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Please use this identifier to cite or link to this item: http://hdl.handle.net/123456789/1530

Authors: Haimanote, Tadesse
Advisors: Dr A. Raman
Copyright: 2007
Date Added: 21-Oct-2008
Publisher: Addis Ababa University
Abstract: Having an accurate model is essential in analyzing systems under various excitations, boundary conditions and parameter changes. Unfortunately, the analytical model through different analytical methods deviates from the true model. This is seen in natural frequencies and mode shapes that are extracted from the test results which do not agree with the predicted values from the finite element analytical model. These errors result from various reasons, such as simplifying assumptions, imprecise boundary conditions etc. It should be noted that the test results themselves may contain errors resulting from use of low cost and less precise test setup but the test results has better accuracy than the analytical results if it is generated by a better experimental setup. Thus, the creation of an analytical model that takes into account the experimental results is becoming an interesting field of study. In this thesis an updating method of finite element analytical model using modal test results that has a relation with the existing error matrix method but with a better feature is presented, and the method can also be used to improve poor test setup by taking analytical results as true values. It is difficult to get the eigen vectors for the total degree of freedom of a complex structure from test because of the limitation of measuring instruments and structural complexity. So to solve this problem a method which is used to generate a test data for the unmeasured degree of freedoms from few test results is presented. This is applied for a class of problems where their lower modes are the predominant modes. Updating of the finite element analytical model is done by introducing diagonal system matrices ( DK,DM ) which when incorporated in to the analytical model will result in updated analytical model. The method of updating can also be equally applied for updating test set up by taking analytical results as true results, since the diagonal system matrices (correction matrices) can be physically realized and added to the experimental set up. The validation of the method is done based on two illustrative problems, using the code developed by MAT LAB software.
Description: A thesis submitted to the school of Graduate Studies of Addis Ababa University in partial fulfillment of the requirements of the Degree of Masters of Science in Mechanical Engineering (Applied Mechanics Stream).
URI: http://hdl.handle.net/123456789/1530
Appears in:Thesis - Mechanical Engineering

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