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7th AIAA/USAF/NASA/ISSMO Symposium on Multidisciplinary Analysis and Optimization, 1998

作者： Choi, K.K. Kirn, Nam H. Park, Young H. Center for Computer-Aided Design and Department of Mechanical Engineering College of Engineering The University of Iowa Iowa CityIA52252 United States

In this paper, a continuum-based shape design sensitivity formulation for a frictional contact problem with a rigid body is proposed. A contact condition is imposed using a penalty method that regularizes the solution of variational inequality. Shape dependency of the contact variational form with respect to the design velocity field is obtained. It is shown that the sensitivity equation needs to be solved at the final converged load step for the frictionless contact problem, whereas the sensitivity equation needs to be solved at the converged configuration of each load step for the frictional contact problem because the sensitivity of the current load step depends on that of the previous load step. The continuum-based contact formulation and consistent linearization is critical for accurate shape design sensitivity results. The accuracy of the proposed method is compared with finite difference method with good agreement for a door seal contact example. © 1998 by K.K. Choi, N.H. Kim, and Y.H. Park.

关键词： Finite difference method

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design sensitivity analysis and optimization of nonlinear structural dynamics using dyna3d 7th

Design sensitivity analysis and optimization of nonlinear st...

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7th AIAA/USAF/NASA/ISSMO Symposium on Multidisciplinary Analysis and Optimization, 1998

作者： Choi, K.K. Cho, Seonho Center for Computer-Aided Design and Department of Mechanical Engineering College of Engineering The University of Iowa Iowa CityIA52242 United States

In this paper, continuum-based sizing and configuration design sensitivity analysis (DSA) and optimization methods using the established transient dynamic analysis code DYNA3D are developed. For transient dynamic analysis, the explicit central difference method is used. For the structural domain, the updated Lagrangian formulation is used since it is appropriate for the path dependent problem. The first-order variations of the kinetic energy form, strain energy form, load form, and kinematic and structural responses with respect to the sizing and configuration design variables are derived. For the updated Lagrangian formulation, the design velocity field that defines the mapping between the initial and perturbed designs is updated at each updated configuration. The direct differentiation method is used in this paper for DSA. Numerical implementation of sizing DSA, configuration DSA, and optimization of a vehicle frame and A-pillar models has been carried out using the nonlinear finite element analysis (FEA) code DYNA3D. © 1998 by K.K. Choi and S. Cho.

关键词： Strain energy

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Preparation of a virtual proving ground for constructionequipment simulation

Preparation of a virtual proving ground for constructionequi...

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ASME 1998 design engineering Technical Conferences, DETC 1998

作者： Grant, Peter Freeman, Jeffrey S. Vail, Rob Huck, Frank Center for Computer Aided Design The University of Iowa Iowa CityIA52242-1000 United States Department of Mechanical Engineering Center for Computer Aided Design The University of Iowa Iowa CityIA52242-1527 United States Caterpillar Inc. P.O. Box 1895 PeoriaIL61656-1895 United States

ISBN: (纸本)9780791880326

A multi-phased evaluation of the Iowa Driving Simulator asa virtual proving ground for construction equipment simulationis presented. In Phase I the Iowa Driving Simulator was evaluated in an "open-loop"mode to assess its capability to simulatea typical maneuver common to wheel loader operation, and itsviability as a test platform for human subject evaluation of thosemaneuvers.A typical wheel loader truck loading cycle involves numerous directional shifts. Cycle productivity is increased if theseshifts are executed at full engine throttle. Jerk and accelerationlevels associated with full throttle shifts, however, can cause bothoperator discomfort and spillage of loaded material. Electronically controlled transmissions have the potential to both minimize directional shift times and material loss while optimizingoperator comfort. This optimization will require an understanding of the factors which affect operator comfort during shifts. Astudy was therefore devised to determine those aspects of themotion generated by a directional shift which affect operatorcomfort. The Iowa Driving Simulator motion system was usedto present operators with a series of acceleration time historieswhich are representative of various shift strategies. The operatorsrated the relative comfort of each strategy during paired comparison tests. Limitations of the simulator motion system preventeddefinitive results from being drawn;however, results did confirmshift comfort criteria previously established by the machine manufacturer. Success of the Phase I effort was sufficient to warranta more in-depth *** Phase II a complete VPG environment for wheel loaderoperation on the IDS was developed and qualitatively *** VPG environment included a visual model of a mine pit,developed for Caterpillar, Inc. by engineers at its National Center for Supercomputing Applications office, combined with theimmersive motion capability of the Iowa Driving Simulator. Areal-time dynamics model of a gen

关键词： Automobile proving grounds

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Molecular simulation of gas transport in poly[1-(trimethylsilyl)-1-propyne]

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Journal of Polymer Science 1998年第3期36卷

作者： J. R. Fried D. K. Goyal The Center for Computer-Aided Molecular Design Department of Chemical Engineering University of Cincinnati Cincinnati Ohio 45221-0171

The bonded constants in the DREIDING force field have been parameterized for poly[1-(trimethylsilyl)-1-propyne] (PTMSP) from AM1 calculations of the dimer. The resultant force field has been validated through the simulation of amorphous cell density and x-ray data ( d -spacing) and used to obtain diffusion coefficients for five gases (He, O 2 , N 2 , CH 4 , and CO 2 ) from 0.5 ns NVT molecular dynamics using the Einstein relationship. In addition, solubility coefficients of these gases have been obtained from the particle insertion method of Bezus et al. and from a fixed-pressure Monte Carlo method which was also used to calculate sorption isotherms. In general, there is good to excellent agreement between experimental and simulated values of the diffusion and solubility coefficients for He, O 2 , N 2 , and CH 4 . Sorption isotherms and dual-mode parameters calculated from the simulation results for O 2 , N 2 , and CH 4 agree very favorably with experimental data (no experimental data was available for He). In the case of CO 2 , diffusion and solubility coefficients as well as sorption isotherms are underestimated. The less satisfactory results for CO 2 have been tentatively attributed to inadequacy of the generic nonbonded Lennard-Jones potential terms of DREIDING used in this study. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 519–536, 1998

关键词： poly[1-(trimethylsilyl)-1-propyne] Monte Carlo simulation diffusion coefficient molecular dynamics gas solubility

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SHAPE design SENSITIVITY ANALYSIS AND OPTIMIZATION FOR STRUCTURAL DURABILITY

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International Journal for Numerical Methods in engineering 1998年第9期40卷

作者： KUANG-HUA CHANG XIAOMING YU KYUNG K. CHOI Center for Computer-Aided Design and Department of Mechanical Engineering College of Engineering The University of Iowa Iowa City IA 52245 U.S.A.

In this paper, a design sensitivity analysis (DSA) method for fatigue life of 3-D solid structural components of mechanical systems with respect to shape design parameters is presented. The DSA method uses dynamic stress DSA obtained using an analytical approach to predict dynamic stress increment due to design changes; computes fatigue life of the component, including crack initiation and crack propagation, using the predicted dynamic stress; and uses the difference of the new life and the original life at the same critical point to approximate the sensitivity of fatigue life. A tracked vehicle roadarm is presented in this paper to demonstrate accuracy and efficiency of the DSA method. Also, this method is applied to support design optimization of the tracked vehicle roadarm considering crack initiation lives as design constraints. © 1997 by John Wiley & Sons, Ltd.

关键词： design sensitivity analysis shape design optimization fatigue life prediction multi-axial crack initiation structural durability

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Second-order shape design sensitivity using P-version finite element analysis

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STRUCTURAL OPTIMIZATION 1997年第2-3期14卷 91-99页

作者： Hwang, HY Choi, KK Chang, KH Center for Computer-Aided Design and Department of Mechanical Engineering College of Engineering The University of Iowa Iowa City USA

The p-version finite element analysis (FEA) approach is attractive for design sensitivity analysis (DSA) and optimization due to its high accuracy of analysis results, even with coarse mesh;insensitivity to finite element mesh distortion and aspect ratio;and tolerance for large shape design changes during design iterations. A continuum second-order shape DSA formulation is derived and implemented using p-version FEA. The second-order shape design sensitivity can be used for reliability based analysis and design optimization by incorporating it with the second-order reliability analysis method (SORM). Both the second-order shape DSA formulations with respect to the single and mixed shape design parameters are derived for elastic solids using the material derivative concept. Both the direct differentiation and hybrid methods are presented in this paper. A shape DSA is implemented by using an established p-version FEA code, STRESS CHECK. Two numerical examples, a connecting rod and bracket, are presented to demonstrate the feasibility and accuracy of the proposed seond-order shape DSA approach.

关键词： Structural analysis

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Analytical boundary of the workspace for general 3-DOF mechanisms

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INTERNATIONAL JOURNAL OF ROBOTICS RESEARCH 1997年第2期16卷 198-213页

作者： AbdelMalek, K Yeh, HJ Center for Computer Aided Design 2129 Engineering Building Department of Mechanical Engineering The University of Iowa Iowa City IA 52242

An analytical method is presented to obtain all surfaces enveloping the workspace of a general 3-DOF mechanism. The method is applicable to kinematic chains that cart be modeled using the Denavit-Hartenberg representation for serial kinematic chains or its modification for. closed-loop kinematic chains. The method developed is bused upon analytical criteria for determining singular behavior of the mechanism. By manipulating the Jacobian of the underlying mechanism, first-order singularities are computed. These singularities are then substituted into the constraint equation to parameterize singular surfaces representing barriers to motion. Singular surfaces are those resulting from a singular behavior of a joint generalized coordinate, allowing the manipulator to lose. one oi. more degrees of mobility. These surfaces are then intersected to determine singular curves, which represent the manipulator losing at least two degrees of mobility. Difficulties in separating singular behaviors at points along singular curves are encountered. Also, difficulties in computing tangents at the intersections of singular curves are addressed. These difficulties are resolved using an analysis of a quadratic form of the intersection of singular surfaces. An example is presented to validate the theory. Although the methods used are numerical, the main result of this work is the ability to analytically define boundary surfaces of the workspace.

关键词： Manipulators

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design propagation in mechanical systems: Kinematic analysis

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JOURNAL OF MECHANICAL design 1997年第3期119卷 338-345页

作者： Zou, H AbdelMalek, KA Wang, JY Center for Computer Aided Design (CCAD) and Department of Mechanical Engineering The University of Iowa Iowa City IA 52242

A broadly applicable formulation for investigating design propagations in mechanisms is developed and illustrated. Analytical criteria in terms of the variations of joint position vectors and orientation matrices for planar and spatial mechanisms are presented. Mechanisms are represented using graph theory and closed loops are converted to a tree-like structure by cutting joints and introducing new constraints. The Jacobian matrix in Cartesian space is then transformed to Joint coordinates space. Two cases are considered: a pair of bodies remain connected by one joint after cutting additional joints and a pair of bodies are disconnected after cutting joints. Using this method, a designer has the ability to study the propagated effect of changing a design variable on the design. The presented formulation is validated through a numerical example of a McPherson strut suspension system. The system is analyzed and an assembled configuration is completed after a change in design.

关键词： Jacobian matrices design Struts (engineering) Suspension systems Cutting Kinematic analysis

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design sensitivity analysis of structure-induced noise and vibration

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JOURNAL OF VIBRATION AND ACOUSTICS-TRANSACTIONS OF THE ASME 1997年第2期119卷 173-179页

作者： Choi, KK Shim, I Wang, S Department of Mechanical Engineering and Center for Computer-Aided Design The University of Iowa Iowa City Iowa 52242 Mechatronics Department Kwangju Institute of Science and Technology Kwangju Korea 506-303

A continuum design sensitivity analysis (DSA) method for dynamic frequency responses of structural-acoustic systems is developed using the adjoint variable and direct differentiation methods. A variational approach with a non-self-adjoint operator for complex variables is used to retain the continuum elasticity formulation throughout derivation of design sensitivity results. It is shown that the adjoint variable method is applicable to the variational equation with the non-self-adjoint operator. Sizing design variables such as se thickness and cross-sectional area of structural components are considered for the design sensitivity analysis. A numerical implementation method of continuum DSA results is developed by postprocessing analysis results fi-om established finite element analysis (FEA) codes to obtain the design sensitivity of noise and vibration performance measures of the structural-acoustic systems. The numerical DSA method presented in this paper is limited to FEA and boundary element analysis (BEA) is not considered. A numerical method is developed to compute design sensitivity of direct and modal frequency FEA results. For the modal frequency FEA method, the numerical DSA method provides design sensitivity very efficiently without requiring design sensitivities of eigenvectors. The numerical method has been tested using passenger vehicle problems. Accurate design sensitivity results are obtained for analysis results obtained from established FEA codes.

关键词： design sensitivity analysis Structural elements (Construction) Noise (Sound) Vehicles design Eigenvalues Frequency response Acoustics Numerical analysis Elasticity Boundary element methods Vibration Finite element analysis

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An object-oriented machine condition monitoring scheme for rotating machinery

An object-oriented machine condition monitoring scheme for r...

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ASME 1997 design engineering Technical Conferences, DETC 1997

作者： Bettig, Bernhard P. Han, Ray P.S. Department of Mechanical and Aerospace Engineering Arizona State University TempeAZ85287-6106 United States Department of Mechanical Engineering The Center for Computer-Aided Design The University of Iowa Iowa CityIA52242-1527 United States

ISBN: (纸本)9780791880432

The increasing reliability and accuracy of sensors as well as improvements in data acquisition and display have lead to the predictive maintenance method of scheduling machinery overhauls and replacement. Numerical models of the dynamics of a machine may be used to more accurately predict and schedule maintenance by relating variables describing deterioration mechanisms to machine measurements. For instance, vibration measurements may be used to determine bearing stiffness which is then trended. The present paper describes the concepts of a program to interactively examine and predict the health of a rotating machine. To facilitate a userfriendly implementation of the method, the paper also presents an object-oriented framework approach for introducing GUI based graphics. © 1997 American Society of Mechanical Engineers (ASME). All rights reserved.

关键词： Rotating machinery

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