脉冲涡流和电磁声换能器双探头无损检测

在许多情况下，只应用一种NDT技术存在不足，这就迫使NDT操作人员使用一种以上的技术以保证检测出危害被检物使用寿命或功能的缺陷。但分别实施多种技术的检测，就会延长检验时间。介绍了一种新的NDT设施，采用两种不同的非接触无损检测技术进行互补，即电磁声换能器（EMAT）和脉冲涡流（PEC）探头。检测结果表明，脉冲涡流和电磁声换能器因是非接触，所以可应用于材料生产过程中的自动在线检验，也可用于在役检验。     

A new non-contacting non-destructive testing method for defect detection in concrete

A new non-destructive testing (NDT) method for defect detection in concrete structures is presented. The method is based on the dynamic response of flawed concrete structures subjected to impact loading. Conversely to similar NDT techniques, such as the impact-echo method, the present method uses non-contacting devices for both impact generation (a shock tube producing shock waves) and response monitoring (laser vibrometers measuring concrete surface velocity). Experimental and numerical (finite element) studies have been carried out for concrete specimens containing artificial defects (penny-shaped cracks parallel to the free surface) with varying length and depth. According to the experimental and numerical results, it appears that the present method enables an effective detection of defects, particularly in the range of shallow defects.     

A hybrid nondestructive testing method of pulsed eddy current testing and electromagnetic acoustic transducer techniques for simultaneous surface and volumetric defects inspection

In this paper, a hybrid nondestructive testing (NDT) method combining with the pulsed eddy current testing (PECT) method and the electromagnetic acoustic transducer (EMAT) method has been proposed and validated through numerical simulations and experiments. First, a numerical code is developed for the simulation of hybrid EMAT/PECT signals based on the developed EMAT and PECT code. Second, based on the numerical simulation, the influences of the eddy current induced by the excitation coil and the eddy current due to the velocity effect of the ultrasonic wave are compared and analyzed. In addition, the features of the EMAT and the PECT signals are analyzed respectively. Third, several signal separation and extraction methods are proposed on the basis of the spectral analysis and filtering strategies for extracting EMAT and PECT signals from the mixed signals of the hybrid EMAT/PECT method and their validity are evaluated through experiments. Finally, hybrid EMAT/PECT experiments are conducted and three types of defects (surface defects, bottom thinning defects, composite defects) in an aluminum plate and a SUS304 plate are successfully detected at the same time using the proposed hybrid NDT method and the signal feature parameters. Based on the numerical and experimental results, the proposed hybrid PECT/EMAT NDT method is demonstrated both high detectability and high efficiency for detecting surface and volumetric defects at the same time.     

A new NDT method based on permanent magnetic field perturbation

On the basis of permanent magnet, perpendicular oriented to the surface of the component under inspection and surrounded by a pick-up coil, the so-called PMFP-effect (permanent magnetic field perturbation-effect) can be observed when the magnet is moved in this perpendicular position with a well defined lift-off along the surface and a surface-breaking or near-surface – but hidden – defect is coming into the influence range of the magnetic field. A new NDT (nondestructive testing) technique by using PMFP so can be proposed for the first time, and its detection mechanism is presented and analyzed by simulations. Afterwards, its testing characteristics for defects are given and its feasibility is further confirmed by experiments. Meantime and particularly, its inspection depth and the effect of the position and attitude of PMFP sensors on inspection signals are analyzed. Accordingly, a multi-differential method used for improving signal-to-noise rate is presented and some testing apparatus using PMFP method is developed. Finally, the proposed PMFP method is discussed specially compared to MFL in detail.     

Relation between mechanical microhardness and impedance variations in eddy current testing

According to the state of the art, eddy current testing (EC) has a strong application in defect detection. The sensitivity to characterize defects and other parameters can be improved by an optimal choice of probes and operation frequency.The work discussed here is a study to materials microstructure characterization and especially the heat affected zones (HAZ) near welds using eddy current techniques.These zones are sometimes brittle and characterized by a microstructure gradient. The aim of this work is to study by eddy current the behavior of such cases. For each damage mechanism, the authors have prepared series of samples. These specimens were tested using NDT methods based on magnetic and electric properties.Electric conductive material samples were made of Aluminum and steel and heated at different temperatures with variable exposure times.The aluminum samples were then exposed to corrosion using an electrochemical process.The applied NDT methods can characterize grain size changes, microstructure types, micro structural changes, hardness changes after thermal treatment.The objective of our work is to detect some metallurgical characteristics by non-destructive methods. The characterization of the microstructure modifications by eddy currents allows detecting mechanical and metallurgical parameters of materials.     

胶接接头的无损检测

保证胶接质量的最好办法是严格控制接头制作过程中的各个环节。简要论述胶接接头的无损检测；介绍几种有前景的接头性能评价的无损检测方法。现有的大多数无损检测方法是针对缺陷的，目前对胶接接头粘附性能和内聚性能的无损检测与评价仍无稳定可靠的方法。     

Evaluation of chloride contamination in concrete using electromagnetic non-destructive testing methods

We present the results of the sensitivity of some electromagnetic non-destructive testing (NDT) methods to chloride contamination. The NDT methods are resistivity, using a quadripole probe, capacitive technique, with few sets of electrodes, and radar technique, using different bistatic configurations. A laboratory study was carried out involving three different concretes with different water to cement ratios. The concretes were conditioned with different degrees of NaCl saturation by means of three solutions containing 0 g/L, 30 g/l or 120 g/l. The solution was homogenized in the concrete by using a specific procedure. Results show that the EM techniques are very sensitive to the chloride content and saturation rate and, on a second level, to the porosity. Multi-linear regression processing was performed to estimate the level of sensitivity of the NDT measurements to the three indicators. Values of ten ND observables are presented and discussed. At last, the uncertainties of the regression models are studied on a real structure in a tidal zone.     

Characterisation of defects in the railhead using ultrasonic surface waves

The ability to detect defects in rail, and in particular surface defects such as gauge corner cracking, is essential. Current ultrasonic testing of the rail uses contacting transducers in a send-receive mode which are at present limited in testing speed to around 20–30 mph, and signals from serious surface defects may be masked by nearby shallow surface defects. Using Rayleigh-like surface waves generated and detected in a pitch-catch manner we can overcome the effect of this masking, and by using electro-magnetic acoustic transducers (EMATs) working at a small standoff we may be able to lift many of the current rail testing speed limitations with a high accuracy for detecting and gauging surface defects. We present experiments on rail samples with real and machined defects, using EMATs to generate and detect a low-frequency wide-band surface wave. The depths of the defects can be characterised through analysis of both the time domain signal amplitude and frequency dependent behaviour. The design of EMAT used is discussed, with consideration of signal, frequency content, directionality of the signal and the effect of standoff above the sample.     

金属管道表面缺陷微波无损检测

对微波技术应用于工业管道表面缺陷的无损检测进行了试验研究,分别进行压力管道内、外表面的微波无损检测试验。试验结果表明：利用微波无损检测技术一方面能实现管道外表面的非接触检测;另一方面能实现管道内表面缺陷的快速定位与测定,大大提高了管道内表面缺陷的检测效率,为金属管道表面缺陷的定位修复和安全评估提供了重要依据。     

脉冲涡流阵列缺陷成像检测技术

脉冲涡流阵列系统具有大面积、快速检测的优点,可用于金属表面裂纹的自动在线检测。在无损检测领域,应用成像技术可以直观地观测到被检测物体的缺陷位置及大小,提高检测人员的工作效率,促进无损检测技术的应用普及。设计了一套脉冲涡流阵列检测系统,包括脉冲涡流阵列探头。应用该系统对标准铝合金试件的缺陷进行了初步的成像处理,给出了标准铝合金试块缺陷成像检测结果,并指出今后的工作方向。     

NDT techniques for railroad wheel and gauge corner inspection

The development of non-destructive techniques (NDT) techniques for the in-service inspection of railroad wheels and gauge corners was the main activity of the NDT division VIII. 4 at BAM over the last 2 years. For such different components, two different inspection techniques were fundamentally chosen in order to fulfil the end-user requirements. Firstly the inspection of the wheels—rim and disk—should be carried out without dismantling the wheels and using ultrasonic techniques. On the other hand, the inspection of the railroad track surface at a train speed of about 70 km/h should be guaranteed using eddy current techniques. The above-mentioned tasks were a challenge for the lab staff. The accessibility for the wheel inspection was limited due to several impassable barriers such as sand tubes, etc. Eddy current application focused mainly on the detection of head check defects occurring at the gauge corner of the rail. Investigations carried out also showed, that other types of surface defects (e.g. Belgrospis, wheel burns, short-pitch corrugations, etc.) could easily be detected. Some aspects of the inspection system as well as an overview of test results are presented in the current contribution.     

厚壁筒形件内表面径向缺陷超声波检测灵敏度试验

对厚壁筒形件进行周向超声检测时,超声波对内表面径向缺陷的检测灵敏度受到多种因素的影响。在研究厚壁筒形件内表面裂纹周向超声检测的主要技术难点的基础上,系统地分析了纯横波技术、双重波型检测法、小角度纵波切内壁法、变型横波端角反射法、变型横波切内壁法等方法的技术特点。通过理论分析提出上述方法的内表面径向缺陷回波波高公式。对含有人工表面缺陷的对比试块进行了灵敏度试验,并对试验结果进行了分析与探讨。     

Artificial disbonds for calibration of transient thermography inspection of thermal barrier coating systems

Transient thermography is commonly used for the detection of disbonds in thermal barrier coatings (TBC). As for other NDT techniques, reference test specimens are required for calibration, but unfortunately, real disbonds are very difficult to use because it is difficult to control their size, and large ones tend to spall. Flat bottomed holes are commonly used, but these over-estimate the thermal contrast obtained for a defect of a given diameter. This paper quantifies the differences in thermal response using finite element analysis validated by experiments, and proposes a form of artificial disbond that gives a better representation of the thermal responses seen with real defects. Real disbonds tend to have a non-uniform gap between the disbonded surfaces across the defect, and the effect of this on the thermal response is evaluated using finite element simulations. It is shown that the effect can be compensated for by adjusting the diameter of the calibration defect compared to the real defect.     

压力容器无损检测--超高压容器的无损检测技术

超高压容器广泛运用在化学、石化、人造水晶、合成金刚石、等静压处理、超高静液压挤压、粉末冶金、金属成型、地球物理和地质力学等行业或领域。在其制造、使用过程中,无损检测是保证产品质量和保证安全使用的有效手段之一。由于超高压容器一般为锻造的厚壁筒体结构,制造过程中的无损检测以超声检测、磁粉检测和渗透检测为主。在用超高压容器的无损检测以表面检测为主,方法有工业内窥镜检查、磁粉检测、渗透检测、磁记忆检测和涡流检测等。超声检测既要检测部件内部又要兼顾内表面缺陷的检测。在容器使用过程中可用声发射进行实时监测。     

涡流脉冲热像与长脉冲光热像对铝板中亚表面缺陷检测的对比研究

作为两种新兴的无损检测与评估技术,涡流脉冲热像和长脉冲光热像已广泛应用于多种场合。针对两种技术检测铝平板类结构中存在的亚表面缺陷,开展试验对比研究。在利用主成分分析和K-means聚类实现增强和提取缺陷信息的基础上,定量对比两种热像技术检测不同尺寸人工平底洞缺陷的性能。试验结果表明,涡流脉冲热像和长脉冲光热像分别能从18个缺陷中检测出14个和12个。此外,涡流脉冲热像对埋藏较浅的缺陷更具检测优势而长脉冲光热像对孔径较大的缺陷检测效果更好。     

Reflective fringe pattern technique for subsurface crack detection

This paper presents a novel optical technique, reflective fringe pattern (RFP), for non-destructive testing (NDT) of objects having specularly or semi-specularly reflective surfaces. The principles are based on measuring the surface deformation of a test object and identifying deformation anomalies caused by subsurface flaws. RFP is not based on optical interference and therefore, it is not subjected to the severe limitations of interferometry. Compared with the conventional methods of NDT techniques, RFP measures the response of a flaw to applied stresses, and hence it provides more direct information about the flaw criticality. In this paper, experimental demonstrations of the present technique to subsurface crack detection are presented. Two software-based methods are also adopted to enhance the flaw visibility on the output of RFP.     

The use of infrared thermography in the corrosion science area

The use of infrared (IR) cameras has in recent years gained interest as a non‐destructive testing (NDT) technique in a number of different research fields. All objects with a temperature above absolute zero emits IR radiation, and the amount of radiation increases with temperature. Infrared thermography is a non‐contact technique with high speed which allows inspection of large areas in a relatively short time. In the present work different aspects of IR thermography are described and discussed. Further, corrosion panels with defects, i.e. blisters and filiform corrosion, have been investigated with pulsed thermography. The area of the blisters and filaments, measured with pulsed thermography, have been evaluated, the result obtained have been compared with results from surface profile measurements of the same area. The differences between the results and the limitations of the pulsed thermography are discussed.     

工业锅炉的无损检测技术

工业锅炉由于承受压力载荷及部分部件直接受火焰和高温烟气加热，因此具有爆炸的危险性。在其制造、安装和使用过程中的无损检测是保证产品质量和安全使用的有效手段之一。论述了上述各阶段采用的无损检测方法及目的。采用的方法除常规的无损检测方法外，还包括X射线实时成像检测和电磁涡流表面裂纹检测等方法。     

Surface crack detection in welds using thermography

Thermography is today used within non-destructive testing for detecting several different types of defects. The possibility for using thermography for detecting surface cracks in welded metal plates has here been investigated. During testing the weld is illuminated using a high power infrared light source. Due to surface cracks acting like black bodies, they will absorb more energy than the surrounding metal and can be identified as a warmer area when imaged using an infrared camera. Notches as well as real longitudinal cold cracks in a weld are investigated using the presented method. The results show that thermography is promising as a method for detection cracks open to the surface.     

Polycrystalline diamond cutting element control using high frequency C-scan image processing

The quality control of drilling tools used in the oil industry essentially consists of testing the cutting elements distributed around the petroleum tool. This study presents a nondestructive testing (NDT) method for the detection of different kinds of defects inside polycrystalline diamond cuttine elements (PDC). This ultrasonic method, based on high frequency (100 MHz) C-scan image processing, allows the detection of three major types of defect such as diamond layer debonding from the substrate, cracks and thermal defects of the diamond layers. These defects induce a perfectly quantified behaviour to mechanical abrasion resistance and fatigue tests. Experimental results show good correlation between our ultrasonic measurements and classical abrasion resistance tests. In fact, a PDC sample exhibiting defects detected by the C-scan technique has been submitted to a mechanical fatigue process and optical microscopic analysis. These tests have shown that each kind of defect has an influence on one or more mechanical characteristics. Using C-mode scanning acoustic microscopy (with a 50 μm pixel size), allows an extremely precise and quantified level of erosion resistance of the cutting elements without systematic resort to expensive destructive tests carried out during the reception of the batch. The rejection of samples showing harmful defects will eliminate the erratic and sometimes unexplained destruction of some tools which were considered to be defect-free.