<p><strong>Abstract</strong></p> <p>The objective of this research is to develop an understanding of the mechanical behavior, failure and microstructure evolution of aluminum tubes under internal pressure loading, and to delineate the physical and mechanical origins of spatially-localized plastic deformation. Traditional approaches to the study of plastic instabilities, necking and failure have either been based on kinematic considerations, such as finite strain effects and geometric softening, or physics-based concepts. In this study, we develop a framework that combines both approaches to investigate the tube deformation and failure behavior at various loading conditions.</p> <p>A rate-dependent dislocation-based MTS model has been developed to study the tube hydro-forming process at high temperatures and at various strain rates. The development and application of the MTS model led to an advanced industrial application of PRF bottle forming, which has been fully investigated. This simulation shows a good agreement between experimental results and prediction. The model has been used extensively throughout the PRF bottle development, with several patent applications.</p> <p>The crystal plasticity based finite element model is selected to simulate surface roughening and localized necking in aluminum alloy tubes under internal pressure. The measured electron backscatter diffraction (EBSD) data are directly incorporated into the finite element model and the constitutive response at an integration point is described by the single crystal plasticity theory. The effects of the spatial grain orientation distribution, strain rate sensitivity, work hardening, and initial surface topography on surface roughening and necking are discussed. It is demonstrated that while localized necking is very sensitive to both the initial texture and its spatial orientation distribution, the initial surface topography has only a small influence on necking, but a large influence on surface roughness of the formed product.</p> <p>An elastic-viscoplastic based finite element model has been developed to study the necking behavior of tube expansion for rate dependent monolithic materials and laminated materials during dynamic loading. Numerical study shows that a high strain rate sensitivity can significantly delay the onset of necking for both monolithic and laminated sheets, and affect the multiple-neck formation in high speed dynamic loading. The model also shows that higher volume fractions of a clad layer with positive rate sensitivity material in laminated sheet could improve the sheet ductility as well.</p> <p>A commercial FE package, ABAQUS, is employed as a finite element method solver in this research work, and several user subroutines were developed to model various hydro-forming processes. Interfaces between the ABAQUS user subroutine UMAT and the ABAQUS main code are developed to allow further extension of the current method.</p> / Doctor of Philosophy (PhD)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/13201 |
| Date | 10 1900 |
| Creators | shi, yihai |
| Contributors | Wu, P.D., Mechanical Engineering |
| Source Sets | McMaster University |
| Detected Language | English |
| Type | thesis |
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