Unformatted text preview: degrees of freedom selected as MDOFs. However, for higher modes (modes
5-10), accurate eigenvalue prediction requires considerably more MDOFs. 7. The mode shape for mode 10 is not captured unless sufficient numbers of MDOFs are chosen. This is
due to the fact that the TOTAL option in this test case does not choose a uniformly distributed set of inANSYS Verification Manual . ANSYS Release 9.0 . 002114 . © SAS IP, Inc. 2–21 Benchmark C5
plane MDOFs, hence allowing for possible inaccurate in-plane mode representation at higher modes.
For SOLID45, 8P (or 80 MDOFs) are required to capture the tenth mode shape while 16P (or 160 MDOFs)
are required for SOLID92. In both cases roughly 7 to 8 percent of the degrees of freedom are required
as MDOF in order to capture the tenth mode.
8. Coincident frequencies (modes 5-6, modes 9-10) are predicted only for the following test cases
• 2–22 SOLID45 with all DOFs chosen as MDOF
SOLID92 with 50P DOFs chosen as MDOF. For cases with significantly reduced MDOF sets, the correct
coincident mode shapes are predicted but the frequencies are slightly different. ANSYS Verifica...
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- The Land, ........., Test Case