Design methods for mobility

In this paper fluid dynamics simulations have been executed using a CFD (Computational Fluid Dynamics) commercial code, on a Maserati Biturbo mod. 222-1988. At first some surfaces are optimised, choosing the more important ones for the reduction of the resistance, by a manual variation of their geometry, hence a large surface is optimised in an automatic way, by means of an own software, developed in the MatLab environment, returning the optimised surface according to a specific objective function (the resistance in this paper). The aerodynamics resistance results are given under the form of aerodynamics penetration coefficient CD, taking into account the vehicle shape effect, the speed, the fluid properties and the orientation. Copyright © 2005 Inderscience Enterprises Ltd.

Keywords: Aerodynamic resistance , CFD simulations , Shape optimisation

In this work a web-based tool to simulate a competitive design environment is described. The speci c application, in particular, has been implemented to simulate a competitive tender for the design of a military aircraft. The teams which participate to the game are asked to design an aircraft which has to satisfy given speci cation. The tender is won by the team which gain the higher score, as detailed by the game rules. The proposed application can be used as an active teaching tool where students can be stimulated to develop their relational and practical capabilities. In particular the scholars can be encouraged to adopt the design techniques that can be applied to the management of complex models that cannot be represented through an explicit mathematical description.

In this paper, the activity aimed at the contact less acquisition, the generation of polygonal descriptive models, the generation of NURBS-based models and the reproduction by means of rapid prototyping tools of pieces of interest in both the heritage and the automotive domains are presented. The work gives an insight of how three-dimensional range cameras and suitable data modeling can be helpful in the reverse engineering and in the virtual representation of complex shapes. In addition, the research represents a valuable example of Computer Support Collaboration Work (CSCW) for the restoration and the rapid prototyping of the objects. © 2005 Taylor & Francis Group.

This paper presents a computer-aided design (CAD)-based system for ergonomics analyses of motorcycles, which includes three-dimensional models of vehicle configurations and equipment, three-dimensional human models of various anthropometries and evaluative techniques to assess reach and postures. The system is based on a modular structure that integrates an established top-down computer-aided design framework for motorcycle design, a widely used anthropometric database and specific behavioural criteria defined by an experimental procedure correlating driving postures and vehicle configurations. As a result, vehicle designers are able to use a single analysis tool to prognosticate and assess postural comfort, from the earliest stages of the design process. In the paper, issues in vehicle design with reference to ergonomics assumptions and posture evaluations by a computerized system are discussed.

Commonly, during the aesthetic design process, stylists sketch features called character lines over a simple and "uninteresting" geometry (e.g. a car bonnet) in order to confer personality, emotional feeling and style. This work presents an original interface paradigm for character line sketching in a virtual reality environment. Taking advantage of the 3D interface, the feature path, also called leading line, can be directly sketched on the initial surface by realtime projection. Afterwards, a semi-transparent section is selected along the path in a interactive way and then the feature profile is sketched on this plane according the user's intention. Subsequently, by moving the virtual pen forwards along the path, the character line is generated, on the contrary if the pen is moved backwards the feature is partially erased. The distance of the virtual pen from the leading line controls, in real time, the offsetting along the path of the feature which remains consistent in style and identity. Such a system has been proven to be a powerful tool for fast expression and evaluation of ideas, which can be, in subsequent design phases, integrated with detailed surfacing applications and prototyping.

Keywords: Constrained-based design , Curve and surface design , Feature-based design , Parametric modelling

A computational model and an experimental analysis have been performed to study the atomisation processes of hollow cone fuel sprays from a high pressure swirl injector for gasoline direct injection (GDI) engines. The objective has been to obtain reliable simulations and better understood structure and evolution of the spray and its interaction with air the flow field. The 3D computations are based on the KIVA 3 code in which basic spray sub models have been modified to simulate break-up phenomena and evaporation process. Spray characteristics have been measured using a system, able to gather and to process spray images, including a CCD camera, a frame grabber and a pulsed sheet obtained by the second harmonic of Nd-YAG laser (wavelength 532 nm, width 12 ns, thickness 80 μm). The readout system has been triggered by a TTL signal synchronized with the start of injection. A digital image processing software has been used to analyse the collected pictures. Computed and measured spray characteristics, such pre-spray and main-spray structure, tip penetration and break-up phenomena, have been compared, achieving good levels of agreement. Copyright © 2002 Society of Automotive Engineers, Inc.

The design of a "high-performance" airbox for a naturally aspirated internal combustion engine (ICE) of a car racing in prototype sport competitions is described. A computational approach to achieve optimum airbox geometry in terms of fluid dynamical losses reduction and engine volumetric efficiency improvement is proposed. Experiments on race track have been carried out to test the car performances improvement. The numerical calculations have been done using a 3D numerical code. The code solves finite-difference approximation of the fluid dynamic governing equations (continuity, momentum and energy balance). The solution has been performed numerically by an integration both in space and time by means of the Arbitrarian Lagrangian Eulerian (ALE) technique. The numerical simulations have been carried out imposing steady and unsteady boundary conditions. The first ones allow to define the fluid dynamic losses and the airbox fluid dynamic behavior in order to identify an "optimum" design; the last ones, defined by means of a 1D code which takes into account the whole engine fluid dynamic scheme, contribute to describe the airbox behavior under more realistic operating conditions. The developed procedure has allowed to define the airbox geometry to be tested on race track. Tests show that there is a great improvement of car performances in comparison to the ones obtained with the unmodified airbox which originally equipped the car. Copyright © 2002 Society of Automotive Engineers, Inc.

In the racecar design process the definition of suspension type and geometry is an important stage. A good design of the main parameters, in terms of static and dynamic angles in bump and steer, is the basis of a successful racecar quite often. This paper aims at introducing the development of a new software tool, called MLKrace, that can analyse the suspensions kinematics for a wide range of different layouts. There are today a lot of commercial tools that analyse or simulate suspension behaviour. In general their application is restricted to the classic double wishbone suspension and in this case the calculation of the kinematics is not so difficult. This layout is used on both ends of the majority of formula and sports race cars but it isn't the only possible one. The MLKrace software is instead more suitable to analyse innovative suspension geometries, the mathematics being based on the resolution of the so-called Stewart platform, a method originally devised for parallel robot kinematics. Therefore full multilink or hybrid systems can be designed as easily as a double wishbone. In addition push rod, pull rod or outboard spring systems can be added and the driveshaft required float is computed. Multilink-McPherson hybrid suspensions can be designed as well. The flexibility is the great advantage of this new software. Apart from the mathematic model, a massive effort was devoted to the design of the Windows interface with the aim of making the designer's job particularly easy and effective compared to outdated MS-Dos interfaces of most of the existing software. The output is shown in the form of 2D and 3D animations, a large number of predefined diagrams, numeric tables and regression functions. Copyright © 2002 SAE International.

Despite massive research efforts carried out by racing car manufacturers aerodynamics is probably the most unexplored field in the design of high performance vehicles. Scale wind tunnel testing is still the most effective way for the development of a new car, CFD codes being at the experimental stage. Wind tunnel engineers produce what is called an "aero map": a simple graph expressing aerodynamic forces versus ride height. That means, drag, downforce, and relative distribution are measured on an array of front and rear different ride heights. The same concept can be applied to track testing with the use of proper sensors on the real vehicle, such as ground height laser sensors and suspension force transducers. Reading such a map and relating it to static and dynamic suspension characteristics is a vital task for performance optimisation. In the perfect world the centre of pressure would always be in the ideal position anywhere on the track, thus enabling the driver to make the most out of the car. As a matter of fact any unwanted, back and forth movement of the centre of pressure due to pitch and/or heave (e.g. under power, in braking, or on road bumps) affects cornering behaviour: the car can be perceived as difficult and tricky for the driver thus jeopardising performance. A module dedicated to non-linear aerodynamics (called "Aerolap") has been added to the RCS software for lap time simulation, working in close co-operation with the Minardi Formula 1 and BMS Scuderia Italia teams. The vehicle model can now take into account the effects of ride height variations on aerodynamic forces, as well as non-linear suspension and tire ground stiffness. The user can therefore simulate the impact of set-up modifications on aerodynamic balance along the track as well as on overall performance. The RCS project (presented at the 2000 SAE Motorsports Engineering Conference in Detroit) was conceived as a pit lane support tool for the race engineer, who usually works under pressure in a noisy, stressing environment were things happen -and decisions are taken- all very quickly. Therefore a particular effort was devoted to interface and graphics. Regarding the Aerolap an innovative method was devised for map visualisation as an alternative to the usual contour plot. This seems to enable a far more intuitive correlation with performance results. On the math side two different methods were used to approximate the aero map surface: a Gaussian array and the so-called Akima's triangles, the former giving more reliable results where extrapolation is required. Copyright © 2002 SAE International.

Deformability and buckling load of yacht in fibers reinforced plastic sandwich depend on the skins stacked sequence. In this work an optimization of the laminae fibers direction of a competition yacht existing design is proposed. This procedure has been divided into three parts (i.e. material characterization; surface model definition; lay-up optimization). First of all a set of unidirectional specimens has been realized, by using the same fibers and matrix (carbon/epoxy) used for the hull as well as the same procedure and workers, in order to characterize the material according to the ASTM D3039, employing strain gage technique. In the second part, by means of an original software in Turbo-Pascal (which uses the half-width value matrix as an input) linked to Pro/ENGINEER, has been possible to obtain the body plan and the surface and finite element models of the sailing yacht for the subsequent analyses. In the third step, an optimization procedure, that uses the results of FE structural analyses in three different navigation configurations, is performed, with the aim to obtain the fibers direction able to minimize the yacht deformability, taking in account buckling loads also. An approximated analytical model has been used in conjunction with a sweep technique in order to evaluate the best of the solutions.

Deformability and buckling load of yacht hulls with fiber reinforced plastic sandwich structure depend on the stack sequence of the skins. In this work an optimization of fiber directions of the laminae for a racing yacht is proposed. This procedure has been divided into three parts (i.e. material characterization, surface model definition, lay-up optimization). First of all a set of unidirectional specimens has been realized, by using the same fibers and matrix (carbon/epoxy) used for the hull as well as the same procedure and workers, in order to characterize the material according to American Society for Testing and Materials (ASTM) Standard D3039, employing strain gage technique. In the second part, by means of an original software in Turbo-Pascal (which uses the half-width value matrix as an input) linked to Pro/ENGINEER, it has been possible to obtain the body plan and surface and finite element (FE) models of the sailing yacht for the subsequent analyses. In the third step, an optimization procedure that uses the results of FE structural analyses in three different sailing configurations is performed, with the aim of obtaining the fiber directions that are able to minimize the yacht deformability, also taking into account the buckling loads. An approximate analytical model has been used in conjunction with a sweep technique in order to evaluate the best of the solutions.

In this study, the performances of two filter media, (Cellulose single layer and dual layered wool non wool/cellulose with electrically charged fibre) for automotive cabin air cleaning application, are investigated. Pressure drops of "clean" and dust loaded filter, fractional efficiencies and behaviour of dust loading were measured. The measurements were carried out in a panel filter housing like that specified by the Society of Automotive Engineers SAE J726 Air Cleaner Test Code. Dual-layered filter, as expected, has filtration efficiency and pressure drops very higher than single layer filter. The flow fields inside the test housing were, also, measured using a Pitot tube. The filter in the housing is exposed to non uniform velocity with very high velocities in the center and lower velocities toward the edge. These velocity variations may be expected to affect the performance of the filter, in terms of efficiency, pressure drops and dust holding capacity. Simple filter efficiency model based on single fibre inertial interception was applied in order to show the influence of non uniform velocities on the filter efficiency.

The evolution of computer aided design (CAD) systems and related technologies has promoted the development of software for the automatic configuration of mechanical systems. This occurred with the introduction of knowledge aided engineering (KAE) systems that enable computers to support the designer during the decision-making process. This paper presents a knowledge-based application that allows the designer to automatically compute and evaluate mass properties of racing cars. The system is constituted by two main components: the computing core, which determines the car model, and the graphic user interface, because of which the system may be used also by nonprogrammers. The computing core creates the model of the car based on a tree structure, which contains all car subsystems (e.g., suspension and chassis). Different part-subpart relationships define the tree model and link an object (e.g., suspension) to its components (e.g., wishbones and wheel). The definition of independent parameters (including design variables) and relationships definition allows the model to configure itself by evaluating all properties related to dimension, position, mass, etc. The graphic user interface allows the end user to interact with the car model by editing independent design parameters. It visualizes the main outputs of the model, which consist in numeric data (mass, center of mass of both the car and its subsystems) and graphic elements (car and subsystems 3D representation).

The dynamic behavior of radial lip seals is investigated experimentally. The experimental apparatus consists of a fixed housing, a radial lip seal, and an internal disk simulating the shaft. The excitation is provided by a shaker connected with a stinger to the seal's lip, and the measurement is performed using an accelerometer placed on the internal disk. In some experiments, the internal disk is removed to test the seal without internal constraints and deformations. In this case, the accelerometer is placed on the seal's lip. Results show a softening-type nonlinear behavior of the system.

The paper aims at introducing the developments of a performance simulation method for predicting the potential lap time of a given racing car on a given circuit. It is based on a previous work published in [1]. This first attempt produced fairly reliable results but it was not totally satisfactory since computation was very slow. It was then decided to restart from scratch with the following approach. Reference is made to the renowned «Milliken» [2]. The vehicle maximum G-G envelope is estimated. Then the model follows the «real» raceline -acquired with on-board instrumentation- performing within the G-G envelope. Accurate comparison with real-world data is used to identify and calibrate some of the model parameters. After calibration the model can be used to study the effect of different set-ups, aerodynamic balance, gear ratios etc. Where the circuit is new to the team a trajectory can be designed on a circuit map by using a built-in, parametric CAD-like interface. G-G envelope estimation prior to actual simulation has largely improved the computational speed. Also, the graphic interface aims at pit-lane use by the race engineer. The software is the product of a joint research between the University of Brescia and the team BMS Scuderia Italia therefore it is not available on the market. Copyright © 2000 Society of Automotive Engineers, Inc.

The design of mechanical assemblies carried out using today's CAD systems is mainly developed by modelling single parts, and then assembling them in a subsequent design phase. This bottom-up approach is not congruent and not satisfying the way designers are used to design assemblies. Besides, most of the CAD systems are weak for what concerns several functionalities. For example, the manipulation or the modification of the part geometry or the mating conditions of a created assembly is not supported. The introduction of the feature-based approach in assembly design, already successfully used in the design of single parts, would offer several advantages. For example, it would allow designers to start drawing the assembly from a top view, leaving the design of details and subsystems to a following phase. This paper describes some results of research work done within a project funded by the European Union aiming at extending and validating the use of features, to help in the solution of assembly problems in aeronautical applications. Copyright © 1999 Inderscience Enterprises Ltd.

Keywords: Assembly feature , Feature-based design , Knowledge formalization , Knowledge-based system

The dynamic behaviour of radial lip seals is experimentally investigated. The experimental apparatus consists of a fixed housing, a radial lip seal and an internal disk simulating the shaft; the excitation is given by a shaker connected with a stinger to the seal's lip and the measurement is performed by using an accelerometer placed on the internal disk. In some experiments the internal disk is removed to test the seal without internal constraints and deformations; in this case, the accelerometer is placed on the seal's lip. The radial lip seal is excited along a fixed direction at different temperatures and without lubrication. The frequency response functions (FRFs) have been measured by using different excitation signals and different assembly interferences between the seal's lip and the shaft; the stiffening effect of the garter spring has also been investigated. Experimental results show a softening-type nonlinear behaviour of the system.

One of the hidden aspects of the past Formula One season was the use of indoor road simulators as a mean of speeding up the springing and damping set-up over the race weekend. According to the rumours some teams can perform an indoor set-up optimization overnight by reproducing freshly acquired road profile data. The optimized set-up is then communicated back to the team and tested on-track the day after. The optimization is carried out on a so-called hydraulic four-post rig (or seven-post rig), where a car is shaken at such frequencies and amplitudes to reproduce the same inputs and forces encountered during a typical circuit lap. The Vehicle Dynamics Group of the University of Brescia has recently acquired a four-post rig by Servotest England. The paper aims to describe this facility while future papers will describe the first results obtained in research. Copyright © 1998 Society of Automotive Engineers, Inc.

The use of aluminium cast components as the uprights is as old as racing; nevertheless this traditional technology is still a standard on budget racing cars, where the advantages of a steel sheet, welded upright are simply not affordable. It is very well known that cast uprights allow for savings in the case of large production numbers (where "large" should be intended relatively to the racing world). The upright is the component which links the wheel and brake to the rest of the suspension. Being subjected to all the road loads and part of the unsprung mass, it is a fairly critical component. Any failure can lead to an accident; also, it must be as stiff and light as possible for better suspension performance hence roadholding. The paper describes the design of a small single-seater cast upright from the drafting phase to FEM computation to experimental testing. It is a case study rather than an innovative project, but it could be a reference for those involved in a similar design. Copyright © 1998 Society of Automotive Engineers, Inc.

The design of mechanical assemblies is mainly done after having modeled single parts. Most of the CAD systems are still weak for what concerns assembly. For example, they do not support the manipulation or the modification of the part geometry or the mating conditions once the assembly is made. The introduction of a feature-based approach in assembly design, successfully used in the design of single parts, would offer several advantages. This paper describes some results of the research work done within a project funded by the European Union aiming at extending the use of features, to help in the solution of assembly problems in the aeronautical applications.