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Nondestructive Evaluation/Testing: New Technology & Application (FENDT), 2013 Far East Forum on

Date 17-20 June 2013

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Displaying Results 1 - 25 of 49
  • Saturated low frequency eddy current technique applied to microstructure phase quantification in duplex stainless steel

    Page(s): 1 - 7
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (529 KB) |  | HTML iconHTML  

    Duplex stainless steel (DSS) presents a good combination of mechanical properties and high corrosion resistance. Its microstructure is composed of two phases with different physical properties: delta ferrite and gamma austenite. The best properties of DSS for in service applications are achieved when these phases are in equal proportions. However, exposition to high temperatures, may entail undesired consequences impairing the mechanical and corrosion properties of the material. Eddy current testing (ECT) has already been used for DSS inspection and microstructure characterization, mainly to detect the presence of deleterious phases, such as sigma. However, conventional ECT was not able to quantify different amounts of austenite and ferrite in the absence of deleterious phases. The present study focuses on the experimental and computational problem of DSS inspection using ECT in saturated magnetic conditions in order to identify different amounts of austenite and ferrite within the DSS microstructure. Samples containing ferrite to austenite ratio equal to 50/50, 70/30 and 80/20 respectively were brought to saturation as designed in the simulations and the ECT was applied presenting a very good result. Saturated low frequency ECT condition proved to be a reliable methodology in quantifying delta ferrite and gamma austenite phases in DSS. View full abstract»

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  • Applications of approximate wave analysis to ultrasonic flaw imaging

    Page(s): 8 - 11
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (419 KB) |  | HTML iconHTML  

    Two applications of approximate wave analyses to ultrasonic flaw imaging are presented. One is to apply a high frequency approximation for transmitted waves through curved interfaces to improve SAFT images of flaws in a structure with complex geometry. As examples, the improved SAFT is applied to pitch-catch data for flaws in an immersed round bar, and flaw images are compared with conventional SAFT images. Another application is to use a low frequency approximation to reconstruct a flaw shape of 3-D plate thinning from reflection coefficients of ultrasonic guided waves. By introducing a far field expression of Green's functions and Born approximation into the integral expression, a Fourier transform pair is obtained between the shape function of thinning flaw and reflection coefficients of backscattered guided waves. Some numerical examples are illustrated to show the validity and effectiveness of our inverse approach. View full abstract»

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  • Detection and classification of weld defects in industrial radiography with use of advanced AI methods

    Page(s): 12 - 17
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (202 KB) |  | HTML iconHTML  

    The paper presents and shortly discusses the AI algorithms created for automated detection and classification of weld defects on the basis of radiography images. The three approaches are described: with use of fuzzy logic, with use of artificial neural networks and that basing on rough sets theory. The data evaluating the accuracies of obtained classifiers as well as chosen examples are attached. View full abstract»

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  • Efficient analytical modelling for Pulsed Remote Field Eddy Current evaluation of stratified tubular structures

    Page(s): 18 - 22
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (221 KB) |  | HTML iconHTML  

    Stratified Tubular Structures (STSs), such as pipeline, are extensively adopted in such engineering fields as nuclear, petroleum, chemical and aerospace, etc. Wall-thinning Defects (WTDs) are usually found within in-service STSs, and taken as critical flaws which demand to be detected and assessed during STS inspection. It is crucial to non-destructively evaluate the integrity of STSs, particularly WTDs before catastrophic accidents occur. Pulsed Remote Field Eddy Current technique (PRFEC) has been found applicable for evaluation of WTDs in ferromagnetic STSs. In this paper, an efficient analytical model for PRFEC of STSs subject to WTDs is established based on the Extended Truncated Region Eigenfunction Expansion (ETREE). The closed-form expressions of PRFEC responses to WTDs in STSs are formulated. The model is verified by Finite Element Modelling (FEM), and found promising in fast computation of PRFEC signals with high accuracy. The research benefits the inverse problems regarding PRFEC of WTDs in STSs. View full abstract»

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  • Ultrasonic weighted imaging of synthetic aperture focusing technique based on the correlation of signals

    Page(s): 23 - 28
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (155 KB) |  | HTML iconHTML  

    A weighted imaging method of an ultrasonic synthetic aperture focusing technique based on the correlation of signals is presented. The correlation between the ultrasonic echo signals within synthetic aperture range is analyzed, and the distribution of the correlativity coefficient is confirmed to parabolic equation in the region of defect echo waves. The signal amplitude correlativity coefficient is defined to describe the probability of a pixel as a non-noisy pixel. Both the two kinds of correlativity coefficient are used as the weight coefficients of weighted imaging methods. As to effective signals and noise signals, the distribution for correlativity coefficient of echo signals implies the identification of the signals and noises, and amplitude correlativity coefficient implies two different processing methods while dealing with them. Theoretical and experimental results show that weighted imaging method can improve the SNR and the lateral resolution of ultrasonic synthetic aperture imaging. View full abstract»

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  • Electromagnetic system for nondestructive evaluation of train hollow axles

    Page(s): 29 - 34
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (925 KB) |  | HTML iconHTML  

    The structural integrity of train axles is one of the important factors for safety precautions in a railway industry. Most common techniques used nowadays in the railway industry for manual inspection are visual and magnetic particle techniques as well as ultrasound testing. In this paper, a novel system for electromagnetic inspection is proposed to meet the aforementioned requirements. The system consists of two subsystems and transducers dedicated for flux leakage and eddy current method. Results of measurements and evaluation of the transducers are provided. View full abstract»

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  • The study on the nonclassical nonlinear effect of concretes with different mix rate

    Page(s): 35 - 39
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (131 KB) |  | HTML iconHTML  

    The mix rate of concrete has great influence on the strength of concrete. At present, research method on different mix rate of concrete is always mechanical rather than acoustical. Different mix rates have different porosities in concretes and their linear and nonlinear acoustic properties of concrete are also different. In this paper, the porosity, the linear and nonlinear acoustic properties such as sound velocity, harmonics, nonlinear frequency shift of the concrete samples are compared. And we explore the possibility of using the linear and nonlinear parameters to characterize the strength of concrete. View full abstract»

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  • Wheel and axle defect detecting technique using phased array ultrasonic

    Page(s): 40 - 45
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (348 KB)  

    The quality of wheel and axle is especially important for the safety of locomotive and vehicle. When the wheel running at high speed and high load, circumferential and radial cracks occurs on the stress concentration area of wheel rim, wheel disk, bore hole and gear seat, wheel seat, unload groove on axle because of the remnants remaining during the wheel manufacturing process. Phased array ultrasonic NDT technology and related equipment development applied widely in railway NDT area is introduced in this lecture. Based on phased array ultrasonic technology wheel-set NDT comprehensive technical system has been built for high speed train in China, which has a very important practical significant for the safety of train and people's lives. View full abstract»

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  • Reconstruction of deep stress corrosion crack based on a multi-objective optimization evaluation from Eddy Current Testing signals

    Page(s): 46 - 49
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (265 KB) |  | HTML iconHTML  

    Sizing of crack profiles with Eddy Current Testing (ECT) signals often underestimates the depth of Stress Corrosion Cracks (SCCs) because of its complicated geometry and conductivity property. In this paper, a multi-objective optimization strategy is proposed for the multi-frequency ECT inversion to improve the sizing accuracy of a deep SCC. A ε-constraint method is applied to solve the multi-objective optimization in order to fully utilize the information from the measured ECT signals of different frequencies. Reconstruction with simulated ECT signals of SCC is conducted and the results reveal that the proposed strategy is effective to improve the sizing precision of a deep SCC. View full abstract»

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  • MFL inspection defect reconstruction based on self-learning PSO

    Page(s): 50 - 54
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (120 KB) |  | HTML iconHTML  

    As an efficient optimization method, iterative approach plays an important role in the signal inversion of magnetic flux leakage (MFL) technology. Particle swarm optimization (PSO), a new population-based iterative optimization technique, has been applied for many real world problems with promising results. Self-learning particle swarm optimization (SLPSO), a recently proposed variant of PSO, has been proved to have superior performance in diverse global optimization benchmark problems with 100 dimensions or even more. In this paper, as an iterative approach, SLPSO is applied to defect profile reconstruction for magnetic flux leakage inspection. RBFNN is also used as forward model in the SLPSO-based defect reconstruction method. The experimental results show the profiles processed by the SLPSO-based defect reconstruction method are significantly precise. View full abstract»

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  • Sizing of cavity defect in metallic foam from DC potential drop signals with stochastic inversion methods

    Page(s): 55 - 58
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (187 KB) |  | HTML iconHTML  

    This paper focuses on the sizing of cavity defect in metallic foam (MF) from DC potential drop (DCPD) signals with stochastic optimization methods. Reconstruction schemes and numerical examples for reconstruction of the major defect parameters from both simulated and measured DCPD signals are given for the genetic algorithm (GA), the simulated annealing (SA) method, and the tabu search (TS) method respectively. The maximum reconstruction errors are 5.25% for the SA method with numerical signals, and 10.0% for the TS method with experimental signals, while the errors between the signals of MFs with defect of true parameters (or the experimental signals) and reconstructed parameters are small. This means that taking the potential drop signals of the nodes at the midline of the upper surface or the midlines of both the upper surface and the front surface is feasible to reconstruct the major parameters of single cavity defect with these stochastic methods. In addition, the numerical results suggest that the GA is the most efficient one among the selected stochastic inversion methods in terms of both accuracy and robustness, and the SA method is more time-saving. View full abstract»

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  • Simulation on quantitative analysis of crack inspection by using eddy current stimulated thermography

    Page(s): 59 - 64
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (347 KB) |  | HTML iconHTML  

    Eddy current (EC) stimulated thermography has been proven to be an emerging integrative nondestructive approach for detecting and characterizing surface and subsurface cracks. In this paper, numerical simulation study has been conducted to understand EC stimulated thermography for defect inspection on metallic sample. It has been investigated that transient EC distribution and heating propagation for cracks with different lengths and depths. The simulations are carried out by using AC/DC module of COMSOL mul-tiphysics software. Image processing technique is proposed to analyze the thermal images obtained during the heating and cooling period of the inspection process. The proposed approach is proved to be capable of tracking the heat diffusion by processing the images sequentially. Understanding of transient EC distribution and heating propagation is the fundamental of quantitative nondestructive evaluation of crack inspection with EC stimulated thermography. View full abstract»

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  • Ultrasonic inspection of complex composites

    Page(s): 65 - 68
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (439 KB) |  | HTML iconHTML  

    Complex composites are widely used in aerospace, automobile industry and other fields. Because parts of complex surface to be detected are usually parts with variable thickness. After analyzing the disadvantages of current testing method, an improved real-time sensitivity adjusting method based on stable amplitude is presented. Part curvatures (convex and concave) have a significant effect on both the ultrasonic response and the scanning resolution requirements. In order to ensure more ultrasonic signals transmitted through composites, transducer should always automatically follow the changing shape of curved surface. A twin-robot testing system is introduced to accomplish testing complex surface automatically. Moreover, the experimental results of testing different complex composites supported the opinion above. View full abstract»

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  • Thermal reliability evaluation of PLCC packaging using scanning acoustic microscopy

    Page(s): 69 - 72
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (183 KB) |  | HTML iconHTML  

    Scanning acoustic microscopy (SAM) has emerged as a powerful non-destructive testing tool for microelectronic packaging testing. Under cyclical thermal loads, the microelectronic packaging is easy to produce cracks, delamination, and other defects, which can be detected using SAM. In order to study the thermal reliability of Plastic Leaded Chip Carrier (PLCC) packaging, a set of practical SAM system was developed; Then, thermal cycling test on a set of PLCC packaging was conducted according to the MIL-STD-883H Microcircuits Test Method Standard with temperature range from -65°C to 150°C. and the crack growth rate of PLCC packaging was studied experimentally using SAM. Finally, the Coffin-Manson's constitutive model was adopted to predict thermal fatigue life, which was consistent with the experimental results. With these researches, the thermal reliability of the PLCC packaging was investigated using scanning acoustic microscopy combined with accelerated thermal cycling methods. View full abstract»

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  • Benchmark of residual stress for ultrasonic nondestructive testing

    Page(s): 73 - 76
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (140 KB) |  | HTML iconHTML  

    Based on acoustoelasticsticity theory, critically refracted longitudinal (LCR) wave was used to detect the residual stress in X70 steel. The method of fabrication and calibration for residual stress reference block was introduced and the detecting error brought by environmental temperature changes was corrected. The theoretical equation about the effect of temperature on residual stress detecting was analyzed. Low/high temperature test chambers and ultrasonic residual stress detecting equipment was used to detect the change of ultrasonic transit time difference, which caused by the temperature change. MATLAB second order polynomial was used to fit the experimental detecting results and fitted equation was obtained. The fitted equation was compensated to the system by software programming. The change of residual stress in reference block in two situations was compared. The results showed that temperature change had a large impact on the accuracy of ultrasonic residual stress detecting. The error of residual stress detecting can be effectively reduced by the temperature compensation modules. As result, the absolute precision of detection reaches ±10MPa. View full abstract»

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  • Time delay estimation via third-order cumulant

    Page(s): 77 - 81
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (410 KB) |  | HTML iconHTML  

    Time-delay is a very significant measurement in the field of non-destructive test. The accuracy of time-delay estimation (TDE) directly influences the precision and reliability of the relative measurement method used in non-destructive testing, such as leak location in underground pipeline leak test, ultrasonic blood velocity measurement, ultrasonic material stress measurement etc. In this paper, methods based on third-order cumulant are applied, including Cross Third-order Cumulant Method and Bispectrum Method, to ultrasonic time delay estimation. Higher-order cumulant can effectively suppress big noise interference. According to the principle that the third moment sequence of a zero-mean Gaussian process is identical to zero, we can use third-order cumulant to estimate time delay. Comparing with Generalized Cross-correlation Method, these methods can suppress the effect of correlated Gaussian noise sources and can be used as the substitution of Generalized Cross-correlation Method. View full abstract»

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  • Immersion ultrasonic reflection tomography by annular array system

    Page(s): 82 - 89
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (554 KB)  

    Ultrasonic reflection tomography has been proposed for tumor detection in medical care, multiphase flow imaging and material flaw detection in industrial processing. It is a better way than transmission tomography to reconstruct the target shape when the target or the inner component of the target would bring about severe attenuation for ultrasonic propagation. This paper provides the simulation and experimental results of immersion ultrasonic reflection tomography through ellipse algorithm. By reconstruct a series of priori circle targets, the influences of different target locations, different data quantities and different target sizes on the reconstruction image qualities are discussed while the interaction relationships between the 3 influencing factors and detection sensitizing zone of the annular array system are also demonstrated. From the simulation results, annular array system with 80 transducers that is shown in this paper could attain the detection resolution less than 500 μm. An immersion annular array with 16 elements is proposed in this experiment and the ultrasonic transducers which are ring arranged are served as both transmitters and receivers in order to acquire all the data of the sample from 360 degree in the imaginary plane of the ultrasonic beams. The target measured by the real system is a 7 mm radius ceramic sphere, demonstrating the image reconstruction ability with limited data by ellipse algorithm. View full abstract»

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  • Plate components ultrasonic guide wave detection based on the transducer array

    Page(s): 90 - 96
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (354 KB) |  | HTML iconHTML  

    Aluminum plate components has been widely used in the practical industrial applications, because of the plate's defects, a lot of major accidents occurred and caused significant economic loss. Therefore, based on the fundamental theory of the guide wave that propagating in the aluminum plate, and by solving and analyzing the guide wave's dispersion, the guide wave's inspiring method have been obtained from the wave-mode conversion. Using the wavelet to process the testing signal, and introducing the ellipse localization imaging algorithm to identify the defect's orientation, the defect's localization and orientation can be detected accurately. Based on the theory and technique previous statement, a multi-channel ultrasonic transducer array detecting system including hardware and software has been established, and a series of experiments have been done. The results shows that: the multi-channel ultrasonic detecting system established has a high detection precision in defect's localization and orientation detecting, which is up to 98%. View full abstract»

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  • Single channel blind source separation for defect identification using Eddy Current Pulsed Thermography

    Page(s): 97 - 101
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (419 KB) |  | HTML iconHTML  

    A single channel blind source separation is proposed to process the Eddy Current Pulsed Thermography (ECPT) image sequences. The proposed method enables the detection automatically extract valuable spatial and time patterns according to the whole transient response behavior without any training knowledge. In addition, it has the potential to automatically identify defect patterns and quantify the defects. In this study, both mathematical and physical models are discussed and linked. The basis of the selection of separated spatial and time patterns is also presented. In addition, a natural crack is applied to validate the proposed method. View full abstract»

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  • Eddy current imaging techniques for NDT&E applications

    Page(s): 102 - 106
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (220 KB) |  | HTML iconHTML  

    Eddy current nondestructive tests are important and widely used within the field of nondestructive evaluation (NDE). The recent advances in sensing technology, hardware and software development dedicated to imaging and image processing methods. At the same time, the development of the material further expanded the application fields and made the potential of electromagnetic NDE imaging seemingly unlimited. This paper provides a comprehensive summary of research works on magneto-optic imaging and eddy current thermography for NDE applications, followed by the summary and discussions on future directions. View full abstract»

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  • Experimental study of alternating current stress measurement under a uniaxial stress

    Page(s): 107 - 111
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (217 KB) |  | HTML iconHTML  

    The alternating current stress measurement (ACSM) which is developed from alternating current field measurement(ACFM) is a new and effective electromagnetic non-destructive testing method with greatly application potential for stress measurement. Using this technology to detect the magnetic field disturbance on the specimen caused by the stress can realize the assessment for the degree of stress concentration. In the present paper, the relationship of stress and induced magnetic field was studied by tensile experiments of 20# low carbon steel. Experiment results which are extremely valuable show when the tensile force is less than the yield strength of the specimen, the percentage change of testing signal in the vertical direction of stress can be up to 8% and higher than that in the parallel direction. When the tensile force increases from 0kN to 40 kN, which can exceed the yield strength, the percentage change of testing signal in the vertical direction increases dramatically and can be up to 26%, while that in the parallel direction can be up to 23% too, which can effectively detect the degree of stress concentration of the ferromagnetic specimen. Meanwhile, a mathematical model of the relationship between stress and induced magnetic field was builded under the external magnetic field according to the principle of ferromagnetics, which can provide a reasonable interpretation for experiments. View full abstract»

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  • R & D to electromagnetic NDT in the German nuclear safety research program — Material characterization of ageing phenomena and online monitoring of fatigue and fracture-mechanical tests

    Page(s): 112 - 117
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (453 KB)  

    Obviously it is a fact: The nuclear energy technology worldwide was and still is an important driver for the development of NDT/NDE. This is true in Germany too. Concerning the most relevant task of NDT - detection, classification, and sizing of material irregularities (inhomogeneity, defects) the development of NDT technologies and methodologies like UT and imaging with phased array transducers or defect reconstruction algorithms like SAFT (synthetic aperture focusing technique) or ET of steam generator heat exchanger tubes with eddy current probes and multi-frequency approaches primarily were in the focus of R&D. However, in Germany there was also a strong demand to develop NDT for characterizing the materials of the nuclear components in their properties. The basic idea was to have NDT technology available for inservice inspection of primary circuit components which can characterize the microstructure as well as load-induced and residual stresses. The characterizing should be performed in terms of mechanical properties as hardness, strength like yield and tensile strength but also toughness properties like Charpy energy and fracture appearance transition temperature. Beginning in 1976 the 3MA Methodology (Micromagnetic, Multiparameter, Microstructure and Stress Analysis) was developed. 3MA has its basis in micromagnetic NDT techniques which are the measurement of magnetic Barkhausen noise, of the magnetic incremental permeability, of the eddy current impedance, the harmonic analysis of the magnetic tangential field strength, and the measurement of the dynamic or also called incremental magnetostriction. All of these techniques ask for a local magnetization in a hysteresis loop of the material under inspection and therefore 3MA can only be applied at ferromagnetic materials. The techniques collect information which is generated by interaction of Bloch walls with microstructural parameters (lattice defects as vacancies, dissolved atoms, dislocations, precipit- tions, grain and phase boundaries as well as stress fields). The magnetization processes utilized are reversible and irreversible. Therefore the information collected is divers and redundant which helps to enhance the statistical significance for prediction and tu suppress disturbance influences. 3MA was applied to characterize aging phenomena in pressure vessel and pipeline steels as thermal ageing and neutron degradation as well as material states when thermal ageing and low cycle fatigue were superimposed. In the case of characterizing material states of austenitic stainless steels it strongly depends on the chemical composition whether the material - for instance when exposed to mechanical static or cyclic loads - reacts localized with phase transformation to bcc α' martensite or not. The phase-transformed microstructure is ferromagnetic and therefore 3MA techniques can be applied. In all other cases UT is applied and - for instance a time-of-flight-measurement - is the tool to characterize cyclic deformation. When the mechanical loading is at elevated temperatures (300°C) EMAT are applied. Monitoring of mechanical-technological destructive tests by NDT technology can significantly enhance the information content. Fatigue as well as fracture mechanical tests were on-line monitored. View full abstract»

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  • Study on the railway wheel ultrasonic inspection method using the full matrix capture

    Page(s): 118 - 124
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (325 KB) |  | HTML iconHTML  

    The quality of wheel is especially important for the safety of high speed railway. In this paper, a new ultrasonic array inspection method, the Full Matrix Capture (FMC) and Total Focus Method (TFM) algorithm, has been studied and applied to the high speed railway wheel inspection, especially in the wheel web from the tread. The Total Focusing Method (TFM) which processing image with the data set captured by the approach of Full Matrix Capture (FMC) has been adopted in the field of industrial non-destructive evaluation from medical field since 2005. In this paper, the model is introduced to discuss the principle of FMC and the signal processing method of Hilbert transform which to solve the analytic signal to recover the instantaneous phase information for high resolution imaging. Then the TFM as the reconstruction algorithm is discussed and simulated with different size of aperture to evaluate the performance of TFM. The experiments on the PA block and railway wheel are carried out based on the conventional Phased Array (PA) and FMC method. The inspection result, such as the reliable detection, SNR and image resolution, has been analyzed and discussed according to the different active aperture size based the TFM algorithm, comparison to the conventional phased array UT. It is demonstrated that this TFM algorithm is with good potential for the wheel inspection. View full abstract»

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  • A voltage-current method of measuring ultrasonic transducer impedance

    Page(s): 125 - 128
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (252 KB) |  | HTML iconHTML  

    Impedance is one of the most important characteristics of ultrasonic transducer. This paper focuses on the measurement method of ultrasonic transducer impedance, studying many methods mentioned in domestic and international standard. The voltage-current method is proposed in this paper. What's more, a measurement system based on this method is constructed. Then lots of experiments are performed to prove this method. The result is compared with that measured by using the impedance analyzer, which proves that the voltage-current method can measure the transducer impedance correctly. View full abstract»

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  • Ultrasoud detection based on confocal Fabry-Perot interferometer

    Page(s): 129 - 134
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (329 KB) |  | HTML iconHTML  

    Laser ultrasonic technology has been paid more and more attention in the NDT field due to its outstanding ability of non-contact measurements. As a good vibration measurement technology, CFPI (confocal Fabry-Perot interferometer) method is sensitive to the laser frequency shift caused by the ultrasonic wave propagation. In this paper, a laser ultrasonic receiver system based on the CFPI method is established, and the system parameters are analyzed in order to obtain an optimal resolution. Also some initial experiment results are presented to certify this system ability. View full abstract»

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