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1、.Materials and Design 22 2001 251257 Icarus: the design process of a conceptual vehicle J.A.O. SimoesU Department of Mechanical Engineering, Uniersity of Aeiro, 3810-193 Aeiro, Portugal Received 2 May 2000; accepted 18 October 2000 Abstract The design and manufacturing of a conceptual prototype vehi

2、cle is described. The project was the result of a collaborative project between students from the University of Aveiro and designers of the School of Arts and Design of Matosinhos. The main objective of the project was to design a vehicle to participate for the design award of the French 1998 Shell

3、Eco-Marathon competition. The design process was essentially focussed on the integration of the aestheticism with the manufacturing of the vehicle. Icarus is a conceptual vehicle inspired on the wing concept, therefore the projects name is associated with the Greek mythological fi gure. The descript

4、ion of the project is presented focusing on the association of the materials chosen to manufacture composite complex geometry surfaces. Q 2001 Elsevier Science Ltd. All rights reserved. Keywords: Conceptual design; Product development; Prototype vehicle; Design education; Composite materials 1. Intr

5、oduction Material is something that is known to common people. And design? For different people, design can mean different things. Common people do not realise how the design process of a certain object can be materialised from idearconcept to the manufacturing of it. While some people associate des

6、ign to the aes- thetics of products, others, the word design means a project that integrates complementary different and related areas of knowledge. Design can be the process of converting an idea into information necessary to w xmanufacture a product 1 . For a mechanical engineer, design can be def

7、i ned as the application of scientifi c principles, technical information and imagination on the defi nition of a product system to perform pre-de- fi ned functions with maximum economy and effi ciency w x2 . The responsibility of the designer covers all the design process, from conception to produc

8、t instruc- UTel.: q351-234-370830; fax: q351-234-370953. .E-mail address: simoesmec.ua.pt J.A.O. Simoes . tions, and its interest maintains throughout the life w xexpectancy of the product 3 . Following Charles and Crane, design is a complex process aiming at the specifi cation of everything neces-

9、w xsary to make something 4 . The process can be charac- w xterised by four attributes 5 : function; aesthetics; man- ufacturing process; and cost. Three of these four essen- tial design features were considered in the design process of the conceptual vehicle, namely function, aesthetics and manufac

10、turing process. Due to the de- fi ned objectives to be achieved within the Icarus pro- ject, the cost parameter was not considered as a rele- vant parameter in the design process of the vehicle. Shell France has organised over the past few years a fueleconomycompetitioncalledtheShellEco- Marathon. T

11、he competitions objectives are to test ve- hicles conceived to minimise the consumption of fuel in common thermal motors and stimulate the research and development of prototype vehicles. Within the w xcompetition a design prize is awarded 3 . This award is essentially based on the integration of the

12、 designs aesthetics within the manufacturing process. Consis- 0261-3069r01r$ - see front matter Q 2001 Elsevier Science Ltd. All rights reserved. .PII: S 0 2 6 1 - 3 0 6 90 00 0 0 9 5 - 9 ()J.A.O. Simoes rMaterials and Design 22 2001 251257 252 tency and originality of the concept are important fact

13、ors to be considered. As for the bodywork, the front and rear aestheticism, the integration of functions and materials choice and exploitation are parameters anal- ysed. These vehicles are driven in a non-ergonomics position, and so drivers cockpit access and exit, the driving controls accessibility

14、, comfort, ventilation, road and instruments visibility are important design features to consider in the design process. The graphical com- munication of the project is also relevant and so atten- tion must be paid to the choice of basic colours, its harmony, graphics integration and quality of exec

15、ution. The internal, external fi nishing and quality execution are also important characteristics to bear in mind. These design selective parameters were taken into ac- count in the project. The Icarus project was developed by students of three departments of the University of Aveiro Depart- ment of

16、 Mechanical Engineering, Department of Elec- tronics and Telecommunications and Department of .Environmental Engineering and by designers from the School of Arts and Design of Matosinhos, who ide- alised the concept. Several aspects were carefully stud- ied, namely those intimately related to the co

17、nceptual design, manufacturing process and materials selection. Distinct goals where to be accomplished within the project: the design of a conceptual vehicle and the utilisation of the project for pedagogic teaching pur- poses. These type projects permit a more effectively learning basis of enginee

18、ring and design matters. Be- sides presenting an extra academic pedagogic value, it is easier to stimulate students to learn by doing it. The students also feel much more motivated when projects to be developed have well-defi ned objectives. Through- out the development of the project we experienced

19、 the dedication and enthusiasm of the students and the recognition that they have learned extra engineering skills such as materials science, structural mechanics, CADrCAM,electronics, telemetry, fl uid mechanics and design communication. The objective of this paper is to describe the devel- opment

20、of a conceptual vehicle, from conception to prototype manufacturing, which involved different de- signrengineering areas of knowledge. Fig. 1 shows the different design tasks idealised for the development of the vehicle. Only those related to the conceptual de- sign, materials selection and manufact

21、uring of the .chassisrbodyworkcockpit , which correspond to the grey zone, are described. 2. The conceptual design The Greek mythological story of Icarus and Daedalus is a universal well-known story. Within the story, the method used by Daedalus and son Icarus to escape from the labyrinth and theref

22、ore from King Minos is described. Idealised by father Daedalus, they built themselves wings by bonding feathers with wax, and attached them to their bodies and fl ew out of the labyrinth over the sea. Icarus, by fl ying too close to the sun, melted the wax fastenings and fell into the waters below.

23、Within the story, the wing was the element used to achieve an objective. The wing, as a concept, has always fascinated man throughout history and has been extensively studied by many investigators since Leo- Fig. 1. Identifi ed design areas. ()J.A.O. Simoes rMaterials and Design 22 2001 251257 253 .

24、Fig. 2. Wireframe computer model of the prototype vehicle Icarus . nardo da Vinci. He was the fi rst man to consider the possibility of fl ight from a technical point of view, by studying the fl ight of birds and their anatomy, and his notebooks contain many sketches showing designs for w x fl ying

25、machines, usually operated by fl apping wings 6 . As said elsewhere, the vehicle developed is a concep- tual one, based on the wing concept, which is intimately related to the aerodynamics principle of lift, which presupposes weight reduction and attrition to the soil when in movement. After previou

26、s studies and sketches drawn, the geometry of the vehicle was modelled using Studio V8.0 computer-aided design softwareAlias .Wavefront, Silicon Graphics . Fig. 2 shows a wireframe model of the vehicle and pilot. A computer image rendering a perspective of the vehicle and its ortho- graphic projecti

27、ons is shown in Figs. 3 and 4, respec- tively. Two models at a scale of 1:10 were machined from W. polyurethane Ureolmaterial to analyse the vehicles Fig. 3. Image rendering of Icarus. aesthetics and volumetric dimensions, which were then optimised based on the pilots ergonomic profi le Fig. .5 . A

28、model at a scale of 1:5 model was also manufac- tured for the aerodynamics study. The ergonomic study was done considering the pilots inherent physical char- .acteristics, mainly its height 1.65 m , and the non-ergo- nomic driving position. The optimal fi nal geometry was achieved based on studies c

29、oncerning the pilots ampli- . tude fi eld view visibility , driving posture and accessi- Fig. 4. Orthographic projections of the vehicle. ()J.A.O. Simoes rMaterials and Design 22 2001 251257 254 Fig. 5. Scaled 1:10 models of the vehicle and pilots driving position. .bility to the driving commands ha

30、nds and feet . For these studies, the pilots anthropometrical profi le was computer generated, as shown in Fig. 2 and Fig. 5, which allowed to minimise, as much as possible, the volumetric dimensions of the vehicle and therefore reduce the vehicles weight. The pilots visibility area was determined b

31、ased on the direct visibility control through an arc from ahead to 908 on either side of the vehicle. The models also allowed to correct the pilots leg position and feet, as well as to defi ne the location of the feet and hand commands. To improve the driving comfort, a customised er- gonomic seat w

32、as manufactured. For this purpose, the surface geometry of the seat was obtained in situ by placing the pilot inside the cockpit of the vehicle in the driving posture. The seat was hand modelled with liq- uid polyurethane that was then coated with an epoxy and covered with a fl exible foam and tissu

33、e. 3. Prototype vehicle manufacturing Materials play an important key role in the material- isation of an idea or concept, and are important in the design process. Nowadays, the choice of materials is almost unlimited, which is simultaneously bad and good news to designers. It is good news because o

34、ne can fi nd the suitable, even optimal, compromise of design parameters for a specifi c product; it is bad news be- cause the less effort to choose materials for a certain application has vanished. The selection of materials is an important aspect of the design process and should be, as much as pos

35、sible, a quantifi ed process. The necessity of selecting materials can be provoked by the design of a new product, by the necessity to introduce better characteristics of existing products or even to redesign a product that has failed in service by some reason. The selection is done preceded by the

36、products .function s defi nition and is carried-out interactively considering the potential manufacturing processes to transform the raw material into the fi nal form of the product. The organic shape of the vehicle limited our choices to a few conventional and advanced composite materi- als. In fac

37、t, the materials were an important choice parameter to correctly achieve the desired shape. The design process, as shown in Fig. 1, consisted on the concept defi nition, three-dimensional CAD modelling, ergonomic study, manufacturing of scale models, de- signand manufacturingof thechassis,bodywork .

38、cockpit , transmission driven train, braking system and steering system, engine modifi cations and adaptations, aerodynamics testing, electronics and telemetry imple- mentation. The chassis, an important structural ele- ment of the vehicle, could be manufactured either using composite materials or b

39、y a conventional welded tubular structure system. However, due to the geome- try shape of the vehicle, composite technology was used to manufacture the vehicle. The chassis and the cockpit structure were manufac- tured as an integrated structure using advanced com- posite materials moulded with CADr

40、CAM technology. Differentiated structural parts of vehicle were con- sidered based on its structural importance, and there- fore different moulds of these considered parts of the vehicle were manufactured. The strategy consisted on the fabrication of mould-modular parts machined from 3. low-density

41、100 kgrmpolyurethane foam material. The parts of the vehicle considered for the manufactur- ing of the moulds are shown in Fig. 6. Four moulds were manufactured, namely those for the chassis, cock- pit bodywork, front and rear covers. The surface of the pilots visibility area was moulded in an acryl

42、ic mate- rial. Due to the numerical controlled machine Mikron .VCE 500 with Fanuc controller limitations, the moulds were manufactured in several modular parts which where bonded to form the complete mould. The com- puter modelling data of the vehicle were converted and manipulated to generate the N

43、C machining strategies usingPowershaperPowermillCADrCAM software .Delcam plc., Birminghamand moulds machined. These were then covered with an epoxy resin rein- Fig. 6. Parts of the vehicle for mould manufacturing. ()J.A.O. Simoes rMaterials and Design 22 2001 251257 255 Fig. 7. Mould of the rear cov

44、er of the vehicle. forced with woven glass fabrics and coated with gel-coat for surface polishing. Fig. 7 shows the mould used to manufacture the rear cover of the vehicle. The chassis-cockpit was manufactured as an integral component using an advanced sandwich composite ma- terial to improved struc

45、tural integrity. A sandwich structure consisting of a foam core material combined with high strength skins was the solution encountered to manufacture the bodywork of the vehicle. The sand- wich structure was built with load bearing composite skins bonded to a core of very lightweight foam. Two diff

46、erent sandwich structures were manufactured for the cockpit and for the chassis. For the cockpit, the composite sandwich was composed of two skins of two 2. plies of woven carbon fabric 195 grmbonded to a W commercialPVCfoammaterialHerexC70.75, .Alusuisse Airex AG Speciality Foams of 6-mm thick- nes

47、s. For the chassis, the sandwich structure was identi- cal, with the exception to the core which had a 15-mm thickness and the skins were manufactured with unidi- rectional carbon fabric added between the woven car- bon fabrics to higher the fl exural rigidity. The foam used is a crossed-linked foam

48、 with rigid closed cell structure with high stiffness and strength to weight ratio and good compression strength and vibration re- w xsistance 7 . Table 1 shows the typical properties of the Table 1 Q .Properties of HerexC70.75 foam manufacturers data StandardUnitsC70.75 3 Aparent nominal densityISO

49、 8451 ASTM D1622kgrm80 2 Compressive strengthISO 8441 ASTM D1621Nrmm1.3 2 Compressive modulusDIN 534571 ASTM D1621Nrmm83 2 Tensile strengthDIN 53455NrmM1.95 2 Tensile modulusDIN 53457NrmM63 2 Shear strengthISO 19221 ASTM C273NrmM1.2 2 Shear modulusASTM C393Nrmm30 Shearing at breakISO 1922%30 2 Impac

50、t strengthDIN 53453kJrm0.9 Thermal conductivity at RTDIN526121 ASTM C177Wrm K0.025 Heat distortion temperatureDIN 534458C75 ()J.A.O. Simoes rMaterials and Design 22 2001 251257 256 Fig. 8. Integrated chassiscockpit sandwich composite structure. .foam used manufacturers data . These foam materials ar

51、e commercialised in scrim-cloth panels, therefore are easily adaptable to manufacture complex geometry sur- .faces. The chassis-bodyworkcockpit , constructed as an integrated sandwich structure is shown in Fig. 8. For the front and rear covers, a composite material of epoxy resin reinforced with wov

52、en carbon fabrics was manufactured to give the necessary stiffness. The two lateral wings of the vehicle were manufactured bonding woven carbon fi bre to a machined core which had the geometry of the wing. Table 2 shows the different composite sandwich structures manufactured for the chassis-cockpit

53、, rear and front covers of the vehicle. The roll-bar of the cockpit had to withstand a static w xload of 700 N imposed by regulations 8 , and so an in situ roll-bar was made of unidirectional carbon fi bre. Some ribs were also added to both sides of the cockpit to withstand possible lateral shocks.

54、Fig. 9 shows the Icarus vehicle in competition at the Paul Ricard circuit. 4. Conclusions Icarus was born in the computer laboratory of the Fig. 9. Icarus at the Paul Ricard circuit 1998 Shell Eco-Marathon . competition . School of Arts and Design of Matosinhos, where the conceptual design was trans

55、formed into computer mod- els based on performed ergonomic studies. At the workshop of the Department of Mechanical Engineer- ing of the University of Aveiro the virtual model was transformed into a prototype vehicle. The design process was developed considering the function and aesthetics of the ve

56、hicle, as well as the integration of selected materials with manufacturing capabilities. The sandwich structures manufactured showed to be an excellent material to manufacture resistant lightweight complex surface structures. As a pedagogic point of view, the project presented an extra-added teaching value because it allowed the students involved in the project a more practical learn- ing engineering basis, which sometimes is not possible to be given within the curricula of the engineering courses. To successfully materialise the objectives of the project, it was necessary to integrate dif