When a structure such as a vehicle body is subjected to collision, the kinetic energy is dissipated largely by plastic deformation. This may be accompanied with ductile tearing as a result of excessive plastic straining. This paper presents issues and several problems involving plastic deformations and ductile tearing. The work presented is largely experimental as theoretical analysis is challenging because of complexity of the problems. For example, one major difficulty is the assessment of tearing energy and an understanding of its possible interaction with other forms of plastic deformation. Except for one analysis of circular tube splitting we have not been able to establish theories as current knowledge is very limited in this respect. Another relevant work is by Wierzbicki and Thomas (1993) where the tearing energy appears to affect plastic deformation in the far region through a process of minimising total energy. Presented are the measurement of ductile tearing energy for in-plane (mode I) and out-of-plane (mode III) tearing, splitting of metal tubes of both square and circular sections, and cutting of a metal plate by a wedge. They represent possible approaches to this class of problems and show some interesting features embedded. In the examples presented, it turns out that the tearing energy sometimes contributes to only a small percentage of the total energy. However, the tearing process is important in ensururing the desired energy dissipation mechanisms, for example ensuring a mainly force plateau over a long stroke. On the other hand, friction can be a major energy dissipation, which leads to the following remark. We have seen that in the dynamic case, energy absorption performance is not necessarily better than their static counterpart as one might expect. On the contrary, it can be worse. This is a direct result of the large contribution which friction makes towards the total energy dissipation; and in the dynamic situation friction is smaller than in the static case. This point needs to be noted in the design and assessment of energy absorbing systems.
Energy absorption of metallic structures involving ductile tearing
Energieabsorption in metallischen Strukturen bei Auftreten von duktilem Reißen
International Journal of Vehicle Design ; 37 , 2/3 ; 224-251
2005
28 Seiten, 25 Bilder, 1 Tabelle, 21 Quellen
Article (Journal)
English
Verformungsbruch , Verformungsfähigkeit , Energieabsorption , Reißfestigkeit , Anwendung im Fahrzeugbau , Anwendung in der Wehrtechnik , Anwendung in der Luft- und Raumfahrt , kinetische Energie , Kollision , Fahrzeugsicherheit , Kraftfahrzeug , Karosserie , plastische Deformation , Duktilität , dynamisches Verhalten , statische Reibung , dynamische Reibung , Dissipation , Aufprallenergieabsorptionsvermögen
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