Doctoral Dissertations

Date of Award

5-1991

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Engineering Science

Major Professor

Remi C. Engels

Committee Members

Kapaluru C. Reddy, Trevor H. Moulden, Basil N. Antar, John E. Caruthers

Abstract

A dynamic analysis technique for generic structural elements is presented. The modeling approach combines many aspects of the standard finite element method with a broader interpretation of the Craig/Bampton substructuring technique. The deterioration of the modal content of standard finite element models can be linked to the neglect of interface restrained assumed modes. Restoration of a few of these modes leads to higher accuracy with fewer generalized coordinates compared to the regular consistent mass matrix approach. Furthermore, since the proposed models possess the hierarchical property, no need exists for subdivision of basic elements such as rods, shafts and beams thereby simplifying the input data and allowing for different levels of approximation with little additional effort. The dynamic finite elements for the axial rod, the torsional shaft, the Bemoulli-Euler beam and the Timoshenko beam are derived in terms of static constraint modes and interface restrained normal modes. In addition, the equations for the Bernoulli-Euler beam and the Timoshenko beam elements are simplified using several types of interface restrained assumed modes. These dynamic finite element models can be easily incorporated into existing structual analysis software. Next, an element assembly process is presented, in which at each stage, the resulting component can be considered as a single larger element. A special algorithm, with good convergence properties, to solve the eigenvalue problem at each stage is developed. The manner in which the elements are modeled and assembled leads to a cost-effective solution of the structural eigenvalue problem. Various demonstration examples, including a large spatial truss, are implemented in order to evaluate the performance of the different dynamic finite element models.

Download
Files over 3MB may be slow to open. For best results, right-click and select "save as..."

Share

COinS