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This paper explores combining a gimbal-mounted tunable diode laser absorption spectroscopy (TDLAS) sensor and a video camera to create a virtual gas camera for methane leak detection. This provides a low-to-zero-cost extension of typical TDLAS gas tomography systems. A prototype setup mounted on a ground robot is evaluated. Results acquired using a simulated methane leak show the feasibility of the virtual gas camera, accurately detecting methane leaks by overlaying concentrations onto a visual image. While the acquisition time is significantly longer than for traditional gas cameras, potential enhancements are discussed. The study concludes that the virtual gas camera is feasible and useful, despite its longer acquisition time. It serves as a valuable software-only addition to typical TDLAS gas tomography systems, offering quickly-available on-site data augmentation for visual leak assessment at low-to-zero cost.
This paper outlines significant advancements in our previously developed aerial gas tomography system, now optimized to reconstruct 2D tomographic slices of gas plumes with enhanced precision in outdoor environments. The core of our system is an aerial robot equipped with a custom-built 3-axis aerial gimbal, a Tunable Diode Laser Absorption Spectroscopy (TDLAS) sensor for CH4 measurements, a laser rangefinder, and a wide-angle camera, combined with a state-of-the-art gas tomography algorithm. In real-world experiments, we sent the aerial robot along gate-shaped flight patterns over a semi-controlled environment with a static-like gas plume, providing a welldefined ground truth for system evaluation. The reconstructed cross-sectional 2D images closely matched the known ground truth concentration, confirming the system’s high accuracy and reliability. The demonstrated system’s capabilities open doors for potential applications in environmental monitoring and industrial safety, though further testing is planned to ascertain the system’s operational boundaries fully.
This paper explores combining a gimbal-mounted tunable diode laser absorption spectroscopy (TDLAS) sensor and a video camera to create a virtual gas camera for methane leak detection. This provides a low-to-zero-cost extension of typical TDLAS gas tomography systems. A prototype setup mounted on a ground robot is evaluated. Results acquired using a simulated methane leak show the feasibility of the virtual gas camera, accurately detecting methane leaks by overlaying concentrations onto a visual image. While the acquisition time is significantly longer than for traditional gas cameras, potential enhancements are discussed. The study concludes that the virtual gas camera is feasible and useful, despite its longer acquisition time. It serves as a valuable software-only addition to typical TDLAS gas tomography systems, offering quickly-available on-site data augmentation for visual leak assessment at low-to-zero cost.
This paper outlines significant advancements in our previously developed aerial gas tomography system, now optimized to reconstruct 2D tomographic slices of gas plumes with enhanced precision in outdoor environments. The core of our system is an aerial robot equipped with a custom-built 3-axis aerial gimbal, a Tunable Diode Laser Absorption Spectroscopy (TDLAS) sensor for CH4 measurements, a laser rangefinder, and a wide-angle camera, combined with a state-of-the-art gas tomography algorithm. In real-world experiments, we sent the aerial robot along gate-shaped flight patterns over a semi-controlled environment with a static-like gas plume, providing a welldefined ground truth for system evaluation. The reconstructed cross-sectional 2D images closely matched the known ground truth concentration, confirming the system’s high accuracy and reliability. The demonstrated system’s capabilities open doors for potential applications in environmental monitoring and industrial safety, though further testing is planned to ascertain the system’s operational boundaries fully.
Normung und Standardisierung in der zerstörungsfreien Prüfung finden auf nationaler, europäischer und internationaler Ebene statt. Die Übernahme von Leitungsfunktionen in diesen Gremien erzeugt die Möglichkeit der Steuerung von Themen und Inhalte der relevanten Normen. Das persönliche Engagement der Fachexpert*innen in den nationalen Gremien und den europäischen und internationalen Arbeitsgruppen ist ein zusätzlicher Faktor für die inhaltliche Korrektheit und die erwünschte inhaltliche Ausrichtung der Norm. Denn wer nicht normt wird genormt und muss letztlich Regeln verwenden, die andere entsprechend ihrer eigenen Interessen gestalten. Voraussetzung für die Teilnahme in europäischen und internationalen Normungsgremien ist die Mitwirkung in den entsprechenden DIN-Spiegelgremien, welche die europäischen (CEN) und internationalen (ISO) Aktivitäten spiegeln und die Fachexperten für die Mitarbeit autorisieren. Auf internationaler Ebene findet die Normungsarbeit in den technischen Komitees ISO/TC 135 “Non-destructive testing” und ISO/TC 44/SC 5 “Testing and inspection of welds” und ihren Arbeitsgruppen statt. Das europäische Pendant ist das CEN/TC 138 “Zerstörungsfreie Prüfverfahren” mit seinen Arbeitsgremien. Die DIN-Spiegelgremien sind für die deutsche Mitarbeit in diesen Gremien und die inhaltliche Bewertung der Norm-Entwürfe zuständig.
Normung und Standardisierung in der zerstörungsfreien Prüfung finden auf nationaler, europäischer und internationaler Ebene statt. Die Übernahme von Leitungsfunktionen in diesen Gremien erzeugt die Möglichkeit der Steuerung von Themen und Inhalten der relevanten Normen. Das persönliche Engagement der Fachexpert*innen in den nationalen Gremien und den europäischen und internationalen Arbeitsgruppen ist ein zusätzlicher Faktor für die inhaltliche Korrektheit und die inhaltliche Ausrichtung der Norm. Denn wer nicht normt, wird genormt und muss letztlich Normen anwenden, die andere entsprechend ihrer eigenen Interessen gestaltet haben. Voraussetzung für die Teilnahme in europäischen und internationalen Normungsgremien ist die Mitwirkung in den entsprechenden DINSpiegelgremien, welche die europäischen (CEN) und internationalen (ISO) Aktivitäten spiegeln und die Fachexpert*innen für die Mitarbeit autorisieren.
Auf internationaler Ebene findet die Normungsarbeit in den technischen Komitees ISO/TC 135 “Non-destructive testing” und ISO/TC 44/SC 5 “Testing and inspection of welds” und ihren Arbeitsgruppen statt. Das europäische Pendant ist das CEN/TC 138 “Zerstörungsfreie Prüfverfahren” mit seinen Arbeitsgremien. Die DINSpiegelgremien sind für die deutsche Mitarbeit in diesen Gremien und die inhaltliche Bewertung der Norm-Entwürfe zuständig.
Bei der zerstörungsfreien Prüfung verlegter Eisenbahnschienen werden die Rohdaten derzeit in proprietären Datenformaten gespeichert und auf Datenträgern zwischen den Prüfzügen und den auswertenden Stellen versendet. Die proprietären Datenformate sind in der Regel nur den Herstellern der Prüfsysteme bekannt und deren Dokumentation nicht allgemein zugänglich.
Die „Standard Practice for Digital Imaging and Communication in Nondestructive Evaluation“ (DICONDE), basierend auf dem medizinischen Standard „Digital Imaging and Communication in Medicine“ (DICOM), ermöglicht es, sowohl Prüfdaten als auch Prüfergebnisse und Streckeninformationen in einem standardisierten Format zu speichern und zwischen verschiedenen Endpunkten zu übertragen.
Das Poster gibt zunächst einen kurzen Überblick über die hierarchische Struktur von DICONDE und zeigt dann, wie DICONDE bei der Prüfung verlegter Eisenbahnschienen verwendet werden kann. Die geometrischen Besonderheiten (mehrere Kilometer Länge pro Prüffahrt, kurviger Streckenverlauf) stellen dabei eine besondere Herausforderung dar. Im Rahmen des mFUND-geförderten Projektes „Arteficial Intelligence for Railway Inspection (AIFRI)“, Förderkennzeichen 19FS2014C, wurde ein Vorschlag für eine Erweiterung des DICONDE-Standards für die Schienenprüfung erarbeitet und bei der ASTM eingereicht.
Bei der zerstörungsfreien Prüfung verlegter Eisenbahnschienen werden die Rohdaten derzeit in proprietären Datenformaten gespeichert und auf Datenträgern zwischen den Prüfzügen und den auswertenden Stellen versendet. Die proprietären Datenformate sind in der Regel nur den Herstellern der Prüfsysteme bekannt und deren Dokumentation nicht allgemein zugänglich.
Die „Standard Practice for Digital Imaging and Communication in Nondestructive Evaluation“ (DICONDE), basierend auf dem medizinischen Standard „Digital Imaging and Communication in Medicine“ (DICOM), ermöglicht es, sowohl Prüfdaten als auch Prüfergebnisse und Streckeninformationen in einem standardisierten Format zu speichern und zwischen verschiedenen Endpunkten zu übertragen.
Das Poster gibt zunächst einen kurzen Überblick über die hierarchische Struktur von DICONDE und zeigt dann, wie DICONDE bei der Prüfung verlegter Eisenbahnschienen verwendet werden kann. Die geometrischen Besonderheiten (mehrere Kilometer Länge pro Prüffahrt, kurviger Streckenverlauf) stellen dabei eine besondere Herausforderung dar. Im Rahmen des mFUND-geförderten Projektes „Arteficial Intelligence for Railway Inspection (AIFRI)“, Förderkennzeichen 19FS2014C, wurde ein Vorschlag für eine Erweiterung des DICONDE-Standards für die Schienenprüfung erarbeitet und bei der ASTM eingereicht.
Bei der Erhaltung von Stahlbetonbauwerken ist der Chloridgehalt im Beton ein wichtiger Parameter zur Festlegung geeigneter Instandsetzungsmaßnahmen. Die bisher etablierten Verfahren basieren auf der nasschemischen Analyse einer Probe, Bohrmehl oder aufgemahlener Segmente eines Bohrkerns. Das Verfahren liefert einen Chloridgehalt je Tiefensegment, was mit einer starken Homogenisierung der Probe einhergeht, wodurch detaillierte Informationen zu Chloridunterschieden im Millimeterbereich verloren gehen. Eine alternative Methode ist die laserinduzierte Plasmaspektroskopie (LIBS), die nicht nur die quantitative ortsaufgelöste Bestimmung des Chloridgehalts im Bezug zur Zementmasse ermöglicht, sondern auch simultan detaillierte Informationen über die Verteilung vieler anderer chemischer Elemente liefert. Die räumliche Auflösung liegt in der Regel im Bereich von einigen Millimetern, kann aber bei Bedarf auf 0,1 mm oder weniger erhöht werden. Das neue Merkblatt B14 „Quantifizierung von Chlorid in Beton mit der laserinduzierten Plasmaspektroskopie (LIBS)“ der Deutschen Gesellschaft für Zerstörungsfreie Prüfungen (DGZfP) regelt und vereinheitlicht erstmals die zuverlässige und reproduzierbare Ermittlung des Chloridgehalts mit LIBS. In diesem Beitrag wird das Merkblatt vorgestellt und anhand praktischer Anwendungsbeispiele das Potenzial von LIBS für Fragestellungen in der Betonerhaltung verdeutlicht.
This technical note highlights the fact that CF-LIBS algorithms work in mole fractions, while results of spectrochemical analysis are usually reported in mass fractions or mass percent. Ignoring this difference and not converting mole fractions to mass fractions can lead to errors in reported concentrations determined by the CF-LIBS method and inadequate comparison of these concentrations with certified concentrations. Here, the key points of the CF-LIBS algorithm are reproduced and the formulae for converting a mole fraction to a mass fraction and vice versa are given. Several numerical examples are also given, which show that the greater the difference between the molar mass of an individual element in a sample and the average molar mass, the greater the discrepancy between the mole and mass fractions.
An observation of the fracture process in front of the crack tip inside a dentin sample by means of ex-situ X-ray computed tomography after uniaxial compression at different deformation values was carried out in this work. This ex-situ approach allowed the microstructure and fracturing process of human dentin to be observed during loading. No cracks are observed up to the middle part of the irreversible deformation in the samples at least visible at 0.4μm resolution. First cracks appeared before the mechanical stress reached the compression strength. The growth of the cracks is realized by connecting the main cracks with satellite cracks that lie ahead of the main crack tip and parallel its trajectory. When under the stress load the deformation in the sample exceeds the deformation at the compression strength of dentin, an appearance of micro-cracks in front of the main cracks is observed. The micro-cracks are inclined (~60°) to the trajectory of the main cracks. The further growth of the main cracks is not realized due to the junction with the micro-cracks; we assume that the micro-cracks dissipate the energy of the main crack and suppressed its growth. These micro-cracks serve as additional stress accommodations, therefore the samples do not break apart after the compression test, as it is usually observed under bending and tension tests.
AbstractAir‐coupled ultrasonic testing (ACU) is a pioneering technique in non‐destructive testing (NDT). While contact testing and fluid immersion testing are standard methods in many applications, the adoption of ACU is progressing slowly, especially in the low ultrasonic frequency range. A main reason for this development is the difficulty of generating high amplitude ultrasonic bursts with equipment that is robust enough to be applied outside a laboratory environment. This paper presents the fluidic ultrasonic transducer as a solution to this challenge. This novel aeroacoustic source uses the flow instability of a sonic jet in a bistable fluidic switch to generate ultrasonic bursts up to 60 kHz with a mean peak pressure of 320 Pa. The robust design allows operation in adverse environments, independent of the operating fluid. Non‐contact through‐transmission experiments are conducted on four materials and compared with the results of conventional transducers. For the first time, it is shown that the novel fluidic ultrasonic transducer provides a suitable acoustic signal for NDT tasks and has potential of furthering the implementation of ACU in industrial applications.This article is protected by copyright. All rights reserved
In ultrasonic testing, material and structural properties of a specimen can be derived from the time-of-flight (ToF). Using signal features, such as the first peak or envelope maximum, to calculate the ToF is error-prone in multipath arrangements or dispersive and attenuating materials, which is not the case for the signal onset. Borrowing from seismology, researchers used the Akaike information criterion (AIC) picker to automatically determine onset times. The most commonly used formulation, Maeda's AIC picker, is reassessed and found to be based on inappropriate assumptions for signals often used in ultrasonic testing and dependent on arbitrary parameters. Consequently, an onset picker for ultrasonic through-transmission measurements is proposed, based on a spectral entropy criterion (SEC) to model the signal using the AIC framework. This SEC picker takes into account the spectral properties of the ultrasonic signal and is virtually free of arbitrary parameters. Synthetic and experimental data are used to compare the performance of SEC and AIC pickers. It is shown that the accuracy of onset picking is improved for densely sampled data.
AbstractHigh-strength aluminum alloys used in aerospace and automotive applications obtain their strength through precipitation hardening. Achieving the desired mechanical properties requires precise control over the nanometer-sized precipitates. However, the microstructure of these alloys changes over time due to aging, leading to a deterioration in strength. Typically, the size, number, and distribution of precipitates for a quantitative assessment of microstructural changes are determined by manual analysis, which is subjective and time-consuming. In our work, we introduce a progressive and automatable approach that enables a more efficient, objective, and reproducible analysis of precipitates. The method involves several sequential steps using an image repository containing dark-field transmission electron microscopy (DF-TEM) images depicting various aging states of an aluminum alloy. During the process, precipitation contours are generated and quantitatively evaluated, and the results are comprehensibly transferred into semantic data structures. The use and deployment of Jupyter Notebooks, along with the beneficial implementation of Semantic Web technologies, significantly enhances the reproducibility and comparability of the findings. This work serves as an exemplar of FAIR image and research data management.
A semi-automatic thermographic procedure for the assessment of the welded area of resistance projection welded joints has been developed. Currently, to assess the quality of RPW joints destructive tests are used and the more commonly used non-destructive technique is the ultrasonic one. The possibility for a quantitative evaluation of the welded area by thermographic technique has been proved by means of an innovative procedure applied on steel RPW joints with ‘as it’ surface conditions. Measurements obtained by thermography and ultrasound have been compared, to verify the developed procedure.
Simulation-Assisted Augmentation of Missing Wedge and Region-of-Interest Computed Tomography Data
(2024)
This study reports a strategy to use sophisticated, realistic X-ray Computed Tomography (CT) simulations to reduce Missing Wedge (MW) and Region-of-Interest (RoI) artifacts in FBP (Filtered Back-Projection) reconstructions. A 3D model of the object is used to simulate the projections that include the missing information inside the MW and outside the RoI. Such information augments the experimental projections, thereby drastically improving the reconstruction results. An X-ray CT dataset of a selected object is modified to mimic various degrees of RoI and MW problems. The results are evaluated in comparison to a standard FBP reconstruction of the complete dataset. In all cases, the reconstruction quality is significantly improved. Small inclusions present in the scanned object are better localized and quantified. The proposed method has the potential to improve the results of any CT reconstruction algorithm.
Until the 1980s radiography was used to inspect civil structures in case of special demands and showed a much better resolution than other NDT techniques. However, due to safety concerns and cost issues, this method is almost never used anymore. Meanwhile, non-destructive techniques such as ultrasound or
radar have found regular, successful practical application but sometimes suffer from limited resolution and accuracy, imaging artefacts or restrictions in detecting certain features when applied to reinforced or prestressed concrete inspection.
Muon tomography has received much attention recently. Muons are particles generated naturally by cosmic rays in the upper atmosphere and pose no risk to humans. Novel detectors and tomographic imaging algorithms have opened new fields of application, mainly in the nuclear sector, but also in spectacular cases such as the Egyptian pyramids.
As a first step towards practical application in civil engineering and as a proof of concept we used an existing system to image the interior of a reference reinforced 600 kg concrete block. Even with a yet not optimized setup for this kind of investigation, the muon imaging results have been at least of similar quality compared to ultrasonic and radar imaging, potentially even better. Recently, the research was expanded to more realistic testing problems such as the detection of voids in certain structural elements. However, before practical implementation, more robust, mobile, and affordable detectors would be required as well as user-Friendly imaging and simulation software.
The built infrastructure ages and requires regular inspection and, when in doubt, monitoring. To ensure that older concrete bridges showing signs of deterioration can be used safely, several innovative monitoring tools have been introduced, including but not limited to optical, fiber-optic, or acoustic emission techniques. However, there are gaps in the portfolio. A sensing technique that covers a wide range of damage scenarios and larger volumes, while still being sensitive and specific, would be beneficial.
For about 15 years, research has been conducted on ultrasonic monitoring of concrete structures that goes beyond the traditional ultrasonic pulse velocity test (PV test), mostly using a very sensitive data evaluation technique called coda wave interferometry. At BAM we have developed sensors and instrumentation specifically for this method.
We have instrumented a 70-year-old, severely damaged prestressed concrete bridge in Germany in addition to a commercial monitoring system. We have now collected data for almost 3 years. We can show that we can provide information about the stress distribution in the bridge. We have also been able to confirm that there has been no significant additional damage to the bridge since the installation.
X-rays without X-rays: Can muon tomography provide pictures from within concrete and other objects?
(2024)
Until the 1980s radiography was used to inspect civil structures in case of special demands and showed a much better resolution than other NDT techniques. However, due to safety concerns and cost issues, this method is almost never used anymore. Meanwhile, non-destructive techniques such as ultrasound or
radar have found regular, successful practical application but sometimes suffer from limited resolution and accuracy, imaging artefacts or restrictions in detecting certain features when applied to reinforced or prestressed concrete inspection.
Muon tomography has received much attention recently. Muons are particles generated naturally by cosmic rays in the upper atmosphere and pose no risk to humans. Novel detectors and tomographic imaging algorithms have opened new fields of application, mainly in the nuclear sector, but also in spectacular cases such as the Egyptian pyramids.
As a first step towards practical application in civil engineering and as a proof of concept we used an existing system to image the interior of a reference reinforced 600 kg concrete block. Even with a yet not optimized setup for this kind of investigation, the muon imaging results have been at least of similar quality compared to ultrasonic and radar imaging, potentially even better. Recently, the research was expanded to more realistic testing problems such as the detection of voids in certain structural elements. However, before practical implementation, more robust, mobile, and affordable detectors would be required as well as user-Friendly imaging and simulation software.
The talk also discusses other applications , such as volcanology, mining and geothermal exploration.