2004 Fiscal Year Final Research Report Summary
A Study on Expansion of Mode Shapes and Residual Stiffness for Structural Dynamics Modification
| Project/Area Number |
15560198
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Dynamics/Control
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| Research Institution | Wakayama University |
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Principal Investigator |
KURATANI Fumiyasu Wakayama University, Technology Education, Professor, 教育学部, 教授 (00294265)
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| Co-Investigator(Kenkyū-buntansha) |
SHIMADA Tetsuo Wakayama University, Design and Information Science, Professor, システム工学部, 教授 (20248165)
YAMANO Tadao Hyogo University of Teacher Education, Life Studies, Professor, 学校教育学部, 教授 (90304138)
OGAWA Takenori Hyogo University of Teacher Education, Integrated Studies, Professor, 学校教育学部, 教授 (80029264)
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| Project Period (FY) |
2003 – 2004
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| Keywords | Modal Analysis / Finite Element Method / Structural Dynamics Modification / Mode Shape Expansion / Plate Structure / Rib Stiffener / Condition Number / Boundary Condition |
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| Research Abstract |
For the experimental modal data based structural dynamics modification(SDM) method, mismatch in degrees of freedom between the model of the modified part and the measurement data, and also modal truncation are serious problems. In this study, the estimation methods for mode shapes and residual stiffness at the unmeasured points has been proposed and incorporated into the SDM procedure to settle the problems.
First, the estimation method for mode shapes at the unmeasured points has been developed using the mode shape expansion method and its accuracy was examined. The mode shapes at the unmeasured points are estimated with sufficient accuracy from the submodel with a free-free boundary condition. In addition, when the number of measurement points is insufficient, the accuracy of estimates decreases with increasing the number of modes combined. The proper number of modes to be combined can be determined by checking the rapid increase in the condition number of the modal matrix of the submodel.
Next, the estimation method for residual stiffness at the unmeasured points has been developed as an extension of the mode shape expansion method and its accuracy was examined. The developed method estimates the residual stiffness, though the accuracy of estimates of residual stiffness is lower than that of mode shapes.
Finally, the SDM procedure with the mode shape expansion method has been developed and the accuracy of predictions was examined. The modification of a thin plate structure with the L-shaped ribs was introduced as a practical example. The developed procedure produces the accurate predictions of the natural frequencies of the modified structure by the use of the estimated mode shapes at the unmeasured points even when the ribs are attached to the locations where mode shapes are not measured.
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Research Products
(4 results)
