Vehicle Collision Dynamics

Analysis and Reconstruction

Dario Vangi

• Publisher: Butterworth-Heinemann
• Year: 2020
• ISBN:
  9780128127513
• Topic: Technology & Engineering
• Subtopic: Automotive Transportation & Engineering
• Index: Technology & Engineering

Vehicle Collision Dynamics provides a unified framework and timely collection of up-to-date results on front crash, side crash and car to car crashes. The book is ideal as a reference, with an approach that's simple, clear, and easy to comprehend. As the mathematical and software-based modelling and analysis of vehicle crash scenarios have not been systematically investigated, this is an ideal source for further study. Numerous academic and industry studies have analyzed vehicle safety during physical crash scenarios, thus material responses during crashes serve as one of the most important performance indices for mechanical design problems.

In addition to mathematical methodologies, this book provides thorough coverage of computer simulations, software-based modeling, and an analysis of methods capable of providing more flexibility.

• Unifies existing and emerging concepts concerning vehicle crash dynamics
• Provides a series of latest results in mathematical-based modeling from front and oblique perspectives
• Contains almost everything needed to capture the essence of model development and analysis for vehicle crash
• Includes both numerical and simulation results given in each chapter
• Presents a comprehensive, up-to-date reference that encourages further study

Chapter 1

Structural behavior of the vehicle during the impact

Abstract

In this chapter, after a brief panoramic of the main feature of vehicle structures, focusing on crashworthiness, the phenomenological aspects of the crash are presented. The acceleration/time, velocity/time, and deformation/time curves acquired during a generic crash test are reported. The force–deformation characteristic curves well represent vehicle crash behavior. The main parameters influencing the force–deformation curves are also discussed, as the test speed, the crash configuration (offset, underride, etc.).

Keywords

Crashworthiness; crash behavior; vehicle structure

Chapter Outline

Outline

• 1.1 Crashworthiness structures and phenomenological aspects of the impact 1
• 1.2 Pulse acceleration curve 6
  • 1.2.1 Centroid time 9
• 1.3 Force–deformation curve 11
• 1.4 Distribution of the impact forces over time and space 14
• 1.5 Parameters of influence for the force–deformation curves 15
  • 1.5.1 Vehicle model 17
  • 1.5.2 Offset 17
  • 1.5.3 Oblique impact 21
  • 1.5.4 Underride/override 22
  • 1.5.5 Impact speed 24
• References 27

1.1 Crashworthiness structures and phenomenological aspects of the impact

The bodywork must offer the necessary resistance to static and dynamic stresses induced during the motion of the vehicle, to ensure an adequate flexural and torsional stiffness and to protect the occupants of the car in case of an accident.

The type of bodywork used by most of the vehicles in production is the monocoque (uni-body) of molded steel sheet (Fenton, 1999; Heisler, 2002). The bearing shell is constituted by a spatial structure composed of more subtle elements of complex shape, joined together through spot welding. These elements contribute through their stiffness to the structural behavior of the body. The floor pan is constituted by the longitudinal members, the plane sheets, the crosspieces, the wheel arches, and the eventual transmission tunnel. The side pillars and the upper pavilion are fixed on the floor pan; the pillars are named A, B, and C pillars, which define the shape of the bodywork.

In the event of a frontal or lateral collision, different structures of the monocoque are involved, as shown in Fig. 1.1.

Figure 1.1 Bodywork structure of the vehicle, with the highlighted parts that most absorb the impact energy in case of a frontal (left) and lateral impact (right).

In some vehicles, typically commercial vehicles, off-road vehicles, and some Sport Utility Vehicles (SUV) and Multi-Purpose Vehicles (MPVs), the body is made with a separate chassis, realized through longitudinal members (body on frame or ladder chassis). This type of chassis is constituted by a substantially planar structure, composed of two longitudinal elements (spars), connected by several transverse elements (crossbars), which is entrusted with the task of providing resistance to lateral forces and to conferring torsional stiffness (see Fig. 1.2).

Figure 1.2 Example of a frame consisting of two longitudinal members, on which the bodywork is mounted.

Recently, the construction of the body concerning the “space frame” (SF) geometry has been widespread, particularly indicated to be made of aluminum alloys. The SF is formed by a reticular structure consisting of a network of elements connected at the ends through rigid joints, typically made by casting, to form spatial geometries. Support functions of both the power train and chassis components are assigned to this spatial cage. Moreover, structural tasks to confer adequate stiffness to the vehicle and protect passengers in case of an accident are assigned to the spatial cage (Fig. 1.3).

Figure 1.3 Example of a vehicle body, realized with space frame geometry.

The core idea of crashworthiness structure design is to preset a crumple zone, which can absorb the kinetic energy of vehicles during crashes, possibly lowering the acceleration. In a frontal crash, for example, the stiffness of the front structure determines the acceleration pulse during a crash. This pulse should have a specific shape, ...