Theses and Dissertations

Ali Najafi

Issuing Body

Mississippi State University

Advisor

Rais-Rohani, Masoud

Committee Member

Horstemayer, Mark F.

Committee Member

Newman, James C., Jr.

Committee Member

Lacy, Thomas E.

Date of Degree

8-8-2009

Document Type

Graduate Thesis - Open Access

Major

Aerospace Engineering

Degree Name

Master of Science

College

James Worth Bagley College of Engineering

Department

Department of Aerospace Engineering

Abstract

Nonlinear explicit finite element (FE) simulations are used to study the axial collapse behavior of multi-corner. single- and multi-cell crush tubes under quasi-static and dynamic loading conditions. It is shown that the higher hardening modulus and yield stress increases the crush force and its resulting energy absorption. Moreover, the multi-cell tubes are found to have complicated collapse modes because of the geometrical complexity of the corner region unlike single-cell tubes. it was also shown that the stress wave propagation has a significant effect on the formation of crush modes in the tubes without imperfections whereas this effect can be ignored in tubes with imperfection or trigger mechanism. An analytical formula for the prediction of mean crush force of multi-corner multi-cell tubes is derived based on the super folding element theory. The analytical predictions for the mean crush force are found to be in good agreement with the FE solutions. Results also show a strong correlation between the cross-sectional geometry and the crash behavior with the method of connecting the inner to the outer walls having large influence on the energy absorption.

URI

https://hdl.handle.net/11668/19362

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