Ultrasonic testing of railheads using the electromagnetic-acoustic method

Theoretical and experimental studies of the mirror-shadow ultrasonic testing of railheads using the electromagnetic-acoustic (EMA) method have been performed, and schemes and facilities for this technique have been developed. The main factors affecting the results of tests are determined. The tolerable limits of the changes in the tested parameters are established. It has been shown experimentally that the EMA method is highly sensitive in detecting flaws of technological origin in the railhead bulk, which do not produce echo signals with sufficiently high amplitudes.Translated from Defektoskopiya, Vol. 40, No. 7, 2004, pp. 17–25.Original Russian Text Copyright © 2004 by Sebko, Suchkov, Malakhov     

锻件侧壁干涉对超声检测结果的影响

1　前言超声波检测压力容器锻件 ,声束入射到工件边界 ,超声波在工件界面反射并发生波形转换 ,由此会产生超声波的叠加和干涉 ,使原主声束的指向性、灵敏度受到影响 ,因此超声波检测压力容器锻件近侧壁缺陷时 ,定量、定位、定性不准确 ,容易出现漏检和误判 ,对产品质量有很大影响。目前国内锻件超声波检测标准对这一问题还没有具体的规定和要求 ,本文就此提出压力容器锻件超声波检测新工艺 ,实践证明 ,此工艺能有效解决锻件近侧壁缺陷的检出及缺陷定量定性分析等问题 ,避免漏检和误判。　　 2　理论分析纵波探伤时 ,探头若靠近工件边缘 ,则…     

Automatic Detection of Spills and Gas Pockets upon Ultrasonic Checking of Welds in Zirconium Fuel Claddings

The problem of automating detection of flaws (gas pockets and spills) in welds obtained by electron-beam welding, using the ultrasonic echo method which is implemented by slanted introduction of ultrasonic waves into a thin zirconium fuel shell, is considered. Algorithms for automatic detection of flaws and evaluation of their relative dimensions are proposed. Experimental results confirming the efficiency of the algorithms proposed are reported.     

Application of the double-scanning method in ultrasonic nondestructive testing of metals for reconstruction of model defect images

The results of application of the double-scanning method for obtaining images of model defects during ultrasonic flaw detection in metals are presented. It has been shown in model experiments that, during reconstruction of flaw images, the amplitudes of parasitic reflections formed by echo signals, which were transformed and repeatedly scattered by inhomogeneities, decrease considerably. These properties of the double-scanning method may be useful in the practice of ultrasonic inspection of heavily loaded objects, especially in the case of the pressing problem of classifying the detected flaws. To identify the type of defects and determine their number accurately, it is desirable to use images obtained in both the double-scanning and transceiver modes. The images obtained during operation of a transducer in these two modes are compared.     

汽车纵梁冲压裂纹检测系统干扰信号的研究

在使用涡流探伤器对汽车纵梁冲压裂纹检测时,会产生振动等干扰因素,从而产生提离干扰信号,干扰了缺陷信号的识别,致使漏检或误检。因此,对干扰信号进行的研究,并设法区分和抑制,是提高涡流探伤可靠性的关键。     

金属材料超声探伤缺陷分类辅助系统的研究

针对在目前工业生产的超声检测中缺陷难以定性的问题,在现有缺陷信号处理和人工神经网络分类研究工作的基础上,基于虚拟仪器的设计思想及功能模块化的设计方法,采用PC机和数据采集卡作为硬件系统,在L abV IEW平台上建立了能对缺陷进行智能识别的系统——金属材料超声探伤缺陷分类辅助系统。系统具有采集金属材料中缺陷回波数据、降噪、特征提取和智能识别缺陷等主要功能。实验结果表明,该系统基本上能自动识别出各类缺陷。     

A nonlinear effect-based ultrasonic flaw detector for detecting cracks

The operation of an ultrasonic flaw detector using a nonlinear modulation method of crack detection that is suitable for effectively testing cracks in wafers is considered. It differs from analogues in the technique of modulation of elastic characteristics of flaws, namely, a sequence of phase-inverted pulses of Lamb waves. The results of testing of an ultrasonic flaw detector intended for detecting model flaws (single cracks and cavities) in wafers are presented.     

Attempt Towards the Replacement of Radiography with Phased Array Ultrasonic Testing of Steel Plate Welded Joints Performed on Bridges and Other Applications

This study was carried out to demonstrate if the phased array ultrasonic testing (PAUT) can be adopted as a suitable substitute of the radiography testing (RT) of steel plate’s welded joints required by codes and standards related to some projects such as bridges construction and inspection according to AWS D1.5 Bridge welding code. Such adoption, if approved, can realize considerable cost saving without taking any additional risk. The two cited inspection techniques had been applied to test four butt welded joints performed on steel plates having thicknesses up to 35 mm. These welded joints had been performed by shielded metal arc welding (SMAW) and containing selected artificial flaws. The comparison between the detection capabilities and characterization of flaws in the welded joints by the two inspection techniques reveals that; PAUT improves the detection capability and sizing of flaws in the welded joints and it can replace RT reliably in case of applying a suitable PAUT procedure that includes simultaneous application of sectorial scan from both sides of the welded joints axes by using encoder with wide active aperture phased array probes and applying supplemental manual scanning for edge testing.     

A modulation crack-detection technique: I. Instrumental method of implementation

The results of the development of a nonlinear modulation technique for diagnosing materials and structures containing flaws, which are characterized by linear (cavities) and nonlinear (cracks) acoustic properties, are presented. This technique is based on the modulation of the acoustic characteristics of flaws with low-frequency bending vibrations of an object that are accompanied by simultaneous coherent pulsed ultrasonic location of flaws. The pulsed location mode is used to determine the coordinates of a flaw, while the presence or absence of modulation of the received ultrasonic pulses allows the following problems to be solved: identification of the type of a flaw (a cavity or crack), detection of closed isolated cracks, and identification of the presence of cracks (microcracks) at early stages of their development. The literature on this measurement technique is reviewed. Specific features of measurements and two possible (hardware and software) methods for implementing this technique are discussed. The results of detecting cracks in model (metal plates) and real (pipeline fragments) objects via an instrumental technique are presented.     

海底管道缺陷检测线聚焦超声传感器阵列设计

在对线聚焦超声传感器声场进行数值模拟和实际测试的基础上，设计了用于海底管道缺陷自动检测的线聚焦超声传感器阵列。用该阵列对样管中的缺陷进行了实际检测。测试结果表明，该阵列对管道中的轴向裂纹有很好的榆出率。通过对测试信号进行分析，发现信号经二级自适应滤波去噪后，可得到更好的检出效果。     

聚乙烯管道电熔焊接接头的超声检测

聚乙烯管连接中大量使用电熔接头,其质量的好坏直接影响管道系统的安全。分析了超声聚焦检测技术对聚乙烯管电熔接头各类缺陷的检出能力。在此基础上,运用相控阵超声技术及B扫描实时成像超声方法检测大量含缺陷接头,对比超声成像图与接头实剖图,发现该方法有较高的检测灵敏度和检出精度,可以应用于工程实践。     

Shape reconstruction of mixed type void flaws using Born inversion method

We study an approximate technique for determining the shapes of mixed type void flaws in elastic media from knowledge of the ultrasonic scattering amplitudes. It is well known that the technique is highly effective under weak scattering conditions. In the paper, two cement paste cylindrical specimens with mixed type void flaws are prepared and ultrasonic measurements are carried out by experimental means. The measurement area is restricted in the plane perpendicular to the axis of cylindrical specimen. The measured wave data are fed into the approximate technique formula—the Born inversion method and cross-sectional image is obtained. We find that good results have been obtained for strong scattering void flaws such as mixed type void flaws in cement paste cylindrical specimens.     

On the Possibility of Using Ultrasonic Surface and Head Waves in Nondestructive Quality Checks of Additive Manufactured Products

The possibilities and limitations of applying head and surface waves to ultrasonic inspection of articles manufactured by selective laser alloying are considered. The optimum angles have been determined for the generation of head and surface waves in a product made of the domestic EP648 powder. The peculiarities of revealing crack-like flaws by the ultrasonic echo method are demonstrated.     

Noise suppression and flaw detection of ultrasonic signals via empirical mode decomposition

In ultrasonic nondestructive testing, the precise detection of flaw echoes buried in backscattering noise caused by highly scattering materials is a problem of great importance. In this paper, a new signal decomposition method for analyzing nonstationary or nonlinear data, empirical mode decomposition, is proposed to deal with ultrasonic signals. A new denoising technique that combines empirical mode decomposition and filtering simultaneously in the time domain and frequency domain is designed to suppress noise and enhance flaw signals. Synthetic and experimental signals are denoised with this EMD-based filtering technique. Simulated results are presented and analyzed, showing that the proposed technique has an excellent performance even when the signal-to-noise ratio is very low (−23 dB). The improvement in flaw detection was experimentally verified on a pipeline sample with artificial flaws. The text was submitted by the authors in English.     

Determining the probability of detecting flaws in weld joints by phased-array ultrasonic testing

The article is devoted to ultrasonic testing of weld joints in aerospace industry with an acoustic phased array. Testing planar flaws of lack-of-fusion and joint-root-crack types by sector scanning is considered. A technique is suggested for calculating the probability of detecting flaws (POD) by means of numerical modeling of the ultrasonic-testing procedure with allowance for interferences. A finite-element model has been developed, and 40 cracks with randomly generated geometry have been modeled. Using the modeling results, a conditional crack height at a level of 10% of the echosignal amplitude from a reference reflector has been determined. POD curves have been calculated using the results of numerical experiments.     

Evaluating Efficiency of Nondestructive Detection of Flaws in Concrete

Tests have been performed to assess feasibility of using the impact-echo method (IEM) and ultrasonic pulse velocity method (UPVM) in detecting flaws and evaluating their depths on the early stage of a concrete structure's service life. Five reinforced concrete (RC) slabs of grades 25, 30, 40, and 50 with fabricated voids at known locations were studied on the 3rd, 7th, 14th, and 28th day. The results were compared to estimate the accuracy of both methods and their efficiency. Both methods detected flaws in the tested samples on the early stages of their operation. Depth measurements of flaws by IEM, however, are more accurate. Results of our tests indicate that both methods can be used in determining depths of flaws in concrete and in performing on-site tests. The accuracy of both methods proved to be better in tests of stronger concretes, and the detection probability ranged from 51.81 to 99.8% after aging during 3 to 28 days under full load, respectively.     

Applying the Algorithm of Calculation in the Frequency Domain to Ultrasonic Tomography

Applying ultrasonic-tomography systems makes it possible to precisely determine the shape and dimensions of flaws with the aim of establishing the degree to which the flaws influence safe operation of tested objects. This problem is solved by using special algorithms that make use of echo-signals recorded by an ultrasonic transducer to generate synthesized images of flaws in the sample. The use of phased arrays in ultrasonic tomography is explained by their ability to provide exhaustive data about the internal structure of a test object, thus allowing formation of the high-quality synthesized images of flaws in the object. Increasing the speed of ultrasonic tomography by using phased arrays necessitates the development and implementation of fast data-processing algorithms. In this connection, of interest are calculation algorithms in the frequency domain, which ensure the high speed of producing synthesized images. An ultrasonic-tomography algorithm is proposed that is based on calculations in the frequency domain. The algorithm takes the complex nature of the propagation of ultrasonic waves into account and is connected with the presence of media with different acoustic properties (e.g., in the case of immersion tests). Possibilities offered by the algorithm are investigated by computer simulations using the licensed CIVA 2016 software package and experimentally.     

Peculiarities of ultrasonic pulsed immersion testing of blanks of railway axles

Research has been conducted and methods have been developed for revealing small-sized flaws in blanks of railway axles by ultrasonic immersion testing technique. It has been established that the use of probing pulse packets significantly improves the sensitivity of testing.     

Ultrasonic Multichannel Flaw Detector for Testing Rails with Signal Recording

Although automated testing instruments have been introduced intensely on the railways of Russia, up to 95% of hazardous flaws in rails are detected by ultrasonic two-line (removable) flaw detectors. The paper describes the functional diagram and basic functions of an ultrasonic detector of the new generation, AVIKON-01, with continuous recording of data. The instrument is supplied with the software package for analysis of testing results, and it has advantages of both hand-held removable flaw detectors and high-performance instruments for nondestructive testing of rails.     

SAFT imaging of flaws in the rail base blade with consideration of multiple reflections of an ultrasonic pulse from the boundaries of a test object

The possibility of obtaining images of type-69 flaws in blades of the railroad rail base is considered. For this purpose, a modification of the SAFT algorithm is proposed, in which, during the calculation of echo-signal delays, multiple reflections of an ultrasonic pulse from the rail boundaries are taken into account. The Fermat principle is used to calculate the delay times. Typical acoustic schemes, each of which can be used to obtain partial flaw images, are determined. Combining the partial images in a final image allows the detection of type-69 flaws. It is shown that the proposed algorithm can be applied for obtaining type-69 images in P65 railroad rails.