• 대한기계학회논문집A
• /
• 제32권4호
• /
• pp.319-326
• /
• 2008

In this study, we investigate the deformation behavior of F.C.C. single crystals containing micro- or submicron-sized voids by using three dimensional finite element methods. The locally homogeneous constitutive model for the rate-dependent crystal plasticity is integrated based on the backward Euler method and implemented into a finite element program (ABAQUS) by means of user-defined subroutine (UMAT). The unit cell analysis has been investigated to study the effect of stress triaxiality and crystallographic orientations on the growth and coalescence of voids in F.C.C. single crystals.

• Interaction and multiscale mechanics
• /
• 제1권4호
• /
• pp.449-465
• /
• 2008

In this paper a general approach for studying the motion of a cantilever beam interacting with a 2D fluid flow is presented. The fluid is solved by a general purpose commercial computational fluid dynamics (CFD) package (FLUENT 6.2), while the structure is managed by means of a dedicated finite element method solver, coded in FLUENT as a user-defined function (UDF). A weak fluid structure interaction coupling scheme is adopted exchanging information at the end of each time step. An arbitrary cantilever beam can be introduced in the CFD mesh with its wetted boundaries specified; the cantilever can also interact with specified rigid and flexible walls through use of a non-linear contact algorithm. After a brief review of relevant scientific contributions, some test cases and application examples are presented.

• Structural Engineering and Mechanics
• /
• 제66권4호
• /
• pp.487-494
• /
• 2018

The purpose of the present paper is to study the bending and free vibration of Functionally Graded Material (FGM) plate using user-defined material subroutine on the finite element software ABAQUS. The FGM plate is simply supported and subjected to sinusoidal and uniform load. The Poisson's ratio is kept constant. The results obtained compared to those available in the literature show the convergence, the exactitude and the efficiency of the method used with various power index of the materials.

• 융복합기술연구소 논문집
• /
• 제4권2호
• /
• pp.1-9
• /
• 2014

This paper examines feature-based reconstruction algorithm using feature-based modeling and based on topology optimization technology, which aims to achieve a minimal volume weight and to satisfy user-defined constraints such as stress, deformation related conditions. The finite element model after topology optimization allows us to remove some region of a solid model for predefined volume requirement. The stress or deformation distribution resulted from finite element analysis enables us to add some material to the solid model for a robust structure. For this purpose, we propose a feature-based redesign algorithm which inserts negative features to the solid model for material removal and positive features for material addition, and we introduce a bisection method which searches an optimal structure by iteratively applying the feature-based redesign algorithm. Several examples are considered to illustrate the proposed algorithms and to demonstrate the effectiveness of the present approach.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1997년도 추계학술대회 논문집
• /
• pp.596-599
• /
• 1997

In this study, the flow control system with shape memory alloy in jet engine inlet was suggested to adjust the shock boundary layer interact~on for supersonic flight system. It consisted of the flap with shape memory alloy, spar with steel, and fixing device with aluminum alloy. The advantages of itself are a simple configuration, a passive air circulation by using the flap deflection due to pressure difference, and no need to be required the auxiliary devices. Finite element analysis was conducted to predict the thenno-mechanical behavlor of the flap system with shape memory alloy. The user-defined subroutine UMAT was implemented with ABAQUS to accon~modate the thermo-mechanical constitutive relation of shape memory alloy.

• 한국HCI학회논문지
• /
• 제12권4호
• /
• pp.57-64
• /
• 2017

사용자 중심의 디자인 패러다임 변화와 사용자 경험 디자인의 부상으로 특정 공간에서의 제품과 서비스에 대한 사용자 경험의 중요성도 증대되었다. 또한 IoT서비스의 등장과 함께 미래 업무환경의 새로운 변화가 예상된다. 본 연구는 미래 업무공간의 컨텍스트를 고려하여 새로운 사용자 경험 디자인을 제안하는 것을 목적으로 한다. 우선 IoT의 개념과 본질에 대한 고찰을 통해 미래 업무환경에 영향을 줄 수 있는 다양한 요소들을 정의하고 각 요소들의 관계를 파악하였다. 다음으로 현재 업무환경에서의 사용자리서치를 통해 다양한 형태의 업무환경에서 사용자의 행태에 영향을 미치는 컨텍스트를 파악하고, 이를 통해 미래 업무환경에서의 새로운 사용자 경험의 가능성을 보여줄 수 있는 인사이트(insight)를 도출하였다. 그리고 위의 분석과 인사이트를 바탕으로 새로운 미래의 업무환경에 대한 다양한 컨텍스트모델을 구성하고, 그에 따른 UX모델링을 통해 구체적인 UX시나리오와 대안을 제시하였다. 본 연구는 UX디자인의 관점을 디바이스 중심에서 공간과 컨텍스트 중심으로 확장시킴으로써, UX디자인 연구의 다양성에 기여할 것이며 공간디자인 분야와 서비스디자인 분야와의 협력적 연구 및 IoT서비스 관련분야와의 학제적 연구에 기여할 것이다.

• 대한전자공학회논문지SD
• /
• 제37권10호
• /
• pp.11-16
• /
• 2000

회로설계 엔지니어들이 쉽게 RF IC 설계에 사용할 수 있는 나선형 인덕터의 SPICE 모델을 개발하였다. 이 모델은 나선형 인덕터의 등가회로 소자 값들을 SPICE의 user-defined function 및 subcircuit 기능을 이용하여, 레이아웃 변수, 공정 변수, 실리콘 기판 변수로부터 정의하였다. 특히 인덕턴스는 임의의 회전에 대한 인덕턴스 Li 및 임의의 두 회전에 대한 상호 인덕턴스 Mij를 subcircuit으로 정의하여 전체 인덕턴스 값을 계산하였다. 모델의 정확성을 검증하기 위하여 CMOS 0.8${\mu}m$ 공정으로 제작된 나선형 인덕터의 측정 s-파라미터, 총 인덕턴스 및 quality-factor 결과를 시뮬레이션 데이터와 비교한 결과 일치함을 확인하였다. 본 논문에서 제시된 SPICE를 이용한 나선형 인덕턴스 모델은 scalable하며, 실리콘 기판의 영향등을 포함하기 때문에 레이아웃 최적화에 쉽게 사용할 수 있는 장점을 가진다.

• Structural Engineering and Mechanics
• /
• 제67권6호
• /
• pp.643-658
• /
• 2018

In this paper, we introduce a new framework for running the finite element (FE) packages inside an online Loop together with MATLAB. Contrary to the Hardware-in-the-Loop techniques (HiL), in the proposed Software-in-the-Loop framework (SiL), the FE package represents a simulation platform replicating the real system which can be out of access due to several strategic reasons, e.g., costs and accessibility. Practically, SiL for sophisticated structural design and multi-physical simulations provides a platform for preliminary tests before prototyping and mass production. This feature may reduce the new product's costs significantly and may add several flexibilities in implementing different instruments with the goal of shortlisting the most cost-effective ones before moving to real-time experiments for the civil and mechanical systems. The proposed SiL interconnection is not limited to ABAQUS as long as the host FE package is capable of executing user-defined commands in FORTRAN language. The focal point of this research is on using the compiled FORTRAN subroutine as a messenger between ABAQUS/CAE kernel and MATLAB Engine. In order to show the generality of the proposed scheme, the limitations of the available SiL schemes in the literature are addressed in this paper. Additionally, all technical details for establishing the connection between FEM and MATLAB are provided for the interested reader. Finally, two numerical sub-problems are defined for offline and online post-processing, i.e., offline optimization and closed-loop system performance analysis in control theory.

• 컴퓨터교육학회논문지
• /
• 제6권1호
• /
• pp.9-17
• /
• 2003

차세대 인터넷 표준 언어인 XML(eXtensible Markup Language)은 데이터(data)와 표현(presentation) 그리고 구조(structure)가 구분되기 때문에 어느 환경에서나 재사용성이나 재구성이 용이한 장점을 보이고 있다. 본 논문에서는 XML 문서를 가상교육 시스템(Virtual Education System)의 멀티미디어 컨텐츠로 범위를 제한하여 사용자 위주의 효율적인 검색 시스템을 구현한다. 본 시스템에서는 가상교육 표준안으로 제안되고 있는 SCORM(Sharable Content Object Reference Model)에서 정의한 SCO(Sharable Content Object)단위의 메타데이터를 기반으로 컨테츠를 설계하고 각 문서를 키워드, 엘리먼트, 애트리뷰트 단위로 색인한다. 또한 사용자 인터페이스에서 엘리먼트 검색화면을 구조적으로 구성해줌으로써 사용자가 DTD(Document Type Definition)에 대한 사전지식 없이도 검색이 가능하며, XML-QL로 재구성된 XML 문서의 형태와 XSL(eXtensible markup language Stylesheet Language)을 이용한 HTML 형태의 두 가지 결과화면을 제시함으로써 사용자 선택의 폭을 넓혀준다.

• Wind and Structures
• /
• 제10권1호
• /
• pp.61-82
• /
• 2007

This paper presents a novel finite element (FE) model for analyzing coupled flutter of long-span bridges using the commercial FE package ANSYS. This model utilizes a specific user-defined element Matrix27 in ANSYS to model the aeroelastic forces acting on the bridge, wherein the stiffness and damping matrices are expressed in terms of the reduced wind velocity and flutter derivatives. Making use of this FE model, damped complex eigenvalue analysis is carried out to determine the complex eigenvalues, of which the real part is the logarithm decay rate and the imaginary part is the damped vibration frequency. The condition for onset of flutter instability becomes that, at a certain wind velocity, the structural system incorporating fictitious Matrix27 elements has a complex eigenvalue with zero or near-zero real part, with the imaginary part of this eigenvalue being the flutter frequency. Case studies are provided to validate the developed procedure as well as to demonstrate the flutter analysis of cable-supported bridges using ANSYS. The proposed method enables the bridge designers and engineering practitioners to analyze flutter instability by using the commercial FE package ANSYS.