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![Theoretical ultrasonic reflection coefficient as a function of distance between parallel stainless steel plates separated by air and water (2.25 MHz, transverse wave at 45 ◦ ) [2]](profile/Iikka-Virkkunen/publication/226799918/figure/fig6/AS:302291874795522@1449083407118/Theoretical-ultrasonic-reflection-coefficient-as-a-function-of-distance-between-parallel.png)
Theoretical ultrasonic reflection coefficient as a function of distance between parallel stainless steel plates separated by air and water (2.25 MHz, transverse wave at 45 ◦ ) [2]
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The reliability of non-destructive evaluation depends on multitude of different factors. Consequently, it is difficult to assess the performance of the system. The only practical way to overcome this complexity and asses inspection reliability is using practical trials. In practical trials the inspection is performed on a known, flawed sample and r...
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... Becker et al. [2] reported that thermal fatigue cracks showed low values of echo amplitude already when no external load was applied. As Fig. 5 shows, by application of an external load the thermal fatigue crack followed the theoretical behavior of reflection amplitude as a function of crack opening (the theoretical amplitude curve is shown in Fig. 6). That is, when the crack is under tension the plateau of high amplitude is obtained and under com- pression the low amplitude plateau of reflection is observed. When no external load is applied, the obtained echo heights lie in the lower part of the steep slope region between the plateaus. Consequently, unloaded thermal fatigue cracks ...
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Citations
... For more details, we refer to [18][19][20] and the references therein. For each gear wheel, the raw signal of acoustic response that goes through a preamplifier was recorded by two receivers (channels 1 and 2) with a sampling rate of 1041.67 kHz with respect to ten different positions: ...
Based on the fact that cogwheels are indispensable parts in manufacturing, we present the acoustic resonance testing (ART) of small data on sintered cogwheels for quality control in the context of non-destructive testing (NDT). Considering the lack of extensive studies on cogwheel data by means of ART in combination with machine learning (ML), we utilize time-frequency domain feature analysis and apply ML algorithms to the obtained feature sets in order to detect damaged samples in two ways: one-class and binary classification. In each case, despite small data, our approach delivers robust performance: All damaged test samples reflecting real-world scenarios are recognized in two one-class classifiers (also called detectors), and one intact test sample is misclassified in binary ones. This shows the usefulness of ML and time-frequency domain feature analysis in ART on a sintered cogwheel dataset.
... The laser beam is translated along the positive and negative direction of the x axis, the origin of which is fixed at the centre of the defect. Since interaction between cracks and ultrasound is significantly affected by the mutual orientation between crack flank and wave propagation direction [47], tests have been performed as the angle β between the bar and the direction of the GCLAD laser beam is varied. The laser beam is arranged parallel to the surface of the bar, at a variable height d (liftoff distance). ...
Ultrasonic signal enhancement resulting from constructive interference between direct Rayleigh waves and same waves reflected by a surface defect is exploited to increase crack identification capabilities of the Gas-Coupled Laser Acoustic Detection (GCLAD) non-contact detection technology. Highlights from simulations are provided regarding the interference phenomenon in the solid and its propagation in air, where GCLAD detection occurs. Experimental campaigns are preliminarily performed on a bar to evidence the effect of cracks on the GCLAD acquired signals. Then, a signal enhancement of +30% is reached on a plate, implying that defects are efficiently scanned by moving the GCLAD in proximity of the discontinuity. Since the GCLAD allows monitoring points of a piece belonging to the same line at once, its translation in one direction is sufficient to perform a two-dimensional scan, entailing reduction of inspection time and simple automation of the interrogation layout compared to other traditional or signal enhancement-based techniques.
... There is a wide variety of parameters that may contribute to the uncertainties in the signal output of a permanently installed sensor, and this has been studied in a wide range of literature [16][17][18][19]. Some examples of these parameters include defect characteristics (location, orientation, morphology), sensor characteristics (size, frequency, position, noise) and sensor-component interaction (lift-off, coupling). ...
There is a growing interest in using permanently installed sensors to monitor for defects in engineering components; the ability to collect real-time measurements is valuable when evaluating the structural integrity of the monitored component. However, a challenge in evaluating the detection capabilities of a permanently installed sensor arises from its fixed location and finite field-of-view, combined with the uncertainty in damage location. A probabilistic framework for evaluating the detection capabilities of a permanently installed sensor is thus proposed. By combining the spatial maps of sensor sensitivity obtained from model-assisted methods and probability of defect location obtained from structural mechanics, the expectation and confidence in the probability of detection (POD) can be estimated. The framework is demonstrated with four sensor-component combinations, and the results show the ability of the framework to characterise the detection capability of permanently installed sensors and quantify its performance with metrics such as the $${\mathrm{a}}_{90|95}$$ a 90 | 95 value (the defect size where there is 95% confidence of obtaining at least 90% POD), which is valuable for structural integrity assessments as a metric for the largest defect that may be present and undetected. The framework is thus valuable for optimising and qualifying monitoring system designs in real-life engineering applications.
... For example, vertical cracks from the back wall of a plate/pipe can 300 often be detected using a single transducer set at an angle to receive the strong reflection from 301 the crack corner and smaller reflection from the crack tip. The proportion of the incident energy 302 reflected from a defect depends on its size and type, e.g. a large air-filled crack results in a 303 complete reflection, whereas a water-filled crack results in a partial reflection making it harder 304 to detect [57] [58] [59] [60] [61] [62]. As the wave-packet propagates through the material the 305 energy available for defect detection reduces due to a combination of spreading, attenuation 306 and scattering from the microstructure. ...
Condition monitoring for water and sewerage pipes is essential for the safety of the environment, energy conservation and human health. This paper focuses on the application of acoustic and ultrasonic techniques for the detection and assessment of leaks, blockages and defect in buried pipes. The review includes acoustic methods (below 20 kHz) based on vibration sensing using accelerometers, hydrophones and fibre optic sensors, and ultrasonic methods (above 20 kHz) based on the propagation of bulk and guided waves. Related data-driven, machine-learning techniques are also discussed. Typical arrangements of sensors are shown, explained and analysed in terms of their applicability to buried pipe networks. Commercial systems and state of the art research for the inspection of pipes made of a range of materials such as cast iron, high-density polyethylene and concrete are critically assessed. This review also explores the future application of autonomous robotics to deploy these sensors in water distribution and sewerage pipes.
... Based on the information reviewed in the references, the physical principle of Phased Array Ultrasonic Testing, and the importance of determining its behavior when evaluating planar discontinuities, and surface notches were machined as discontinuities to be measured [9], [10], [11], [12]. ...
... Incorrect measurements were obtained in inspection plans with a focus at 3 mm for the three resolution levels used. The previous observations allow us to conclude that a relationship exists in the curves of the average measured values of the discontinuities of the mechanized samples M2 and M7 and the real discontinuity, which corresponds to a lack of penetration generated in the welding process [11], [21]. ...
This research evaluates the effect of the variables of Phased Array Ultrasonic Testing(PAUT) on the sectoral angular beam scans “S-Scan” and the geometric morphology of planar discontinuities such as the inclination forthe ultrasonic beam and the shape of the extremity on accuracy in measurements. The study was carried out in two stages. Duringthe first stage, eight ASTM A36 steel samples with machined notches by penetration from EDM and a welded sample with lack of penetration in a butt weld were designed and produced. In the second stage, it wasmeasured the size of the discontinuities using ultrasound inspection and different configurations of the phase arrangement. The effect of each variable and inspection setting with errors between 0.2 % and 120 % were determined by statistical analysis.
... The characteristics that primarily affect the flaw response are the location and orientation of the crack, size of the crack, opening of the crack through the whole path and at the crack tip, fracture surface roughness and filling of the crack with a substance. An in-depth study of the flaw responses and crack characteristics has already been conducted by [9,10]. For the most representative flaw response signal, it is reasonable to assume that these characteristics should be met in order to achieve the best possible training data for machine learning as well. ...
Previous research (Li et al., Understanding the disharmony between dropout and batch normalization by variance shift. CoRR abs/1801.05134 (2018). http://arxiv.org/abs/1801.05134arXiv:1801.05134) has shown the plausibility of using a modern deep convolutional neural network to detect flaws from phased-array ultrasonic data. This brings the repeatability and effectiveness of automated systems to complex ultrasonic signal evaluation, previously done exclusively by human inspectors. The major breakthrough was to use virtual flaws to generate ample flaw data for the teaching of the algorithm. This enabled the use of raw ultrasonic scan data for detection and to leverage some of the approaches used in machine learning for image recognition. Unlike traditional image recognition, training data for ultrasonic inspection is scarce. While virtual flaws allow us to broaden the data considerably, original flaws with proper flaw-size distribution are still required. This is of course the same for training human inspectors. The training of human inspectors is usually done with easily manufacturable flaws such as side-drilled holes and EDM notches. While the difference between these easily manufactured artificial flaws and real flaws is obvious, human inspectors still manage to train with them and perform well in real inspection scenarios. In the present work, we use a modern, deep convolutional neural network to detect flaws from phased-array ultrasonic data and compare the results achieved from different training data obtained from various artificial flaws. The model demonstrated good generalization capability toward flaw sizes larger than the original training data, and the effect of the minimum flaw size in the data set affects the a90/95 value. This work also demonstrates how different artificial flaws, solidification cracks, EDM notch and simple simulated flaws generalize differently.
... A variety of nondestructive testing (NDT) techniques are developed to inspect and assess crack for reliability and safety issues [3]. Nevertheless, the traditional NDT techniques might be too expensive or cumbersome for the structural health monitoring (SHM). ...
... In other words, the sensitivity may decrease when the crack moves away from the center of the CDR. The representative flaws used in practical trials are important for NDT technique [3]. Further simulation shows that the resonant frequency of the CDR may be split into two resonances when the crack type becomes zigzag. ...
Crack is pervasive but crucial for infrastructures frequently exposed to atmosphere and stress, e.g. costal infrastructure, railway track, pipeline. Recently, passive wireless antenna sensors are emerging for the early crack detection and life-long monitoring. However, the mode distribution challenges the direction stability in crack detection. Enabling by a cylindrical dielectric resonator (CDR), this communication proposes a passive wireless sensor for ubiquitous crack monitoring. The proposed CDR can excite a HE11δ mode and its polarization can be configured through the change of the polarization of the incident wave. Due to the high dielectric substrate selected, the proposed CDR has a compact size of 24.0 mm (diameter) × 9.0 mm (height). By confining the near-field energy into a small magnetic wall, the CDR is naturally turned into a sensitive crack sensor. The crack growth causes a continuous shift in the resonant frequency of the radar cross section (RCS). This behavior can be wirelessly monitored in a distance of 0.25 m through a horn antenna. For a fixed crack width of 2.0 mm, the sensitivity in crack depth characterization is 25.4 MHz/mm. Due to the absence of electronic device and metal, the proposed sensor can work in extreme conditions, e.g., high-temperature environment.
... This means, the used artificial or realistic defects give similar response in the used NDT than real flaw. (Kemppainen & Virkkunen, 2011) discussed three approaches (real, artificial, and realistic flaws representativeness): ...
There has been an increasing demand for Nondestructive Testing (NDT) and Structural Health Monitoring (SHM) techniques to continuously monitor during all processes of a structure to prevent catastrophic failure and reduce maintenance costs. NDT and SHM are inspection processes which form part of the quality assurance/quality control (QA/QC) scheme. Among NDT and SHM methods, ultrasonic and guided wave techniques are the most commonly and widely used in industry. Ultrasonic methods provide the advantage of accurately locating and dimensioning defects within structures. Most of these structures consist of welded joints because welding is an economical and efficient method for obtaining a permanent joint. However, austenitic stainless steels, especially the welding process zone, exhibit heterogeneous and anisotropic behavior which has a decisive influence on the ultrasonic beam making the interpretation of ultrasonic inspection results notoriously difficult. NDT and SHM methods aim to detect possible defects and characterize them (location and dimensions) so that their severity can be assessed, and the mechanical integrity of the welded components guaranteed.
Experimental investigations confirm the challenges and significant shortcomings in the inspection of future industrial components where such microstructures are desirable for their mechanical properties.
First, the methods of fabricating artificial weld defects are investigated. Because of the great variety of possible types of cracks and causes for their formation, the problem of safeguarding against crack formation in welding operations is a highly complex one. The experimental set-up is fabricated to meet these challenges.
Austenitic stainless steel welds are inspected with X-ray radiography (RT) and advanced ultrasonic NDT such as phased array ultrasonic testing (PAUT).
Second, guided wave propagation in elastic structures is discussed. High frequency guided waves within thick structures and along weld geometries are discussed.
Furthermore, the interaction of weld guided waves with defects is examined through Pitch-Catch and Scanning Laser Doppler Vibrometer (SLDV) methods.
The thesis finishes with a comparison between NDT and SHM followed by a summary, conclusions, and suggestions for future work.
... NDE has gained high importance due to the rapid technological progress made during the past decades in areas such as aviation, petrochemical and nuclear industries, where the risks are high and strict precautions are required. Currently, the NDE are employed in manufacturing and in-service inspections with the aim of assuring product integrity and reliability, maintaining their quality and reduction of production costs [3]. ...
Novel approach using swept frequency eddy current technique is employed in non-destructive inspection of conductive materials. Possibility of defect extent evaluation from response signals is experimentally studied. Two plate specimens made of austenitic steel SUS 316L containing artificial electro-discharge machined notches are inspected. The notches vary in dimensions, and they are inspected by two eddy current probes. In particular, a length and a depth dimensions of the notches are concerned here. A wide frequency range is used for the experiments, while the probes containing a transmitting and a receiving coils are located at fixed positions over the plates’ surface during entire inspection. The voltage transfer frequency characteristics of the probes are recorded as the response signals. The frequency range is adjusted in such a way that the electrical resonance is clearly visible from the acquired characteristics. Influences of the defects’ length and depth on the response signals are evaluated in order to investigate possibilities of cracks’ evaluation. The presented results clearly show that the resonance frequency depends on a defect extent.
... Crack is one of the most dangerous process defects in welded joint. Of all the critical inspection techniques used to detect and size real cracks, ultrasonic inspections are most widely used [1]. The estimation of the depth of crack allows a better estimate of the risk which the crack poses to the equipment, which is very important for weld defect ratings. ...
