstrating higher sensitivity to defect detection. SH waves suffer less beam steering in a weld than either compression or SV waves, which can miss defects due to weld microstructure anisotropy and attenuation. All defects were identified from every side of the weld/plate using the SH waves, but this was not possible using the piezoelectric transducer.     

Weld oxide formation on lean duplex stainless steel

Weld oxides have a strong influence on corrosion resistance, but have hitherto only been studied to a limited extent for duplex stainless steels. X-ray photoelectron spectroscopy (XPS) has here been used to study heat tint formed on gas tungsten arc (GTA) welds on the commercial duplex grades LDX 2101 (EN 1.4162/UNS S32101) and 2304 (EN 1.4362/UNS S32304) welded with and without nitrogen additions to the shielding gas. The process of heat tint formation is discussed in terms of transport phenomena to explain the effect of atmosphere, temperature and composition. The oxides formed were found to be enriched in manganese and corrosion testing shows that nitrogen has a strong influence on the weld oxide. A mechanism is proposed including evaporation from the weld pool and subsequent redeposition.     

300 MW高压加热器焊接缺陷分析及质量控制

300MW高压加热器是电站机组中重要的汽水加热设备，在运行中最易出现的质量问题是管端或管系发生泄漏，造成机组停机检修，给电厂造成重大经济损失。除机组运行及管子本身质量因素外，焊接质量是引起高压加热器泄漏的主要原因，根据近年来的质量反馈显示，已投运的300MW高压加热器出现泄漏绝大多数是由于管子与管板连接处的焊缝存在缺陷经给水冲蚀而产生的，因此，有效控制焊接质量，是提高高压加热器使用寿命的有效手段之一。本的目的是通过对管子与管板焊接缺陷的分析，提出改进300MW高压加热器焊接质量的措施，提高产品质量，避免由此引起的管端泄漏等质量问题的发生。     

基于改正二维主成分分析的焊缝表面缺陷检测

机器人焊接因零件形状不规则和焊接工艺复杂不可避免带来各种焊缝缺陷.针对二维主成分分析应用于焊缝表面缺陷检测时面临计算复杂度高、分类准确率低及无法进行增量学习等问题,提出了一种基于均值更新的增量二维主成分分析(mean updated incremental two-dimensional principal compo...     

异质紫铜的TIG焊

我公司施工的昆山某电子工程 ,其设备接地采用2 0多根紫铜管打入地下一定深度 ,然后用紫铜排与紫铜管连接 ,具体见图1。紫铜管的材质为Ｔ2 ,规格为50ｍｍ× 3ｍｍ ;紫铜排的材质为ＴＰ2 ,规格为 4ｍｍ× 4 0ｍｍ。1　焊接性分析由于紫铜的导热系数、线膨胀系数和收缩率都比钢大 ,因此如果采用的焊接规范与焊接同厚度的低碳钢差不多 ,则母材就很难熔化 ,因而使填充金属和母材不能很好熔合 ,故产生焊不透的现象。与此同时还会使焊缝热影响区变宽 ,焊后变形大。因此 ,紫铜焊接时要求较强热源和适当预热。2　焊接工艺2 .1　焊接方法的选择考虑…     

基于改正二维主成分分析的焊缝表面缺陷检测

针对小径管X射线焊缝图像缺陷检测精确率低的现状,通过对图像进行特征分析并结合稀疏字典学习,提出一种基于图像分割的小径管焊缝图像缺陷检测算法. 首先,对小径管焊缝图像进行两步图像分割获得感兴趣区域;其次,提取焊缝缺陷,得到缺陷疑似局部图像;最后,提出以不同类型原子间相关性最小为目标的小径管焊缝缺陷字典矩阵数学模型并使用K-SVD算法进行求解,利用该字典矩阵实现圆形缺陷、线形缺陷和噪声的分类鉴别. 为提高系统实时性,使用并行编程对图像分割算法进行加速. 结果表明,改进后缺陷字典矩阵对圆形缺陷识别成功率为0.974,线形缺陷识别成功率为0.967,且具有较快的识别速度,实现了小径管焊缝图像缺陷的有效识别.

     

摆动电弧窄间隙立向上GMAW焊缝成形

文中对摆动电弧窄间隙立向上GMAW工艺进行了研究.结果表明,窄间隙立向上焊缝表面中间凸起,而立向下焊缝中间下凹;摆动角度和摆动速度的增加均有利于焊缝中间凸起高度的降低,侧壁停留时间对焊缝中间凸起的影响较小;电弧在坡口中间摆动时单位移动轨迹长度上的电弧能量能够影响焊缝中间凸起高度,侧壁停留时的单位移动轨迹长度上的电弧能量则主要影响焊缝熔宽,摆动参数通过影响电弧能量的分布来影响焊缝熔宽和中间凸起高度.     

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B样条曲线的X射线图像焊缝缺陷分割与提取

针对大部分X射线数字图像低对比度、背景起伏大以及纹理复杂的问题,在X射线数字焊缝图像预处理之后,采用B样条曲线对列灰度曲线进行拟合,获得光滑而且顺畅的曲线.在此基础上进一步提取曲线的极值点,并通过定义的波动阈值以及边界阈值进行两次极值点集合的修正.最后利用数学形态学及中值滤波对缺陷的形状和大小进行了修正.结果表明,该技术有效地解决了X射线图像由于焊缝纹理复杂导致缺陷提取困难的问题,有利于实现X射线图像焊接缺陷的自动提取.     

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%.     

高速GMAW驼峰焊道形成过程熔池图像识别

针对高速驼峰焊道形成过程中熔池的变化规律,采用CCD视觉传感系统跟踪采集. 提出了一种基于模糊C-均值聚类(fuzzy C-means,FCM)协作主动轮廓(chan-vese,CV)模型的熔池图像分割方法,对高速焊接过程中的熔池图像进行图像分割. 结果表明,驼峰的形成过程中,熔池长度的阶跃变化是反映驼峰形成的主要图像特征. 将熔池长度序列拟合成波形,采用Symlets2号小波进行分解,发现d₂级小波分解能更好地识别熔池长度的阶跃变化. 对d₂级小波细节能量设定阈值,获取反映熔池长度阶跃变化的尖峰突起特征信号,能很好地识别驼峰缺陷的形成,初步实现了驼峰焊道的监测控制.     

一种铝箔针孔形成机理的探讨

利用光学显微镜、扫描电镜、能谱分析等试验手段对铝箔中"桔瓣"形针孔形成的原因进行了分析.结果表明,铝箔麻面波浪深凹部存在着由K、Cl、Ca等元素组成的化合物;麻面波浪深凹部一般都对应存在着油坑,而有油坑的地方不一定已形成针孔;针孔是在麻面波谷处与光面油坑对应部位穿透而形成的.分析认为,含K、Cl、Ca等元素的化合物的存在增大了麻面粗糙度,从而增加了针孔形成几率;控制双合前轧辊的粗糙度、控制轧制油量、适当进行热处理等均可减少针孔数量.     

Influence of Rotation Rate on Microstructure and Comprehensive Performance of FSWed Mg Alloy

Die-casting AZ31 Mg alloys were successfully friction stir welded at a constant welding speed and different rotation rates. More uniform and fine grains were obtained at the rotation rate of 1400 rpm due to more suitable temperature for dynamic recrystallization in this welding condition. In addition, the intensity of (0001) texture in stir zone increased with the increasing rotation rate. The results of mechanical property test indicated joint with rotation rate of 1400 rpm had better tensile property, which was associated with fine grains, uniform transition in the interface between thermo-mechanically affected zone and stir zone as well as more favorable Schmidt factor for basal slip and twinning. The corrosion resistance of joints increased with the increasing rotation rate, which is significantly related to the (0001) texture with basal plane parallel to the corroded surfaces.     

‘Herringbone’ defect formation in planar-flow melt spinning

A short-wavelength, periodic feature (≈1 mm) similar in appearance to a herringbone pattern appeared on ribbon produced at high rates (≈10 m/s) by the planar-flow process. These marks corresponded to a high-frequency (≈10 kHz) disturbance to the process stream. Observations of herringbone formation came from ribbon profilometry, customized nozzle tests and high-speed meniscus imaging. These observations were compared against observations of the ‘crosswave’ feature formation which were subject to prior study. It is demonstrated here that herringbone marks, in contrast to the crosswave marks, were mainly influenced by the substrate motion of translation. Herringbone formation is also reported to have correlated with the pinning of the liquid puddle at the nozzle edge.     

X-ray images of defect formation in porcelain ceramics during drying

The drying phase during the manufacture of ceramic pieces is often the point of failure owing to the formation of cracks. In this study, non-destructive microfocus X-ray imaging has been employed to study the onset of cracking in porcelain and correlate it with the moisture content. Samples of moist porcelain paste were extruded through dies of 30 and 50 mm diameter. Sections of the extrudate were placed into an X-ray transparent oven and imaged while drying at constant temperature and low humidity. The time to the onset of cracking was found to be a function of temperature. The mode of failure was consistent across the temperature range 40–120 °C.The higher the drying temperature, the shorter the time to failure and the higher the moisture loss at failure. For a particular paste consistency and sample geometry there was found to be a critical moisture content below which cracking began to occur. This moisture threshold was observed to be weakly temperature dependent; it appears to be more sensitive to sample geometry and paste consistency. A safe drying curve has been constructed which provides a boundary for the process parameters which prevent cracking. The implication is that during the drying of a ceramic piece, different sections may have different safe parameter boundaries and the process must be designed to keep all sections within the safe region.