共查询到19条相似文献,搜索用时 296 毫秒
1.
2.
3.
由于金属构件缺陷各异,损伤部位可能存在多个缺陷,为了实现涡流检测的可靠性评价,建立了合两个矩形槽缺陷的管道二维轴对称有限元模型,计算了信号的相位和幅值。仿真结果表明,多缺陷对涡流信号的影响不同于单一缺陷,且随激励频率不同,阻抗信号偏差不同;而在进行缺陷定量表征时,缺陷的几何状态(深度、宽度、内外壁状况)会对深度较小缺陷的定量表征有影响,引起损伤评价不当,可参考幅值细致分析此影响。 相似文献
4.
核电站蒸汽发生器用690镍基合金传热管在制造过程中至少需进行3次涡流检测,第一次是直管成品时,使用外穿式探头主要检测传热管外壁缺陷;第二次是弯管前,使用内穿式探头主要控制传热管信噪比;第三次是弯管后,使用内穿式探头主要检测传热管内壁缺陷。介绍了3次涡流检测的时机、目的、参数设置、信号分析和验收评定结果。另外通过试验研究了整体消应力热处理对涡流检测的影响,试验结果表明,整体消应力热处理对U形传热管的内涡流检测信号无影响且未产生热处理信号。 相似文献
5.
6.
1 不同的裂纹对涡流线圈阻抗的影响涡流探伤主要检查工件表面和近表面裂纹 ,裂纹对线圈阻抗的影响可视为电导率和几何形状两个参数的综合效应 ,同时 ,裂纹的大小、方向、埋藏深度和裂纹本身宽度的差异 ,对阻抗影响也不同 (图 1 )。下面我们用同种型号的放置式低频反射探头和同种测试程序对表面开口裂纹及不同埋深裂纹进行测试 ,以弄清裂纹在平面阻抗中的显示情况。图 1 不同埋深的裂纹及其阻抗由图可以看出 ,裂纹的长度和宽度恒定时 ,表面裂纹信号最强 ,随着裂纹埋藏深度的不同 ,信号幅度逐渐减少 ,导体中的涡流和表面涡流的相位不同 ,表… 相似文献
7.
8.
9.
在利用外穿过式线圈对不锈钢管件进行涡流检测时,发现深度分别为0.10,0.15和0.20 mm的三种裂纹无法利用检测信号的相位角进行识别。针对这一现象,利用阻抗分析方法进行了计算,得出在不同检测频率下,管件表面从0.10~1.90 mm不同深度裂纹的相位角,以及上述无法区分的三种缺陷的幅值。在此基础上,制作了带有人工缺陷的试样管件并对其进行涡流检测。检测结果表明,根据检测信号幅值的大小,可将深度差异为0.05 mm的人工缺陷区分开,且检测结果稳定可靠。 相似文献
10.
设计有不同深宽比裂纹的2组对比样管,探究阵列涡流对于不同深宽比裂纹的敏感性。使用阵列涡流检测方法,对样管上的缺陷进行检测对比。结果表明:在对裂纹深宽比特征参数研究中发现,当宽度一定、深宽比大于1时,涡流幅值随深宽比增加逐渐变大,深宽比小于1时,涡流幅值与深宽比无明显对应关系;当深度一定、深宽比大于1时,涡流幅值大小随深宽比增加逐渐变大。在宽度相同、深度不同和的深度相同、宽度不同的深宽比研究中发现,深宽比相同时,阵列涡流检测到的模拟裂纹的涡流幅值均随检测频率的增加而逐渐变大。 相似文献
11.
12.
This paper presents a generalized likelihood ratio technique for detection of defect locations from bobbin coil eddy current data. First a Neyman–Pearson (NP) decision rule for detection of known random signals (in presence of noise) is discussed. The result is then generalized to the problem of detection of unknown random signals that are commonly found in bobbin coil eddy current data. The performance of the proposed detection technique is tested on several real world data sets collected from the steam generator tubes of nuclear power plants. The experimental results indicate that the method is quite promising and useful for automated processing and classification of eddy current data. 相似文献
13.
Haoyu Huang Nozomu Sakurai Toshiyuki Takagi Tetsuya Uchimoto 《NDT & E International》2003,36(7):515-522
This paper describes an arrayed multi-coil probe, newly developed for the testing and crack sizing of steam generator tubes by eddy current testing (ECT). The testing speed, the high sensitivity to shallow cracks and the crack sizing are the present requirements in ECT. Because of the multi-coil arrangement, the arrayed probe has a high detection speed around the whole tube, without the need for rotation. It is realized from former studies that knowing the number of cracks, their directions, and their positions beforehand is of great help in crack sizing. Thus, not only the sensitivities but also the spatial resolutions are important. Numerical simulations are applied to help the design of the probe from the viewpoint of the crack sizing of steam generator tubes. Experiments show that the present probe provides both a high detectability and a remarkable capability of reconstructing the shallow cracks of a tube. 相似文献
14.
In this paper, an inversion algorithm for three-dimensional profile reconstruction of wall thinning defect in a double-layer region of a typical coolant pipe of nuclear power plants from pulsed eddy current testing (PECT) signals has been proposed and experimentally validated, based on a fast simulator of PECT signals and a deterministic optimization strategy. First, the fast simulator developed by authors for PECT signal prediction based on a Fourier-series scheme in addition with interpolation and database approaches is briefly described as a base for the inversion of PECT signals. Then, the formula of the conjugate graduate inversion algorithm for sizing three-dimensional wall thinning from PECT signals is deduced in detail based on that for crack like reconstruction using single frequency ECT signals. The three-dimensional local wall thinning is modeled as a group of planar defects with different length and depth which are reconstructed from two-dimensional scanning PECT signals through inverse analysis. Through conducting PECT experiment for double-layer coolant tube test-piece and reconstructing wall thinning profile from the measured signals, the efficiency and the robustness of the proposed inversion algorithm are demonstrated. 相似文献
15.
16.
17.
For defect characterization in steam generator tubes, feature extraction to interpret eddy current testing (ECT) signals has been recognized as an important step. In this paper, we propose a new feature extraction from ECT signals for defect classification and defect sizing. Using the extracted features as an input vector, a multi-layer perceptron (MLP) neural networks are used to classify defect types and to predict defect size. Although the proposed method requires relatively fewer features for the defect classification, it provides not only a high level of classification accuracy but also promising robustness to noise. Moreover, for the prediction of defect size, the proposed method yields a comparable prediction accuracy even though it needs fewer features than the previous result. 相似文献
18.
针对传统的涡流检测激励频率确定方法存在与实际情况不符和难以得到最佳检测频率的问题,基于大型通用有限元软件ANSYS建立了外径19 mm、壁厚2 mm的1Cr18Ni9Ti不锈钢管材涡流检测内插式探头和穿过式探头的仿真模型,根据差动探头的特性,通过计算距人工缺陷不同距离时检测线圈电流的实部IREAL、虚部IIMAG和线圈的阻抗差ΔZ,进而得到缺陷仿真信号,通过比较不同频率下缺陷信号的幅值和相位,确定穿过式探头的最佳检测频率为50 kHz。 相似文献