Artículos (Ingeniería Mecánica y Fabricación)

URI permanente para esta colecciónhttps://hdl.handle.net/11441/11372

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Risk of fragility fracture is aggravated during bone regeneration processes in osteoporotic sheep
(Public Library of Science (PLOS), 2025) Toscano Angulo, Juan José; Mora Macías, Juan; Blázquez Carmona, Pablo; Morgaz, Juan; Navarrete Calvo, Rocío; Domínguez Abascal, Jaime; Reina Romo, Esther; Universidad de Sevilla. Departamento de Ingeniería Mecánica y Fabricación; Ministerio de Ciencia, Innovación y Universidades (MICIU). España; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER)
Introduction: Bone regeneration processes are associated with a systemic skeletal change in bone quality, increasing the risk of fragility fractures. This condition may be aggravated in osteoporotic patients due to their limited osteogenic capacity. This work evaluates the impairment of the bone quality in osteoporotic sheep during a bone regeneration process. It provides a deeper understanding about the complex multiscale dynamics of bone mineral density, microstructure and chemical composition across different bone tissues, locations and time points. Materials and Methods: Osteoporosis was induced in fifteen Merino sheep. A critical-size defect was then created in the sheep’s right hind metatarsus and subsequently regenerated using distraction osteogenesis. The animals were randomly sacrificed during bone regeneration, either on days 40 or 100 after surgery. Computed tomography, micro computed tomography and chemical composition analyses were conducted on different bone tissues (cortical, trabecular and woven) at several skeletal locations (the operated metatarsus, the contralateral one and the iliac crest) to assess the individual bone quality changes relative to the non-osteoporotic time point. Results: After osteoporosis induction, the trabecular tissue experienced a 6.4% reduction in the bone mineral density, while no significant changes were reported in cortical tissue quality. During bone regeneration, the operated bone increased significantly the woven ossification whilst the cortical mineral density decreased by 18.7%. Simultaneously, an early deterioration in the microstructure and chemical composition of the trabecular bone was observed in the iliac crest, persisting over time in non-operated trabecular regions. Conclusions: Osteoporosis causes uneven degradation to trabecular tissue quality across different bone locations. Furthermore, the bone regeneration process via bone transport in osteoporotic subjects leads to a systemic skeletal disorder that further impairs the bone quality, surpassing the damage caused by osteoporosis alone. This impairment appears to be intensified by the pre-existing osteoporotic condition.
Analysis of biaxial fatigue limit models for cases with circular notches
(Elsevier, 2022-09) Chaves Repiso, Víctor Manuel; Navarro Robles, Alfredo; Susmel, Luca; Taylor, D.; Universidad de Sevilla. Departamento de Ingeniería Mecánica y Fabricación; Ministerio de Ciencia e Innovación (MICIN). España; Junta de Andalucía; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); Universidad de Sevilla. TEP111: Ingeniería Mecánica
This work shows an analysis of several models of multiaxial fatigue for notches: Navarro-Rios’ model, which analyses the interaction between the crack and its associated plastic zone with the material microstructural barriers, and three models that combine a critical volume method for notches with a critical plane model for multiaxial fatigue in unnotched solids. Specifically, the application of these models for the prediction of the fatigue limit for a plate with a circular hole subjected to axial, shear and in-phase biaxial cyclic loading is studied. The effects of two parameters are analysed: the radius of the hole and the relationship between the torsional and axial fatigue limits. For all the analysed models, cases are observed in which an increase in the hole radius produces an increase in the predicted fatigue limit, that is, the evolution of the fatigue limit with an increasing hole radius is not always monotonically decreasing, as would be expected. These effects, which we have called “humps” because of their appearance on the prediction graphs, mainly occur in shear loading. No humps were observed in the studied experimental results, but the number of available experimental results is too small to assure this tendency. The results shown in the work indicate that a greater knowledge of the physics of multiaxial fatigue in notches is necessary to achieve models that are capable of providing increasingly accurate predictions.
A simplified Navarro-Rios model to predict fatigue limits in notched components
(Elsevier, 2021-08) Chaves Repiso, Víctor Manuel; Universidad de Sevilla. Departamento de Ingeniería Mecánica y Fabricación; Ministerio de Economia, Industria y Competitividad (MINECO). España; Universidad de Sevilla. TEP111: Ingeniería Mecánica
Many methods have been proposed to predict fatigue failure in the presence of notches, among which is the Navarro-Rios model. This model is based on short-crack fracture mechanics. Specifically, the model analyses the capacity of the crack, which is formed at the notch root by cyclic loading, to overcome successive microstructural barriers such as grain boundaries. This model provides a fairly reasonable explanation of crack growth from a notch under cyclic loading and has been successfully used for many years to predict the fatigue limit in some notched geometries, as shown in several published works. However, the application of this model is not easy, mainly for two reasons: the first is that to build the equations of the model, it is necessary to know the stress field generated by a dislocation in the vicinity of the specific notch, which is a complicated elasticity problem except for very simple notch geometries. The second is related to the resolution of the equations of the model, which are singular integral equations that are difficult to solve except for very simple cases. This work shows a simplified version of the Navarro-Rios model, which allows us to overcome these two difficulties. First, the elastic problem of a dislocation near a notch is simplified to that of a dislocation in an infinite medium, which has a known analytical solution. Second, the study of the equilibrium at the crack line is simplified by using the elastic stress at the midpoint of the crack line instead of using the full stress gradient. After this simplification, the singular integral equation has a known and simple solution. This simplified Navarro-Rios model is applied to some notched geometries and provides similar fatigue limit predictions to those of the classic Navarro-Rios model. It is also compared with results in the literature, where it provides similar predictions to the experimental fatigue limits. The simplified Navarro-Rios model can be a relatively simple alternative to critical distance models for predicting the fatigue limit in notched solids.
Divertor shaping with neutral baffling as a solution to the tokamak power exhaust challenge
(Nature Research, 2025-05-23) Verhaegh, Kevin; Harrison, James; Moulton, David; Lipschultz, Bruce; Lonigro, Nicola; Osborne, Nick; Lingyan, Xiang; The EUROfusion Tokamak Exploitation Team; The MAST Upgrade Team; 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; Van Vuuren, Anton Jansen; Mancini, Alessio; McKay, Kiera Anne; Oyola Domínguez, Pablo; Rivero Rodríguez, Juan Francisco; Romero Madrid, Carlos Francisco; Rueda Rueda, José; Toscano Jiménez, Manuel; Velarde Gallardo, Lina; Viezzer, Eleonora; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Universidad de Sevilla. Departamento de Ingeniería Mecánica y Fabricación; Engineering and Physical Sciences Research Council (UK); US Department of Energy; European Union (UE)
Exhausting power from the hot fusion core to the plasma-facing components is one fusion energy’s biggest challenges. The MAST Upgrade tokamak uniquely integrates strong containment of neutrals within the exhaust area (divertor) with extreme divertor shaping capability. By systematically altering the divertor shape, this study shows the strongest evidence to date to our knowledge that long-legged divertors with a high magnetic field gradient (total flux expansion) deliver key power exhaust benefits without adversely impacting the hot fusion core. These benefits are already achieved with relatively modest geometry adjustments that are more feasible to integrate in reactor designs. Benefits include reduced target heat loads and improved access to, and stability of, a neutral gas buffer that ‘shields’ the target and enhances power exhaust (detachment). Analysis and model comparisons shows these benefits are obtained by combining multiple shaping aspects: long-legged divertors have expanded plasma-neutral interaction volume that drive reductions in particle and power loads, while total flux expansion enhances detachment access and stability. Containing the neutrals in the exhaust area with physical structures further augments these shaping benefits. These results demonstrate strategic variation in the divertor geometry and magnetic topology is a potential solution to one of fusion’s power exhaust challenge.
Efficient computation of the magnetic field created by a toroidal volumetric current of convex cross section with application to the study of the magnetic confinement in tokamaks
(Elsevier, 2025-08) Camacho Aguilar, Miguel; Rodríguez Boix, Rafael; Cruz Zabala, Diego José; Galdón Quiroga, Joaquín; Ayllón Guerola, Juan Manuel; Viezzer, Eleonora; Universidad de Sevilla. Departamento de Ingeniería Mecánica y Fabricación; Universidad de Sevilla. Departamento de Electrónica y Electromagnetismo; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Ministerio de Ciencia, Innovación y Universidades (MICIU). España; European Union (UE); European Research Council (ERC)
In this paper we present an efficient approach for the numerical computation of the static vector potential and the poloidal magnetic field of a toroidal volumetric current with arbitrary convex cross section. The standard integral expressions for both the vector potential and the magnetic field include singularities that have a deleterious effect in the computation of these integrals. In order to handle these singularities, we first introduce a change of variables to polar coordinates with origin at the observation point that makes it possible to remove the singularities of the integrands thanks to the Jacobian factor. Then, two different numerical integration methods are applied to the resulting integrals: Ma-Rokhlin-Wandzura quadrature rules and the double exponential quadrature rule. Both methods efficiently handle the singularities in the derivative of the integrand for the integrals of the vector potential and the magnetic field, and the advantages and disadvantages of each method are discussed. The results obtained for the vector potential and magnetic field are validated by comparing with closed-form results existing for the vector potential and magnetic field of a circular loop and an infinite cylinder, and good agreement is found. Then, the magnetic field code is used to model the plasma toroidal current in a tokamak nuclear fusion reactor, and it is shown that the combined magnetic field of the plasma current and that of the poloidal and toroidal coils leads to magnetic confinement of the charged particles existing in the plasma.
Multiscale characterization of the mechanics of curved fibered structures with application to biological and engineered materials
(Elsevier, 2025-04-01) Sanz Herrera, José Antonio; Apolinar Fernández, Alejandro; JIménez Aires, A.; Pérez Alcántara, P.; Domínguez Abascal, Jaime; Reina Romo, Esther; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Universidad de Sevilla. Departamento de Ingeniería Mecánica y Fabricación; Ministerio de Ciencia e Innovación (MICIN). España; Agencia Estatal de Investigación. España; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); Junta de Andalucía; Universidad de Sevilla. TEP245: Ingeniería de las Estructuras; Universidad de Sevilla. TEP111: Ingeniería Mecánica
Curved fibered structures are ubiquitous in nature and the mechanical behavior of these materials is of pivotal importance in the biomechanics and mechanobiology fields. We develop a multiscale formulation to characterize the macroscopic mechanical nonlinear behavior from the microstructure of fibered matrices. From the analysis of the mechanics of a randomly curved single fiber, a fibered matrix model is built to determine the macroscopic behavior following a homogenization approach. The model is tested for tensile, compression and shear loads in different applications. The presented approach naturally recovers instabilities at compression as well as the strain stiffening regime, which are observed experimentally in the mechanical behavior of collagen matrices. Indeed, it was found that the bending energy associated to fiber unrolling, is the most important source of energy developed by fibers for the analyzed cases in tensile and shear in all deformation regions (except the strain stiffening region), whereas bending energy dominates at compression too during buckling. The proposed computational framework can also be used to perform multiscale simulations in engineered fibered materials. Therefore, the developed methodology may be an interesting and complementary tool to characterize the nonlinear behavior and evolution of curved fibered structures present in biology and engineering.
Validation of the Synthetic Model for the Imaging Heavy ion Beam Probe at the ASDEX Upgrade Tokamak (invited)
(AIP Publishing, 2024) Oyola Domínguez, Pablo; Birkenmeier, G.; Lindl, H.; Galdón Quiroga, Joaquín; Rueda Rueda, José; Viezzer, Eleonora; Rodríguez González, A.; Hidalgo Salaverri, Javier; García Muñoz, Manuel; Tal, B.; Anda, G.; Kalis, J.; Lunt, T.; Refy, D.; Videla Trevin, M.; ASDEX Upgrade Team; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Universidad de Sevilla. Departamento de Ingeniería Mecánica y Fabricación; Ministerio de Ciencia e Innovación (MICIN). España; Helmholtz Association. Alemania; European Union (UE). H2020; European Union (UE)
Recent experiments at the ASDEX Upgrade tokamak have provided the first ever measurements from the imaging heavy-ion beam probe. In this work, we show that the developed simulation framework can reproduce qualitatively the measurement's observed shape and position. Quantitatively, we demonstrate that the model reproduces, within the experimental uncertainties, the observed signal levels. A detailed explanation of the synthetic model is presented, along with the calibration of the optical setup that reproduces the measurements.
Rope–sheave contact transient analysis in hoisting operations with a bristle model and an arbitrary Lagrangian–Eulerian approach
(Springer, 2025) Escalona Franco, José Luis; Universidad de Sevilla. Departamento de Ingeniería Mecánica y Fabricación; European Union (UE). H2020
This paper describes the development of a computational model for the rope–sheave contact interaction in reeving systems when the ropes are modeled with an arbitrary Lagrangian–Eulerian approach. This discretization approach has been developed in previous publications as a general and systematic method for the modeling and simulation of reeving systems. However, the rope–sheave contact model was avoided assuming the no-slip contact condition. The contact model developed in this paper introduces specialized ALE-ANCF-cubic rope contact elements that are used to discretize the rope segment winded at the sheave. The contact is modeled using a set of virtual discrete bristles attached to material points in the mid-line of the rope in one end and in contact with the sheave in the other end. Therefore, a second Lagrangian mesh, apart of the ALE mesh used to discretize the rope, is used to define the fixed ends of the bristles. The kinematics and dynamics used to calculate the normal and tangential contact forces are described in detail. The contact model is 3D and can be used to analyze the contact with a sheave groove with arbitrary shape. The tangential contact force model can be used to describe stick and slip contact conditions and, to improve the simulation performance of the model, an LuGre regularization tangential contact force model is used. The rope-sheave contact model is used to analyze the behavior of a simple elevator system. The numerical results show that the static rope-sheave contact interaction agrees well with an analytical solution of the problem. Finally, the same elevator system is analyzed dynamically for a cabin ride of 8 meters with a steady velocity of 1 m/s. Results show that the normal and tangential contact forces during the steady velocity period are not so different from the static solution, but very different from the classical Creep Theory and Firbank’s Theory.
Velocity-space analysis of fast-ion losses measured in MAST-U using a high-speed camera in the FILD detector
(IOP Publishing, 2025) Velarde Gallardo, Lina; Rivero Rodríguez, Juan Francisco; Galdón Quiroga, Joaquín; Williams, T.; Rueda Rueda, José; Cano Megías, Pilar; Chacartegui, Ricardo; García Muñoz, Manuel; Sanchis Sánchez, Lucía; Viezzer, Eleonora; Universidad de Sevilla. Departamento de Ingeniería Energética; Universidad de Sevilla. Departamento de Ingeniería Mecánica y Fabricación; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Consejería de Transformación Económica, Industria, Conocimiento y Universidades. Junta de Andalucía; European Research Council (ERC)
A fast-ion loss detector (FILD) was installed for the first time at the mega amp spherical tokamak—upgrade (MAST-U) spherical tokamak during its upgrade in 2021. A new CMOS camera was installed in the MAST-U FILD acquisition system to provide high spatial resolution (1.1 MPx) with an acquisition frequency of up to 3.5 kHz. This camera has enabled the systematic analysis of the velocity-space of the fast-ion losses measured in MAST-U presented in this manuscript. The main parameters that determine the FILD measurement have been analysed to maximise the signal in the detector: the orbit-following code ASCOT predicts an inverse relation between the FILD signal and the probe’s relative distance to the separatrix. This prediction has been validated experimentally, enabling the measurement of fast-ion losses in the flat-top phase of the discharge; furthermore, ASCOT simulations show a big impact of the edge safety factor (q95) on the toroidal deposition of the prompt losses, indicating that the signal in the MAST-U FILD can be maximised by running scenarios with | q 95 | < 6 . This prediction was validated experimentally by a scan in the toroidal magnetic field. The experimental resolution of the MAST-U FILD has been evaluated for a typical MAST-U scenario with 750 kA plasma current. The results show that the diagnostic resolution is in the order of 0.5 to 1 degree in pitch angle, and of 1 to 3 cm in gyroradius in current scenarios. A systematic analysis of the velocity-space of the losses shows that the measured gyroradii of the prompt losses match those of the neutral beam injector injection energies within the resolution of the diagnostic. The experimentally measured pitch angles have been compared with ASCOT simulations, and it has been found that the agreement is better for scenarios heated with the on-axis beam, since this beam enables measurements of the magnetic field pitch angle. This analysis has been applied to a discharge where type-III ELM-induced fast-ion losses were measured, showing that the ELMs result in an increase in the FILD signal, and that the losses are coming from passing orbits.
Hybrid hydrogen-electricity production using spherical tokamaks: a cost-driver sensitivity study and techno-economic analysis
(Iop Publishing Ltd, 2025) Hidalgo Salaverri, Javier; Griffiths, T; Conti, Z. X.; Cano Megías, Pilar; Chacartegui, Ricardo; Bluck, M; Ayllón Guerola, Juan Manuel; García Muñoz, Manuel; Viezzer, Eleonora; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Universidad de Sevilla. Departamento de Ingeniería Energética; Universidad de Sevilla. Departamento de Ingeniería Mecánica y Fabricación; European Union (UE)
Hybrid fusion power plants, which produce both hydrogen and electricity, are proposed as a way to decarbonise the fossil-fuel-dominated primary energy market and improve plant economics. The main cost drivers of a fusion power plant based on a spherical tokamak have been identified using statistical analysis (Morris and Sobol methods) from a wide range of cases obtained with the systems code PROCESS. The analysis reveals the importance of plasma physics and reactor geometry on power plant economics. Three scenarios of advancing technophysical assumptions (conservative, moderate and optimistic) have been chosen to study the integration of the fusion reactor with the power block (Rankine, He-Brayton or super-critical-CO2-Feher) and with the PEM electrolyser. The super-critical-CO2 cycle returns the best results for the studied temperature range (500 ◦C–800 ◦C), with an efficiency between 40%–56%. The modelled PEM is in line with current commercial models with a consumption of 51.97 kWh kg−1 H2. The economic feasibility of these scenarios has been explored for a set of learning factors that consider the cheapening of the capital costs tied to experience. The LCOE of these scenarios have been compared against current price ranges of solar, wind and fission power and the LCOH against PEM prices, showing that the moderate and optimistic scenarios could be competitive for learning factors lower than 0.5 and capacity factors larger than 0.7. An extrapolation of the optimistic scenario shows that the hybrid fusion power plant in the French and German market can improve the plant profits by 15% and 66% respectively.
Advances in mechanobiological pharmacokinetic-pharmacodynamic models of osteoporosis treatment – Pathways to optimise and exploit existing therapies
(Elsevier, 2024-09) Pivonka, Peter; Calvo Gallego, José Luis; Schmidt, Stephan; Martínez Reina, Francisco Javier; Universidad de Sevilla. Departamento de Ingeniería Mecánica y Fabricación; Ministerio de Ciencia e Innovación (MICIN). España; Australian Research Council (ARC), Industrial Transformation Training Centre for Joint Biomechanics; Universidad de Sevilla. TEP111: Ingeniería Mecánica
Osteoporosis (OP) is a chronic progressive bone disease which is characterised by reduction of bone matrix volume and changes in the bone matrix properties which can ultimately lead to bone fracture. The two major forms of OP are related to aging and/or menopause. With the worldwide increase of the elderly population, particularly age-related OP poses a serious health issue which puts large pressure on health care systems. A major challenge for development of new drug treatments for OP and comparison of drug efficacy with existing treatments is due to current regulatory requirements which demand testing of drugs based on bone mineral density (BMD) in phase 2 trials and fracture risk in phase 3 trials. This requires large clinical trials to be conducted and to be run for long time periods, which is very costly. This, together with the fact that there are already many drugs available for treatment of OP, makes the development of new drugs inhibitive. Furthermore, an increased trend of the use of different sequential drug therapies has been observed in OP management, such as sequential anabolic-anticatabolic drug treatment or switching from one anticatabolic drug to another. Running clinical trials for concurrent and sequential therapies is neither feasible nor practical due to large number of combinatorial possibilities. In silico mechanobiological pharmacokinetic-pharmacodynamic (PK-PD) models of OP treatments allow predictions beyond BMD, i.e. bone microdamage and degree of mineralisation can also be monitored. This will help to inform clinical drug usage and development by identifying the most promising scenarios to be tested clinically (confirmatory trials rather than exploratory only trials), optimise trial design and identify subgroups of the population that show benefit-risk profiles (both good and bad) that are different from the average patient. In this review, we provide examples of the predictive capabilities of mechanobiological PK-PD models. These include simulation results of PMO treatment with denosumab, implications of denosumab drug holidays and coupling of bone remodelling models with calcium and phosphate systems models that allows to investigate the effects of co-morbidities such as hyperparathyroidism and chronic kidney disease together with calcium and vitamin D status on drug efficacy.
Assessment of mechanical variables best describing bone remodelling responses based on their correlation with bone density
(2024-12) Martínez Reina, Francisco Javier; Ojeda Granja, Joaquín; Calvo Gallego, José Luis; Pivonka, Peter; Martelli, Saulo; Universidad de Sevilla. Departamento de Ingeniería Mecánica y Fabricación; Ministerio de Ciencia e Innovación (MICIN). España; Australian Research Council (ARC), Industrial Transformation Training Centre for Joint Biomechanics; Universidad de Sevilla. TEP111: Ingeniería Mecánica
Density distribution in bones can be estimated using bone remodelling models (BRM) and applying daily normal loads to assess the stress/strain state to which the bone is subjected. These models locally relate a certain mechanical stimulus, derived from the stress/strain state, directly to bone density or to its variation over time. The background of this idea is Frost’s Mechanostat Theory, which states that overloading states tend to increase bone density and disuse states tend to decrease it. Different variables have been proposed in the literature to measure the mechanical stimulus. Strain energy density (SED) and stresses have been commonly used as mechanical stimuli, but to date their use has not been justified with convincing arguments. In this paper we have selected several variables derived from stress and strain tensors and correlated them with the distribution of bone density in the femur of 13 elderly women to conclude which would be most appropriate for use as a mechanical stimulus in a BRM. We have performed this correlation analysis for six different activities: walking normally, fast walking, stair ascent, stair descent, rising from and sitting on a chair, and jumping in place. Musculoskeletal models were used to estimate joint reaction and muscle forces of each individual for each activity. These were applied to the corresponding finite element model of the femur to obtain stress and strain tensors at each point. The variables proposed as mechanical stimulus and derived from these tensors were correlated to the actual density obtained for each individual from CT-scans. Our results show that stress variables are the best correlated with density. In contrast, the correlations of SED are very weak, so it is not a good candidate for mechanical stimulus. Strains are also weakly correlated to density, but in this case because their distribution across the femur is rather uniform. This is in agreement with the Mechanostat Theory which states that bone reacts to load changes by changing its stiffness so to keep strains in a certain interval. Consequently, a plausible choice for a remodelling criterion could be keeping that strain uniformity.
Optimisation of romosozumab plus denosumab sequential treatments against postmenopausal osteoporosis. Insights from in silico simulations
(Springer Nature, 2025) Ruiz Lozano, Rocío; Calvo Gallego, José Luis; Pivonka, Peter; Martínez Reina, Francisco Javier; Universidad de Sevilla. Departamento de Ingeniería Mecánica y Fabricación; Ministerio de Ciencia e Innovación (MICIN). España; Australian Research Council (ARC), Industrial Transformation Training Centre for Joint Biomechanics; Universidad de Sevilla. TEP111: Ingeniería Mecánica
Drug treatments against osteoporosis are commonly divided into anti-catabolic and anabolic. Anti-catabolic drugs reduce bone turnover and increase bone mass mainly through mineralization of the existing bone matrix. Anabolic drugs, on the other hand, enhance osteoblastic activity, resulting in new bone formation. Treatments are often limited to a few years due to reported side effects, which increases fracture risk upon discontinuation. Switching to a different drug is a common strategy. However, it is not clear what is the best combination of a dual-drug therapy, the lapse between treatments and other parameters defining the combination. In this study, we conducted in silico trials to assess the efficacy of two drugs: denosumab (anti-catabolic) and romosozumab (anabolic and anti-catabolic). Our simulations indicate that starting treatment with romosozumab leads to greater bone mass gain. This is because anti-catabolic treatments reduce bone rate and, due to osteoblast-osteoclast coupling, the number of osteoblast precursors. Romosozumab increases the proliferation of these precursors, so their population should be maximised for optimal efficacy. Therefore, prior administration of an anti-catabolic drug may be counterproductive to the effectiveness of romosozumab. We also found that a rest period between treatments does not benefit bone mass gain. Furthermore, concurrent administration of romosozumab and denosumab results in greater bone mass gain and might be worth investigating in future clinical trials. Finally, we showed that reduction of fracture risk in patients undergoing sequential treatments is dose dependent and consequently, dosage could be optimised in a patient-specific manner.
Experimental study of the use of a transfer function to find rail corrugation from axle-box accelerations
(Elsevier, 2025-05) Yu, Xinxin; Muñoz Moreno, Sergio; Urda Gómez, Pedro; Fernández Aceituno, Javier; Rodríguez Gómez, Miguel; Escalona Franco, José Luis; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Universidad de Sevilla. Departamento de Ingeniería Mecánica y Fabricación; Consejería de Economía, Ciencia, Empresa y Universidades. Junta de Andalucía; Ministerio de Ciencia, Innovación y Universidades (MICIU). España; Universidad de Sevilla. TEP111: Ingeniería Mecánica; Universidad de Sevilla. TEP123: Metalurgia e Ingeniería de los Materiales
This investigation uses a scale vehicle-track experimental facility to study the calculation of rail corrugation using vertical accelerations measured in the axle-box of rail vehicles and a transfer function (TF). The rail corrugated profile is machined in the rail heads of the scale track following a periodic function with four harmonics. Experiments are performed with a scale bogie-like vehicle at different forward velocities in the range inspection velocities. Two simple analytical forms of the TF are studied: the kinematic TF, that assumes that the axle box follows the rail profile, and the TF of a 2-dof model of the vehicle-track system. For the vehicle response analysis, this work proposes to normalize the measured acceleration with the square of the forward velocity of the vehicle, that is assumed to be approximately constant. This normalized acceleration reduces the effect of the forward velocity on the TF. Experimental results show that the kinematic TF can be used to measure the track corrugation for moderate forward velocities providing reasonable but not accurate results. The limitation of the kinematic TF is mainly due to free flights and wheel rail curvature incompatibility. The measured axle-box accelerations may include frequency peaks that are not excitation frequencies and can distort the rail profile measurement. Results show that linear elastic models like the assumed 2-dof model do not explain the appearance of these non-excitation peaks.
Hybrid kinetic-MHD modeling of alpha-driven TAEs in the SPARC tokamak
(IOP Publishing, 2025-03) Tinguely, R. Alexander; González Martín, 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, Javier; 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.

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