R.M. Lin

Improvement on the iterated IRS method for structural eigensolutions

Iterated improved reduced system (IIRS) technique is a model reduction (or condensation) method by repeatedly updating a transformation matrix. An improvement on this dynamic condensation technique is proposed in this paper to modify the iterative transformation matrix and achieve faster convergence. Meanwhile, connection between the present algorithm and the subspace iteration method (SIM) is demonstrated. A proof of the convergence property is also presented. Applications of the method to two numerical examples have demonstrated that the proposed method can obtain the lowest eigensolutions of structures more accurately and efficiently, as compared with the current IIRS.

A new eigensolution of structures via dynamic condensation

Dynamic condensation (or model reduction) is a commonly used algorithm to fast estimate some low eigenvalues and corresponding eigenvectors of structures by reducing the order of the original structural model to a smaller one. This paper proposes a new eigensolution technique via iterated dynamic condensation. The technique retains all the inertia terms associated with the removed degrees of freedom in an iterated form, which generates the reduced mass matrix similar to that obtained in the Guyan reduction method with a frequency-dependent perturbed term. The corresponding eigenvalues and eigenvectors of interest are obtained as those of the Guyan reduction method with perturbations by using an eigensensitivity-based iterative method. The effectiveness and accuracy of the proposed technique are numerically verified by using a steel frame and the GARTEUR structure.

Application of Taguchi Method to Identify Damage in Cantilever Beam

A robust damage identification technique is presented such that the location and severity of damages can be identified in presence of random errors in measured data as well as systematic errors in analytical model. In order to identify damage efficiently, the concept of design of experiment using orthogonal array is used for screening main effects of each parameter which corresponds to possible damage location in FE model. Then, Taguchi method, which has been widely used for robust design in industry, is applied to the optimization of the objective function, which is defined by the difference between measured and analytical modal data, by updating the parameters in analytical FE model in an iterative way. The numerical simulation of cantilever beam shows that various types of damages can be identified effectively with reasonable accuracy.Copyright