Improvements of Finite Element Solutions for Structural and Nonstructural Applications.
Final rept. Jul 69-May 71,
LIEGE UNIV (BELGIUM) LABORATOIRE DE TECHNIQUES AERONAUTIQUES ET SPATIALES
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The report presents a new formulation which allows the derivation of finite element properties in terms of stress functions. It is applicable to both displacement and equilibrium models and leads for certain classes of problems to a substantial reduction in the number of unknowns. The choice of the stress functions as unknowns is identified with an automatic selection procedure of redundancies of minimal diffusion. Therefore, this method can be interpreted as a force method in which the numerical search for the redundancies is avoided. It is shown to apply particularly well in certain nonstructural problems. Independently the effect of the introduction of internal degrees of freedom bubble functions in finite elements is evaluated. The conclusion is that a few of such modes can improve significantly the finite element properties and bring them partically in coincidence with assumed stress models. Author