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IMPLEMENTATION OF design SENSITIVITY ANALYSIS WITH EXISTING FINITE-ELEMENT CODES

JOURNAL OF MECHANISMS TRANSMISSIONS AND AUTOMATION IN design-TRANSACTIONS OF THE ASME 1987年第3期109卷 385-391页

作者： CHOI, KK SANTOS, JLT FREDERICK, MC Center for Computer Aided Design and Department of Mechanical Engineering The University of Iowa Iowa City IA 52242

A numerical method is presented to implement structural design sensitivity analysis theory, using the versatility and convenience of existing finite element structural analysis programs. design variables such as thickness and cross-sectional areas of components of individual members and built-up structures are considered. Structural performance functionals considered include displacement and stress. The method is also applicable for eigenvalue problem design sensitivity analysis. It is shown that calculations can be carried out outside existing finite element codes, using postprocessing data only. Thus design sensitivity analysis software does not have to be imbedded in an existing finite element code. Feasibility of the method is shown through analysis of several problems, including a built-up structure. Accurate design sensitivity results are obtained without the uncertainty of numerical accuracy associated with selection of finite difference perturbations.

关键词： design sensitivity analysis Displacement design Eigenvalues Stress Structural design Uncertainty Numerical analysis Sensitivity analysis computer software Structural analysis Finite element analysis

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ACCELERATED FAULT SIMULATION AND FAULT GRADING IN COMBINATIONAL-CIRCUITS

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IEEE TRANSACTIONS ON computer-aided design OF INTEGRATED CIRCUITS AND SYSTEMS 1987年第5期6卷 704-712页

作者： ANTREICH, KJ SCHULZ, MH Institute of Computer Aided Design Department of Electrical Engineering Technical University Munich Munich Germany

The principles of fault simulation and fault grading are introduced by a general description of the problem. Based upon the well-known concept of restricting fault simulation to the fanout stems and of combining it with a backward traversal inside the fanout-free regions of the circuit, proposals are presented to further accelerate fault simulation and fault grading. These proposals aim at parallel processing of patterns at all stages of the calculation procedure, at reducing the number of fanout stems for which a fault simulation has to be carried out, and at taking advantage of structural characteristics of the circuit. An experiment with a set of benchmark circuits demonstrates the efficiency of the proposed approaches.

关键词： Circuit faults Acceleration Circuit simulation Combinational circuits Circuit testing Proposals Costs computational modeling Very large scale integration Sequential analysis

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A DIFFERENTIABLE NULL SPACE METHOD FOR CONSTRAINED DYNAMIC ANALYSIS

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JOURNAL OF MECHANISMS TRANSMISSIONS AND AUTOMATION IN design-TRANSACTIONS OF THE ASME 1987年第3期109卷 405-411页

作者： LIANG, CG LANCE, GM General Motors Research Laboratories Warren MI Center for Computer Aided Design Department of Mechanical Engineering College of Engineering The University of Iowa Iowa City IA 52242

A geometric approach to the solution of the dynamic response of constrained mechanical systems is proposed. A continuous and differentiable basis of the constraint null space is automatically generated using the Gram-Schmidt process. The independent coordinates are obtained by transforming the physical velocity coordinates to the tangent hyperplane of the constraint surface. As a result the independent coordinates lie on the constraint surface and no constraint violation control is necessary.

关键词： Dynamic response Dynamic analysis

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computational fatigue life prediction of welded and non-welded ground vehicle components

Computational fatigue life prediction of welded and non-weld...

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Passenger Car Meeting and Exposition

作者： Stephens, R.I. Dopker, B. Haug, E.J. Baek, W.K. Johnson, L.P. Liu, T.S. Mechanical Engineering Department and Center for Computer Aided Design University of Iowa Iowa City IA United States

A variable amplitude computational fatigue life prediction method was developed for use with welded and/or non-welded components for use with the ground vehicle industry. The method is principally applicable to the pre-prototype and prototype iteration/optimization design stage. For welded components, the method incorporates the hot-spot stress approach developed by the European community for off-shore structures. For non-welded notched components, the method incorporates the local notch strain approach. Finite element stress-strain analysis using the ANSYS program combined with dynamic simulation utilizing the DADS program transforms a vehicle wheel input, in the form of a terrain surface description, to the principal hot spot stress or nominal principal strain at each node of interest as a function of time. Rainflow counting and linear damage accumulation along with specific material or weld classification properties are incorporated. Verification of the welded and non-weld fatigue life prediction methods were made using welded cruciform specimen and keyhole specimen variable amplitude test results obtained from the literature. Fatigue life predictions were also made at critical locations on the HMMWV military vehicle subjected to simple terrain wheel input. The computational fatigue life prediction methods developed have been implemented in the Integrated Analysis Capability (IAC) command processor and data base system. This program interfaces well established analysis tools and provides the engineer control of the complex interdisciplinary process. Copyright © 1987 Society of Automotive Engineers, Inc.

关键词： Finite element method

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Selection of deformation modes for flexible mul tibodv dynamics

Selection of deformation modes for flexible mul tibodv dynam...

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ASME 1987 design Technology Conferences, DETC 1987

作者： Kim, S.-S. Haug, E.J. Center for Computer Aided Design and Department of Mechanical Engineering College of Engineering University of Iowa Iowa CityIA United States

ISBN: (纸本)9780791897744

This paper presents a method of selecting boundary conditions and deformation modes for redundantly constrained flexible components in mechanical system dynamics. Gaussian elimination is used to partition the coefficient matrix in equilibrium equations for each flexible component, leading to definition of a retained statically determinate set and a redundant set of boundary conditions. Methods for selection of deformation modes is presented, to account for deformation due to constraint reaction forces. A door closing mechanism and a moving flexible beam illustrate the method of selecting boundary conditions and the effectiveness of constraint modes for approximation for system dynamic response. © 1987 American Society of Mechanical Engineers (ASME). All rights reserved.

关键词： Boundary conditions

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A substructure technique for dynamics of flexible mechanical systems with contact-impact

A substructure technique for dynamics of flexible mechanical...

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ASME 1987 design Technology Conferences, DETC 1987

作者： Wu, S.-C. Haug, E.J. Structures and Dynamics Division NASA-Langley HamptonVA United States Center for Computer Aided Design and Department of Mechanical Engineering University of Iowa Iowa CityIA United States

ISBN: (纸本)9780791897744

A substructure synthesis method is proposed to account for contact-impact effects in flexible components of mechanical systems. Components that may come into contact is divided into substructures, on each of which local deformation modes are defined to described deformation fields of components. Constraint modes and fixed interface normal modes are used to account for elastic deformation within each substructure. A constraint addition-deletion technique is used to account for contact between impacting bodies. Lagrange multipliers associated with the constraints, which represent constraint forces, are used to determine separation of contacting nodes. Use of the method is illustrated on problems of longitudinal and transverse impact of bodies. © 1987 American Society of Mechanical Engineers (ASME). All rights reserved.

关键词： Lagrange multipliers

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Control of Distributed Parameter Systems with Spillover using an Augmented Observer

Control of Distributed Parameter Systems with Spillover usin...

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American Control Conference (ACC)

作者： Yossi Chait Clark J. Radcliffe Department of Mechanical Engineering A.H. Case Center for Computer-Aided Design Michigan State University East Lansing MI USA

Modern modal control methods for flexible structures, based on a truncated model of the structure's dynamics, have control and observation spillover which can reduce the stability margin of the controlled structure. The sensor output is often filtered to reduce observation spillover, however, it introduces signal distortion which perturbs the closed-loop system pole locations. This can reduce stability margins and jeopardize convergence of the observer. When the filter equation is included in the standard observer equations the separation principle between the controller and the observer will no longer holds, and the closed-loop poles cannot be located using standard pole placement methods. A new method is presented, where a first order filter is included in an augmented observer. The separation principle, and controllability and observability properties of the original system are shown to remain when using the augmented observer. Filter and spillover produced pole perturbations in the different methods are illustrated with a numerical example.

关键词： Distributed control Control systems Distributed parameter systems Filters Stability Equations Flexible structures Sensor systems Distortion Convergence

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Accelerated Transition Fault Simulation

Accelerated Transition Fault Simulation

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design Automation Conference

作者： M.H. Schulz F. Brglez Insitute of Computer Aided Design Department of Electrical Engineering Technical University of Munich Munich Germany Bell-Northern Research Inc. NC USA

This paper presents a new and an effective approach to fault simulation of transition faults in combinational or scan - based logic. An experiment with a set of benchmark circuits demonstrates the efficiency of the approach, achieved by combining a very fast single stuck - at fault simulation algorithm with a quasi - static definition of a transition fault. Tests that cover transition faults are becoming increasingly important as they also provide a cover for most typical transistor stuck - open faults in CMOS.

关键词： Acceleration Circuit faults Circuit testing Circuit simulation Fault detection Semiconductor device modeling computational modeling Proposals Logic testing Benchmark testing

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A design Study of a Positioning System with Electrohydraulic Actuation

A Design Study of a Positioning System with Electrohydraulic...

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American Control Conference (ACC)

作者： Steven T. Sherman George M. Lance McDonnell Douglas Corporation Douglas Aircraft Company Inc. Long Beach CA USA Center for Computer Aided Design and Department of Mechanical Engineering University of Iowa Iowa IA USA

The results of a study of the modeling and design of a positioning system using electrohydraulic actuation are presented. Linearization of the servovalve characteristics near null position is considered. A control configuration is developed based on an optimal linear design and a modification to improve large amplitude nonlinear performance. The nonlinear behavior is obtained by use of an integrated system simulation program.

关键词： Electrohydraulics Valves Weapons Actuators Analytical models Control system synthesis Nonlinear control systems Mathematical model Aircraft propulsion Lakes

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A METHODOLOGY FOR WORST-CASE ANALYSIS OF INTEGRATED-CIRCUITS

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IEEE TRANSACTIONS ON computer-aided design OF INTEGRATED CIRCUITS AND SYSTEMS 1986年第1期5卷 104-113页

作者： NASSIF, SR STROJWAS, AJ DIRECTOR, SW Department Electrical and Computer Engineering Research Center for Computer-Aided Design Carnegie Mellon University Pittsburgh PA USA

Worst-case analysis is one of the most often used techniques for verifying that the sensitivity of integrated circuit (IC) performances to changes in manufacturing conditions is minimized. However, worst-case analysis is often carried out in terms of a correlated set of parameters, which results in a design that is unnecessarily pessimistic. This paper presents a new approach to the worst-case analysis of integrated circuits that results in more realistic estimates of variations in device and circuit performances. In particular, worst-case analysis is performed in terms of a set of statistically independent process disturbances. A software package for worst-case analysis is described and illustrated by a number of examples. The results of the proposed worst-case analysis method are compared to Monte Carlo simulations.

关键词： Circuit analysis Performance analysis Fluctuations Power dissipation Circuit simulation Integrated circuit manufacture Software packages Manufacturing processes Performance evaluation Delay lines

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