Università degli Studi di Palermo
SCOPUS ID: 7101733772
Abstract: The design of a sailing yacht is mostly based on the traditional design techniques of trial-and-error which takes time and requires iterative corrections to reach the final result. Moreover, several design teams with different and complementary expertise are required. If the standpoint is the one of the designs of a pleasure yacht, most of the activities can be solved through the related standards. While, concerning regatta’s yacht, more deep investigations become mandatory and intensive application of digital design instruments is now a common practice in modern yacht design. In this paper, a parametric procedure has been set up aimed to design and numerically compare sailing hulls performances. The hull shape design follows the classical approach based on the definition of the main curves frame and the generation of a parametric surface. Preliminary information about the hull resistance can be quickly obtained with a dedicated module of the software. Once a satisfactory shape has been modeled, detailed investigations can be automatically executed with commercial fluid dynamics software. The procedure has been successfully applied to the design of a new boat belonging to a specific class-called 1001VELAcup R3- which is two people racing dinghy designed according to a box rule with limitations on materials, dimensions and total sail area. The availability of experimental data suggested the numerical investigation about the influence of the hull geometry on the sailing performances.
Keywords: CAD modeling | Numerical investigation | Yacht design
Abstract: 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 FEM solutions: one is the result of a structural analysis on the boat loaded with real forces acting during navigation and the other one is the result of a modal analysis aimed to extract natural frequencies of the structure. The result must fulfil several requirements such as weight, stiffness and stress. TO models have been compared with a traditionally designed sailboat with the same total mass and relevant improvements have been obtained in terms of local stiffness and reduction of moments of inertia.
Keywords: FEM | Reinforcement | Topology optimization | Yacht design
Abstract: 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 evaluating and optimizing downwind sail performance and manufacturing. A new weakly coupled fluid–structure interaction (FSI) procedure has been developed to study downwind sails. The proposed method is parametric and automated and allows for investigating multiple kinds of sails under different sailing conditions. The study of a gennaker of a small sailing yacht is presented as a case study. Based on the numerical results obtained, an analytical formulation for calculating the sail corner loads has been also proposed. The novel proposed methodology could represent a promising approach to allow for the widespread and effective use of numerical methods in the design and manufacturing of yacht sails.
Keywords: Computational fluid dynamics | Finite element method | FSI | Gennaker | Sail design | Sail loads
Abstract: 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 Aided Design (CAD) software and used as a frame to fit with a surface. The resistance of the hull can be calculated and plotted in order to have a real time estimation of the performances. The algorithm and the related Graphical User Interface (GUI) have been written in Visual Basic for Excel. To test the usability and the precision of the tool, two existing sailboats with different characteristics have been successfully replicated and a new design, taking advantages of both the hulls, has been developed. The new design shows good performances in terms of resistance values in a wide range of Froude numbers with respect to the original hulls.
Keywords: CAD | Excel | Rational Bézier curves | Sailing yacht design | VBA | VPP
Abstract: In 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 of internal reinforcements consists of a truss-like web frame with a final weight equal to the 18% of the initial full body.
Keywords: Reinforcement | Topology optimization | Yacht design
Abstract: In 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 software and used as a frame to fit with a surface. The algorithm and the related Graphical User Interface (GUI) have been written in Visual Basic for Excel. To test the usability and the precision of the tool, two sailboats with different characteristics have been replicated. The rebuilt version of the hulls is very close to the original ones both in terms of shape and dimensionless coefficients.
Keywords: CAD | Rational Bézier curves | Sailing yacht design
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” from the University of Palermo and “TryAgain” managed by the University of Naples but designed by the University of Roma3 team. These boats were definitely superior as regard motion resistance when tested without appendages during 2017 MIDWINTER INDOOR RACE and, although very different in main section shape, had comparable performances. The observed behaviours and the availability of experimental data suggested a suitable numerical approach and a fair comparison between experimental and numerical results is presented.
Keywords: 1001VELAcup | Box ruled racing dinghy | CFD | EFD | Sailing hull forms
Abstract: 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-Stokes solver is used with the k-ω SST turbulence model and the gamma transition criterion. A verification study is carried out based on four grids of systematically varied density, and results compared with experimental data on a NACA 64-006 section. The parallel-sided sections are modeled with rational Bézier curves whose geometrical parameters permit to link the shape of the profile to physical variables, which are systematically varied. Three Reynolds numbers and two angles of attack are investigated. Systematic plots show the influence of the trailing edge angle and nose radius for the different section families, and the optimum combination is presented in a table. Physical explanations of the trends, and of the exceptions, are given in the paper, using flow visualizations as well as pressure and friction plots.
Keywords: Bézier curves | CAD | Centerboard | Gamma transition criterion | Low Reynolds number | NACA | Parallel-sided | Sailing | Systematic investigation
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 deformed model is compared with measurements of local strains obtained with Electrical Resistance strain gauges applied on the hull and on reinforcements of the boat. Onboard measuring devices are real-time monitored with a home-made software while the numerical prediction of the global boat deformation is obtained a posteriori once FEM computation is achieved. A test at sea has been performed to check the efficiency of the system: data computed with the proposed procedure have been compared with those coming from the field test.
Keywords: Computer aided engineering | On board monitoring system | Sailing yacht
Abstract: 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 impact. The aim of this work is to verify the applicability of FDM to structural naval component subjected to demanding loads during navigation and, at the same time, to investigate on the robustness of a topology optimization strategy in creating new shapes that recent additive manufacturing are able to create.
Keywords: CAD modeling | Fused deposition modeling | Topology optimization
Abstract: 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 maximum beam reduced. At the same time, results of FEM simulations on the modified model were analysed in order to verify the structural integrity. Shape modifications have been applied to the real model in laboratory and the resulting hull has been instrumented with strain gauges and tested under rigging conditions to validate the numerical procedure. Finally, the FEM model was used to predict the response of the boat to loading systems typical of sailing conditions.
Keywords: FEM | Refitting | Sailing yacht
Abstract: 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 sailing yacht is also presented. The obtained results have demonstrated the efficiency of the new proposed low-cost method.
Keywords: CAD Model | CAE tools | Close range photogrammetry | Generative algorithms | Low-cost reverse engineering analysis | Sailing yacht
Abstract: 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 does not exist. If the target point is in upwind sailing then, performances will be better for such a condition and worse for others. The effectiveness of the proposed procedure has been tested by means of a case study related to the design of hull, appendages and sails of a 15” yacht subject to box-rules, designed and manufactured at the University of Palermo.
Keywords: Computational fluid dynamics | Conceptual design | Numerical methods | Optimization | Sailing yacht
Abstract: 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 experiments were compared.
Keywords: Parametric design | Refitting | Sailing yacht
Abstract: 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 reverse engineering model was checked through two different procedures implemented by the graphical algorithm editor Grasshopper. The first procedure has allowed to compare the photogrammetric measurements with the rebuilt surface, in order to verify if the reverse engineering process has led to reliable results. The second has been implement to measure the deviations between the original CAD model and the rebuilt surface of the hull. This procedure has given the possibility to highlight any permanent deformation of the hull due to errors during the production phase or to excessive loads during its use. The obtained results have demonstrated that the developed procedure is very efficient and able to give detailed information on the deviation values of the two compared surfaces.
Keywords: CAE tools | Close range photogrammetry | Generative algorithms | Reverse engineering | Sailing yacht
Abstract: 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 speed of the evolutionary process, the constraints on displacements and/or stresses, the desired volume reduction, etc. All these variables may influence significantly the final topology. The main goal of this work is to study the influence of both the different optimization parameters and the used efficiency criteria on the optimized topology. In particular, two different evolutionary approaches, based on the von Mises stress and the Strain Energy criteria, have been implemented and analyzed. Both approaches have been deeply investigated by means of a systematic simulation campaign aimed to better understand how the final topology can be influenced by different optimization parameters (e.g. rejection ratio, evolutionary rate, convergence criterion, etc..). A simple case study (a clamped beam) has been developed and simulated and the related results have been compared. Despite the object simplicity, it can be observed that the evolved topology is strictly related to the selected parameters and criteria.
Keywords: Efficiency criteria | Evolutionary optimization | FEM | Rejection ratio | Topology optimization
Abstract: 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 reduced. In the present work, such a mechanism is investigated by a phenomenological approach, performing periodical loading/unloading cycles, and repeating tensile tests on previously "yielded" samples to assess the evolution of stiffness behaviour. Infrared thermography is also employed to measure the temperature of specimens during monotonic and cyclic loading. In the first case, the thermal signal is monitored to correlate departures from the thermoelastic behaviour with the onset of energy loss mechanisms. In the case of cyclic loading, the thermoelastic signal and the second harmonic component are both determined in order to investigate the extent of elastic behaviour of the material.
Keywords: Crimped unidirectional textiles | Damage | Flax fibre composite | IR thermography | Tensile properties | Thermoelastic stress analysis
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 the local elastic indentation in the experimental evaluation of the flexural stiffness. This procedure is based on the analytical solution of an indented beam resting on a fully backed Winkler foundation.
Keywords: Agglomerated Cork Core | Composite Sandwich | Flexural Behaviour | Indentation | Long Flax Fibres | Winkler foundation
Abstract: 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 components and bones (humerus and scapula) involved in the shoulder joint. Following step has been the setup of numerical finite element method models to simulate use conditions. To this scope, analyses have been performed in accordance with experimental conditions found in literature. Stability conditions have been verified under the action of horizontal and vertical instability loads with different version angles between humerus and the humeral implant. In particular, the stability ratios of the prosthesis have been calculated for the analysed loading conditions. Obtained results show how the positioning has a great influence on the shoulder stability and allow the definition of guidelines for the application of this prosthesis. © 2014 Springer-Verlag France.
Keywords: 3D scanner acquisition | Non linear FEM analyses | Reversed shoulder prosthesis | Shoulder stability ratio
Abstract: 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 evaluate stresses and stability of the joining during normal working conditions. The new design has shown very high mechanical stability in the axial compression and torsional load cases. Since its very simple self-locking system, the new expansion intramedullary nail would reduce the operating time and the exposure to radiations for the surgeons as well as the patients. © 2012 Springer-Verlag France.
Keywords: Intramedullary nail | Non linear FEM analyses | Parametric CAD model | Redesign | Virtual prototyping
Abstract: The detection of surface defects during periodic inspection is important because, usually, the stresses are higher at the surface, thus affecting the growth of the discontinuity. Surface defects can be detected using some traditional non-destructive testing methods, such as eddy current, dye penetrant, magnetic particle and ultrasonic. Some of these methods can be used only in static conditions; the others have limitations for the dynamic inspection. The recent progress in the field of non-contact ultrasonic sensors has led us to develop a simple system for the real-time inspection of moving bodies at a high speed. The paper presents the possibility of using, with the developed system, two methodologies, based on non-contact ultrasound, to detect surface defects on objects moving at 100 km/h, so that in service inspection is possible. A methodology, based on laser and air-coupled sensors, uses the advantages of laser-generated surface waves; the analysis is done on the reflected wave, created by the interaction of the surface wave with the defect. The inspected surface layer can be selected from the wavelength of the surface wave. The other methodology, based on air-coupled sensors, uses the disadvantages of the ultrasound transmission at the air/metal interface; the analysis is done on the diffraction of the wave reflected from the surface. The execution of the inspection is simple with both techniques. The experimental results indicate a good efficiency of the two methodologies proposed for the real-time detection of surface defects on objects moving at high speed.
Abstract: This paper describes an approach to the keel design of a sailing yacht. The related software, which is fully automatic, leads to the optimal shape by modifying the surface used to define the keel planform. B-spline curves and surfaces have been used due to their ability in following complex shapes. The algorithm integrates ad hoc implemented original software with computational fluid dynamics (CFD) commercial ones. The optimisation procedure uses 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 centreboard of the 5o5 international class racing dinghy. © 2008 Elsevier Ltd. All rights reserved.
Keywords: CFD | Design optimisation | GAs | Sailing yacht
Abstract: 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 Reinforced Plastics (GFRPs), also a new topology of the vehicle frame; the designed semitrailer, in fact, has a monocoque structure. Copyright © 2007 Inderscience Enterprises Ltd.
Keywords: Composite material | Redesign process | Semitrailer | Structural frame
Abstract: 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 objectives and constraints. An optimisation technique based upon the gradient method ensures that a reliable solution is obtained in a very short time. © 2005 Elsevier Ltd. All rights reserved.
Keywords: CAD | Optimisation | Surface fairing | Yacht design
Abstract: Redesign of a product becomes necessary as a consequence of the evolution of the market requirements, of the man creativity, of the influence of the environmental factors, of the technological development etc. The redesign activity, especially in a context of exasperated economic competition, has become a crucial point in order to try to increase the competitiveness, if not even the life, of a product and/or a company. The redesign must allow the resumption of the increasing process of the performances. This aim requires a methodical and structured approach, which can also cause the modification of the standard conception of the product. In this paper the possibility to reduce the mass of a semitrailer is analysed, modifying its structure. Various solutions have been considered, characterized also by new topology and/or materials, and between all of them the one constituted from a structural floor in composite material has been chosen. © 2005 WIT Press.
Keywords: Composite material | Redesign | Semitrailer | Structural floor
Abstract: 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, the fluid properties and the orientation. Copyright © 2005 Inderscience Enterprises Ltd.
Keywords: Aerodynamic resistance | CFD simulations | Shape optimisation
Abstract: 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 coordinates of the keypoints of changeable boundaries constituted by curves. In both the steps the aim is that to find the variable sets producing the maximum stiffness of the structure, respecting an upper limit on the employed mass. The structural evaluations are carried out with a FEM commercial code, linked to the algorithm. Some applications have been performed and results compared with solutions reported in literature. © 2003 Elsevier Science Ltd. All rights reserved.
Keywords: Genetic algorithms | Shape optimisation | Topology optimisation
Abstract: 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.
Keywords: Composites | Misalignment error | Strain gauges
Abstract: Deformability and buckling load of yacht in fibers reinforced plastic sandwich depend on the skins stacked sequence. In this work an optimization of the laminae fibers direction of a competition yacht existing design 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 the ASTM D3039, employing strain gage technique. In the second part, by means of an original software in Turbo-Pascal (which uses the half-width value matrix as an input) linked to Pro/ENGINEER, has been possible to obtain the body plan and the surface and finite element models of the sailing yacht for the subsequent analyses. In the third step, an optimization procedure, that uses the results of FE structural analyses in three different navigation configurations, is performed, with the aim to obtain the fibers direction able to minimize the yacht deformability, taking in account buckling loads also. An approximated analytical model has been used in conjunction with a sweep technique in order to evaluate the best of the solutions.
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 technique. In the second part, by means of an original software in Turbo-Pascal (which uses the half-width value matrix as an input) linked to Pro/ENGINEER, it has been possible to obtain the body plan and surface and finite element (FE) models of the sailing yacht for the subsequent analyses. In the third step, an optimization procedure that uses the results of FE structural analyses in three different sailing configurations is performed, with the aim of obtaining the fiber directions that are able to minimize the yacht deformability, also taking into account the buckling loads. An approximate analytical model has been used in conjunction with a sweep technique in order to evaluate the best of the solutions.