Modernizing the Echo Method of Ultrasonic Flaw Detection

Russian Journal of Nondestructive Testing - WE consider a modernization of the echo method of ultrasonic flaw detection that uses one or several receiving transducers on the object’s lateral...     

Experimental Testing of the Variational Procedure for Constructing Multidimensional Radio Images of Echo Signals in Non-Emitting Radars

This paper describes the results of experimental approbation of a computationally efficient procedure for constructing multidimensional (in the “angular direction — delay — Doppler frequency shift” coordinates) radio images of target echo signals by a variational method in radar complexes with extraneous illumination.     

Computer Simulation of Echo Signals from a Lateral Cylindrical Hole

The pulsed signal of a slanted transducer, reflected from a lateral cylindrical hole, has been calculated by means of computer simulation. The calculations confirm the results of the earlier investigations and explain certain effects observed.     

Wavelet Filtering of Signals from Ultrasonic Flaw Detector

The paper considers basic principles of the algorithm of wavelet filtering of signals from an ultrasonic aw detector with the help of the fast wavelet transform. Criteria for selection of the type and order of a wavelet are formulated, and the number of decomposition levels required for the needed accuracy and reproducibility of results of ultrasonic tests are determined.     

超声缺陷回波信号的小波包降噪及特征提取

根据非稳态超声检测信号的特点，将小波包变换用于缺陷信号的降噪及特征提取问题的研究，并利用类别可分性判据和RBF神经网络分别对特征值提取结果进行评价。引入了平均阈值的概念，在此基础上研究了小波包降噪效果。提出了以选取小波包分解频带的能量作为缺陷信号特征值的方法。实际焊接缺陷的实验结果表明，小波包降噪效果明显；在特征数据得以压缩的同时，分类的可分性较高。     

超声信号的特征提取与选择在缺陷分类识别中的应用

超声缺陷回波信号的特征提取与选择是超声波检测的基础和关键。结合待检测超声信号的特点,在时域、频域上研究了超声缺陷信号的特征提取,提出SBS和SFS结合的特征选择方法。在满足识别准确率的同时,有效地降低了分类器输入向量的维数,提高了运算效率。     

小波变换在超声探伤仪检测回波处理中的应用

超声检测时探伤仪的电噪声和被检粗晶材料的散射噪声严重影响检测回波的信噪比。研究小波变换软阈值去噪方法在超声检测回波处理中的应用。在分析仪器电噪声、材料散射噪声和缺陷回波的小波变换特性的基础上，提出一种用一个尺度问变化的门限阀值来抑制噪声回波的小波变换系数再重构检测回波的方法提高信噪比。距离一波幅一当量曲线测定实验结果表明，该方法具有很好的去噪效果，处理后的回波损失小，能保证超声探伤的定量准确性。     

Time-Frequency Analysis of Impact Echo Signals of Grouting Defects in Tunnels

Russian Journal of Nondestructive Testing - Abstract—Defects in the grouting layer are hidden problems of underground engineering quality, while it plays an important role in the stability of...     

声学故障诊断中的宽带相关噪声信号分离方法

为了提取混合噪声中待诊设备的噪声信号，利用传声器组构造线性测量阵列流型，建立多声源机器系统的宽带相关噪声混合模型。使用聚集变换技术消除频率对参数估计的影响，并同时消除相关信号功率谱矩阵的奇异性，采用宽带相关MUSIC法估计噪声方差与声源方位，从混合信号频谱中分离噪声源信号频谱。该方法可减小其他噪声源信号的干扰，提高待检设备噪声信号的信噪比。实验结果验证了模型与算法的可行性。     

基于小波包分析的超声缺陷信号特征提取

提取超声缺陷信号的特征是超声缺陷识别的重要关键技术之一,它直接影响着缺陷识别的准确性和可靠性.在分析超声检测信号特征的基础上,采用小波包分析来提取信号的特征信息,其基本思想是选取适当的小波基函数对信号进行小波包变换,提取各个频带上的能量构成特征向量,并用基于距离的类别可分性判据对提取结果进行了评价,可分性测度平均值高达97.7%.试验结果表明,该方法对于超声缺陷回波信号的特征提取非常有效.     

Deep Learning Techniques for Flaw Characterization in Weld Pieces from Ultrasonic Signals

Russian Journal of Nondestructive Testing - Computer aided Interpretation of Ultrasonic signals depicting flaws in weld pieces is depicted in this work. In this work, feasibility of Long Short Term...     

Applying Compression Recognition Method to Achieve Superresolution of Echo Signals

Russian Journal of Nondestructive Testing - The possibility of using the method of compressive sensing (CS) to increase the resolution of echo signals is investigated. For comparison with the CS...     

新型传感器的开发与应用

本文综述了检测复合材料损伤的新型传感器的构思与开发，介绍了有关传感器的应用，并展望了传感器的发展方向     

Calculation of the Spectral Function of Magnetic Field due to a Surface Flaw and Reconstruction of Magnetic Field due to a Flaw of Corresponding Dimensions in a Ferromagnetic Plate

The spectral function of the magnetic field generated by a flaw in a ferromagnetic plate has been calculated, and feasibility of reconstructing magnetic field due to a flaw on the other side of the plate has been demonstrated.     

Application of a Double Scanning Method in Ultrasonic Nondestructive Testing to Improve the Quality of Flaw Images

An algorithm for obtaining flaw images by a double scanning method for application in ultrasonic nondestructive testing, in which a radiator and a receiver move independently along parallel straight lines, is considered. A formula for reconstruction of flaw images is presented. The advantages and drawbacks of the double scanning method are discussed in comparison with the method of projection in the spectral space (PSS), which is also used for a coherent reconstruction of flaw images. The efficiency of the double scanning technique in suppressing the phantom images produced by transformed and rescattered pulses is shown in numerical and model experiments. The immunity of this method to the distortions introduced by an irregular measurement surface and the higher noise immunity compared to the PSS method are also demonstrated.     

Finite-Difference Time Domain Method. Calculating Echo Signals in Homogeneous Isotropic Materials

The method of finite differences in time domain (FDTD) can be used to calculate echo signals in numerical ultrasonic-inspection experiments. As the FDTD method is based on the explicit numerical solution of the wave equation for elastic medium, it can be used to take account of the emergence of a run round wave on a bulk reflector, the effects of a longitudinal wave transforming into a lateral one in the scattering of ultrasound on a crack, and rescattering of pulses between reflectors and test object boundaries. Numerical solution of the vector wave equation by the FDTD method, in contrast to the modelling methods based on the theory of ray tubes, enables a more accurate modeling of ultrasonic inspection results. In this article, three options are considered for suppressing pulse reflections from computational grid boundaries. Calculating the direct problem of the propagation of elastic vibrations through a solid body by the FDTD method may prove useful when solving the inverse coefficient problem of nondestructive ultrasonic inspection.     

钢丝绳弱磁探伤数值模拟及实验研究

在对绞线钢丝绳3D建模的基础上,采用有限元技术,分析了弱磁励磁状态下,钢丝绳复杂表面的磁场分布;对钢丝绳周围空气中的漏磁场矢量进行了仿真,研究了缺陷对钢丝绳表面及空间漏磁场分布的影响。仿真分析结果表明:在无缺陷状态下,钢丝绳周边空气中的漏磁场分布与其绳股形状相对应,其圆周方向的漏磁场呈周期性变化,周期为绳股节距;当缺陷存在时,漏磁场分布的周期性被破坏,且幅值大幅增加。依据理论分析结果,搭建了基于弱磁励磁的钢丝绳无损探伤实验平台,得到了不同断丝缺陷的漏磁场实测波形,实验结果验证了仿真分析结果的正确性。     

超声相控阵在管道缺陷检测中的优化设计

本文采用具有电子偏转及电子聚焦特性的超声相控阵技术对大口径长输管道环焊缝进行缺陷检测,克服传统无损检测由于焦点固定引起检测过程复杂的不足.相控阵换能器的声场特性决定探伤灵敏度,是换能器设计的主要依据.所以需要对超声相控阵换能器进行优化设计,其目的是研究阵元参数与声场特性之间的关系,尽可能地使主瓣尖锐,抑制栅瓣的产生,减弱旁瓣的幅度.本文首先采用数值分析方法,研究并仿真线阵参数对超声束聚焦性能的影响.然后介绍用超声相控阵换能器进行环焊缝检测的试验平台.在此基础上,选取优化后的超声相控阵探头与一个同频的常规超声探头进行对比试验.试验结果表明了该方法的有效性,能提高相控阵换能器的性能.     

基于瞬时频率熵的超声缺陷检测

根据超声无损检测中缺陷和噪声反射回波的瞬时频率的差别，提出利用超声信号瞬时频率在一移动窗内熵的信息，估计缺陷的时频位置。瞬时频率熵方法使得用Wigner—Ville分布表示超声信号时，既能利用Wigner—Ville分布的重要性质，又能实现缺陷的准确定位。对仿真数据和实际探伤数据的实验结果分析表明，瞬时频率熵方法不仅能够识别单个缺陷，也能有效地检测多个缺陷。     

Determination of Welded Joint Flaw Dimensions on the Basis of Scanned X-Ray Images

A method of calculating the depth of incomplete fusion of a welded joint root on the basis of its X-ray image is outlined. The results of approbation of the method using artificial and natural flaws are given.