1993-1999 MSC Users' Conference Proceedings

Categories

Design/Manufacturing Methods

APPLYING MSC/PATRAN AND MSC/NASTRAN TO IMPROVE THE DESIGN PERFORMANCE OF LARGE BULK MATERIALS HANDLING MACHINES (Acrobat 33K) #3798, 9 pgs.
R.C. Morgan, Dr. S. Loganathan, and Dr. F. Gatto--BHP Engineering Pty Ltd.

ABSTRACT: Bulk materials handling machines such as stackers, bucket wheel reclaimers, ship loaders and ship unloaders are complex moving structures with onerous loading and service conditions. Due to such factors there is the potential for many failure modes and problem areas on these machines.

Machines are normally purpose designed for the particular application at a port, mine or industrial facility. In the current environment, high reliability standards are required in order to provide operational security for business and safety to personnel.

Dynamic, buckling and non linear behaviour of such structures can all contribute to failures and operational problems. Hence a sophisticated analysis and modelling tool is required in order to provide adequate representation under service conditions.

Due to the complexity and size of these structures, models with large numbers of degrees of freedom are required for analysis. It was previously very time consuming and costly to carry out such work, putting it out of the realms of commercial application. However the compatibility of MSC/PATRAN with CAD systems and the ease of building large models, together with recent developments in the efficiency of the solvers in MSC/NASTRAN, opens new frontiers for engineers to critically examine the design of new structures before they are built.

Similarly, with the application of MSC/PATRAN and MSC/NASTRAN, existing machines can be critically examined and cost effective life extension strategies developed to deliver major economic benefits to owners.

COMBINING MSC/NASTRAN, SENSITIVITY METHODS AND VIRTUAL REALITY TO FACILITATE INTERACTIVE DESIGN (Acrobat 819K) #395, 11 pgs.
Tsung-Pin Yeh--Iowa State University
Judy M. Vance--Iowa State University

ABSTRACT: This paper will present results of a research project which investigated incorporating finite element analysis results into a virtual environment. Three programs developed in the course of this research are described. MSC/NASTRAN is used to perform the analysis and WorldToolKit and GL are used to develop the virtual environment. Virtual reality peripherals including a head-mounted display and a BOOM are used with a 3D mouse as interface devices. Sensitivity methods are incorporated into the programs to allow the designer to change design variables and immediately view the effects without performing a re-analysis.

AN INTRODUCTION TO TOLERANCE ANALYSIS OF FLEXIBLE ASSEMBLIES (Acrobat 256K) 1996, 14 pgs.
K. G. Merkley--Brigham Young University
K. W. Chase--Brigham Young University
E. Perry--Brigham Young University

ABSTRACT: Tolerance analysis is used to predict the effects of manufacturing variation on finished products. Either design tolerances or manufacturing process data may be used to define the variation. Current efforts in tolerance analysis assume rigid body motions. This paper will present a method of combining the flexibility of individual parts, derived from the finite element method, with a rigid body tolerance analysis of the assembly. These results can be used to predict statistical variation in residual stress and part displacement. This paper will show that manufacturing variation can produce significant residual stress in assemblies. It will demonstrate two different methods of combining tolerance analysis with the flexibility of the assembly.

MODAL QUALITY. THE KEY TO CAD/CAM/CAE INTEROPERABILITY (Acrobat 195K) #2398, 12 pgs.
Dan McKenney--International TechneGroup Incorporated

ABSTRACT: Today 3D CAD Models are driving a growing number of downstream CAD/CAM/CAE applications. When those involved in Finite Element Analysis, Rapid prototyping, Numerical Control, and Data Exchange functions can work directly with the original, clean CAD model the results are significant boosts to product quality, production costs, and time to market.

Unfortunately a growing number of CAD models contain hidden errors or anomalies requiring the models to be reworked by the downstream user. Studies show that FEA users, for example, are spending as much as 70% of their time fixing CAD models. Similarly, other downstream users are wasting a significant amount of time correcting CAD model errors as well.

This presentation will discuss the Model Quality concept and demonstrate how these problems can be easily isolated and identified. It will show how implementing a Model Quality program can slash or eliminate the need for the downstream users to fix problem CAD files. We will detail how CAD/CAM/CAE users at any level can and should begin implementing such a program. While the presentation will provide a solid overview, it will highlight the CAE interests of the audience.

MODELING OF DIE SURFACE FEATURES ON INTEGRATED CIRCUITS TO IMPROVE DEVICE RELIABILITY (Acrobat 1.9MB) 1996, 14 pgs.
John Sauber--Digital Equipment Corporation

ABSTRACT: When semiconductor devices are encapsulated in plastic, the glass-like dielectric and passivations layers on the surface of the die are subjected to very high stresses from the shrinkage of the molding compound. This paper reviews the modeling approach used to simulate very small features (~0.1 mm) inside of a relatively large (~28000 mm) package, with the goal of optimizing the design to eliminate device failure caused by cracking of the dielectric and passivation layers.

RAPID OPTO-MECHANICAL DESIGN USING PRO/E, MSC/NASTRAN AND CODE V. (Acrobat 683K) #2198, 10 pgs.
Victor J. Wagner, Richard Malnory, and K. Scott. Ellis--Raytheon Missile Systems Company

ABSTRACT: The mechanical design of Optical systems (Opto-Mechanical Design) is typically concerned with minimizing the impact of the mechanical structure and environments on optical performance. Structurally insignificant loads may induce unacceptable motion and/or distortion into the optical elements, which are summed along the optical path resulting in total image blur and error. Optical system designs are therefore extremely sensitive to mounting configurations and structural dynamic characteristics of the mechanical system. A process for efficient design investigation is discussed that provides rapid system and individual optical element error predictions for mechanical system design. Topics include discussions of fundamental Opto-Mechanical design considerations, Pro/E model modification to facilitate automesh techniques, various automesh approaches using MSC/PATRAN and Pro/Engineer, tet4 vs tet10 element performance and accuracy with MSC/NASTRAN, Line Of Sight (LOS) error predictions, and Zernike polynomial calculations for optical surface aberrations using the MSC/OPOLY utility and Code V.

RECENT ADVANCES IN MSC/PATRAN PRE-PROCESSING SOFTWARE ALLOWS MODELING OF COMPLEX AUTOMOTIVE LAMP DESIGNS (Acrobat 618K) #3398, 9 pgs.
William I. Moore, Eric S. Donovan, and Christopher R. Powers-- Delphi Interior and Lighting Systems

ABSTRACT: Advances in automotive lamp designs have resulted in a more compact, aerodynamic packaging and the use of less expensive plastic materials for the lens and housing. The smaller packaging and lower melting point of plastics have increased the need for a predictive tool for simulating the lamp temperature rise under operating conditions. The modeling of lamps requires sophisticated analysis tools incorporating computational fluid dynamics and specular radiation. These tools use a finite element method to solve a system of non-linear equations for velocity, pressure and temperature. In addition to the non-linearity, the complex parabolic shape of the lamp reflector and lens requires very powerful mesh generation capability in order to produce an adequately refined mesh. The lamp modeling is performed in two stages. First the model is generated by importing CAD data from Pro/ENGINEER or Unigraphics into the MSC/PATRAN pre-processor. The surfaces are then meshed with triangular elements which are used as a seed for creating the air volume and lamp solid wall tetrahedral element meshes. The use of the new MSC/PATRAN hybrid tetrahedral mesher has enabled the creation of very complex 3D element meshes to represent fluid volumes with several hundred thousand elements. MSC/PATRAN has become a common pre/post-processor for many analysis codes because of the open CAE environment, advanced meshing capability, ease of applying loads and boundary conditions and effective post-processing capability for displaying results.

DMAP Applications

A DMAP ALTER TO ALLOW AMPLITUDE-DEPENDENT MODAL DAMPING IN A TRANSIENT SOLUTION (Acrobat 224K) 1996, 15 pgs.
Ted Rose--The MacNeal-Schwendler Corporation
Martin McNamee--The MacNeal-Schwendler Corporation

ABSTRACT: Most structural systems display some amount of nonlinear behavior. In most analyses, we assume that the nonlinear affects are not important and use a linear approximation. Often the nonlinear affects cannot be ignored and must be included in the solution of the problem. This paper addresses a special case where the modal damping may not be a constant fraction of the critical damping ratio, rather the damping ratio is a function of the magnitude of the response.

A DMAP alter is presented which allows the user to include modal damping which is a function of the displacement (or velocity) measured at selected points.

A DMAP ALTER TO CALCULATE THE CONTRIBUTIONS OF INDIVIDUAL MODES IN A MODAL COMPLEX EIGENVALUE OR FREQUENCY RESPONSE SOLUTION(Acrobat 358K) #1798, 9 pgs.
Ted Rose Manager--MSC

ABSTRACT: In this paper, a DMAP alter is presented which will calculate and print the Contributions of individual modes to a solution at user-selected locations. The alter allows you to chose from several different formats for the output: Magnitude/phase, real/imaginary, projection on solution, fraction of solution, and others.

DMAP ALTERS FOR CALCULATING AND SUMMARIZING RESULTANT FORCES FROM THE APPLICATION OF SPC AND AUTOSPC CONSTRAINTS (Acrobat 983K) #0994, 18 pgs.
Grant Parker -- Northrop Corporation
John Brown -- Northrop Corporation
Ted Rose -- The MacNeal-Schwendler Corporation
Jim Swan -- The MacNeal-Schwendler Corporation

ABSTRACT: MSC/NASTRAN DMAP (Direct Matrix Abstraction Programs) alter programs have been written to identify and summarize all resultant forces from single point constraints (SPC) and AUTOSPC constraints. This capability was developed primarily as an enhancement to previous DMAPs for model checking and identifying grounding problems and constraint checks through the use of strain energy calculations on the stiffness matrix.

Discussion and examples of the use of the DMAPs for model verification are presented.

MDI/ADAMS-MSC/NASTRAN INTEGRATION USING COMPONENT MODE SYNTHESIS (Acrobat 98K) #1998, 10 pgs.
Gisli Ottarson--Mechanical Dynamics Inc.
Greg Moore--The MacNeal-Schwendler Corporation
Diego Minen--Mechanical Dynamics Inc., Italy

ABSTRACT: Improvements continue to be made in the area of MSC/NASTRAN-MDI/ADAMS coupling, with the status of the jointly developed DMAP/translator-based interface described herein. Although the current implementation still relies on a combined DMAP alter and an external utility, the results of this phase of development include a number of enhancements which greatly improve ease-of-use, performance, and results quality. This paper briefly describes the motivation for the current work, outlines improvements made to the component modes-based interface, and concludes with an example of the new interface's use in automotive vehicle design.

MSC/NASTRAN BASED COMPONENT MODE SYNTHESIS ANALYSIS WITHOUT THE USE OF DMAPS (Acrobat 64K) 1996, 19 pgs.
Tarun Ghosh--Rockwell International Corporation

ABSTRACT: Component mode synthesis method of analyzing large structures is a very powerful and efficient tool available in MSC/NASTRAN. For many years the method based on MSC/NASTRAN has been widely used in the aerospace and automotive industries where different physical components are often designed and modelled by different organizations, departments or groups. For forward and backward flow of data it is important to have a standard, yet flexible, method. Unfortunately, different organizations have their own Direct Matrix Abstraction Program (DMAP) based method of component mode synthesis. This becomes an obstacle to the free flow of data, increases the chance of errors, imposes restrictions and creates a major task of updating and verifying the DMAPs with MSC/NASTRAN revisions.

The purpose of this paper is to show through an actual example how component mode synthesis can be performed in MSC/NASTRAN without the use of elaborate DMAPs. The analyst can do such tasks as plotting, data recovery, apply loads, transfer data forward and backward, without the use of a single structured solution based DMAP. The net result is an efficient process that reduces the time and cost of the analysis.

STIFFNESS-GENERATED RIGID-BODY MODE SHAPES FOR LANCZOS EIGENSOLUIION WITH SUPORT DOF VIA A MSC/NASTRAN DMAP ALTER (Acrobat 694K) #1094, 16 pgs.
Ayman A. Abdallah -- Analex Corporation
Alan R Barnett -- Analex Corporation
Timothy W. Widrick -- Analex Corporation
Richard T Manella -- National Aeronautics and Space Administration
Robert P. Miller -- National Aeronautics and Space Administration

ABSTRACT: When using all MSC/NASTRAN eigensolution methods except Lanczos, the analyst can replace the coupled system rigid-body modes calculated within DMAP module READ with mass orthogonalized and normalized rigid-body modes generated from the system stiffness. This option is invoked by defining MSC/NASTRAN r-set degrees-of- freedom via the SUPORT Hulk Data card. The newly calculated modes are required if the rigid-body modes calculated by the eigensolver are not "clean" due to numerical roundoffs in the solution. When performing transient structural dynamic load analyses, the numerical roundoffs can result in inaccurate rigid-body accelerations which affect steady-state responses. Unfortunately, when using the Lanczos method and defining r-set degrees-of-freedom, the rigid-body modes calculated within DMAP module REIGL are retained. To overcome this limitation and to allow MSC/NASTRAN to handle SUPORT degrees-of-freedom identically for all eigensolvers, a DMAP Alter has been written which replaces Lanczos-calculated rigid-body modes with stiffness-generated rigid-body modes. The newly generated rigid-body modes are normalized with respect to the system mass and orthogonalized using the Gram-Schmidt technique. This algorithm has been implemented as an enhancement to an existing coupled loads methodology.

TRANSIENT ANALYSIS MODE PARTICIPATION FOR MODAL SURVEY TARGET MODE SELECTION USING MSC/NASTRAN DMAP (Acrobat 1.14MB) #0894, 19 pgs.
Alan R. Bamett -- Analex Corporation
Omar M. Ibrahim -- Analex Corporation
Timothy L. Sullivan -- Analex Corporation
Thomas W. Goodnight -- National Aeronautics and Space Administration

ABSTRACT: Many methods have been developed to aid analysts in identifying component modes which contribute significantly to component responses. These modes, typically targeted for dynamic model correlation via a modal survey, are known as target modes. Most methods used to identify target modes are based on component global dynamic behavior. It is sometimes unclear if these methods identify all modes contributing to responses important to the analyst. These responses are usually those in areas of hardware design concerns. One method used to check the completeness of target mode sets and identify modes contributing significantly to important component responses is mode participation. With this method, the participation of component modes in dynamic responses is quantified. Those modes which have high participation are likely modal survey target modes. Mode participation is most beneficial when it is used with responses from analyses simulating actual flight events. For spacecraft, these responses are generated via a structural dynamic coupled loads analysis. Using MSC/NASTRAN DMAP, a method has been developed for calculating mode participation based on transient coupled loads analysis results. The algorithm has been implemented to be compatible with an existing coupled loads methodology and has been used successfully to develop a set of modal survey target modes.

DMAP in Dynamics

EFFECTIVE MASS SENSITIVITY: A DMAP PROCEDURE (Acrobat 743K) #3995, 18 pgs.
A. Bramante--Alenia Spazio
A. Paolozzi--Universita' degli Studi di Roma "La Sapienza"
I. Peroni--Universita' degli Studi di Roma "La Sapienza"

ABSTRACT: To know how the effective modal mass changes, while the structure modifies in the design phase, is helpful in aerospace engineering. To this aim an MSC/NASTRAN DMAP procedure, for yielding the effective mass partial derivative with respect to the structural lumped mass, has been developed. To validate the procedure some outputs are compared with the standard Nastran ones for a spacecraft structural model. The results show a good agreement and qualify the procedure as very reliable.

A GENERAL PROCEDURE FOR FINITE ELEMENT MODEL CHECK AND MODEL IDENTIFICATION (Acrobat 1.39MB) #3895, 18 pgs.
Y T Chung----McDonnell Douglas Aerospace Company - West
L. L. Kahre--McDonnell Douglas Aerospace Company - West

ABSTRACT: Dynamic loads analysis using finite element models is a major task in the structural design process. An error free model to predict accurate loads or responses is essential for designing a vehicle to meet its performance requirements. A systematic approach employing MSC/NASTRAN direct matrix algorithm program is developed to check the residual loads and the rigid body strain energy for identifying improper modeling. The modal effective mass of each system mode is also computed using rigid body modes for statically determinate structures or constraint modes for statically indeterminate structures to identify the significant modes of the structure with respect to the constrained interfaces. These significant modes are the target modes to be identified in the payload structural qualification modal survey for generating a test-verified dynamic model used in the verification loads analysis. Furthermore, the modal kinetic energy distribution per degree of freedom and the kinetic energy fraction for each superelement are computed to identify the important subsystem local modes in additional to the standard strain energy fraction provided by MSC/NASTRAN. An example is presented to demonstrate this systematic approach for analytical model check and model identification.

A STAND-ALONE DMAP PROGRAM FOR MODAL CROSS-CORRELATION (Acrobat 564K) #4095, 10 pgs.
Jack Scanlon--Analex Corporation

Jim Swan--MacNeal-Schwendler Corporation

ABSTRACT: A standalone DMAP program has been developed which gives the MSC/NASTRAN analyst a more complete set of tools with which to address the task of modal cross-correlation analysis. This program brings a number of user-oriented features to the otherwise fairly simple [phi]<sup>T[M] [phi] calculations. These features include options for reducing and realigning the DOFs between the two models (manual or automatic), re-ordering and/or removing modes, and several normalizing and filtering options. The program has been tested and used with both simple test models and real-world models. The paper briefly explains modal cross correlation and discusses the tools that this DMAP brings for both pre-processing of the input matrices and post-processing of the results.

Durability

FATIGUE LIFE ANALYSIS OF VOLVO S80 BI-FUEL (Acrobat 195K) #0499, 7 pgs.
M. Fermér, G. McInally and G. Sandin--Volvo Car Corporation, Sweden

ABSTRACT: The dimensioning of Volvo S80 Bi-Fuel has been totally performed in a virtual environment. Several design solutions have been numerically investigated using two dominant load cases. The robustness of chosen solutions have been investigated by calculations with critical spotwelds removed from the FE-model. The final design has been verified with a full four poster shake rig test. Although the rear floor is totally redesigned for the gas tank installation, no fatigue failure has been observed in this area.

The paper gives some insight into the dimensioning process, with special focus on spotweld fatigue analysis. All fatigue calculations were performed using MSC/Fatigue.

FE-BASED WHEEL FATIGUE ANALYSIS USING MSC.FATIGUE (Acrobat 130 K) #0599, 5 pgs.
S.C. Kerr and N.W.M. Bishop--MSC.Software, UK
D.L. Russell and U.S. Patel--BF Goodrich Aerospace, OH

ABSTRACT: A validation exercise is currently underway at BF Goodrich to evaluate the fatigue life of a rotating wheel using a new "WHEELS" capability within MSC.FATIGUE. BF Goodrich will shortly be using this capability to automate fatigue calculations for rotating aircraft wheels subject to vertical and lateral loads. As part of a validation exercise, an FE model of the wheel was analysed by applying a bearing roller load around the inner surface of the wheel hub at 15 ^o increments. A linear static analysis was conducted at each increment to produce a stress tensor history ( s_x, s_y, and t_xy) for all surface nodes. Due to the nature of a rolling wheel, it was expected that the principal stresses and their directions would vary for each increment. For this reason, the stress tensors were also rotated on the model surface through 360 ^o, at 10 ^o increments, to calculate the components of the principal stresses in those directions. All stress data was run through an S-N fatigue life analysis with no mean stress correction. Although not complete, the results are expected to show contour plots of fatigue life and fatigue damage for all nodes at the worst (most damaging) surface angle. MSC.Software envisions that this new capability can also be applied to any rotating body, especially automotive wheels.

THE IGNORED FAILURE MODE: SPOTWELD UNDER INPLANE ROTATION (Acrobat 683K) #0399, 11 pgs.
Pey Wung--Ford Motor Company, USA

ABSTRACT: Spot weld failures of complicated structure, such as automobile bodies, are difficult to explain using current multiaxial spot weld failure theory. After introducing the in-plane rotational failure mode, some unexplainable spot weld failures become explainable. The purpose of this report is to introduce the spot weld rotational test, its relative strengths and its finite element simulation. It is found that the strength of a spot weld under the in-plane rotational mode is far below the strengths of the same spot weld under other failure modes such as in-plane shear. Hence, the work conducted in this study could be a foundation for a new generation of multiaxial spot weld failure theory development.

USING MSC.Fatigue TO ESTIMATE THE FATIGUE DAMAGE CAUSED TO VIBRATING AUTOMOTIVE COMPONENTS (NOT PRESENTED) (Acrobat 650K) #3899, 7 pgs.
Neil Bishop, Stuart Kerr, and Alan Caserio--MSC.Software

ABSTRACT: An earlier paper demonstrated that vibration fatigue techniques can be a powerful tool in the design of automotive components subjected to vibration loadings. This paper extends the work by utilizing new techniques in the software program MSC.Fatigue. In particular, new techniques now exist which enable principal stresses to be computer over the entire surface region of interest. Complete results are included in this paper.

Vibration testing of components using accelerated test tracks or laboratory simulators is widely used in automotive design, as is fatigue testing for reliability. Furthermore, there are many common features between these two disciplines. However, problems often arise when engineers who are skilled in one field have to use techniques and concepts more generally used in the other. One example of such a situation concerns the use of frequency domain descriptions of structural response, which are commonplace in vibration. Many engineering applications, such as offshore structures and wind turbines, have already seen the benefits of using frequency domain fatigue analysis for reliability assessment. The purpose of this paper is to assess the benefits of frequency domain fatigue analysis and compare it with more conventional time domain techniques. A typical automotive component has been analyzed using MSC.Nastran and MSC.Fatigue using both time and frequency domain methods. Probability density functions and fatigue lives computed using output from these two different approaches show good agreement.

USING THE MSC/NASTRAN SUPERELEMENT MODAL METHOD TO IMPROVE THE ACCURACY OF PREDICTIVE FATIGUE LOADS OF A SHORT AND LONG ARM TYPE REAR SUSPENSION (Acrobat 228 K) #0699, 24 pgs.
Dr. Hong Zhu, Dr. John Dakin and Ray Pountney--Ford Motor Company Limitd

ABSTRACT: In the fiercely competitive world of today's automotive industry, Computer Aided Engineering (CAE) is playing a more and more important role in shortening the design cycle time, minimising costs and improving the product quality.

For vehicle engineering, an optimised design is to develop a light-weight, safe and durable system. A key aspect of the fatigue/durability process is to quantify the vehicle service loads in the early design phase. Within the constraints of the development time, cost and quality, the trend has been to reduce road measurement, to use more rig simulation, to increase CAE prototypes and to decrease hardware prototypes. The accuracy of the CAE durability process is mandated to achieve a robust design.

This investigation includes an application of the MSC/Nastran superelement modal method to improve the load accuracy of a short and long arm typed rear suspension. Also a comparison is made between the loads obtained using rigid body dynamics and those including MSC/Nastran flexible bodies and to quantify the influence of the elastic suspension components such as links and knuckles.

Rigid body dynamic simulation methods usually neglect the flexibility and the modal properties of the elastic components. An integration of the MSC/Nastran superelement modal method with the MDI/Adams rigid body dynamics method offers an effective tool to improve the quality of the prediction of dynamic fatigue loads in the new product development.

VIBRATION FATIGUE ANALYSIS IN THE FINITE ELEMENT ENVIRONMENT (NOT PRESENTED) (Acrobat 1.3 MB) #3799, 16 pgs.
Neil Bishop--MSC.Software Limited-United Kingdom

ABSTRACT: Fatigue damage is traditionally determined from time signals of loading, usually in the form of stress or strain. However, there are many design scenarios when the loading, or fatigue damage process, cannot easily be defined using time signals. In these cases the design engineer usually has to use a test based approach to evaluate the fatigue life of his structure or component. Or, alternatively, a frequency based fatigue calculation can be utilised where the loading and response are represented using Power Spectral Density (PSD) functions. One very important design problem, which falls into this category, is that of acoustic fatigue. However, there are also many other situations where structures are subjected to a random form of loading such as wing flutter, landing gear runway profiles, engine vibrations and so on. All of these situations can be analysed using new fatigue life estimation techniques now incorporated into the Finite Element Analysis (FEA) environment.

The theory of random vibration fatigue has seen a number of important developments over the last fifteen years. The author has been personally involved in developing new fatigue analysis theories and structural analysis techniques in the frequency domain. More recently this work has focused on the link with FEA because of the powerful design opportunities which this creates. The work has found many important practical applications. This paper presents a state of the art perspective of random vibration fatigue technology and FEA based fatigue analysis. A number of design applications are presented.

Dynamics

APPLICATION OF APPROXIMATE TECHNIQUES IN THE ESTIMATION OF EIGENVALUE QUALITY (Acrobat 582K) #1193, 18 pgs.

B. P. Wang -- The University of Texas at Arlington

S. P. Caldwell -- McDonnell Douglas Corporation

ABSTRACT: An eigenvalue quality estimate has been implemented in MSC/NASTRAN. The quality estimate is based on the eigenvalue difference from a lumped and consistent mass matrix formulation. This difference represents the error associated with the discretization of the finite element model. Normally two eigensolutions are required to compute the error estimate. However, several approximate solution techniques have been provided to efficiently compute the consistent mass matrix eigenvalues. The eigenvalue quality estimator has been implemented as a set of Direct Matrix Abstraction Programming (DMAP) alters to SOL 103 (SEMODES) of MSC/NASTRAN Version 67. Several numerical examples are provided to demonstrate the method.

APPLICATION OF MSC/DYNA IN HEAD IMPACT ANALYSIS (Acrobat 205K) #7093, 6 pgs.

Vasudeva Murthy -- Johnson Controls

Han Sankara -- Johnson Controls

ABSTRACT: The Federal Motor Vehicle Safety Standard 201 (FMVSS 201) specifies requirements to afford impact protection for occupants. It provides (see reference 1) that "when that area of the seat back that is impacted in accordance with S3.22 by a 15 pound, 6.5 inches diameter head-form at a relative velocity of 15 mph the deceleration of the head-form shall not exceed 80 g's for more than 3 ms". This paper presents the results of a head impact simulation on an automotive seat using MSC/DYNA. The results were correlated with those from an actual laboratory test. Good correlation was achieved in the deceleration time history as well as deformation of the structure. Though simulations of the crash type have been performed on entire vehicles few have been focussed on the seat to the level of detail here.

ABSTRACT: Between cylinder liner and parent bore of internal combustion engines cooling water flow is existing.

Due to the operating conditions cavitation effected by

• dynamic acoustic excitations and
• fluid flow may occur.

AVL is investigating both effects using the MSC/NASTRAN acoustic element to consider the dynamic acoustic effected cavitation and the AVL developed CFD-software FIRE for the fluid flow effects.

This paper considers only the dynamic acoustic effect. Here the calculational and experimental work is explained, which has been done till now to apply MSC/NASTRAN to cavitation calculation. In addition to this, the difficulties to per form measurements and to compare the results out of calculation and of measurements are described.

The MAC (Modal Accuracy Criterion) is used as a tool to compare measurement and calculation. The calculations are carried out as eigenmode analysis and as forced vibrations.

AN EQUIVALENT LINEARIZATION SOLUTION SEQUENCE FOR MSC/NASTRAN (Acrobat 786K) #3593, 11 pgs.

J.H. Robinson -- NASA Langley Research Center

C.K. Chiang -- Old Dominion University

ABSTRACT: A classical equivalent linearization solution procedure for the geometric nonlinear random response of structures is incorporated into MSC/NASTRAN by Direct Matrix Abstraction Programming (DMAP). The equivalent linearization solution sequence was derived from the existing Super Element Modal Frequency (SEMFREQ) response solution sequence. The definition of the equivalent linear stiffness matrix in terms of the MSC/NASTRAN differential stiffness for Gaussian random loads is presented. The required modification and inclusions to the SEMFREQ solution sequence are discussed. Results are presented for the nonlinear random response of a simple and a complex panel.

EULER BUCKLING (Acrobat 434K) #6793, 17 pgs.

Kevin E. Arden -- Newport News Shipbuilding

ABSTRACT: This paper is intended to investigate the accuracy of MSC/NASTRAN's Solution 105 for use in calculating linear elastic (Euler) buckling modes.

Column buckling, panel buckling, and stiffened panel buckling is analyzed using Euler equations and Solution 105. Comparisons and modeling recommendations are made for each type of structure.

Solution 105 provides excellent results for Euler type buckling. Panel buckling requires the use of an adequate number of elements. A convergence plot shows that four QUAD4 elements per half sine wave are necessary for accurate results.

The opinions expressed herein are those of the author and do not necessarily reflect those of Newport News Shipbuilding and Dry Dock Company.

IDENTIFICATION OF CRITICAL SPEEDS OF ROTORS ATTACHED TO FLEXIBLE SUPPORTS (Acrobat 333K) #3493, 7 pgs.

David Bella -- The MacNeal-Schwendler Corporation

Hans Hartmueller -- BMW Rolls-Royce GmbH

Dr. Karsten Muehlenfeld -- BMW Rolls-Royce GmbH

Dr. Gabriel Tokar -- BMW Rolls-Royce GmbH

ABSTRACT: It is common practice to include the gyroscopic terms for rigid rotors into the equations of motion for the calculation of critical speeds. This procedure works well for the case in which the rotors are connected directly to ground by elastic and/or damping elements. All calculated eigenfrequencies are critical speeds of the rotor. If additional degrees of freedom are included to model the actual support structure, then not all eigenfrequencies are critical speeds. Many of the calculated eigenfrequencies are simply modes of the support structure. The procedure presented allows critical speeds to be filtered from the set eigenfrequencies calculated when the support structure is included in the analysis. The methodology is used to determine the critical speeds of the BRR 700 series aerojet.

PSDTOOL - A DMAP ENHANCEMENT TO HARMONIC/RANDOM RESPONSE ANALYSIS IN MSC/NASTRAN (Acrobat 1.12MB) #3693, 25 pgs.

Alwar Parthasarathy -- Advanced Technology Systems Group, Spar Aerospace Limited

Mohamed Elzeki -- Advanced Technology Systems Group, Spar Aerospace Limited

Vivianne Abramovici -- Advanced Technology Systems Group, Spar Aerospace Limited

ABSTRACT: This Paper presents a DMAP framework called PSDTOOL that significantly enhances the scope of harmonic/random response analysis in MSC/NASTRAN. PSDTOOL addresses the case where grid-point accelerations (and displacements) form the primary output of a dynamic analysis and locates response-maxima within and across subcases and frequencies. In the common aerospace application where the input-excitation is specified as a base-motion PSD-spectrum in the form of a scalar or a diagonal matrix, PSDTOOL outputs the RMS (and RSS) responses at all the grid-points of a finite-element model as a single OLOAD-type table and locates peak RMS responses over the whole system or over individual user-defined subsystems. For facilitating high-level system design and integration, PSDTOOL includes a novel capability for computing mass-weighted average- responses at 'centers-of-mass' of system and subsystems. The goal is to automate and condense output-generation and to produce design-data with speed and confidence. PSDTOOL offers some incidental conveniences such as a conventional relative-motion formulation of base-excitation analysis and output-screening in a common co-ordinate system. The DMAP scheme is implemented as an ALTER in a DBLOCATE-restart from a mode-extraction database and the various special features are driven by non-standard PARAMeters. Extension to element-output is being envisioned.

SOLVING MODAL EQUATIONS OF MOTION WITH INITIAL CONDITIONS USING MSC/NASTRAN DMAP, PART 1: IMPLEMENTING EXACT MODE SUPERPOSITION (Acrobat 533K) #1293, 12 pgs.

Ayman A. Abdallah -- Analex Corporation

Alan R. Barnett -- Analex Corporation

Omar M. Ibrahim -- Analex Corporation

Richard T. Manella -- National Aeronautics and Space Administration

ABSTRACT: Within the MSC/NASTRAN DMAP module TRDl , solving physical (coupled) or modal (uncoupled) transient equations of motion is performed using the Newmark-Beta or mode superposition algorithms, respectively. For equations of motion with initial conditions, only the Newmark-Beta integration routine has been available in MSC/NASTRAN solution sequences for solving physical systems and in custom DMAP sequences or Alters for solving modal systems. In some cases, one difficulty with using the Newmark-Beta method is that the process of selecting suitable integration time steps for obtaining acceptable results is lengthy. In addition, when very small step sizes are required, a large amount of time can be spent integrating the equations of motion. For certain aerospace applications, a significant time savings can be realized when the equations of motion are solved using an exact integration routine instead of the Newmark-Beta numerical algorithm. In order to solve modal equations of motion with initial conditions and take advantage of efficiencies gained when using uncoupled solution algorithms (like that within TRD1), an exact mode superposition method using MSC/NASTRAN DMAP has been developed and successfully implemented as an enhancement to an existing coupled loads methodology at the NASA Lewis Research Center.

SOLVING MODAL EQUATIONS OF MOTION WITH INITIAL CONDITIONS USING MSC/NASTRAN DMAP, PART 2: COUPLED VS. UNCOUPLED INTEGRATION (Acrobat 581K) #1393, 10 pgs.
Alan R. Barnett -- Analex Corporation
Omar M. Ibrahim -- Analex Corporation
Ayman A. Abdallah -- Analex Corporation
Timothy L. Sullivan -- National Aeronautics and Space Administration

ABSTRACT: By utilizing MSC/NASTRAN DMAP in an existing NASA Lewis Research Center coupled loads methodology, solving modal equations of motion with initial conditions is possible using either coupled (Newmark-Beta) or uncoupled (exact mode superposition) integration available within module TRD1. Both the coupled and newly developed exact mode superposition methods have been used to perform transient analyses of various space systerns. However, experience has shown that in most cases, significant time savings are realized when the equations of motion are integrated using the uncoupled solver instead of the coupled solver. Through the results of a real-world engineering analysis, advantages of using the exact mode superposition methodology are illustrated.

SPACE STATION SOLAR ARRAY POINTING SYSTEM CONTROL/STRUCTURE INTERACTION STUDY USING CO-ST-IN FOR MODAL REDUCTION (Acrobat 976K) #6893, 22 pgs.

Tarun Ghosh -- Rockwell International Corporation

Benigno Muniz Jr. -- Rockwell International Corporation

Joseph Cheng -- Rockwell International Corporation

Marsha Nall -- NASA Lewis Research Center

ABSTRACT: The control/structure interaction problem of orienting the Space Station Freedom (SSF) PhotoVoltaic arrays is solved to achieve desired system pointing performance using the Beta Gimbal Drive Mechanism. The vibration modes of the on-orbit SSF Stage Configuration 17 are calculated using MSC/NASTRAN finite element models which presently comprise a total of 250,000 degrees of freedom. In-house Direct Matrix Abstraction Programs and post-processors are developed for more efficient and accurate Craig-Bampton modal reduction with geometric stiffening and either modal displacement or modal acceleration data recovery. Structural Dynamic Research Corporation's CO-ST-IN post-processor is used to rank the vibration modes for control system analysis. The problem of solving an actual case of ranking modes using CO ST-IN for large-scale SSF application is illustrated. Examples of calculated control system response including the effects of reduced flexible mode dynamics are shown.

SSF FLEXIBLE MULTI-BODY CONTROL/STRUCTURE INTERACTION SIMULATION (Acrobat 711K) #1593, 19 pgs.

Timothy T. Cao -- NASA JSC/ES

Huang-Tsang Chang -- DYNACS Engineering Co.

Tuyen Hua -- NASA JSC/EG2

ABSTRACT: For a large structure with the size of Space Station Freedom, it is important to consider the structural flexibity in the dynamics and control simulation. Conventionally, structural flexibility is obtained from the MSC/NASTRAN structural models. The interface between MSC/NASTRAN structural models and multi-body simulation programs is achieved by a flex-preprocessor. This approach becomes formidable as the size of finite element models grows with the evolution of SSF structures. The use of superelement and Craig -Bampton reduction in MSC/NASTRAN introduces difficulty in interfacing MSC/NASTRAN structural models with the Station/Orbiter Multi-Flex- Body Berthing Analysis Tool (SOMBAT), a program developed at JSC to perform flex-multibody dynamics and control simulation. To handle the dynamic reduction approach in MSC/NASTRAN, the flex-preprocessor in SOMBAT has been modified, and appropriate DMAP sequences have been developed. This paper presents the enhanced capability of SOMBAT for the space station freedom dynamics and control simulation. The procedure is validated through control structure interaction simulation for space station stage two scenarios.

A SUPEREFFICIENT, MSC/NASTRAN-INTERFACED COMPUTER CODE SYSTEM FOR DYNAMIC RESPONSE ANALYSIS OF NONPROPORTIONALLY DAMPED ELASTIC SYSTEMS (Acrobat 748K) #1493, 16 pgs.

Rong C. Shieh -- MU, Inc.

ABSTRACT: With the emphasis on frequency response analysis case, development of the title computer code capability and application of the latter in evaluation of the computational efficiency of the MSC/NASTRAN code itself in the dynamic structural response analysis of nonproportionally . damped elastic systems are made in this study. In this system, MSC/NASTRAN is used mainly for physical or modal structural (mass, damping, and stiffness) matrix assembling. The newly developed CMODEAN (Complex MOde/DEcoupling ANalysis) module uses the structural matrices as input for complex normal modes (state eigenmodes) calculation and equations of motion decoupling. Computational efficiency of CMODSTAN over MSC/NASTRAN for frequency response analysis of nonproportionally damped systems is demonstrated by an example problem with 225 dynamic degrees of freedom.

Dynamics Analysis

ACCURATE ENFORCED MOTION ANALYSIS USING MSC/NASTRAN SUPERELEMENTS

(Acrobat 666K) #2594

Christopher C. Flanigan -- SDRC Engineering Services Division, Inc.

ABSTRACT: The standard approach for performing an enforced motion analysis in MSC/NASTRAN uses very large masses and forces to obtain the desired motion at selected locations. This approach can lead to inaccurate results if the large masses are too large or too small.

An alternate approach for enforced motion analysis is presented in this paper. The alternate method uses the Craig-Bampton superelement capability in MSC/NASTRAN to form the required matrices for a direct solution of the equations of enforced motion. The need for large masses is eliminated, resulting in improved accuracy. In addition, the enforced motion analysis is performed directly, eliminating the need for Lagrange multipliers.

A rigid format alter for performing the new enforced motion analysis method is included in the paper. An example problem is presented to demonstrate the new method and to illustrate some of the pitfalls of enforced motion analysis.

ACOUSTIC SENSITIVITY ANALYSIS USING BOUNDARY ELEMENTS AND STRUCTURAL DYNAMIC RESPONSE (Acrobat 737K) #0794, 14 pgs.
Nickolas Vlahopoulos -- Automated Analysis Corporation
S.T. Raveendra -- Automated Analysis Corporation
Chris Mollo -- Automated Analysis Corporation

ABSTRACT: Structural/acoustic sensitivity analysis can provide information on how structural design modifications can affect the noise emitted from vibrating structures. MSC/NASTRAN S0L108 and SOLl1 can be used to compute structural dynamic frequency response sensitivities. This information can be coupled with Boundary Element (BE) results to derive the acoustic sensitivity with respect to structural design variables.

In this work two BE formulations, the Direct and Indirect, have been coupled to MSC/NASTRAN design sensitivity results to compute the acoustic sensitivity with respect to structural design variables. The theoretical background of the coupling algorithm is presented along with some examples of noise prediction in interior and exterior noise radiation.

 

AEROELASTIC MODELLING OF AN AIRPLANE WITH STAND-BY ACTUATOR USING MSC/NASTRAN FOR FLUTTER ANALYSIS (Acrobat 481K) #3394, 16 pgs.

Yan Mursal -- Pt.IPTN/Indonesia Aircraft Industry Ltd.

Moh. Risdaya Fadil -- Pt.IPTN/Indonesia Aircraft Industry Ltd.

ABSTRACT: The aircraft control surfaces that were considered in this paper are driven by a pair of hydraulically powered servo actuators. One actuator is normally in an active mode and the other is normally in a stand-by mode. This paper describes an aeroelastic modeling technique where a control System has two hydraulic failures, the active mode actuator is failed (e.g. a structural disconnect) and no hydraulic power comes to the stand-by mode actuator. In this situation the stand-by mode acts as a hydraulic damper.

In the failure condition, the stand-by actuator must provide sufficient damping in order the airplane still maintain flutter free condition. To perform the aeroelastic analysis of the System, the generalized mass, stiffness and damping of the plant (airplane) equation must be modified. These tasks were done using the combination of EPOINT, TF MSC/NASTRAN bulk data entry and DMAP. The EPOINT entry was used to add one generalized coordinate. In this case it is due to the moment of the actuator introduced to the airplane. The Nastran TF bulk data was used to introduce the diagonal terms of the MHH, BHH and KHH matrices. A small DMAP routine was created to add off-diagonal terms of these matrices and to perform the analysis automatically. The calculation was done using SOL 145. Some results are presented as an example and also compared with another method.

ANALYSIS AND MODAL SURVEY TEST INTELSAT VIIA DEPLOYED SOLAR ARRAY (Acrobat 469K) #2794, 12 pgs.
K. C. Jiang -- Space Systems/Loral
R. Gahart -- Space Systems/Loral

ABSTRACT: A nonlinear normal modes analysis and a modal survey test have been performed to determine the frequencies and mode shapes of a large flexible deployed solar array for the Intelsat VIIA series communication satellites under production at Space Systems/Loral. Test parameters such as gravity, air mass and test fixture stiffness are included in the analysis. MSC/NASTRAN Solution 105 was used to generate the gravitational stiffness due to 1-g gravity and Solution 103 was used to calculate the frequencies. A DMAP Alter was updated for MSC/NASTRAN Version 67 to combine the Solution 105 gravitational stiffness matrix and Solution 103 structural stiffness matrix. The modal survey test was performed to measure frequencies and mode shapes for correlation with the analytical results. The deployed solar array was hung vertically. The solar array was pulled and released suddenly to excite transient vibrations. The decaying vibration response was measured and analyzed to deduce the frequencies. The test results show good correlation with the predictions.

DYNAMIC ANALYSIS BY THE FOURIER TRANSFORM METHOD WITH MSC/NASTRAN (Acrobat 1.07MB) #1095, 23 pgs.
Dean Bellinger--The MacNeal-Schwendler Corporation

ABSTRACT: This paper briefly describes the Fourier transform capability using MSC/NASTRAN, demonstrates its application to several examples without including any aerodynamic effects and provides an explanation for general application within MSC/NASTRAN.

The Fourier transform capability in MSC/NASTRAN allows transient response analysis to be performed with a frequency response solution. Time dependent loads are transformed into the frequency domain and all frequency dependent calculations are performed with the modal frequency response modules. The frequency response results are then transformed back into the time domain with an inverse Fourier transform module as an integral part of the solution sequence.

Fourier transform methods have been implemented in MSC/NASTRAN to solve the equations of motion for the aeroelastic response of fixed wing aircraft. This capability is vital to this analysis technique because the unsteady aerodynamic matrices are calculated in the frequency domain. The Fourier transform method is easily accessible with SOL 146 and the aerodynamic input becomes unnecessary when a DMAP alter avoids the aeroelastic coupling. The forward Fourier transform is also included in the frequency response analysis solution sequences, e.g., SOL 108. This provides a method for calculation of Fourier series coefficients from a function of time as specified on any combination of TLOAD1 and/or TLOAD2 bulk data entries.

DYNAMIC DESIGN ANALYSIS METHOD (DDAM) USING MSC/NASTRAN (Acrobat 314K) #3194, 10 pgs.
Pam Barber -- Newport News Shipbuilding
Kevin Arden -- Newport News Shipbuilding

ABSTRACT: Components on naval ships are currently analyzed for shock loads due to hostile attacks using the Dynamic Design Analysis Method (DDAM). DDAM estimates the dynamic response of a component to a beam excitation resulting from the motion of the ship's hull.

This paper gives a brief description of the history and use of DDAM, presents an overview of the mathematics, and demonstrates the use of DDAM in designing a typical submarine component.

The demonstration problem uses MSC/NASTRAN for the dynamic analysis and modal summations, and shows how DDAM can be performed using MSC/NASTRAN Solution 103.

The opinions herein are that of the authors' and do not necessarily represent the opinion of Newport News Shipbuilding.

AN EFFICIENT PROCEDURE FOR DATA RECOVERY OF A CRAIG-BAMPTON COMPONENT
(Acrobat 506K) #2694, 15 pgs.
Edward T. Tong -- Rockwell International
Craig C.J. Chang -- Rockwell International

INTRODUCTION: Dynamic analyses of large and complex space structures are generally performed using the modal approach. Component modal syntheses are used frequently so that various companies, each designing their own hardware, can supply the component models to the integrator for System dynamic analysis. Of the various techniques of component modal reduction, the Craig-Bampton procedure is most commonly used. The deliverable data usually consists of the component Craig-Bampton generalized mass and stiffness matrices, and the Craig-Bampton transformation matrix. Linear Transformation Matrices (LTMs) associated with the model generated by the component companies are used to facilitate data recovery. Sizes of these LTMs range from a few key bad indicators which are of interest to the integrator to an extensive data recovery set that drives the component's design. Component modal synthesis and data recovery therefore form a tandum in dynamic analysis of large space structures. The two widely used procedures to compute the LTMs are the mode displacement approach and the mode acceleration approach. Although the mode acceleration approach is generally perceived to be an improvement over the mode displacement approach, there are considerations when choosing a data recovery method.

This paper will formulate a simplified procedure to construct the Craig-Bampton LTMs using either the mode acceleration approach or the mode displacement approach. The procedure will be formulated for the general case of statically indeterminant structures. Further simplification can be made for statically determinant Craig-Bampton components. A general purpose DMAP routine of MSC/NASTRAN version 67 encompassing the tandum has been implemented. Sample problems to demonstrate the procedure with the DMAP are included. Although the DMAP is written for a Craig Bampton component, it can be extended to a general modally reduced model.

A disadvantage of the mode acceleration recovery is the costly computation to construct the LTMs when an applied load at the interior set is present. One of the recent applications is the plume implingement on the solar arrays during Shuttle docking with the Space Station. This paper will discuss a cost saving technique and suggest an approach which reduces cost by utilizing a 'mixture' of the two approaches.

MODEL REDUCTION AND MODEL CORRELATION USING MSC/NASTRAN (948K) #0895, 16 pgs.
Y T. Chung--McDonnell Douglas Aerospace Company-West

ABSTRACT: Dynamic mathematical models used in the launch vehicle verification loads analysis for predicting the flight loads and assessing the structural integrity are required to be test- verified. The test-verified model is usually developed after conducting a modal survey on a structural test article and correlating the measured frequencies and mode shapes with the analytical prediction. However, it is not practical to instrument a test article in all degrees of freedom corresponding to those of the analytical model. Therefore, it is extremely difficult to correlate each analytical mode shape with the measured data. A systematic approach using MSC/NASTRAN version 67.5 direct matrix algorithm program (DMAP) is developed to minimize the effort for test-analysis model reduction and correlation. Four model reduction methods are available and can be selected by the user to generate a test analysis model (TAM). The size of the TAM is equal to the number of accelerometers mounted on the test article. This provides a direct comparison of the analytical prediction with the measured data. The orthogonality matrix, the cross-orthogonality matrix, and the modal assurance criteria between the analytical modes and the test modes are computed automatically by the DMAP to assess the correlation of the TAM with the modal test results. An analytical model is test-verified if the cross-orthogonality matrix and the frequency comparison meet the launch vehicle payload verification requirements . An example is presented to demonstrate the implementation of this MSC/NASTRAN DMAP for payload model verification.

SHAKE TEST SIMULATION USING MSC/NASTRAN (Acrobat 744K) #3294, 21 pgs.

Randal H. Visintainer -- Ford Motor Company

Farhang Aslani -- Automated Analysis Corporation

ABSTRACT: Advances in Computer-Aided Testing technology have led to the Simulation of Service Operation and test track loads in the laboratory. The controlled environment of the lab creates an ideal Situation for attempts to simulate the lab test. Furthermore, the concept of up-front engineering using analytical prototype has pushed the demands on the CAE analysts to develop methodology to simulate operating conditions, durability events, and laboratory tests. To address this need, the frequency response solution (SOL 111) of MSC/NASTRAN is used to simulate the vehicle shake test of a heavy truck. The displacement-controlled lab test was performed between the frequency range of 20 to 50 Hertz (Hz). The MSC/NASTRAN simulation of the test and the correlation between the test and analysis results revealed several important points that should be considered in a computer simulation using the analytical prototype.

SIMULATION OF PROVING GROUND EVENTS FOR HEAVY TRUCK CABS USING ADAMS, MSC/NASTRAN, and P/FATIGUE (Acrobat 862K) #0594, 19 pgs.

Farhang Aslani -- Automated Analysis Corporation

Manicka Yatheendar -- Automated Analysis Corporation

Randal H. Visintainer -- Ford Motor Company

David S. Rohweder -- Ford Motor Company

Juan Lopez de Alda -- Mechanical Dynamics Inc.

ABSTRACT: The concept of up-front engineering using analytical prototype has pushed the demands on the CAE analysts to develop methodologies which simulate operating conditions, proving ground events, and laboratory tests well ahead of the availability of structural prototypes of the vehicle. One purpose of such analysis is to provide fatigue life prediction at an early stage of the design to permit the incorporation of design modifications prior to initial tooling release. The stress history resulting from the operation of the vehicle on the proving ground events can be simulated by enforcement of the profile of proving ground events using transient analysis in MSC/NASTRAN However, some of the proving ground events for heavy truck cabs include tire patch displacement of 12 inches that can not be simulated in MSC/NASTRAN directly. A methodology has been developed for use of the ADAMS vehicle model which provides accelerations at the cab mounts under those events. The acceleration response from the ADAMS model was used to perform transient analysis in MSC/NASTRAN to predict the time history of stresses in the cab. The time history of the stresses are input to the P/FATIGUE program to predict fatigue life of the structure under specific proving round events.

A STUDY ON THE ANALYSIS AND IMPROVEMENT OF THE ACOUSTIC CHARACTERISTICS OF THE MUFFLER WITH COMPLEX GEOMETRY (Acrobat 466K) #0694, 10 pgs.

Jin-Yong Mo -- SAMSUNG ELECTRONICS Co

Man-Sun Huh -- SAMSUNG ELECTRONICS Co

Jung-Rae Kim -- SAMSUNG ELECTRONICS Co

Heui-Jong Kang -- SAMSUNG ELECTRONICS Co

Sang-Kyoung Oh -- SAMSUNG ELECTRONICS Co

ABSTRACT: An acoustic transmission loss analysis method for mufflers with complex geometry is developed using MSC/NASTRAN on the basis of acoustic-structural analogy and two-microphone method. In this study, mufflers with simple and complex shapes are analyzed using this method and compared with theoretical and experimental results for verification.

Applying this method to design of suction muffler of reciprocating compressor, we could obtain 4dB(A) total noise reduction, especially more than 10dB(A) noise reduction at 500Hz.

VIBROACOUSTICS RANDOM RESPONSE ANALYSIS METHODOLOGY (Acrobat 566K) #0995, 11 pgs.

Gregory J. Michels--Eastman Kodak Company

ABSTRACT: The theory, application, and assumptions of a dynamic modal analysis based technique are presented to familiarize users with a method to use MSC/NASTRAN to determine the random response of a structure subjected to acoustic loads. Emphasis is placed on computing the mechanical response of a structure due to applied acoustic loads with worst case spatial correlation. MSC/NASTRAN solutions 101, 103 and 111 with the random response processor are used in the analysis method.

Electromagnetics

EDDY CURRENT SIMULATIONS FOR THE SSCL LOW ENERGY BOOSTER CAVITY (Acrobat 420K) #1693, 11 pgs.

Y Goren -- Superconducting Super Collider Laboratory

L. Walling -- Superconducting Super Collider Laboratory

ABSTRACT: Eddy currents are developed in the tuner of the Superconducting Super Collider Low Energy Booster (LEB) cavity during the LEB frequency sweep. The two main difficulties created by the eddy currents are excessive tuner-surface heating, and more important, a reduction in the time response of the tuner. We present a detailed analysis of the eddy currents for various tuner designs. The analysis has been done using 2D and 3D time-domain finite element codes: PE2D by Vector- Field and MSC/EMAS by the MacNeal-Schwendler Corporation. Non-linear analysis was performed utilizing B-H curves. The codes have been bench marked analytically and by using measured data for different slotted pillbox structures.

INDUCTION FURNACES: INTEGRATED MSC/EMAS, MSC/XL, AND MSC/NASTRAN ANALYSIS (Acrobat 873K) #2093, 25 pgs.

Vern D. Overbye -- STM Consulting, Inc.

Glenn H. Stalker -- STM Consulting, Inc.

Scott M. Schaefer -- STM Consulting, Inc.

Roy H. VanderHeiden -- STM Consulting, Inc.

S. Rajendran -- Mobil Solar Energy Corporation

ABSTRACT: A generic induction-heated high temperature furnace is modeled using MSC/EMAS to determine power loss density distribution in a 3-D segment with a cylindrical coil surrounding the furnace. MSC/XL is used to display color plots of furnace induced power loss density as well as magnetic flux density within furnace and coil components. MSC/XL is next used to generate internal heat generation records for an MSC/NASTRAN nonlinear steady state thermal analysis using a full radiation matrix (assuming radiation shields closely spaced). An alternative to full radiation analysis is presented using a theory developed for radiation - equivalent convection. The two methods are compared, and furnace temperature contours are presented using MSC/XL. Results of a C-language program are presented to calculate heat flux and display the results graphically. Finally, the authors present several recommendations for forthcoming releases of MSC/NASTRAN to improve user friendliness.

MAGNETIC SENSOR DEVELOPMENT USING FINITE ELEMENT ANALYSIS (Acrobat 990K) #1893, 18 pgs.

T.J. Wagener -- Honeywell Systems and Research Center

James R. Campbell, Jr. -- Honeywell Systems and Research Center

James E. Lenz -- Honeywell Systems and Research Center

ABSTRACT: Magnetic finite element analysis has proven to be valuable in the research and development of magnetic sensors and actuators. The emphasis of this research is not entirely on design detail, but also on the basic magnetics and material properties on which devices are based. Examples of this research include: 1) magnetic shielding for ring-laser gyros, 2) magnetic force modeling for accelerometers based on the type-two high-temperature superconductors, 3) proximity and position sensors for aircraft applications, and 4) the dynamics of and losses in electromagnetic actuators and bearings. These examples represent the wide diversity of magnetic problems faced by researchers, and demonstrate how solutions to these problems range from simple two-dimensional models to larger and more complicated three-dimensional models.

MSC/EMAS NONLINEAR TRANSIENT ANALYSES OF MULTITURN COILS WITH ATTACHED CIRCUITS (Acrobat 622K) #2293, 14 pgs.

John R. Brauer -- The MacNeal-Schwendler Corporation

Charles R. Figer, Jr. -- The MacNeal-Schwendler Corporation

ABSTRACT: MSC/EMAS can be used to model multiturn nonlinear coils with attached circuits. The circuits are modeled by 0D finite elements, which can be attached to 1D line elements that represent multiturn windings. The 1D elements can then be MPCd to the 3D or 2D finite element model containing nonlinear magnetic material. The complete finite element model is analyzed by nonlinear transient Solution 305. Example computations of time-varying currents and electromagnetic fields are shown for an inductor, a transformer, and an induction motor. The induction motor solution is shown to be aided by the new ADAPT nonlinear transient method that is available in Version 2.5.

3D NONLINEAR MAGNETIZATION STUDIES OF THIN AMORPHOUS RIBBONS (Acrobat 558K) #1993, 10 pgs.

Richard L. Copeland -- Sensormatic Electronics Corporation

Markus B. Kopp -- Sensormatic Electronics Corporation

ABSTRACT: Three-Dimensional analysis of a thin amorphous magnetic ribbon is studied using MSC/EMAS. A uniform static magnetic field is applied at various angles with respect to a nonlinear isotropic magnetic ribbon by using HSURF loads at certain boundary grid points. Different finite element meshes were examined in terms of generating a very uniform magnetic field to a region in the model center representing the thin amorphous ribbon. A simple uniform mesh produced a more uniform field than a mesh with much more refinement at the center. The importance of the proper boundary conditions along with the HSURF loads are discussed. The results clearly demonstrate the expected closure field around the ribbon and help in understanding the magnetization distributions in and around thin magnetic regions under an applied uniform field.

USING FINITE ELEMENT SOFTWARE TO PREDICT EMC PERFORMANCE FROM ELECTRICALLY SMALL SOURCES (Acrobat 555K) #1793, 9 pgs.

Mark L. Markel -- General Motors Corporation

ABSTRACT: A major limit of the finite element method in the past has been its relative difficulty to model three-dimensional open configurations found in EMC problems. MSC/EMAS with its open boundary elements now enables problems to be solved in three-dimensions that were previously considered solvable only with Method of Moment (MoM) codes and other techniques. MSC/EMAS is used here to accurately compute radiation fields from an electrically small source (less than a wavelength) that was previously solved with method of moments codes, and then to analyze printed circuit radiation that cannot easily be predicted by MoM.

USING MSC/EMAS IN STIMULATING A PARALLEL MICROSTRIP TRANSMISSION LINE (Acrobat 298K) #2193, 9 pgs.

Markus B. Kopp -- Sensormatic Electronics Corp.

Vichate Ungvichian, Ph.D. -- Florida Atlantic University

Richard L. Copeland, Ph.D. -- Sensormatic Electronics Corp.

ABSTRACT: During a crosstalk study of two parallel and coplanar microstrip lines having identical width and thickness, the MSC/EMAS code was used to calculate the total current flows on the receptor line, and demonstrate the relationship between substrate height and crosstalk. The frequency used in the simulations was 200 MHz. One microstrip trace was driven by a 100 mA ideal current source and terminated with a 50 ohm resistive load. The other trace was terminated at both ends by two 50 ohm loads.

MSC/EMAS produced results that are accurate to within 4 percent of the closed form solution. It also clearly demonstrated that the magnitude of crosstalk, as a function of substrate height, asymptotically approaches a final value.

Electronics

STRUCTURAL ANALYSIS OF KA-BAND GIMBALED ANTENNAS FOR A COMMUNICATIONS SATELLITE SYSTEM (Acrobat 192K) 1996, 15 pgs.
Hong Su--COM DEV Ltd.

ABSTRACT: This paper presents the FE modeling, structural analysis and test validation, of the Ka-band gimbaled antennas developed by COM DEV Ltd. for a satellite communications system. The modeling methods and dynamic stress analysis approaches are highlighted in order to achieve a compromise of the technical accuracy, computational cost and effectiveness requirements. The antenna launch-lock mechanisms with small clearance are modeled as equivalent linear springs (CELAS2's) by using the iteration technique. A linearized and locally remeshed assembly model is then effectively used to perform dynamic and stress analyses, by employing the MSC/NASTRAN programs. It is shown that the analysis results of the nonlinear gimbaled antennas, in terms of major modal frequencies, sine and random acceleration response, correlate the measured qualification test data very well.

3D MSC/EMAS SIMULATION OF A THREE PHASE POWER TRANSFORMER BY MEANS OF ANISOTROPIC MATERIAL PROPERTIES (Acrobat 544K) 1996, 11 pgs.
Dr. E. Schmidt--University of Technology, Vienna
S. Ojak--University of Technology, Vienna

ABSTRACT: This paper deals with the MSC/EMAS simulation of a three phase power transformer using a 3D finite element model. The most important part of the presented simulation is the modelling of the multiturn windings and the iron core by means of anisotropic material properties. Characteristic calculation results with the derived transformer model will show that the modelling technique is practicable for many low frequency applications.

Elements

ANALYSIS OF SHELL STRUCTURES USING MSC/NASTRAN'S SHELL ELEMENTS WITH SURFACE NORMALS (Acrobat 643K) #2695, 18 pgs.
C.C.Hoff--MacNeal-Schwendler Corporation
R.L.Harder--MacNeal-Schwendler Corporation
G.Campbell--Ford Motor Company
R.H.MacNeal--MacNeal-Schwendler Corporation
C.T.Wilson--MacNeal-Schwendler Corporation

ABSTRACT: MSC/NASTRAN's lower order shell elements TRIA3, QUAD4, TRIAR, and QUADR are some of the most frequently used shell elements in the finite element market. The performance and quality of MSC's shell elements have been tested over a long period of time, but there is still potential for improvement. It has been reported that moderately thick shell elements with transverse shear flexibility are too soft in twist for cases where additional bending and membrane forces are active. In addition, spurious out-of-plane rotations have been reported. The behavior occurred only in very few practical problems and it did not appear in the MacNeal-Harder standard test problems. Unique surface normals at grid points are introduced in MSC/NASTRAN Version 68.2 to improve the behavior of the shell elements. The improvement of shells with normals is shown.

COMGEN-BEM: BOUNDARY ELEMENT MODEL GENERATION FOR COMPOSITE MATERIALS MICROMECHANICAL ANALYSIS (Acrobat 1.88MB) #2395, 20 pgs.
Robert K. Goldberg--NASA Lewis Research Center
Michele D. Comiskey--University of Akron

ABSTRACT: COMGEN-BEM (Composite Model Generation - Boundary Element Method) is a program developed in MSC/PATRAN's PATRAN Command Language (PCL) which generates boundary element models of continuous fiber reinforced laminated and woven composites at the micromechanical (constituent) scale. Through the use of menus and forms, the user enters a few simple parameters such as fiber volume fraction, fiber diameter, mesh density, material properties, fiber rotation information and load and boundary condition data. From the user defined parameters, a complete boundary element model is automatically generated. Once the model is generated, the user can invoke a provided translator to convert the model information into an appropriate boundary element analysis input format. This program demonstrates the ability of MSC/PATRAN and PCL to simplify the parametric generation of boundary element models in general, and composite micromechanical models in particular.

AN INTERFACE ELEMENT FOR GLOBAL/LOCAL AND SUBSTRUCTURING ANALYSIS (Acrobat 1.48MB) #2595, 20 pgs.
Jerrold M. Housner--NASA Langley Research Center
Mohammad A. Aminpour--Old Dominion University
Carlos G. Davila--National Research Council Associate
John E. Schiermeier--MacNeal-Schwendler Corporation
W. Jefferson Stroud-- NASA Langley Research Center
Jonathan B. Ransom--NASA Langley Research Center
Ronnie E. Gillian--NASA Langley Research Center

ABSTRACT: NASA and the MacNeal Schwendler Corporation have entered into a cooperative agreement to further the development of Interface Technology for finite element modeling. This new technology enables incompatibly meshed models to be accurately joined together even when their grid points do not coincide. Until recently, this technology was being developed solely by NASA. To improve technology transfer and to ensure relevancy of NASA developments in this area, NASA and MSC will work together to extend the capability in an experimental version of MSC/NASTRAN. This paper describes the Interface Technology, demonstrates its capabilities and value, and reviews the activity of the NASA/MSC joint venture.

USE OF MSC/NASTRAN GENERAL ELEMENTS IN COMPLEX STATIC PROBLEMS (Acrobat 855K) #2495, 19 pgs.
Mitchell L. Greenberg--Spar Space Systems

ABSTRACT: This paper shall explore uses of MSC/NASTRAN general (GENEL) elements. Basic stiffness matrix concepts as pertaining to GENEL formulation will be discussed, and techniques to reduce large linear static structures to a single GENEL connected at the boundary GRIDs shall be presented. The methods herein provide an alternative to and supplement the capabilities of SuperElements for manipulating and modelling sub-components.

Fatigue Analysis

ANALYTICAL FATIGUE LIFE ASSESSMENT OF VIBRATION INDUCED FATIGUE DAMAGE (Acrobat 786K) #1895, 17 pgs.

NWM Bishop--University College London (UCL)

LW Lack--nCode International

T Li--Ford Motor Company

SC Kerr--University College London (UCL)

ABSTRACT: Vibration testing of components using accelerated test tracks or laboratory simulators is widely used in automotive design, as is fatigue testing for reliability. Furthermore, there are many common features between these two disciplines. However, problems often arise when engineers who are skilled in one field have to use techniques and concepts more generally used in the other. One example of such a situation concerns the use of frequency domain descriptions of structural response, which are commonplace in vibration testing for ruggedness, for computing the fatigue life or reliability of the same component. Many engineering applications, such as offshore engineering and wind turbine engineering, have already seen the benefits of using frequency domain fatigue tools for reliability assessment. The purpose of this paper is to assess the benefits of frequency domain fatigue analysis by comparison with a more conventional time series transient fatigue analysis. A typical automotive component has been analysed using MSC/NASTRAN and MSC/PATRAN FATIGUE in both the time domain (using a transient time history analysis) and in the frequency domain using spectral fatigue analysis techniques. Probability density functions and fatigue lives computed using the output from these two different approaches show good agreement.

FATIGUE ANALYSIS USING RANDOM VIBRATION (Acrobat 389K) #1795, 8 pgs.
H. L. Schwab--Ford Motor Company
J. Caifrey--F.E.Tools
J. Lin--Ford Motor Company

ABSTRACT: The structural requirements for components are often defined in terms of random vibration specifications. However most present analysis methods are limited to approximating the structural capabilities by using static equivalent loads . In order to achieve correlation between the requirements and the analysis, an MSC/NASTRAN post-processing program has been written to calculate the fatigue life of a structure based on a random vibration input. This program is explained with a correlating example.

FINITE ELEMENT BASED FATIGUE ANALYSIS (Acrobat 13.3 MB) #1298, 15 pgs.
Dr. NWM Bishop and Alan Caserio--MSC

ABSTRACT: Fatigue analysis procedures for the design of modern structures rely on techniques, which have been developed over the last 100 years or so. The first accepted technique was the S-N or stress-life method generally given credit to the German August Woehler for his systematic tests done on railway axles in the 1870's. Initially these techniques were relatively simple procedures, which compared measured constant amplitude stresses (from prototype tests) with material data from test coupons. These techniques have become progressively more sophisticated with the introduction of strain based techniques to deal with local plasticity effects. Nowadays, variable stress responses can be dealt with. Furthermore, techniques exist to predict how fast a crack will grow through a component, instead of the more limited capability to simply predict the time to failure. Even more recently techniques have been introduced to deal with the occurrence of stresses in more than one principal direction (multi-axial fatigue) and to deal with vibrating structures where responses are predicted as PSD's (Power Spectral Density's) of stress. Even more recently researchers have addressed the requirements for the design of specific components such as spot welds. All of these techniques were developed outside of the Finite Element environment. However, they have now been implanted into many FE based analysis programs, the best known of which is MSCFATIGUE. The FE environment introduces additional considerations relating to how input data is processed and how fatigue life, or damage, results are post processed. This paper will deal with the issues associated with how fatigue techniques can be incorporated into the FE environment. Modern examples of FE based fatigue design will be included.

A LIFE PREDICTION ALGORITHM IMPLEMENTED IN P3 USING PCL (Acrobat 1.01MB) #1995, 11 pgs.

Matthew E. Melis--NASA Lewis Research Center

Joseph A. Ogonek--Analex Corporation

ABSTRACT: A life prediction methodology is implemented in P3 through a computer program, Probable Cause, written in Patran Command Language (PCL). The software uses finite element analysis data, and probabilistic material parameters to predict the component life and probability of survival for the analysis model. Probable Cause is imbedded in P3 and is accessed through a graphical user interface called from the main menu bar.

The theory in Probable Cause is briefly outlined in this paper and its use is demonstrated with a finite element analysis of a jet engine turbine disk. The usefulness of PCL in accomplishing a task of this nature is shown and the lessons learned in the development process are discussed.

A Life Prediction Algorithm Implemented in P3 Using PCL 1.

A SPOT-WELD FATIGUE ANALYSIS MODULE IN THE MSC/FATIGUE ENVIRONMENT (Acrobat 256K) 1996, 13 pgs.
Peter Heyes--nCode International Limited
Mikael Fermér--Volvo Car Corporation

ABSTRACT: A software system has been developed in the MSC/FATIGUE [1] environment which permits fatigue life predictions to be made for automotive spot-welds joining two steel sheets. The method uses bar element forces to calculate the "structural stresses" in each spot-weld nugget and the adjacent sheets using the methodology described by Rupp, Störzel and Grubisic [2]. The system described here extends this general method to support the use of dynamic stresses derived from road load data, using either a quasi-static or transient approach to stress history determination. The method is geometry independent and suitable for application to large models (because it does not require local mesh refinement). The system provides a convenient way for users of MSC/PATRAN [3], MSC/NASTRAN [4] and MSC/FATIGUE to predict the location and life of fatigue sensitive spot-welds.

A STEPWISE APPROACH FOR FATIGUE EVALUATION OF ENGINE ACCESSORIES PRIOR TO PROTOTYPING USING HYBRID MODELLING TECHNOLOGY (Acrobat 1.7MB) 1996, 12 pgs.
L. Gielen--LMS International
M. Brughmans--LMS International
C. Petellat--MACK

ABSTRACT: To improve the prediction of fatigue performance of automotive components in their early design stage, the operational boundary conditions and loads have to be modelled. The use of an experimental description of the dynamic behaviour of existing parts of the final assembly is proposed. 3 different methods to couple these measured data to the MSC/NASTRAN model are presented. The first method aims at direct application of frequency dependent boundary conditions to the free-free FE-model. Next, the coupling of MSC/NASTRAN model model structure is discussed. The third method uses impedance coupling algorithms to predict transfer function matricies after assembly starting from the Frequency Response Functions (FRF) calculated by MSC/NASTRAN at the interface DOF's of the compoment and measured interface FRF's on the carrying structure. The methods are applied to estimate resonance frequencies of a newly designed alternator support when bolted to a truck engine. Experimental evaluation data are measured on a prototype support. To minimize bias errors, the original MSC/NASTRAN model is correlated and tuned prior to the application of coupling algorithms, based on experimental modal analysis on the prototype component.

VIBRATION FATIGUE ANALYSIS IN THE FINITE ELEMENT ENVIRONMENT (Acrobat 4.3 MB) #1398, 15 pgs.
Dr. Neil Bishop and Alan Caserio--MSC

ABSTRACT: Fatigue damage is traditionally determined from time signals of loading, usually in the form of stress or strain. However, there are many design scenarios when the loading, or fatigue damage process, cannot easily be defined using time signals. In these cases the design engineer usually has to use a test based approach to evaluate the fatigue life of his structure or component. Or, alternatively, a frequency based fatigue calculation can be utilized where the loading and response are categorised using Power Spectral Density (PSD) functions.

One very important design problem, which falls into this category, is that of acoustic fatigue. However, there are also many other situations where structures are subjected to a random form of loading such as wing flutter, landing gear runway profiles, engine vibrations and so on. All of these situations can be analysed using new fatigue life estimation techniques now incorporated in MSC/FATIGUE.

The theory of random vibration fatigue has seen a number of important developments over the last fifteen years. The authors have been personally involved in developing new fatigue analysis theories and structural analysis techniques in the frequency domain. More recently this work has focused on the link with Finite Element Analysis (FEA) because of the powerful design opportunities which this creates. The work has found many important practical applications. This paper will provide a state of the art perspective of random vibration fatigue technology. A number of design applications will be presented.

General Stress Analysis

APPLICATIONS OF FINITE ELEMENT ANALYSIS FOR AN IMPROVED MUSICAL INSTRUMENT DESIGN (Acrobat 896K) 1996, 20 pgs.
Mark Carlson--Fender Musical Instruments Corporation

ABSTRACT: Implementation of finite element analysis and proof of its power as a design tool to an industry unfamiliar with this type of technology will be demonstrated through the use of MSC/NASTRAN and MSC/ARIES to develop a comprehensive guitar neck system. This system will provide a better playing, better sounding instrument by accounting for the following:
• bending and twisting of the neck due to string forces
• bending and twisting of the neck due to moisture content expansion forces
• the cylindrical orthotropic nature of wood
• individual musician's preferences (neck adjustment capability)
• elimination of less resonant "dead spots" which occur for certain notes on the neck

Several analysis types will be utilized for different steps of the design phase as follows:

• linear static analysis for stability against string and moisture content loads
• nonlinear slideline contact analysis for developing the adjustment capability
• unstressed and prestressed modal analysis for tuning out "dead spots"

APPLYING VIRTUAL REALITY TECHNOLOGIES TO THE INTERACTIVE STRESS ANALYSIS OF A TRACTOR LIFT ARM (Acrobat 455K) #0198 , 15 pgs.
Michael J. Ryken, and Dr. Judy M. Vance-- Iowa State University

ABSTRACT: The objective of this research is to examine the challenges of applying virtual reality techniques to the interactive stress analysis of a tractor lift arm. NURBS-based free form deformation, finite element analysis, sensitivity analysis, collision detection, and virtual reality are combined to create an interactive environment for designers to view and modify part shape, evaluate the resulting stresses, and check for interference of the new part shape and surrounding parts in real-time. These methods are implemented using a surround screen virtual environment where the part of interest and associated geometry surrounding that part are displayed together using stereo projection to provide a three-dimensional view of the assembly.

COMPARISON OF MSC/NASTRAN ANALYSIS RESULTS TO SOME WELL KNOWN CLOSED FORM SOLUTIONS TO GUIDE MODELING OF VEHICLE STRUCTURES (Acrobat 1.3MB) 1996, 14 pgs.
Bijan K. Shahidi--Ford Motor Company
John V. Fazio--Ford Motor Company

ABSTRACT: The art of modeling is a basic yet integral part in obtaining a valid correlation between numerical (FEA/CAE) analysis and vehicle testing. This perhaps is the key ingredient in creating a confidence level among designers, analysts, and test engineers so that they can derive the best design using CAE and analytical prototypes.

There are several options available in MSC/NASTRAN when one desires to create a finite element model of a vehicle structure. The question that remains unanswered is, what is the best way to model a vehicle in a real world environment economically, and believe in the results without creating the actual part for testing. In order to gain some insight and answer this question, one often looks into the well-known classical mechanics problems in literature where there is either a closed form solution or a repeatable lab experiment conducted in a controlled envionment, to compare with modeling techniques.

In this paper, several classical problems are sought from literature, which are modeled using MSC/NASTRAN, and the results are compared to one another. The problems range from linear static analysis of slender beams to free vibration and nonlinear static analysis. The conclusions are drawn from the comparison of several modeling methods to the closed form solutions available to the authors. It is found that one must take great caution when modeling a vehicle structure on choice of element types, their size and range validity. Discussions on the accuracy of results in deflection analysis vs. stress or vibration analysis are made by using different modeling methods and rationalizing the comparison of the results to the analytical solutions.

COMPARISON OF THE MSC/NASTRAN AND HOLOGRAPHIC INTERFEROMETRY DATA ON A LOCAL STRAIN/STRESS EVALUATION IN THE ELASTO-PLASTIC RANGE (Acrobat 992K) 1996, 21 pgs.
A.S. Dzuba--Moscow Institute of Physics and Technology
V.D. Grigoriev--Moscow Institute of Physics and Technology
V.S. Pisarev--Moscow Institute of Physics and Technology

ABSTRACT: The report presented is related to the MSC/NASTRAN implementation to an accurate determination of a stress/strain concentration both in the elastic and elasto-plastic deformation range. This problem is of great importance from a low-cyclic-fatigue life-time prediction point of view.

The elastic stress concentration problem in a thin plane specimen under tension and thin-walled curved circular cylindrical shell subjected to torsion are considered carefully through the use of the Version 68.1. The accuracy of numerical results in both cases is established by comparing them with the corresponding experimental data obtained by means of holographic interferometric measurements. The calculation of maximum stress values is carried out by using QUAD4 Corner Output. An excellent agreement between numerical and experimental results have been revealed.

An evolution of local elasto-plastic strains in a thin plane strip with a circular open hole under static tension is studied. The data of holographic interferometric measurements are used again in order to estimate the accuracy of numerical solution for different levels of applied external load. An influence of the circumferential strain gradient on results of a maximum elasto-plastic strain calculation is dicussed in detail.

DIRECT OR ITERATIVE? A DILEMMA FOR THE USER (Acrobat 33K) #2698, 8 pgs.
Petra Poschmann, Louis Komzsik and Stefan Mayer--The MacNeal-Schwendler Corporation

ABSTRACT: The subject of this paper is the comparison of Direct and Iterative solvers in the Solution of large Finite Element Problems with MSC/NASTRAN. The results of such a comparison vary based on problem type and with new developments in both the direct and iterative solution techniques. This paper gives the curren