A tool in support of oral implantology

Il brevetto si riferisce ad un dispositivo che trova applicazione nella tecnica “flap-less” in chirurgia impiantare (inserimento di impianti senza esecuzione di lembo chirurgico), tecnica meno invasiva e traumatica per il paziente; esso consente di: - eseguire in modo diretto e preciso la rilevazione del profilo osseo esterno del sito impiantare - determinare l’angolazione ottimale dell’asse di foratura - guidare l’operazione di fresatura secondo l’asse prescelto Il dispositivo, grazie alla sua adattabilità e modularità è utilizzabile per eseguire siti implantari sia singoli che multipli ed è adattabile a tutte le variabili anatomiche che si possono presentare, è inoltre sterilizzabile e qu…

Simulation of the Behaviour of a New Semitrailer with Structural Load-Carrying Platform in Composite Material

Design of a new tibial intramedullary nail

Approccio Metodico alla Riprogettazione di un Semirimorchio

Economic competition leads to continuous development of new products and processes, but it is opposed by the decrease of speed of characteristics improvement and by the consequent tendency of the market to saturation. Redesign assumes in this context a particular remark because it cans allowing the acceleration of process of performances increase. This objective needs a methodical and structured approach that can leading, even, to the modification of product concept. In this work it has been studied the possibility of reducing the mass of a road semitrailer, by intervening on its structural elements. Some solutions, characterized by new topology and/or materials, have been examined and a st…

Topology Optimization Design of Internal Reinforcements in a Sailing Dinghy

AbstractIn this paper, a novel approach has been followed based on FEM simulation and Topology Optimization tools to locate and model the reinforcements inside the hull of a sailing dinghy. This process assumes that the inner volume included between the hull and the deck is, at the beginning of the simulation, filled with material; then a portion of this inner volume is eroded until a final free form shape of the reinforcements is obtained. A key point of this procedure is the definition of the optimization constrains because the final shape of the reinforcements must fulfill several requirements such as weight, stiffness and stress. At the end of the optimization procedure, the final shape…

Influence of the evolutionary optimization parameters on the optimal topology

Topological optimization can be considered as one of the most general types of structural optimization. Between all known topological optimization techniques, the Evolutionary Structural Optimization represents one of the most efficient and easy to implement approaches. Evolutionary topological optimization is based on a heuristic general principle which states that, by gradually removing portions of inefficient material from an assigned domain, the resulting structure will evolve towards an optimal configuration. Usually, the initial continuum domain is divided into finite elements that may or may not be removed according to the chosen efficiency criteria and other parameters like the spee…

Advanced Techniques for Design and Manufacturing in Marine Engineering

Modern engineering design processes are driven by the extensive use of numerical simulations, and naval architecture as well as ocean engineering are no exception. Structural design or fluid dynamic performance evaluation can only be carried out by means of several dedicated pieces of software. Classical naval design methodology can take advantage of the integration of these pieces of software, giving rise to more robust design in terms of shape, structural and hydrodynamic performances, and manufacturing processes. This Special Issue (SI) on “Advanced Techniques for Design and Manufacturing in Marine Engineering”, published in the Journal of Marine Science and Engineering, aimed to invite …

Lay-up optimization for the hull of a racing sailing yacht

Abstract Deformability and buckling load of yacht hulls with fiber reinforced plastic sandwich structure depend on the stack sequence of the skins. In this work an optimization of fiber directions of the laminae for a racing yacht is proposed. This procedure has been divided into three parts (i.e. material characterization, surface model definition, lay-up optimization). First of all a set of unidirectional specimens has been realized, by using the same fibers and matrix (carbon/epoxy) used for the hull as well as the same procedure and workers, in order to characterize the material according to American Society for Testing and Materials (ASTM) Standard D3039, employing strain gage techniqu…

Improving the Downwind Sail Design Process by Means of a Novel FSI Approach

The process of designing a sail can be a challenging task because of the difficulties in predicting the real aerodynamic performance. This is especially true in the case of downwind sails, where the evaluation of the real shapes and aerodynamic forces can be very complex because of turbulent and detached flows and the high-deformable behavior of structures. Of course, numerical methods are very useful and reliable tools to investigate sail performances, and their use, also as a result of the exponential growth of computational resources at a very low cost, is spreading more and more, even in not highly competitive fields. This paper presents a new methodology to support sail designers in ev…

A SIMULTANEOUS ENGINEERING APPROACH TO THE YACHT DESIGN

The authors describe the approach applied to the design and manufacturing of a 15” dinghy which will challenge other similar sailing boats in fleet regattas. The Simultaneous Engineering approach appears to be the most powerful instrument since it permits to keep under control many variables simultaneously and then to reduce the Time To Market. Starting from regatta rules and limitations, the hull shape has been chosen and then modelled with a parametric CAD software. Such a model has been managed in order to be suitable for both FEM (Finite Element Method) and CFD (Computational Fluid Dynamics) analyses.

A New Systematic Series of Foil Sections with Parallel Sides

Parallel-sided foil sections are used for centerboards and rudders in sailing dinghy classes and also for struts placed in a fluid flow. The objective of this work is to create a systematic series of parallel-sided sections to be used under different conditions, with an emphasis on the sailing dinghies 470, 420 and Optimist. The loss, and surprisingly the gain, in performance relative to 4-digit NACA sections are also investigated. A 2D Reynolds-averaged Navier&ndash

Analisi di un timone navale

Thermo-Mechanical Behaviour of Flax-Fibre Reinforced Epoxy Laminates for Industrial Applications

The present work describes the experimental mechanical characterisation of a natural flax fibre reinforced epoxy polymer composite. A commercial plain woven quasi-unidirectional flax fabric with spun-twisted yarns is employed in particular, as well as unidirectional composite panels manufactured with three techniques: hand-lay-up, vacuum bagging and resin infusion. The stiffness and strength behaviours are investigated under both monotonic and low-cycle fatigue loadings. The analysed material has, in particular, shown a typical bilinear behaviour under pure traction, with a knee yield point occurring at a rather low stress value, after which the material tensile stiffness is significantly r…

Curve and Surface Fitting via Optimisation Technique

Mechanical Behaviour of a Green Sandwich Made of Flax Reinforced Polymer Facings and Cork Core

Abstract This work investigates the flexural behavior of a composite sandwich made of flax fibers reinforced skin facings and an agglomerated cork core, to be employed as an eco-friendly solution for the making of structural components of small sailing boats. An experimental mechanical characterization of the strength and stiffness flexural behavior of the proposed sandwich is carried out, providing a comparison of performances from three implemented assembling techniques: hand-lay-up, vacuum bagging and resin infusion. Sandwich beams have been tested under three point bending (TPB) at various span lengths. A procedure is also proposed and implemented to consider the potential influence of …

Sailing dinghy hydrodynamic resistance by experimental and numerical assessments

Abstract Hull forms of high-performance sailing dinghies are very interesting for yacht designers. After a long period in which the attention has been focused on one-design boats, in recent years a few exciting restricted classes such as International Moth, International 14′, 18’ Skiff and Class A catamaran become recognized in several countries and led to interesting advances in high-performance yacht design. “1001VELAcup R3” class is two people racing dinghy designed according to a box rule with limitation on LOA and Bmax and total sail area. The boats must be designed and built by students of European Universities and race yearly in Italy. This paper focuses on two best-ranked boats “LED…

A new user interface for human-computer interaction in virtual reality environments

This paper concerns the result of a research activity about the problems related to the human-computer interaction (both hardware and software) in virtual reality systems. In particular, a virtual reality application package, called VIRDE and used for the design review in immersive environment, has been used as a case study. After a detailed analysis of the hardware and software systems, and the examination of the main functional requirements, a new user interface has been developed. This new interface being composed of two input devices (tracked by an optical system) permits the two-hands interaction, instead of the most commonly single-hand interaction. The measurement of the software usa…

A tool for the interactive mesh refinement in virtual environments

Simulation of a Milling Process with Virtual Reality

Numerical study of the components positioning influence on the stability of a reverse shoulder prosthesis

Aim of this paper is to setup a novel procedure able to analyze performances of a reverse shoulder prosthesis when different geometrical configurations are assumed. Nowadays, such a prosthesis is widely used but, because of its novelty, data in literature give poor information about performances and limits to its applicability. The activity has been divided into the following steps. At the beginning the shape of the prosthesis has been digitally acquired via a 3D scanner. Then, CAD models of all prosthetic components have been geometrically optimized in a way to obtain final entities suitable for numerical simulations. After that, CAD assemblies have been created between prosthetic componen…

Strain Measurement on Composites: Errors due to Rosette Misalignment

Electrical resistance strain gauges are increasingly used for the determination of the strain field in composite components. The effect of the angular misalignment of a strain gauge rosette on the determination of the strains in a composite material is investigated in this paper. The theoretical analysis shows that the strain error along the principal material directions depends on the difference of principal strains, on the angular misalignment of the rosette and on the angle between the maximum principal strain and the fibre direction. The paper also shows experimental evidence for the theoretical analysis.

Numerical methods in the design process of a sailing yacht

A genetic algorithm for combined topology and shape optimisations

A method to find optimal topology and shape of structures is presented. With the first the optimal distribution of an assigned mass is found using an approach based on homogenisation theory, that seeks in which elements of a meshed domain it is present mass; with the second the discontinuous boundaries are smoothed. The problem of the optimal topology search has an ON/OFF nature and has suggested the employment of genetic algorithms. Thus in this paper a genetic algorithm has been developed, which uses as design variables, in the topology optimisation, the relative densities (with respect to effective material density) 0 or 1 of each element of the structure and, in the shape one, the coord…

Virtual prototyping of a new intramedullary nail for tibial fractures

In this work a new distal interlocking system has been developed which is easy to use, allows a reduction of the operating time and consequently the exposure to radiations both for surgeon and patient. The main goal of this study has been the design of a new intramedullary nail for tibial fractures able to simplify and speed up the distal locking operation phases. After a preliminary stage during which several candidate concepts have been proposed and analysed, the best solution has been developed and deeply investigated. The new system, called “expansion nail”, has been firstly modelled by setting up a full parametric CAD model and, then, tested by running non linear FEM analyses to evalua…

L’implementazione del processo di redesign

Methodical redesign of a semitrailer

A new design approach to the use of composite materials for heavy transport vehicles

In order to keep or to reach a high level of competitiveness and performance of a product, it is necessary to explore all the possible solutions that allow the best compromise between costs and project requirements. By this point of view the study of alternative designs and/or materials to use, is an important aspect that can identify a new concept or way of thinking about a product. This paper presents how to make use of composite materials in the field of heavy vehicles transportation. A new semitrailer in composite material has been designed, using a methodical redesign approach and an optimisation process. The main innovation in this project is, besides the use of the Glass Fibre Reinfo…

New algorithms to evaluate the real shape of a hull

In this study, a new method to compare rebuilt surfaces of hulls of sailing yachts is presented. In particular, the considered rebuilt surfaces are created through classic reverse engineering approaches. The new method has been developed by means of Grasshopper, a free generative algorithms editor that can be used as plugin of Rhinoceros, one of the most widespread free-form modelling software. In particular, two different algorithms have been developed: the first one allows controlling the quality of the rebuilt surfaces, the second one, instead, allows to measure the deviations between the original CAD Model and the rebuilt surface of the hull. A case study related to the hull of a small …

THE TOPOLOGY OPTIMIZATION IN THE PRODUCT DESIGN PROCESS

The design process represents, already for a long time now, a very interesting research field for the scientific community that has tried, through its own activity of research and development, to make it faster, more reliable and efficient. Thanks to this continuous development, during the last years, the product design process has suffered a remarkable improvement, both regarding the methodological aspect, become mostly structured, objective and rational, and as regards the helping tools for the design like, for example, the software CAD, FEM, CFD, that have been improved in their efficiency and functionality. In this context, the development of more and more reliable and simple to use met…

A reverse engineering approach to measure the deformations of a sailing yacht

In this work, a multidisciplinary experience, aimed to study the permanent deformations of the hull of a regatta sailing yacht is described. In particular, a procedure to compare two different surfaces of the hull of a small sailing yacht, designed and manufactured at the University of Palermo, has been developed. The first one represents the original CAD model while the second one has been obtained by means of a reverse engineering approach. The reverse engineering process was performed through an automatic close-range photogrammetry survey, that has allowed to obtain very accurate measures of the hull, and a 3D modelling step by the well-known 3D computer graphics software Rhinoceros. The…

Refitting of an eco-friendly sailing yacht: numerical prediction and experimental validation

A 4.60 m sailing yacht, made with a flax fiber composite and wood, has been refitted with the aim of hull weight reduction and performance improvement during regattas. The first objective was obtained with a lightening of internal hull reinforcements while the second one with a reduction of the maximum beam, in order to minimize the longitudinal moment of inertia. The refitting was first simulated via CAD-FEM interaction to establish the feasibility of the procedure and to verify the structural integrity. The resulting hull was then instrumented with strain gauges and tested under typical rigging and sailing conditions. Results obtained by the numerical modeling and measured from experiment…

Un nuovo strumento per lo studio dei risultati di analisi FEM

Ottimizzazione di Forma della Deriva di una Barca a Vela: applicazione al caso della classe 5o5

Con questo lavoro gli autori propongono un metodo di indagine automatizzato per la ricerca della forma ottimale di una deriva di uno scafo a vela che garantisca la portanza necessaria, nelle ordinarie condizioni di navigazione controvento, offrendo al contempo la minore resistenza. L’ampio spettro di forme adottate denuncia forse il problema dei progettisti, i quali si rifanno alla teoria classica dell’aerodinamica, nell’interpretare il complesso problema idrodinamico. Da questo punto di vista un valido aiuto viene offerto dai codici di fluidodinamica computazionale (CFD) i quali permettono, con buona approssimazione, di individuare la distribuzione delle forze e delle velocità di un flusso…

A Numerical Approach to the Keel Design of a Sailing Yacht

This paper describes an approach to the keel design of a sailing yacht. The related software, which is fully automatic, permits to obtain an optimal shape by modifying the surface used to define the keel planform. B-spline curves and surfaces have been used because of their ability in following complex shapes. The algorithm integrates ad hoc implemented original software with Computational Fluid Dynamics (CFD) commercial ones. The optimisation procedure makes use of Genetic Algorithms (GAs) and a gradient – based optimiser for the refinement of the solution. A careful CAD and CFD modelling leads to a stable and efficient generalised method, which has been applied to the design of the centre…

OTTIMIZZAZIONE DI FORMA ATTRAVERSO ANALISI CFD DI UN CATAMARANO CON SCAFI ASIMMETRICI PER USO AD ALTA VELOCITÀ

Strumento di supporto all’implantologia orale.

Il brevetto si riferisce ad un dispositivo che trova applicazione nella tecnica "flap-less" in chirurgia implantare (inserimento di impianti senza esecuzione di lembo chirurgico), tecnica meno invasiva e traumatica per il paziente; esso consente di: - eseguire in modo diretto e preciso la rilevazione del profilo osseo esterno del sito implantare - determinare l'angolazione ottimale dell'asse di foratura - guidare l'operazione di fresatura secondo l'asse prescelto. Il dispositivo, grazie alla sua adattabilita' e modularita'. E' utilizzabile per eseguire siti implantari sia singoli che multipli ed è adattabile a tutte le variabili anatomiche che si possono presentare, è inoltre sterilizzabile…

Catamarano a scafi asimmetrici ad alta efficienza idrodinamica

Topological optimization of a structural naval component manufactured in FDM

In this paper, a topological optimization procedure has been applied on a real component of the deck of a sailing multi-hull in order to find the internal shape that best save the material used in the manufacturing process without a relevant loss of structural rigidity. The multi-hull boat is a 16 feet length catamaran equipped with an asymmetric foil on both centerboards and with a symmetric foil on both rudders. The task of the analyzed object is to act as a cylindrical support for the screw that drives the rotation of the centerboard. The process adopted to manufacture this object is the Fused Deposition Modeling (FDM) technique, because of its high versatility and its relative low-cost …

Progettazione di un chiodo endomidollare tibiale

Yacht performance monitoring in real sailing conditions

Abstract In this paper a multi-method approach is used to setup and validate a monitoring system applied to a small sailing boat during real sailing conditions. This monitoring system is able to transform the data coming from some typical devices installed on board into information about the deformed state of the boat. GPS, Wind Data Logger and cameras have been installed on the boat to measure its route and speed, the apparent wind velocity and direction and the positions of the crew members. These data are processed to determine the equilibrium of the boat and estimate the loads applied on it. Then, a CAD/FEM model calculates the effects of these loads on the boat shape. The resulting def…

Metodologie di progettazione innovative In campo navale

An algorithm for CAD modelling and optimisation of sailing boats under regatta bonds: application in the case of IMS class

A multi-technique simultaneous approach for the design of a sailing yacht

In this paper, most significant steps involved during the whole process of designing a sailing yacht are outlined. In particular, a novel simultaneous approach has been proposed to optimize the design process of a sailing yacht. Analytical resistance prediction models are simultaneously used with CAD systems and computational fluid dynamics tools to find, in the more effective way, the best solution for the chosen design conditions. As a general rule, in fact, once the target point has been decided, task of the designer is the definition of those systems of aerodynamic and hydrodynamic forces that are in equilibrium when the boat sails at its target. Unfortunately, a multi-purpose yacht doe…

Sistema di supporto per vela alare semi-rigida

La presente invenzione si riferisce ad un sistema di supporto per vela alare, in particolare per una vela alare semi-rigida a geometria variabile per uso nautico.

Progettazione e Confronto di Barche a Vela Mediante Analisi CFD

Le simulazioni fluidodinamiche computazionali (CFD) forniscono uno strumento particolarmente utile alla valutazione delle caratteristiche di barche a vela. La possibilità di studiare differenti carene e piani velici, ha permesso di mettere a punto geometrie che senza l’ausilio di queste tecniche innovative sarebbero apparse difficilmente raggiungibili. Nel presente lavoro sono state messe a confronto due barche a vela progettate e costruite per partecipare alle regate di Mille e una Vela per l’Università – manifestazione didattico/sportiva organizzata dall’Università Roma Tre.

Ottimizzazione fluido-strutturale di un timone navale

Integrazione di Tecnologie CAE in Ambienti VR

Applying virtual reality (VR) to numerical analyses (finite element –FE or fluid dynamics - CFD) produces considerable advantages, both for costs and for quality, in the mechanical engineering design process. Generally, during the stage of structural tests, after having carried out the CAD model, the designer runs FE and/or CFD analyses. Clearly, hardly ever, the obtained results are satisfactory during the first iteration, so that the designer, after having analysed the first data, needs to modify some parts of the model and to carry out a new analysis. Such re-analysis process is very improved and faster if it is carried out in a virtual reality environment; that because using the virtual…

Real-time non-contact ultrasonic detection of surface defects on objects moving at high speed

Il rilievo di difetti superficiali durante le ispezioni periodiche è importante poiché in genere le sollecitazioni sono maggiori in superficie e possono accelerare la crescita delle discontinuità. I difetti superficiali possono essere rilevati utilizzando alcuni metodi tradizionali di controllo non distruttivo, quali correnti indotte, liquidi penetranti, polveri magnetiche ed ultrasuoni. Alcuni tra questi metodi possono essere usati solo in condizioni statiche; gli altri presentano delle limitazioni per l’ispezione dinamica. I progressi recenti nel campo dei sensori ultrasonori senza contatto ci hanno permesso di sviluppare un sistema semplice per l’ispezione in tempo reale di corpi in movi…

Parametric Hull Design with Rational Bézier Curves and Estimation of Performances

In this paper, a tool able to support the sailing yacht designer during the early stage of the design process has been developed. Cubic Rational Bézier curves have been selected to describe the main curves defining the hull of a sailing yacht. The adopted approach is based upon the definition of a set of parameters, say the length of waterline, the beam of the waterline, canoe body draft and some dimensionless coefficients according to the traditional way of the yacht designer. Some geometrical constraints imposed on the curves (e.g., continuity, endpoint angles, curvature) have been conceived aimed to avoid unreasonable shapes. These curves can be imported into any commercial Computer Aide…

Finite element reanalysis in virtual reality environments

Avviamento delle Carene Mediante Tecniche di Ottimizzazione

CFD Study of an Innovative Catamaran with Asymmetrical Hulls

The purpose of this paper is the study of the shape of catamaran with asymmetrical hulls by both experimental and numerical viewpoint. The experimental study is based on the towing tank tests on a catamaran hulls shape obtained from previous works, showing that the wave resistance is very low produces a lower energy loss and a greater effectiveness. The hulls shape is optimized by the CFD application by force of commercial software, which shows that the reduction of wasted energy is very sensitive to make some changes; in particular three different width of the catamaran are tested and their performances are compared.

Parametric Design of Sailing Hull Shapes

The author presents an original algorithm aimed at automatically generating the hull shape of a sailing yacht starting from an initial set of parameters. The procedure consists of two steps. First one keel line and a Designed Water Line (DWL in the following) are faired according to a set of parameters, say length of water line, canoe body draft, stem angle and some adimensional coefficients. This information is then used to fair the hull surface, which must in turn fulfil more prerequisites (parameters like displaty cement, floatation area and related coefficients). The hull is defined by means of a B-spline surface, the fairing of which is ensured by allowing for all the imposed objective…

Optimization of a Vehicle Shape by CFD Code

In this paper, fluid dynamics simulations have been executed using a CFD (Computational Fluid Dynamics) commercial code, on a Maserati Biturbo mod. 222 - 1988. At first some surfaces are optimised, choosing the more important ones for the reduction of the resistance, by a manual variation of their geometry, hence a large surface is optimised in an automatic way, by means of an own software, developed in the MatLab environment, returning the optimised surface according to a specific objective function (the resistance in this paper). The aerodynamics resistance results are given under the form of aerodynamics penetration coefficient CD, taking into account the vehicle shape effect, the speed,…

Una Barca a Vela in Ottima Forma

Using FEM simulation to predict structural performances of a sailing dinghy

The use of finite element method (FEM) tools is proposed to investigate the structural response of an eco-sustainable sailing yacht to different loading conditions, typical of those acting during regattas. The boat is, in particular, a 4.60 m dinghy with the hull and the deck made of an hybrid flax–cork sandwich and internal reinforcements made of marine plywood. A preliminary activity has consisted in the refitting of an existing model in order to reduce the hull weight and to improve performances during manoeuvrings. These tasks have been interactively simulated in the virtual environment of the boat CAD model, where longitudinal and transversal reinforcements were enlightened and the m…

Parametric Hull Design with Rational Bézier Curves

AbstractIn this paper, a tool able to support the sailing yacht designer during the early stage of the design process has been developed. Quadratic and cubic Rational Bézier curves have been selected to describe the main curves defining the hull of a sailing yacht. The adopted approach is based upon the definition of a set of parameters, say the length of water line, the beam of the waterline, canoe body draft and some dimensionless coefficients according to the traditional way of the yacht designer. Some geometrical constraints imposed on the curves (e.g. continuity, endpoint angles) have been conceived aimed to avoid unreasonable shapes. These curves can be imported in any commercial CAD …

Designing the internal reinforcements of a sailing boat using a topology optimization approach

In naval design it is common practice to define an internal regular web frame made of longitudinal elements and transversal sections with the purpose of giving stiffness to the whole structure and, at the same time, promoting lightness. In this work, FEM simulation and Topology Optimization (TO) tools are implemented to present a different approach in placing the reinforcements inside the hull of a sailing dinghy. The methodology proposed in this paper considers as a starting point the volume inside the hull and the deck completely filled with material and the result after the simulations is a free form shape of the sailboat reinforcements. The TO procedure is based on two different input F…