Journal: Meccanica

Abbreviation

Meccanica

Publisher

Springer

Journal Volumes

ISSN

1572-9648
0025-6455

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2018 - 201922020 - 20255
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Publications 1 - 7 of 7
  • Thermomechanical analysis and additive manufacturing of a target for nuclear physics
    Item type: Journal Article
    Benmansour, Hicham; Cavoto, Gianluca; Chiarello, Gianluigi; et al. (2025)
    Meccanica
    In nuclear physics experiments, a typical engineering issue is the dissipation of heat from very small surfaces and volumes on which a significant amount of energy is thermally deposited by a small-sized beam of particles. This article describes a finite element method simulation methodology for heat dissipation and the subsequent design and development of the holder of a lithium-based target up to its construction. The target described in the paper is used to study the ⁷Li(p,e⁺e⁻)⁸ Be process with the proton Cockcroft–Walton accelerator of the MEG experiment at the Paul Scherrer Institut (Villigen, Switzerland). The material of the target region crossed by the emitted e⁺e⁻ has to be reduced as much as possible to minimally perturb the measurement of their momenta, and a thin target is required. In order to ensure the dissipation of the thermal load on the target, an in-depth thermomechanical and structural simulation was realized using ANSYS. This allowed to verify the efficiency of the dissipation mechanisms, the maximum temperatures reached, and the thermal stress on all parts to ensure a sufficiently long lifetime of the target for the physics process measurement. To realize an optimized geometry ensuring continuity of the thermal flux—essential to dissipate the incoming power—the additive manufacturing was deemed necessary. The target support has been realized in pure copper, exploiting its excellent conductive properties and the cutting-edge additive manufacturing technologies, recently developed to overcome the inherent difficulties of Laser Powder Bed Fusion (L-PBF) technology to this material.
  • Well-conditioned AI-assisted sub-matrix selection for numerically stable constrained form-finding of reticulated shells using geometric deep Q-learning
    Item type: Journal Article
    Tam, Kam-Ming Mark; Maia Avelino, Ricardo; Kudenko, Daniel; et al. (2025)
    Meccanica
    The selection of well-conditioned sub-matrices is a critical concern in problems across multiple disciplines, particularly those demanding robust numerical stability. This research introduces an innovative, AI-assisted approach to sub-matrix selection, aimed at enhancing the form-finding of reticulated shell structures under the xy-constrained Force Density Method (also known as Thrust Network Analysis), using independent edge sets. The goal is to select a well-conditioned sub-matrix within a larger matrix with an inherent graph interpretation where each column represents an edge in the corresponding graph. The selection of ill-conditioned edges poses a significant challenge because it can render large segments of the parameter space numerically unstable, leading to numerical sensitivities that may impede design exploration and optimisation. By improving the selection of edges, the research assists in computing a pseudo-inverse for a critical sub-problem in structural form-finding, thereby enhancing numerical stability. Central to the selection strategy is a novel combination of deep reinforcement learning based on Deep Q-Networks and geometric deep learning based on CW Network. The proposed framework, which generalises across a trans-topological design space encompassing patterns of varying sizes and connectivity, offers a robust strategy that effectively identifies better-conditioned independent edges leading to improved optimisation routines with the potential to be extended for sub-matrix selection problems with graph interpretations in other domains.
  • A variational phase-field model for ductile fracture depending on hydrostatic stresses
    Item type: Journal Article
    Sur, Anne-Sophie; De Lorenzis, Laura; Maurini, Corrado; et al. (2025)
    Meccanica
    We model ductile fracture for geometrically linear deformations by coupling plasticity and phase-field fracture models in a variationally consistent framework. The main aim of the proposed model is to account for the effect of stress triaxiality, in order to accurately reproduce ductile fracture, in particular, the instant and location of fracture initiation. For this purpose, we couple the modified Cam-Clay plasticity model with a phase-field fracture model. We study the behaviour of the model analytically in terms of homogeneous material responses, and numerically on plane-strain and axisymmetric specimens under tension with different notches.
  • Robotically controlled scale-model testing of masonry vault collapse
    Item type: Journal Article
    Calvo Barentin, Cristián; Van Mele, Tom; Block, Philippe (2018)
    Meccanica
    Scale-model testing can be used to understand the equilibrium and validate the computational modelling of discrete-element assemblies subjected to external loads or support displacements. This paper proposes a novel approach to investigate the collapse of discrete-element assemblies using 3D-printed scale models manipulated with force-sensitive robotic arms combined with an optical measuring system. To demonstrate that this provides a more flexible and comprehensive solution for the assessment of the structural behaviour of unreinforced masonry structures, the same setup is used to conduct different types of experiments on a 3D-printed model of a cross vault. First, the robotic arms are used to apply a point load in different locations while measuring the resistance of the vault until collapse. In a second experiment, the robotic arms are used to simulate the effect of progressive differential settlement of the supports of the vault. The trajectory along which the displacement of the support is applied is based on real-time measurements by the force-sensitive robots of the occurring outward thrust.
  • Hybrid vibration absorber for self-induced vibration suppression: exact analytical formulation for acceleration feedback control
    Item type: Journal Article
    Bartos, Marcell; Habib, Giuseppe (2023)
    Meccanica
    Hybrid vibration absorbers (HVAs) are an effective solution for vibration mitigation. They combine the passive vibration absorption mechanism of tuned mass dampers (TMDs) with feedback-controlled actuators, similar to active mass dampers. This enables them to overcome the performance of both systems in terms of vibration mitigation effectiveness and energy consumption, respectively. This study evaluates the vibration suppression capabilities of an HVA against self-excited oscillations. A single-degree-of-freedom host system encompassing a negative damping term is considered. First, the possibility of enhancing the stability properties of an optimally tuned TMD through a feedback controller is evaluated. The analysis shows that this approach cannot improve the absorber’s performance. Subsequently, simultaneous optimization of all the HVA parameters is considered. Our results reveal that this approach significantly enhances the system’s performance. All analysis is carried out analytically without resorting to approximations. Finally, the absorber is numerically applied to suppress friction-induced vibrations and galloping instabilities.
  • Load-path optimisation of funicular networks
    Item type: Journal Article
    Liew, Andrew; Pagonakis D.; Van Mele, Tom; et al. (2018)
    Meccanica
    This paper describes the use of load-path optimisation for discrete, doubly curved, compression-only structures, represented by thrust networks. The load-path of a thrust network is defined as the sum of the internal forces in the edges multiplied by their lengths. The presented approach allows for the finding of the funicular solution for a network layout defined in plan, that has the lowest volume for the given boundary conditions. The compression-only thrust networks are constructed with Thrust Network Analysis by assigning force densities to the network’s independent edges. By defining a load-path function and deriving its associated gradient and Hessian functions, optimisation routines were used to find the optimum independent force densities that minimised the load-path function subject to compression-only constraints. A selection of example cases showed a dependence of the optimum load-path and force distribution on the network topology. Appropriate selection of the network pattern encouraged the flow of compression forces by avoiding long network edges with high force densities. A general, non-orthogonal network example showed that structures of high network indeterminacy can be investigated both directly for weight minimisation, and for the understanding of efficient thrust network patterns within the structure.
  • Densely packed membrane configurations
    Item type: Journal Article
    Heyden, Stefanie; Ortiz, Michael (2025)
    Meccanica ~ ICTAM-100
    We put forth a simple mathematical model of densely packed fluid membranes and solve for packing configurations that minimize their elastic energy. Numerical calculations are facilitated via a finite-difference discretization scheme. Absent topological constraints, energy-minimizing configurations are found to closely follow solutions of the eikonal equation. These typically involve foliations comprising many closed surfaces. We show how allowing for cuts and creases, with an additional minimization over the total crease energy, generates configurations consisting of a densely packed single sheet.
Publications 1 - 7 of 7