Papers by Author: Deokki Youn

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Authors: Usik Lee, Deokki Youn
Abstract: By using a continuum modeling approach based on the equivalent elliptical crack representation of a local damage and the strain energy equivalence principle, the effective elastic compliances and the effective engineering constants are derived in closed forms in terms of the virgin (undamaged) elastic properties and a scalar damage variable for damaged two- and threedimensional isotropic solids. It is shown that the effective Young’s modulus in the direction normal to the crack surfaces is always smaller than its intact value.
Authors: Usik Lee, Deokki Youn, Sang Kwon Lee
Abstract: A new continuum damage theory (CDT) has been proposed by Lee et al. (1997) based on the SEEP. The CDT has the apparent advantage over the other related theories because the complete constitutive law can be readily derived by simply replacing the virgin elastic stiffness with the effective orthotropic elastic stiffness obtained by using the proposed continuum damage theory. In this paper, the CDT is evaluated by comparing the mode shapes and natural frequencies of a square plate containing a small line-through crack with those of the same plate with a damaged site replaced with the effective orthotropic elastic stiffness computed by using the CDT.
Authors: Deokki Youn, Usik Lee, Oh Yang Kwon
Abstract: In this paper, an experimental verification has been conducted for a frequency response function (FRF)-based structural damage identification method (SDIM) proposed in the previous study [1]. The FRF-based SDIM requires the natural frequencies and mode shapes measured in the intact state and the FRF-data measured in the damaged state. Experiments are conducted for the cantilevered beam specimens with one and three slots. It is shown that the proposed FRF-based SDIM provides damage identification results that agree quite well with true damage state.
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