• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.03a
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• pp.217-221
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• 1997

In this study, 3D sheet metal forming analysis program is developed by explicit finite element method. In this program, analysis flow just follows the real engineering process to provide the user intuitive understanding and smooth contact alorithm improves the accuracy of stress prediction. The capability of this program are demonstrated by various examples.

• Journal of applied mathematics & informatics
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• v.27 no.3_4
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• pp.715-723
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• 2009

The aim of this paper is to present an explicit iteration method for finding a common fixed point of a finite family of strictly pseudocon-tractive mappings defined on q-uniformly smooth and uniformly convex Banach spaces.

• Journal of computational fluids engineering
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• v.15 no.4
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• pp.76-84
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• 2010

In order to analyze the periodic unsteady flow problem efficiently the partially implicit harmonic balance (PIHB) method was developed. Contrary to the existing harmonic balance method, this method handles the harmonic source term explicitly and deals with flux terms implicitly. This method has a good convergence in comparison with the full explicit harmonic method and it is easy to apply this method because there is no need to calculate the complicated flux Jacobian term by comparing with the full implicit harmonic method. With the multigrid method about the each harmonic it turns out that this method has a good convergence regardless of the number of harmonics. The oscillating flows over NACA0012 airfoil is considered to verify this method then the result correponsed to both the result of dual time stepping and explicit Runge-Kutta method.

• Journal of the Korean Society for Advanced Composite Structures
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• v.3 no.4
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• pp.1-9
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• 2012

Dynamic application lower mode response is of interest, however the higher modes of spatially discretized equations generally do not represent the real behavior. Some implicit algorithms, therefore, are introduced to filter out the high-frequency modes. The objective of this study is to introduce the P-method and PC ${\alpha}$-method to compare that with dissipation method and Newmark method through the stability analysis and numerical example. PC ${\alpha}$-method gives more accuracy than other methods because it based on the ${\alpha}$-method inherits the superior properties of the implicit ${\alpha}$-method. In finite element analysis, the PC ${\alpha}$-method is more useful than other methods because it is the explicit scheme and it achieve the second order accuracy and numerical damping simultaneously.

• Journal of the Korean Institute of Telematics and Electronics
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• v.20 no.6
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• pp.11-17
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• 1983

In this paper, the application of the explicit M.R.A.C. algorithms to the D.C. motor speed control using the microprocessor is studied. The adaptation algorithms are derived from the gradient method and the exponentially weighted least square [E.W.L.S.] method. In order to minimize the computational instability of the E.W.L.S. method, the adaptation algorithm of UDUt factorization method is developed, and because of the characteristics of the D.C. motor (dead-aone phenomenon) , the SM. gra-dient type algorithm is also improved from the gradient type algorithm. Computer simulations and experiments show that these algorithms adapt well to the rapid change of the reference input and the load.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.9
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• pp.74-81
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• 2002

Recently tube hydroforming has been widely applied to the automotive industries due to its several advantages over conventional methods. In this paper, attention is paid to comparison of an implicit and an explicit finite element method widely used for numerical simulation of a hydroforming process. For an explicit FEM, a huge amount of computational time is required because of the very small time increment to solve a quasi-static problem. Hence, when an explicit FEM is used fDr a hydroforming process, it is general to convert the real problem to a virtual problem with a different processing time and mass density by appropriate scaling factor. However it is difficult to figure out how large the scaling should be adopted enough to ignore the dynamic effects and maintain the desired accuracy. In this paper, the comparison of the results obtained from both methods focus on the accuracy of the predicted geometrical shape and the stress with various scaling factors which are applied to analyze hydroforming process of an automobile lower arm.

• Wind and Structures
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• v.20 no.3
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• pp.423-448
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• 2015

In this paper the unsteady fluid-structure interaction (FSI) problems with large structural displacement are solved by partitioned solution approaches in the arbitrary Lagrangian-Eulerian finite element framework. The incompressible Navier-Stokes equations are solved by the characteristic-based split (CBS) scheme. Both a rigid body and a geometrically nonlinear solid are considered as the structural models. The latter is solved by Newton-Raphson procedure. The equation governing the structural motion is advanced by Newmark-${\beta}$ method in time. The dynamic mesh is updated by using moving submesh approach that cooperates with the ortho-semi-torsional spring analogy method. A mass source term (MST) is introduced into the CBS scheme to satisfy geometric conservation law. Three partitioned coupling strategies are developed to take FSI into account, involving the explicit, implicit and semi-implicit schemes. The semi-implicit scheme is a mixture of the explicit and implicit coupling schemes due to the fluid projection splitting. In this scheme MST is renewed for interfacial elements. Fixed-point algorithm with Aitken's ${\Delta}^2$ method is carried out to couple different solvers within the implicit and semi-implicit schemes. Flow-induced vibrations of a bridge deck and a flexible cantilever behind an obstacle are analyzed to test the performance of the proposed methods. The overall numerical results agree well with the existing data, demonstrating the validity and applicability of the present approaches.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.7
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• pp.989-996
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• 2001

High-speed and low-speed flows are simulated numerically by flowfield-dependent mixed explicit-implicit (FDMEI) method. This algorithm depends on implicitness parameters of convection, diffusion, diffusion gradients, and source terms which are calculated from the changes of local Mach, Reynolds, Peclet, and Damkohler numbers between adjacent nodes. Convection phenomena or shock waves are resolved from Mach number-dependent implicitness parameters whereas diffusion or viscous actions are simulated by Reynolds number or Peclet number-dependent implicitness parameters. Fluctuation components of all variables are properly accommodated spatially and temporally in the FDMEI procedure. To illustrate, some benchmark example problems are presented for comparisons of the FDMEI results with other available data. These results appear to be encouraging and point toward the need for further investigations of the FDMEI theory.

• Kyungpook Mathematical Journal
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• v.62 no.4
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• pp.699-713
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• 2022

This paper proposes a hybrid successive over-relaxation iterative method for the numerical solution of a nonlinear diffusion in a one-dimensional porous medium. The considered mathematical model is discretized using a computational complexity reduction scheme called half-sweep finite differences. The local truncation error and the analysis of the stability of the scheme are discussed. The proposed iterative method, which uses explicit group technique and modified successive over-relaxation, is formulated systematically. This method improves the efficiency of obtaining the solution in terms of total iterations and program elapsed time. The accuracy of the proposed method, which is measured using the magnitude of absolute errors, is promising. Numerical convergence tests of the proposed method are also provided. Some numerical experiments are delivered using initial-boundary value problems to show the superiority of the proposed method against some existing numerical methods.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.1
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• pp.29-36
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• 2008

In this paper, the orbital forming analysis of an automotive hub bearing was studied to predict forming performances using the explicit finite element method. To find an efficient solution technique for the orbital forming, axisymmetric finite element models and 3D solid element models were solved and numerically compared. The time scaling and mass scaling techniques were introduced to reduce the excessive computational time caused by small element size in case of the explicit finite element method. It was found from the numerical simulations on the orbital forming that the axisymmetric element models showed the similar results to the 3D solid element models in forming loads whereas the deformations at the inner race of bearing were quite different. Finally the strains at the inner race of bearing and the forming forces to the peen were measured for the same product of the numerical model by test, and were compared with the 3D solid element results. It was founded that the test results were in good agreements with the numerical ones.