The Automotive Body

The Automotive Body

Mechanical Engineering Series

Frederick F. Ling

Editor-in-Chief

The Mechanical Engineering Series features graduate texts and research monographs to

address the need for information in contemporary mechanical engineering, including

areas of concentration of applied mechanics, biomechanics, computational mechanics,

dynamical systems and control, energetics, mechanics of materials, processing, produc￾tion systems, thermal science, and tribology.

Advisory Board/Series Editors

Applied Mechanics F.A. Leckie

University of California,

Santa Barbara

D. Gross

Technical University of Darmstadt

Biomechanics V.C. Mow

Columbia University

Computational Mechanics H.T. Yang

University of California,

Santa Barbara

Dynamic Systems and

Control/Mechatronics

D. Bryant

University of Texas at Austin

Energetics J.R.Welty

University of Oregon, Eugene

Mechanics of Materials I. Finnie

University of California, Berkeley

Processing K.K. Wang

Cornell University

Production Systems G.-A. Klutke

Texas A&M University

Thermal Science A.E. Bergles

Rensselaer Polytechnic Institute

Tribology W.O. Winer

Georgia Institute of Technology

For other titles published in this series, go to

http://www.springer.com/1161

Lorenzo Morello • Lorenzo Rosti Rossini •

Giuseppe Pia • Andrea Tonoli

TheAutomotiveBody

Volume II: System Design

ABC

Lorenzo Morello

Via Bey 5B

10090 Villarbasse

Italy

E-mail: [email protected]

Lorenzo Rosti Rossini

via Canova 9

20145 Milan

Italy

E-mail: [email protected]

Giuseppe Pia

via Filadelfia 237/8 B

10137 Torino

Italy

E-mail: [email protected]

Andrea Tonoli

via Oronte Nota 55

10051 Avigliana (TO)

Italy

E-mail: [email protected]

ISSN 0941-5122

ISBN 978-94-007-0515-9 e-ISBN 978-94-007-0516-6

DOI 10.1007/978-94-007-0516-6

Springer Dordrecht Heidelberg London New York

The accuracy and completeness of information provided in this book are not guaranteed

to produce any particular results. Therefore, the Authors and the Publisher will not be

liable for any direct or indirect loss or damages incurred from any use of the information

contained in the book.

c Springer Science + Business Media B.V. 2011

No part of this work may be reproduced, stored in a retrieval system, or transmitted in

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system, for exclusive use by the purchaser of the work.

Cover design: eStudio Calamar S.L.

Printed on acid-free paper

Springer is part of Springer Science+Business Media (www.springer.com)

Contents

7 Introduction to Volume II .................................. 1

8 Functions and Specifications ................................ 3

8.1 Transportation Statistics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

8.1.1 Traffic Volume . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

8.1.2 Energy Consumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

8.1.3 Operating Fleet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

8.1.4 Infrastructures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

8.1.5 Social Impact . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

8.2 Vehicle Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

8.2.1 System Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

8.2.2 Functions Perceived by Customers . . . . . . . . . . . . . . . . . . . 39

8.2.3 Technical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

8.2.4 Body System Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

8.3 Requirements Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

8.3.1 Translation of Subjective Judgments into Measurable

Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

8.3.2 Euro NCAP Rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

8.3.3 Insurance Companies Rating . . . . . . . . . . . . . . . . . . . . . . . . 62

8.3.4 Aging Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

8.4 Regulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

8.4.1 The Vehicle in General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

8.4.2 Body Shape . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

8.4.3 Artificial External Lighting . . . . . . . . . . . . . . . . . . . . . . . . . 86

8.4.4 External Visibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

9 Ergonomics and Packaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127

9.1 Hints on Physiology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128

9.1.1 Backbone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

9.1.2 Joints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131

VI Contents

9.1.3 Effects of the Vibrations on the Comfort . . . . . . . . . . . . . 133

9.2 Manikins for Interior Packaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135

9.2.1 Hints about Anthropometry . . . . . . . . . . . . . . . . . . . . . . . . 135

9.2.2 Two-Dimensional Manikins . . . . . . . . . . . . . . . . . . . . . . . . . 140

9.2.3 Head Contour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142

9.2.4 Three-Dimensional Manikins . . . . . . . . . . . . . . . . . . . . . . . . 145

9.2.5 SAE Quotation System . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146

9.3 Hints of Occupants Positioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147

9.3.1 Basic Postures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148

9.3.2 Positions Adopted in Automotive Applications . . . . . . . . 151

9.3.3 Experimental Tools to Evaluate the Postural

Comfort . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154

9.4 Pedals Functionality and Positioning . . . . . . . . . . . . . . . . . . . . . . . . 155

9.4.1 Wheel Arch Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157

9.4.2 Pedals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158

9.5 Interior Packaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160

9.5.1 Front Row - Driver’s Position . . . . . . . . . . . . . . . . . . . . . . . 160

9.5.2 Steering Wheel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164

9.5.3 Seat and Steering Wheel Adjustment . . . . . . . . . . . . . . . . 165

9.5.4 Rear Rows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166

9.6 Seat Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167

9.6.1 Static Comfort . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168

9.6.2 Comfort under Dynamic Loads . . . . . . . . . . . . . . . . . . . . . . 171

9.7 Accessibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173

9.7.1 Getting in and Out . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173

9.7.2 Dimensional Parameters to Define the Apertures . . . . . . 176

9.8 Commands Reach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176

9.9 Loading and Unloading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180

9.10 Visibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180

9.10.1 Optical Properties of Glass Plates for Vehicle

Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183

9.10.2 Eyellipses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186

9.10.3 Direct Field of View and Binocular Obstruction . . . . . . . 193

9.10.4 Indirect Visibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199

10 Climatic Comfort . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201

10.1 Physiology Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201

10.1.1 Body Temperature Control . . . . . . . . . . . . . . . . . . . . . . . . . 202

10.1.2 Thermal Comfort Condition . . . . . . . . . . . . . . . . . . . . . . . . 204

10.1.3 Thermal Comfort Evaluation . . . . . . . . . . . . . . . . . . . . . . . 217

10.2 Passenger Compartment Energy Balance . . . . . . . . . . . . . . . . . . . . 221

10.2.1 Exchanged Heat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222

10.2.2 Radiated Heat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224

10.2.3 Passengers Metabolism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224

10.2.4 Powertrain Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224

10.2.5 Air Conditioning System . . . . . . . . . . . . . . . . . . . . . . . . . . . 224

Contents VII

10.3 HEVAC System Design and Testing. . . . . . . . . . . . . . . . . . . . . . . . . 226

10.3.1 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226

10.3.2 Cooling System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229

10.3.3 Heating System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231

10.3.4 Design Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231

10.3.5 Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236

11 Noise, Vibration, Harshness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239

11.1 Sensitivity to Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241

11.2 Sources of Noise and Vibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251

11.2.1 Road Surface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251

11.2.2 Wheel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264

11.2.3 Engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271

11.2.4 Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276

11.2.5 Brakes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281

11.2.6 Aerodynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 282

11.3 Dynamic Behavior of the Car Body and Modal Analysis . . . . . . . 284

11.3.1 Dynamic Equations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284

11.3.2 Free Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290

11.3.3 Modal Coordinates Transformation . . . . . . . . . . . . . . . . . . 292

11.3.4 Mode Shapes of a Car Body . . . . . . . . . . . . . . . . . . . . . . . . 295

11.3.5 Forced Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297

11.3.6 Response to a Random Excitation . . . . . . . . . . . . . . . . . . . 299

11.3.7 Viscous and Structural Damping . . . . . . . . . . . . . . . . . . . . 300

11.3.8 Model Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303

11.3.9 Cavity Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313

11.3.10 Radiation from the Panels . . . . . . . . . . . . . . . . . . . . . . . . . . 316

11.4 Engine Suspension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 318

11.4.1 Engine Suspension Mounts . . . . . . . . . . . . . . . . . . . . . . . . . 320

11.4.2 Role of the Damping in Engine Suspensions. . . . . . . . . . . 321

11.4.3 Engine Suspension Architectures . . . . . . . . . . . . . . . . . . . . 330

11.4.4 Location of the Attachment Points to the Car Body

Frame . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333

11.5 Acoustic Transmission and Insulation . . . . . . . . . . . . . . . . . . . . . . . 337

11.5.1 Transmission Loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337

11.5.2 Sound Barriers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 348

11.5.3 Sound Absorbing Materials . . . . . . . . . . . . . . . . . . . . . . . . . 350

11.5.4 Measurement of the Sound Absorption Coefficient . . . . . 360

11.5.5 Sound Absorption Treatments in Car Body

Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362

12 Structural Integrity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365

12.1 Internal and External Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366

12.1.1 Parking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367

12.1.2 Limit Maneuvers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 369

12.1.3 Road Unevenness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 371

VIII Contents

12.1.4 Internal Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 374

12.1.5 Safety Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377

12.2 Behavior of Thin Wall Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . 379

12.2.1 Hypothesis and Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 379

12.2.2 Bending . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 381

12.2.3 Torsion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 382

12.2.4 Shear and Bending . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 390

12.2.5 Buckling of Beams. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 400

12.2.6 Buckling of Flat Panels . . . . . . . . . . . . . . . . . . . . . . . . . . . . 402

12.2.7 Buckling of Composite Shapes . . . . . . . . . . . . . . . . . . . . . . 405

12.2.8 Buckling of Thin Wall Cylinders . . . . . . . . . . . . . . . . . . . . 408

12.2.9 Shear Buckling of Flat Panels . . . . . . . . . . . . . . . . . . . . . . . 410

12.3 Simplified Structural Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412

12.3.1 Box Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 418

12.3.2 Underbody Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . 422

12.3.3 Central Portion Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 436

12.3.4 Functional Requirements for a Structural Body . . . . . . . 436

12.4 Numerical Models for Structural Analysis . . . . . . . . . . . . . . . . . . . 439

12.4.1 Shape Functions and Degrees of Freedom . . . . . . . . . . . . . 440

12.4.2 Equations of the Motion . . . . . . . . . . . . . . . . . . . . . . . . . . . 441

12.4.3 Finite Elements Models of Car Body Structures . . . . . . . 446

12.5 Measurement of the Car Body Stiffness. . . . . . . . . . . . . . . . . . . . . . 455

12.5.1 Test Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 456

12.5.2 Vehicle Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 456

12.5.3 Bending Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 458

12.5.4 Torsional Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 458

12.5.5 Stiffness Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 458

13 Passive Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 463

13.1 Biomechanics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 463

13.1.1 Biomechanical Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . 463

13.1.2 Injury Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 471

13.2 Simplified Models for Crash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 485

13.2.1 Impulsive Model: With Full Overlap . . . . . . . . . . . . . . . . . 485

13.2.2 Role of the Restraint System. . . . . . . . . . . . . . . . . . . . . . . . 490

13.2.3 Speed-Time Diagrams. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 492

13.3 Introduction on Impact Energy Absorbers . . . . . . . . . . . . . . . . . . . 497

13.3.1 Beams with Rectangular Cross Section . . . . . . . . . . . . . . . 499

13.3.2 Stable Crush: Mechanics of the Deformation . . . . . . . . . . 503

13.3.3 Triggers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 511

13.3.4 Global Compression Instability of Beams . . . . . . . . . . . . . 514

13.3.5 Bending Instability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 514

13.3.6 Collapse of Tubes with Circular Cross Section . . . . . . . . . 519

13.3.7 Axial Collapse of Circular Tubes . . . . . . . . . . . . . . . . . . . . 522

13.3.8 Effects of the Strain Rate . . . . . . . . . . . . . . . . . . . . . . . . . . 527

13.3.9 Structural Foams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 528

Contents IX

13.4 Front Structure Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 531

13.4.1 Target Acceleration Profiles. . . . . . . . . . . . . . . . . . . . . . . . . 533

13.5 Testing on Vehicles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 539

13.5.1 Dummies for Impact Test . . . . . . . . . . . . . . . . . . . . . . . . . . 539

13.6 Impact Tests Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 547

13.6.1 Equipment for Tests on a Whole Vehicle . . . . . . . . . . . . . 547

13.6.2 Component Test: HYGE Slide . . . . . . . . . . . . . . . . . . . . . . 550

13.7 Non Linear FEM Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 551

13.7.1 Solution of Non Linear Static Problems . . . . . . . . . . . . . . 552

13.7.2 Characteristics of Non Linear Dynamic Problems . . . . . . 555

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 559

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 563

7

Introduction to Volume II

The purpose of Volume II is to explain the links which exist between satisfying

the needs of the customer (either driver or passenger) and the specifications for

vehicle design, and between the specifications for vehicle system and components.

For this study a complete vehicle system must be considered, including, ac￾cording to the nature of functions that will be discussed, more component classes

than considered in Volume I, and, sometimes, also part of the chassis and the

powertrain.

Since the first element of the chain of elements to be taken into consideration

is the human being, it is appropriate to consider physiology issues to some extent

in order to better understand the needs to be satisfied and the control parameters

to be evaluated.

The Chapter 8, the first in this Volume, is dedicated to body requirements and

functions. An introductory framework regarding statistic vehicle usage in Europe

is provided, followed by an analysis of vehicle functions, with particular refer￾ence to those functions that are more conditioned by body design: Ergonomics

and internal space utilization, thermal comfort, acoustic and vibration comfort,

structural integrity and passive safety.

Although specific aspects of marketing are beyond the scope of this text, some

examples are provided as a reference regarding the procedures applied to define

technical quantitative specifications on the basis of customer’s needs, usually

rated qualitatively. Bearing in mind their correlation with vehicle system speci￾fications, the European regulations relevant to the car body and its components

are also explained, with particular reference to vehicle active and passive safety.

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2 7 Introduction to Volume II

The following chapter, dedicated to Ergonomics and packaging, describes the

most important issues to be considered in terms of occupants well-being inside

passenger compartment: seating comfort, direct and indirect visibility, the space

necessary to install mechanical components into the vehicle will be particularly

considered. The analysis of these issues allows to the primary design criteria of

internal space and the lay-out of seats and controls to be identified.

Chapter 10 addresses the topic of thermal comfort and includes an introduc￾tion to the human body physiology thermal comfort conditions and the main

parameters of relevance; the metabolic activity is also examined as function of

ambient conditions and the influence on comfort, taking into account the thermal

exchange. A thermal balance can therefore be evaluated of relevance with respect

to the design of the air conditioning system. After summarizing the main compo￾nents of the HVAC system, already described in Volume I, the chapter concludes

with design and testing criteria description.

Starting from human sensitivity to noise and vibration, the main issues influ￾encing comfort are considered in the next chapter. The main sources of dynamic

excitation are examined, including those which generate noise and vibration in￾side the vehicle including tires and powertrain, and outside the vehicle such as

road shocks and aerodynamic noise. The main parameters needed to describe the

dynamic behavior of the body are also introduced, together with the technical

solutions proposed to reduce the transmission of excitations to the body.

The main objective of the following chapter concerning structural integrity

is to explain the role of the body primary components and the baseline criteria

for their design. Quasi-static reference loads acting on the body during normal

service life are introduced. Some additional concepts, appropriate to understand

the effect of bending and torsion deformation on a car body, are also discussed in

terms of the contribution of the framework. The chapter concludes by describing

the options available and the critical issues to be considered when modeling a

car body using the finite elements technique.

The last chapter is dedicated to the subject of passive safety, opening with

an introduction to biomechanics and the criteria used to evaluate the severity

of injuries consequent to an accident. This very broad topic is limited here to

empirical relationships and the acceptability limits proposed by governments reg￾ulations to limit the severity of injuries during accidents. The need to guarantee

a high level of protection to mitigate the consequence of accidents is a major

issue that directly conditions body design. The objective of the explanation in￾cluded is to describe the most common solutions and design criteria in use to

protect car occupants during an accident. Simplified mathematical models are

introduced to describe restraint systems functions and the structural behavior

of deformable parts of the body involved in the crash. The high reliability of

results obtained from finite elements method, also for the prediction of the large

displacements expected as a result of a crash, justifies the outline included of the

computer codes applied to model plastic behavior.

8

Functions and Specifications

Knowledge of how the vehicle is constructed and manufactured and of how its

components should be designed, which are the subjects of Volume I, and of how

they should be integrated into the system, the scope of Volume II, does not

complete the entire picture with regard to how to conceive and develop a car

which will meet with commercial success since in practice many of the functions

are not directly related to purely technical aspects.

Such knowledge is essential for obtaining a set of assigned targets for the

product. However the vehicle is a mature product meaning that fundamental

characteristics are almost always standardized and technical excellence is now

considered to be a ‘must’ than a topic for advertisement. Without underesti￾mating the fundamental importance of this knowledge and the resulting product

targets, it is appropriate to recognize that the success of a product is mostly

dependent on how well these targets are able to interpret the customer’s needs.

The combination of vehicle technical objectives and an overall description of

its architecture comprise what is universally known, with particular reference to

the case of the car, as product concept or conceptual design.

The concept is the starting point for the development of a car and its pro￾duction tools. It can be expressed with a sketch or by using a three dimensional

simplified model, suitable for illustrating its appearance and its main functions.

Its aesthetic appearance must also be addressed because it must be coherent

with the expectations of potential customers. This visual documentation must

be accompanied by an exhaustive quantitative definition of the technical and

economical characteristics which demonstrate congruence and feasibility.

Concept creation is a truly creative process, where its leadership is usually

assigned to a marketing specialist, but where meeting its target successfully must

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4 8 Functions and Specifications

include contributions from every discipline involved in product development. In

fact, the characteristics of the concept must be derived fromagood understand￾ing of customer needs and of how much the customer is willing to spend for their

satisfaction; even if it is true that this knowledge is the speciality of market￾ing experts, an innovative contribution essential for success is required from all

involved who are competent regarding relevant product functions.

Definingaconcept means, therefore:

• to describe a product in terms of technical functions and specifications;

• to determine the product configuration and to choose its main components;

• to identify character, personality, feelings and other traits this new product

will offer to the customer.

Each car manufacturer emphasizes different aspects of the product concept

and determines, consequently, its characteristics and potential success from the

outset of the development process. The most obvious aspects may be defined, for

example, according to the categories of convenience, luxury and sportsmanship.

The central issue of the concept definition process is to obtain involvement

throughout the company; the concept is partly driven by objective and measur￾able facts, the job of technicians, and partly by insight that will be contributed

by marketing experts and others involved with sufficient experience to contribute

creatively.

Those in charge of detailed product design, component specification, styling,

production means development, sales and service must also be involved since

their expertise will condition customer satisfaction.

Nevertheless, strong leadership by marketing experts is necessary: While ig￾noring the any of the operations listed above during the concept development

can cause significant inconvenience, it is also true that excessive involvement of

many can cause premature conflicts and compromises, leading to product char￾acteristics which may be ’flat’ or even trivial.

A new vehicle cannot be simply the extrapolation of a previous perception of

customer needs, as assessed by the popularity of existing products; very often,

successful cars have been born out of a response to needs that were unexpressed

until the time of product launch.

To underline this point, it is worthwhile recalling the first launch of sport util￾ity vehicles, coupe-cabriolets, minivans and a series of other product innovations

that met with commercial success which initially may have been unexpected by

other vehicle manufacturers.

When defining a new concept it is important to proceed according to the

following steps:

• Focus on customer needs;

• Identify latent or hidden needs, in addition to those demonstrated by ex￾isting products;