Kinematically admissible folding mechanisms for the progressive collapse of foam filled conical frusta
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Kinematically admissible folding mechanisms: for the progressive collapse of foam filled conical frusta Fan Yang . S. A. Meguid . A. M. S. Hamouda
Received: 31 October 2016 / Accepted: 30 December 2016 Springer Science+Business Media Dordrecht 2017
Abstract In this paper, the progressive collapse of foam filled conical frusta is investigated analytically using four different kinematically admissible folding mechanisms with varied straight folds. Comparisons are made between these four kinematically admissible mechanisms; specifically, pure inward folding, pure outward folding, first inward followed by outward folding, and first outward followed by inward folding. The instantaneous force as well as the mean crushing force was derived based on the principle of energy conversation, and the crushing energy was absorbed by the plastic deformation of the shell, the crushing of foam filler and the foam/shell interaction. The resulted upper bound solution of the four different mechanisms is compared with the finite element predictions of the same system. Our parametric study reveals that first outward then inward folding mechanism is generally energy favorable except for cases involving greater foam resistance, thin shell thickness, and/or large taper F. Yang School of Aerospace Engineering and Applied Mechanics, Tongji University, Shanghai, China S. A. Meguid (&) Mechanics and Aerospace Design Laboratory, University of Toronto, 5 King’s College Road, Toronto, ON M5S 3G8, Canada e-mail: [email protected] A. M. S. Hamouda Department of Mechanical and Industrial Engineering, Qatar University, Doha, Qatar
angle in which the pure outward folding mechanism may be preferable. Keywords Kinematically admissible mechanism Progressive collapse Foam filled Frusta
1 Introduction Currently, proper design of effective energy absorption system is still the major approach to protect the occupants from the damage caused by the high impact loads during the crash event of a transporting vehicle. Thin walled metallic structures are typically used as energy absorbers due to their weight and cost effectiveness, ease of fabrication and assembly, and high specific energy absorption (SEA). For example, thinwalled columns are used in the design of crash boxes in the automotive industry to connect the bumper to the side rails to effectively improve the crashworthiness (Li et al. 2009). Seats in the aircraft have also been redesigned by placing aluminium tubes over the seat rails (Desjardins 2006) to enhance their shock absorption capabilities. A number of studies have been conducted to investigate the collapse behavior and the energy absorption capacity of thin-walled columns. This includes the extensive experimental work contributed by Guillow et al. (2001), Hanssen et al. (2000a, b), Meguid et al. (2004a), among others. Extensive
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numerical efforts have also been made to determine the effect of each design parameter and expedite the design process. Finite element (FE) method (Ahmad and Thambiratnam 2009a, b;
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