A sizing approach for stand-alone hybrid photovoltaic-wind-battery systems: A Sicilian case study

Abstract Solar and wind energy are the two most available renewable energy resources in the world. In this paper, a high-resolution analysis that allows sizing a hybrid photovoltaic-wind turbine-battery banks has been carried out. The analysis aims to minimize the annualized cost of the systems satisfying two reliability constraints. The solution has been obtained numerically by means of an iterative technique. The decision variables are the photovoltaic area, wind turbine radius, and battery capacity. A high-resolution model, based on fuzzy logic inference system, has been developed to evaluate the number of active occupants and the domestic electricity consumption. In order to allow a mor…

Numerical experimental analysis of hybrid double lap aluminum-CFRP joints

Abstract Due to their reliability and ease of assembly, both the adhesively bonded and the mechanical joints are commonly used in different fields of modern industrial design and manufacturing, to joint composite materials or composites with metals. As it is well known, adhesively bonded joints are characterized by high stiffness and good fatigue life, although delamination phenomena localized near the free edges may limit their use, especially for applications where corrosive environments and/or moisture can lead to premature failure of the bonding. In these cases, a possible alternative is given by the well-known mechanical joints. On the contrary, these last joints (bolted, riveted) requ…

Modello di previsione della crescita di una cricca in un giunto incollato

IMPIANTO DI STABILIZZAZIONE DI UNA IMBARCAZIONE A SOSTENTAMENTO ALARE

Lo studio, frutto dell’attività di ricerca svolta dal DICGIM dell’Università degli Studi di Palermo in partnership con l’Engineering Department della Ustica Lines S.p.A. nell’ambito di un progetto finanziato con fondi PON Ricerca e Competitività 2007-2013, analizza preliminarmente le cause di guasto comportanti la fermata di un battello a sostentamento alare HSC per trasporto passeggeri al fine di individuare i componenti critici del mezzo. Individuato tale componente nel sistema di stabilizzazione, viene valutato l’impatto economico che il fermo del battello comporta sui costi operativi della Compagnia di navigazione. L’entità di tali costi, anche in termini di mancata utilizzazione del me…

PROGETTAZIONE DI UN MECCANISMO DI MOVIMENTAZIONE DEI FLAPS DI UN ALISCAFO

Lo studio, frutto dell’attività di ricerca svolta dal DICGIM dell’Università degli Studi di Palermo in partnership con l’Engineering Department della Ustica Lines S.p.A. nell’ambito di un progetto finanziato con fondi PON Ricerca e Competitività 2007-2013, analizza preliminarmente le cause di guasto comportanti la fermata di un aliscafo HSC per trasporto passeggeri al fine di individuare i componenti critici del mezzo. Individuato tale criticità nel sistema di stabilizzazione, viene valutato l’impatto economico del fermo del battello sui costi operativi della Compagnia di navigazione. L’entità di tali costi, anche in termini di mancata utilizzazione del mezzo, comporta la necessità di un ap…

Study of a Semi Active Electromagnetic Regenerative Suspension

The main objective of this work is the theoretical and numerical study of a device that allows recovering energy from an automobile suspension. In place of the viscous damper, which dissipates the kinetic energy of the vehicle due to rough roads or more marked obstacles, an electromagnetic damper performs the functions of the viscous shock absorber with a recovery of electric energy. The damper has permanent magnets and its working is based on the electromagnetic induction. The used ferromagnetic material is the Supermendur, which has very good ferromagnetic properties, but is expensive and difficult to found, so that the choice of different material is useful to reduce the costs. The mathe…

Experimental and numerical analysis of aluminum-aluminum bolted joints subject to an indentation process

Abstract The increasing interest of the industry (especially automotive, aviation and marine) in the fastener joints (riveted, bolted, etc.) between metallic materials, has re-opened the study on the possibility to improve the performance of the drilled structure using plastic deformation processes. Indentation process, performed before the drilling operation, creates circumferential compression stresses around the hole which increase significantly the mechanical performance of the drilled structures. In this paper, static and the fatigue performances of aluminum–aluminum (AW 6082-T6) single-lap bolted joints are studied. In particular, the study compares the mechanical strength of only dri…

ANALISI SPERIMENTALE DELLA DISTRIBUZIONE DELLE PRESSIONI AL CONTATTO RUOTA-SUOLO PER UN PNEUMATICO DA FUORI STRADA

Numerical and experimental analysis of a high innovative hydrofoil

The hydrofoil is a craft where the weight is entirely supported by the lift generated by the submerged part of wings. The particular structure of the craft requires a thorough study of the architecture of the hull, whose structure differs from others high speed vessels since the lift on wing surfaces are transmitted to the hull in limited areas (wing attacks). The authors have developed a research to optimize geometry of hull and wing system on a hydrofoil capable to carry 250 passengers at a speed of 35 knots, operating among Sicilian island. The principal goals of the new hydrofoil concern both the fuel reduction that the improvement of the comfort in terms of seakeeping and levels of aco…

Design of a Close Power Loop Test Bench for Contra-Rotating Propellers

The aim of the research is to develop an azimuthing contra-rotating propeller for commercial applications with a power of 2000 kW. The thruster system is designed especially to be installed on high speed crafts (HSCs) for passenger transport with a cruising speed of about 35–40 knots. The topic is very useful because the azimuth thruster solutions currently do not find commercial applications in naval units for passenger transport. The latter are heavy, not very efficient from a hydrodynamic point of view and suitable for maximum cruising speed of about 18–20 knots. The study is interesting because among the advantages that these solutions provide are the possibility of transmitting very hi…

STRUCTURAL OPTIMIZATION AND STRUCTURAL ANALYSIS OF COMPOSITE MATERIAL PANEL FOR NAVAL USE

The purpose of the work is the realization of a composite material with long glass fibers having better characteristic than a fiber random composite, to permit the reduction of weight and costs to shipyards for pleasure craft. Structural optimization is performed by ANSYS for the choice of the layers disposition to obtain the maximum stiffness with minimum material employment, saving weight. The study is centered on the research of the better configurations of plies packing in relation of pure shear stress for four different plies. Unidirectional plies, both symmetric orthotropic and symmetric non-orthotropic ones, are realized successively by the vacuum bag technique. Experimental tests of…

ANALISI DEGLI EFFETTI DEL CAMPO MAGNETICO SULLO STATO TENSIONALE INDOTTO IN PIASTRE DI ACCIAIO FORATE

Si è considerata una piastra forata di materiale ferromagnetico opportunamente accoppiata da bobine di filo di rame smaltato alimentato da un alimentatore DC a 30V. Essa è stata analizzata agli Elementi Finiti e successivamente sono state eseguite sperimentazioni per la validazione dei risultati ottenuti. Dopo aver levigato la piastra sono stati installati due estensimetri per misurare la deformazione lungo l’asse x e lungo l’asse z. Si sono ottenuti i valori di deformazione di 5µm in direzione z e -2µm in direzione x. Il confronto numerico-sperimentale mostra che i risultati di laboratorio sono più bassi di quelli numerici, mentre segni e ordini di grandezza sono gli stessi. Si conclude ch…

Effects of clearance on thick, single-lap bolted joints using through-the-thickness measuring techniques

Composite materials have increasingly become more common in ground transportation. As this occured thicker panels, as compared to composite panels used in aviation, become necessary in order to withstand high impact loads and day to day degradation. The effectiveness of these panels was often limited by the strength of the joint in which the panel was attached to the frame of the vehicle. Investigating methods of reducing strain concentrations within these joints would increase the effectiveness in using composite materials in ground transportation applications by increasing the load necessary for joint failure to occur. In this study, fiber optic strain gages were embedded in a composite p…

Dual compensation control-system for offshore logistic equipment

In offshore applications and moreover in transports from ship-to-ship, the needs of highly sophisticated motion compensation solution are increasing. They consist of sensors, actuators and control units. To design the best mechatronic solution, it is necessary modeling the mechanical system in order to identify the transfer function and the dynamic behaviour of the system. Currently Active Heave Compensation system are widely used in order to compensate for heave vessel motion. between a vessel moving under sea state and a fixed base or viceversa. Several research project are ongoing in order to develop solution able to compensate undesired movements also in ship to ship offloading operatio…

New relations between professional and work’s organizations introduced by computer applications, special vessel case study

At present time the project of a naval vehicle, where with the word project we refer to all the process of design and manufacturing, especially when the vehicle offers special formal and performance characteristics, involves a number of operators that has been increasing considerably in recent decades, and this increased complexity can be correlated with dimensional and typological growth of many categories of ships. Simultaneously we are witnessing a complete new project approach, where the possibility given by the computer contribution to represent processes and results becomes crucial. The paper aims to investigate the consequences of this progress in the organization of the project and …

Cyclic Delamination Analysis: Experimental and Cohesive-Frictional interface Finite Element Modelling

Comfort-structural analysis in product development Optimization of a motorcycle frame

This work steps from a bachelor thesis, joining the results of a study about the dynamic loads to evaluate the comfort loss in the motorcycle during the usage, with the potentiality of a modern FEM software. The goal is the development of a new methodology for structural optimization of motorcycle’s frame. In many of cases the success of the structural optimization is linked with a two factors combination: the software and the strength of the engineer to condition the mathematical problem, defining parameters domain and technological constraints. A good alternative to the traditional load hypothesis linked to historical data or instrumental measurements is focused in this paper. Consistent …

EFFETTO DELL’ATTRITO NELL’AVANZAMENTO DELLA DELAMINAZIONE PER MODO II DI CARICO

Il lavoro valuta l’influenza della dissipazione energetica dovuta agli effetti attritivi che si sviluppano all’interfaccia tra le lamine di provini sollecitati a Modo II di carico. Sono state effettuate diverse prove sperimentali su compositi in fibra di vetro e resina epossidica soggetti a condizioni di carico cicliche e valore medio crescente, tali da mantenere le lamine del composito in continua aderenza. Al fine di valutare l’incidenza dell’attrito interlaminare nella delaminazione per Modo II, i risultati delle prove sperimentali sono stati riprodotti per mezzo di analisi agli elementi finiti utilizzando il programma di calcolo FEAP (con codice sorgente aperto), nel quale è stato imple…

ANALISI NUMERICO-SPERIMENTALE SUL COMPORTAMENTO A FATICA DI COMPOSITI CARALL RIVETTATI

Nel lavoro è descritto un modello di danneggiamento per provini CARALL (CArbon Reinforced ALLuminium), rivettati e non rivettati, sottoposti a prove di fatica mediante flessione pulsatoria a tre punti in controllo di spostamento. I provini sono realizzati sovrapponendo 8 lamine di tessuto intrecciato di carbonio [0°/90°] e resina epossidica con interposta una lamina in lega di alluminio 6061-T6 dello spessore di 0.8mm. Le prove sono state condotte su provini non rivettati (Tipo 1), su provini con due rivetti disposti simmetricamente ad una distanza d=22 mm dalla mezzeria (Tipo 2) e su provini con 2 rivetti disposti ad una distanza d=44 mm dalla mezzeria (Tipo3). L’analisi dei risultati sper…

Analysis of the maximization of wind turbine energy yield using a continuously variable transmission system

Abstract In this paper, an analytic study of the subject of mechanical power transmission in HAWT wind turbine has been carried out. For the most part, the study analyzes the use of continuously variable transmission (CVT) in order to allow the turbine and the electric generator to couple, allowing in turn, an unremitting transmission ratio adjustment. In low-wind sites, the design criteria suggest an oversizing of the wind turbine in order to generate adequate electrical power even at low wind speed. The proposed solution enhances the space of operating points since it allows the electric generator to release the rotational speed from the turbine one (limited due to structural integrity). …

Design of the stabilization control system of a high-speed craft

In this paper, the main causes of technical malfunction of a hydrofoil was analyzed. In particular, a preliminary analysis evaluates the economic impact for the navigation company of the periodical maintenance related to the keeping of the vessel in dry dock. The study demonstrated that the main critical points are focused on the fragility of the stabilization control system. The increasing of operating costs has motivated the realization of a study aimed at redesigning the stabilization system. The continuing failure of the stabilization system (usually in water-immersed) severely limits the use of the high-speed craft. The proposed design solution considers the positioning of the control …

Effect of Cold Working and Ring Indentation on Fatigue Life of Aluminum Alloy Specimens

The article deals with the fatigue life of plates with hole made of aluminum alloy. Specifically, the combined effect of cold working expansion and ring indentation on improved fatigue life performance was investigated. Multiple fatigue tests were performed to determine the cycles to failure and the corresponding W¨ ohler diagram. Experimental results were compared with those of nontreated specimens. The conclusion was that cold working expansion and indentation create a delay on crack formation and fatigue failure.

A Fiber Optic Strain Gage Sensor for Measuring Preload in Thick Composite Bolted Joints

Mechanical fastening is a popular choice in joining composites because of the ability to transfer high loads and the ease of assembly and disassembly. In this study, the failure behavior of composite–aluminum single lap bolted joint is investigated. In particular, the effects of varying the preload on the bolt are examined. In order to accurately measure the preload, a specialized sensor that uses a fiber Bragg grating sensor embedded in the bolt is proposed and created. This sensor is realized for the current tests but can be expanded to other applications. An experimental study of bolted single-lap joints varying the tightening torque value has been carried out and, in order to validate t…

Progetto e messa a punto di una macchina prova materiali a fatica a flessione piana per provini in composito

STUDIO NUMERICO-SPERIMENTALE DI GIUNZIONI IBRIDE A DOPPIA SOVRAPPOSIZIONE CFRP-ALLUMINIO

The adhesively bonded joints and the mechanical joints between structural components made by composite materials or between elements made by composite and metal, are commonly used in different fields of modern industrial design and manufacturing, since they are characterized by economy, reliability and ease of assembly. The bonded joints are characterized by high stiffness and fatigue life, although delamination phenomena localized near the edges of attack of the adherends may limit their use, especially in particular applications where corrosive environments and humidity can lead to premature failure. In these cases, a possible alternative is offered by the well known riveted joints. On th…

Numerical and Experimental Analysis of the Frictional Effects on 4ENF Delamination Tests Performed on Unidirectional CFRP

Abstract Progressive delamination in composite materials under static or fatigue loading condition are, in many structures, one of the predominant cause of failure. In the paper, an accurate study of quasi-static delamination growth under mode II loading condition is conducted. Several experimental tests are performed on composite laminates consisting of unidirectional carbon/epoxy layers. Four-point end-notched flexure (4ENF) test is employed in order to characterize the mode II interlaminar fracture toughness. The R-curve is obtained by means of optical and numerical determination of crack tip position. The energy release rate and the crack length are calculated through experimental deter…

Effects of the indentation process on fatigue life of drilled specimens: optimization of the distance between adjacent holes

The generation of permanent compressive stresses around the holes is recognized as a valuable mean to delay the onset and propagation of the defects and to extend the fatigue life of the mechanical components. In the work, a bilateral indentation process, performed on each side of the component, is widely used in order to create a residual circumferential stress field around the area to be drilled and that persists after the drilling operation. In order to evaluate the process parameters and to identify optimal geometric solutions, several static and fatigue tests are conducted on AW 6082-T6 aluminum alloy specimen where two holes are created. In particular, experimental tests on only drill…

Effect of the indentation process on fatigue life of drilled specimens

Design and manufacture of mechanical elements are strongly influenced by the evaluation of the residual stresses due to their effects on the material strength. This paper presents numerical and experimental results performed on AW 6082-T6 aluminum alloy drilled specimens when the hole is created after a bilateral indentation process. The plastic deformation induced by the indenters creates a compressive residual stress field around the hole, which persists after the drilling operation. Several numerical analysis have been carried out in ANSYS APDL explicit solver for different indentation depths and hole diameters in order to evaluate the compressive circumferential stresses, optimal proces…

Studio numerico di sistemi di cementazione per inlay in composito.

Nel lavoro è condotto uno studio numerico su diverse tipologie di cementazione per inlay in composito utilizzate in ambito odontoiatrico per il restauro dei denti anteriori e posteriori. Il comportamento meccanico dei diversi sistemi di cementazione è stato riprodotto numericamente mediante simulazioni FEM: infatti, la moderna tecnica odontoiatrica fa uso dei software agli elementi finiti per l’elevata versatilità ed economicità nello studio di soluzioni sempre diverse. Le simulazioni hanno permesso di prevedere lo stato tensionale e l’evoluzione di una delaminazione creata all’interfaccia bi-materiale.

Biomechanical Analysis of a New Elbow Prosthesis

Total elbow arthroplasty (TEA) is an effective and frequently used treatment for patients with debilitating elbow pathology. Total elbow prostheses have lagged behind those of the knee, hip and shoulder for different reasons, such as the high failure rate of the early designs. Concern remains regarding the longevity of TEA implants, especially in younger patients. The main cause of revision of the implant is usually related to the phenomenon of aseptic loosening mainly due to the cement-bone interface failure. Aim of this work is the biomechanical analysis of a new elbow prosthesis to investigate the mechanical behaviour at the cement-bone interface. For this reason, a musculoskeletal model…

EFFETTO DELLA PRESSURIZZAZIONE DEI FORI E DELL’INDENTAZIONE ANULARE SULLA VITA A FATICA DI PROVINI IN LEGA DI ALLUMINIO

Nel lavoro è investigato il comportamento a fatica di lastre forate in lega di alluminio. In particolare è valutata l‟influenza combinata dell‟espansione a freddo dei fori e dell‟indentazione sul miglioramento della vita a fatica. A tal fine sono state condotte diverse prove di fatica aventi lo scopo di valutare il numero di cicli a rottura e la conseguente curva di Wöhler. I risultati sperimentali sono stati confrontati con quelli ottenuti senza la realizzazione di alcun processo di espansione e di espansione-indentazione. Lo studio ha permesso di concludere che il processo di espansione ed indentazione anulare determina un ritardo nella nascita della cricca e della conseguente rottura a f…

ANALISI STRUTTURALE DI UN TIMONE PER ALISCAFI

Attualmente i sistemi di controllo direzionale (timone) e di stabilità (flap) dei battelli veloci per il trasporto passeggeri (HSC) sono realizzati con elementi scatolari in acciaio. Ciò è essenzialmente dovuto alle notevoli sollecitazioni idrodinamiche che tali elementi sopportano a causa dell’elevata velocità di crociera. L’esigenza di ridurre il peso di tali elementi e di aumentarne la resistenza alle azioni corrosive esterne spinge ad una ricerca su materiali e tecnologie di fabbricazioni innovative. In questo studio è presentato il progetto di un timone, realizzato in materiale ibrido composito e acciaio, da impiegare su un battello per trasporto veloce passeggeri.

EFFETTI DEL PROCESSO STRESSWAVE SULLA VITA A FATICA DI PROVINI FORATI IN LEGA DI ALLUMINIO: OTTIMIZZAZIONE DELLA DISTANZA TRA FORI ADIACENTI

STRUCTURAL OPTIMIZATION AND EXPERIMENTAL ANALYSIS OF COMPOSITE MATERIAL PANELS FOR NAVAL USE

Effect of suturing the femoral portion of a four-strand graft during an ACL reconstruction

Purpose A suture passed along the part of the graft that will be inserted into the femoral tunnel is widely used by surgeons, because it could prevent the graft sliding on the femoral fixation device during pulling from the tibial side. The aim of this study was to evaluate the biomechanical effects of suturing the intratunnel femoral part of the graft during an anterior cruciate ligament (ACL) reconstruction. Methods Bovine digital extensor tendons and tibias were harvested from 20 fresh-frozen mature bovine knees ranging in age from 18 to 24 months. Quadruple-strand bovine tendons were passed through the tibial tunnel and secured distally with a bioabsorbable interference screw. In one ha…

Three-Dimensional Strain Analysis of Single-Lap Bolted Joints in Thick Composites Using Fibre-Optic Gauges and the Finite-Element Method

Bolted joints involving composite plates used to be almost entirely dedicated to aerospace applications. As the need for energy conservation has increased, the field of composite bolted joints has found new applications in ground armoured vehicles. Thick panels able to withstand large in-plane and impact loads are critical. The present investigation evaluates the interior strain field, through the thickness, of a composite plate connected to an aluminium panel with a single-lap bolted joint. The area of interest is the bearing plane region close to the hole because of the presence of stress concentrations that heavily modify the stress field. Experimental data for the bolted joint were rec…

Cohesive delamination and frictional contact on joining surface via XFEM

In the present paper, the complex mechanical behaviour of the surfaces joining two different bodies is analysed by a cohesive-frictional interface constitutive model. The kinematical behaviour is characterized by the presence of discontinuous displacement fields, that take place at the internal connecting surfaces, both in the fully cohesive phase and in the delamination one. Generally, in order to catch discontinuous displacement fields, internal connecting surfaces (adhesive layers) are modelled by means of interface elements, which connect, node by node, the meshes of the joined bodies, requiring the mesh to be conforming to the geometry of the single bodies and to the relevant connectin…

DETERMINAZIONE DELLE TENSIONI RESIDUE IN GIUNTI FSW A T MEDIANTE METODO DEL CUT-COMPLIANCE

In questo lavoro è stato applicato il metodo del cut-compliance (CC) per la determinzazione delle tensioni residue in giunti friction stir welding (FSW) saldati con una forma T. È riconosciuto che il metodo del CC fornisce ottimi risultati per i giunti di testa la cui geometria è simile al provino CT per prove di fatica. In letteratura, tuttavia, non è presente alcuna applicazione di questo metodo a forme differenti da quelle del giunto di testa poiché non sono note le funzioni di peso e di forma per differenti geometrie. Per tale motivo, sono state effettuate delle simulazioni agli elementi finiti per stimare le funzioni di forma e di peso considerando la geometria dei giunti FSW saldati a…

Mixed Mode Delamination Analysis by a Thermodynamically Consistent Cohesive Interface Model with Independent Mode I and Mode II Fracture Energies

Abstract In the present paper a new thermodynamically consistent cohesive interface model is proposed; it based on a predefined Helmhotz free energy with a single scalar damage variable and produces two independent fracture energies, in pure mode I and pure mode II debonding conditions. The proposed model can also take in to account the frictional effects with a smooth transition of the mechanical behaviour, from the initial cohesive one of the sound material, to the frictional one of the fully debonded interface. The cohesive-frictional behaviour is based on the mesoscale geometric interpretation of the scalar damage variable, which distinguish sound and debonded fractions of a representat…

STRUCTURAL OPTIMIZATION OF INNOVATIVE RUDDER FOR HSC

Currently, directional and stability control systems (rudders and flaps) of high speed craft (HSC) are made by steel box-shaped elements. This is mainly caused by the high hydrodynamic stresses applied on these elements due to the high cruising speed of HSC. In order to reduce the weight of these elements and to increase the resistance to external corrosive action, innovative manufacturing technologies and new materials are studied. In this paper, innovative hybrid steel-composite rudder are presented to use in high speed craft.

Frictional effect in mode II delamination: Experimental test and numerical simulation

Abstract The present paper proposes an experimental and a numerical analysis of the frictional effect on the mode II delamination. Frictional stresses between the crack edges can absorb and dissipate significant energy contributions in the delamination zones, especially under cyclic loading conditions. The experimental tests are performed for a set of unidirectional End-Notched Flexure (ENF) composite specimens, which are subjected to fatigue loading law with increasing mean value. The numerical analyses are performed considering a cohesive–frictional constitutive model, which is able to reproduce the transition of the interface behavior from the sound elastic condition to the fully cracked…

Valutazione dell'usura nei carrelli per serramenti

Nel lavoro è valutato il comportamento di carrelli per serramenti in condizioni di carico variabile al fine di valutarne l’usura. Le prove dinamiche sono state condotte su una macchina di semplice concezione appositamente realizzata e adatta a garantire un moto alterno sotto carico. Per la valutazione dell’usura è stata eseguita una scansione molto accurata della geometria delle rotelle (prima e dopo aver effettuato le prove dinamiche) attraverso un sistema di rilevazione a luce strutturata COMET V STEINBICHLER. Il processo di scansione ha permesso di digitalizzare le rotelle con un’accuratezza dell’ordine di 5µm. I dati della scansione hanno evidenziato un aumento pressoché uniforme del di…

A New Approach for CAD Modelling of Customised Orthoses by Generative Design

The standard method of design and manufacturing customised orthoses is still very time-consuming due to their often very complex shape. Different authors have tried to solve this problem but, unfortunately, the proposed approaches cannot be easily used in clinical practice because they require substantial interaction among medical staff and engineers or technicians. The aim of this work is to present the framework of a new design approach that could allow clinicians to easily model a customised orthosis, without a skilled technician develops the entire procedure. In particular, an automatic process based on Generative Design has been implemented. The obtained results have demonstrated that …

Analisi dei meccanismi di delaminazione in un materiale ortotropo ed all'interfaccia di un composito ibrido

Optimal manufacturing and mechanical characterization of high performance biocomposites reinforced by sisal fibers

Abstract The increasing interest about eco-sustainable materials in the industrial production (automotive, civil construction, packaging), has led to the increase of the research works dealing with biocomposites. However, until now the most attention has been devoted to the development of short fiber biocomposites for non-structural applications, whereas only a few works have considered high performance biocomposites for structural applications. Consequently, the development of structural biocomposites from robust natural fibers, as sisal fibers, is a result expected from the scientific community, but not yet achieved. In order to give a contribution to the implementation of high performanc…

STUDIO NUMERICO-SPERIMENTALE SUGLI EFFETTI DEL PROCESSO STRESSWAVE IN PIASTRE FORATE IN LEGA DI ALLUMINIO

STUDIO NUMERICO E SPERIMENTALE SU GIUNZIONI DI ELEMENTI IN POLIETILENE SALDATI DI TESTA ED ELETTROFUSI

Analisi numerico-sperimentale per la determinazione delle tensioni residue in un giunto saldato

La durata di un componente dipende dall’interazione tra le caratteristiche meccaniche del materiale con cui è costruito e gli sforzi a cui esso è sottoposto. Per la determinazione dello stato tensionale agente, oltre agli sforzi dovuti ai carichi imposti durante l’esercizio, è necessario conoscere accuratamente gli stati tensionali residui derivanti dal processo di produzione. Generalmente, le tensioni residue sono indesiderate poiché possono essere di entità elevata e tale da ridurre la resistenza complessiva del componente meccanico. Un aspetto particolarmente insidioso delle tensioni residue è che la loro presenza viene generalmente riconosciuta solo dopo il verificarsi di un malfunziona…

Analisi numerico-sperimentale sull’influenza dell’attrito nella delaminazione in Modo II

DESIGN AND OPTIMIZATION OF A CHASSIS FOR A FORMULA SAE RACE CAR

In this paper, the design process of a new chassis for a Formula SAE car is presented. The chassis is undoubtedly one of the most important parts of the car, both for the influence that it has on the vehicle dynamic behaviour, and because it is the main component that assures the driver safety. The new designed chassis is composed of many structural tubular bars and has been equipped with systems for the joining of all the auxiliary members. After the definition of the masses distribution and the choice of the main dimensions, preliminary CAD and FEM models have been carried out for the evaluation of the structural behaviour of this kind of vehicle. Successively, in order maximizing the tor…

OTTIMIZZAZIONE DI UNA GIUNZIONE INCOLLATA A DOPPIA SOVRAPPOSIZIONE PER SANDWICH IN COMPOSITO

Grazie alle peculiari performances meccaniche, quali soprattutto l’elevata resistenza a flessione unita ad un basso peso specifico, le strutture sandwich in composito sono sempre più frequentemente utilizzate nella moderna progettazione industriale. Nel presente lavoro, considerando un composito sandwich con skins in vetroresina e core in PVC espanso, è stato eseguito uno studio numerico e sperimentale al fine di individuare la configurazione ottimale di una giunzione incollata a doppia sovrapposizione avente quali aderendi esterni le stesse skins del sandwich e aderendo interno costituito da un inserto in metallo o in composito. In dettaglio, previa preliminare ottimizzazione teorica della…

Analysis of the effects of magnetic field on the induced stress in drilled plates

Abstract A drilled plate of ferromagnetic material suitably coupled by coils of enameled copper wire fed by a DC power supply to 30 V is considered in this paper. It is analyzed with finite element and later experiments are performed to validate the obtained results. After polishing the plate, two strain gauges for measuring the deformation along the x axis and along the z axis are installed. The values of strain are 5 μm/m in z direction and −2 μm/m in x direction. The experimental–numerical comparison shows that the laboratory results are lower than numerical, while signs and orders of magnitude are the same. It is concluded that the results of the FEM analysis can be considered acceptabl…

Industry 4.0: Advanced digital solutions implemented on a close power loop test bench

Abstract The paradigm of Industry 4.0 allows to increase the efficiency and effectiveness of the production. Companies that will implement advanced solutions in production systems will increase their level of competitiveness and will be able reach high market shares. The present paper is focused on the development of advanced digital solutions to be implemented on a close power loop test bench designed to test high power transmissions for naval unit. In particular, the test configuration consists of a back-to-back connection between two identical mechanical reducers. Since the efficiency of these systems are very high, it is not necessary to use large electric motors, thus managing to conta…

Sustainable vehicle routing based on firefly algorithm and TOPSIS methodology

Abstract In a sustainable management of logistics, transportation plays a crucial role. Traditionally, the main purpose was to solve the Vehicle Routing Problem minimizing the cost associated with the travelled distances. Nowadays, the economic profit cannot be the only driver for achieving sustainability and environmental issues have to be also considered. In this paper, to satisfy the intricate limits involved in real vehicle routing problem, the study has been structured considering different types of vehicles in terms of maximum capacity, velocity and emissions, asymmetric paths, vehicle-client constraints and delivery time windows. The firefly algorithm has been implemented to solve th…

Experimental analysis of the contact pressure distribution in an off-road tyre

In this paper the results of experimental tests are shown, lead by extended method of measurement, on a tire for an off-road vehicle 175/82 R16, inserting Prescale paper at the contact with the ground. The experimental analysis of the pressures is lead, in cross-sectional direction, in 5 zones correspondents to the middle of the single dowels constituting the tread. The results are analyzed by means of software predisposed to the scope so as to go back easily to the value of the pressure. The obtained results are critically analyzed and the result are compared with those obtained by the formulas of Rowland and MacLaurin, and by the nominal pressure at ground, concluding that the expression …

Crack growth analysis at adhesive–adherent interface in bonded joints under mixed mode I/II

The propagation of an interface crack subjected to mixed mode I/II was investigated for two 2024-T351 aluminum thin layers joined by means of DP760 epoxy adhesive produced by 3M©. On the basis of beam theory, an analytical expression for computing the energy release rate is presented for the mixed-mode end loaded split (MMELS) test. The analytical strain energy release rate was compared by finite element (FE) analysis using the virtual crack closure technique (VCCT). Several fatigue crack growth tests were carried out in a plane bending machine to compare the experimental energy release rates to those of the analytical and FE solutions. Experimental results showed the relationship between t…

Implementation of eco-sustainable biocomposite materials reinforced by optimized agave fibers

Abstract Although several works have recently been published in literature about biocomposites, i.e. about composites with polymeric matrix reinforced by natural fibers, only a few articles have been devoted to the implementation of high performance biocomposites for structural and semi-structural applications. The present study aims to give a contribution by considering biocomposites obtained by using an eco-friendly partially bio-based epoxy (green epoxy) and sisal (agave sisalana fibers) obtained by a proper optimization process. Through a systematic experimental analysis, three different types of biocomposites obtained with a suitable manufacturing process, such as random short fiber bi…

Industry 4.0: smart test bench for shipbuilding industry

AbstractIndustry 4.0 promises to increase the efficiency of production plants and the quality of the final product. Consequently, companies that implement advanced solutions in production systems will have a competitive advantage in the future. The principles of Industry 4.0 can also be applied to shipyards to transform them into “smart shipyards” (Shipyard 4.0). The aim of this research is to implement an interactive approach by Internet of Things on a closed power-loop test bench equipped with sophisticated sensors that is specifically designed to test high-power thrusters before they are installed on high-speed crafts, which are used in passenger transport. The preliminary results of the…

A thermodynamically consistent cohesive-frictional interface model for mixed mode delamination

Abstract A new interface constitutive model based on damage mechanics and frictional plasticity is presented. The model is thermodynamically consistent, it is able to accurately reproduce arbitrary mixed mode debonding conditions and it is proved that the separation work is always bounded between the fracture energy in mode I and the fracture energy in mode II. Analytical results are given for proportional loading paths and for two non-proportional loading paths, confirming the correct behavior of the model for complex loading histories. Numerical and analytical solutions are compared for three classical delamination tests and frictional effects on 4ENF are also considered.

Analysys and optimization of an end double-lap bonded joint for GFRP composite sandwich panels

Although the best configuration of the joints used to connect a common GFRP sandwich panel with the main structures is the adhesively bonded one, that permit high static and fatigue performances as well as to avoid stress concentrations, mechanical or hybrid joints are still widely used in the industrial field. After a preliminary theoretical design, the optimal configuration of an end adhesively bonded double-lap joint constituted by a simple insert as internal adherent and the same face sheets as external adherent, has been researched. In detail, several experimental tests and successive numerical simulations under tensile and bending loading, performed by varying the main influence para…

Rapid evaluation of notch stress intensity factors using the peak stress method: Comparison of commercial finite element codes for a range of mesh patterns

The peak stress method (PSM) is an engineering, finite element (FE)-oriented method to rapidly estimate the notch stress intensity factors by using the singular linear elastic peak stresses calculated from coarse FE analyses. The average element size adopted to generate the mesh pattern can be chosen arbitrarily within a given range. Originally, the PSM has been calibrated under pure mode I and pure mode II loadings by means of Ansys FE software. In the present contribution, a round robin between 10 Italian universities has been carried out to calibrate the PSM with 7 different commercial FE codes. To this aim, several two-dimensional mode I and mode II problems have been analysed independe…

Analysis of the Behaviour of an Optimized Magnetorheological Brake

This paper presents the optimization process of MR – magnetorheological brake in order to define its configuration, and to reach the requested vehicle braking torque. FEM analysis previously carried out, concerning structural sizing of such a brake, showed that both braking torque and brake mass did not satisfy the requirements. Due to the necessity of limitation on the suspended mass of a motor vehicle, the optimization of the form of MR brake stator has been executed, including determination of its contribution to the total mass of the brake. Thus a percentage reduction of approximately 40% was obtained. In order to estimate the brake temperature which results from the transformation into…

SISTEMA INNOVATIVO PER LA STABILIZZAZIONE DI UN HSC

Studio numerico e sperimentale del danneggiamento a fatica dei materiali compositi ibridi

Fatigue crack growth of new FML composites for light ship buildings under predominant mode II loading condition

The use of light but strong materials is largely studied in various area of the shipbuilding, this because the need of reducing the weight, and especially the weight of all the structures above the main deck assume primary importance for the stability. Traditionally in fast boats like fast ferries, hydrofoils, patrol boats, the typical materials are Aluminum alloy or composites, both those materials have advantages and disadvantages, but the new development of technologies made possible to combine them, in order to have a new material, combining the advantages of both, in terms of fatigue resistance, firefighting characteristics. In this paper, predominant mode II fatigue delamination tests…

Studio numerico-sperimentale sulla resistenza a fatica di sistemi di cementazione per inlay in composito

Nel lavoro è valutata la resistenza a fatica di tre diversi tipi di cementazione per inlay in composito utilizzati in ambito odontoiatrico per il restauro dei denti anteriori e posteriori. Il comportamento meccanico dei diversi sistemi di cementazione è stato ricavato sperimentalmente mediante prove di fatica in controllo di carico e riprodotto numericamente mediante simulazioni numeriche agli elementi finiti (FEM). Le diverse simulazioni hanno permesso di prevedere lo stato tensionale e l’evoluzione di una delaminazione all’interfaccia bi-materiale.

Firefly algorithm based upon slicing structure encoding for unequal facility layout problem

Finding the locations of departments or machines in a workspace is classified as a Facility Layout Problem. Good placement of departments has a relevant influence on manufacturing costs, work in process, lead times and production efficiency. This paper analyses the problem of allocating departments with restrictions in terms of unequal area and rectangular shape within a facility, in order to minimize the sum of material handling costs taking into account the satisfaction of the aspect ratio requested. In particular, we propose for the first time a Firefly Algorithm based on the slicing structure encoding. The proposed method was tested comparing the results obtained from other authors on t…

Propagazione di difetti all’interfaccia adesivo aderendo in giunti incollati

Progettazione ed ottimizzazione di un telaio per vettura di Formula SAE

Ottimizzazione di un freno a fluido magnetoreologico per uso automobilistico

Il presente lavoro ha come oggetto lo studio numerico di un freno a fluido magnetoreologico (MR) per uso automobilistico tramite il codice agli elementi finiti ANSYS. In seguito ad un dimensionamento analitico preliminare del freno la realizzazione di un modello FEM magnetico permette un’accurata valutazione della distribuzione del campo magnetico nel fluido MR e la valutazione del momento frenante generato in seguito all’applicazione della corrente alla bobina. La successiva ottimizzazione in due fasi del circuito magnetico consente di migliorarne le prestazioni in termini di momento frenante e peso del dispositivo. L’analisi FEM termica di tipo dinamico permette infine di valutare l’andam…

Effect of the mutual position between weld seam and reinforcement on the residual stress distribution in Friction Stir Welding of AA6082 skin and stringer structures

Abstract In the paper, a numerical and experimental study was carried out to highlight the effect of the distance d between the weld seam and the reinforcement on the residual stress distribution in Friction Stir Welded AA6082-T6 structures. An L-shaped profile was welded to a sheet metal with varying tool rotation and distance d from the weld seam. The Cut Compliance method was used to determine the resulting longitudinal residual stress. A dedicated FE model for FSW was set up, validated and utilized to predict the longitudinal residual stress in the assembled part. The analysis allowed the identification of a few design guidelines in order to reduce the detrimental effects of the residua…

Design and use of a Fatigue Test Machine in Plane Bending for Composite Specimens and Bonded Joints

Polymeric and composites materials are increasingly used in industry as structural parts, so that specific information on their mechanical properties "at long term" (creep, relaxation, fatigue) are requested. The design and implementation of these components also requires that they are permanently connected together to perform certain functions. The use of adhesives in structural joints has increased over recent years thanks to the continuous development by companies which provide the market with adhesive having better and better mechanical properties. The main areas relate to the aerospace, aeronautical and automotive industries, where requirements are required for lightness and reliabilit…

Static strength and fatigue life of optimized hybrid single lap aluminum–CFRP structural joints

Hybrid bolted/bonded joints are used to assemble structural components, commonly made by carbon fiber reinforced plastics (CFRP), with aluminum frames. Hence, they have become common solutions in a number of modern structural applications in the industrial fields, as well as civil constructions. Unfortunately, due to the lack of understanding of the relationships between the multiple parameters of influence that characterize their mechanical performance, only limited improvement have been achieved so far over classical bonding approaches, in terms of static and fatigue strength. As a result, further studies are needed in order to better exploit the potential of hybrid bolted/bonded joints a…

Design of an Electromagnetic Regenerative Damper and Energy Harvesting Assessment

Design of an electromagnetic regenerative shock absorber is proposed in this paper. In order to increase the efficiency of land vehicles the sources of energy losses have to be eliminated, or reduced. For this reason, several systems, recovering kinetic energy and converting it into electrical power, were studied and designed in the last years. This energy, converted into heat in traditional systems, is recovered to increase the autonomy of the vehicle. The proposed device is constituted by a stator part which coils are placed in an innovative disposition. The moving part is constituted by a rod made in stainless steel with alternated permanent magnets and spacers, so that the relative moti…

Firefly Algorithm for Structural Optimization Using ANSYS

In the mid-1980s, several metaheuristic methods began to be developed for solving a very large class of computational problems with the aim of obtaining more robust and efficient procedures. Among them, many metaheuristic methods use bio-inspired intelligent algorithms. In recent years, these methods are becoming increasingly important and they can be used in various subject areas for solving complex problems. Firefly Algorithm is a nature-inspired optimization algorithm proposed by Yang to solve multimodal optimization problems. In particular, the method is inspired by the nature of fireflies to emit a light signal to attract other individuals of this species. In this work, a numerical stu…

DETERMINAZIONE DELLE TENSIONI RESIDUE IN PROFILATI IN LEGA DI ALLUMINIO SALDATI DI TESTA MEDIANTE FRICTION STIR WELDING

A model for predicting the mixed-mode fatigue crack growth in a bonded joint

Bonded joints are highly sensitive to the presence of defects and to the degradation phenomena, and this aspect represents the primary obstacle to their use in different structural engineering applications. Delamination in a bonded joint represents, in fact, one of the primary, most common and insidious causes of damage. In this paper, a numerical–experimental study on the crack propagation along the adhesive layer of a bonded joint specimen is carried out. Experimental study is focused on the evaluation of the damage modalities of a bonded joint when the specimens are subject to fatigue load. Experimental tests are compared with the results of several numerical analysis performed in ANSYS …

Enhancement of Static and Fatigue Strength of Short Sisal Fiber Biocomposites by Low Fraction Nanotubes

AbstractThanks to good mechanical performances, high availability, low cost and low weight, the agave sisalana fiber allows to obtain biocomposites characterised by high specific properties, potentially very attractive for the replacement of synthetic materials in various industrial fields. Unfortunately, due to the low strength versus transversal damage processes mainly related to the matrix brittleness and/or to the low fiber/matrix adhesion, the tensile performance of random short fiber biocomposites are quite low, and to date most of the fiber treatments proposed in literature to improve the fiber-matrix adhesion, have not led to very satisfactory results. In order to overcome such a dr…

Random short sisal fiber biocomposites: Optimal manufacturing process and reliable theoretical models

Although several works have been published in literature on agave fibers and their biocomposites, accurate information about the choice of both the fibers and the manufacturing processes that allow the user to optimize the biocomposites properties in terms of strength and stiffness are not yet available; also, no theoretical models that can be used for an accurate evaluation of the mechanical properties of these biocomposites, are reported.To this aim, the present work intends to give a contribution by considering green epoxy biocomposites reinforced by both short and discontinuous sisal agave fibers arranged in proper MAT-type fabrics. In particular, an optimized manufacturing process that…

An analysis of interface delamination mechanisms in orthotropic and hybrid fiber-metal composite laminates

Abstract The onset and propagation of interlaminar defects is one of the main damage mechanisms in composite materials. This is even more the case when considering layered materials comprising metallic laminae (typically Aluminium) and FRP laminae. Propagation of delamination mainly depends on the initial crack extension and its loading mode. This work presents some results of a combined analytical–numerical–experimental study on the onset and propagation mechanisms regarding interlaminar defects. Two cases have been analysed in particular, the first consisting of a glass-fibre reinforced epoxy resin laminate, and the second consisting of a hybrid laminate where a lamina of aluminium is lay…

GIUNZIONI BULLONATE FRA COMPOSITO E ALLUMINIO: STUDIO DEL GIOCO MEDIANTE FIBRE OTTICHE INGLOBATE NELLO SPESSORE

Le giunzioni bullonate di elementi in composito sono state da sempre utilizzate per applicazioni impegnative. Sono stati annegati estensimetri a fibra ottica nello spessore di un pannello in composito in prossimità della superficie di contatto piastra-bullone in un giunto ibrido composito-alluminio. Sono state eseguite diverse prove di trazione su provini single-lap joint con differenti valori del gioco tra bullone e foro. Le prove consentono di determinare una relazione fra il gioco tra bullone e foro e i valori delle deformazioni misurate dagli estensimetri a fibra ottica. Risulta che ad un incremento dei valori del gioco corrisponde un incremento dei valori di deformazione in prossimità …

Preliminary design of a magnetorheological brake for automotive use

After an initial study of the characteristics of magnetorheological fluids based on a thorough search in literature, a preliminary configuration of MR brake is proposed. It comes from the evaluation of the main factors influencing the design of an appropriate magnetic circuit, and then the performance obtained in terms of brake torque. The analytical study of the brake has allowed a first preliminary sizing. Through the subsequent execution of an electromagnetic finite element model, created in ANSYS, it was possible to assess more accurately the distribution of the magnetic field inside the MR fluid and hence the resistance to relative motion between rotor and stator. The work needs an acc…