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Probabilistic cost modeling as a basis for optimizing inspection and maintenance of turbine support structures in offshore wind farms
No full textThe operational management of offshore wind farms includes inspection and maintenance (I&M) of the wind turbine support structures. These activities are complex and influenced by numerous uncertain factors that affect their costs. The uncertainty in the I&M costs should be considered in decision value analyses performed to optimize I&M strategies for the turbine support structures. In this paper, we formulate a probabilistic parametric model to describe I&M costs for the common case in which a wind farm is serviced and maintained using a workboat-based strategy. The model is developed based on (a) interviews with a wind farm operator, engineering consultants, and operation and maintenance engineers, as well as (b) scientific literature. Our methodology involves deriving the probabilistic models of the cost model parameters based on intervals representing a subjective expert opinion on the foreseeable ranges of the parameter values. The probabilistic cost model is applied to evaluate the total I&M costs, and a sensitivity analysis is conducted to identify the main cost drivers. The model can be utilized to optimize I&M strategies at the component, structural system, and wind farm level. To illustrate its potential use, we apply it in a numerical study in which we optimize I&M strategies at the structural system level and identify and demonstrate a simplified approach of capturing uncertain I&M costs in the optimization. The simplified approach is generalized and made available for maintenance cost optimization of offshore wind turbine structures
pyIHM: Indirect Hard Modeling, in Python
No full textNMR is a powerful analytical technique that combines an exquisite qualitative power, related to the unicity of the spectra of each molecule in a mixture, with an intrinsic quantitativeness, related to the fact that the integral of each peak only depends on the number of nuclei (i.e., the amount of substance times the number of equivalent nuclei in the signal), regardless of the molecule. Signal integration is the most common approach in quantitative NMR but has several drawbacks (vide infra). An alternative is to use hard modeling of the peaks. In this paper, we present pyIHM, a Python package for the quantification of the components of NMR spectra through indirect hard modeling, and we discuss some numerical details of the implementation that make this approach robust and reliable
In situ Measurement of Hydrogen in Steel using Laser‑induced Breakdown Spectroscopy (LIBS)
No full textThe ISO 3690 standard “Determination of hydrogen content in arc weld metal” requires a thermal activation of the diffusible hydrogen in a piece of weld metal for the subsequent ex situ concentration measurement by carrier gas hot extraction CGHE or thermal desorption spectroscopy (TCD). Laser-induced breakdown spectroscopy (LIBS) offers a time and spatially resolved, almost non-destructive, in situ measurement of hydrogen at surfaces without sample preparation. We measured hydrogen in steels, which were charged either electrochemically or by high-pressure hydrogen gas and compared the results. Further, the feasibility of quantitative hydrogen line scan measurements with LIBS was demonstrated by measuring hydrogen at water jet cut surfaces. The hydrogen concentrations measured with the help of LIBS were compared with CGHE measurements. It was observed that hydrogen can be reliably measured with LIBS for concentrations larger than 2 wt.-ppm. The maximum hydrogen concentration achieved using electrochemical charging was 85.1 ppm. The results show that LIBS is a promising technique for time- and spatially resolved measurements of hydrogen in steels
StahlDigital: Ontology-Based Workflows for the Steel Industry
No full textThe innovative strength of the steel industry is based on the mastery of microstructure–property relationships. Digital workflows can largely contribute to this aim by making the complexity of workflows reproducible and their execution user independent. In this work, the tools and workflows developed in the project StahlDigital as part of the German MaterialDigital initiative are presented and application examples are provided. A steel ontology builds the
foundation for data collection and storage as well as for the semantic description of experimental and simulation data processing workflows. A dataspace powered by the Dataspace Management System (DSMS) digitally represents such workflows and manages data along them in a Findable, Accessible, Interoperable, Reusable manner aiming to derive new knowledge. Experimental data processed via DSMS can be further evaluated and used as input for simulation workflows. The simulations included in such workflows are run by the workflow system pyiron, which has been semantically extended in StahlDigital for this purpose
Modern welding processes for optimising repair welds on high strength offshore steels
No full textThe successful energy transition in Germany will require offshore wind turbines with outputs >10 MW in the future. To achieve these high outputs, turbines far from coast are required with large subsea jacket structures (30 m up to 50 m) and tall towers (up to 200 m). High-strength steels with a yield strength up to 500 MPa and wall thicknesses up to 150 mm are increasingly being used for these structures. This plac-es high demands on welding manufacturing, especially for high-strength offshore steels. During the manu-facturing process detected defects by NDT require localized repair of welds by gouging and rewelding. Due to a lack of investigations, there are no repair concepts and information in standards and guidelines, par-ticularly for high-strength thick plate joints made of high-strength offshore steels. However, these are ur-gently needed to enable manufacturers, especially SMEs, to carry out safe and economical repairs. There-fore, BAM started the FOSTA project P1629 (IGF 01IF22746N) to investigate the stress-optimized repair (local gouging and welding) of high-strength thick plate joints made of offshore grades in the yield strength range off 355 to 460 MPa and similar weld metal with controlled high-performance GMAW pro-cesses and optimized narrow gouging grooves. The experimental analyses take into account the complex interaction of process, material, and design-related influences on the formation of weld induced stresses and the special microstructure of high-strength fine-grain structural steels. Welding-related material degra-dation and crack-critical residual tensile stresses need to be avoided to ensure high component safety and performance. A reduction in residual stress in the presence of high restraint conditions can be achieved by adapted heat control (if no disassembly measures are possible). The repair process involves manual thermal gouging, which allows the groove configuration to be modi-fied. Modern welding processes using high frequency arc control provide deep root penetration and focused energy input capable of welding narrow seams. A comparison was made between the traditional weld con-figuration with a wide 45° groove and transition arc welding and a narrow 30° groove with modern welding process. Even in the case of free shrinkage specimens, the narrow groove weld exhibits a significant reduc-tion of residual stresses, cf. Figure 1, especially in the HAZ and toward the adjacent base material. This can be attributed to the lower weld metal volume needed and the reduction of heat input per layer due to the controlled arc process. For the purposes of this comparison, the same weld seam build-up (but different number of layers) has been applied to both seam configurations. Note that in industrial application (manu-al welding), the wider groove would be welded with several off-center weld beads with conventional weld-ing process. In this analysis this would cause asymmetric effects regarding the residual stress state, diffi-cult to compare to each other. Component-related welding experiments on special testing equipment, adapted process and heat control concepts along with variable groove configurations will be developed and recommendations for guidelines elaborated. This is the prerequisite for fully utilizing the strength potential of high-strength steels and making a valuable contribution to the energy transition in Germany, especially for steel-processing SMEs
Vereinfachte Prüfmethode zur Bewertung der Gefahr wasserstoffunterstützter Kaltrisse (HACC) beim Lichtbogenschweißen hochfester Stähle
No full textDie Präsentation gibt einen Kurzüberblick über die Versuchsmethodik und den erreichten Projektfortschritt des IGF-Projektes 01IF22624N bzw. DVS-Nr. 01.3410. Ziel der Untersuchungen ist eine Methodik für eine vereinfachte Probenform zur Bewertung der Kaltrissanfälligkeit durch Wasserstoff bei hochfesten, geschweißten Stählen. Dazu wird ISO 3690 (Quantifizierung des H-Gehaltes) mit direkt prüfbaren Querzugproben kombiniert, die die realistische Bewertung der Schweißnaht unter industriepraktischen Parametern ermöglicht
Real-time monitoring of hydrogen composite pressure vessels using surface-applied distributed fiber optic sensors
No full textIn this paper, we report to the best of our knowledge for the first time on continuous real-time monitoring of composite overwrapped pressure vessels (COPVs) designed for hydrogen storage using surface-applied distributed fiber optic sensors (DFOS). We conducted continuous and real-time DFOS measurements during pressure cycling tests consisting of periodic pressure fluctuations between 20 bar and 875 bar, with a rate of 5 cycles min−1. During pressure cycling, the DFOS system measured strain changes, that under normal operating conditions were linearly correlated to changes in pressure. To detect and quantify damage-related anomalies, we trained a simple regression model to predict strain from pressure data and used the difference between predicted and measured values as a damage indicator. With our approach, the DFOS system not only detected and localized the damage but also continuously tracked its evolution in real time under dynamic pressure conditions. Furthermore, unlike previous studies where optical fibers were embedded within the composite structure, we applied them on the COPV surface, reducing both implementation cost and time while eliminating the need to modify the COPV manufacturing process. Based on our results, we are confident that DFOS can enhance safety and facilitate the transition from time-consuming periodic inspections to more efficient, machine learning-based predictive maintenance
Competitive cytometry-based immunoassay for patulin determination in apple juice
No full textPatulin is a mycotoxin that is frequently found in apples and apple-derived products. Given the potential harm it can cause to humans, maximum levels for patulin in food have been set worldwide. Conventional methods for the detection of patulin are often time-consuming or lack sensitivity. In this study, a novel cytometry approach based on specific monoclonal antibodies is presented. These high-affinity binders do not target patulin itself, but a stable derivative (adduct) that is rapidly obtained in an aqueous medium at room temperature. To develop the assay, a specific fluorescent competitor was designed and synthesized. After optimizing the assay conditions, including the concentration of the fluorescent competitor and of the antibody bound to polystyrene-silica core–shell microparticles, a detection limit of 0.03 μg L-1 in buffer was achieved. Finally, validation according to Commission Regulation (EU) 2023/2782 demonstrated that apple juice samples spiked with patulin at 25 or 50 μg L-1 (permissible limits set by the EU) were properly scored as non-compliant without any additional treatment other than a simple dilution step in buffer. The developed assay offers several key advantages, including rapid analysis, high sensitivity and specificity, and the potential for multiplexing, making it a promising analytical tool for routine monitoring of patulin contamination in food
Embedded sensor for the detection of TNT in surface and marine waters
No full textIn 1945, the Potsdam Conference led to the decision to destroy a significant amount of ammunition from the warring parties of WWII. Dumping was considered the cheapest, quickest, and safest solution to dispose of unused ammunition. However, thin barrels or containers often leak after 50 years, allowing explosives to escape into the marine environment. As the effects of weapons chemicals on ecosystems are well-documented, it is becoming increasingly important to detect, recover and dispose of old ammunition. Physical techniques such as magnetometry and sonar are used to detect ammunition in the sea, but they do not provide chemical information. Detecting leaking organic contaminants like TNT or other explosives in water or soil requires high-end laboratory equipment like HPLC or GC-MS, making remote water testing virtually impossible. As an alternative, a miniaturized method for the selective and sensitive indication of TNT using fluorescence light-up sensing was developed.
The visual identification of TNT with a nucleophile that forms a strongly absorbing charge transfer complex (CTC) is a well-known method. This CTC is formed by the attraction of an electron from the donor molecule by the electron-deficient aromatic ring. In this work, a TNT-based CTC was selectively formed by the addition of tetraoctylammonium acetate in N,N-diethylformamide and, as expected, showed strong absorption. Surprisingly, at room temperature, the CTC can be converted into a fluorescent product with an emission band centred at 577 nm. For the detection of TNT in water, a microfluidic chip made of polydimethylsiloxane (PDMS) is used for both the extraction and reaction steps. In addition to miniaturising the experimental steps, the optical system (fluorometer) has been integrated into an autonomous smartphone assembly capable of catalysing the photoreaction and analysing the fluorescence response. Taking advantage of the light-up response, TNT was still easily detectable down to 9.4 ng with the CMOS camera. Further evaluation of this analytical tool consisted of analyses of unfiltered and untreated surface water samples spiked directly with increasing concentrations of TNT to reflect different levels of contamination. LODs of 21 and 40 ng were found for samples from the Teltow Canal in Berlin (DEU) and the Baltic Sea near Greifswald (DEU).
Such an analytical tool could be used to monitor water quality in the field, as the release of organic pollutants from munitions into surface and marine waters will become increasingly problematic and concentrations will continue to rise over the coming decades
Forever Chemicals of Tomorrow? Fate of Fluorinated Li-Ion Battery Additives
No full textFluorinated organic compounds (FOCs) are a category of anthropogenic chemicals distinguished by their resilient carbon-fluorine bonds, which confer significant chemical stability and resistance to degradation. This durability makes them valuable in various applications, particularly in lithium-ion batteries (LiBs) [1,2]. However, the environmental implications of these compounds have not been thoroughly investigated. This study focuses on the environmental impact of two fluorinated aromatic compounds: tris(pentafluorophenyl)borane (TPFPB) and tris(pentafluorophenyl)phosphine (TPFPP), specifically regarding their roles in enhancing LiB performance [3,4]. To assess their environmental fate, we employed a range of laboratory simulation techniques generating transformation products (TPs), including total oxidizable precursor assays, electrochemistry (EC), Fenton reactions, UV-C irradiation, and hydrolysis. We utilized liquid chromatography and gas chromatography coupled with high-resolution mass spectrometry to identify TPs and predict their molecular formulas. Despite their structural similarities, TPFPB and TPFPP displayed differences in electrochemical behavior and degradation pathways. TPFPB underwent significant transformation through hydroxylation and hydrolysis, yielding a diverse array of 49 TPs, including 28 newly identified compounds, including oligomers and minor levels of highly toxic dioxins. In contrast, TPFPP underwent degradation only at extreme conditions, highlighting the necessity for new conditioning protocols in electrochemistry. Overall, our simulation experiments revealed 9 structurally unique compounds, including 7 previously unidentified partially defluorinated byproducts. This study underscores the potential environmental hazards associated with the use of FOCs in lithium-ion batteries and enhances our understanding of the complex interactions these compounds have with the environment