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Many laboratories have been working about Active Thermography
as a Non Destructive Testing method for many
years. This method can be applied on metallic or composites
materials for surface or subsurface defects. Thus, many
different configurations can be encountered to measure the
heat distribution and generate heat flow into the part. Signal
processing is also widely used to improve the performance
of detection.
After encouraging results, aerospace, automotive and energy
industries are now involved into industrialization of the
technology to apply it for production or maintenance applications.
Good practices and common wording are often
required by end-user to qualify the process.
Since the beginning of the 2000s, a working group was
founded within CEN/TC138 'Non-destructive Testing' to define standards in thermography, in the European Committee
for Standardization (CEN). Some other actors have also produced
standards (ISO, IEC, ASTM...).
This paper aims to list the standards currently available about
thermography and the associatd vocabulary. It describes
the generic terms to be used in active and passive thermography
(operating modes, reference blocks, reporting…) and
also more specific elements about laser and induction thermography
for example.
It will also put in perspective the further works to be done
in the next few years to take into account the new trends in
active thermography and how to qualify for industrial applications.
The energy transition towards hydrogen utilisation has increased the demand for reliable testing methods to evaluate the susceptibility of metallic materials to hydrogen degradation. However, traditional electrochemical pre-charging techniques have limitations in represent-ing realistic gaseous hydrogen exposure conditions. This study presents three comparative analyses of tensile testing methodologies, focusing on the differences between electrochem-ical pre-charging, gaseous pre-charging, and in-situ testing using hollow specimens for aus-tenitic steels AISI 304L and 316L type austenitic steels.
Based on the results obtained, the first comparison reveals that electrochemically pre-charged and gaseously pre-charged specimens exhibit different behaviours regarding the impact on the mechanical properties. This effect can be retraced to the varying distribution of hydrogen throughout the specimens. Although comparable embrittlement was observed for similar hydrogen concentrations, the relationship appears to be non-systematic.
The second comparison evaluates the performance of pre-charged hollow specimens (300°C, 100 bar, 21 days) in comparison to hollow specimens tested in-situ under 200 bar hydrogen during slow strain rate tensile tests (SSRT). While pre-charged specimens show a slight de-crease in elongation at fracture and a noticeable decrease in reduction of area (RA), in-situ tested specimens exhibit significantly more pronounced embrittlement. This is in accord-ance with the results of Michler et. al.
In the third comparison, geometry effects between pre-charged conventional and pre-charged hollow specimens are explored. In this case, the hydrogen effect appears to be of the same order of magnitude for both specimen types, although some differences are ob-served.
The study's findings underscore the importance of considering differences between test methods when assessing materials’ compatibility with hydrogen. It specifically emphasises the need for in-situ testing with gaseous hydrogen to better represent real conditions in ap-plications within the hydrogen sector. Furthermore, the study provides an initial compari-son between conventional and hollow specimens, demonstrating their capability to reveal hydrogen effects. However, additional research is essential to enhance the comparability of results yielded by these testing methods.
Eurachem is an international network of national organisations having the objective of establishing a system for the international traceability of chemical measurements and the promotion of good quality practices. It also provides a forum for discussing common problems and exchanging information on quality assurance issues in analytical chemistry. The presentation will explain how Eurachem is organised, the requirements for participation and the opportunities for collaboration and networking. In particular, it will discuss why Eurachem offers an interesting network for young scientists to exchange experiences and further their own education.
Robotic-assisted 3D scanning and laser thermography for crack inspection on complex components
(2024)
The integration of automation and robotics into inspection processes has marked a transformative shift in the evaluation of complex components. This study presents a novel approach employing robotic-assisted laser thermography for the automated identification and in-depth analysis of cracks in these intricate structures. This method not only streamlines the inspection process but also eliminates the need for numerous manual steps and the use of chemicals associated with traditional methods such as dye penetrant testing. With the increasing com-plexity of components, this is an important step, especially with regard to additively manufactured components, in order to be able to guarantee component safety for a long lifecycle.
Many laboratories have been working about Active Thermography as a Non Destructive Testing method for many years. This method can be applied on metallic or composites materials for surface or subsurface defects. Thus, many different configurations can be encountered to measure the heat distribution and generate heat flow into the part. Signal processing is also widely used to improve the performance of detection. After encouraging results, aerospace, automotive and energy industries are now involved into industrialization of the technology to apply it for production or maintenance applications. Good practices and common wording are often required by end-user to qualify the process. Since the beginning of the 2000s, European Committee for Standardization (CEN) has launched a Working Group within CEN/TC138 to define standards in thermography. Some other actors have also produced standards (ISO, IEC, ASTM,..). This goal of this presentation is to present a status of the standard currently available about thermography and the associated vocabulary. It describes the generic terms to be used in active and passive thermography (operating modes, reference blocks, reporting,…) and also more specific elements about laser and induction thermography for example. It will also put in perspective the further works to be done in the next few years to take into account the new trends in active thermography and how to qualify for industrial applications.
The transition to a decarbonised economy will require large amounts of hydrogen over a broad variety of applications. The use of hydrogen poses high safety requirements as hydrogen can be absorbed by metallic materials and result in hydrogen embrittlement under certain condi-tions. For this reason, interactions of gaseous hydrogen and metallic materials are of high sci-entific and industrial interest. Slow strain rate tensile (SSRT) tests are commonly used to evaluate the hydrogen-induced ductility loss of alloys. However, the current standardised test method describes a complex and expensive procedure with limited availability worldwide. The hollow specimen technique promises huge potential for scaling suitable in-situ testing infra-structure and is currently under intensive development in several institutes around the world. As this method has only gained significant attention in the last decade, there are varying interpretations, particularly when testing materials with vastly different mechanical properties. Most available literature focuses on common steels used in hydrogen and natural gas piping systems. The present work provides an overview of the widespread applicability of hollow specimens in evaluating the effect of high-pressure hydrogen on the tensile properties of vari-ous metallic materials. The research presented includes Near-Net shape produced additively manufactured (AM) AISI 316 L, ferritic X65 steel, its weld seam, and solution annealed and hardened 100Cr6 steel.
Forschungsprojekt "INSIST"
(2024)
Der Vortrag zeigt den Bearbeitungsstand des Forschungsvorhabens "Entwicklung eines Verfahrens zur in situ Bewertung des Feuerwiderstands von bestehenden Stahlkonstruktionen mit reaktiven Brandschutzsystem (RBS)" (INSIST). Die Entwicklung und der Bau eines Geräteprototyps wurden vorgenommen und ein Konzept zur Kalibration erarbeitet. Die bisherigen Untersuchungen belegen, dass das Verfahren Ergebnisse liefert, die denen konventioneller Brandversuche im untersuchten Parameterbereich gleichwertig sind.
Nickel-based alloys have been widely used for gas turbine blades owing to their excellent mechanical properties and corrosion resistance at high temperatures. The operating temperatures of modern gas turbines have been increased in pursuit of increased thermal efficiency. Turbine blades are exposed to these high temperatures combined with mechanical stresses, resulting in material damage through creep, fatigue, and other mechanisms. These turbine blades must be regularly inspected and replaced as needed, to prevent the loss of efficiency, breakdown, and catastrophic failure. Repair of the damaged turbine blades is often a more practical and cost-effective option than replacement, as replacement is associated with high costs and loss of material resources. To this end, state-of-the-art repair technologies including different additive manufacturing and brazing processes are considered to ensure efficient repair and optimum properties of repaired components.
In any repaired part, materials property-mismatches and/or inner defects may facilitate the crack initiation and propagation and thus reduce the number of load cycles to failure. Therefore, a fundamental understanding of the fatigue crack growth and fracture mechanisms in joining zones is required to enable the prediction of the remaining life of repaired components and to further improve and adapt the repair technologies.
Fatigue crack growth experiments have been conducted on SEN (Single Edge Notch) specimens joined via brazing, and pre-sintered Preform (PSP) and multi-materials (casted/printed) specimens layered via additive manufacturing (AM). The experiments were performed at 950 °C and various stress ratios. The crack growth was measured using DCPD (Direct Current Potential Drop) method. The stress intensity factors for joined SEN specimens were calculated using the finite element method and then used to derive the fatigue crack growth curves. Metallographic and fractographic analyses were conducted to get insight into the fracture mechanism.
Results show that the experimental technique for fatigue crack growth was successfully adapted and applied for testing joined specimens. Furthermore, the initial tests indicate that the investigated braze filler material provides a lower resistance to crack growth, and bonding defects cause a crack to deviate to the interface of the base material and joining zone. In AM-sandwich specimens, the crack growth rates are significantly reduced when the crack reaches the interface of printed material and casted material. The obtained crack growth data can be used to calibrate a crack growth model, which will further be utilized to predict the remaining life of repaired components.
Nickelbasierte Superlegierungen werden in großem Umfang für Gasturbinenschaufeln verwendet, da sie einer Kombination aus hoher Belastung und hohen Temperaturen widerstehen können. Um die Effizienz moderner Gasturbinen zu verbessern, werden hohe Betriebstemperaturen angestrebt. Diese hohen Temperaturen verbunden mit mechanischen Belastungen führen zu Materialschäden aufgrund von Kriechen, Ermüdung und anderen Schadensmechanismen. Aus diesem Grund werden Turbinenschaufeln regelmäßig im Rahmen von Wartungs- und Instandsetzungsmaßnahmen geprüft und falls erforderlich ausgetauscht, um ein katastrophales Versagen im Betrieb zu vermeiden. Ein kompletter Austausch ist mit sehr hohen Kosten verbunden, weshalb geeignete Reparaturverfahren entwickelt wurden und werden. Neue Reparaturtechnologien wie die Additive Fertigung, Lötverfahren und der Einsatz von vorgesinterten Vorformen (Presintered Preform PSP) sollen eine effiziente Reparatur und optimale Eigenschaften der reparierten Bauteile sichterstellen.
Im Allgemeinen stellen die Fügezonen typische Schwachstellen dar, da sie die Anrissbildung und Rissausbreitung erleichtern und die Anzahl der Lastzyklen bis zum Bruch reduzieren können. Aus diesem Grund ist eine umfassende Untersuchung des Rissfortschrittsverhaltens in diesen, durch neue Reparaturtechnologien entstandenen Bereichen erforderlich, um die Restlebensdauer der Turbinenschaufeln vorherzusagen.
Als ein erster Beitrag zu dieser Fragestellung werden Ergebnisse von Rissfortschrittsversuchen (Fig. 1) an SENT-Proben vorgestellt, die durch Engspaltlöten gefügt wurden. Die Versuche wurden bei einer Temperatur von 950 °C und einem Spannungsverhältnis R = 0,1 durchgeführt. Die Erfassung des Rissfortschritts erfolgte mit dem Gleichstrom-Potentialsonden-Verfahren. Mit der Finite-Element-Methode konnte der Spannungsintensitätsfaktor für gefügte SENT-Proben berechnet werden, der dann zur Berechnung der Risswachstumskurven verwendet wurde. Eine abschließende licht- und rasterelektronenmikroskopische Untersuchung der Bruchflächen soll einen Beitrag zum Verständnis der Bruchmechanismen liefern und klären, ob der Riss sich im Lotwerkstoff, im Grundwerkstoff oder in der Grenzfläche ausbreitet. Die Ergebnisse werden zur Kalibrierung des Rissfortschrittsmodells und der Auslegung zukünftiger Komponenten verwendet.
Photon-based additive manufacturing technologies such as SLA, DLP, LCM, moreover volumetric two-photon-polymerization, Xolography and holographic technologies promise the highest accuracy and dimensional freedom. But to transfer the light through the feedstock it needs sufficient transparency at the used light wavelength. Ceramic particles used for powder processing routes act as scattering sites and therefore hinder the light transmission, unless…
The particle size and particle size distribution are chosen small and narrow enough. Particles which are smaller than roughly 1/10th of the light wavelength, mostly nanoparticles around 5nm size, decrease scattering vastly. This turns resins even with homogeneously distributed ceramic weight fraction of up to 80% transparent again. Feedstocks could be prepared for the highly accurate two-photon-polymerization gaining the smallest yttria stabilized zirconia structures with a resolution of 500nm and unique mechanical properties. The same feedstocks could be applied to DLP and LCM as layer-by-layer AM-technologies for bigger parts. Hybridizing both technologies lead to ceramic parts with microscopic accuracy at macroscopic dimensions. The feedstock was even applied to the volumetric Xolography with the highest transparency requirement so far and to versatile and flexible holographic AM.
Highly filled nano-particle containing transparent ceramic feedstocks open the way for technical ceramics in high precision manufacturing where the performance and durability and accessibility are increased and created by the unique ceramic properties such as mechanical strength, chemical and thermal resistance and biocompatibility
In order to be able to manipulate ceramic powder compacts and ceramic suspensions (slurries) in their volume with light, a minimum transparency of the materials is required. Compared to polymers and metals, ceramic materials are characterized by the fact that they have a wide electronic band gap and therefore a wide optical window of transparency. The optical window generally ranges from less than 0.3 µm to 5 µm wavelength. Therefore, to focus light into the volume of a ceramic powder compact, its light scattering properties need to be tailored. In this study, we present the physical background and material development strategies for the application of two-photon polymerization (2PP), Xolography and selective volumetric sintering for the additive manufacturing of structures in the volume of ceramic slips and green compacts.
Nickel-based alloys have been widely used for gas turbine blades owing to their excellent mechanical properties and corrosion resistance at high temperatures. The operating temperatures of modern gas turbines have been increased in pursuit of increased thermal efficiency. Turbine blades are exposed to these high temperatures combined with mechanical stresses, resulting in material damage through creep, fatigue, and other mechanisms. These turbine blades must be regularly inspected and replaced as needed, to prevent the loss of efficiency, breakdown, and catastrophic failure. Repair of the damaged turbine blades is often a more practical and cost-effective option than replacement, as replacement is associated with high costs and loss of material resources. To this end, state-of-the-art repair technologies including different additive manufacturing and brazing processes are considered to ensure efficient repair and optimum properties of repaired components.
In any repaired part, materials property-mismatches and/or inner defects may facilitate the crack initiation and propagation and thus reduce the number of load cycles to failure. Therefore, a fundamental understanding of the fatigue crack growth and fracture mechanisms in joining zones is required to enable the prediction of the remaining life of repaired components and to further improve and adapt the repair technologies.
Fatigue crack growth experiments have been conducted on SEN (Single Edge Notch) specimens joined via brazing, and pre-sintered Preform (PSP) and multi-materials (casted/printed) specimens layered via additive manufacturing (AM). The experiments were performed at 950 °C and various stress ratios. The crack growth was measured using DCPD (Direct Current Potential Drop) method. The stress intensity factors for joined SEN specimens were calculated using the finite element method and then used to derive the fatigue crack growth curves. Metallographic and fractographic analyses were conducted to get insight into the fracture mechanism.
Results show that the experimental technique for fatigue crack growth was successfully adapted and applied for testing joined specimens. Furthermore, the initial tests indicate that the investigated braze filler material provides a lower resistance to crack growth, and bonding defects cause a crack to deviate to the interface of the base material and joining zone. In AM-sandwich specimens, the crack growth rates are significantly reduced when the crack reaches the interface of printed material and casted material. The obtained crack growth data can be used to calibrate a crack growth model, which will further be utilized to predict the remaining life of repaired components.
This talk presents the EU funded project PlasticTrace. It shows the challenges in micro- and nanoplastic reference materials and gives some solutions regarding spectroscipc methods such as Raman or IR microscopy to determine the particle numbers. Materials are prepared by cryo milling to get some powder that is later pressed into tablets. The polymer type used is PET, because that is highly important for drinking water directive of EU commission.
Protection against terrorist or accidental scenarios in industrial settings requires suitable designs of structures to resist blast loads. Field testing as well as finite element simulations are among the techniques available to engineers in the understanding of the structural behavior against blast loading. As blast testing of complex scenarios can be very resource intensive, tests are generally performed for simplified scenarios. Numerical tools can be used to model these scenarios in order to get a better insight into blast loading, structural response and the resulting damage to the structure. In the next steps, the simplified scenario is successively modified in numerical simulations to incorporate complexities that cannot be covered in blast testing experiments. One of the conditions for this approach to work is that the original simplified numerical simulation is valid. The scopes and challenges encountered in such a validation are the focus of this presentation. A relatively ‘simple’ field test of a horizontal reinforced concrete (RC) slab subjected to blast loading is taken as an example for validation of the performance of numerical tools. The blast test incorporated various measurement techniques to quantify the blast load as well as the behavior of the RC slab. Blast load was measured using flush-mounted piezoelectric pressure gauges, whereas acceleration sensors and fiber-optic sensor cables were used to characterize the dynamic behavior of the slab under blast loading. Additionally, damage characteristics were ascertained also using fiber-optic sensing. The application of such measurement techniques, along with different numerical software available for the analysis of the scenario in question,
demonstrate the scope of our contribution.
Traceable morphological and chemical characterization of nanomaterials with respect to the various possible sizes, size distributions, shapes, and concentrations of real-world nanoparticles (NPs) is a challenging task. Particularly for the nonspherical, non-monodisperse nanoparticles – as typically for most of the commercial particles, including their strong tendency to agglomerate, there is a lack of standard operation procedures providing accurate nanoparticle characterisation.
In the framework of the pre-standardisation framework of VAMAS (Versailles Project on Advanced Materials and Standards, www.vamas.org) two interlaboratory comparison (ILC) studies are being carried out under the Technical Working Area (TWA) 34 “Nanoparticle Populations”:i) Project #15 addresses the analysis of the size and shape distribution of TiO2 bipyramidal NPs by traceable imaging methods such as TEM, SEM, STEM-in-SEM, AFM as well as with SAXS as an ensemble method. This ILC is thought as the next level development of the case studies exemplified in the published ISO standards ISO 21363 and ISO 19749. It was agreed to complete the first ILC with the NPs already prepared according to the same procedure on a TEM grid, and, at a later stage, to carry out second ILCs with the same NPs distributed to the participants as liquid suspensions together with protocols for the uniform NP deposition on suited substrates - as developed and optimized within the European project nPSize. Once having good deposition protocols available, the door for automated image analysis gets opened. Corresponding image analysis protocols and reporting templates have been distributed to the ILC participants, too.
ii) Project #16: two spherical SiO2 NP samples with bi-modal size distributions in two nominal relative number concentrations were prepared and distributed also as liquid suspensions accompanied by sample preparation, measurement, and image analysis protocols and reporting templates. Here, the NP concentration is the primary parameter to be measured. For the imaging methods it is targeted to
measure the relative nanoparticle concentrations (relative populations of the two modes).
The results of all the participating laboratories, in both ILCs, compiled in comparative representations will be shown and discussed for the first time. The reduction of the measurement uncertainties associated to the size, shape and number-concentration results induced by the significant improvement of the sample preparation on substrates (as single particles with a high-density coverage), combined with well-defined image analysis procedures will be highlighted.
Finally, a very recent 3rd ILC an the determination of lateral size of Graphene Oxide flakes by SEM is presented as project P13 under VAMAS TWA41 Graphene and Related 2D.
Bonds and local atomic environments are crucial descriptors of material properties. They have been used to create design rules and heuristics and as features in machine learning of materials properties. Implementations and algorithms (e.g., ChemEnv and LobsterEnv) for identifying local atomic environments based on geometrical characteristics and quantum-chemical bonding analysis are nowadays available. Fully automatic workflows and analysis tools have been developed to use quantum-chemical bonding analysis on a large scale. The lecture will demonstrate how our tools, that assess local atomic environments and perform automatic bonding analysis, help to develop new machine learning models and a new intuitive understanding of materials. Furthermore, the general trend toward automation in computational materials science and some of our recent contributions will be discussed.
Many organisations are being driven towards employing sustainable practices to counteract the growing concerns of environmental and social issues. With various stakeholders including governments, suppliers and customers putting on pressure the process industry is no exception. However, many industrial firms struggle to implement sustainability measures. One of the usual first steps when conducting implementation is to analyse the current situation. For this analysis, indicators are commonly used to measure, monitor, and report a company’s sustainable development performance. However, the selection of appropriate indicators is often challenging due to the current lack of relevant methodologies, guidelines, and insights into a practitioner perspective.
To address this challenge, this work focuses on the creation of a user-orientated method, which helps practitioners in the process industry to select relevant indicators for their plant and assist in the deduction of sustainability measures. This includes addressing the difficulties of implementation and regarding the current needs like the inclusion of indicators for reporting or the quantification of gathered metrics.
The presentation is divided into two parts. The first part is about the influence of the oxygen content to results testing the oxygen compatibility. BAM performed tests with several nonmetallic sealing materials such as PTFE, PA 6.6, and EPDM with different oxygen contents between 21 Vol% and pure oxygen. Using the standardized oxygen pressure surge tester, the results have shown, that even a small increase in the oxygen content above 21% in air is associated with a significant reduction on the maximum test pressure at which no reaction of the material occurs. Using the standardized tester to determine the autogenous ignition temperature of the materials in oxygen, the results have shown, that even a small increase in the oxygen content above 21% in air is associated with a significant reduction on the autogenous ignition temperature at which the material shows self-ignition without an additional ignition source. The second part of the presentation is about the oxygen endurance test according to DIN EN ISO 10297, which is generally performed with air or with nitrogen. However, BAM performed this test with oxygen. In some cases, different test results were found: Valves failed the endurance test with oxygen but passed the endurance test with air. Based on the results with different oxygen content and with the oxygen endurance tester, it is unclear, why materials and valves for oxygen are still not consistently tested with oxygen.
Motivation: A precise diagnosis of atherosclerosis is of clinical importance, since cardiovascular disease remain one of the leading causes of death worldwide.
Goal(s): The goal of this study was to evaluate the feasibility of characterizing a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS4) using molecular magnetic resonance imaging in a preclnical model of atherosclerosis.
Approach: Molecular magnetic resonance imaging using a novel probe targeted against ADAMTS4 was used in a high-fat murine model.
Results: It was possible to image atherosclerotic lesions in a mouse model using an ADAMTS4- specific probe for magnetic resonance imaging.
Impact: Using molecular MRI targeting ADAMTS4 is a promising method for characterization of plaque composition and could possibly impact plaque vulnerability assessment in the diagnosis and treatment of atherosclerosis in patients.
In this paper we present a new hydrogen-based test rig for an ongoing feasibility study of using hydrogen as an energy source for the thermal testing of transport packages containing radioactive materials. The test rig will be capable of combusting hydrogen for a wide range of different burner geometries, mass flows and if necessary hydrogen blends. As this type of fire test according to the IAEA boundary conditions does not yet exist, a large number of preliminary investigations, safety assessments and calculations must be carried out in order to develop a viable concept for hydrogen fires. In the first step of the feasibility study, the temperature, structure, and radiation of various hydrogen flames are surveyed. In future works, the results will make it possible to design burner frames that are suitable for fire reference tests in order to make comparisons with pool and propane fires used in assessment procedures today. In parallel comparative numerical simulations are conducted to model the thermal behaviour of hydrogen flames using the software package Ansys®. On the one hand, the numerical simulations support the experiments by providing an overview of numerous parameters and the measuring range; on the other hand, they will help with the design of the burner frame in future work. This paper gives an overview in the design and capabilities of the test rig. Furthermore, the results of the parameter studies show that burner geometry and mass flow provide a significant design margin for the thermal shape of the hydrogen flames. In addition, the results of the initial numerical calculations will be used to determine the necessary sensors, the positions, and their operating range. Only the optimal interaction allows a controlled system that permits user-defined hydrogen fires.