The efficiency of using substructuring in the dynamic analysis of small models is examined by using a university version of ANSYS to perform a series of four case studies on a small, 648 degree of freedom model. The model is based upon the monocoque center section for an automotive space structure and was constructed using STTF 63 plate elements. In each case study, the model was divided into a different substructure configuration. In the configurations used, the model was divided into one, two, three and four substructures, respectively. In each case study, a series of modal analyses was performed for different master degree of freedom configurations. The first four eigenvalues and the CPU time needed to find a solution were compared. Based upon numerical experiments, it is shown that dynamic substructuring has a great potential for saving CPU time. Optimal substructured solutions which resulted in natural frequencies that agree with the frequencies of a non-substructured baseline solution within a tolerance of three to four significant digits could be found for an appreciable (17.49-70.16 CPU seconds) savings in CPU time. It is also demonstrated that the number of master degrees of freedom placed along the substructure boundaries has the strongest effect upon solution efficiency. Minimizing the number of boundary master degrees of freedom is shown to minimize the amount of CPU time needed to find a solution with a desired level of accuracy.

Library of Congress Subject Headings

Finite element method--Data processing--Case studies; Structural dynamics--Data processing--Case studies

Publication Date


Document Type


Department, Program, or Center

Mechanical Engineering (KGCOE)


Torok, Joseph


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