国产涡流检测设备在轧辊磨削及检查中的应用

简述为提高轧辊使用寿命 ,降低生产成本 ,对在役轧辊实施自动检测的重要意义。介绍了上海宝钢益昌薄板有限公司采用的国产涡流自动检测设备的组成和功能。该厂采用该技术后 ,减少了轧辊磨削量 ,避免了爆辊事故 ,取得了较好效果。     

涡流检测与其它探伤方法对轧辊的质量控制

针对轧辊表面缺陷检测方法的选择,以及涡流检测原理和涡流检测时遇到的各种问题,着重分析涡流检测灵敏度设定以及轧辊材质对涡流探伤的影响,并利用其它检测方法来校验涡流的检测结果,对实际缺陷的当量、形状和缺陷的种类进行分析,完成轧辊的质量控制。     

列管式反应器的涡流检测

列管式反应器的泄漏将严重影响化工生产。采用双频涡流方法检测其列管及管板，介绍了检测传感器的设计和制作，分析和研究了缺陷和涡流信号响应特征之问的关系。对比分析了表面凹坑、夹渣及裂纹等缺陷的阻抗图特征。验证了根据阻抗图幅度和相位分析判定缺陷技术的优点。实践表明，涡流检测速度快、灵敏度高且测试结果准确。     

远场涡流检测技术在碳钢管束中的应用

远场涡流检测是一种发展中的钢管检测技术,它可以解决电力石化行业大量使用的碳钢管在役快速检测难题,很有发展前景。针对某化机厂新建的换热器管束,将两种标准相结合,对该管束进行涡流检测,并采用其他方法对部分可疑的管束进行检测,将结果进行对照。应用实例证实了远场涡流检测技术对碳钢管是一种切实可行的快速和可靠的检测方法。     

汽轮机叶片的涡流检测

电厂汽轮机转子叶片是汽轮机关键部件之一 ,其结构完整性是保证汽轮机安全运行的重要因素。汽轮机的定检要求对转子叶片进行原位探伤。以往检验采用着色法 ,灵敏度偏低 ,检测结果受人为因素影响。现在采用涡流检测法 ,在叶片上用电蚀法制作模拟裂纹 ,虽然它与自然疲劳裂纹在阻抗信号的响应上有差别 ,但便于对缺陷尺寸和响应信号之间关系进行定量研究 ,从而确定与实际应用相近的试验参数模式。涡流法应用于汽轮机叶片检测具有灵敏度高、准确直观等优点 ,某动力厂 2号和 3号汽轮机末三级叶片的检测实践证实了该法的优越性 ,收到了良好的效果 ,…     

相控阵超声检测技术在硬质合金轧辊修磨中的应用

根据相控阵超声检测原理,设计硬质合金开槽、刻肋轧辊相控阵超声检测试块,利用此试块,配置特定的探头与相应的楔块,进行相控阵超声检测仪器的调整、检测灵敏度的调试。以开槽、刻肋轧辊的内表面为接触面,采用调试好的仪器对轧辊开槽、刻肋位置进行相控阵超声检测。通过实验验证,利用设计的试块调试检测仪器及检测灵敏度,采用以开槽、刻肋轧辊内表面为检测面,进行40°～70°范围扫描的相控阵超声检测方法能检测轧辊开槽刻肋位置的内部缺陷,能准确判断缺陷的位置,准确指导轧辊修磨工艺参数,误差在0～2 mm。     

涡流检测技术在电厂设备检测中的应用

介绍了常用的几种涡流检测技术在火电厂设备检测中的应用,同时对几种涡流检测技术进行了比较,并指出了目前应用中存在的问题。     

远场涡流检测技术的世界动向

远场涡流(RFEC)检测方法,适用于强磁性厚壁管外表面腐蚀缺陷的检测,管壁厚度的变化与检出信号相位差成比例,管子的外壁缺陷与内部缺陷在检测中具有相同的灵敏度.而常规的涡流检测方法是不具此特点的.近年在美国、加拿大和日本等国家,此技术的实际应用研究开发已成为热门话题.但目前还存在不少理论上的问题没有完全解释清楚,在具体应用技术上也同样存在不少问题.     

涡流检测技术的某些新进展

评述近年来国内外涡流检测技术的发展状态,着得介绍涡流传感器的最新进展及涡流成象技术新动向。     

低频电磁/涡流无损检测技术的研究

介绍利用低频电磁／涡流法检测在役铁磁性铁、管材等部件的原理和初步应用情况。     

主成分分析法在脉冲涡流缺陷识别中的应用

在钢结构脉冲涡流缺陷识别中,通常采用信号的峰值幅度、过零时间、主峰面积等特征参数对缺陷进行表征。但上述参数相互关联,存在一定的信息冗余,增加了数据分析量及信息筛选难度,进而影响了缺陷识别的效率。针对上述问题,采用主成分分析法对脉冲涡流信号的6个特征参数进行降维处理,构造了一个主成分特征,减少了信息冗余;将上述主成分特征输入Logistic分类器,实现了对钢结构减薄缺陷的准确识别。结果表明:主成分分析法可以在确保缺陷识别准确率的情况下,有效减少分类器处理的数据量,提高缺陷识别效率。     

基于数理统计的缺陷涡流检测定量方法

针对涡流阻抗平面显示检测仪器对缺陷大小不能准确定量检测的难题,采用正态分布及一元线性回归分析的数理统计方法,对涡流检测定量方法进行研究,得出了涡流阻抗幅值与缺陷大小的数学规律。经试验验证,定量检测结果良好。     

宝钢支撑辊的使用技术

介绍了宝山钢铁股份有限公司 5套板带轧机的支撑辊使用环境、使用技术和使用水平 ,指出适用的轧辊材质和性能、合理可控的换辊周期、优化的配辊和磨削技术 ,以及完善的无损检测是轧辊使用和维护的关键。并对支撑辊使用技术的发展作了展望     

Thickness measurement of metal pipe using swept-frequency eddy current testing

Swept-frequency eddy current measurement of pipe thickness is studied in this paper. First, suitable frequency range of swept-frequency eddy current testing is determined by comparing sensitivities of relative reactance change with respect to pipe thickness and other parameters at different frequencies. Based on analytical solutions to pipe eddy current field, Levenberg–Marquardt algorithm and variable transformation, a method for solving inverse eddy current problem is developed. Finally, several inversion calculations are carried out and the results are close to the truth values. The low errors reveal that the method presented in this paper is appropriate.     

Structural analysis of CFRP using eddy current methods

Nondestructive inspection of carbon fibre-reinforced plastics (CFRP) using eddy current methods is not only based on the conductivity of the fibres. High frequencies (up to 10 MHz) enable the exploitation of capacitive effects reflecting the properties of the matrix. The paper presents a method using rotating eddy current probes to measure the anisotropic electrical properties. Potential applications of the method are structural identification of laminates and estimation of their degradation. For example, the strength properties of constructions based on unidirectional CFRP are very sensitive to small differences in fibre direction angle. Best detection of these angles could be obtained above 7.5 MHz. In addition, a signal perpendicular to the fibre orientation was found and termed the plateau effect. It is a result of capacitive connections between the fibres and presents new opportunities for the characterization of matrix properties.     

Reduction of lift-off effects for pulsed eddy current NDT

The lift-off effect is commonly known to be one of the main obstacles for effective eddy current NDT testing as it can easily mask defect signals. Pulsed eddy current techniques, which are believed to be potentially rich of information, are also sensitive to the effect. An approach using normalisation and two reference signals to reduce the lift-off problem with pulsed eddy current techniques is proposed. Experimental testing on the proposed technique and results are presented in this report. Results show that significant reduction in the effect has been achieved mainly in metal loss and sub-surface slot inspection. The technique can also be applied for measurement of metal thickness beneath non-conductive coatings, microstructure, strain/stress measurement, where the output is sensitive to the lift-off effect.     

An eddy current array instrument for application on ferritic welds

This paper describes a multi-element, eddy current array for the local testing of ferritic specimens including welds. A novel transient method is used to extract coil impedance parameters, and has the advantage of fast measurement, digital compatibility and a minimum of front-end components; a useful feature when large element numbers are involved. The problem of displaying lift-off and flaw information from an array is solved by using a novel ‘volcano display’, which provides a simple two-dimensional image of conditions under the array. However, to produce this display, the burden of interpreting the coil element responses must be left to the instrument. The resident analysis software contains a number of operating modes which provide options for single element and multi-element operation. The array has been applied to the detection of cracks in the HAZ of a weld, where the large surface area of the probe permits a coarser scanning pattern to be used whilst providing a high probability of detection due to the number of elements deployed.     

Impedance inversion in eddy current testing of layered planar structures via neural networks

The inversion of eddy current probe impedance measurements is widely recognized as a complex theoretical problem whose solution is likely to have a significant impact on the characterization of materials. In this paper the evaluation of the conductivity profile of a layered planar structure is performed after inverting the impedance of a circular air-cored probe coil, of rectangular cross-section, using multilayer perceptron neural networks, trained via the back propagation learning algorithm. The merits of the method are illustrated in the light of two engineering examples.     

宝钢热轧厂轧辊磨床的技术改造

介绍了宝山钢铁股份有限公司热轧厂对其轧辊磨床进行床身导轨、数控系统、测量系统、中心架、砂轮主轴及动平衡装置、集中控制、在线涡流探伤等方面的技术改造情况。改造后，磨床精度、效率和稳定性明显提高。