CONSTITUTIVE MODELING OF ALUMINUM FOAM AND FINITE ELEMENT IMPLEMENTATION FOR CRASH SIMULATIONS

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Bi, J. (2012). CONSTITUTIVE MODELING OF ALUMINUM FOAM AND FINITE ELEMENT IMPLEMENTATION FOR CRASH SIMULATIONS. Unc Charlotte Electronic Theses And Dissertations.
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Abstract

In the past decades metallic foams have been increasingly used as filler materials in crashworthiness applications due to their relatively low cost and high capacity of energy absorption. Due to the destructive nature of crashes, studies on the performance of metallic foams using physical testing have been limited to examining the crushing force histories and/or folding patterns that are insufficient for crashworthiness designs. For this reason, numerical simulations, particularly nonlinear finite element (FE) analyses, play an important role in designing crashworthy foam-filled structures. An effective and numerically stable model is needed for modeling metallic foams that are porous and encounter large nonlinear deformations in crashes.In this study a new constitutive model for metallic foams is developed to overcome the deficiency of existing models in commercial FE codes such as LS-DYNA. The new constitutive model accounts for volume changes under hydrostatic compression and combines the hydrostatic pressure and von Mises stress into one yield function. The change of the compressibility of the metallic foam is handled in the constitutive model by allowing for shape changes of the yield surface in the hydrostatic pressure-von Mises stress space. The backward Euler method is adopted to integrate the constitutive equations to achieve numerical accuracy and stability. The new foam model is verified and validated by existing experimental data before used in FE simulations of crushing of foam-filled columns that have square and hexagonal cross-sections.

Details
Author

Bi, Jing

Title

CONSTITUTIVE MODELING OF ALUMINUM FOAM AND FINITE ELEMENT IMPLEMENTATION FOR CRASH SIMULATIONS

Physical Description

1 online resource (143 pages) : PDF

Date

2012

Degree Granting Institution

University of North Carolina at Charlotte

Abstract

In the past decades metallic foams have been increasingly used as filler materials in crashworthiness applications due to their relatively low cost and high capacity of energy absorption. Due to the destructive nature of crashes, studies on the performance of metallic foams using physical testing have been limited to examining the crushing force histories and/or folding patterns that are insufficient for crashworthiness designs. For this reason, numerical simulations, particularly nonlinear finite element (FE) analyses, play an important role in designing crashworthy foam-filled structures. An effective and numerically stable model is needed for modeling metallic foams that are porous and encounter large nonlinear deformations in crashes.In this study a new constitutive model for metallic foams is developed to overcome the deficiency of existing models in commercial FE codes such as LS-DYNA. The new constitutive model accounts for volume changes under hydrostatic compression and combines the hydrostatic pressure and von Mises stress into one yield function. The change of the compressibility of the metallic foam is handled in the constitutive model by allowing for shape changes of the yield surface in the hydrostatic pressure-von Mises stress space. The backward Euler method is adopted to integrate the constitutive equations to achieve numerical accuracy and stability. The new foam model is verified and validated by existing experimental data before used in FE simulations of crushing of foam-filled columns that have square and hexagonal cross-sections.

Genre

doctoral dissertations

Subjects--Topics

Mechanical engineering
Engineering

Degree

Ph.D.

Keywords

Constitutive Modeling
Crash Simulation
Finite Element Analysis
Metallic Foam

Subject Area

Mechanical Engineering

Advisor(s)

Fang, Hongbing

Committee Members

Smelser, Ronald
Cherukuri, Harish
Weggel, David
Keanini, Russell
Chen, Don

Degree Note

Thesis (Ph.D.)--University of North Carolina at Charlotte, 2012.

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Rights Holder Information

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Identifier

Bi_uncc_0694D_10301

Permalink

http://hdl.handle.net/20.500.13093/etd:1149