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2003 ASME design engineering Technical Conferences and computers and Information in engineering Conference

作者： Choi, Kyung K. Dong, Jun Vlahopoulos, Nickolas Wang, Aimin Zhang, Weiguo Center for Computer-Aided Design Department of Mechanical Engineering University of Iowa Iowa City IA 52242 United States Dept. of Nav. Arch. Engineering University of Michigan Ann Arbor MI 48109 United States

A design sensitivity analysis of high frequency structural-acoustic problem is formulated and presented. The Energy Finite Element Method (EFEM) is used to predict the structural-acoustic responses in high frequency range, where the coupling between the structural and acoustic domain are modeled by using radiation efficiency. The continuum design sensitivity formulation is derived from the governing equation of EFEM and the discrete method is applied in the variation of the structural-acoustic coupling matrix. The direct differentiation and adjoint variable method are both developed for the sensitivity analysis, where the difficulty of the adjoint variable method is overcome by solving a transposed system equation. Parametric design variables such as panel thickness and material damping are considered for sensitivity analysis, and the numerical sensitivity results show excellent agreement comparing with the finite difference results.

关键词： Structural design

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Learning the methods and the skills of global product realization in an academic virtual enterprise

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European Journal of engineering Education 2003年第1期28卷 83-102页

作者： HORVÁTH, IMRE DUHOVNIK, JOŽE XIROUCHAKIS, PAUL Section of Computer Aided Design and Engineering Department of Design Engineering Faculty of Industrial Design Engineering Delft University of Technology Landbergstraat 15 Delft2628 CE Netherlands Faculty of Mechanical Engineering University of Ljubljana Slovenia École Polytechnique Fédérale Lausanne Institut de Production et Robotique Switzerland

This paper reports on and draws conclusions about the international course called European Global Product Realization. It was organized to provide university students with knowledge about distributed product development in virtual enterprises. The philosophy of the course is discussed together with its structure, contents, organization, infrastructure, deliverables and the experiences. Necessitated by globalization, the principles of operation of virtual enterprises were used in organizing the course. The knowledge accumulated in global product realization by the participating companies and academic sections provided the basis for the course and for the student projects. The organizers put the students of three European universities into the position of evolving young professionals who act as both knowledge producers and knowledge consumers. The design and engineering students took part in academic lectures and industrial case studies in a virtual classroom and practised collaborative product development in the emulated virtual enterprise. The academic virtual enterprise framework has been confirmed to be a solution for opening the conventional educational institutions. Our future work will concentrate on how to exploit disciplinary and operational research as the engine behind academic learning and teaching. © 2003, Copyright Taylor & Francis Group, LLC.

关键词： Students

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On probabilistic approaches for reliability-based design optimization (RBDO)

On probabilistic approaches for reliability-based design opt...

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9th AIAA/ISSMO Symposium on Multidisciplinary Analysis and Optimization 2002

作者： Choi, K.K. Youn, B.D. Center for Computer-Aided Design and Department of Mechanical and Industrial Engineering The University of Iowa Iowa City IA 52242 United States

ISBN: (纸本)9781624101205

During last decade, numerous endeavors have been made to develop effective reliability-based design optimization (RBDO) methods. Due to the fact that evaluation of probabilistic constraints defined in RBDO formulation is the most difficult part to deal with, a number of different probabilistic design approaches have been proposed to evaluate probabilistic constraints in RBDO. In the first approach, statistical moments are approximated to evaluate the probabilistic constraint. Thus it is referred to as approximate moment approach (AMA). The second approach, called reliability index approach (RIA), describes the probabilistic constraint as a reliability index. Lastly, the performance measure approach (PMA) was proposed by converting the probability measure to a performance measure. This paper presents a comparative study to find the most effective probabilistic design approach for RBDO from the perspective of various numerical considerations. It has been found in the literature that PMA is more efficient and stable than RIA in the RBDO process. This paper presents that PMA has several major advantages over AMA, in terms of numerical accuracy, simplicity, and stability. Some numerical examples are shown to demonstrate several numerical observations on three different RBDO approaches. © 2002 by the author(s). Published by the American Institute of Aeronautics and Astronautics, Inc.

关键词： Machine design

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Adaptive probability analysis using performance measure approach

Adaptive probability analysis using performance measure appr...

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9th AIAA/ISSMO Symposium on Multidisciplinary Analysis and Optimization 2002

作者： Youn, B.D. Choi, K.K. Center for Computer-Aided Design and Department of Mechanical and Industrial Engineering The University of Iowa Iowa City IA 52242 United States

ISBN: (纸本)9781624101205

This paper presents an adaptive probability analysis to identify the effect of input uncertainty. It was found in the literatures that existing probability analysis methods do not perform well in terms of numerical efficiency, accuracy, and/or robustness. These difficulties can be resolved by utilizing the performance measure approach (PMA) and accurately approximating the most probable point (MPP) locus that provides initial search points for the probability analysis process. The MPP locus approximation is studied by employing a least squares (LS) and a moving least squares (MLS) methods. The proposed probability analysis method adaptively adds more probability levels by using a posteriori-error estimator, such that an appropriate number of probability levels is adaptively decided while constructing probability function of output performance functions. The hybrid mean value (HMV) method is numerically implemented in the proposed adaptive probability analysis using performance measure approach (PMA). © 2002 by the author(s).

关键词： Uncertainty analysis

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An investigation of nonlinearity of reliability-based design optimization approaches

An investigation of nonlinearity of reliability-based design...

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作者： Choi, Kyung K. Youn, Byeng D. Center for Computer-Aided Design Department of Mechanical Engineering University of Iowa Iowa City IA 52242 United States

ISBN: (纸本)0791836215

Deterministic optimum designs that are obtained without consideration of uncertainty could lead to unreliable designs, which call for a reliability approach to design optimization, using a Reliability-Based design Optimization (RBDO) method. A typical RBDO process iteratively carries out a design optimization in an original random space (X-space) and reliability analysis in an independent and standard normal random space (U-space). This process requires numerous nonlinear mapping between X- and U-spaces for a various probability distributions. Therefore, the nonlinearity of RBDO problem will depend on the type of distribution of random parameters, since a transformation between X- and U-spaces introduces additional nonlinearity to reliability-based performance measures evaluated during the RBDO process. Evaluation of probabilistic constraints in RBDO can be carried out in two different ways: the Reliability Index Approach (RIA) and the Performance Measure Approach (PMA). Different reliability analysis approaches employed in RIA and PMA result in different behaviors of nonlinearity of RIA and PMA in the RBDO process. In this paper, it is shown that RIA becomes much more difficult to solve for non-normally distributed random parameters because of highly nonlinear transformations involved. However, PMA is rather independent of probability distributions because of little involvement of the nonlinear transformation. Copyright © 2002 by ASME.

关键词： Reliability analysis

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Topology optimization of element removal method using stress density

Topology optimization of element removal method using stress...

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9th AIAA/ISSMO Symposium on Multidisciplinary Analysis and Optimization 2002

作者： Lim, O-Kaung Kim, Chang-Sik Lee, Jin-Sik Department of Mechanical Design Engineering Pusan National University Kumjung Ku Busan 609-735 Korea Republic of Department of Computer Aided Design Kyonggi Institute of Technology Siheung City Gyeonggi Do 429-792 Korea Republic of

ISBN: (纸本)9781624101205

Topology optimization has been evolved into a very efficient conceptual design tool and has been utilized into design engineering processes. Traditional topology optimization has been using homogenization method and optimality criteria method. Homogenization method provides relationship equation between structure which included many holes and stiffness matrix in FEM. Optimality criteria method is used to update design variables while maintaining that volume fraction is uniform. Traditional topology optimization has advantage of good convergence but has disadvantage of too much convergence time. In one way to solve this problem, ERM(Element Removal Method) is presented. Then, it is applied to examples. From the results, it is verified that the time of convergence is very improved. © 2002 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

关键词： Stiffness matrix

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design optimization for structural-acoustic problems using fem-BEM

Design optimization for structural-acoustic problems using f...

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ASME 2002 International design engineering Technical Conferences and computers and Information in engineering Conference, IDETC/CIE 2002

作者： Choi, Kyung K. Dong, Jun Kim, Nam Ho Center for Computer-Aided Design Department of Mechanical and Industrial Engineering University of Iowa Iowa CityIA52242 United States Department of Mechanical Engineering University of Florida PO Box 116300 GainesvilleFL32611-6300 United States

ISBN: (纸本)0791836223

A structural-acoustic design optimization of a vehicle is presented using finite element and boundary element analyses. The steady-state dynamic behavior of the vehicle is calculated from the finite element frequency response analysis, while the sound pressure level within the acoustic cavity is calculated using the boundary element analysis. A reverse solution procedure is employed for the design sensitivity calculation using the adjoint variable method. An adjoint load is obtained from the acoustic boundary element re-analysis, while the adjoint solution is calculated from the structural dynamic reanalysis. The evaluation of pressure sensitivity only involves a numerical integration process for the structural part. Two design optimization problems are formulated and solved. It has been shown that the structural weight is saved when the noise level is maintained, and the weight needs to increase in order to reduce the noise level in the passenger compartment. Copyright © 2002 by ASME.

关键词： Boundary element method

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Planning for kinematically smooth manipulator trajectories

Planning for kinematically smooth manipulator trajectories

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ASME 2002 International design engineering Technical Conferences and computers and Information in engineering Conference, IDETC/CIE 2002

作者： Mi, Zan Yang, Jingzhou Abdel-Malek, Karim Jay, Laurent Center for Computer Aided Design Department of Mechanical and Industrial Engineering University of Iowa Iowa CityIA52242 United States Department of Mathematics University of Iowa Iowa CityIA52242-1419 United States

This paper presents a general methodology and accompanying formulation for planning kinematically smooth path trajectories for serial robot manipulators. Starting from an initial point on the path, it is required to traverse a path trajectory without halting the motion (typically due to switch from one inverse solution to another). The problem focuses on determining a starting configuration at the initial point on the path. The problem is formulated in terms of a constraint function and characterized by a system of differential-algebraic equations (DAEs) of index 2. These DAEs are solved numerically by Runge-Kutta (RK) methods while a best starting configuration is chosen using a cost-function driven optimization method. The formulation is demonstrated through a planar 3 degree of freedom robot manipulator. © Copyright 2002 by ASME.

关键词： Trajectories

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Meshfree analysis and die shape design of extrusion process

Meshfree analysis and die shape design of extrusion process

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9th AIAA/ISSMO Symposium on Multidisciplinary Analysis and Optimization 2002

作者： Kim, Nam H. Yi, Ki-Young Choi, Kyung K. Department of Mechanical Engineering University of Florida PO Box 116300 Gainesville FL 32611-6300 United States Center for Computer-Aided Design University of Iowa Iowa City IA 52242 United States

ISBN: (纸本)9781624101205

Meshfree analysis and die shape design of a 3-D metal extrusion problem is proposed. Multiplicatively decomposed elastoplasticity is used for the finite deformation nonlinear material model, while a penalty method is employed for the frictional contact condition between billet and die. The die shape design parameter in the CAD model is converted into a design velocity field on the rigid surface. The analytical design sensitivity formulation is derived in the continuum domain and is approximated using the meshfree method. A penalty-regularized contact variational equation is differentiated with respect to die shape design parameters. A material derivative consistent with the frictional returnmapping scheme is derived using non-associative plasticity. In order to improve the convergence behavior of the contact problem, a C2-continous contact surface is constructed from the scattered set of particles, such that the contact and friction force change continuously. © 2002 by Nam H. Kim, Ki-Young Yi, and Kyung K. Choi.

关键词： Elastoplasticity

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design sensitivity analysis of high-frequency structural acoustic problems

Design sensitivity analysis of high-frequency structural aco...

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9th AIAA/ISSMO Symposium on Multidisciplinary Analysis and Optimization 2002

作者： Kim, Nam H. Dong, Jun Choi, Kyung K. Department of Mechanical Engineering University of Florida PO Box 116300 Gainesville FL 32611-6300 United States Center for Computer-Aided Design University of Iowa Iowa City IA 52242 United States

ISBN: (纸本)9781624101205

A design sensitivity formulation for structural-acoustic problems at high frequencies (1,000-20,000 Hz) is presented using the energy finite element method. The material property, panel thickness, and structural damping factor are taken as design variables. The continuum method is used to derive the design sensitivity equation of the energy flow equation, while the discrete method is used to calculate the variation of the coupling relation. The design variable's effect on the power transfer coefficient is discussed in detail. Even when the system matrix equation is not symmetric, the adjoint problem is solved using the same factorized matrix from energy finite element analysis. design sensitivity results calculated from the proposed method are compared to finite difference sensitivity results with good agreement. © 2002 by Nam H. Kim, Jun Dong, and Kyung K. Choi.

关键词： Matrix algebra

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