Accession Number : ADA329601

Title :   Research in Structural Dynamics

Descriptive Note : Final rept. 1 Mar 94-28 Feb 97

Corporate Author : GEORGIA INST OF TECH ATLANTA SCHOOL OF AEROSPACE ENGINEERING

Personal Author(s) : Hodges, D. ; Berdichevsky, V.

PDF Url : ADA329601

Report Date : 31 AUG 1997

Pagination or Media Count : 177

Abstract : This report addresses truncation in structural dynamics, energy thresholds in nonlinear vibration, dynamic potential of vibrating systems, and high temperature diffusional creep. Study of the dynamics of elastic structures is usually based on structural models with a few degrees of freedom. In this connection it is important to understand how these degrees of freedom should be chosen and how the neglected degrees of freedom affect the accuracy of the model. It is shown that there is an energy threshold beyond which the laws of statistical mechanics become valid, requiring the consideration of all degrees of freedom. For excitation which is moderate (but below this threshold) methods are presented which show how to capture the leading degrees of freedom and how to take into account the neglected modes. The value of the energy threshold is driven by the specifics of models used so that small changes in the model can strongly increase the value of the threshold. The dynamic potential makes use of an analogy between thermodynamical energy and structural vibration. The existence of the dynamical potential reduces the number of experimentally determined functions to one. It is shown, and confirmed experimentally, how this leads to simple relations between excitations and responses of nonlinear vibrating systems. Finally, a nonlinear theory of diffusional plasticity is presented.

Descriptors :   *THERMOMECHANICS, *CREEP, *STATISTICAL MECHANICS, VIBRATION, STRUCTURAL PROPERTIES, THRESHOLD EFFECTS, CHAOS, STRUCTURAL MECHANICS, ELASTIC PROPERTIES, GRAIN SIZE, DEGREES OF FREEDOM, PLASTIC PROPERTIES, POISSON DENSITY FUNCTIONS.

Subject Categories : Mechanics
      Thermodynamics
      Statistics and Probability

Distribution Statement : APPROVED FOR PUBLIC RELEASE