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10. An Efficient Dynamic Response Reconstruction Methodology Based on Model Condensation and Modal Decomposition.

Author

Fu, Zheng Yi, Adeagbo, Mujib Olamide, and Lam, Heung Fai

Subjects
*FINITE element method, *ERRORS-in-variables models, *CONDENSATION, *MEASUREMENT errors, *MODE shapes, *STRUCTURAL engineering
Abstract

The structural dynamic response reconstruction of large-scale civil engineering structures using traditional methods results in heavy computational burden with low efficiency. To improve efficiency, a novel time-domain response reconstruction method based on model condensation and modal decomposition is proposed in this paper. The finite element model of the target structure is transformed and condensed. The system matrices of the condensed model have lower dimensionality than those of the original finite element model. A checking procedure based on the modal assurance criterion is developed to ensure the accuracy of the condensed system. Measured dynamic responses are decomposed to time-domain modal responses at measured degrees of freedom (DOFs) using band-pass filters. The mode shape matrix of the condensed model is used to calculate the modal responses at the unmeasured DOFs. Following modal superposition and coordinate transformation, the dynamic responses at unmeasured DOFs are reconstructed without knowledge of the excitation. The accuracy and efficiency of the proposed methodology are verified in a numerical case study of a three-dimensional building frame model and an experimental case study of a two-story steel frame under laboratory conditions. In contrast with the numerical case study, the effects of modeling error and measurement noise are considered in the experiment verification. The results show the outstanding performance of the proposed methodology when compared with a traditional response reconstruction method. [ABSTRACT FROM AUTHOR]

Published
2024
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37. Grain refining performance of SHS Al-50TiC master alloys for commercially pure aluminum

Author

Yuan Run-zhang, Yan Youwei, and Fu Zheng-yi

Subjects
Equiaxed crystals, Materials science, Economies of agglomeration, Metallurgy, Composite number, Alloy, chemistry.chemical_element, engineering.material, Microstructure, Grain size, chemistry, Aluminium, engineering, General Materials Science, Refining (metallurgy)
Abstract

An Al-50wt% TiC composite was directly synthesized by self-propagating high-temperature synthesis (SHS) technology, and then was used as a grain refining master alloy for commercially pure aluminum. the microstructure and grain refining performance of the synthesized master alloy were emphatically investigated. The SHS master alloy only contained submicron TiC particles except for Al matrix. Moreover, TiC particles were relatively free of agglomeration. Grain refining tests show that adding only 0.1 wt% of the master alloys to the aluminum melt could transform the structure of the solidified samples from coarse columnar grains to fine equiaxed grains (average grain size 120 μm), and that this grain refining effectiveness could be maintained for almost 1. 5h at 1003 K. Therefore, it is concluded that the SHS master alloy is an effective grain refiner for aluminum and its alloys, and that it is highly resistant to the grain refining fading encountered with most grain refiners.

Published
2002
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