This chapter presents the development of a new remote monitoring technique for the evaluation of corrosion on reinforced concrete structures, which uses embeddable variations of known ASTM standards and telecommunication technologies as a new way to estimate the rate of loss of the steel used as a component of rebar, since such phenom‐ enon is the main cause of deterioration and degradation of the civil infrastructure. The adaptation of the technique was carried out to obtain an electrochemical half-cell that can be embedded indefinitely into the concrete, which provides the measurements corre‐ sponding to the corrosive state and allows calculating indirectly the rate of corrosion through the linear polarization resistance. The adaptation is based on a reference electrode of copper/copper sulphate, a segment of the same steel of the studied structure as working electrode and an auxiliary electrode made from pure graphite, all covered by mortar.
A maintenance program must include several techniques of monitoring of the electric motor's conditions. Among these techniques, probably the two classic ones are related to megger and impulse test. Unfortunately, in both cases, inherent drawbacks can expose the electrical motor at a high voltage that could deteriorate insulation condition making difficult its use on industrial environment. As the electrical machines have several different components (e.g., bearings, rotor bars, shaft, and stator windings), the fault frequencies can be excited by mechanical and/or electrical faults making the identification of the real condition difficult. This chapter describes several methods of the nondestructive tests for induction motors based on the motor current signature analysis (MCSA), magnetic flux, and vibration analysis. The method of analysis is a good alternative tool for destructive tests and fault detection in induction motors. Numerical and experimental results demonstrate the effectiveness of the proposed technique. This chapter also presents a model suitable for computer simulation of induction motor in a healthy state and with general asymmetries that can be analyzed simultaneously. The model makes it possible to conduct research on different characteristics of engines and outstanding effects produced by the faults.
The subject area regards to metrology and measurement methods applied for non-destructive investigation of electrical discharges occurring in oil insulation systems of high-voltage devices. The main aim of performed research studies is a detailed and multivariate analysis of physical phenomena associated with generation of electrical partial discharges (PD), which occur in oil insulation of electrical equipment. An important cognitive component was the verification whether the form of PD has an effect on the energy contribution of the physical phenomena associated with their generation. For investigating the physical processes associated with generation of PD, a system for modelling, the study and analysis of physical phenomena associated with their generation in insulating oil were designed and implemented. In particular, the PD were simulated in three setups: (1) a surface system, (2) needle-needle system in insulating oil and (3) needle-needle system in insulating oil with gas bubbles. In these experimental setups, optical signals (IR, UV and visible), ultra–high frequency electromagnetic and high-energy X-ray radiation, acoustic emission and thermal images were registered. Recorded signals were subjected for multi-variant investigation and analyses in the time and frequency domains. The contribution of particular physical phenomena was determined.
Accurate evaluation is the final aim of nondestructive testing (NDT). However, the present electromagnetic NDT methods are commonly used to check the existence of defects, and all the tested targets only consist of concave defects (i.e., section-loss defects), such as holes, cracks, or corrosions, failing to evaluate the tested surface topography, which mainly consists of concave-shaped and bump-shaped features. At present, it is accepted that the commonly observed signals of the defects mainly manifest themselves in a single-/doublepeak wave and their up/down directions of the peak wave can be easily changed just by changing the directions of either applied magnetization or pick-up units even for one defect. Unlike the present stylus and optical methods for surface topography inspec‐ tions, a new electromagnetic NDT and evaluation (NDT&E) methodology is provided based on the accurate magnetic representation of surface topography, in which a concaveshaped feature produces “positive” magnetic flux leakages (MFLs) and therefore forms a “raised” signal wave but a bump-shaped feature generates “negative” magnetic fields and therefore leads to a “sunken” signal wave. In this case, the corresponding relation‐ ships between wave features and surface topography are presented and the relevant evaluation system for testing surface topography (concave, bumped, and flat features) is built. The provided methodology was analyzed and verified by finite element and experimental methods. Meanwhile, the different dimension parameters of height/ depth and width of surface topography are further studied.
This chapter discusses the principle and application of two model‐based algorithms for processing non‐dispersive and dispersive ground penetrating radar (GPR) data over layered medium under monostatic antenna configuration. Both algorithms have been selected for their super‐time resolution capability and reduced computational burden; they allow GPR to measure a layer thickness smaller than the fraction of the dominant wavelength. For non‐dispersive data, the ESPRIT algorithm is generalized to handle different kinds of data models encountered in experiments and in the literature. For dispersive data, the proposed adaptation of the MPM algorithm allows recovering the full‐time resolution and jointly estimating the time delays and quality factors of a layered medium with reduced bias. Both processing techniques are applied to probe‐layered roadways for NDT&E purposes.
Non-destructive techniques have always been used in the study of built cultural heritage because of the high cultural value of the concerned objects and the need to preserve them as intact as possible. In this chapter, different non-destructive techniques applied to the conservation of historical building are presented. The selected techniques concern the measurement of some physical properties of the building materials measured at the surface: water absorption, permeability, water content, cohesion, hardness and so on; the actual conditions of the building: stress state, deformation, crack growth and so on; and in-depth physical properties: mechanical properties, inner structure of walls, damp location and salt content. Some of these techniques are used for inspection of the building at a given time, whereas others can be applied for long periods of time to investigate the evolution of the building or of one of its parts (e.g., crack propagation) with time.
The application of acoustic emission (AE) technique in monitoring the safe condition is a useful technique in steel and concrete structures, whereas its application is restrained in masonry structures due to the layered property. Qualitative and quantitative analyses were investigated in this research to improve the AE application in masonry structures. For quantitative analysis, an improved localization method is proposed to give more reliable crack localization results. In the proposed method, the parameter ξ on the behavior of inhomogeneity of the monitored structure could minimize the unavoidable propagation delay caused by the layers in the masonry structure. The rest results approved the reliability of the proposed method in masonry structures. For qualitative analysis, the parameter analysis, including the cumulative AE event, frequency distribution, time-scaling exponent, and b-value, was adopted to monitor one historical church and was approved to be useful.
A novel beamforming array technique and probability-based diagnostic imaging method are proposed to determine the acoustic emission (AE) source in plate-like structures. The technique that differs from common beamforming array techniques, in particular a sensor network, is used instead of a linear sensor array, to highlight information on the AE source location in one coordinate system as energy distribution. To reduce the uncertainty, avoid the boundary reflection effect, and ensure the rationality of the signal superposition, a Hilbert transform-based signal processing is applied before the delay-and-sum algorithm and a probability-based diagnostic imaging method is developed for AE source localization. The finite element numerical simulation method and the pencil-lead-broken experiment on aluminum plate are also conducted, and a thin-walled cylinder pipe-like structure is also tested by the pencil-lead-broken experiment to develop the application of the proposed method in various fields. The results indicate that this method is efficient and capable of visually showing the localization results highlighted in the probability images.
Experimental data and modelling results for pipeline wall thinning confirm a classification of Guided Wave (GW) propagation and detected features based on signal amplitude. This interpretation leads to a decision on a follow up inspection based on High, Medium or Low priority. The severity of defects must be determined; achievable by examining the signal amplitude as a function of metal loss. Specifically, if resonance can be obtained at a particular frequency, the operator can identify the wall thickness loss through the reflected GW energy amplitude. Previous research presented in this chapter identified a suitable strategy to deploy this thickness resonance technique, starting from dispersion curves (DC) development, to the analysis of the thickness loss effect on the DC, and experiments that prove the effectiveness of the methodology.
A model for studying the effects of defect surface roughness on ultrasonic signals is described. The model contains many aspects of a real inspection system, giving predictions of interest to practical ultrasonic non-destructive testing. Acoustic Kirchhoff theory is used in a full time-dependent calculation, to give A, B or C scan information for arbitrary inspection geometries. This paper presents comparisons of the model predictions and experimental results. Comparison with time-harmonic pulse-echo measurements from a corrugated surface shows agreement to within 2 dB for average scan amplitudes. Comparison is also made with time-dependent pulse-echo measurement of the variation of average signal amplitude with angle of incidence, for surfaces ranging from smooth to very rough. Agreement between the experimental results and the model predictions is typically to within 3 dB, except for very rough surfaces. Model predictions are then presented for 45° tandem inspection and 60° pulse-echo inspection of defects of various orientations. The model shows how roughness decreases the detectability of well-oriented defects but enhances the detectability of defects which are mis-oriented by more than ≈ 20°. The effects of roughness on sizing techniques are also briefly discussed. It is shown that amplitude measurements for the dB drop technique may require careful interpretation when surface roughness is present. Time-based sizing techniques may also be affected, since roughness can lead to the loss of distinct diffracted signals from which to make timing measurements.
The Dynamic Acoustic Intensity Scanning (DAIS) technique is an innovative concept based on the measurement of intensity to capture the flow of acoustic energy over a structure. It can be directed to a wide variety of nondestructive testing and quality control applications. This paper presents the results of a project designed to evaluate the suitability of DAIS as a remote sensing technique to monitor fatigue cracking in the submerged welded nodes of offshore structures.
This chapter discusses the results of the testing of the iterative transform algorithm on experimental data. Two kinds of limited-angle situations were simulated in the studies discussed in the chapter. The first kind of limited-angle data situations was caused by the over-attenuation of the x-rays by the long paths through the object. In the second kind of limited-angle image reconstructions, the missing data cone may have oriented in an arbitrary direction, which in general is not related to the direction of maximum attenuation.The results of the experiment validated the practical value of the iterative transform algorithm in reconstructing images from incomplete x-ray data, both incomplete projections and limited-angle data. In all the cases tested, there were significant improvements in the appearance of the images after iterations. The visual improvements were substantiated in a quantitative manner by the plots of errors in wall-thickness measurements, which in general decrease in magnitude with iterations.
The Expert System (ES) EXTRACSION CdF (système Expert de TRaitement, d'Analyse et de Classification des SIgnaux d'Origine Nucléaire en Courants de Foucault) is described. The purpose of this system under study is to diagnosticate pipes of Steam Generators (SG), which are tested by Eddy Currents. This ES drives algorithmical programs (whose some are here presented) and describes the real world with an object oriented representation. This representation is used as well for metallurgical structures of SGs as for measurement method or signal structures. The important problems of a priori Knowledge (apK) and coherence between the different knowledges are broached.
In the iron smelting process, slag, which is production waste, usually forms the majority of remains found at ancient metallurgical sites. In Ban Kruat, Buriram Province, Northeast Thailand, at least 50 slag-bearing sites have so far been documented, which can be divided into nine clusters. One of the clusters, Ban Sai Tho 7 group, demonstrates a quite unique spatial organisation of slag mounds. Here, 10–11 mounds of circular or ellipsoid shape were found surrounding a flat area of 350 × 400 m. Two different stages of iron production were identified between these two areas: iron smelting at the circular mounds and iron smithing on the central plain. Compared with the nearby neighboring heap, this is a comparatively large concentration of slag, and possibly illustrates the long dynamic history of iron-smelting production. Although in 2009 and 2010, this site was estimated to have existed in the Iron age by accelerator mass spectrometric (AMS) dating of in-slag charcoal, the result only reveals the early production of iron-smelting regarding the law of superposition. Therefore, in order to assess the duration of production, optically stimulated luminescence (OSL) dating was employed to date technical ceramics (i.e., furnaces and tuyères) from the topmost layers of the surface slag heap in order to indicate the late or terminal iron-smelting production. The dates of the technical ceramics that came from the different sides of the slag heap show two different periods: the early 10th to the early 11th centuries (around 1000–1100 years ago) and the early 17th century (around 370 years ago). More significantly, the old samples were at the edge of the southern part, while the young samples came from the topmost of the northeastern slag heap. Therefore, these two furnaces were possibly used in different periods and distributed in different areas of the slag heap. The result also illustrates the terminal period (the early 17th century) of metallurgy in the ancient Angkor highlands, particularly at the Ban Sai Tho 7 site. An iron-smelting activity at Ban Sai Tho 7 seems to exist in the same location for several centuries. Moreover, OSL dating is an alternative method to directly date the late period of iron-smelting production.
The automation of different inspection tasks is an increasingly important factor, especially with respect to the reduction of inspection time and the increase of reliability. This paper describes a system that integrates and automates the different inspection tasks. The evaluation module incorporates an expert system providing graphic and alphanumeric outputs of results, emulating the human evaluator.
The report considers the problems of developing and creating matrix eddy current transducers. The structures of their sensitive elements are described as well.
In this paper we focus on a new development of an ultrasonic array for endoscopic application in medicine and NDT. This new device is a so-called circular array and consists of more than 80 strip elements. The diameter of this array is 10 mm. The frequency is about 5.0 MHz. The mathematical algorithm, monochromatic and broadband calculations of the soundfield are shown. Furthermore the process of manufacturing is discussed and partially depicted.
This paper reports the results so far obtained in developing innovative NDT for component evaluation in power plant. Application of EMAT technique has been developed for heat exchanger inspections and proper equipment was manufactured and in field tested. To improve inspection capabilities also defect imaging ultrasonic methods have been intensively investigated and a syntetic tomography, based on phased array transducers, has been developed. Acoustic Emission (AE) techniques are also considered and the results and actual benefits already achieved in continuous monitoring of plant components are reported.
Alternating current (a.c.) is widely used to magnetise components and materials for magnetic particle inspection (MPI). The skin effect associated with this current wave form is inevitable because of the eddy current and hysteresis losses which occur. It is sometimes suggested that the greater ease with which very shallow defects are found when a.c. is used in MPI is due to the skin effect. This study investigates the suggestion and the conclusion is that the observed effect is not associated with the skin effect but is due to the complication forces between the leakage field and the magnetic particles used to indicate it.
