Artículos (Ingeniería Mecánica y Fabricación)

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Hybrid kinetic-MHD modeling of alpha-driven TAEs in the SPARC tokamak
(IOP PUBLISHING, 2025-03) Tinguely, R. Alexander; Gonzalez Martin, Javier; Todo, Yasushi; Universidad de Sevilla. Departamento de Ingeniería Mecánica y Fabricación; Agencia Estatal de Investigación. España
As the magnetic confinement fusion community prepares for the next generation of fusion devices and burning plasmas, there is still a question of whether fast ions (FIs) will drive MHD instabilities, causing significant redistribution or even loss of FIs, thereby leading to reduced plasma performance and possibly threatening the integrity of the first wall. In this paper, we explore the existence and stability of toroidicity-induced Alfvén eigenmodes (TAEs) in the > 100 MW , Q ∼ 9 -11 DT-fusion power ‘Primary Reference Discharge’ (PRD) of the SPARC tokamak; the PRD has a relatively low on-axis alpha pressure, β α 0 ≈ 0.6 % , due to the high magnetic field strength, B 0 = 12.2 T . A scan in toroidal mode number is performed in the vicinity of the estimated ‘most unstable’ modes, n ≈ 5-20, with the linear eigenvalue code NOVA-K and nonlinear initial-value code MEGA. Both codes identify the same (even) n = 10 TAE located near q = 1 with frequency f ≈ 360 kHz and alpha drive γ / ω ≈ + 0.6 % . While MEGA evaluates this mode to be marginally unstable for the nominal alpha pressure, NOVA-K instead identifies a higher frequency (odd) n = 10 TAE as marginally destabilized; different evaluations of radiative damping are likely the cause of this discrepancy. These results indicate that AEs may be only marginally unstable for the highest performing SPARC PRD, at least for the q profile explored here. They also serve as a starting point for further scans, inclusion of FIs from auxiliary heating systems, and exploration of AE-induced FI transport, as well as a guide for diagnostic measurements of these n ≈ 10 AEs.
The influence of thermo-electromechanical coupling on the performance of lead-free BNT-PDMS piezoelectric composites
(IOP Publishing, 2024) Akshayveer; Buroni Cuneo, Federico Carlos; Melnik, Roderick; Rodríguez de Tembleque Solano, Luis; Sáez Pérez, Andrés; Singh, Sundeep; Universidad de Sevilla. Departamento de Ingeniería Mecánica y Fabricación; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Universidad de Sevilla. TEP245: Ingeniería de las Estructuras
In recent times, there have been notable advancements in haptic technology, particularly in screens found on mobile phones, laptops, light-emitting diode (LED) screens, and control panels. However, it is essential to note that the progress in high-temperature haptic applications is still in the developmental phase. Due to their complex phase and domain structures, lead-free piezoelectric materials such as Bi0.5Na0.5TiO3 (BNT)-based haptic technology behave differently at high temperatures than in ambient conditions. Therefore, it is essential to investigate the aspects of thermal management and thermal stability, as temperature plays a vital role in the phase and domain transition of BNT material. A two-dimensional thermo-electromechanical model has been proposed in this study to analyze the thermal stability of the BNT-PDMS composite by analyzing the impact of temperature on effective electromechanical properties and mechanical and electric field parameters. However, the thermo-electromechanical modelling of the BNT-PDMS composite examines the macroscopic effects of the applied thermal field on mechanical and electric field parameters, as phase change and microdomain dynamics are not considered in this model. This study analyzes the impact of thermo-electromechanical coupling on the performance of the BNT-PDMS composite compared to conventional electromechanical coupling. The results predicted a significant improvement in piezoelectric response compared to electromechanical coupling due to the increased thermoelectric effect in the absence of phase change and microdomain switching for temperature boundary conditions below depolarization temperature (Td ∼ 200◦C for pure BNT material).
Recent progress of JT-60SA project toward plasma operation
(2024-09-12) Shirai, H.; Takahashi, K.; Di Pietro, E.; Abate, D.; Abdel Maksoud, W.; Abe, H.; Ayllón Guerola, Juan Manuel; Garcia Dominguez, Javier; García López, Francisco Javier; García Muñoz, Manuel; Gonzalez Martin, Javier; Higashijima, S.; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Universidad de Sevilla. Departamento de Ingeniería Mecánica y Fabricación
Superconducting (SC) tokamak JT-60SA plays an essential role in fusion research and development by supporting and complementing the ITER project, providing directions to the DEMO design activity and fostering next generation scientists and engineers. Since the short circuit incident at the terminal joints of equilibrium field coil #1 during the integrated commissioning (IC) in March 2021, both EU and JA implementing agencies (IAs) have examined how to ensure safe operation of JT-60SA by mitigating the risk of possible discharge occurrence inside the cryostat. Based on the experience of the global Paschen tests, the IAs have established a strategy of risk mitigation measures, which is a combination of (i) reinforcement of insulation, (ii) avoiding unnecessary voltage application to the coil systems and (iii) immediate de-energization of the coils when deteriorated vacuum conditions are detected. Thanks to the considerable efforts of the Integrated Project Team members, the IC restarted in May 2023. After confirmation of the SC state of the coil systems (TF, EF and CS), the coil energization test and the plasma operation phase 1 (OP-1) started. The first plasma was successfully achieved on 23 October 2023 with a limited value of voltage and current applied to the coils. The plasma configuration control was also confirmed with low plasma current and low auxiliary heating power conditions. Based on the IO–F4E–QST collaboration, activities of JT-60SA have been shared with the IO and provided an important lesson for ITER assembly and commissioning, and will provide an outstanding contribution to fusion research at large. After OP-1, maintenance & enhancement phase 1 (M/E-1) starts from January 2024, in which in-vessel components are installed, and heating and diagnostic systems are extensively upgraded to allow a high power heating experiment planned in OP-2. In order to make the best use of JT-60SA, a newly organized JT-60SA experiment team will refine the research plan for the future high heating power operation phase.
Novel test designs for assessing the shear fracture forming limit in thin-walled tubes
(Elsevier, 2025-05) Suntaxi, C.; López Fernández, José Andrés; Centeno Báez, Gabriel; Vallellano Martín, Carpóforo; Universidad de Sevilla. Departamento de Ingeniería Mecánica y de Fabricación; Ministerio de Ciencia, Innovación y Universidades (MICIU). España; Agencia Estatal de Investigación. España; Next Generation EU; Ministerio de Ciencia e Innovación (MICIN). España; Universidad de Sevilla. TEP111: Ingeniería Mecánica
Thin-walled tubes are used for the manufacturing of essential components in several industries. Indeed, the characterization of their formability and failure is vital for tool design, product quality and safety. In the recent years, the number of procedures and test designs for characterizing tubes in forming has experienced a significant development. This progress has been achieved in combination with the use of digital image correlation techniques and finite element analysis, making use of different plastic anisotropy criteria. Nevertheless, most of those tests are aimed at the assessment of failure in mode I of fracture mechanics, being the analysis of fracture under in-plane shear, i.e. mode II of fracture mechanics, reduced to a very limited number of research works based in the adaptation of the corresponding sheet metal forming tests inducing shear. To this regard, this work presents two new procedures based on the specific thin-walled tube geometry for characterizing formability in-plane shear and failure in mode II of fracture mechanics, addressing the absence of specific experimental methods for evaluating the shear fracture forming limit (SFFL) for tubes. The results, based on a combined numerical modelling and experimental analysis of the proposed tests, show that the SFFL can be accurately evaluated by controlling a set of geometrical parameters in the specimens designed to generate shear in tubes by applying either tensile or compressive forces. These proposed tests provide a valuable tool for characterizing the SFFL of thin-walled tubes.
Self-adaptive diagnostic of radial fast-ion loss measurements on the ASDEX Upgrade tokamak (invited)
(American Institute of Physics, 2021-05-14) Gonzalez Martin, Javier; García Muñoz, Manuel; Sieglin, B.; Herrmann, A.; Lunt, T.; Ayllón Guerola, Juan Manuel; Galdón Quiroga, Joaquín; Hidalgo-Salaverri, J.; Kovacsik, A.; Rivero Rodríguez, Juan Francisco; Sanchis Sánchez, Lucía; Silvagni, D.; Zoletnik, S.; Domínguez Abascal, Jaime; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Universidad de Sevilla. Departamento de Ingeniería Mecánica y de Fabricación; EUROfusion Consortium; Ministerio de Ciencia e Innovación (MICIN). España
A poloidal array of scintillator-based Fast-Ion Loss Detectors (FILDs) has been installed in the ASDEX Upgrade (AUG) tokamak. While all AUG FILD systems are mounted on reciprocating arms driven externally by servomotors, the reciprocating system of the FILD probe located just below the midplane is based on a magnetic coil that is energized in real-time by the AUG discharge control system. This novel reciprocating system allows, for the first time, real-time control of the FILD position including infrared measurements of its probe head temperature to avoid overheating. This considerably expands the diagnostic operational window, enabling unprecedented radial measurements of fast-ion losses. Fast collimator-slit sweeping (up to 0.2 mm/ms) is used to obtain radially resolved velocity-space measurements along 8 cm within the scrape-off layer. This provides a direct evaluation of the neutral beam deposition profiles via first-orbit losses. Moreover, the light-ion beam probe (LIBP) technique is used to infer radial profiles of fast-ion orbit deflection. This radial-LIBP technique is applied to trapped orbits (exploring both the plasma core and the FILD stroke near the wall), enabling radial localization of internal plasma fluctuations (neoclassical tearing modes). This is quantitatively compared against electron cyclotron emission measurements, showing excellent agreement. For the first time, radial profiles of fast-ion losses in MHD quiescent plasmas as well as in the presence of magnetic islands and edge localized modes are presented.
On the determination of forming limits in thin-walled tubes
(Elsevier, 2019-05) Magrinho, J. P.; Silva, M.B.; Centeno Báez, Gabriel; Moedas, F.; Vallellano Martín, Carpóforo; Martins, P.A.F.; Universidad de Sevilla. Departamento de Ingeniería Mecánica y de Fabricación; Fundação para a Ciência e a Tecnologia. Portugal; Universidad de Sevilla. TEP111: Ingeniería Mecánica
This paper proposes a methodology to determine the formability limits of thin-walled tubes and to plot them in principal strain space and in the space of effective strain vs. stress-triaxiality. Digital image correlation (DIC), combined either with time-dependent methodologies or strain-force approaches, is utilized to identify the onset of failure by necking and obtain the corresponding limit strains. Thickness measurements and determination of the gauge length strains across the cracked regions are utilized to characterize the onset of fracture and to evaluate the fracture limit strains. Results show that the utilization of tube expansion with rigid punches and elastomers allow obtaining strain loading paths and fracture loci by necking and fracture across a wide range of tube forming conditions ranging from biaxial stretching in the first quadrant to pure tension in the second quadrant of principal strain space. The fracture forming line (FFL) is the first time ever determined for thin-walled tubes. The forming limit curve (FLC) and the FFL resemble those of sheet and strip materials and their use is of paramount importance in the design and optimization of tube forming processes.
A detailed study of short fatigue crack directions for carbon steel specimens with circular holes subject to cyclic biaxial loads
(Elsevier, 2023-12) Balbín Molina, José Antonio; Chaves Repiso, Víctor Manuel; Navarro Robles, Alfredo; Universidad de Sevilla. Departamento de Ingeniería Mecánica y de Fabricación; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); Agencia Estatal de Investigación. España; Ministerio de Ciencia e Innovación (MICIN). España; Universidad de Sevilla. TEP022: Diseño Industrial e Ingeniería del Proyecto y la Innovación; Universidad de Sevilla. TEP111: Ingeniería Mecánica
The effect of notches and biaxial fatigue loading on the crack paths was studied in detail for thin-walled tube specimens with a passing-through hole, paying special attention to the short-crack period. The study was focused on the high cycle fatigue regime. The material was a carbon steel and the tests were under load control, at t 𝑅𝜎 = −1 . The crack initiation point on the notch surface and the crack direction were studied with an optical microscope on the specimen outer surface and with a scanning electron microscope and a non-contact 3D optical profilometer on the fracture surface. The crack direction was analyzed for several crack lengths, ranging from the length of one average grain to the length of twenty average grains, all lengths within the short-crack regime, in order to carefully observe the evolution of the crack direction in the Stage I and during the transition from Stage I to Stage II. A statistical analysis of the crack initiation point and the experimental crack directions was carried out. In general, the crack initiation point was close to the maximum principal stress point. The crack direction during the first grains was approximately the Mode I direction. There was no initiation in Mode II. The crack continued in the Mode I direction as it got longer, within the short-crack period. The experimental fatigue limits were compared with the predictions calculated with two models from the literature. The direction of the straight lines used by the models to make the predictions were compared with the average crack directions measured experimentally. The goodness of the models, not only from the point of view of the fatigue limit value prediction but also from the closeness of the direction of the line used for the prediction to the experimental crack direction, was discussed.
On the lowest-frequency bandgap of 1D phononic crystals
(Elsevier, 2025-01) González-Carbajal, Javier; Lemm, M.; García Suárez, Joaquín; Universidad de Sevilla. Departamento de Ingeniería Mecánica y de Fabricación; Universidad de Sevilla. TEP111: Ingeniería Mecánica
This manuscript puts forward and verifies an analytical approach for the design of phononic crystals that feature a bandgap at the lowest possible frequencies, in the sense of finding the optimal layer thicknesses for a given set of materials in a prescribed layering order. The mathematical formulation rests upon the exact form of the half-trace function (half of the trace of the global transfer matrix) of the layered medium, which is directly connected to its bandgap structure. After showing that there is a tight relation between the frequency at which the first bandgap opens up and the curvature of the half-trace function at zero frequency, a new optimization strategy is proposed, based on the minimization of this curvature. Notably, the optimal solution is expressed as a closed-form equation and remains valid for any number of layers within the unit cell. We validate this analytical result by comparison with a numerically optimized design, finding remarkably good agreement between both solutions.
Directions of high cycle fatigue cracks emanating from circular notches studied by optical profilometry
(Elsevier, 2022-12) Balbín Molina, José Antonio; Chaves Repiso, Víctor Manuel; Larrosa, N.O.; Madrigal Sánchez, Carmen; Navarro Robles, Alfredo; Universidad de Sevilla. Departamento de Ingeniería del Diseño; Universidad de Sevilla. Departamento de Ingeniería Mecánica y de Fabricación; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); Ministerio de Ciencia e Innovación (MICIN). España; Agencia Estatal de Investigación. España; Universidad de Sevilla. TEP022: Diseño Industrial e Ingeniería del Proyecto y la Innovación; Universidad de Sevilla. TEP111: Ingeniería Mecánica
Current models for predicting the fatigue endurance of notched solids use the stresses along a straight line, beginning at the notch root, as a simplification of the real crack propagation path. In this work, the experimental crack paths for hollow notched samples were analysed through different microscopy techniques, with the objective of establishing high cycle fatigue crack growth directions in a mild steel. Fully reversed tension–compression fatigue tests (𝑅 = −1) of thin-walled tube specimens with a passing-through hole were carried out. The crack paths observed in the outer cylindrical surface were studied in each case, with special attention to the crack initiation point and the crack direction along the first grains. Moreover, the analysis of the fracture surfaces allowed the same analysis to be performed to determine the internal crack paths. It was observed that the crack initiation point was close to the maximum principal stress point at the hole contour as obtained from linear elastic finite element analysis, and the crack direction in its initiation was generally close to Mode I direction, contrary to the conventionally accepted 45◦ crack growth direction.
On the influence of structural and chemical properties on the elastic modulus of woven bone under healing
(Frontiers, 2024-10) Blázquez Carmona, Pablo; Mora Macías, Juan; Pajares, Antonia; Mármol, Álvaro; Reina Romo, Esther; Universidad de Sevilla. Departamento de Ingeniería Mecánica y de Fabricación; Agencia Estatal de Investigación. España; Universidad de Sevilla. TEP111: Ingeniería Mecánica
Woven bone, a heterogeneous and temporary tissue in bone regeneration, is remodeled by osteoblastic and osteoclastic activity and shaped by mechanical stress to restore healthy tissue properties. Characterizing this tissue at different length scales is crucial for developing micromechanical models that optimize mechanical parameters, thereby controlling regeneration and preventing non-unions.
Overview of the EUROfusion Tokamak Exploitation programme in support of ITER and DEMO
(Institute of Physics Publishing, 2024-11-01) Jet Contributors; Ayllón Guerola, Juan Manuel; Cruz Zabala, Diego José; Domínguez Palacios Durán, Jesús José; Doyle, Scott James; Galdón Quiroga, Joaquín; García Muñoz, Manuel; Hidalgo Salaverri, Javier; Mancini, Alessio; McKay, Kiera Anne; Oyola Domínguez, Pablo; Rivero Rodríguez, Juan Francisco; Romero Madrid, Carlos Francisco; Rueda Rueda, José; Toscano Jiménez, Manuel; Van Vuuren, Anton Jansen; Velarde Gallardo, Lina; Viezzer, Eleonora; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Universidad de Sevilla. Departamento de Física Aplicada III; Universidad de Sevilla. Departamento de Ingeniería Energética; Universidad de Sevilla. Departamento de Ingeniería Mecánica y de Fabricación; EUROfusion Consortium
Within the 9th European Framework programme, since 2021 EUROfusion is operating five tokamaks under the auspices of a single Task Force called ‘Tokamak Exploitation’. The goal is to benefit from the complementary capabilities of each machine in a coordinated way and help in developing a scientific output scalable to future largre machines. The programme of this Task Force ensures that ASDEX Upgrade, MAST-U, TCV, WEST and JET (since 2022) work together to achieve the objectives of Missions 1 and 2 of the EUROfusion Roadmap: i) demonstrate plasma scenarios that increase the success margin of ITER and satisfy the requirements of DEMO and, ii) demonstrate an integrated approach that can handle the large power leaving ITER and DEMO plasmas. The Tokamak Exploitation task force has therefore organized experiments on these two missions with the goal to strengthen the physics and operational basis for the ITER baseline scenario and for exploiting the recent plasma exhaust enhancements in all four devices (PEX: Plasma EXhaust) for exploring the solution for handling heat and particle exhaust in ITER and develop the conceptual solutions for DEMO. The ITER Baseline scenario has been developed in a similar way in ASDEX Upgrade, TCV and JET. Key risks for ITER such as disruptions and run-aways have been also investigated in TCV, ASDEX Upgrade and JET. Experiments have explored successfully different divertor configurations (standard, super-X, snowflakes) in MAST-U and TCV and studied tungsten melting in WEST and ASDEX Upgrade. The input from the smaller devices to JET has also been proven successful to set-up novel control schemes on disruption avoidance and detachment.
Experimental research on the TCV tokamak
(Institute of Physics Publishing, 2024-10-29) Duval, B. P.; Abdolmaleki, A.; Agostini, M.; Ajay, C. J.; Alberti, S.; Alessi, E.; Anastasiou, G.; Andrèbe, Y.; Apruzzese, G. M.; Ayllón Guerola, Juan Manuel; Galdón Quiroga, Joaquín; García Muñoz, Manuel; Gil, L.; Zurita, M.; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Universidad de Sevilla. Departamento de Ingeniería Mecánica y de Fabricación; EUROfusion Consortium; Department of Energy. United States
Tokamak à configuration variable (TCV), recently celebrating 30 years of near-continual operation, continues in its missions to advance outstanding key physics and operational scenario issues for ITER and the design of future power plants such as DEMO. The main machine heating systems and operational changes are first described. Then follow five sections: plasma scenarios. ITER Base-Line (IBL) discharges, triangularity studies together with X3 heating and N2 seeding. Edge localised mode suppression, with a high radiation region near the X-point is reported with N2 injection with and without divertor baffles in a snowflake configuration. Negative triangularity (NT) discharges attained record, albeit transient, βN ∼ 3 with lower turbulence, higher low-Z impurity transport, vertical stability and density limits and core transport better than the IBL. Positive triangularity L-Mode linear and saturated ohmic confinement confinement saturation, often-correlated with intrinsic toroidal rotation reversals, was probed for D, H and He working gases. H-mode confinement and pedestal studies were extended to low collisionality with electron cyclotron heating obtaining steady state electron iternal transport barrier with neutral beam heating (NBH), and NBH driven H-mode configurations with off-axis co-electron cyclotron current drive. Fast particle physics. The physics of disruptions, runaway electrons and fast ions (FIs) was developed using near-full current conversion at disruption with recombination thresholds characterised for impurity species (Ne, Ar, Kr). Different flushing gases (D2, H2) and pathways to trigger a benign disruption were explored. The 55 kV NBH II generated a rich Alfvénic spectrum modulating the FI fas ion loss detector signal. NT configurations showed less toroidal Alfvén excitation activity preferentially affecting higher FI pitch angles. Scrape-off layer and edge physics. gas puff imaging systems characterised turbulent plasma ejection for several advanced divertor configurations, including NT. Combined diagnostic array divertor state analysis in detachment conditions was compared to modelling revealing an importance for molecular processes. Divertor physics. Internal gas baffles diversified to include shorter/longer structures on the high and/or low field side to probe compressive efficiency. Divertor studies concentrated upon mitigating target power, facilitating detachment and increasing the radiated power fraction employing alternative divertor geometries, optimised X-point radiator regimes and long-legged configurations. Smaller-than-expected improvements with total flux expansion were better modelled when including parallel flows. Peak outer target heat flux reduction was achieved (>50%) for high flux-expansion geometries, maintaining core performance (H98 > 1). A reduction in target heat loads and facilitated detachment access at lower core densities is reported. Real-time control. TCV’s real-time control upgrades employed MIMO gas injector control of stable, robust, partial detachment and plasma β feedback control avoiding neoclassical tearing modes with plasma confinement changes. Machine-learning enhancements include trajectory tracking disruption proximity and avoidance as well as a first-of-its-kind reinforcement learning-based controller for the plasma equilibrium trained entirely on a free-boundary simulator. Finally, a short description of TCV’s immediate future plans will be given.
Divertor Tokamak Test facility project: status of design and implementation
(Institute of Physics (IOP Publishing), 2024-11-01) Romanelli, F.; Ayllón Guerola, Juan Manuel; Galdón Quiroga, Joaquín; García López, Javier; García Muñoz, Manuel; Hidalgo Salaverri, J.; Rueda Rueda, José; Universidad de Sevilla. Departamento de Ingeniería Mecánica y de Fabricación; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Universidad de Sevilla. Departamento de Construcciones Arquitectónicas I (ETSA); European Union (UE); Universidad de Sevilla. FQM402: Ciencias y Tecnologías del Plasma y el Espacio; Universidad de Sevilla. TEP130: Aquitectura, Patrimonio y Sostenibilidad: Acústica, Iluminación, Óptica y Energía
An overview is presented of the progress since 2021 in the construction and scientific programme preparation of the Divertor Tokamak Test (DTT) facility. Licensing for building construction has been granted at the end of 2021. Licensing for Cat. A radiologic source has been also granted in 2022. The construction of the toroidal field magnet system is progressing. The prototype of the 170 GHz gyrotron has been produced and it is now under test on the FALCON facility. The design of the vacuum vessel, the poloidal field coils and the civil infrastructures has been completed. The shape of the first DTT divertor has been agreed with EUROfusion to test different plasma and exhaust scenarios: single null, double null, X-divertor and negative triangularity plasmas. A detailed research plan is being elaborated with the involvement of the EUROfusion laboratories.
EUROfusion contributions to ITER nuclear operation
(Institute of Physics (IOP Publishing), 2024-11) Litaudon, X.; Galdón Quiroga, Joaquín; García Muñoz, Manuel; Gonzalez Martin, Javier; Sanchis Sánchez, Lucía; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Universidad de Sevilla. Departamento de Ingeniería Mecánica y de Fabricación; European Union (UE); Academy of Finland; Universidad de Sevilla. FQM402: Ciencias y Tecnologías del Plasma y el Espacio
ITER is of key importance in the European fusion roadmap as it aims to prove the scientific and technological feasibility of fusion as a future energy source. The EUROfusion consortium of labs within Europe is contributing to the preparation of ITER scientific exploitation and operation and aspires to exploit ITER outcomes in view of DEMO. The paper provides an overview of the major progress obtained recently, carried out in the frame of the new (initiated in 2021) EUROfusion work-package called 'Preparation of ITER Operation' (PrIO). The overview paper is directly supported by the eleven EUROfusion PrIO contributions given at the 29th Fusion Energy Conference (16–21 October 2023) London, UK [www.iaea.org/events/fec2023]. The paper covers the following topics: (i) development and validation of tools in support to ITER operation (plasma breakdown/burn-through with evolving plasma volume, new infra-red synthetic diagnostic for off-line analysis and wall monitoring using Artificial Intelligence techniques, synthetic diagnostics development, development and exploitation of multi-machine databases); (ii) R&D for the radio-frequency ITER neutral beam sources leading to long duration of negative deuterium/hydrogen ions current extraction at ELISE and participation in the neutral beam test facility with progress on the ITER source SPIDER, and, the commissioning of the 1 MV high voltage accelerator (MITICA) with lessons learned for ITER; (iii) validation of neutronic tools for ITER nuclear operation following the second JET deuterium–tritium experimental campaigns carried out in 2021 and in 2023 (neutron streaming and shutdown dose rate calculation, water activation and activated corrosion products with advanced fluid dynamic simulation; irradiation of several materials under 14.1 MeV neutron flux etc).
Estudio de fuerzas elasticas en elementos finitos formulados en coordenadas nodales absolutas
(Asociación Española de Ingeniería Mecánica, 2008) García Vallejo, Daniel; García Martín, D.; Escalona Franco, José Luis; Universidad de Sevilla. Departamento de Ingeniería Mecánica y de Fabricación; Ministerio de Educación y Ciencia (MEC). España; Universidad de Sevilla. TEP111: Ingenieria Mecanica
Actualmente existen determinados elementos finitos tipo viga basados en la formulación en coordenadas nodales absolutas (ANCF). Entre ellos, el elemento finito tipo viga Euler-Bermoulli parametrizado por su línea media es ampliamente utilizado.
Formulación espacial de sistemas multicuerpo con sólidos rígidos y flexibles mediante coordenadas absolutas
(Asociación Espñaola de Ingeniería Mecánica (AEIM), 2004) García Vallejo, Daniel; Mayo Núñez, Juana María; Escalona Franco, José Luis; Domínguez Abascal, Jaime; Universidad de Sevilla. Departamento de Ingeniería Mecánica y de Fabricación; García Vallejo, Daniel; Comisión Interministerial de Ciencia y Tecnología (CICYT). España; Universidad de Sevilla. TEP111: Ingenieria Mecanica
El uso de matrices de masa constantes en mecanismos rígido-flexibles de barra da lugar a ecuaciones en las que no aparecen términos de fuerzas de inercia centrífugas y de Coriolis, además, la factorización de la matriz de masa solo se hace una vez. Las formulaciones en coordenadas nodales absolutas y naturales ofrecen dichas ventajas para sólidos flexibles y rígidos, respectivamente. Ambas utilizan el mismo tipo de variables, lo cual permite reducir enormemente el conjunto de ecuaciones de restricción.
Beam modulation and bump-on-tail effects on Alfvén eigenmode stability in DIII-D
(Institute of Physics Publishing, 2021-05) Van Zeeland, Michael A.; Bardóczi, László; Gonzalez Martin, Javier; Heidbrink, William W.; García Muñoz, Manuel; Wang, Xin; Universidad de Sevilla. Departamento de Ingeniería Mecánica y de Fabricación; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; European Union (UE)
Beam modulation effects on Alfvén eigenmode stability have been investigated in a recent DIII-D experiment and show that variations in neutral beam modulation period can have an impact on the beam driven Alfvén eigenmode spectrum and resultant fast ion transport despite similar time-averaged input power. The experiment was carried out during the current ramp phase of L-mode discharges heated with sub-Alfvénic 50-80 kV deuterium neutral beams that drive a variety of Alfvén eigenmodes unstable. The modulation period of two interleaved beams with different tangency radii was varied from shot to shot in order to modify the relative time dependent mix of the beam pitch angle distribution as well as the persistence of a bump-on-tail feature near the injection energy (a feature confirmed by imaging neutral particle analyzer measurements). As the beam modulation period is varied from 7 ms to 30 ms on/off (typical full energy slowing down time of τ slow ≈ 50 ms at mid-radius), toroidicity-induced Alfvén eigenmodes (TAEs) located in the outer periphery of the plasma become intermittent and coincident with the more tangential beam. Core mode activity changes from reversed shear Alfvén eigenmodes (RSAEs) to a mix of RSAE and beta-induced Alfvén eigenmodes. Discharges with 30 ms on/off period do not have a persistent bump-on-tail feature, have the lowest average mode amplitude and least fast ion transport. Detailed analysis of an individual TAE using TRANSP kick modeling (Monte Carlo evolution of the distribution function with probabilistic 'kicks' by the AEs) and the resistive MHD code with kinetic fast ions, MEGA, find no strong role of energy gradient drive due to bump-on-tail features. Instead, the observed TAE modulation with interleaved beams is likely a pitch angle dependent result combined with slowing down of the tangential beam between pulses. For the conditions investigated, bump-on-tail contributions to TAE drive were found to be 5% or less of the total drive at any given time.
Predicting Rail Corrugation Based on Convolutional Neural Networks Using Vehicle’s Acceleration Measurements
(2024-07) Haghbin, Masoud; Chiachío Ruano, Juan; Muñoz Moreno, Sergio; Escalona Franco, José Luis; Guillén López, Antonio Jesús; Crespo Márquez, Adolfo; Cantero-Chinchilla, Sergio; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Universidad de Sevilla. Departamento de Ingeniería Mecánica y de Fabricación; Universidad de Sevilla. Departamento de Organización Industrial y Gestión de Empresas I; Junta de Andalucía; Universidad de Sevilla. TEP123: Metalurgia e Ingeniería de los Materiales; Universidad de Sevilla. TEP134: Organización Industrial; Universidad de Sevilla. TEP111: Ingeniería Mecánica
This paper presents a deep learning approach for predicting rail corrugation based on on-board rolling-stock vertical acceleration and forward velocity measurements using One-Dimensional Convolutional Neural Networks (CNN-1D). The model’s performance is examined in a 1:10 scale railway system at two different forward velocities. During both the training and test stages, the CNN-1D produced results with mean absolute percentage errors of less than 5% for both forward velocities, confirming its ability to reproduce the corrugation profile based on real-time acceleration and forward velocity measurements. Moreover, by using a Gradient-weighted Class Activation Mapping (Grad-CAM) technique, it is shown that the CNN-1D can distinguish various regions, including the transition from damaged to undamaged regions and one-sided or two-sided corrugated regions, while predicting corrugation. In summary, the results of this study reveal the potential of data-driven techniques such as CNN-1D in predicting rails’ corrugation using online data from the dynamics of the rolling-stock, which can lead to more reliable and efficient maintenance and repair of railways.
Analysing the mechanisms of failure in polycarbonate sheets deformed by SPIF
(Elsevier, 2024-07-01) Rosa-Sainz, Ana; Magrinho, J. P.; Vaz, M. F.; Silva, Maria Beatriz; Centeno Báez, Gabriel; Vallellano Martín, Carpóforo; Universidad de Sevilla. Departamento de Ingeniería Mecánica y de Fabricación; Ministerio de Ciencia, Innovación y Universidades (MICINN). España; European Union (UE); Fundação para a Ciência e a Tecnologia. Portugal; Universidad de Sevilla. TEP111: Ingeniería Mecánica
This article presents experimental research conducted on polycarbonate sheets deformed via single-point incremental forming (SPIF). Building upon established frameworks from previous studies, the analysis focuses on evaluating the formability and failure modes, particularly necking and fracture, of polymeric sheets in both conventional and incremental forming processes. The experimental design encompasses an investigation of spindle speed and step down process parameters, utilizing both oil and water as lubricants, to comprehensively assess their effects. The findings provide insights into how these parameters influence formability and affect the failure mode. When using oil as a lubricant, three distinct failure modes were observed during deformation: fracture, twisting, and crazing. An increased twisting was associated with higher step down values, whereas elevated spindle speeds contributed to increase crazing. Additionally, these tests revealed a “post-crazing” failure mode following deformation. Conversely, when water was used as a lubricant, only fracture and twisting were observed in the SPIF specimens. This work introduces, for the first time ever, a complete investigation of these failure modes through scanning electron microscopy analysis of the failure surface. This analysis scrutinizes surface features and interprets them, thus providing a valuable tool for failure analysis.
Fracture in stretch flanging by single point incremental forming
(Elsevier, 2024-09) López Fernández, José Andrés; Borrego Puche, Marcos; Centeno Báez, Gabriel; Vallellano Martín, Carpóforo; Universidad de Sevilla. Departamento de Ingeniería Mecánica y de Fabricación; Ministerio de Ciencia e Innovación (MICIN). España; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); Ministerio de Ciencia, Innovación y Universidades (MICINN). España; European Union (UE); Universidad de Sevilla. TEP111: Ingeniería Mecánica.
This study presents a comprehensive investigation of fracture in open-stretched flanges formed using Single Point Incremental Forming (SPIF) on AA2024-T3 aluminium sheets. The work systematically explores the impact of geometric parameters, namely initial width and length, on the occurrence of the two primary failure modes: fracture at the corner and fracture at the edge of the flange. The experimental campaign comprises a series of flanging tests on medium-small radii to examine the deformation process on both the inner and outer surfaces of the flanges. The novelty of the investigation lies in two key aspects. Firstly, it offers, for the first time, an experimental characterisation of the onset of failure at the flange corner, which significantly limits the process's capabilities, and critically compares it with the failure at the flange edge. It is highlighted that the fracture at the corner is strongly influenced by tool-induced friction and the incremental nature of the SPIF process, resulting in a local formability significantly higher than expected with a quasi-proportional deformation process, as characterised by the conventional Fracture Forming Limit (FFL) evaluated through Nakazima tests. Secondly, a detailed formability analysis of the flange in the average stress triaxiality versus equivalent strain space is conducted, identifying a common region of Mode I fracture for plane stress applicable to both open-stretched flanges by SPIF and conventional Nakazima tests. To this end, an explicit numerical model based on the Barlat-89 anisotropic yield criterion is used to assess the non-proportional strain/stress paths, inherent in the incremental process. A numerical-experimental methodology is employed to predict both edge and corner failures of the flanges within the average stress triaxiality - equivalent strain space. The fracture loci for Mode I have been determined for both the incremental flanging tests and the Nakazima tests. A comparison of both fracture loci reveals a noticeably lower average stress triaxiality and larger equivalent strain in the SPIFed flanges than in the Nakazima tests, consistent with the increase in the apparent formability of the material observed experimentally in the incremental processes with respect to the conventional tests.

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