• Transactions of the Korean Society of Mechanical Engineers
• /
• v.18 no.7
• /
• pp.1738-1750
• /
• 1994

Both cylindrical cup drawing and square cup drawing are analyzed using membrane analysis as well as shell analysis by the elastic-plastic finite element method. An incremental formulation incorporating the effect of large deformation and normal anisotropy is used for the analysis of elastic-plastic non-steady deformation. The computed results are compared with the existing experimental results to show the validity of the analysis. Comparisons are made in the punch load and distribution of thickness strain between the membrane analysis and the shell analysis for both cylindrical and square cup drawing processes. In punch load, both analyses show very little difference and also show generally good agreement with the experiment. For the cylindrical cup deep drawing, the computed thickness strain of a membrane analysis, however, shows a wide difference with the experiment. In the shell analysis, the thickness strain shows good agrement with the experiment. For the square cup deep drawing, both membrane and shell analyses show a wide difference with experiment, this may be attributable to the ignorance of the shear deformation. Concludingly, it has been shown that the membrane approach shows a limitation for the deep drawing process in which the effect of bending is not negligible and more exact information on the thickness strain distribution is required.

• Proceedings of the Korean Operations and Management Science Society Conference
• /
• 2006.05a
• /
• pp.1788-1792
• /
• 2006

The ordered weighted averaging (OWA) operator by Yager has received more and more attention since its appearance. One key point in the OWA operator is to determine its associated weights. Among numerous methods that have appeared in the literature, we notice the maximum entropy OWA (MEOWA) weights that are determined by taking into account two appealing measures characterizing the OWA weights. Instead of maximizing the entropy in the formulation for determining the MEOWA weights, the new method in the article tries to obtain the OWA weights which are evenly spread out around equal weights as much as possible while strictly satisfying the orness value provided in the program. This consideration leads to the least squared OWA (LSOWA) weighting method in which the program tries to obtain the weights that minimize the sum of deviations from the equal weights since entropy is maximized when the weights are equal. Above all, the LSOWA weights display symmetric allocations of weights on the basis of equal weights. The positive or negative allocations of weights from the median as a basis depend on the magnitude of orness specified. Further interval LSOWA weights are constructed when a decision-maker specifies his or her value of orness in uncertain numerical bounds.

• Journal of computational fluids engineering
• /
• v.12 no.2
• /
• pp.21-25
• /
• 2007

A general purpose program NUFLEX has been extended for two-phase flows with topologically complex interface and cavitation flows with liquid-vapor phase change caused by large pressure drop. In analysis of two-phase flow, the phase interfaces are tracked by employing a LS(Level Set) method. Compared with the VOF(Volume-of-Fluid) method based on a non-smooth volume-fraction function, the LS method can calculate an interfacial curvature more accurately by using a smooth distance function. Also, it is quite straightforward to implement for 3-D irregular meshes compared with the VOF method requiring much more complicated geometric calculations. Also, the cavitation process is computed by including the effects of evaporation and condensation for bubble formation and collapse as well as turbulence in flows. The volume-faction and continuity equations are adapted for cavitation models with phase change. The LS and cavitation formulation are implemented into a general purpose program for 3-D flows and verified through several test problems.

• 한국전산유체공학회:학술대회논문집
• /
• 2008.10a
• /
• pp.33-41
• /
• 2008

This paper is an extension of previous study[9] on a development of a divergence-free element method using a hermite interpolated stream function. Divergence-free velocity bases defined on rectangles derived herein produce pointwise divergence-free flow fields. Hence the explicit imposition of continuity constraint is not necessary and the Galerkin finite element formulation for velocities does not involve the pressure. The divergence-free element of the previous study employed hermite serendipity cubic for interpolation of stream function, and it has been noted a possible discontinuity in variables along element interfaces. This deficiency can be removed by use of a hermite bicubic interpolated stream function, which requires at each element corners four degrees-of-freedom such as the unknown variable, its x- and y-derivatives and its cross derivative. Detailed derivations are presented for both solenoidal and irrotational bases from the hermite bicubic interpolated stream function. Numerical tests are performed on the lid-driven cavity flow, and results are compared with those from hermite serendipity cubics and a stabilized finite element method by Illinca et al[7].

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.2 no.2
• /
• pp.19-28
• /
• 1982

The development of unsteady, depth-averaged two dimensional sediment transport prediction model in estuaries and harbors by the Galerkin finite element technique is presented. The model consists of two submodels, flow induced circulation model and sediment transport model. The sediment transport submodel is formulated by incorporating sediment continuity equation and sediment diffusion equation. Numerical experiments of the model, which were carried out in one dimensional channel under different conditions for circulation and sediment transport, show the adaptability of the formulation for predicting the migration of both cohesive and noncohesive sediments. The model was applied to Busan harbor to simulate circulation and sediment transport for simplified conditions. Of the results by the model the flow pattern are shown to be similar to observed data.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.22 no.9
• /
• pp.830-836
• /
• 2012

The NDIF method based on a sub-domain technique is introduced to extract highly accurate natural frequencies of arbitrarily shaped plates with the simply-supported boundary condition. The NDIF method, which was developed by the authors for the eigen-mode analysis of arbitrarily shaped plates with various boundary conditions, has the feature that it yields highly accurate natural frequencies thanks to its effective theoretical formulation, compared with other analytical methods or numerical methods(FEM and BEM). However, the NDIF method has the weak point that it can be applicable for only convex plates. It was revealed that the NDIF method offers very inaccurate natural frequencies or no solution for concave cavities. To overcome the weak point, the paper proposes the sub-domain method of dividing a concave plate into several convex domains. Finally, the validity of the proposed method is verified in various case studies, which indicate that natural frequencies obtained by the proposed method are very accurate compared to the exact method and FEM(ANSYS).

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.21 no.11
• /
• pp.1538-1551
• /
• 1997

Kinetic energy conservation for fixed and moving grids is examined in time-accurate finite element computation of fully unsteady inviscid flows. As numerical algorithms, fractional step method (FSM) and modified SIMPLE are used. To simulate the flow in moving grid system, arbitrary Lagrangian-Eulerian (ALE) method is adopted. In the present study, the energy conserving time integration rule for finite element algorithm is proposed and discussed schematically. It is shown that the discretization by Crank-Nicolson in time and Galerkin (central difference) in space must be used to ensure energy conservation. The developed code has been tested for a standing vortex in fixed or moving grid system, sloshing in a tank and propagation of a solitary wave, and has been shown to be a completely energy conserving algorithm.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.19 no.8
• /
• pp.1950-1963
• /
• 1995

A modification of the approximate-factorization method is made to accelerate the convergency rate and to take sufficiently large Courant number without loss of accuracy. And a stable implicit finite-difference scheme for solving the incompressible Navier-Stokes equations employed above modified method is developed. In the present implicit scheme, the volume fluxes with contravariant velocity components and the pressure formulation in curvilinear coordinates is adopted. In order to satisfy the continuity condition completely and to remove spurious errors for the pressure, the Navier-Stokes equations are solved by a modified SMAC scheme using a staggered gird. The upstream-difference scheme such as the QUICK scheme is also employed to the right hand side. The implicit scheme is unconditionally stable and satisfies a diagonally dominant condition for scalar diagonal linear systems of implicit operator on the left hand side. Numerical results for some test calculations of the two-dimensional flow in a square cavity and over a backward-facing step are obtained using both usual approximate-factorization method and the modified one, and compared with each other. It is shown that the present scheme allows a sufficiently large Courant number of O(10$^{2}$) and reduces the computing time.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.23 no.11 s.170
• /
• pp.1993-2006
• /
• 1999

A Volume Integral Equation Method (VIEM) is applied for the effective analysis of elastic wave scattering problems and plane elastostatic problems in unbounded solids containing general anisotropic inclusions. It should be noted that this newly developed numerical method does not require the Green's function for anisotropic inclusions to solve this class of problems since only Green's function for the unbounded isotropic matrix is involved in their formulation for the analysis. This new method can also be applied to general two-dimensional elastodynamic and elastostatic problems with arbitrary shapes and number of anisotropic inclusions and voids. Through the analysis of plane elastodynamic and elastostatic problems in unbounded isotropic matrix with orthotropic inclusions and voids, it will be established that this new method is very accurate and effective for solving plane elastic problems in unbounded solids containing general anisotropic inclusions and voids.

• The Korean Journal of Food And Nutrition
• /
• v.27 no.4
• /
• pp.706-715
• /
• 2014

The purpose of this study was to determine the optimal mixing ratio of Alaska Pollack (Theragra chalcogramma) and olive oil in the preparation of sausage. The experiment was designed according to the central composite design for estimating the response surface, which demonstrated 10 experimental points including 2 replicates for Alaska Pollack and olive oil. The physical, mechanical and sensory properties of test materials were measured. A canonical form and perturbation plot showed the influence of each ingredient on the final product mixture. Measurement results of the physical and mechanical properties showed a significant increase or decrease in the following properties: dough sweetness (p<0.05); sausage L (p<0.05), a (p<0.001), and b (p<0.01); hardness (p<0.01), chewiness (p<0.05), and gumminess (p<0.01). Also, the sensory measurements showed a significant improvement in color (p<0.05), flavor (p<0.01), taste (p<0.001), tenderness (p<0.05), chewiness (p<0.01), mositness (p<0.05), and overall quality (p<0.01). As a result, the optimum formulation by numerical and graphical methods was calculated as Alaska Pollack 35.74 g and olive oil 7 g.