共查询到16条相似文献,搜索用时 484 毫秒
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涡流检测技术对工件表面或近表面的缺陷有很高的检出灵敏度,且检测线圈不需与被测物直接接触,可进行高速检测,易于实现自动化。针对航空发动机涡轮叶片的复杂曲面人工检测难度大、效率低等问题,研制了一套六自由度机器人涡流自动化检测系统,该系统可自行对其工作空间、工作表面和运动学的工作特性进行分析研究;设计了多种典型涡轮叶片专用弹压式涡流检测探头,可自适应叶片形貌及叶片安装误差;开展了涡轮叶片检测自动扫查检测试验,优化了涡流检测的激励频率和自动扫查速度。结果表明:可弹压式涡流探头对叶片表面缺陷可自适应涡轮叶片的复杂表面,提高了自动化检测的精度,同时弥补提离变化和安装误差。当激励频率为1.25~1.75 MHz、扫查速度为30 mm/s时,检测灵敏度较高,能有效检出缺陷。相比于人工涡流检测方法,该自动化检测系统提高了叶片的检测效率。 相似文献
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脉冲涡流检测中由于探头倾斜或被测对象表面不光滑等原因容易产生提离效应,提离效应严重影响着脉冲涡流无损检测的结果。提出了一种基于差分信号二阶微分零时刻值匹配补偿的方法。首先建立相应的提离参考数据库,然后通过索引二阶微分零时刻值匹配提离参考信号,计算补偿比,利用补偿公式对提离效应进行抑制。通过试验发现,经该方法处理后的有提离差分信号能够与无提离的差分信号可以很好的吻合,消除了提离效应对差分信号的影响。试验结果表明了该方法能够对多层金属结构的内部缺陷检测具有较好的提离抑制效果。 相似文献
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为了分析阵列涡流传感器扫查不同位置表面横向裂纹时的线圈输出信号特征,以及焊缝受热区金属材质变化对线圈输出信号的影响,建立铝合金焊缝裂纹的阵列涡流检测的三维有限元模型。结果表明:当裂纹长度分别为1.6、3.0、4.5 mm时,裂纹长度与线圈感应电动势的波峰幅值呈单调递增关系,探头扫查侧面裂纹时的线圈感应信号总是大于正上方裂纹;焊接所引起的5A06铝合金材料电导率减小会使线圈的感应电动势幅值增大,且当裂纹长度分别为1.6、3.0、4.5 mm时,裂纹长度越大,电导率减小在裂纹检测时对线圈输出信号的影响越小。 相似文献
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承压类特种设备在石油化工等行业应用广泛,然而,出于防腐等需要,承压设备外常涂有涂层,给检测带来了难度。针对涡流检测技术在带涂层检测中的应用,提出了一种基于双切向涡流的阵列探头,并对其阵列单元的性能和阵列探头的整体结构进行分析和设计。理论分析表明,所提出的阵列单元可消除激励线圈到接收线圈直接耦合信号的影响,同时,该探头能够同时实现对不同长度和不同角度裂纹的定量分析,进而提高裂纹的检测精度。此外,为减小提离效应对检测结果的影响,设计了带有弹簧的阵列探头结构,弹簧始终处于压缩状态,以保证在检测过程中探头的提离最小,该研究可为带涂层设备的检测提供一定技术支持。 相似文献
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Precision eddy current measurements have been shown to be capable of characterizing the near-surface residual stress and cold work profiles in surface-treated components. To capture the peak compressive residual stress in moderately shot-peened (Almen 4–8 A) nickel-base superalloys, the eddy current inspection frequency has to be as high as 50–80 MHz. Unfortunately, spurious self- and stray-capacitance effects render the complex eddy current coil impedance variation with lift-off, the so-called lift-off curve, highly nonlinear, which makes it difficult to achieve accurate eddy current conductivity measurements beyond 25 MHz in the presence of even the slightest lift-off uncertainties. As opposed to the well-known inductive lift-off effect that decreases with increasing probe size, the capacitive lift-off effect increases with probe size. Both effects increase with frequency with the inductive effect being initially stronger, but then taken over at high frequencies by the faster growing capacitive effect. Since the two effects produce opposite curvature in the lift-off curve, in the frequency range where they are approximately equal to the lift-off curve becomes essentially linear and fairly accurate, conductivity measurements can be conducted even in the presence of lift-off variations. 相似文献
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Measurement of lift-off using the relative variation of magnetic flux in pulsed eddy current testing
Measurement of lift-off can be used to assess the thermal insulation thickness and it has the potential to reduce the lift-off effect in pulsed eddy current testing. In this paper, first, the relative variation of magnetic flux is proposed as a feature for the measurement of lift-off. And then, how to directly obtain the key parameters of the feature from the testing signals is provided. At last, the validity of the feature is verified by simulations and experiments, respectively. The results show that the feature is suitable when the lift-off is tens of millimeters and the plate is ferromagnetic. 相似文献
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脉冲涡流检测技术在带包覆层管道腐蚀缺陷检测中展现出优势而引起广泛关注。本研究设计了一种脉冲涡流聚焦探头,通过有限元仿真与试验,研究其在复杂结构部位中的检测能力。仿真结果显示,设计的脉冲涡流聚焦探头能有效聚集磁场与涡流场能量,有利于对局部缺陷与复杂结构中的缺陷进行检测。通过探究聚焦探头在提离10~50 mm下对管道焊缝及各种尺寸局部缺陷的检测灵敏度,分析其检测能力与提离检测极限,以及在检测过程中的信号特征。结果表明,聚焦探头在提离50 mm下仍能检出尺寸为40 mm×40 mm×1 mm(长×宽×深)的方形局部腐蚀缺陷,焊缝信号的凸起特征、缺陷信号的下凹特征与仿真结果相印证。 相似文献