MSC Software Corporation

MSC 1995 World Users' Conference Proceedings

The conference proceedings for the 1995 World Users' Conference are now available on-line in Adobe Acrobat PDF format. (The Adobe Acrobat Reader software is available for free download from Adobe's web site at www.adobe.com.) When printed, these PDF files will produce a better quality image than the one shown on your computer screen. All papers have been categorized by topic.

Aircraft

GETTING FEA INTO THE DESIGN PROCESS: RAPID ANALYSIS OF TUBES (Acrobat 667KB) #495
Raymond N. Frick, Ph.D., RE.--Pratt & Whitney
: ABSTRACT: This paper shows how Pratt & Whitney increased engineering productivity by incorporating finite element analysis (FEA) with MSC/NASTRAN into the design cycle. In particular, Pratt & Whitney has developed a fast, efficient process to analyze external tubes of jet engines called the Preliminary Tube Analysis (PTA) System. This process was originally intended to be a preliminary analysis prior to a more formal analysis. However, it has been proven to be very accurate and is usually the only analysis. This process uses a commercial CAD program, MSC/NASTRAN, and custom pre and post processors. This process enables all tubes for new designs to be analyzed before manufacture and testing. While relating some of the details of the custom programs, the emphasis of this paper will be on the process development; i.e. how finite element analysis can be put to effective use within the design environment. This required understanding the design process, creating custom programs to interface with commercial codes, and applying engineering judgment.

Automotive

ANALYSIS OF FLEXIBLE ROTATING CRANKSHAFT WITH FLEXIBLE ENGINE BLOCK USING MSC/NASTRAN AND DADS(Acrobat 787KB) #3595
Lee S. Mayer--Computer Aided Design Incorporated
Hans Zeischka--Computer Aided Design Incorporated NV
Frank Maessen--Computer Aided Design Incorporated NV
Marc Scherens--Computer Aided Design Incorporated NV
: ABSTRACT: Mechanical engineers most commonly predict stress and vibration of components within complete mechanical systems by the use of Finite Element Analysis (FEA) techniques. The accuracy of predictions depends mainly on applied boundary and loading conditions as well as meshing techniques. Experience has shown that discrepancies between numerical prediction and test data become great when one is dealing with dynamically loaded structures within mechanical systems that undergo large rigid body motion. Such systems typically exhibit geometric non-linearity and non-linear compliance between the different bodies. This publication presents the basic theory of flexible bodies in DADS and the application in the study of interaction between crankshaft and engine block for 4-cylinder and 4-stroke engines in unfired and fired conditions.

APPLICATION OF A FRF BASED MODEL UPDATING TECHNIQUE FOR THE VALIDATION OF FINITE ELEMENT MODELS OF COMPONENTS OF THE AUTOMOTIVE INDUSTRY (Acrobat 1.77MB) #795
Stefan Lammens--LMS International
Marc Brughmans--LMS International
Jan Leuridan--LMS International
Paul Sas-- Katholieke Universiteit Leuven
DEVELOPMENT OF A NONLINEAR FREQUENCY RESPONSE PROGRAM FOR SIMULATING VEHICLE RIDE COMFORT(Acrobat 491KB) #3795
Keuchiro Tsutsui-- ESTECH Corporation
Ray Nogami--ESTECH Corporation
John L. Breti, Ph.D.-- Structural Dynamics Research Corp.
: ABSTRACT:Dynamic models have been used in the automotive industry as predictive tools in simulating the vibrational characteristics of vehicles. However, existing models are limited in their ability to deal with nonlinear characteristics such as the frequency and amplitude dependency of connectors. A practical frequency response program has been developed that can treat the nonlinear vibrational characteristics of various connectors. This program interfaces with an MSC/NASTRAN FEA model, which is used to assemble the baseline system matrices for the nonlinear solution. The program includes such nonlinear capabilities as frequency/amplitude-dependent elastomeric connectors, velocity-dependent viscous damping elements and Coulomb friction damping. This paper outlines the program and gives an example of its application to an analysis of vehicle ride comfort, the results of which correlated closely with experimental data.

FRICTION INDUCED VIBRATION (Acrobat 732KB) #3695
Wayne V Nack--General Motors Corporation
Arun M Joshi--General Motors Corporation


MODAL TEST ON THE PININFARINA CONCEPT CAR BODY, "ETHOS 1" (Acrobat 785KB) #595
ir M. Brughmans--LMS International
ir F. Lembregts, PhD--LMS International
ir F. Furini, PhD--Industrie Pininfarina
: ABSTRACT: This paper describes the modal test and analysis carried out on the body of a 2 passenger cabriolet concept car designed by Pininfarina. It discusses the specific problems in a modal test on such a car body of extruded aluminium profiles. Next, the experimental modal model is correlated with an MSC/NASTRAN analytical model, and a diagnosis is made to improve the analytical model.

A STUDY ON IDLE VIBRATION ANALYSIS TECHNIQUE USING TOTAL VEHICLE MODEL (Acrobat 322KB) #695
H.B. Park--Hyundai Motor Company
J.K. Suh--Hyundai Motor Company
H.G. Cho--Hyundai Motor Company
G.S. Jung--Hyundai Motor Company
: ABSTRACT: It was required to improve the low frequency vibration characteristics of a current production car. For the sake of design study, a well correlated FE model was necessary. This paper describes the process of how to build FE model and to correlate it with test result from BIW to total vehicle.

Design/Manufacturing Methods

COMBINING MSC/NASTRAN, SENSITIVITY METHODS AND VIRTUAL REALITY TO FACILITATE INTERACTIVE DESIGN (Acrobat 819KB) #395
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.

DMAP in Dynamics

EFFECTIVE MASS SENSITIVITY: A DMAP PROCEDURE (Acrobat 743KB) #3995
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
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 564KB) #4095
Jack Scanlon--Analex Corporation
Jim Swan--MSC.Software 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.

Dynamic Analysis

DYNAMIC ANALYSIS BY THE FOURIER TRANSFORM METHOD WITH MSC/NASTRAN (Acrobat 1.07MB) #1095
Dean Bellinger--The MSC.Software 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.

MODEL REDUCTION AND MODEL CORRELATION USING MSC/NASTRAN (948KB) #895
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.

VIBROACOUSTICS RANDOM RESPONSE ANALYSIS METHODOLOGY (Acrobat 566KB) #995
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.

Elements

ANALYSIS OF SHELL STRUCTURES USING MSC/NASTRAN'S SHELL ELEMENTS WITH SURFACE NORMALS (Acrobat 643KB) #2695
C.C.Hoff--MSC.Software Corporation
R.L.Harder--MSC.Software Corporation
G.Campbell--Ford Motor Company
R.H.MacNeal--MSC.Software Corporation
C.T.Wilson--MSC.Software 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
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
Jerrold M. Housner--NASA Langley Research Center
Mohammad A. Aminpour--Old Dominion University
Carlos G. Davila--National Research Council Associate
John E. Schiermeier--MSC.Software 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 855KB) #2495
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 786KB) #1895
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 389KB) #1795
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.

A LIFE PREDICTION ALGORITHM IMPLEMENTED IN P3 USING PCL (Acrobat 1.01MB) #1995
Matthew E. Melis--NASA Lewis Research Center
Joseph A. Ogonek--Analex Corporation

Nonlinear Analysis

A DESIGN STAGE NON-LINEARISATION OF STIFFENED-COMPRESSION PANELS FOR LINEAR MSC/NASTRAN/ARIES MODELLING OF DIAGONAL TENSION FIELD SHELLS (Acrobat 1.61 MB) #3095
S. Basic--Morrison Knudsen Corporation
FULLY NONLINEAR HYPERELASTIC ANALYSIS OF NEARLY INCOMPRESSIBLE SOLIDS: ELEMENTS AND MATERIAL MODELS IN MSC/NASTRAN (Acrobat 1MB) #2995
Katerina-D. Papoulia--MSC.Software Corporation
: ABSTRACT: The hyperelastic elements in MSC/NASTRAN are described for 3D, plane strain and axisymmetric analysis with large strain and large rotation. The hyperelastic model used is generalized Rivlin of up to order five, extended to include the effect of compressibility at the nearly incompressible limit. Emphasis is placed on the treatment of incompressibility and the avoidance of volumetric locking. Mixed and selective reduced integration methods and the use of penalty versus Lagrange multipler techniques is discussed. Higher order elements, which effectively overcome shear locking, are presented. A series of simple and real-life examples is provided to illustrate the features of the model: extremely large strain and element distortion, volumetric and shear locking avoidance and contact applications.

STABILITY ANALYSIS OF PERFECT AND IMPERFECT CYLINDERS USING MSC/NASTRAN LINEAR AND NONLINEAR BUCKLING (Acrobat 1.48MB) #2795
M. H. Schneider, Jr.--McDonnell Douglas Aerospace
R. J. Feldes--McDonnell Douglas Aerospace
J. R Halcomb--MSC.Software
C.C. Hoff--MSC.Software
: ABSTRACT: The buckling behavior of cylindrical shells with and without initial geometric imperfections is investigated using a combined analytical and experimental approach. Seamless cylindrical plastic models were fabricated and tested under axial compression and external hydrostatic pressure as "perfect" cylinders. Upon completion of testing, the cylinders were reformed to a specified imperfection shape and re-tested. The thickness, modulus of elasticity, and geometric shape was measured for each cylinder. Analytical models were generated in MSC/PATRAN using measured imperfection shape and amplitude. Buckling loads were calculated in MSC/NASTRAN using the geometric nonlinear analysis provided in solution sequence SOL 106. These results were correlated to experiments and compared with results predicted by other computer codes. The finite element mesh spacing used in the correlation effort was based on the results of a mesh convergence study performed using the linear eigenvalue solution sequence SOL 105. Good agreement between experimental results and other predictions was achieved.

STATIC TEST AND NONLINEAR ANALYSIS OF THE MAST FOR INTERNATIONAL SPACE STATION ALPHA SOLAR ARRAY WING (Acrobat 1.17MB) #2895
C.C.Tang--Lockheed Missiles & Space Company
A.J. Elliott--Lockheed Missiles & Space Company
Dr. M. L.Bowden--AEC-Able Engineering Company, Inc
S. Robinson--AEC-Able Engineering Company, Inc.
: ABSTRACT: Static test and nonlinear analyses results are used to develop the on-orbit end-of-life (EOL) strength of the deployed mast for the International Space Station Alpha Solar Array wing. The fully deployed mast is a 108 feet long boom that is capable of supporting the solar array wing for on-orbit plume impingement loads and inertia loads induced by space station disturbances. A series of static structural tests are performed to characterize the mast. The test results are then used to validate a MSC/NASTRAN nonlinear finite element model of the mast. Nonlinear static analyses, using the test-validated finite element model, are performed to determine mast failure for a large number of load combinations and orientations. Based on these data and an understanding of the mast behavior in the nonlinear regime, two interaction strength formulas are developed to define the on-orbit EOL mast limit load capability for combined loads in two different orientations. The test program and nonlinear finite element analysis using MSC/NASTRAN SOL 106 (V67.7) are described in this paper.

Nonlinear Transient Response

APPLICATION OF MSC/DYTRAN TO THE HYDRODYNAMIC RAM PROBLEM (Acrobat 1.43MB) #1295
Geetha Bharatram--Wright Patterson AFB
Capt. Scott A. Schimmels--Wright Patterson AFB
Dr. Vipperla B. Venkayya--Wright Patterson AFB


EXTENDING MSC/DYTRAN FOR THE NUMERICAL SOLUTION OF THE NAVIER-STOKES EQUATIONS (Acrobat 1.08MB) #5295
Ortwin .cfmer--California State University, Long Beach
NONLINEAR IMPACT ANALYSIS OF INTERNATIONAL SPACE STATION ALPHA MODULE BERTHING USING MSC/NASTRAN (Acrobat 1.59MB) #5095
Timothy S. West--McDonnell Douglas Aerospace
David A VanHorn--McDonnell Douglas Aerospace
John R LeCour--McDonnell Douglas Aerospace
Mitchell W. Usrey--McDonnell Douglas Aerospace
: ABSTRACT: MSC/NASTRAN nonlinear gap element modelling techniques were implemented to analyze the impact between berthing modules and on-orbit structure during assembly of International Space Station Alpha (ISSA). Component mode synthesis techniques were used to create superelements to reduce the analysis set degrees of freedom during the nonlinear analysis. Superelements were again used in structural response recovery, where the impact forces were applied to the reduced ISSA model in modal transient analysis and responses were recovered for a large number of response items. This procedure is illustrated with three different examples.

THREE-DIMENSIONAL SIMULATION OF CLOSED-DIE FORGING PROCESS USING MSC/DYNA (Acrobat 805KB) #1395
Mary Wicklin Schleider--Mercer University Engineering Research Center
: ABSTRACT: A three-dimensional, elastic-plastic finite element model using MSC/DYNA was used to simulate a closed-die forging process. An H-shaped cross-section forging die and a rectangular billet were modelled. Die/billet interface contact friction, and die geometry were varied to determine the effects of these variables on material flow, strain, and die force.

USE OF MSC/NASTRAN IN PREDICTING STRUCTURAL RESPONSE TO AN UNDERWATER EXPLOSION (Acrobat 430KB) #5195
Kevin E. Arden--Newport News Shipbuilding
: ABSTRACT: The prediction of the response of submerged structures to underwater explosions requires solving a fluid-structure interaction problem. This paper is based on experiences with MSC/NASTRAN's interface with the USA (Underwater Shock Analysis) code. The phenomena associated with an underwater explosion and how MSC/NASTRAN/USA is used to solve the problem will be discussed. As a validation, analytical results will be compared to a test. The statements and opinions herein are those of the author and do not necessarily represent Newport News Shipbuilding.

VULNERABILITY AND SURVIVABILITY ANALYSIS OF AIRCRAFT FUSELAGE SUBJECTED TO INTERNAL DETONATIONS (Acrobat 1.13MB) #1195
Young Moon--Wright Patterson AFB
Geetha Bharatram--Wright Patterson AFB
Capt. Scott Schimmels--Wright Patterson AFB
Dr.Vipperla Venkayya--Wright Patterson AFB

Optimization

DESIGN SENSITIVITY ANALYSIS FOR DURABILITY DESIGN OF BODY STRUCTURES (Acrobat 655KB) #4895
E Y. Kuo--Ford Motor Company
S. G. Kelkar--Ford Motor Company
R Nagpal--Ford Motor Company

ABSTRACT: Design sensitivity analysis (DSA) computes the derivatives of structural response quantities (e.g., displacements, stresses, modal frequencies, mode shapes) with respect to design variables (e.g., cross-sectional properties such as area, moments of inertia, torsional constant). These derivatives, defined as design sensitivity coefficients, give the designer a feel as to how the structure will respond to a proposed design change. Although the general concept of DSA has been well established, the application of this method to vehicle body durability design is relatively new. The current paper examines the relation between the body overall stiffness/strength characteristics and fatigue life. It also demonstrates how DSA can be employed to effectively identify design variables most affecting fatigue life through the body overall stiffness/strength evaluations. The methods and concepts are demonstrated using a very simplified finite element model which conceptually simulates a body structural system.

INNOVATIVE USES OF SYNTHETIC RESPONSES IN DESIGN OPTIMIZATION (Acrobat 701KB) #4995
Erwin H. Johnson--MSC.Software Corporation

ABSTRACT: Synthetic responses in MSC/NASTRAN allow the user to combine responses, design variables, and grid locations to define new responses that can be incorporated into a structural design task. This paper indicates how this capability can be applied in a wide variety of applications. Four examples are presented showing the use of this capability to (1) minimize the maximum stress response, (2) create mean-square responses (3) include Johnson/Euler buckling conditions in the design task, and (4) perform topology optimization.

OPTIMAL DESIGN OF A SIMULATOR MODULE FRAME (Acrobat 384KB) #1595
S.C. McIntosh, Jr.--McIntosh Structural Dynamics, Inc.
Erwin H. Johnson--MSC.Software Corporation

ABSTRACT: The support frame of a simulator module for the entertainment industry is designed to meet stiffness and strength conditions while minimizing the weight. As such, it represents a straightforward design optimization task with the novelty associated with the nonconventional vehicle that is being designed. A simple frame structure is used for the design. MSC/NASTRAN's ability to synthesize property values allows considerable generality in the specification of cross-sectional dimensions. This paper presents the design concept, the loading conditions, and the design constraints. The MSC/NASTRAN model is discussed, and the results of the the optimization task are given. The initial arbitrary design was infeasible, with a 33 percent weight increase necessary to achieve the final optimal design.

OPTIMUM DESIGN OF A LIGHTWEIGHT TELESCOPE (Acrobat 560KB) #1495
Victor Genberg--Eastman Kodak Company

ABSTRACT: The sizing and shape capability of MSC/NASTRAN was applied to the design of an orbiting lightweight telescope. Design variables included dimensions of the primary mirror, mounts, and metering structure. Constraints were applied to optical performance measures such as image motion and surface distortion, as well as the conventional stress, frequency, and buckling behavior.

SHAPE OPTIMIZATION USING SHAPE BASIS VECTORS (Acrobat 428KB) #4795
Jane Zhang--Ford Motor Company

ABSTRACT: Most shape optirnization methods require parametric modeling and automatic mesh generation. However, there are no robust tools available for parametric modeling and automeshing. This has resulted in few applications of shape optimization to large-scale industrial structures. Recently, the reduced basis method was introduced in shape optimization. Because it does not require the parametric modeling and auto-meshing, it has found wide applications in the automotive industry. Research engineers in Ford Motor Company have incorporated the reduced basis method in their design software. Development engineers in MSC.Software Corporation also implemented this method in MSC/NASTRAN. They recently released MSC/NASTRAN version 68 which provides shape optimization capability with the feature of reduced basis vectors. In this paper, the shape optimization capability in MSC/NASTRAN V68 is discussed. The Modified Thermal Load Approach (MTLA) for generation of shape basis vectors is described. A procedure is developed for generating and inputting these basis vectors to the MSC/NASTRAN The convergence characteristics and the efficiency of incorporating MTLA for MSC/NASTRAN optimization process are demonstrated through two numerical examples. The optimized results are presented and discussed.

USING OPTIMIZATION IN MSC/NASTRAN TO MINIMIZE RESPONSE TO A ROTATING IMBALANCE (Acrobat 1.11MB) #1695
Ted Rose--MSC.Software Corporation

ABSTRACT: In any applications of rotating equipment, it is common for an engineer to try to minimize the response of a structure with a rotating imbalance. This paper demonstrates how to perform this minimization using MSC/NASTRAN. A practical example problem is used. This sample minimizes the response at the driver's seat of a car model with a wheel out-of-balance. The problem will begin by demonstrating how to perform frequency response analysis of the car model with a rotating imbalance, followed by dynamic sensitivity of the response, followed by minimization of the response by tuning the dampers (shock absorbers) and springs.

During the process, special features in MSC/NASTRAN will be used to assist in understanding the dynamic problem and in determining the best approach to minimizing the response.

PC Products

INTEGRATED FEM/FEA ON POWER MAC (Acrobat 326KB) #4595
Gert Lundgren--LAPCAD Engineering
: ABSTRACT: LAPCAD Engineering introduces LapFEA, a logical union of LapCAD and MSC/pal 2. The model is created in LapFEA, complete with connectivities, properties and loads. Then the analysis is executed with icons in the Solver tool pallet. Post-processing and documentation with a word processor is completed from within LapCAD.

MSC/NASTRAN FOR WINDOWS: THE POWER OF MSC/NASTRAN COUPLED WITH THE EASE OF USE OF WINDOWS (Acrobat 654KB) #4695
Ken Blakely--MSC.Software Corporation
Cliff Brown--MSC.Software Corporation
Brian Casey--MSC.Software Corporation
Wai Ho--MSC.Software Corporation
Son Giang--MSC.Software Corporation
Mark Kenyon--MSC.Software Corporation
John Muskivitch--MSC.Software Corporation
John Saunders--MSC.Software Corporation
Grant Sitton--MSC.Software Corporation
Richard Taylor--MSC.Software Corporation
: ABSTRACT: This paper presents an overview of MSC/NASTRAN for Windows. The product integrates modeling, analysis, and postprocessing, all within the familiar interface of Microsoft Windows 3.1. This paper focuses on the philosophy, features, and performance of the product.

MULTI DISCIPLINARY ANALYSIS IN MSC/NASTRAN WITH FEMAP (Acrobat 1.29MB) #4495
Mark A. Sherman--Enterprise Software Products, Inc.
: ABSTRACT: FEMAP is a general-purpose finite element modeling and post-processing software package available for Personal Computers running Microsoft Windows 3.1 and Windows NT, DEC Alpha Workstations running Windows NT, and HP, SGI, SUN, and IBM UNIX Workstations. This paper presents the multi-disciplinary analysis of a hot-gas diffuser that was modeled in FEMAP, and analyzed with MSC/NASTRAN, complete with step-by-step modeling descriptions that will provide the reader with a thorough understanding of the capabilities of FEMAP as applied to a combined static, modal, and thermal analysis of the hot-gas diffuser.

Stress Analysis

AUTOMATED STRESS ANALYSIS - REDUCING STRESS ANALYSIS TIME BY AN ORDER OF MAGNITUDE (Acrobat 296KB) #4195
John C. Lambert--United Technologies Hamilton Standard Division
Brent J. Merritt--United Technologies Hamilton Standard Division

ABSTRACT: In an environment of ever increasing global competition, pressure on engineering organizations to produce high quality products quickly has become extreme. As a result, fast and accurate stress analysis has become a critical issue. Analysts and Designers must conduct analyses in much shorter time spans. This paper discusses a new rule-based approach that automates finite element analysis and the entire pre- and post-processing tasks. Hamilton Standard has achieved order of magnitude reductions in analysis turnaround times as a result of rule-based automation.

CLOSED-FORM STATIC ANALYSIS WITH INERTIA RELIEF AND DISPLACEMENT-DEPENDENT LOADS USING A MSC/NASTRAN DMAP ALTER (Acrobat 686KB) #3195
Alan R. Barnett--Analex Corporation
Timothy W. Widrick--Analex Corporation
Damian R. Ludwiczak--National Aeronautics and Space Administration

ABSTRACT: Solving for the displacements of free-free coupled systems acted upon by static loads is commonly performed throughout the aerospace industry. Many times, these problems are solved using static analysis with inertia relief. This solution technique allows for a free-free static analysis by balancing the applied loads with inertia loads generated by the applied loads. For some engineering applications, the displacements of the free-free coupled system induce additional static loads. Hence, the applied loads are equal to the original loads plus displacement-dependent loads. Solving for the final displacements of such systems is commonly performed using iterative solution techniques. Unfortunately, these techniques can be time-consuming and labor-intensive. Since the coupled system equations for free-free systems with displacement-dependent loads can be written in closed-form, it is advantageous to solve for the displacements in this manner. Implementing closed-form equations in static analysis with inertia relief is analogous to implementing transfer functions in dynamic analysis. Using a MSC/NASTRAN DMAP Alter, displacement-dependent loads have been included in static analysis with inertia relief. Such an Alter has been used successfully to efficiently solve a common aerospace problem typically solved using an iterative technique.

DMAP ALTERS TO ADD DIFFERENTIAL STIFFNESS AND FOLLOWER FORCE MATRICES TO MSC/NASTRAN LINEAR SOLUTIONS (Acrobat 341KB) #3395
David F. Bella--MSC.Software Corporation

ABSTRACT: This paper describes a DMAP procedure to add differential stiffness and follower force matrices to MSC/NASTRAN linear analysis solution sequences. Differential stiffness results from internal element forces due to applied loads. It is used in buckling analysis to determine buckling loads and also in geometric nonlinear analysis to more efficiently converge to correct solutions. Follower forces arise from loads which are dependent on a structures geometry. As a structure deforms, follower forces change in their magnitude or direction. This displacement-dependent change of loading can be characterized as a stiffness term in linear analysis. Inclusion of the differential stiffness and follower force matrices produce a corrected tangent stiffness matrices for linear analysis.

DYNAMIC ANALYSIS OF R.C.C. CHIMNEYS (Acrobat 787KB) #3495
M. Shivaji--A.P.S.E. Board
V.S.N. Raju--A.P.S.E. Board

ABSTRACT: Chimneys are symbols of industrial growth in any country. Most current chimney design standards require analysis of dynamic response of chimney due to influence of earthquake or wind-induced loads. Because of changes in the dimensions of chimney structural analysis such as response to earthquake and wind oscillations have become more critical. This paper discusses the dynamic analysis of 220m high R.C.C. chimney for free vibration analysis and response spectrum analysis using MSC/NASTRAN. Analysis has been carried out for a) fixed base case and b) base soil structure interaction case. Apart from showing appreciable differences in eigen values and eigen vectors with respect to fixed base, the interaction model has shown large reduction in values of Bending Moment and Shear Force due to seismic forces at the base of the chimney. Analysis has also been carried out for SRSS, NRL & ABS methods and results are compared. Effect of damping is also studied.

AN INTERACTIVE COMPUTER AIDED DESIGN SYSTEM FOR CUT-OUTS IN PRESSURIZED AIRCRAFT FUSELAGES (Acrobat 1.37 MB) #4395
M.E. Heerschap--Delft University of Technology

ABSTRACT: Cut-outs in pressurized aircraft fuselages are very sensitive to fatigue. This explains the need for a design tool to enable the designer to perform a comprehensive design of these "difficult" structures. A menu-driven, highly interactive system for the design of the reinforcement around a cut-out in a pressurized fuselage is presented. The design system is set up in such a way that maximum use is made of the combination of MSC/NASTRAN and MSC/PATRAN. There are six basic options offered by the system: 1) fast, easy initial model generation; 2) fully interactive, user-friendly model editing; 3) preparation for both geometrically linear and geometrically non-linear finite element calculations; 4) preparation for a sensitivity analysis and graphical display of the results of such an analysis; 5) carrying out "what-if" studies; 6) preparing and performing a design optimization.

The system is set up as a special-purpose design tool. This makes a considerable improvement in the design process, because the time needed for the modelling of the complex structure is greatly reduced. The design system is based on the pre- and post-processor MSC/PATRAN. The necessary software is written almost entirely in MSC/PATRAN Command Language (PCL) which implies that the generated code can be run "inside" MSC/PATRAN. Maximum use is made of the graphical capability of this software package. The finite element calculations, including sensitivity analysis and optimization, are performed with MSC/NASTRAN.

SASSI - STRUCTURAL ANALYSIS SOFTWARE SYSTEMS INTERFACE (Acrobat 1.57MB) #4295
Lee Abbuhl--Boeing Computer Services
Viswa Padma_nabhan--Boeing Computer Services

ABSTRACT: SASSI contains a set of tools for structural engineering analysis in a distributed workstation environment. These tools provide 1) access to a host of engineering applications software through a single command 'SASSI' entered in a workstation window. Analysis data post-processing, network tasks, plotters and printers, and additional system and analysis tools are available and accessed by a set of pop-up menus and dialog boxes in the menu. 2) Data transfers between the various applications are very efficient in SASSI. 3) An interactive menu interface provides transparent access to engineering computing tasks and applications that enhances the productivity of stress engineers. Some of these will be illustrated by examples using MSC/NASTRAN.

SELF-EXCITED OSCILLATION OF A 165 FOOT WATER TOWER (Acrobat 957KB) #3295
Louis J. Pulgrano--E. I.. duPont de Nemours and Company
Steven G. Masters--E. I.. duPont de Nemours and Company

ABSTRACT: When a new 165 foot high water tank was being filled for the first time, a large amplitude oscillation of the entire structure occurred and forced an immediate shutdown of the filling process. Analysis of the problem, using a combination of math modeling and experimental measurements, revealed the cause to be an unstable coupled fluid/structural response that was being driven by the incoming water. Design modifications were needed to eliminate the coupling and allow the tank to be put into service.

Thermal Analysis

DESIGN OF RAPID THERMAL PROCESSING SYSTEM BASED ON MSC/NASTRAN THERMAL ANALYSIS (Acrobat 732KB) #2195
Sergey Belikov--New Jersey Institute of Technology
Helen Martynov--New Jersey Institute of Technology
Michael Kaplinsky--New Jersey Institute of Technology

ABSTRACT: This paper describes a finite element model of rapid thermal processing (RTP) system for semiconductor manufacturing and its implementation with MSC/NASTRAN. The model is used for optimization of geometry and configuration of heating lamps in the RTP system. MSC/NASTRAN serves two main purposes: (1) calculation of parameters for design optimization algorithm using VIEW module; (2) performance evaluation of obtained configuration using heat transfer analysis. Condition of achievability of temperature uniformity is used as the goal of design in an interactive procedure with MSC/NASTRAN program in the kernel. Version 68 allows to improve the design procedure. Possible further refinements are discussed.

MODELLING AND ANALYSIS OF AN ACCELEROMETER USING MSC.Aries AND MSC/NASTRAN (Acrobat 1.17MB) #2295
Yeuan Jyh Ju--University of Bridgeport
Tienko Ting--University of Bridgeport

ABSTRACT: This paper presents the modeling and analysis of an accelerometer mounted on a jet engine block. The effects of some extreme thermal and vibratory conditions were examined. The finite element model of the accelerometer was modelled using the solid modeling and automatic meshing generation capabilities of MSC.Aries. Normal modes and thermal analysis were then performed using MSC/NASTRAN Version 68.

STRESS ANALYSIS OF HYBRID PINS IN A WARPED PRINTED WIRING BOARD USING MSC/NASTRAN (Acrobat 480KB) #2095
Kirit V. Patel--Sverdrup Technology, Inc.

ABSTRACT: During manufacturing, when the hybrids are wave soldered on a plated-through hole printed wiring board, the heat effects cause the polyimide board to warp. Since the hybrids are rigid, any attempt to straighten the edge of the board will introduce the residual stresses in the pins of the hybrid. This paper presents finite element modeling of such an out-of-plane imperfection of the board. The stress analysis is performed to estimate the residual stresses in the hybrid pins using MSC/NASTRAN. Also, a chassis level random frequency response analysis is performed to show the use of excursion delimiter in reducing the vibration-induced deflections in the board.

MSC 1995 World Users' Conference Proceedings

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