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Title: Finite element model updating by using natural frequency and mode shape sensitivities
Author: Ng, G. H. T.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1994
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Three finite element model updating approaches are considered in this thesis. In the first updating approach, a line search method is used in conjunction with the existing two level Gauss-Newton approach. This two level updating approach was used to tackle the problem of shape function discretization and enabled a coarse finite element model to be updated without discretization bias. The purpose of the line search method is to place the updated estimates, which are obtained at each iteration step of the Newton method, in a superior position for the next Newton iteration. Accordingly, convergence can be achieved with the use of line searching in some non-convergent problems. The effectiveness of this updating technique is illustrated by both simulated and experimental case studies. The second approach is concerned with reduction methods for use in finite element model updating. Particular attention is paid to the performance of dynamic condensation and modal truncation schemes. In both cases, subspace iteration and the efficient computation approaches which incorporate the skyline storage method are used in conjunction with the updating method. Moreover, an efficient method is proposed for the computation of eigenvector sensitivities in principal co-ordinates. Two simulated updating problems containing over one thousand degrees of freedom are examined for a variety of cases using different forms of sensitivity data. Another area of interest in the present thesis is the modelling and updating of adhesive, welded and bolted joints. In the case of the adhesive joint, two modelling approaches, referred to as the simplified 'element strip' model and the complex 'full joint' model are examined. For the updating of the welded joint, careful parameterization is found to be critical. The use of nodal offset dimensions is shown to result in an updated joint with physical meaning. When applied to the non-linear adhesive and bolted joints, model updating will produce equivalent linearized representations. The methods and their effectiveness for mechanical joint model updating are demonstrated by experimental case studies.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available