• 한국전산유체공학회:학술대회논문집
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• 2003.10a
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• pp.77-79
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• 2003

The stability of flows induced by a surface acoustic wave (SAW) propagating along the deformable walls in a confined parallel-plane microchannel or slab in the laminar flow regime is investigated. The governing equation which was derived by considering the nonlinear coupling between the deformable or waving interface and viscous fluids is linearized and then the problem is solved by a verified code based on the spectral method together with the associated interface and boundary conditions. The value of the critical Reynolds number was found to be near 1439 which is much smaller than the rigid-wall case: 5772 for conventional pressure-driven flows.

• Journal of Mechanical Science and Technology
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• v.15 no.8
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• pp.1079-1089
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• 2001

This paper proposes J and CTOD estimation schemes applied to fracture toughness testing, covering typical homogeneous and bi-material specimens. Recommendations are based on the plastic limit analysis (either slip line field or finite element limit analyses), assuming the rigid plastic material behavior. The main outcome of the present study is that the J and CTOD estimation schemes (both codified and non-codified), recommended for homogeneous specimens, can be equally used for bi-material specimens with interface cracks. The effect of yield strength mismatch in bi-material specimens on the J-integral CTOD is discussed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.11 s.170
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• pp.2078-2086
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• 1999

Fracture behaviors of an interface crack in a ductile layer sandwiched by rigid substrates are analyzed by finite element method. Several fracture mechanisms and the corresponding criteria are examined. And the crack growth behavior and fracture toughness are predicted. As the results, various crack growth procedures such as the crack jump to the other interface on the opposite side, the creation of a new crack far from the initial crack front, and the asymmetric relation of fracture toughness vs. mode mixity ($J_c$-$\Phi$) can be successfully explained.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.3 s.174
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• pp.685-690
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• 2000

This paper deals with the stress singularity induced at the interface corner between the viscoelastic thin film and the rigid substrate as the film absorbs moisture from the ambient environment. Th e time domain boundary element method is employed to investigate the behavior of interface stresses. The order of the free-edge singularity is obtained numerically for a given viscoelastic model. It is shown that the stress singularity factor is relaxed with time, while the order of the singularity increases with time for the viscoelastic model considered.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.557-562
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• 2004

For constructing virtual environment it is more natural to model object as deformable body than as rigid body. High accuracy of simulation of model and low-latency computational cost for real-time simulation should be guaranteed. We pre-compute Green function through finite element analysis of deformable body and it is possible to simulate deformation of body in real-time environment using Capacitance Matrix Algorithm. Also, the capacitance matrix algorithm enables to construct the haptic rendering which serves the reaction force through a haptic device. The Newmark scheme is used for the more realistic haptic rendering and dynamic simulation in real-time.

• Journal of Adhesion and Interface
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• v.3 no.1
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• pp.9-12
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• 2002

In this paper, N,N-m-phenyenedimaleimide (m-PDM), Polyamide Resin (PI) and Metallic dimethacrylate etc. influencing the heat resistance of anaerobic adhesive has been studied, an anaerobic adhesive composition capable of post-cure expansion and $230^{\circ}C$ temperature resistance comprising a multifunctional methacrylate and m-PDM capable of effectuating expansion upon post-cure has been developed. A homogeneous mixture of a monomer and m-PDM are subjected to a first cure heat stage (Room Temperature) wherein a rigid partially-cured plastic is formed and a post-cure heat stage ($150^{\circ}C$) to effectuate permanent expansion of cured adhesive composition.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2003.12a
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• pp.146-153
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• 2003

This paper deals with the stress singularity induced at the interface corner between the viscoelastic thin film and the rigid substrate subjected to the combined influence of temperature change and moisture absorption. A boundary element analysis is employed to investigate the behavior of interface stresses. The film is assumed to be thermorheologically simple. It is further assumed that moisture effects are analogous to thermal effects. Numerical results are presented for a given viscoelastic model, indicating the singular residual stresses induced during cooling down from the curing temperature, and how they can be altered by subsequent moisture absorption at room temperature.

• Journal of Mechanical Science and Technology
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• v.20 no.6
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• pp.882-895
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• 2006

Surface and interfacial waves in two superposed horizontal inviscid fluids of finite depths are studied. The flow is induced by translating a vertical rigid plate with a prescribed velocity. Analytical solutions that accurately predict the motion of the free surface and the interface are obtained by using a small-Froude-number approximation. Three different velocities of the plate are considered, while flows induced by any arbitrary motion of the plate can be easily analyzed by a linear superposition of the solutions obtained. It is shown that pinching of the upper layer can occur for a sufficiently thin upper layer, which leads to its rupture into small segments. Other interesting phenomena, such as primary and secondary wiggles generated on the interface near the wavemaker, are discussed.

• Journal of the Society of Naval Architects of Korea
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• v.42 no.4 s.142
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• pp.330-340
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• 2005

Compressible two-phase flow is analyzed based on the arbitrary Lagrangian-Eulerian (ALE) formulation. For water, Tamman type stiffened equation of state is used. Numerical fluxes are calculated using the ALE two-phase Godunov scheme which assumes only that the speed of sound and pressure can be provided whenever density and internal energy are given. Effects of the approximations of a material interface speed are Investigated h method Is suggested to assign a rigid body boundary condition effectively To validate the developed code, several well-known problems are calculated and the results are compared with analytic or other numerical solutions including a single material Sod shock tube problem and a gas/water shock tube problem The code is applied to analyze the refraction and transmission of shock waves which are impacting on a water-gas interface from gas or water medium.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.859-865
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• 2007

This paper presents a method to analyze the unbalance response of a high speed polygon mirror scanner motor supported by sintered bearing and flexible supporting structures by using the finite element method and the mode superposition method. The appropriate finite element equations for polygon mirror are described by rotating annular sector element using Kirchhoff plate theory and von Karman non-linear strain, and its rigid body motion is also considered. The rotating components except for the polygon mirror are modeled by Timoshenko beam element including the gyroscopic effect. The flexible supporting structures are modeled by using a 4-node tetrahedron element and 4-node shell element with rotational degrees of freedom. Finite element equations of each component of the polygon mirror scanner motor and the flexible supporting structures are consistently derived by satisfying the geometric compatibility in the internal boundary between each component. The rigid link constraints are also imposed at the interface area between sleeve and sintered bearing to describe the physical motion at this interface. A global matrix equation obtained by assembling the finite element equations of each substructure is transformed to a state-space matrix-vector equation, and both damped natural frequencies and modal damping ratios are calculated by solving the associated eigenvalue problem by using the restarted Arnoldi iteration method. Unbalance responses in time and frequency domain are performed by superposing the eigenvalues and eigenvectors from the free vibration analysis. The validity of the proposed method is verified by comparing the simulated unbalance response with the experimental results. This research also shows that the flexibility of supporting structures plays an important role in determining the unbalance response of the polygon mirror scanner motor.