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Tensile Properties and Fracture Analysis of Duplex (2205) and Super Duplex (2507) Stainless Steels, Produced via Laser Powder Bed Fusion Additive Manufacturing
Get PDFAbstract Additive manufacturing of duplex (DSS) and super duplex stainless steel (SDSS) has been successfully demonstrated using laser powder bed fusion (LPBF) in recent years. Owing to the high cooling rates, as-built LPBF-processed DSS and SDSS exhibit close to 100% ferritic microstructures and require heat treatment at 1000–1300 °C to obtain the desired duplex microstructure. In this work, the mechanical properties of DSS and SDSS processed via LPBF were investigated in three building directions (vertical, horizontal, diagonal) and three processing conditions (as-built, stress-relieved, annealed, and quenched) using uniaxial tensile testing. As-built samples exhibited tensile and yield strength greater than 1000 MPa accompanied by less than 20% elongation at break. In comparison, the water-quenched samples and samples annealed at 1100 °C exhibited elongation at break greater than 34% with yield and tensile strength values less than 950 MPa. Stress relief annealing at 300 °C had a negligible impact on the mechanical properties. Austenite formation upon high-temperature annealing restored the reduced ductility of the as-built samples. The as-built and stress-relieved SDSS showed the highest yield and tensile strength values in the horizontal build direction, reaching up to ≈1400 and ≈1500 MPa (for SDSS), respectively, as compared to the vertical and diagonal directions. Fractographic investigation after tensile testing revealed predominantly a quasi-ductile failure mechanism, showing fine size dimple formation and cleavage facets in the as-built state and a fully ductile fracture in the annealed and quenched conditions. The findings in this study demonstrate the mechanical anisotropy of DSS and SDSS along three different build orientations, 0°, 45°, 90°, and three post-processing conditions.publishedVersio
Power Fluctuations caused by Wind Turbulence on a 15MW Floating Offshore Wind Turbine
Get PDFThis study informs about power fluctuations caused by wind turbulence that should be expected from a 15MW floating offshore wind turbine in the context of power supply to an isolated grid with energy storage. To this end, appropriate engineering models are used to screen through normal wind conditions to be encountered during the system's lifetime. The impact of the various modelling assumptions is then assessed through sensitivity studies. Power fluctuations are then translated into size requirements for energy storage, when its objective is to filter fluctuations over a selected time horizon to provide stable power to the isolated grid.Power Fluctuations caused by Wind Turbulence on a 15MW Floating Offshore Wind TurbinepublishedVersio
Gjengangere i bygg og anlegg - Kartlegging og anbefalinger for å løfte det felles sikkerhetsarbeidet
Get PDFRapporten oppsummerer funnene fra et prosjekt som er gjennomført av SINTEF på oppdrag av Fondsstyret for regionale verneombud i bygge- og anleggsbransjen i perioden august 2023 – juni 2024. Bakgrunnen var at fondsstyret ønsket å få utarbeidet en kartlegging og kunnskapsoppsummering spisset inn mot gjengangertematikken i bransjen, med forslag til videre arbeid. Gjennom prosjektet er det utarbeidet en definisjon av "gjengangere", gitt en beskrivelse av utvikling og status på skader og ulykker, undersøkt hva som gjøres av sentrale aktører i dag, og gitt anbefalinger om hva som skal til for å løfte det felles sikkerhetsarbeidet i framtiden.Gjengangere i bygg og anlegg - Kartlegging og anbefalinger for å løfte det felles sikkerhetsarbeidetISBN: 978-82-14-07034-7publishedVersio
Social acceptance for salmon produced in new production systems - Report on willingness to pay for new production systems and social acceptance of salmon farming in general
Get PDFThis report summarizes the findings from a price experiment survey on the willingness to pay (WTP) for salmon produced using new production systems in salmon farming in three countries (Norway, Canada and Scotland). This includes land-based, floating closed containment cages and offshore production systems. The results revealed that consumers preferred salmon produced using conventional (traditional) systems rather than new production systems. Regarding social acceptance, respondents stated they agreed that the environmental issues were problematic, while the economic contributions were considered as positive.Social acceptance for salmon produced in new production systems - Report on willingness to pay for new production systems and social acceptance of salmon farming in generalpublishedVersio
Optimizing Feeding Strategies in Aquaculture Using Machine Learning: Ensuring Sustainable and Economically Viable Fish Farming Practices
Get PDFThe aquaculture industry faces critical challenges in optimizing feeding strategies to enhance fish growth while minimizing environmental impacts and ensuring economic viability. Traditional feeding methods often fall short in adapting to dynamic environmental conditions and fish growth rates, leading to suboptimal growth, waste, and environmental degradation. To address these issues, this study introduces a robust machine learning-based framework designed to optimize feeding processes in aquaculture. The framework employs advanced regression models such as Gradient Boosting Regressor, Elastic Net Regression, and Support Vector Regression to predict optimal feeding rates with high accuracy and efficiency. Our methodology integrates real-time data from environmental sensors, video analytics, and manual logging to predict the optimal feed amount. The goal of this comprehensive approach is to achieve high growth performance indicators such as Specific Growth Rate (SGR), Relative Growth Index (RGI), and optimal Feed Conversion Ratio (FCR), while also ensuring minimal feed spillage. By employing machine learning, we can dynamically adjust feeding amounts based on fish appetite and environmental conditions, thus ensuring sustainable and economically viable fish farming practices. This paper details the implementation of this framework, encompassing data collection and cataloging, model training, selection, and validation processes, and discusses the significant improvements over traditional methods. Our results demonstrate the model’s effectiveness in reducing waste and enhancing fish growth, illustrating the potential for wider application within the aquaculture industry.Optimizing Feeding Strategies in Aquaculture Using Machine Learning: Ensuring Sustainable and Economically Viable Fish Farming PracticespublishedVersio
A complete experimental study on hard granites: Microstructural characterization, mechanical response, and failure criterion
Get PDFThis study, performed during the ORCHYD European project, devoted to drilling deep geothermal boreholes, has many potential applications to mechanical studies. It gathers geological descriptions of three outcropping granites from Scandinavia (Kuru Grey and Red Bohus) and from the South of France (Sidobre). Microstructural investigations include optical microscopy and X-ray tomography. The three granites chosen contain grain sizes that cover all the common ranges for granites: fine, medium and coarse. As the mineral phase volume fractions are similar in each, the grain defects and grain boundaries are carefully studied in an attempt to understand the physical and mechanical properties of the three granite rock samples measured at laboratory specimen scale. The rocks are tested for UCS, BTS and triaxial compressive strength with confining pressures up to 225 MPa or/and high strain-rates up to 103/s. The micro-structural parameters influencing the mechanical behaviour are highlighted. Test results show that the effect of confining pressure and strain-rate on compressive strength are uncoupled. These effects are then estimated independently, and a fracture criterion in compression accounting for both variables is proposed for the family of very hard granites. This criterion takes as a single reference strength measure for each rock the deviatoric stress at failure under 20 MPa confining stress in the quasi-static regime. It is then compared with existing datasets for which both quasi-static and dynamic regime data are available. This complete data set on these three very hard granites (UCS ∼ 200 MPa), together with a synthesis for failure prediction, has the potential to inform numerous rock engineering projects and be of value to the scientific community.publishedVersio
Superstructure of Locally Disordered Na2Zn2TeO6
Get PDFThis work expands on the superstructure in the layered oxide Na2Zn2TeO6 (NZTO). The diffractogram contains weak peaks that are not fitted by the average structure but are found to belong to a 2 × 2 × 3 commensurate modulation of the structure. The modulated structure was found by randomizing the starting points to ensure that the global minima are identified. The resulting superstructure is then used to generate a starting structure for reversed Monte Carlo (RMC) fitting of the total scattering data. We identify two structural features that are preserved through both fittings. One is that two of the Zn/Te columns in the layer direction have a significantly higher degree of disorder, with the exchange of Zn and Te. The second feature is that one of the crystallographic Na sites (2a) was found to be empty. The Na atoms are located midway between crystallographic 2a and 6g sites, which surrounds half of the 2a sites. This type of off-centering is found both in the modulated structure and in the corresponding structure preserved through RMC modeling. The results are discussed in relation to variable-temperature solid-state NMR data measured between 100 and 293 K. We suggest that the phenomenon is a feature of a dynamic situation and an important clue to progress the understanding of ion dynamics in more detail.publishedVersio
A practical approach to calculating inertial forces for nontrivial subsea structures using CFD simulation
Get PDFIn the oil and gas industry, the majority of subsea structures are subjected to considerable forces from sea waves and currents. It is therefore of critical importance to be able to accurately assess these forces, both during the commissioning process, when the structure is lowered with a crane, and for stability calculations, such as those required for ballast estimation. Of particular importance in this context is the second scenario, which is particularly relevant for protection structures made with glass-reinforced plastic (GRP) in the form of large covers. Due to their relatively low weight and high surface area, these structures require ballast to ensure a fixed position. The following paper presents a set of observations and guidelines for calculating wave and current loads for non-trivial objects, such as GRP covers. The work was focused on the inertial forces, as these forces are most problematic due to their transient nature. Two approaches are presented, along with their applicability and limitations: a simplified and a detailed. Both methods are based on curve-fitting the outcome of the simulation to the Morison equation. Furthermore, a simple validation study is presented for the two methods, comparing simulation data to values obtained from the literature. The test demonstrated decent accuracy, particularly for the detailed method. A comparison between the simplified and detailed methods indicates that while the simplified method produces comparable results for thin-walled objects, such as GRP covers, it is not as effective for thick-walled structures.Finally, the influence of the seabed was investigated. The study demonstrated that the inertia forces acting on a structure increase considerably when the object is in close proximity or in contact with the seabed. As the majority of existing literature provides data for relatively simple objects set away from the boundaries, the presented methods appear to be a promising tool for the analysis of structures situated on a seabed.publishedVersio
Flexibility through power-to-heat in local integrated energy systems with renewable electricity generation and seasonal thermal energy storage
Get PDFIn heating dominated regions, the flexibility obtained through coupling heating and power sectors is particularly beneficial for the integration of high shares of variable renewable energy sources. This study concerns the design of an energy system for a new neighborhood in Norway, including a seasonal thermal energy storage storing excess heat from waste incineration, a seawater heat pump, and local power generation. Two supply temperature scenarios are considered for the local heating network: medium-temperature (70 °C), where all heating demands are covered through the network; and low-temperature (45 °C), where booster heat pumps are applied for hot water production. Both scenarios are more cost-effective than if heat demands were to be met through import from the district heating network, however, the difference between the two scenarios is small. The low-temperature scenario has the highest degree of self-sufficiency, and the advantage of additional flexibility gained through the local heat pumps with hot water storage. Cost-optimal charging strategy for the seasonal storage was highly dependent on the pricing of excess heat with respect to the electricity prices. Unlimited sharing of electricity among all users in the neighborhood should be promoted to gain full benefits of local flexibility.Flexibility through power-to-heat in local integrated energy systems with renewable electricity generation and seasonal thermal energy storagepublishedVersio
Evaluation of Wind Farm Control Strategies - Coupling with Drivetrain Degradation
Get PDFA mid-fidelity simulation framework for large offshore wind farms has been developed at SINTEF, for the efficient joint modelling of active power control and structural degradation due to fatigue damage. It bridges two fields of research that are traditionally split: grid integration and mitigation of asset degradation, through multi-objective wind farm control. Component-level damage is brought to farm-level simulations. There, damage and power demand from the grid are linked to stochastic loads and power fluctuations arising from turbulence in the wind, on which a particular emphasis has been set. In a joint project with NTNU, this has been applied to the mitigation of the degradation of power train components (gears and bearings) in curtailed (down-regulated) wind conditions. It is shown that when a farm is requested not to operate at its full available power by the grid operator, it is possible to —to some extent— steer degradation to better fit maintenance scheduling or lifetime extension plans to further reduce LCOE. The framework has been developed in parallel projects in synergy with NorthWind and consists of four main features: (1) a wind farm simulator adapted for stochastic simulations of large wind farms in down-regulated operation, (2) a farm-wide turbulence generator, (3) a wind farm controller and (4) a database for drivetrain degradation based on turbine- and component-level simulations. This report first introduces the concept and motivation, then presents each of the above-mentioned features before linking them in a case study.Evaluation of Wind Farm Control Strategies - Coupling with Drivetrain DegradationpublishedVersio