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Full-Skip TFM(FSTFM)是在全聚焦成像技术(TFM)的基础上发展起来的一种超声相控阵后处理成像技术. 文中分别采用TFM,FSTFM这两种算法分别对典型的对接焊缝模拟试件中的上表面微小裂纹(垂直表面扩展,深度约1 mm)进行了成像检测. 结果表明,在TFM的成像中,无法观察到裂纹的存在;而在FSTFM的成像中,裂纹的根部和尖端成像清晰可见. 同时根据FSTFM的成像结果,测量出裂纹的扩展深度,且具有较小的误差. 另外,文中通过试验验证了FSTFM对于有余高的对接焊缝的上表面微小裂纹的成像检测同样适用. 相似文献
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利用全聚焦相控阵成像技术对焊缝中的未熔合和裂纹两种典型缺陷进行了检测。首先,介绍了全聚焦成像技术的基本原理;其次,设计制作了含上述缺陷的人工试块,利用CIVA软件进行裂纹和未熔合的缺陷响应研究;接着,对人工试块进行检测试验,比较了常规相控阵技术和全聚焦技术对上述两种缺陷的检测能力;最后,对试块进行常规无损检测,确定焊缝中缺陷的长度,对试块缺陷部位进行解剖,测量得到真实的缺陷埋藏深度和自身高度。检测试验及解剖结果表明:全聚焦技术对上述两种缺陷的成像具有更高的检测分辨率,对缺陷的定位和定量误差较小,可以应用于工程实践。 相似文献
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全聚焦技术是一种基于全矩阵采集的虚拟聚焦图像后处理技术,全聚焦算法将成像区域分割为多个网格,对每一网格都进行聚焦,使得超声成像结果更加均匀平滑,成像质量优于常规相控阵超声检测方法的质量。根据全聚焦成像的技术特点开展管道环焊缝相控阵超声全聚焦检测工艺方案的研究,参照管道环焊缝试块设计标准设计并制作全聚焦验证试块,针对全聚焦验证试块、全自动超声检测(AUT)校准试块开展相控阵超声全聚焦检测试验。试验结果表明,对于V型坡口,全聚焦成像效果好;对于小角度的自动焊坡口,常规全聚焦检测时接收超声回波困难,存在检测灵敏度低的问题;通过对全聚焦算法的优化改进,提高了小角度缺陷的检出率,证明全自动焊焊缝可采用全聚焦技术进行检测。 相似文献
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全聚焦法(TFM)是用后处理算法增强的超声技术.基于全矩阵捕获(FMC)采集数据,由TFM生成的图像几乎聚焦在每个像素上,因而能提高缺陷检出率,改善缺陷定量和表征技术.本文评析焊缝检测中某些方向性面型缺陷引起的信号波幅变化,并对此与其他技术——超声相控阵检测(PAUT)、射线检测(RT)和金相检测结果作了比较.强调声传... 相似文献
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研究多模式全聚焦方法对钢板对接焊缝内部不同倾斜角度缺陷的定量能力。以矩形刻槽代表焊缝内的条状缺陷,采用有限元方法获取刻槽单频散射系数,同时与波传播模型结合进行全矩阵数据模拟,对倾角不同的刻槽进行仿真成像。结果表明,LL-L,TT-T,TT-L等3种半跨模式可覆盖0°~40°倾角的缺陷,TL-LT,LL-LL,TL-TL,TT-TL,TT-LL等5种全跨模式可覆盖10°~70°倾角的缺陷,对缺陷角度表征能力最佳,应在实际检测中优先考虑。另外,刻槽长度定量易受散射强度影响,用同一阈值进行定量识别并不适合全部模式。 相似文献
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航空金属薄板在加工时由于夹杂产生的气孔会随着使用过程中的拉伸和挤压而形成一种闭合型的分层缺陷。针对此类缺陷的检测,提出一种相控阵全聚焦成像算法与兰姆波检测结合的方法。首先从原理上分析并确定激励兰姆波的模态、频率及楔块的角度,其次对3 mm厚度不锈钢板中不同规格、形状的分层缺陷进行试验。结果表明:本研究方法能够对分层缺陷的轮廓成像;兰姆波易受缺陷上端面反射影响,导致缺陷下端面成像出现拖尾图像,且缺陷上端的定位定量精度要高于缺陷下端面;上端面缺陷的定位误差均在4%以内。 相似文献
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随着现代工业的迅速发展,人们对工业无损检测定量分析的要求也越来越严格。本文针对板中缺陷检测的问题在频域合成孔径算法理论的基础上,通过多物理场仿真软件COMSOL Multiphysics进行数值模拟,将仿真得到的A扫数据导入MATLAB软件中进行相位迁移算法处理,得到了二维缺陷重构图像,将50张引入阈值为0.3后的二维缺陷重构图像进行叠加得到了三维缺陷重构图。由缺陷重构结果可知,经过相位迁移算法处理后缺陷中心位置与仿真模型中预设位置X轴坐标相对误差范围为2%~2.5%,Y轴坐标相对误差范围为0%~2%。 相似文献
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A manual inspection of large-diameter tubular joints is difficult. As a result a scanner with three degrees of freedom (DOFs) was developed based on the scanning principle of ultrasonic phased array. The weld tracing is realized by a 2D0F motion of scanner. The pose of ultrasonic probe is controlled by the third one. The control strategy is put forward based on a programmable multi-axis controller. Four kinds of scanning modes can be implemented simultaneously employing this ultrasonic inspection system. Experiments on reference blocks of tubular joints reveal that the automatic ultrasonic phased array inspection system has the same inspection accuracy as a manual ultrasonic inspection. This system is superior to the manual ultrasonic system in terms of reliability and repeatability. The artificial defects of weld at tubular joint can be detected accurately with the presented inspection system. 相似文献
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Zhou Zhenfeng Zhang Xiaoying Guan Liyuan Zhou Gang Wu Shanli Jilin University of Technology Changchun 《中国焊接》1992,(2)
Nickel-iron type cast iron electrodes are widely used for weldingQT600-3 nodular iron.Nevertheless,the research work has demonstrated thatthe strength of these heterogeneous welded joints is low.In this paper,the uni-axial tension of the joints is studied by the Moire fringe method,and the dis-placement,strain and stress in the total fields are obtaind.Based on the unevendistribution of strain and stress,the reason of crack initiation and propagation isdiscussed.Through examining the appearance of the fracture by scanning elec-tron microscope,a lot of spherical substances distributed on the fracture surfaceare found,which may be another reason leading to cracking of the welded jointunder the lower tensile stress.These new findings will help to improve theproperties of nickel-iron type cast iron electrodes and the strength of the weldedjoint. 相似文献
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The method for the determination of the geometrical dimensions and area of the welded joint using a computer program to increase the quality and productivity of the process is described. 相似文献
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The fractal dimension of the fusion line in different dissimilar welded joints is measured with Box Dimension Method.The non-scale region of the fusi on line with fractal character is calculated. The fusion line in the dissimilar welded joint is proved to be a fractal structure. The change and influence factors of the fractal dimension of the fusion line are studied. 相似文献
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The non-destructive testing of brazed joint in honeycomb structure with thin panel ( thickness : 0. 2 mm) was studied by ultrasonic C-scan method. Samples with different types of artificial defect were designed; the characteristic signal and the main parameters of the test were determined by the pre-experiment, and then parameters were optimized by orthogonal design, finally the optimum process was verified by a single panel sample. The multiple reflection echoes were chosen as the characteristic signal. The optimal C-scan results were achieved when the 20 MHz focus probe was used, and the pass band range for received signal were selected as 8 - 17. 5 MHz. The defects such as incomplete penetration and core damage can be detected with ultrasonic C-scan, and the detection accuracy can reach to 1 ram. 相似文献
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文中对超声冲击处理前后的7A52铝合金焊接接头显微组织、显微硬度以及残余应力进行了分析,并对超声冲击处理前后的接头在不同循环应力比的加载条件下进行了疲劳试验.结果表明,经超声冲击处理后接头塑性变形层厚度在45~70 μm左右,母材区表面硬度提高了170%,焊缝区硬度提高了大约70%,改变了焊态残余应力分布,成功引入了压应力;在疲劳试验中,循环次数为2×106的条件下,加载应力循环比为0.1时,冲击态接头的疲劳强度为60.26 MPa,比疲劳强度为40.74 MPa的焊态试样提高了47.9%,而在加载应力循环比为0.45时,冲击态接头的疲劳强度为46.53 MPa,比疲劳强度为39.97 MPa的焊态试样提高了16.4%. 相似文献
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以沸水堆堆芯围板焊接热影响区应力腐蚀开裂为例进行了裂纹扩展评估研究.采用有限元模拟与试验检测数据验证相结合的方法对焊接热影响区焊接残余应力场及应力腐蚀开裂扩展过程进行模拟.通过有限元方法计算了应力腐蚀开裂裂纹尖端应力强度因子,再根据应力腐蚀裂纹扩展试验数据获得裂纹尖端应力强度因子与裂纹扩展速率的关系,最终预测了沸水堆堆芯围板的使用寿命,解决了重大构件基于应力腐蚀开裂失效的安全评估问题.该研究过程为重大构件的腐蚀疲劳裂纹失效的安全使用提供了可借鉴的方法. 相似文献