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A geometric nonlinear degenerated shell element using a mixed formulation with independently assumed strain fieldsA mixed formulation is chosen to overcome deficiencies of the standard displacement-based shell model. Element development is traced from the incremental variational principle on through to the final set of equilibrium equations. Particular attention is paid to developing specific guidelines for selecting the optimal set of strain parameters. A discussion of constraint index concepts and their predictive capability related to locking is included. Performance characteristics of the elements are assessed in a wide variety of linear and nonlinear plate/shell problems. Despite limiting the study to geometric nonlinear analysis, a substantial amount of additional insight concerning the finite element modeling of thin plate/shell structures is provided. For example, in nonlinear analysis, given the same mesh and load step size, mixed elements converge in fewer iterations than equivalent displacement-based models. It is also demonstrated that, in mixed formulations, lower order elements are preferred. Additionally, meshes used to obtain accurate linear solutions do not necessarily converge to the correct nonlinear solution. Finally, a new form of locking was identified associated with employing elements designed for biaxial bending in uniaxial bending applications.
Document ID
19920015850
Acquisition Source
Legacy CDMS
Document Type
Thesis/Dissertation
Authors
Graf, Wiley E.
(Akron Univ. Akron, OH, United States)
Date Acquired
September 6, 2013
Publication Date
December 1, 1991
Subject Category
Structural Mechanics
Report/Patent Number
NAS 1.26:189086
NASA-CR-189086
Accession Number
92N25093
Funding Number(s)
PROJECT: RTOP 505-63-5B
CONTRACT_GRANT: NAG3-307
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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