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Lanzi L.,IChrome Ltd | Airoldi A.,Polytechnic of Milan | Cacchione B.,Polytechnic of Milan | Astori P.,Polytechnic of Milan
Structural and Multidisciplinary Optimization | Year: 2012

The paper proposes a novel approach to identify the feasible region for a constrained optimisation problem. In engineering applications the search for the feasible region turns out to be extremely useful in the understanding of the problem as the feasible region defines the portion of the domain where design parameters can be ranged to fulfil the constraints imposed on performances, manufacturing and regulations. The search for the feasible region is not a trivial task as non-convex, irregular and disjointed shapes can be found. The algorithm presented in this paper moves from the above considerations and proposes a recursive feasible-infeasible segment bisection algorithm combined with Support Vector Machine (SVM) techniques to reduce the overall computational effort. The method is discussed and then illustrated by means of three simple analytical test cases in the first part of the paper. A real-world application is finally presented: the search for the survivability zone of a crashworthy helicopter seat under different crash conditions. A finite element model, including an anthropomorphic dummy, is adopted to simulate impacts that are characterised by different deceleration pulses and the proposed algorithm is used to investigate the influence of pulse shape on impact survivability. © 2012 Springer-Verlag.

Quaranta G.,Polytechnic of Milan | Lanzi L.,iChrome Ltd. | Sima M.,iChrome Ltd.
37th European Rotorcraft Forum 2011, ERF 2011 | Year: 2011

The paper presents a novel free mesh morphing technology based on Moving Least Square (MLS) applied to Structural Optimisation. The proposed approach moves from the field of surface reconstruction from 3D scattered data. From a more general standpoint, MLS methods seem promising methodologies to solve different morphing problems where existing meshes can be modified without specific needs to change their topology, i.e. their connectivity information. In this respect, MLS is a very effective and promising methodology for mesh morphing. The proposed MLS morphing methodology has been applied to the optimisation of composite stiffened panels. The goal of the optimisation is to reduce the overall panel weight finding the best layups (thickness and percentages) for skin and stringers as well as the optimal shape for the stringers via MLS morphing, considering stability and strength constraints. The optimisation process acts on the shape of the stringers, via the proposed MLS approach, without requiring any remeshing towards the optimisation process. Nonlinear Finite Element analyses are used to predict the overall behaviour of the panels in terms of force vs. shortening curve up to final failure, discriminate between local skin instabilities and global ones, eventually leading to the overall failure of the structure. Strength criteria are additionally accounted by monitoring the maximum Tsai-Wu failure index overall the structure.

Airoldi A.,Polytechnic of Milan | Bertoli S.,Polytechnic of Milan | Lanzi L.,IChrome Ltd. | Sirna M.,IChrome Ltd. | Sala G.,Polytechnic of Milan
Applied Composite Materials | Year: 2012

A study for the replacement of a metallic swing-arm of a high performance motorcycle with a composite part is presented. Considering the high structural effectiveness of the original metallic component, the case study evaluates the potential of composites in a challenging application. The FE model of the original component is developed to evaluate the structural performance in the most significant load conditions. A manufacturing process, based on a RTM technique, is proposed and analysed in order to develop realistic design hypotheses. The design approach is based on an optimisation process with 60 design variables. A constrained multi-objective genetic algorithm is applied to identify the solutions representing the best trade-off between mass reduction and improvement of torsional stiffness. Results show that composite materials can enhance the structural efficiency of the original metallic part, even considering technological limitations and damage tolerance requirements. © Springer Science+Business Media B.V. 2011.

Airoldi A.,Polytechnic of Milan | Di Landro L.,Polytechnic of Milan | Sirna M.,Ichrome Ltd | Iavarone P.,Polytechnic of Milan | Sala G.,Polytechnic of Milan
Journal of Materials Science | Year: 2013

The article describes the development of a numerical material model of ceramic matrix composite (CMC) reinforced by bundles of thousands of short carbon fibres and produced by means of a liquid silicon infiltration process. The objective of the article is the development of a numerical mesoscale model that considers the material as a simple bi-phasic composite constituted by an isotropic matrix with differently sized inclusions. The distinctive material microstructure that complicates the development of such a model is presented and the issues represented by the generation of the finite element models and by the identification of the effective properties of the constituent phases are discussed. In the presented approach, models are generated by numerically simulating the packing of bundles and phases are identified by means of tests and numerical analyses, which are performed on long fibre-reinforced specimens and on specimens subjected to a thermal process for the elimination of carbon reinforcement. The approach is applied to find out the parameters of a homogenized orthotropic model for CMC plates. The obtained results show that the numerical packing simulations can generate models with a realistic distribution of size, shape and orientation of the bundles. The mesoscale model and the phase properties identified by the proposed numerical and experimental procedure are validated by considering the stiffness of standard CMC specimens obtained in three-point bending tests. According to the results, the developed methodologies can be considered as a promising approach for a reliable prediction of short fibre-reinforced CMC elastic properties. © 2012 Springer Science+Business Media New York.

Chiarelli M.R.,University of Pisa | Binante V.,University of Pisa | Botturi S.,University of Pisa | Massai A.,University of Pisa | And 3 more authors.
Aircraft Engineering and Aerospace Technology | Year: 2016

Purpose: The purpose of this study concerns numerical studies and experimental validation of the mechanical behavior of hybrid specimens. These kinds of composite specimens are made up of thin carbon and glass substrates on which some Macro Fiber Composite® (MFC) piezoelectric patches are glued. A proper design and manufacturing of the hybrid specimens as well as testing activities have been performed. The research activity has been carried out under the FutureWings project, funded by the European Commission within the 7th Framework. Design/methodology/approach: The paper describes the basic assumptions made to define specimen geometries and to carry out experimental tests. Finite element (FE) results and experimental data (laser technique measurements) have been compared: it shows very good agreement for the displacements' distribution along the specimens. Findings: Within the objectives of the project, the study of passive and active deformation characteristics of the hybrid composite material has provided reference technical data and has allowed for the correct adaptation of the FE models. More in particular, using the hybrid specimens, both the bending deformations and the torsion deformations have been studied. Practical implications: The deformation capability of the hybrid specimens will be used in the development of prototypical three-dimensional structures, that, through the electrical control of the MFC patches, will be able to change the curvature of their cross section or will be able to change the angle of torsion along their longitudinal axis. Originality/value: The design of nonstandard specimens and the tests executed represent a novelty in the field of structures using piezoelectric actuators. The numerical and experimental data of the present research constitute a small step forward in the field of smart materials technology. © Mario Chiarelli, Vincenczo Binante, Stefano Botturi, Andrea Massai, Jan Kunzmann, Angelo Colbertaldo, Diego Romano.

Agency: European Commission | Branch: FP7 | Program: CP-FP | Phase: AAT.2012.6.3-1. | Award Amount: 816.80K | Year: 2013

The project moves starting from a very simple concept: let us think of an airplane as a great body with its end structures that could have the possibility to change their shape as they had internal nerve endings and muscles. The aerodynamic shape of aircraft lifting surfaces must change during the flight, owing to the aerodynamic requirements of the different maneuvers (ascent and descent operations, yaw). Mobile surfaces are introduced in conventional wings to this purpose (ailerons, flaps, slats etc.), introducing at the same time inevitably additional weight, mechanisms, sources of vibrations and other well known limits. An interesting alternative to mobile surfaces could be represented by self shaping wings, i.e. wings the surface of which can be elastically deformed through its entire length, and managed in order to obtain the required lifting profile. Such wing performances could be obtained through the application of composite hybrid materials where layers of new generation of piezoelectric fibers are drowned, and trigged by relatively low voltage. Target of the research is the deep understanding of the technical feasibility and of the limits of such an application. Depending on the results, self shaping wings (or Future Wings) could be more deeply investigated and designed in order to replace ailerons, slats, tail wings, rudders and, probably, even flaps: the relevant technology could have really wide fields of applications (helicopter rotor blades, satellite panels, etc.). Project objectives will be pursued developing at first theoretical models and computational new generation algorithms aimed at designing, optimizing and afterwards manufacturing a scaled model of Future Wing on which experimental tests will be carried out in order to understand the viability of the original idea, which has the potential to bring a radical new approach to the design of flying vehicles lifting surfaces configuration.

Agency: GTR | Branch: Innovate UK | Program: | Phase: Smart - Development of Prototype | Award Amount: 126.00K | Year: 2013

The goal of the project is to develop a prototype for an advanced 3D mesh morphing tool—named Shaper—for computer-aided engineering (CAE) applications. Shaper will allow the user to efficiently re-shape and re-size three-dimensional computer models used for structural and fluid-dynamics simulations, which are extensively used during the design phase of new products in the aerospace, automotive and renewable energy industry. Shaper will provide a novel approach to mesh morphing by combining classic morphing techniques with innovative algorithms recently developed in the computer graphics field, thus resulting in a more powerful tool than similar products already available in the market. A key aspect of Shaper will be its open architecture: the implemented mesh morphing techniques are completely independent from the underlying computer model used and hence the product will be able to support any of the structural and computational fluid-dynamics softwares available on the market. In fact, through the use of public application programming interfaces, end users can easily integrate the software into their existing engineering design procedure, which, in turn, will result in a significant reduction of the development time of a new product and hence of project costs. This is extremely beneficial to the design cycle of a new product, especially when the complexity of the project requires a computationally intensive, time-consuming, iterative optimisation of the initial design.

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