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Showing papers in "Ndt & E International in 2004"


Journal ArticleDOI
TL;DR: In this article, the authors used two kinds of classifiers: a supervised classifier and also an unsupervised one (Kohonen's map), combining two techniques: the k-means algorithm and the k nearest neighbours.
Abstract: Acoustic Emission (AE) can be used to discriminate the different types of damage occurring in a constrained composite. However, the main problem associated with data analysis is the discrimination between the different acoustic emission sources. The objective of the cluster analysis is to separate a set of data into several classes that reflect the internal structure of the data. Indeed, cluster analysis is an important tool for investigating and interpreting data. In this paper we use two kinds of classifiers: a supervised classifier and also an unsupervised one (Kohonen's map). We combine two techniques: the k-means algorithm and the k nearest neighbours. Glass/polyester model specimens were used for the validation of the proposed methodology. We worked on polyester resin and glass/polyester unidirectional specimens, subjected to tensile loading within different configurations, awaiting preferential damage modes in the material. Moreover, single fibre composites have been tested to produce fibre breakage acoustic emission events under conditions closely approximating those encountered in a real composite.

266 citations


Journal ArticleDOI
TL;DR: In this article, the effect of pipe size, defect size, guided wave mode and frequency on the reflection from notches was analyzed for a 3-in. schedule 40 steel pipe.
Abstract: Ultrasonic guided waves are used for the rapid screening of pipelines in service and simple, standard testing procedures are already defined. The implementation of the method enables the localization of the defects along the length of the pipe and offers a rough estimate of defect size. In this article we present a systematic analysis of the effect of pipe size, defect size, guided wave mode and frequency on the reflection from notches. The maximum and minimum value of the reflection coefficient at varying axial extent are identified and used for the purpose of defect sizing. Maps of reflection coefficient as a function of the circumferential extent and depth of the defect are presented for a 3 in. schedule 40 steel pipe. An approximate formula, which allows these results to be extrapolated to other pipe sizes, is proposed and evaluated.

253 citations


Journal ArticleDOI
TL;DR: In this paper, a review of the technologies currently employed, along with examples of recent field applications, and some of the ongoing advancements and options for the future are also discussed, as well as some of their ongoing advancements.
Abstract: Rail Flaw Detection has an important part to play in ensuring the safety of the world's railroads. Recent accidents caused by broken rails have focused attention on the technologies that enable the detection of flaws in railroad rail. This paper reviews the technologies currently employed, along with examples of recent field applications. Some of the ongoing advancements and options for the future are also discussed.

210 citations


Journal ArticleDOI
TL;DR: This work presents a new approach for surface roughness characterization using computer vision and image processing techniques and some statistical parameters have been calculated from the GLCMs and compared with the arithmetic average roughness Ra.
Abstract: Computer vision technology has maintained tremendous vitality in many fields. Several investigations have been performed to inspect surface roughness based on computer vision technology. This work presents a new approach for surface roughness characterization using computer vision and image processing techniques. A vision system has been introduced to capture images for surfaces to be characterized and a software has been developed to analyze the captured images based on the gray level co-occurrence matrix (GLCM). Three standard specimens and 10 machined samples with different roughness values have been characterized by the presented approach. Three-dimensional plots of the GLCMs for various captured images have been introduced, compared and discussed. In addition, some statistical parameters (maximum occurrence of the matrix, maximum occurrence position and standard deviation of the matrix) have been calculated from the GLCMs and compared with the arithmetic average roughness Ra. Furthermore, a new parameter called maximum width of the matrix is introduced to be used as an indicator for surface roughness.

189 citations


Journal ArticleDOI
TL;DR: In this article, the results of experiments they have conducted on rail at test tracks and on an operating railroad are provided. But the results are limited to the use of noncontact air-coupled and electromagnetic acoustic transducers as receivers of sound energy emanating from rail.
Abstract: The authors provide the results of experiments they have conducted on rail at test tracks and on an operating railroad. Results are presented that suggest that the frequency range [40,80] kHz readily supports guided waves. Theoretical results including roots of the dispersion relations for rail and a sample of wave displacement within a railhead are presented. Non-contact air-coupled and electromagnetic acoustic transducers (EMATs) are discussed as receivers of sound energy emanating from rail. The results of an experiment that used air-coupled transducers to profile the radiation pattern of a rail are presented. A rail cutting experiment with EMATs that simulated a transverse rail defect is discussed. Conclusions that the authors have drawn from their work are summarized at the end of the paper.

162 citations


Journal ArticleDOI
TL;DR: In this paper, 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.
Abstract: 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.

146 citations


Journal ArticleDOI
TL;DR: In this paper, the feasibility of employing mechatronic conductance signatures of surface bonded piezoelectric-ceramic (PZT) patches in monitoring the conditions of reinforced concrete (RC) structures subjected to base vibrations, such as those caused by earthquakes and underground blasts, were considered.
Abstract: The last three decades have witnessed the construction of vast infrastructural facilities, especially from reinforced concrete (RC), in many parts of the world. This has necessitated the development of automated, real-time and online structural health monitoring systems, which can provide a cost-effective alternative to the traditional visual inspection. This paper discusses the feasibility of employing mechatronic conductance signatures of surface bonded piezoelectric-ceramic (PZT) patches in monitoring the conditions of RC structures subjected to base vibrations, such as those caused by earthquakes and underground blasts. Specifically, flexural and shear cracks, two prominent types of incipient damages in RC structures, were considered. The PZT patches were found to be able to identify both damage types much earlier than the conventional low frequency dynamic response techniques. Therefore, the PZT patches can be potentially employed to monitor the health of RC frames, which constitute the main skeletons of most large civil structures.

129 citations


Journal ArticleDOI
TL;DR: In this article, the dependence of Barkhausen noise on elastic and plastic deformations, achieved in tension and in compression, has been investigated both in Armco iron and a low carbon steel.
Abstract: The dependence of Barkhausen noise on elastic and plastic deformations, achieved in tension and in compression, has been investigated both in Armco iron and a low carbon steel These materials exhibit quite different behaviours, especially with regard to the effect of plastic deformation: a tensile plastic deformation (>1%) induces a marked increase in Barkhausen noise for Armco iron while it induces a steep decrease in the low carbon steel The comparison between the tensile and compressive behaviours, as well as between the elastic and plastic regimes of deformation enables us to attribute these effects to two underlying mechanisms, ie effect of residual internal stresses through magneto-elastic coupling and dislocation–domain wall interaction In Armco iron, the latter mechanism seems to have the strongest influence on the Barkhausen noise, while in the low carbon steel the influence of residual internal stresses prevails

105 citations


Journal ArticleDOI
TL;DR: In this paper, a three-part finite element model is developed that characterizes the ultrasonic pulse produced by an electromagnetic acoustic transducer (EMAT), which is used to optimize the design of the EMAT system.
Abstract: A three-part finite element model is developed that characterizes the ultrasonic pulse produced by an electromagnetic acoustic transducer (EMAT). The model represents several significant improvements over previously published works, as follows: (a) spatial inhomogeneities in the magnetic flux density are calculated and then incorporated in the determination of body forces, (b) an improved model of the electromagnetic induction phenomenon is formulated, allowing a more accurate evaluation of the ultrasonic pulse launched by an EMAT transmitter and (c) results from the model are compared directly with experimental measurements, yielding discrepancies of the order of 15% in the amplitude of the ultrasonic pulse. The new model is used to optimize the design of the EMAT system. In particular, a parametric study was conducted on the effects of varying an EMAT's magnet-to-coil width ratio. For the EMAT configuration considered, significant improvements can be achieved in the ultrasonic beam amplitude and profile by increasing the ratio to about 1.2; further increases in magnet dimensions yield only marginal improvements in the ultrasonic beam, at the cost of excessive EMAT size.

99 citations


Journal ArticleDOI
TL;DR: In this article, a new method for determination of Acoustic emission (AE) wave arrival times for source location purposes is described, based on a simple geometry of carbon-fibre reinforced plastic.
Abstract: Here we describe a new method for determination of Acoustic Emission (AE) wave arrival times for source location purposes. In complex structures or structures of small dimension, an AE source can rapidly become distorted by the presence of several modes travelling at different speeds, and through contamination by reflections and mode conversions. Using a simple geometry of carbon-fibre reinforced plastic, the responses acquired from two-sensor and four-sensor arrays have been analysed using a variety of techniques, which are variants on identification of first arrival time and/or the arrival of the maximum intensity of the wave. The methods are compared in terms of the consistency of the velocity which is indicated at different points in the arrays, and a method based on wavelet decomposition, filtering and threshold-crossing is recommended as the most consistent and accurate method of determining arrival time.

94 citations


Journal ArticleDOI
TL;DR: In this paper, an experimental study on the applicability of Acoustic Emissions (AE) for rail-track defect diagnosis is presented. And the authors conclude that the AE technique offers a complementary tool for rail track defect detection.
Abstract: In light of recent accidents in the rail industry, the assessment of the mechanical integrity of rail-track is of vital importance. This encompasses the integrity of the track due to rolling contact fatigue and surface wear. Whilst numerous techniques are employed for crack detection, several defects have clearly been missed. In Europe, more than 100 rails are broken each year and rail maintenance costs within the European Union is estimated at 300-million Euros annually [Inst Mech Engrs 216 (2001) 249]. The derailment of a train at Hatfield in October 2000 is a tragic example of a fractured rail going undetected. This paper presents an experimental study on the applicability of Acoustic Emissions (AE) for rail-track defect diagnosis. An experimental test-rig was employed for this programme. This allowed for a surface defect to be seeded onto the test-rig. The investigation presented is part of an on-going attempt to develop the non-destructive technique of AE for assessing the surface integrity of rail-track. The AE technique is not new but the application in this particular instance is unique. It is concluded that the AE technique offers a complementary tool for rail track defect detection.

Journal ArticleDOI
TL;DR: In this paper, phase interference of microwave images has been experimented for remote submillimeter-accuracy detection of structural displacements of a real-scale building, subject to tensional stress.
Abstract: Phase interference of microwave images has been experimented for remote submillimeter-accuracy detection of structural displacements of a real-scale building, subject to tensional stress. The images are obtained by a synthetic-aperture interferometric radar, making use of continuous-wave step-frequency waveform. Phase information of the synthesized microwave images is exploited for detecting displacements of the illuminated structure.

Journal ArticleDOI
TL;DR: In this paper, a study of nonlinear pattern classifiers, implemented by artificial neural networks, to classify weld defects existent in radiographic weld beads, aiming principally to increase the percentage of defect recognition success obtained with the linear classifiers.
Abstract: In recent years there has been a marked advance in the research for the development of an automatized system to analyze weld defects detected by radiographs. This work describes a study of nonlinear pattern classifiers, implemented by artificial neural networks, to classify weld defects existent in radiographic weld beads, aiming principally to increase the percentage of defect recognition success obtained with the linear classifiers. Radiographic patterns from International Institute of Welding (IIW) were used. Geometric features of defect classes were used as input data of the classifiers. Using a novel approach for this area of research, a criterion of neural relevance was applied to evaluate the discrimination capacity of the classes studied by the features used, aiming to prove that the quality of the features is more important than the quantity of features used. Well known for other applications, but still not exploited in weld defect recognition, the analytical techniques of the principal nonlinear discrimination components, also developed by neural networks, are presented to show the classification problem in two dimensions, as well as evaluating the classification performance obtained with these techniques. The results prove the efficiency of the techniques for the data used.

Journal ArticleDOI
TL;DR: In this paper, an automated vision system is introduced to detect and assess the welding defects of gas pipelines from the radiographic films, which offers many advantages such as enhancing the captured images so that the defects appear much clear and eliminating the loss of image details, which occurs due to film deterioration by the time.
Abstract: In this paper, a novel automated vision system is introduced to detect and assess the welding defects of gas pipelines from the radiographic films. The proposed vision system was used to capture images for the radiographic films and apply various image processing and computer vision algorithms to detect the welding defects and to calculate necessary information such as length, width, area and perimeter of the defects. A developed software, named AutoWDA, has been fully written in lab using Microsoft Visual C++6 to perform the analysis process. The proposed system offers many advantages such as enhancing the captured images so that the defects appear much clear and eliminating the loss of image details, which occurs due to film deterioration by the time, by transferring the radiographic films into digitized images, which could be saved on magnetic mass storage media. The proposed system is considered quite cheap compared with commercial radiographic image enhancement systems.

Journal ArticleDOI
TL;DR: In this paper, the measured weight loss data for a number of mild steel bars contained in Portland Cement concrete, together with predicted weight loss values monitored using potentiostatically controlled linear polarisation resistance (LPR) measurements are reported.
Abstract: The measured weight loss data for a number of mild steel bars contained in Portland Cement concrete, together with predicted weight loss values monitored using potentiostatically controlled linear polarisation resistance (LPR) measurements are reported. Three sets of reinforced concrete specimens, each containing electrically isolated mild steel bars, were subjected to either • chloride-induced corrosion, • carbonation-induced corrosion • a control nitrogen rich environment with minimal corrosion. Each set of specimens was initially exposed to a 22-hour dry, 2-hour wet controlled environment for a duration of between 1026 and 1085 days. This was later changed to a 6-day dry, 1 day wet cycle for the carbonation exposure specimens after the initial set of gravimetric testing. The weight loss for each bar due to corrosion was recorded. Instantaneous LPR measurements were also taken on each bar at regular intervals throughout the exposure period. These resistance measurements were then integrated over the exposure period to estimate total weight loss. The results show that weight loss evaluated from experimental LPR measurements gives a significant over-estimate of the weight losses measured gravimetrically.

Journal ArticleDOI
TL;DR: In this paper, a study to materials microstructure characterization and especially the heat affected zones (HAZ) near welds using eddy current techniques has been conducted, where the authors have prepared series of samples made of Aluminum and steel and heated at different temperatures with variable exposure times.
Abstract: 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.

Journal ArticleDOI
TL;DR: In this paper, an expert vision system for automatic inspection of gas pipeline welding defects from radiographic films is presented, which is capable of identifying and testing the main types of welding defects (11 defects) in gas pipelines welded by shielded metal arc welding.
Abstract: Automatic inspection of welded gas pipelines is desirable because human inspectors are not always consistent evaluators. In addition, automatic inspection decreases the cost of inspection process and improves the inspection quality. In this paper, an expert vision system for automatic inspection of gas pipeline welding defects from radiographic films is presented. The proposed system has been established in the Metrology lab, Mansoura University, Faculty of Engineering. The software, named AutoWDI, is fully written in lab using Microsoft Visual C++ and is ready to run on any Windows environment. The proposed vision system is used to capture images for the radiographic films then applies various image processing and computer vision algorithms to recognize the defects and to make acceptance decisions according to international standards. The expert system is based on a knowledge base, which was gathered from specialists, textbooks and international standards. The proposed system is capable of identifying and testing the main types of welding defects (11 defects) in gas pipelines welded by shielded metal arc welding.

Journal ArticleDOI
TL;DR: In this paper, an experimental study of ultrasonic, through-transmission, wave propagation on fresh cementitious material is discussed, where the propagation characteristics of different frequency tone-bursts revealed the strong dispersive behavior of this type of materials while using sine-sweep excitation, the attenuation up to about 1 MHz was examined.
Abstract: Results from an experimental study of ultrasonic, through-transmission, wave propagation on fresh cementitious material are discussed in this paper. The propagation characteristics of different frequency tone-bursts revealed the strong dispersive behavior of this type of materials while using sine-sweep excitation, the attenuation up to about 1 MHz was examined. Sand content and size exercise significant influence on wave parameters while entrapped air bubbles seem to dominate the attenuation at low frequencies since cement paste specimens, containing no sand, exhibit strong attenuation. The possibility of mortar composition characterization within 10 min after mixing is also addressed leading to encouraging results.

Journal ArticleDOI
TL;DR: In this article, a coal-tar-enamel-coated pipe was investigated experimentally over a 5-30-kHz frequency range and up to a 1.7m soil cover.
Abstract: Attenuation of the fundamental torsional guided waves in a coal-tar-enamel-coated pipe was investigated experimentally over a 5–30-kHz frequency range and up to a 1.7-m soil cover. The attenuation coefficients in the coated pipe above the ground were an order of magnitude greater than in bare pipe and, over the frequency range studied, it increased approximately linearly with frequency. Soil cover on the pipe caused the attenuation to increase significantly further—by a factor of three to ten at a 1.7-m cover depth—and altered its frequency dependence to become somewhat parabolic with a minimum point.

Journal ArticleDOI
TL;DR: In this article, a spectral analysis of radar surface waves for non-destructive evaluation of cover concrete is presented, which consists in taking several profiles at the same place using different distances between the two antennas.
Abstract: This paper presents the use of spectral analysis of radar surface waves for the non-destructive evaluation of cover concrete. With only two commercial coupled antennas centred around 1.5 GHz, an original measurement mode is proposed for obtaining dynamic wide angle reflection refraction profiles. It consists in taking several profiles at the same place using different distances between the two antennas. After separation of the air wave and surface waves, the wrapped phase spectrum is obtained for a given distance between two receiver positions by means of a Fourier transform. For a given position, the speed is calculated for each frequency from the known wave travel distance. The repetition of the processing for other positions gives the speed variation along a profile. Moreover, the dispersion analysis can provide further information on the humidity of the material. Tests on a dry concrete surface and after wetting provide reliable results which allow the two moisture contents to be distinguished.

Journal ArticleDOI
TL;DR: In this paper, the application of time-dependent parameters (e.g., instantaneous energy, mean and median frequencies, and bandwidth) in the detection and diagnosis of localised and wear gear failures is discussed.
Abstract: Time–frequency methods, which can lead to the clear identification of the nature of faults, are widely used to describe machine condition. Capabilities of time–frequency distributions in the detection of any abnormality can further be improved when their low-order frequency moments (or time-dependent parameters), which characterise dynamic behaviour of the observed signal with few parameters, are considered. This paper presents the applications of four time-dependent parameters (e.g. the instantaneous energy, mean and median frequencies, and bandwidth) based upon the use of spectrogram and scalogram, and compares their abilities in the detection and diagnosis of localised and wear gear failures. It has been found that scalogram based parameters are superior to those of a spectrogram in the detection and location of a local tooth defect even when the gear load is small, as they result in equally useful parameters in the revelation of gear wear. Moreover, the global values of these time-dependent parameters are found to be very useful and provide a very good basis for reflecting not only the presence of gear damage, but also any change in operating gear load.

Journal ArticleDOI
TL;DR: In this article, a new measurement parameter has been developed for microstructural characterisation called MAE absolute energy and has proved to be a useful quantitative method in MAE waveform measurement.
Abstract: Magneto-acoustic emission (MAE) and magnetic Barkhausen noise (MBN) sensing techniques were developed and employed to characterise plastically deformed and heat-treated AISI 430 ferritic stainless steel samples. These results have been compared to the mechanical hardness, coercivity and residual stress of the samples. MAE and MBN were shown to decrease with increasing permanent material deformation. It was found that the inverse of MAE (absolute energy) and MBN (RMS) are linearly proportional to hardness. With increased deformation, the resultant change in dislocation density was found to effect material coercivity. It has been shown that the inverse of MAE absolute energy and MBN have an exponential relationship to the change in material coercivity. The results are explained in terms of the different mechanisms that effect dislocation-domain wall interactions. A new measurement parameter has been developed for microstructural characterisation called MAE absolute energy and has proved to be a useful quantitative method in MAE waveform measurement.

Journal ArticleDOI
TL;DR: In this paper, the authors proposed an original solution to the acoustic impedance mismatch between a PZT transducer and a water load, which consists in using two matching layers where one of them is the glue.
Abstract: The aim of this work is to propose an original solution to the acoustic impedance mismatch between a PZT transducer and a water load. The characteristic acoustic impedance of the PZT is around 33 MRayl. Theoretically, a quarter-wave layer with characteristic acoustic impedance equal to 7 MRayl is necessary to match the transducer to water. In practice, it is difficult to find a material with this particular impedance. Two or more quarter-wave layers may also be used. The following proposed solution consists in using two matching layers where one of them is the glue. Moreover, their thicknesses are not equal to a quarter of their individual wavelength. Once the glue is taken as the first matching layer, the specific material of the second layer can easily be found. In this work, the second layer, which is also the front layer, is made of glass. The thickness of each matching layer is then calculated as a function of the characteristic acoustic impedance of the two layers. The influence of the thickness of these layers is discussed. The proposed matching configuration is analyzed and theoretical results have been carefully and successfully compared with measurements.

Journal ArticleDOI
TL;DR: In this article, a technique based on measurement of change of natural frequencies has been employed to detect multiple cracks in long pipes containing fluid at different pressures, and two simultaneous cracks are considered in the experiments.
Abstract: A technique based on measurement of change of natural frequencies has been employed to detect multiple cracks in long pipes containing fluid at different pressures. The cracks have straight fronts and are non-leaking. Both theoretical and experimental results are presented. Two different materials, aluminium and mild steel, have been examined. The fluid considered is water; three (gauge) pressures in the range 0–981 kPa, and crack size to thickness ratio in the range 0.19–0.64 are studied. Two simultaneous cracks are considered in the experiments. The crack locations are predicted with an error less than 4.3%. Results on crack-equivalent rotational spring stiffness, which can be useful in the calculation of natural frequencies and crack size predictions, are reported.

Journal ArticleDOI
TL;DR: In this paper, an investigation has been made of the potential of pulsed-transient thermography for identifying the location of fixtures beneath aircraft skins to facilitate accurate automated assembly operations.
Abstract: In this work, an investigation has been made of the potential of pulsed-transient thermography for identifying the location of fixtures beneath aircraft skins to facilitate accurate automated assembly operations. Representative test structures, comprising of aircraft skin (i.e. aluminium (Al) or carbon fibre reinforced plastic (CFRP)) positioned over a thick strut fixture of Al or CFRP, were investigated experimentally and analysed using finite difference thermal modelling software, taking into account the size and depth of the features, as well as the thermal properties of the investigated materials. The ability of the technique to detect a subsurface fixing and to provide information about its location was analysed. Results from the modelling and the experimental analysis are presented and discussed.

Journal ArticleDOI
TL;DR: In this paper, an artificial neural network was trained to recognize the stress intensity factor in the interval from microcrack to fracture from acoustic emission (AE) measurements on compact tension specimens.
Abstract: An artificial neural (ANN) network was trained to recognize the stress intensity factor in the interval from microcrack to fracture from acoustic emission (AE) measurements on compact tension specimens. The specimens were made from structural steel SWS490B whilst the ANN had a 5-14-1 structure. The number of neurons in the input layers was five inputs of the AE parameters such as ring-down counts, rise time, energy, event duration and peak amplitude. The performance of the ANN was tested using a specific set of the AE data. The ANN is a promising tool for predicting the stress intensity factor of material using AE data.

Journal ArticleDOI
TL;DR: In this article, the authors present the possibilities of applying ultrasonic methods in asphalt concrete specimen testing in order to estimate fatigue life using ultrasonic characteristics of specimens and the procedures and results of testing cylinder shaped samples of both ultrasonic analysis and fatigue life testing are described.
Abstract: This paper presents the possibilities of applying ultrasonic methods in asphalt concrete specimen testing in order to estimate fatigue life using ultrasonic characteristics of specimens. The procedures and results of testing cylinder shaped samples of both ultrasonic analysis and fatigue life testing are described. The ultrasonic method was first used in order to obtain the seismic characteristics of specimens. Then, the specimens were tested for fatigue lives using the repeated-loading indirect tensile test equipment (SDU-Asphalt Tester). To be able to model the fatigue lives, in addition to conventional fatigue model parameters new parameters from this ultrasonic analysis were taken into consideration. These additional parameters are acquired from the seismic measurements. Hence, only by examining the ultrasonic method, it will be possible to predict the fatigue lives of the specimens non-destructively.

Journal ArticleDOI
TL;DR: In this article, the propagation of short pulses in concrete with known frequency-dependent properties is studied and the extent of how the pulses are attenuated and distorted is analyzed and the implications on GPR applications are also discussed.
Abstract: The knowledge of how a dispersive, dielectric medium such as concrete affects a propagating short electromagnetic pulse used in ground penetrating radar (GPR) is helpful both in the interpretation of radar results and in the prediction/modelling of expected radar measurements. Although there are a number of published results on the frequency-dependent, dielectric properties of media such as concrete and soils, the use of this information is still relatively small, primarily due the lack of a reliable method of applying these properties to propagating radar pulses. Modelling the dielectric medium as low-pass filter is one solution to this difficulty. In this paper the propagation of short pulses in concrete with known frequency-dependent properties is studied. The extent of how the pulses are attenuated and distorted is analysed and the implications on GPR applications are also discussed.

Journal ArticleDOI
TL;DR: In this article, 3D laser profilometry (LP) and pulsed thermography (PT) were used in the inspection of Pentelic marble Quarry samples, after processing with different roughness treatments (i.e., 60, 80, 100, 220, 400 and 600 mesh).
Abstract: Three dimensional (3D) laser profilometry (LP) and pulsed thermography (PT) were used in the inspection of Pentelic marble Quarry Pentelic marble samples, after processed with different roughness treatments (ie 60, 80, 100, 220, 400 and 600 mesh), were evaluated in the laboratory Furthermore, different surface cleaning treatments were applied to a Pentelic marble surface in situ and then representative samples were collected and evaluated in the laboratory by the means of these two non-destructive techniques Quantitative analysis of all samples was performed The surface roughness parameter Rq at a specific length scale was estimated by the use of the LP scanning approach Furthermore, 3D micro-topography plots from the laser scans were attained PT, through the formation of temperature—time plots that display the intensity of pixels as a function of time on the obtained thermal images, was able to distinguish the influence of the applied roughness treatments Results indicate that these two non-contact and non-destructive techniques can be used for the assessment of surface roughness

Journal ArticleDOI
TL;DR: In this article, an adaptive order tracking fault diagnosis technique based on recursive Kalman filtering algorithm is presented, which is one of the important tools for fault diagnosis of rotating machinery, and the problem is treated as the tracking of frequency-varying bandpass signals.
Abstract: In this paper, an application of adaptive order tracking fault diagnosis technique based on recursive Kalman filtering algorithm is presented. Order tracking fault diagnosis technique is one of the important tools for fault diagnosis of rotating machinery. Conventional methods of order tracking are primarily based on Fourier analysis with reference to shaft speed. In this study, a high-resolution order tracking method with adaptive Kalman filter is used to diagnose the fault in a gear set and damaged engine turbocharger wheel blades. The adaptive Kalman filtering algorithm can overcome the problems encountered in conventional methods. The problem is treated as the tracking of frequency-varying bandpass signals. Ordered amplitudes can be calculated with high resolution after experimental implementation. Experiments are also carried out to evaluate the proposed system in gear-set defect diagnosis and engine turbocharger wheel blades damaged under various conditions. The experimental results indicate that the proposed algorithm is effective in fault diagnosis of both cases.