Artículos (Ingeniería Mecánica y de Fabricación)
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Artículo 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 EspacioITER 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).Artículo 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 MecanicaActualmente 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.Artículo 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 MecanicaEl 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.Artículo 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.Artículo 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 MecánicaThis 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.Artículo 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 MecánicaThis 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.Artículo 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.Artículo Active control of Alfvén eigenmodes by external magnetic perturbations with different spatial spectra(Institute of Physics (IOP), 2024-07) González Martín, Javier; García Muñoz, Manuel; Galdón Quiroga, Joaquín; Todo, Y.; Domínguez Palacios Durán, Jesús José; Dunne, M.; Van Vuuren, Anton Jansen; Liu, Y. Q.; Sanchis Sánchez, Lucía; Spong, D.; Suttrop, W.; Wang, X.; Willensdorfer, M.; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Universidad de Sevilla. Departamento de Ingeniería Mecánica y de Fabricación; European Union (UE). H2020; Ministerio de Ciencia e Innovación (MICIN). España; ; Universidad de Sevilla. FQM402: Ciencias y Tecnologías del Plasma y el Espacio.Alfvén eigenmodes have been suppressed and excited in tokamak plasmas by (just) modifying the poloidal spectra of externally applied static magnetic perturbations. This effect is observed experimentally when toroidal spectra of n = 2, n = 4 as well as a mixed spectrum of n = 2 and n = 4 is applied. Under the n = 2 magnetic perturbations, the modes are excited or suppressed by modifying the coil phasing between the upper and the lower set of coils. Regardless of the absolute rotation, an even parity for the n = 4 perturbation is observed to reduce the amplitude of the Alfvénic instabilities, while an odd parity amplifies it. To combine the stabilizing (and destabilizing) effect of n = 2 and n = 4, a mixed spectrum is applied, finding similar reduction (and amplification) trends. However, the impact on the mode amplitude is more subtle, due to the reduced coil current required for a mixed spectrum. The signal level on the fast-ion loss detector is sensitive to the applied poloidal spectrum, which is consistent with Hamiltonian full-orbit modelling of an edge resonant transport layer activated by the 3D perturbative fields. An internal redistribution of the fast-ion population is induced, modifying the phase-space gradients driving the Alfvénic instabilities, and ultimately determining their existence. The calculated edge resonant layers for both n = 2 and n = 4 toroidal spectra are consistent with the observed suppressed and excited phases. Moreover, hybrid kinetic-magnetohydrodynamic (MHD) simulations reveal that this edge resonant transport layer overlaps in phase-space with the population responsible for the fast-ion drive. The results presented here may help to control fast-ion driven Alfvénic instabilities in future burning plasmas with a significant fusion born alpha particle population.Artículo Rope–sheave contact transient analysis in hoisting operations with a bristle model and an arbitrary Lagrangian–Eulerian approach(Springer, 2024-06) Escalona Franco, José Luis; Universidad de Sevilla. Departamento de Ingeniería Mecánica y de Fabricación; European Union (UE). H2020; Universidad de Sevilla; Universidad de Sevilla. TEP111: Ingeniería Mecánica.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.Artículo Design and analysis of a flexible linkage for robot safe operation in collaborative scenarios(Elsevier, 2015-04) López Martínez, Javier; Blanco Claraco, José Luis; García Vallejo, Daniel; Giménez Fernández, Antonio; Universidad de Sevilla. Departamento de Ingeniería Mecánica y de Fabricación; Ministerio de Ciencia e Innovación (MICIN). España; Universidad de Sevilla. TEP111: Ingeniería MecánicaOne of the most serious security issues for collaborative work between robots and humans is the potential damage caused by unexpected collisions between them. Intrinsically-safe systems are a must in order to assure safety for both, the user and the robot, under the worst-case scenario of a total failure of the control subsystem. This work contributes to the field of passive mechanical system safety. The proposed security system consists in a flexible linkage that splits a robot arm link in two parts. Such a linkage allows the link to remain completely rigid as long as a given torque threshold is not exceeded, with that threshold being configurable according to working conditions and safety considerations. Both theoretical and experimental tests demonstrate a significant reduction in the accelerations and forces generated by impacts between the end effector of a robot arm equipped with the proposed mechanism and a simplified human head model. © 2015 Elsevier Ltd. All rights reserved.Artículo Dynamical analysis and design of active orthoses for spinal cord injured subjects by aesthetic and energetic optimization(Springer, 2016-04) García Vallejo, Daniel; Font-Llagunes, J.M.; Schiehlen, W.; Universidad de Sevilla. Departamento de Ingeniería Mecánica y de Fabricación; Universidad de Sevilla. TEP111: Ingeniería MecánicaThe dynamic analysis and simulation of human gait using multibody dynamics techniques has been a major area of research in the last decades. Nevertheless, not much attention has been paid to the analysis and simulation of robotic-assisted gait. Simulation is a very powerful tool both for assisting the design stage of active rehabilitation robots and predicting the subject–orthoses cooperation and the resulting aesthetic gait. This paper presents a parameter optimization approach that allows simulating gait motion patterns in the particular case of a subject with incomplete spinal cord injury (SCI) wearing active knee–ankle–foot orthoses at both legs. The subject is modelled as a planar multibody system actuated through the main lower limb muscle groups. A muscle force-sharing problem is solved to obtain optimal muscle activation patterns. Furthermore, denervation of muscle groups caused by the SCI is parameterized to account for different injury severities. The active orthoses are modelled as external devices attached to the legs, and their dynamic and performance parameters are taken from a real prototype. Numerical results using energetic and aesthetic objective functions, and considering different SCI severities are obtained. Detailed discussions are given related to the different motion and actuation patterns both from muscles and orthoses. The proposed methodology opens new perspectives towards the prediction of human-assisted gait, which can be very helpful for the design of new rehabilitation robots. © 2015, Springer Science+Business Media Dordrecht.Artículo Direct sensitivity analysis of multibody systems with holonomic and nonholonomic constraints via an index-3 augmented Lagrangian formulation with projections(Springer, 2018-09) Dopico, Daniel; González, Francisco; Luaces, Alberto; Saura, Mariano; García Vallejo, Daniel; Universidad de Sevilla. Departamento de Ingeniería Mecánica y de Fabricación; Ministerio de Economía y Competitividad (MINECO). España; Universidad de Sevilla. TEP111: Ingeniería MecánicaOptimizing the dynamic response of mechanical systems is often a necessary step during the early stages of product development cycle. This is a complex problem that requires to carry out the sensitivity analysis of the system dynamics equations if gradient-based optimization tools are used. These dynamics equations are often expressed as a highly nonlinear system of ordinary differential equations or differential-algebraic equations, if a dependent set of generalized coordinates with its corresponding kinematic constraints is used to describe the motion. Two main techniques are currently available to perform the sensitivity analysis of a multibody system, namely the direct differentiation and the adjoint variable methods. In this paper, we derive the equations that correspond to the direct sensitivity analysis of the index-3 augmented Lagrangian formulation with velocity and acceleration projections. Mechanical systems with both holonomic and nonholonomic constraints are considered. The evaluation of the system sensitivities requires the solution of a tangent linear model that corresponds to the Newton–Raphson iterative solution of the dynamics at configuration level, plus two additional nonlinear systems of equations for the velocity and acceleration projections. The method was validated in the sensitivity analysis of a set of examples, including a five-bar linkage with spring elements, which had been used in the literature as benchmark problem for similar multibody dynamics formulations, a point-mass system subjected to nonholonomic constraints, and a full-scale vehicle model. © 2018, Springer Science+Business Media B.V., part of Springer Nature.Artículo Thermo-mechanical assessment of the JT-60SA fast-ion loss detector(Elsevier, 2021-06) Cobacho Rodríguez, Carlos; Segado Fernández, Jorge; Hidalgo Salaverri, Javier; Mancini, Alessio; Núñez Portillo, Juan Manuel; García Vallejo, Daniel; García Muñoz, Manuel; Davis, S.; Tomarchio, V.; Hajnal, N.; Piccinni, Carla; Ayllón Guerola, Juan Manuel; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Universidad de Sevilla. Departamento de Ingeniería Aeroespacial y Mecánica de Fluidos; Universidad de Sevilla. Departamento de Ingeniería Mecánica y de Fabricación; Ministerio de Economía y Competitividad (MINECO). España; Ministerio de Economía y Competitividad (MINECO). España; Ministerio de Economía y Competitividad (MINECO). España; European Commission (EC); Universidad de Sevilla. TEP111: Ingeniería Mecánica; Universidad de Sevilla. FQM402: Ciencias y Tecnologías del Plasma y el Espacio; Universidad de Sevilla. TEP-945: Ingeniería AeroespacialA fast-ion loss detector (FILD) is being designed for the JT-60SA tokamak. In this work, the preliminary mechanical design of this diagnostic is described. The expected motion needed to move the probe head between the parking and the measuring positions has been estimated by numerical simulations. A finite element thermal assessment of the detector is presented, to characterize its thermal response during the operation of the machine. Finally, the results of a preliminary electromagnetic analysis are reported to evaluate the impact of major disruptions on the structural components the system. © 2021 The AuthorArtículo On the theory and application of absolute coordinates-based multibody modelling of the rigid–flexible coupled dynamics of a deep-sea ROV-TMS (tether management system) integrated model(Elsevier, 2022-08) Htun, Thant Zin; Suzuki, Hiroyoshi; García Vallejo, Daniel; Universidad de Sevilla. Departamento de Ingeniería Mecánica y de Fabricación; Universidad de Sevilla. TEP111: Ingeniería MecánicaThis paper presents a novel method to investigate the dynamics between the interconnected rigid and very flexible bodies of a deep-sea ROV-TMS with highly coupled dynamics. The aim is to develop an accurate yet effective system model, which is applicable to a wide range of deep-sea working-class ROV applications. The use of different sets of generalized coordinates in rigid–flexible multibody system usually leads to complex forms of constraints Jacobian and quadratic velocity vector when the interconnected rigid and flexible bodies share highly coupled dynamics. Thus, the compatibility of the formulations used in modelling is pivotal to a correct representation of the dynamics of an underwater multibody system with highly coupled dynamics. To this end, a mixed formulation, which is fully-based on absolute coordinates, is presented in modelling the dynamics of underwater tethered vehicle system. The development of system model of a basic ROV-TMS and theoretical implementations are presented in this paper. The applicability of the presented model is assessed through numerical simulations for the realistic scenarios during the deep-sea ROV operations. The numerical studies show that the proposed model is able to capture the nonlinear dynamics of cable and cable drum, and the nonlinear coupling dynamics between the tether cable and the ROV. © 2022 Elsevier LtdArtículo Experimental estimation of the residual fatigue life of in-service wind turbine bolts(Elsevier, 2022-11) Rincón Casado, Alejandro; Juliá Lerma, Javier Miguel; García Vallejo, Daniel; Domínguez Abascal, Jaime; Universidad de Sevilla. Departamento de Ingeniería Mecánica y de Fabricación; Universidad de Sevilla. TEP111: Ingeniería MecánicaThis study presents an experimental methodology aimed at estimating the residual fatigue life of in-service wind turbine bolts. The main objective is to assess the residual life of the bolts to plan their replacement and to avoid unexpected breakages of wind turbine blade connections. To develop the methodology, M16 bolts of quality 10.9 with controlled predamage were used, simulating in-service operating conditions. The fatigue tests were carried out taking care to place the nut at the point on the bolt that produces the highest damage at the same point where the predamage was performed. In addition, the influence of a possible angular positioning error on the residual fatigue life has been investigated. The residual fatigue life is estimated from the difference in fatigue life of new bolt tests and the fatigue life of predamaged bolt tests, simulating service conditions. Special care has been taken to guarantee that the most damaged zone of the bolt in service is also in the position that produces the highest damage during tests. An experimental procedure for determining the fatigue life of a new bolt from tests conducted on a bolt under the same operating conditions was developed. The developed methodology has been applied to M20 bolts belonging to real turbines in service. © 2022 The Author(s)Artículo Formulation of a high-fidelity multibody dynamical model for an electric solar wind sail(Elsevier, 2023-10) Pacheco Ramos, Guillermo; García Vallejo, Daniel; Vázquez Valenzuela, Rafael; Universidad de Sevilla. Departamento de Ingeniería Aeroespacial y Mecánica de Fluidos; Universidad de Sevilla. Departamento de Ingeniería Mecánica y de Fabricación; Ministerio de Ciencia e Innovación (MICIN). España; Universidad de Sevilla. TEP111: Ingeniería Mecánica; Universidad de Sevilla. TEP945: Ingeniería AeroespacialE-sail technology enables a continuous propulsion system based on the repulsive force exerted by solar wind protons on a set of positively charged tethers. Diverse methods have been explored within the last two decades to investigate the dynamics of E-sail. This work introduces a dynamic multibody model combining Absolute Nodal Coordinate Formulation (ANCF) and Natural Coordinates (NC) to describe flexible and rigid bodies, respectively. A complete formulation for cable elements considering nonlinear bending and internal damping is provided. Coulomb propulsive forces are included and the expressions for the integration of the resulting Differential Algebraic Equation (DAE) system are given. Based on the simulation results obtained from the proposed model, the convenience of considering bending stiffness to accurately capture the dynamics is proven. The in-plane and out-of-plane oscillations of the tethers are reported and explained. By means of the Power Spectral Density (PSD) representation, the relevant role on the E-sail dynamics of the spin, bending and axial modes, associated to the well-known problem of a rotating cable with a tip mass, is described. The force and perturbation moments transmitted to the central body are compared to the generated thrust, and its complexity and instability under non-null sailing angle operation is established. © 2023 Elsevier LtdArtículo Synthesis of 1-DOF mechanisms for exact regular polygonal path generation based on non-circular gear transmissions(Elsevier, 2024-08) Castillo, Carlos; López Martínez, Javier; García Vallejo, Daniel; Blanco Claraco, José Luis; Universidad de Sevilla. Departamento de Ingeniería Mecánica y de Fabricación; Universidad de Sevilla. TEP111: Ingeniería MecánicaDesign of one-degree-of-freedom (1-DOF) mechanisms is of paramount interest. This work deals with the generation of exact regular polygonal paths by using two particular 1-DOF mechanisms. The design of two-bar and three-bar mechanisms including non-circular gears is presented and evaluated. Differences in the kinematics of both mechanisms are discussed. The three-bar mechanism allows derivable velocity and acceleration curves during the whole trajectory, including the polygon vertices, a feature that cannot be achieved with the simpler two-bar mechanism. Hence, the three-bar mechanism makes it possible to generate perfect vertices using non-circular gears. To the best of the authors’ knowledge, this mechanism is the first 1-DOF mechanism with articulated links and a non-circular gear transmission that can generate exact regular polygonal paths. The proposed mechanisms can also be applied to generate two straight lines with a given angle, which is another novel contribution of this work. A prototype of the three-bar mechanism has been developed for experimental validation. © 2024 The Author(s)Artículo Dynamic inversion and optimal tracking control on the ball-plate system based on a linearized nonholonomic multibody model(Elsevier, 2024-11) García-Agúndez Blanco, Alfonso; Saccon, A.; García Vallejo, Daniel; Freire Macías, Emilio; Universidad de Sevilla. Departamento de Matemática Aplicada II (ETSI); Universidad de Sevilla. Departamento de Ingeniería Mecánica y de Fabricación; Ministerio de Ciencia, Innovación y Universidades (MICINN). España; Junta de Andalucía; Universidad de Sevilla. TEP111: Ingenieria Mecanica; Universidad de Sevilla. TIC-130: Investigación en Sistemas Dinámicos en IngenieríaThis paper addresses the optimal control of the ball-plate system, a well-known nonholonomic system in the context of nonprehensile manipulation, using a multibody dynamics approach. The trajectory tracking control of a steady-state circular motion of the ball on the plate, for any radius and potentially off-centric with respect to the plate's pivoting point, is achieved by designing a Linear-Quadratic Regulator. A spatial multibody model of the ball-plate system is considered. A key contribution is the analytical computation of the circular steady motion of the ball by dynamic inversion, including the control actions to achieve this reference solution. This enables the analytical computation of the linearized equations along this reference motion, resulting in a periodic linear time-varying (LTV) system, and the application of linear controllability criteria for LTV systems. A controllable linear system, involving the Cartesian coordinates of the contact point and the yaw angle of the sphere, is obtained using a convenient coordinate partition in the linearization. Compared to existing results on the same problem, closed-loop stability about the desired trajectory is achieved for any radius of the circular trajectory. © 2024 The AuthorsArtículo Fatigue life and crack growth direction in 7075-T6 aluminium alloy specimens with a circular hole under biaxial loading(Elsevier, 2019-08) Chaves Repiso, Víctor Manuel; Beretta, Guido; Balbín Molina, José Antonio; Navarro Robles, Alfredo; Universidad de Sevilla. Departamento de Ingeniería Mecánica y de Fabricación; Ministerio de Educación. España; Universidad de Sevilla. TEP111: Ingeniería MecánicaThis work shows the results of a set of tests in 7075-T6 aluminium alloy specimens. The tests were under load control at R = --1. From the tests, the corresponding S-N curves were built, and the endurance limits were calculated for 1 million cycles. The ratio between the pure torsion and tension endurance limits was 0.58, i.e., the behaviour of this material in fatigue is of the von Mises type. Specimens with circular holes of various diameters under tension, torsion and in-phase biaxial loading were tested. The directions of the cracks that grew from the holes were studied with an optical microscope, a scanning electron microscope (SEM) and a non-contact 3D optical profiler. In particular, the points where the cracks began and the direction in which the cracks propagated along the first 150 μm were analysed. In general, the initiation point was close to the maximum principal stress point, and the crack direction was close to the maximum principal stress direction. The endurance limit predictions were close to the experimental resultsArtículo Effect of the notch-component relative size on the notch fatigue limit of AISI 304L specimens under push–pull tests(Sage Publications, 2019-10) Balbín Molina, José Antonio; Chaves Repiso, Víctor Manuel; Navarro Robles, Alfredo; Universidad de Sevilla. Departamento de Ingeniería Mecánica y de Fabricación; Ministerio de Educación. España; Universidad de Sevilla. TEP111: Ingeniería MecánicaResults of a large set of fatigue tests on AISI 304L stainless steel cylindrical round specimens with a circumferential notch of semicircular profile and subjected to uniaxial loading (R = –1) are reported. The outer diameter of the specimens has been kept fixed, whereas the radius of the notch has been increased progressively. A whole range of configurations is studied, from combinations of notch radius and specimen diameter where the remaining ligament is much larger than the notch (semi-infinite problem) to configurations where the ligament is much smaller than the notch (finite problem) and where interaction effects have a noticeable influence on the shape of the stress gradient. An S–N curve has been obtained for each configuration. The experimentally obtained fatigue limits for the different notch radii have been compared with predictions made with several methods. However, a strong divergence between the experimental values and the theoretical predictions, which were extremely conservative, has been found and this has been attributed to work-hardening and residual stress effects connected with the machining process. It has also been suggested that a geometrical notch strengthening effect, possibly connected with stress triaxiality due to the notch, and the accompanying hydrostatic tensile stress, may also be a contributing factor. A simple practical engineering method to account for these effects has been proposed.