INFLUENZA SUL COMPORTAMENTO DINAMICO DI UN ROTORE SOSPESO ATTRAVERSO CUSCINETTI MAGNETICI ATTIVI MEDIANTE μ-SYNTHESIS E LOOP-SHAPING DESIGN

In questo lavoro viene effettuato un confronto sul comportamento dinamico di un albero rotante quando è sospeso attraverso un sistema di due cuscinetti magnetici ciascuno costituito da due assi. Le sospensione magnetica attiva è ottenuta elaborando due diversi sistemi di controllo che realizzano la stabilità del rotore conferendo a quest’ultimo delle prestazioni robuste nel mantenimento degli spostamenti entro certi margini prestabiliti. Ognuno di questi sistemi di controllo è caratterizzato da otto ingressi e quattro uscite con la presenza di incertezze sul guadagno spostamento e guadagno di corrente; ciò è giustificato dal semplice fatto che gli apparati elettronici possono usurarsi con i…

INFLUENCE OF UNCERTAINTIES ON PD TUNING

The aim of this work is to present a method for tuning the parameters of PD controller under the influences of the uncertainties, in order to stabilize the position of a rotor supported by active magnetic bearings (AMBs). The uncertainties are relative to mass, transverse and polar moment of inertia of the rotor. The introduction of the uncertainties is due to an incomplete modeled dynamic of the system or in the case the system being subjected to a parametric variation. The presence of the uncertainties produces a set of differences among the values of the output. Poles displacement method is used to reach the asymptotically stability condition characterized by a periodic oscillation durin…

The Recovery of the Optimal Damping Constant by the MRF Damper

In this paper was studied a method to analyze the recovering of optimal damping constant because of temperature increasing in a shock absorber. The increasing on temperature leads to decreasing that constant by mean dynamic viscosity such to modify the dynamic behavior of a 2DOF system built-up by sprung and unsprung mass. A MagnetoRheological damper was designed according with the desired optimal damping constant once fixed temperature design. It was seen that the increasing of temperature this constant is lost. As MagnetoRheological-Fluids allows us to increase the viscosity, we use a control signal by a state feedback of reduced order to create a such magnetic induction field to recover …

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…

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

CONFRONTO TEORICO SPERIMENTALE DEL CAMPO TERMICO IN UNA OPERAZIONE DI SALDATURA DI TESTA

Sub-Optimal Control Law for Active Magnetic Bearings Suspension

This paper deals with the comparison of three types of sub-optimal control law for the stable levitation of a turbojet shaft, sustained by two radial active magnetic bearings (AMBs). Shaft is considered rigid for the procedure simplification. The utilized approach leads to development of different sub-optimal control laws to use in speed-varying simulations in the angular speed of the shaft. The first control matrix is obtained by explicit relationships of the parameters of the control law vs. speed, obtained using a curve-fitting procedure neglecting the speed-varying elements out of the main diagonal of each single block constituting the entire control matrix. The second control law is ob…

Vehicle Side Crashworthness by FEM and ANN

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…

Cinematic And Dynamic Analysis And Structural Verify Of An Innovative Motorcycle Suspension

Analisi di un timone navale

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…

Influence on the Dynamic Behavior of Full Car Equipped by Magnetorheological Damper via Switch on/off and h∞ Controller

This paper shows the influence on dynamic behavior of the car when it is equipped with magneto-rheological dampers controlled by a feedback. The feedback is built up in two ways; the first is implemented by a switch on/off control that is characterized by the injection of magnetic field with a constant value. It happens when a certain value of relative speed between the sprung and unsprung mass is exceeded. The second feedback is characterized by the H-infinity control which is based on the relative displacement in order to vary the magnetic field signal in a continuous manner. At the same time the H-infinity control of vehicle is maintained by taking into account the exceeding of speed sig…

DETERMINATION AND ANALYSIS OF HEAD AND CHEST PARAMETERS BY SIMULATION OF VEHICLE-TEENAGER IMPACT

This paper reports the results of multi-body numerical simulation of a vehicle crash with a teenager pedestrian. A previous technique utilized for adult pedestrian impact is applied. The work starts with the determination of the masses for the various segments of the body of a teenager with a total mass of 45 kg and then switches to the construction of the dummy and the middle-class vehicle in the Visual Nastran environment. Simulations are performed for both frontal impacts and lateral impacts, when the vehicle is travelling at a constant speed and when the vehicle is braking, following the Euro NCAP rules on the subject. The results are analysed by calculating the values of the head inju…

Guarnizioni metalliche multistrato. Una nuova metodologia di simulazione numerica

MULTIBODY NUMERICAL SIMULATION FOR VEHICLE – PEDESTRIAN CRASH TEST

The purpose of this paper is the simulation of vehicle – pedestrian crash test, executed by Visual Nastran. The evaluation of the damage caused to pedestrian is obtained following the EURONCAP directive. The vehicle virtual model, DIMA, follows closely the characteristics of a saloon car belonging to the small cars category. A total of 16 simulation tests are conduced; each characterized by different initial conditions. The vehicle advances with several speeds, at constant speed and in braking. The anthropomorphic model Dummy impacts with the vehicle in lateral or perfectly frontal position with respect to the front of the vehicle.

INFLUENCE OF UNCERTAINTIES ON ROTATING FLEXIBLE SHAFT SUSPENDED BY 4-AXIS RADIAL ACTIVE MAGNETIC BEARINGS µ-SYNTHESIS AND LOOP-SHAPING-DESIGN

This paper shows a comparison about dynamic behavior of a rotating shaft when it is suspended by 4-axis radial active magnetic bearing system. The active magnetic suspension is obtained by two different controllers which realize the robust stability and robust performance. The control systems used are µ-synthesis and loop shaping design procedure. Each of these controllers is characterized by fourinput and four output signals and the introduction of uncertainties on displacement gain and current gain is justified by the simple fact that during the time the component which constitutes these gains can be subjected to torn and worn which can lead the entire system to instability phenomena. The…

DEVELOPMENT OF AN ANTHROPOMORPHIC MODEL FOR VEHICLE – PEDESTRIAN CRASH TEST

The purpose of this work is the achievement of an anthropomorphic model for the virtual simulation of pedestrian – vehicle crash test. “Dummy” construction in Visual Nastran room does possible the preparation of crash test with several vehicle models. Its three-dimensional geometry is implemented by video animation software, extracting the geometry element for element, and its characteristics are in keeping with EURONCAP protocol. Every bodily segment properties are determined using the reference material on the movement biomechanics. At last fall tests from three different heights are simulated for the “Dummy” validation, obtaining a reliable result.

STUDY OF NEW AUTOMOTIVE REAR SUSPENSION MECHANISM

The paper presents firstly an introduction discussing: the problem’s statement emphasizing the actual problem of research of passenger car suspension to improve driving comfort and dynamic of the vehicle movement; aspects regarding the studies of car suspension mechanisms; the paper’s aims and objectives showing that a new configuration of suspension mechanism having in structure mobile frame and an actuator offering some important operational advantages is proposed. After this, the innovative concept is presented. The motions of mechanism elements and actuator and kinematic displacements are largely presented. The simulation using modern software (MSC Patran 2007, MD R2 Nastran and MSC ADA…

TORSIONAL STRESS CONCENTRATIONS IN SHAFTS: FROM ELECTRICAL ANALOGIES TO NUMERICAL METHODS

This paper presents the historical development of methods used for the study of torsional stresses in shafts. In particular the paper covers both analog methods, in particular those based on electrical analogies proposed since about 1925, and numerical methods, in particular finite difference methods (FDM), finite element methods (FEM) and boundary elements (BEM).

Optimal Damping Constant Investigation on a Quarter-Car

This paper shows an investigation on optimal damping constant performed in the frequency domain. The optimal damping constant is meant as that value that minimizes the acceleration of all connected bodies characterizing a two degree of freedom system sketching a quarter car. The connected bodies are sprung and unsprung mass respectively for quarter of chassis and tire, this last keeps the contact with the ground and it is connected with the sprung mass through a shock absorber characterized by spring and fluid damper. Optimal damping constant was determined by imposing analytical conditions on the expression of acceleration of two masses. Afterwards, the variation of acceleration and positi…

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 …

Engine/Transmission Matching

This chapter deals with the forecasting of vehicle performance on the road, according to the installed engine. It begins with Section 1, which shows the calculation of the resistance to motion, that is, the forces that the vehicle must overcome to advance on flat roads and uphill. The calculation excludes accidental resistance in curves because it is not essential for predicting the behavior of the vehicle on the road. Section 2 begins with the power characteristic, the forecast by traction–speed and power–speed diagrams, calculation of gear ratios, and then passing to the limits to the estimated acceleration, feature consumption, and distance. This chapter concludes with a section on the d…

Neural modelling of friction material cold performance

The complex and highly non-linear phenomena involved during braking are primarily caused by friction materials’ characteristics. The final friction materials' characteristics are determined by their compositions, manufacturing, and the brake's operating conditions. Analytical models of friction materials' behaviour are difficult, even impossible, to obtain for the case of different brakes' operating conditions. That is why, in this paper, all relevant influences on the friction materials' cold performance have been integrated by means of artificial neural networks. The influences of 26 input parameters, defined by the friction materials' composition (18 ingredients), manufacturing (five pa…

CONTROLLO SUB-OTTIMO PER UN ALBERO ROTANTE IN LEVITAZIONE MAGNETICA ATTIVA

Il presente lavoro ha come scopo quello di mettere in mostra le sostanziali differenze rilevate nel comportamento dinamico di un rotore supportato da cuscinetti radiali in levitazione magnetica attiva. Sono stati rilevati sia gli spostamenti radiali che la risposta in frequenza controllando il rotore dapprima con una legge di ottimo tempo variante e successivamente con una di tipo sub-ottimo, ricavata dalla precedente rendendola stazionaria rispetto alla velocità angolare. È mostrato come la presenza del controllo sub-ottimo annulla la dipendenza del segnale di controllo dalle componenti di spostamento non interessate dal sensore e riduce sensibilmente l’entità degli spostamenti radiali.

NUMERICAL STUDY OF THE PHENOMENON OF “BRAKE SQUEAL” IN THE DISC BRAKES. FIRST RESULTS

In this paper we consider the problem of disc brake noise, an unstable behaviour that occurs in disc brakes due to particular vibratory phenomena. The most obvious phenomenology is the product wheezing during braking. The numerous researches carried out have not yet reached satisfactory results for knowledge. There was a total of high frequency squeal, which depends only on the characteristics of the disc and not by brake complete. Finite element method is applied to achieve modal analysis; a linear model was developed noting that to eliminate or reduce the phenomena of noise brake is necessary that the ranges of calliper-disc frequencies modal do not overlap. The modal analysis of the runw…

Teenage cyclist - Pick up crash by multibody simulation; HIC evaluation and comparison with previous results

The study of the injury caused by Pick-up vehicle-teenage cyclist crash is presented in this paper. The vehicle has high frontal part, in order to compare the results with those obtained previously in the sedan and SUV - teenage cyclist crash. No variation is executed on the model of the teenage cyclist and the bike. Three different positions are analyzed: front, rear and lateral position. The injury on the cyclist head is examined by HIC criterion, in the way indicated in the rules. Correlation HIC – AIS is used to calculate the lethality of the injuries. A comparison is made between the results of the simulations for Pick up, SUV and sedan, concluding that the injury of the head is more d…

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

Head Injury Criterion: mini review

Head Injury Criterion (HIC) is the most important parameter in terms of human survival; it is indicative of brain injuries due to the impact of the head in numerous cases, with a vehicle. This index can be estimated by integrating the resulting acceleration of the head (measured in its gravity center) in a time window

FE Calculation Methodology for the Thermodynamic Fatigue Analysis of an Engine Component

Thermo mechanical fatigue problem is treated to define an analysis methodology permitting the strength evaluation by reliability viewpoint. The main difficulty is the lack of both theoretical and experimental information; consequently the problem is treated verifying continually the validity and the limits of the developing solution method. The main task of the activity described in this paper was the development of a numerical methodology, based on FE analyses, for the evaluation of the structural behavior of engine components subjected to thermo mechanical fatigue phenomena. The chosen application was the exhaust manifold of an IC engine; FE analyses were executed following the standard m…

Sistema di sospensioni interconnesse

DYNAMIC ANALYSIS OF MOTORCYCLE BEHAVIOUR ON THE ROAD WITH STEERING PLATE STRUCTURAL OPTIMISATION

Improvements of Fatigue Life in Drilling Structures by Both Cold Expansion and Indentation

ANALISI CFD DELLE PRESTAZIONI DI UN CATAMARANO CON SCAFI ASIMMETRICI DOTATO DI SOSTENTAMENTO IDRODINAMICO

Nel presente lavoro è proposto uno studio di ottimizzazione su di un catamarano a scafi asimmetrici con murate piane esterne, grazie al progetto di due alettoni posizionati trasversalmente alla direzione del moto al di sotto del piano di galleggiamento ai quali è affidato il sostentamento idrodinamico dell’intero catamarano. L’obiettivo finale dello studio è quello di ridurre la resistenza totale all’avanzamento del catamarano dopo aver progettato in maniera opportuna le due appendici alari. Le analisi CFD, sia del catamarano senza alettoni che del catamarano con agli alettoni, hanno dato la possibilità di operare un confronto tra i due catamarani evidenziando un beneficio del 38% in termin…

Study of the reliability of internal combustion engines by application of a Weibull model in bands

The performance of 1,6 l four-valve Otto cycle engines is examined in this paper from the point of view of excessive consumption of lubricating oil. Three failure bands were recognized, at low, medium, and high distance traveled, each one obtained from a sample of 15 vehicles. A “Weibull model in bands” was applied; we obtained a satisfactory result from the point of view of reliability and applied the method to several types of motor vehicle. FMEA analysis of a sample permitted identification of the principal causes of unevenness in cylinder surfaces and an evaluation of the methods of machining required to correct this unevenness. Finishing of cylinders with a flexible smoothing tool is a…

Multi-body numerical simulation of the distribution drive system in an internal combustion engine

V clanku je predstaven vyvoj metodiky pro vypocet dynamiky mechanismu motoroveho rozvodu. Vyuzity jsou techniky simulaci vicehmotovych soustav; pouzit byl software AVL/Tycon. Objektem vyzkumu byl vliv pracovnfho rezimu motoru na dynamiku retezoveho rozvodu s jednim (SOHC) a dvema (DOHC) vackovymi hndeli v hiave motoru. Analyza obsahuje dukaz, ze retezovy prevod zavadi (di'ky kinematickemu zaberu) vysokou frekvenci s velmi malou amplitudou v porovnani s harmonickymi frekvencemi od externi sil. Metodika umozhuje urdt zati'zeni vstupni'ho a pomocnych hridelu, zatizeni na strukturu motoru indukovane pres operne a napmaci kladky. Diky tomu se predstavena metodika stava vyznamnym nastrojem pro pr…

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…

DETERMINAZIONE DEI COEFFICIENTI AERODINAMICI DI UN VEICOLO DA TURISMO MEDIANTE ANALISI CFD

In questo lavoro ci si propone di determinare il coefficiente di penetrazione aerodinamica della carrozzeria di un veicolo da turismo mediante analisi CFD e di migliorarlo, modificandone la geometria senza stravolgerne la natura di fondo, e continuando a garantire un adeguato livello di sicurezza per i passeggeri e per i pedoni. Tale progetto nasce dunque, con l’obiettivo di studiare e limitare, dove possibile, le perdite dovute alla resistenza aerodinamica a cui è soggetto un veicolo. L’analisi fluidodinamica del veicolo in questione, la FIAT Bravo, nella sua seconda serie del 2007, è stata effettuata mediante un calcolo bidimensionale sul profilo della sezione di simmetria. Le caratterist…

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

STUDIO DEL COMPORTAMENTO DINAMICO DI UN MODELLO HALF CAR E CONFRONTO FRA AMMORTIZZAZIONE PASSIVA E SEMIATTIVA A FLUIDO MAGNETO-REOLOGICO

Questo lavoro inizia con la progettazione di massima del pistone di un ammortizzatore a fluido magnetoreologico, effettuata con l’ausilio di Solid Works e del software di simulazione magnetica FEMM. Le dimensioni preliminari sono state assegnate facendo uso delle relazioni teoriche, mentre il software FEMM ha confermato il risultato. Sono state poi ricavate le equazioni della dinamica di un modello half car, sia in forma di sistema di equazioni differenziali che in forma di spazio di stato. Tramite l’interfaccia SimuLink di MatLab, è eseguito un confronto fra i risultati ottenuti dal sistema in condizioni di funzionamento passivo con quelli in funzionamento semi-attivo. Scelta la geometria …

Tecnica delle costruzioni meccaniche

Multibody numerical simulation for vehicle – pedestrian crash test and analysis of characteristic parameters

BRAKING PROCEDURE ANALYSIS OF A PEGS-WIN VENTILATED DISK BRAKE ROTOR

La bicicletta sportiva. Caratteristiche geometriche ed inerziali. Simulazione dinamica

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…

Biomechanics Parameters in the Vehicle-Cyclist Crash with Accident Analysis in Palermo

The vehicle-bicyclist impact is studied in this paper. After analysis of the accidents in Palermo in the last years, the multibody simulation of the crash is executed by making use of Visual Nastran. Dummy, car and bicycle are those used in previous works. The attention is on a teenage cyclist, because the data on this argument are found in literature with difficulty. The impact is simulated at four different speeds until 50 km/h, with three different positions of the cyclist relative to the vehicle: frontal, side and rear. In particular the injury of the head is analyzed using the parameter HIC and the chest injury is analyzed by 3 ms criterion; the likelihood AIS 4+ is calculated, conclud…

Prediction of driving performance of a hybrid vehicle with CVT transmission

The purpose of this work is the description of the phenomenology of driving behaviour of a production car characterized by a hybrid powertrain and a continuously variable transmission (CVT), along with a theoretical study of consumption that provides results in agreement with the experimental ones obtained and reported by the Car Maker.

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

COMPORTAMENTO DINAMICO DI UN AUTOVEICOLO. INFLUENZA DEGLI ANGOLI CARATTERISTICI DELLE RUOTE

Head, chest and femur injury in teenage pedestrian–SUV crash; mass influence on the speeds

This work studies the teenage pedestrian–sport utility vehicle (SUV) crash; injury to the vital parts of the body, such as the head and chest, and to the femur is evaluated. More advanced injury criteria are applied, as provided in the rules. The multibody technique is applied by making use of SimWise software and of the teenager anthropomorphic model, the use of which is now consolidated. Head injury criterion (HIC) is used for the head, thoracic trauma index (TTI) criterion for the thorax in the case of side impact and 3 ms criterion in the case of frontal impact, while the force criterion is used for the femur. Both the TTI and femur load evaluation require non-substantial modifications…

Braking procedure analysis of a pegs-wing ventilated disk brake rotor

Fade test results of a ventilated disk brake rotor with pegs-wing performed by means of an inertia dynamometer, consisting of 14 repeated brake applications from an initial brake speed of 160 km/h down to 0 km/h, with constant deceleration are shown. The first brake application test results are compared to the FEM numerical predictions with MSC Visual Nastran on the entire disk. These conform well to the experimental data, although numerical thermal field is slightly higher than the experimental one. Besides, ventilated disk brake rotor shows great dimensional stability and the ability to dissipate a great amount of thermal flow.

RILIEVO FOTOGRAMMETRICO E ANALISI CFD DI COPPIE GENOA RANDA E CONFRONTO TRA FLYING SHAPE E DESIGN SHAPE

Le vele di una imbarcazione sono sottoposte a grandi spostamenti a causa della loro natura altamente flessibile, per tale motivo, la forma che assumono quando sono sottoposte alla forza del vento è differente da quella di progetto stabilita dal velaio. Nel lavoro gli autori propongono un metodo basato sull’utilizzo della tecnica fotogrammetrica per il rilievo in navigazione di vele in vera grandezza. L’utilizzo di tecniche ottiche di Reverse Engineering consente, infatti, la ricostruzione tridimensionale del modello dell’intera vela. Vengono costruiti i modelli CAD delle vele di un’imbarcazione di classe Meteor in condizioni di navigazione (flying shape) e in condizioni di progetto (design …

Catamarano a scafi asimmetrici ad alta efficienza idrodinamica

Intelligent Control of Vehicle Combination Braking Compatibility

Development of an anthropomorphic model for vehicle-pedestrian crash test

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…

Finite Element Simulation of Multilayer Metal Cylinder Head Gaskets

ABAQUS gasket elements are an efficient and flexible tool to study gasket applications. Nevertheless the usage of the ABAQUS gasket elements is not limited to gasket analysis, but it provides an effective improvement in structural analysis. The results point out that both the predicted contact pressure and the predicted stress distribution depend on the mesh topology. Several combinations of mesh dimension and topology are investigated. The purpose is the definition of a calculation methodology and the demonstration of the application potentiality. Complex models analysis highlights that the set methodology constitutes a very effective tool for the design and optimization of gasket, cylinde…

OPTIMAL DAMPING CONSTANT OF THE QUARTER CAR SHOCK ABSORBER

The paper aim is the investigation of optimal damping constant of a quarter car shock absorber that is performed in the frequency domain. The optimal damping constant refers to the value that minimizes the acceleration of all connected bodies characterizing a two degree of freedom system sketching a quarter car. The connected bodies are sprung and unsprung mass respectively for quarter of chassis and tire, the last one maintain the contact with the ground and it is connected with the sprung mass through a shock absorber characterized by spring and fluid damper. Optimal damping constant was determined by imposing analytical conditions on the expression of acceleration of two masses. Afterwar…

Analisi dinamica del comportamento su strada di un motoveicolo - con ottimizzazione strutturale della piastra di sterzo

Determination of Torsional Stresses in Shafts: From Physical Analogies to Mathematical Models

This paper presents the historical development of methods used for the study of torsional stresses in shafts. In particular, the paper covers both analog methods, especially those based on electrical analogies proposed circa 1925, and numerical methods, especially finite difference methods (FDM), finite element methods (FEM) and boundary element methods (BEM).

Optimization of wheel characteristic angles by numerical simulation, with verify of Pacejka Formulas

MULTIBODY NUMERICAL SIMULATION OF AN INTERNAL COMBUSTION ENGINE WITH APPRAISAL OF THE WEAR DAMAGE

An internal combustion engine at four times (Otto cycle) and three cylinders is simulated by multibody software MSC Visual Nastran. The bearings are simulated by means of the library of constraint of the software, putting a particular attention to bench bearings and to the lubrication conditions. The loads on the bench bearings and in both the feet and head of the connecting rods, are evaluated by dynamical simulation, so that the inertia loads can be take in account, considering the condition of the maximum couple furnished by the engine. By making the necessary hypothesis, the evaluation of the wear damage is executed by Bayer theory on zero wear, obtaining that a good expectation of life…

Studio termomeccanico di un freno a tamburo per veicoli pesanti

STUDIO NUMERICO DEL FENOMENO DEL “BRAKE SQUEAL” NEI FRENI A DISCO

Active magnetic bearing design study

The purpose of this paper is to propose a useful method to implement active magnetic bearings (AMBs) on an existing rotating shaft which rotates on conventional bearings. This is feasible if AMBs can produce the same reaction loads of conventional ones and if the size of vane is large enough to host an AMB. As this substitution could offer some difficulties due to the different size between magnetic bearings and conventional ones, a set of equations are performed to show that a variation of some parameters can solve this problem. The journal ratio is the geometrical parameter introduced to develop the present analysis. The variation of journal ratio does not produce a variation of the pole…

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…

FLUID MECHANICS ANALYSIS OF A SAILBOAT MAST

This study aims to analyze different configurations of mast-sail coupling of a boat with single sail and wishbone rig to vary the shape of the cross-section of the mast that is to assess the influence of the mast on the performance of the sail. The analysis is performed with four several shapes of the mast cross section and several angles of attack to the wind. The numerical simulations on different geometries show an improvement by using a wing shape for the mast rotated in the direction of the wind, in all the corners. This solution allows to rotate rigidly the system mast-boom-sail in order to maintain the same angle of incidence and maximize the efficiency of the sail. The efficiency in…

Ottimizzazione fluido-strutturale di un timone navale

HIC evaluation in teenage cyclist – SUV accident

The study of the crash between normal sedan and teenage cyclist was examined in previous paper, and is here continued analyzing the influence of the front part of the vehicle in the injury caused by the accident. The vehicle is a SUV, with high frontal part. No variation is executed on the model of the teenage cyclist and the bike. The position of the teenage cyclist regard to SUV is the same: three different positions are analyzed: front, rear and lateral position. The injury on the cyclist head is examined by HIC criterion, in the way indicated in the rules. Correlation HIC – AIS is used to calculate the lethality of the injuries. The work is arranged to calculate the damage to the chest …

STUDIO DI UNA FRIZIONE MAGNETOREOLOGICA PER AUTOVEICOLI

Dopo un’accurata ricerca bibliografica sui fluidi magnetoreologici, il loro comportamento ed impiego, si è passati alla progettazione di una frizione magnetoreologica per autoveicoli. Considerando le caratteristiche di coppia trasmessa e potenza, il dispositivo è stato dimensionato tenendo presente i vincoli di ingombro del veicolo preso in esame. Sottoponendo il dispositivo ad analisi magnetostatica agli elementi finiti, si è determinato l’andamento delle linee di flusso del campo magnetico nel meato di fluido e nelle zone di maggior interesse, calcolando la coppia teoricamente trasmessa dall’innesto.È stato anche eseguito il confronto delle prestazionifra una frizione MR ed una frizione t…

On the history of torsional stress concentrations in shafts: From electrical analogies to numerical methods

This article proposes a retrospective on experimental and numerical methods developed throughout the past century to solve the torsion problem in shafts, with particular emphasis on the determination of shear stress concentration factors in discontinuities of typical use in shaft design. This article, in particular, presents the theory and related solutions distinguishing between two classes of geometries: shafts with constant cross section and axisymmetric shafts with variable diameter. Emphasis is given to approaches based on physical analog methods and, in particular, those based on electrical analogies proposed since about 1925. Experimental methods based on structural physical models …

Effect of residual stresses and their redistribution on the fatigue crack growth in cold-worked holes

The cold-expansion process is widely used to enhance the fatigue life of structures with fastener holes. Various studies assert that the cold-expansion improves the fatigue strength of fastener holes; however, the improvement of fatigue life is difficult to quantify. The influence on fatigue life of cold-worked hole in a 6061-T6 alluminum allosy was studied by numerical and experimental tests. Fatigue crack growth tests were carried out to find the crack length and growth rates of crack propagating from hole edge. Thus, the cold-expansion process was modeled with a Lagrangian implicit code for metal forming to obtain the residual stress field. Progressive crack growth along the observed fat…

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…

Influence of the vehicle front shape inTeenage Cyclist-Vehicle Crash

In this work the data, obtained for the three vehicles (sedan, SUV and Pick Up), tested in previous works, are compared. Following the results found in the literature, particular emphasis is done on the speed of the teenager cyclist head at the instant of impact and the diagrams of the head speed and the chest obtained in the simulations are shown. The speed of the head is that absolute, and this is used for processing the data and the subsequent determination of the best values of the three geometric actual parameters identified in front of the vehicle. Absolute speed is preferred because using the relative speed respect to vehicle, some amounts that cannot be disregarded are omitted from …

Verifica dei risultati della normativa ISO 6336 sulle ruote dentate per mezzo di simulazione numerica

BEM application on an external problem comparison with both theoretical and finite elements results and observations on divergence strip

Abstract By means of a computer program the Boundary Element Method is applied to a central hole in an undefined plate with uniform load along the boundary. Results are compared with those obtained by Kirsch's theoretical solution and a previous analysis by the Finite Element Method. The calculus of percentage error shows the advantage of the Boundary Element Method on the external problem with regard to the Finite Element Method. The error causes near the boundary internal points are analysed with the existence of a strip, where the result is not reliable in evidence.

ROBUST CONTROL FOR A SUSPENDED ROTATING SHAFT BY RADIAL ACTIVE MAGNETIC BEARINGS

This paper shows a comparison based on dynamic behaviour of a rotating shaft when it is suspended by 4-axis active magnetic bearings under several control systems. The control systems used are μ-synthesis, loop shaping design procedure and Sub(H∞) robust control with the introduction of uncertainties on position and current gains of the actuators. Each of these controllers is characterized by four input signals and four output signals and the introduction of uncertainties on displacement gain and current gain is due to torn and worn of the components during the time, which can lead the entire system to instability phenomena. The comparison of the performances is obtained through the introdu…

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…

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.

STUDIO DI UN AMMORTIZZATORE ELETTROMAGNETICO A RECUPERO DI ENERGIA

Questo lavoro ha come obiettivo principale lo studio teorico e con supporto di software F.E.M. di un dispositivo che consenta recupero energetico da una sospensione automobilistica. In sostituzione allo smorzatore viscoso, che dissipa l’energia cinetica del veicolo a seguito dell’attraversamento di strade sconnesse o ostacoli più marcati, si è usato uno smorzatore elettromagnetico che svolga le funzioni dello smorzatore viscoso consentendo un recupero di energia elettrica. Lo smorzatore elettromagnetico è di tipo a magneti permanenti e il suo funzionamento si basa sul fenomeno dell’induzione elettromagnetica. Il modello matematico descrive il funzionamento dello smorzatore, restituendo i va…

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,…

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…

Theoretical and Experimental Comparison between the Resistance Components of a fast Catamaran in different Configurations

The investigation performed by the Authors represents the most recent development of a research presented in [1] and [2], in which the geometrical solutions of the hull have been obtained through an optimization process, made by using the CFD numerical methods. The most important result of this optimization was the wave resistance reduction, which arrived up to 20% of the total initial resistance. In this further process the hull catamaran model has been built and tested at the towing tanks of the Universities of Naples and Trieste. The results obtained in the numerical process have been compared with the experimental ones and the reliability of the numerical results will be proved. Then th…

Analisi dinamica multibody di un motociclo con telaio innovativo in lega di titanio

ON THE WEIGHT DISPLACEMENT IN CURVE AND THE ROADABILITY OF A 4WS VEHICLE

A simplified theory on the vehicle stability in curve is explained in this paper; it allows the calculation of the force on the wheels during the motion in curve, supposing unchanging the position of the rolling centre; moreover it does not take in account the turn of the wheels and the behaviour of the tires, so that the theory can be applied to 2WS and 4WS vehicles for vertical loads calculation. The virtual simulations of 2WS and 4WS vehicles are executed, extracting all the data interesting the vehicle stability; it needs the distinction between manoeuvrability and handling. The simulations of two different tests are executed: the elk test like manoeuvrability test and a similar one at …

SAFETY CONSIDERATIONS ON TEENAGE PEDESTRIAN-BUS IMPACT

This work studies the impact conditions between the adolescent pedestrian and the bus focusing on head and chest injury. The injury to the head is analyzed using both the Head Injury Criterion (HIC) 36 and the HIC15 parameters as established by the most advanced legislation and comparing the risk probability Abbreviated Injury Scale (AIS3+) and AIS4+. The parameter HIC15 gives a higher probability of risk with lower values, and therefore it can be considered more conservative. Moreover, the study of chest injury is performed with two different biomechanical parameters: the Thoracic Trauma Index (TTI) and the TTI(d); the last neglects the pedestrian mass. The results indicate that the param…

Appunti alle lezioni di Costruzione di Autoveicoli