• 소성∙가공
• /
• 제3권1호
• /
• pp.84-96
• /
• 1994

Simulation of 3 dimensional large irregularly shaped stamping process by a dynamic approach, based on an explicit time integration scheme, has been shown to be highly efficient and robust in comparison to traditional, implicit, quasi-static ones. The objective of the work is to evaluate the results from explicit code in application to deep drawing of rectangular cup and stamping of automotive front fender, in which deformation, force, thickness distribution are calculated. The method of predicting spring back and formability by and explicit code are suggested and applied to the processes.

• 산업공학
• /
• 제13권3호
• /
• pp.339-347
• /
• 2000

The use of the Web-based Simulation Environment (WBSE) provides a strong influence on supply chain simulations. A virtual supply chain simulation is available to evaluate strategies for reducing response time to customers and for shrinking the finished goods inventory along its supply chain. This paper presents the basic concepts and definitions of Web-Based Global Supply Chain Management (WBGSCM) simulation system. It also discusses the advantages of supply chain simulation modules integration. A Time Synchronization Mechanism (TSM) called Phased Bucket Scheme (PBS) is introduced as an approach of the distributed simulation modules integration.

• Journal of Mechanical Science and Technology
• /
• 제18권3호
• /
• pp.460-470
• /
• 2004

A computational analysis of engineering problems with moving domain or/and boundary according to either Lagrangian or Eulerian approach may encounter inherent numerical difficulties, the extreme mesh distortion in the former and the material boundary indistinctness in the latter. In order to overcome such defects in classical numerical approaches, the ALE(arbitrary Lagrangian Eulerian) method is widely being adopted in which the finite element mesh moves with arbitrary velocity. This paper is concerned with the ALE finite element formulation, aiming at the dynamic response analysis of baffled fuel-storage container in yawing motion, for which the coupled time integration scheme, the remeshing and smoothing algorithm and the mesh velocity determination are addressed. Numerical simulation illustrating theoretical works is also presented.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 추계학술대회
• /
• pp.1286-1290
• /
• 2003

This paper presents a newly implemented parallel finite element procedure for contact-impact problems. Three sub-algorithms are includes in the proposed parallel contact-impact procedure, such as a parallel Belytschko-Lin-Tsay (BLT) shell element generation, a parallel explicit time integration scheme, and a parallel contact search algorithm based on the master slave slide-line algorithm. The underlying focus of the algorithms is on its effectiveness and efficiency for inclusion in future finite element systems on parallel computers. Throughout this research, a prototype code, named GT-PARADYN, is developed on the IBM SP2, a distributed-memory computer. Some numerical examples are provided to demonstrate the timing results of the procedure, discussing the accuracy and efficiency of the code.

• 한국정밀공학회지
• /
• 제12권10호
• /
• pp.149-156
• /
• 1995

This paper presents a method of detecting chatter vibration in end-mill process. The detecting system consists of an adaptive signal processing scheme which uses an autore- gressive time-series model and a neural network is proposed and is verified its effectiveness by using acceleration and cutting force signals recorded during slotting in end-mill operations. Expeerimental results indicate that the proposed system provides excellent detection when chatter is occured within the ranges of cutting conditions considered in this study and an effectiveness of the integration of signals is confirmed.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2003년도 The Fifth Asian Computational Fluid Dynamics Conference
• /
• pp.181-182
• /
• 2003

A preconditioned numerical method for gas-liquid to-phase flow is applied to solve cavitating flow. The present method employs a density based finite-difference method of dual time-stepping integration procedure and Roe's flux difference splitting approximation with MUSCL-TVD scheme. A homogeneous equilibrium cavitation model is used. The method permits simple treatment of the whole gas-liquid two-phase flow field including wave propagation, large density changes and incompressible flow characteristics at low Mach number. By this method, two-dimensional internal flows through a venturi tuve and decelerating cascades are computed and discussed.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2006년도 추계 학술대회논문집
• /
• pp.31-35
• /
• 2006

The delta-formulation of the Navier-Stokes equations has been popularly used in the aerodynamics area. Implicit algorithm can be easily implemented in that by using Taylor series expansion. This formulation is extended for an unsteady analysis by using a dual-time integration. In the meanwhile, the incompressible flows with heat transfers which occur in the area of thermo-hydraulics have been solved by a segregated algorithm such as the SIMPLE method, where each equation is discretised by using an under-relaxed deferred correction method and solved sequentially. In this study, the dual-time delta formulation is implemented in the segregated Navier-Stokes solver which is based on the collocated cell-centerd scheme with un unstructured mesh FVM. The pressure correction equation is derived by the SIMPLE method. From this study, it was found that the Euler dual-time method in the delta formulation can be combined with the SIMPLE method.

• 전력전자학회논문지
• /
• 제5권5호
• /
• pp.427-434
• /
• 2000

본 논문은 유도전동기의 직접벡터 제어 시스템에서 전동기가 기동 시 토크 충격없이 부드럽게 기동할 수 있는 기동기법을 제시한다. 정지모드에서는 고정자 전류만으로 고정자자속을 계산하는 방식을 사용하며, 기동 후 직접 벡터제어 모드에서는 프로그램어블 3-단계 저역필터로 고정자자속을 계산한다. 정지모드에서 직접벡터제어 모드로 변환 시 3-단계 저역필터의 시간지연으로 고정자 자속이 급격히 감소되어 토크 역시 갑자기 감소된다. 본 논문에서는 전동기가 기동 시 토크 충격을 방지하기 위한 고정자 자속의 피이드포워드 제어 기법을 제시하고, 시뮬레이션 및 실험을 통하여 이 기법의 타당성을 확인한다.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 2003년도 ICCAS
• /
• pp.260-263
• /
• 2003

This paper has developed the computer integration manufacturing system and Internet based tele-operations. The functions of CIMS include production planing, material requirement planning, work order generation, process control, quality control, shipping planning, warehouse and inventory management and material cost accounting.[1] In this paper focuses on the automatic warehouse control and inventory management by developing the information system as well as the Internet-based integration. The system overview is divided into three parts, the mechanical system, the computer and developed software to control and manage the information and the communication system. The mechanical system consists of the warehouse machine and forklift mobile robot controlled by programmable logic controller (PLC). The computer works on many functions such as control station interfaces with PLC, managing database and inventory, and Internet server to broadcast the inventory database to users via World Wide Web and monitoring the operation on web camera. Our scheme the inventory database can be checked easily anywhere and anytime when the users connect to the Internet. In this article, the lead-time and inventory level can be reduced therefore the holding cost and operating time is also decreased.

• 대한기계학회논문집
• /
• 제16권5호
• /
• pp.899-909
• /
• 1992

본 연구에서는 대수 미분 방정식을 풀기위한 새로운 방법을 소개한다. 본 작업에서는 Lagrange multiplier의 값이 사전에 주어졌다고 생각하여, 즉 대수 미분 방정식을 순수한 상미분 방정식으로 변환하여, 잘 알려진 시간 적분법을 적용한다. 또 정확한 Lagrange Multiplier값은 반복 계산법(iterative scheme)에 의하여 계산한 다. 시간 적분의 정확도와 제한 조건의 정확도는 모두 보장된다. 특히 제한 조건 의 경우, 위치, 속도 및 가속도의 제한 조건이 모두 만족된다. 또 정확한 Lagrange multiplier의 값을 계산 가속기법(acceleration technique)에 의하여 대단히 빨리 계 산한다. 독립 좌표를 구할 필요가 없으므로 거대한 행열을 decomposition하는 등의 복잡한 절차가 불필요하며 N-R 반복법 역시 불필요하다. 이러한 사항들 및 Jacobian 행열의 sparsity로 인하여 경제적인 계산이 가능하게 된다.