Tesi di Dottorato

Permanent URI for this communityhttps://lisa.unical.it/handle/10955/10

Policy e regolamenti

Browse

Subject: search.filters.subject.FEM

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Development of a CAE-basedapproach for the concurrent design, manufacturing and testing of hybrid metal-composite spur gears
    (Università della Calabria, 2020-02-19) Catera, Piervincenzo Giovanni; Furgiuele, Franco; Mundo, Domenico; Treviso, Alessandra
    Trends in emission limitations and fuel efficiency impose a more efficient energy exploitation in many application fields of mechanical systems. In this direction, the lightweighting of mechanical structures represents a powerful strategy, above all in the transportation industry, where geared transmissions play a key role. Here, these components are designed in such a way that performance criteria are met at the minimum weight, without compromising the requirements of reliability and safety. In this context, the aim of the present work is the development of new strategies for the design of geared systems, where the concept of gear body lightweighting with geometrical modifications is substituted by the one applied to the material, in order to improve the strength-to-weight ratio and reduce vibrations in the overall mechanical system. In particular, the research is focused on innovative methods for the simulation, manufacturing and testing of a hybrid gear, in which a metal rim is joined with a composite body. In detail, the contribution of the gear body stiffness is studied by means of a multi-scale approach, which starts from the interaction between matrix and fibres at the micro-scale to derive the lamina properties at the macro-scale. In this way, the anisotropy of the composite material can be accounted for, leading to an accurate modelling and evaluation of the mechanical properties of the gear. Additionally, two assembly techniques are used for joining the rim part to the body, which include adhesive bonding and interference fitting. Both techniques are analysed with experimental modal tests to characterize dynamic stiffness and damping in comparison to a lightweight metal gear with the same mass. At the same time, non-linear finite element (FE) simulations are executed for the evaluation of the static transmission error and meshing stiffness. Finally, the last part of the work deals with the experimental analysis of a hybrid gear pair during meshing in a dedicated test-rig, where the dynamic behaviour is analysed with respect to the variation of applied torque and rotational velocity. Noise and vibration behaviour of a solid-hybrid gear pair is compared to that of a pair composed by a solid and a lightweight metal gear. Experimental results show the great potentiality of the multi-material approach in mechanical power transmissions.
  • Thumbnail Image
    Item
    Toughening mechanisms and damage tolerance of bioinspired interfaces
    (Università della Calabria, 2020-03-06) Morano, Chiara; Furgiuele, Franco; Alfano, Marco
    Biologically inspired designs were deployed into selective laser sintering of polyamide substrates to study the mechanics of adhesion and debonding of adhesive bonded structural interfaces. In particular, through extensive series of experiments and simulations, the present study covers the effect of hollow channels, mimicking the base plate of the Amphibalanus amphitrite, and of sinusoidal interfaces, resembling those observed in sutures joints, on the mechanics of crack propagation in adhesive bonds. A model material system comprising adhesively bonded 3D printed substrates in the Double Cantilever Beam (DCB) configuration was selected for the analyses. Adhesive bonding and subsequent mechanical tests revealed the occurrence of a crack trapping effect, which hinders crack propagation and enhances energy dissipation with respect to the baseline interface. The use of bioinspired structures is shown to improve the performances of adhesive joints, enabling damage tolerance and, in the case of subsurface channels, also a weight reduction. Numerical simulations, carried out using finite element analysis (FEA) with interface elements, were also executed to gain a deep understanding of all mechanisms observed experimentally. The simulations were able to mimic the serrated behavior observed in experimental load-displacement responses, which was due to the snap-through interfacial cracking mechanism, i.e., a sudden and almost instantaneous growth of apparently stable cracks. Moreover, the mechanisms of fracture observed in the experiments (e.g., nucleation of a secondary crack at the interface) were reproduced with good accuracy in finite element simulations. The overall analysis demonstrates that is possible to improve joints effective fracture toughness by modifying joints architecture, even without any modification of adhesive type and/or interface properties (e.g., surface energy). This study further confirms that additive manufacturing represents a powerful platform for the experimental study of bio-inspired materials