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DICONDE: Enabling FAIR Data and Communication in NDE 4.0
No full textFor the digital transformation and the integration of NDE into the Industry 4.0,
standardized data formats and communication interfaces are mandatory. The
Standard Practice for Digital Imaging and Communication in Nondestructive
Evaluation (DICONDE), based on Digital Imaging and Communication in Medicine (DICOM), offers both a standardized data format and standardized communication interfaces. Furthermore, DICONDE meets the requirements of the EU Data Act by supporting the FAIR data principle (findable, accessible, interoperable, and reusable data).
DICONDE standards are available for radiography including computed
tomography, ultrasonic, and eddy current testing. Standards for thermography
and secondary capture are under development. The basic concept of DICONDE, storage of eddy current and ultrasonic raw data, and the use case of railway rail inspection at the AIFRI project are discussed in detail
Flexural behavior of hollow HPC beams with cross-wound CFRP shear reinforcement
No full textThis article presents cross-wound carbon fiber-reinforced polymer (CFRP) shear reinforcement of hollow high-performance concrete (HPC) beams. A removable mold used to form the core of the hollow elements was utilized for reinforcement positioning. Basalt fiber-reinforced polymer (BFRP) tensile reinforcement was attached to the removable mold by spacers, and the CFRP shear reinforcement was cross-wound around the BFRP bars from carbon rovings oriented at ± 45° from the longitudinal axis. The flexural, and shear performance of the hollow HPC structural beams was evaluated. To set a comparison, specimens without any shear reinforcement and specimens made of HPC with 80 kg/m3 of dispersed short steel fibers were tested alongside them. The shear capacity of the specimens with CFRP reinforcement evaluated in a three-point bending test was up to 73 % higher compared to those with dispersed steel fibers. The cross-wound CFRP reinforcement also complemented the BFRP tensile reinforcement, as for specimens that failed in tension, the ones with CFRP reinforcement achieved 25 % higher ultimate flexural strength compared to those with dispersed steel fibers. The inclined CFRP mesh affected the orientation of the critical shear crack resulting in higher shear capacity at a longer shear span. Direct effect of the longitudinal reinforcement ratio on the shear capacity was observed
Analysis of intact and damaged (floating) slab tracks by finite-element boundary-element models and by measurements
No full textThe damage detection and repair control have become important tasks for slab tracks. Different intact and damaged slab tracks have been investigated theoretically and experimentally for train passages and hammer impacts. The following damages have been considered: The loss of contact between the sleeper and the track slab, between the track slab and the base slab, and between the base slab and the base layer. At first, a slab track with a gap between the track slab and the base layer has been calculated by the combined finite-element boundary-element method which correctly incorporates the behaviour of the infinite soil. The basic results are the track displacements of the rail, the track slab, and the base layer along the track which are caused by a single axle load. These solutions are properly superposed for to get the complete train load. The influence of track and soil parameters and of the track damage has been analysed. For the intact track, the compliance of the soil is dominant whereas the track bending stiffness becomes more important for the damaged track. By comparing the calculated results with the measurements, the length of the gap could be quantified. A slab track with a loose sleeper (without contact to the supporting track slab) was analysed by the transfer function between the displacements and the hammer force (receptance functions) where a resonance appeared in case of the damage. Differences between the different track elements confirmed the detection of the damage. A floating slab track with a thin rubber layer has been investigated for a possible gap between the base slab and the base layer. The behaviour of the intact track has been calculated by a wavenumber-domain method, and the same behaviour has been found in the measurements at several track sections, indicating that there is no damage. Finally, a floating slab track with steel springs and viscous fluid dampers has been measured in the Tongji laboratory. The modes of the floating track slab and the transfer function with corresponding resonances have been calculated and successfully compared with results from wheelset drop tests
Additive Manufacturing with In-situ Measurement and Closed-loop Control for the Powder Flow in Laser Metal Deposition
No full textThe powder mass flow rate is one of the three main factors directly influencing geometry and quality in the Additive Manufacturing (AM; also 3D printing) process of Laser Metal Deposition (LMD), also known as Directed Energy Deposition (DED-LB/M). However, the pneumatic transport of the metal powder lacks stability, repeatability, and traceability. There is currently no reliable in-situ measurement of the mass flow rate available in industry. As a result, time-consuming powder flow measurements before the manufacturing are typical while no recording or feedback takes place during the manufacturing. Based on this problem statement, this thesis introduces a holistic approach for in-situ measurement and closed-loop control of pneumatic powder flows. For the in-situ measurement, a widely available nonintrusive optoelectronic sensor was used. Found mathematical dependencies reliably convert the sensor output into a powder mass flow rate dependent on powder parameters and feeding conditions. Therefore, the model is usable with various powder types while achieving a Mean Relative Error (MRE) of less than 4% at 125 Hz. Similarly, a model was introduced for the powder velocity using a second sensor further downstream. This provided insight into the powder’s movement while the model achieved an MRE of less than 3%.
As a second main research endeavor, the sensor output was used to implement and investigate a closed-loop powder flow control on a vibration feeder. PID controller gains were calculated empirically at set operating points for the nonlinear system. Again, a usage with various metal powders is possible as the influences of powder parameters and feeding conditions were investigated and incorporated into the model. In addition, the dependence on the previous powder flow (memory effect) was factored in as well. With this, faster recovery from blockages and a reduction in standard deviation during steady state feeding by more than 20% were demonstrated.
Complementary numerical CFD simulations investigated the effect of the carrier gas flow rates on powder flow homogeneity and powder particle size separations. A second modeling approach demonstrated the use of machine learning with the optoelectronic sensor output. A 1D convolutional neural network (CNN) was shown to be able to predict the powder flow with a Weighted Absolute Percentage Error (WAPE) of less than 4% compared to the actual flow. With this, the model’s capability to detect slightly elevated moisture (at <0.4wt%) in the powder as well as differences in particle size distribution was proven on in-situ data from powder feeding.
Finally, the methods were validated on the LMD process by additively manufacturing test components. The active closed-loop powder flow control shows a significant improvement in repeatability for LMD. The in-situ measurement allows a monitoring of the powder mass flow rate with the recorded data throughout the entire AM process. In addition, Scanning Electron Microscopy (SEM) images showed potential benefits at the microscopic level like reduced defects.
With this, the whole chain for a powder flow improvement method was investigated, implemented, and validated in the context of Laser Metal Deposition. Furthermore, a high potential for retrofitting is given while at low cost. This lays the foundation for a more traceable and digital AM process in industry leading to repeatable and safe products
Ratiometric detection of perfluoroalkyl carboxylic acids using dual fluorescent nanoparticles and a miniaturised microfluidic platform
No full textThe widespread contamination of soil and water with perfluoroalkyl substances (PFAS) has caused considerable societal and scientific concern. Legislative measures and an increased need for remediation require effective on-site analytical methods for PFAS management. Here we report on the development of a green-fluorescent guanidine-BODIPY indicator monomer incorporated into a molecularly imprinted polymer (MIP) for the selective detection of perfluorooctanoic acid (PFOA). Complexation of PFOA by the indicator, which is mediated by concerted protonation-induced ion pairing-assisted hydrogen bonding, significantly enhances fluorescence in polar organic solvents. The MIP forms as a thin layer on silica nanoparticles doped with tris(bipyridine)ruthenium(II) chloride, which provides an orange emission signal as internal reference, resulting in low measurement uncertainties. Using a liquid-liquid extraction protocol, this assay enables the direct detection of PFOA in environmental water samples and achieves a detection limit of 0.11 µM. Integration into an opto-microfluidic system enables a compact and user-friendly system for detecting PFOA in less than 15 minutes
Digitalization of Glass Development
No full textIm Vortrag werden erste Ergebnisse aus dem vom BMFTR im Rahmen der MaterialDigital Initiative geförderten Projekt „GlasAgent“ vorgestellt, welches die Glasentwicklung mittels KI vorantreiben soll. In diesem Projekt werden mehrere Entwicklungszyklen inklusive des Recyclingprozesses durchlaufen und die Ergebnisse genutzt, um Datenbanken und Modelle zu verbessern. Mit diesen verknüpft und basierend auf der semantischen GlasDigital-Ontologie soll zukünftig ein Chatbot die Glasentwicklung schneller, präziser und nachhaltiger gestalten
Influence of Substrate Design on Properties and Residual Stresses in Hybrid AM/DED-Arc of High-Strength Steels
No full textHigh-strength, fine-grained structural steels are increasingly used in modern steel construction to meet economic and environmental demands through lightweight design and reduced material usage. Additive manufacturing (AM), in particularly direct energy deposition with gas metal arc welding (DED-Arc), offers significant advantages in flex-ibility, production speed, and cost efficiency. In hybrid AM, conventionally manufac-tured parts are extended or modified using AM processes. Welding-induced residual stresses, especially in the transition area, pose challenges to structural integrity. This study investigates the influence of substrate design and thermal pretreatment on the residual stress state of hybrid AM components made from base material steel S690QL and a welding filler, a modified solid wire G79. Two substrate geometries (I- and T-substrate) are analysed, which are additively and conventionally manufactured, re-spectively. Results show that substrate geometry significantly affects local residual stresses, microstructure and hardness, particularly in the transition are. The findings contribute to a better understanding of the evolution of welding stresses in hybrid AM components to achieve reliable, crack-resistant and economic high-strength steel structures
Unveiling Effects of Biodiesel and Diesel on Environmental Stress Cracking of PE-HD
No full textThe behavior of high‐density polyethylene with respect to resistance against environmental stress cracking (ESC) is usually regarded as an inherent material property being specific for respective types of PE‐HD and tested using standardized methods, conditions, and also standard testing liquids (usually aqueous surfactant solutions). On the other hand, for practical applications the ESC behavior of those polymeric materials, commonly used for pipes or containers, in contact with other liquids (e.g., fuels) is often of relevant interest, but for a reasonable assessment, where consistent benchmark data for a direct comparison are often missing, it is essential to determine the actually prevailing failure mode and classify it related to crack propagation or other mechanisms. Using the well‐established Full Notch Creep Test, which favorably allows for a detailed microscopic fracture surface analysis after failure, the behavior of two typical PE‐HD types for container applications is investigated in biodiesel and diesel and compared to a standard surfactant solution. This enables a clear identification of characteristic features of the interaction of biodiesel and diesel as sorptive fuels in contact with the polymer, revealing the complex interplay of sorption and plasticization as well as ESC inducing effects on PE‐HD, which could be clearly shown for both fuels
Dynamics of Chromosome Evolution in Reticulitermes of Europe
No full textTermites challenge long-standing assumptions about insect social evolution. One important difference compared to the social ants, bees and wasps lies in their chromosomes: termites are diploid, with X/Y sex differentiation observed in most species and males playing active roles across all castes and life stages. Adding to their uniqueness, termites exhibit multivalent chromosome chains during male meiosis—an intriguing and seldom seen feature of eukaryote evolution. These chains, in addition to other chromosomal formations, such as bivalent rings and rods, may serve to suppress recombination, thereby mitigating against the potentially harmful effects of inbreeding. Multivalent chromosome chains may also play a significant role in speciation processes by increasing the likelihood of chromosomal translocations and promoting genomic islands of divergence. In European Reticulitermes, variability in chain length and stability both between and within species provides a compelling model system for studying the evolutionary importance of multivalent chromosome chains at intra- and interspecific levels and at different evolutionary time scales. To investigate these dynamics, we collected over 200 colonies of Reticulitermes species across the Mediterranean, generating de novo reference genomes, comprehensive population genomic as well as karyotypic data from three recently diverged species. Our findings shed light on the intricate relationship between chromosomal architecture and evolutionary mechanisms in termites, offering new insight into how genome structure shapes species evolutio
Manufacturing Ceramics with Light
No full textAdditive manufacturing of extremely complex and filigree geometries from ceramic materials is a fascinating topic as ceramic materials are especially suitable for extremely small structures thanks to their physicochemical properties: they are chemically stable and do not corrode, while exhibiting unique mechanical properties especially in the micrometre range (Fig. 1). In addition, the ceramic structures made of yttria-stabilized zirconia (YSZ) shown in the figure are transparent, which makes them interesting candidates for the development of miniaturized optical components. The refractive index of YSZ measures 2,2 and is therefore considerably higher than that of polymer-based materials or glasses. The possibility of building this type of structure is enabled with the use of ceramic slurries with sufficiently high Transparency for the volumetric process of two-photon polymerization, which uses a femtosecond-short-pulse laser to structure photo-crosslinkable resins in the volume of one droplet. Slurries with even further optimized transparency allow even the application of xolography, a volumetric process that builds components with relatively low resolution, but in relatively large volumes and higher productivity. In the scope of the research presented here, for the first time, this process is applied to sintered ceramic materials. To be able to use minute ceramic structures as real components, an approach for the hybridization of processes ispresented in which components in the centimetre range, with relatively low resolution, are combined with very high-resolution nanostructures