Crashworthiness of Aluminium Structures
Lightweight materials such as aluminium offer the automotive industry an opportunity to design and manufacture high-performance vehicles that are safe, energy-efficient and environmentally friendly, and much lighter than traditional designs. The introduct
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CRASHWORTHINESS OF ALUMINIUM STRUCTURES Professor Magnus Langseth and Arve GnJjnsund Hanssen, Dr. ing. Structural Impact Laboratory (SIMLab) Department of Structural Engineering Norwegian University of Science and Technology
1. INTRODUCTION Lightweight materials such as aluminium offer the automotive industry an opportunity to design and manufacture high-performance vehicles that are safe, energy-efficient and environmentally friendly, and much lighter than traditional designs. The introduction of these materials will challenge the automotive design engineers to explore and develop new solutions in design and production technology in order to fully realize the potential that can be gained in the interaction between these materials, productlstructural design and the manufacturing process. Even though aluminium is an "old" material, it is relatively new as a load-carrying material in the automotive industry. This implies that material producers and parts suppliers have to develop new knowledge about these materials to gain an increased market share. In a design process, computational mechanics is an indispensable too!. It enables new design concepts to be evaluated without extensive testing and provides a framework for combining new knowledge in the modeIling of materials and structures with experimental data on components and systems behaviour. However, in an efficient design process the designer must still possess knowledge about the physical mechanisms controlling the response, as weIl as have tools available for initial design studies. This will give guidelines to design solutions as weIl as what kind of simplifications that can be made in the numerical modelling of material and structural parts and still retain sufficient reliability and accuracy. In this part of the course we will try to provide basic knowledge related to energy absorption and crashworthiness of aluminium structures that is relevant to engineers in the auto motive industry. Focus is placed on material behaviour under static and dynamic loading conditions with special emphasis on plastic flow and tensile instabilities of thin-walled components. With regard to structural component behaviour, emphasis is placed on the behaviour of laterally and axially loaded members as weIl as the behaviour of aluminium foam and foam-filled components. Here, simple design methods are given relevant for thin-walled aluminium extrusions subjected to impact loading conditions. F. M. Mazzolani (ed.), Aluminium Structural Design © Springer-Verlag Wien 2003
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M. Langseth, A.G. Hanssen
2. MATERIAL BEHAVlOURAND MODELLING 2.1. 2.1.1.
Uniaxial behaviour True stress and true strain F,S
Fracture
ALore
0-2
0-1 1-2 2-3 So Su
2-3
Elastic behaviour, & =dcr/de=constant Elastic-plastic behaviour, & varies Localized deformation, necking Yield stress Ultimate stress
Figure 1: Stress-strain relationship A uniaxial test is mainly used to establish the relationship between load and extension (stress and strain). The basic information from such a test is the force, F, and
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