• 한국자동차공학회논문집
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• 제13권3호
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• pp.178-185
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• 2005

Crack tip displacement is originated by tensile stress component, s and shear stress component, t on pure Mode I and pure Mode II. The crack tip displacement(CTD) depends on combined types of different two stress components under mixed-mode loading conditions (MMLC). Thus, the analysis of crack tip displacement must be CTD vector, dv which is composition of ds and dt under MMLC. In this paper, various effects of MMLC on the crack closure are studied experimentally. The crack closure magnitude is calculated from the information of crack tip displacement under MMLC. This information has been obtained from the high resolution optical microscope in direct observations of crack displacement behavior at the crack tip. Observed crack tip displacement is analyzed by using CTD vector to determine crack opening load. The various effects of MMLC on the crack closure are explained using crack opening ratio with crack length and mode mixture. The effective stress intensity factor considering crack closure is also discussed.

• 한국지진공학회논문집
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• 제22권5호
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• pp.299-309
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• 2018

Now that problems with force-based seismic design have been clearly identified, design is inclined toward displacement-based methods. One such widely used method is Direct-Displacement-Based Design (DDBD). Yet, one of the shortcomings of DDBD is considering higher-mode amplification of story shear, moments, and displacements using equations obtained from limited parametric studies of regular planar frames. In this paper, a different approach to account for higher-mode effects is proposed. This approach determines the lateral secant stiffness of the building frames that fulfill the allowable inter-story drift without exceeding the desired story displacements. Using the stiffness, an elastic response spectrum analysis is carried out to determine elastic higher-mode force effects. These force effects are then combined with DDBD-obtained first-mode force effects using the appropriate modal superposition method so that design can be performed. The proposed design procedure is verified using Nonlinear Time History Analysis (NTHA) of twelve planar frames in four categories accounting for mass and stiffness irregularity along the height. In general, the NTHA response outputs compared well with the allowable limits of the performance objective. Thus, it fulfills the aim of minimizing the use of NTHA for planar frame buildings, thereby saving computational resources and effort.

• Structural Engineering and Mechanics
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• 제41권5호
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• pp.663-673
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• 2012

A number of mode shape-based structure damage identification methods have been verified by numerical simulations or experiments for on-line structure health monitoring (SHM). However, many of them need a baseline mode shape generated by the healthy structure serving as a reference to identify damages. Otherwise these methods can hardly perform well when multiple cracks conditions occur. So it is important to solve the problems above. By aid of the fractal dimension method (FD), Qiao and Wang proposed a generalized fractal dimension (GFD) to detect the delamination damage. As a modification of GFD, Qiao and Cao proposed the approximate waveform capacity dimension (AWCD) technique to simplify the calculation of fractal and overcome the false peak appearing in the high mode shapes. Based on their valued work, this paper combined and applied the AWCD method and curvature mode shape data to detect multiple damages in beam. In the end, the identification properties of the AWCD for multiple damages have been verified by groups of Monte Carlo simulations and experiments.

• International Journal of Ocean System Engineering
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• 제3권3호
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• pp.131-135
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• 2013

We construct the fundamental fields for 3-D arbitrarily shaped plane cracks in by differentiating with respect to a parameter of the crack. As an application of these fundamental fields, the total elastic energy release rate in combined mode cracking is computed.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.235-238
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• 2006

For high-speed aircraft and high-speed civil transport planes, certain structural skin components are subjected to very large acoustic loads in an elevated thermal environment. In this study, we used the single-mode Fokker-Panck distribution to predict displacements of isotropic plates subject to thermo-acoustic combined load. The single mode was formulated to predict the nonlinear dynamic responses of postbuckled plates under acoustic random excitation. Acoustic random excitation was used with Gauss distribution. Some important effects of the snap-through motion on the dynamic responses of the postbuckled plates are described.

• KIEE International Transactions on Electrophysics and Applications
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• 제2C권5호
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• pp.268-272
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• 2002

In this paper, we proposed a procedure to analyze a shielded-microstrip step discontinuity using the mode matching method (MMM) combined with the vector finite element method (VFEM), which is used to find the equivalent waveguide-model for a microstrip. In order to calculate the effective-widths and -dielectric permittivity of the equivalent waveguide-model corresponding shielded-microstrip, the propagation constant and characteristic impedance are calculated from the VFEM. MMM is then applied to find the scattering parameter in the planar waveguide. This technique makes it possible to take advantage of the high accuracy of the VFEM as well as the high efficiency of the MMM.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 C
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• pp.1817-1819
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• 2001

For an efficient calculation of scattering matrix of planar transmission line with step discontinuity. Mode Matching Method combined with Vector Finite Element Method is adopted. Calculating effective widths are replaced with their respective equivalent planar waveguide corresponding to the microstrip width, Propagation Constant is calculated from the Vector finite element. Mode matching method is used for deriving scattering parameters.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2003년도 추계학술대회
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• pp.186-194
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• 2003

This paper proposes a combined controller frame of the adaptive robust control(ARC) and the sliding mode control(SMC) for the trajectory tracking control of the excavator to preserve the advantages of the both methods while overcoming their drawbacks, namely, asymptotic stability of adaptive system fir parametric uncertainties and guaranteed transient performance of sliding mode control for both parametric uncertainties and external disturbance. The suggested control technique is applied for the tracking of a straight-line motion of end-effector of manipulators, and through computer simulations, its trajectory tracking performances and the robustness to payload variation and uncertainties are illustrated.

• 대한기계학회논문집A
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• 제23권11호
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• pp.2040-2049
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• 1999

The Rayleigh-Ritz method is used to investigate the natural frequencies and mode shapes of the ring stiffened cylindrical shells with a rectangular cutout. The cutout is located on the center of the shell. The Love's thin shell theory combined with the discrete stiffener theory is adopted to formulate the analytical model of the shell. The effect of stiffener eccentricity, number, and position on vibration characteristics of the shell is examined. Also the effect of cutout size is examined. By comparison with previously published analytical and new FEM results, it is shown that natural frequencies and mode shapes can be determined with adequate accuracy.

• 전자공학회논문지D
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• 제34D권4호
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• pp.87-93
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• 1997

An electro-optic polymer digital optical switch with a coupling region modified for optimum mode coupling is proposed, and it is analyzed by using the beam propagation method combined with the effective index method. Its modified coupling region is adiabatically introduced along the propagation direction from the branching point of the two waveguides. The structure of the modified coupling region and its refractive index profiles are designed to optimize the mode coupling in the Y-branch waveguide. Therefor, the switching performance of the device may be enhanced with a fixed device length. It is confirmed from the numerical calculation that the drive voltage is reduced by more than 30 percents and te crosstalk is improved by about 8dB.