Finite element nonlinear transient response analysis of simple 2-d structures subjected to impulse or impact loads
Author(s)
Rodal, José J. A.; Witmer, Emmett A.
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This study was intended to contribute to the development of more
rational practical methods for predicting the transient responses of
structures which are subjected to transient and impact loads. Attention
is restricted to the global structural response; local (or stress-wave-
induced) response is not included. The use of higher-order assumed-
displacement finite elements (FE) is investigated to seek more efficient
and accurate strain predictions; these studies were carried out for 2-d
structural deformations typical of beams and curved rings to minimize
cost and labor. These studies were done in conjunction with the use of
various approximations to the nonlinear strain-displacement relations
since large deflections and rotations need to be taken into account.
Transient large-deflection elastic-plastic structural response
predictions are made for these various FE models for impulsively-loaded
beams and a free initially-circular ring, for which high quality experimental measurements of strains and deflections are available. From
comparisons of (a) predictions with each other for the various FE models
investigated and (b) predictions vs. experimental data, it appears to be
more efficient for the same number of degree-of-freedom (DOF) unknowns to
use the simple 4 DOF/node elements rather than fewer of the more sophisticated
8 DOF/node elements although the latter provide a physically superior and
more realistic distribution of strain along the structural span at any given
time instant compared with the use of the 4 DOF/N elements. Comparisons of
measured with predicted transient strain and final deformation of a thin
aluminum beam with both ends clamped and impacted at midspan by a 1-inch
diameter steel sphere show very good agreement.
Extensions to the present analysis to accommodate more general types
of fragments and fragment-impacted structures are discussed briefly.
Description
Originally presented as the first author's thesis, (M.S.) in the M.I.T. Dept. of Aeronautics and Astronautics
Date issued
1976Publisher
MIT Energy Lab
Other identifiers
04065249
Series/Report no.
MIT-EL76-004
Keywords
Finite element method, Structural dynamics, Transients (Dynamics), Girders
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