MSC 1987 World Users' Conference Proceedings-Volume I

The conference proceedings for the 1987 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.

STATUS OF MSC PRODUCTS, 1987 (Acrobat 2.08MB) #0287, 44 pgs.
M.A. Gockel--MSC.Software Corporation

ABSTRACT: MSC provides a series of software products and services useful to the engineering community. The status of these products and services is discussed here. (The text below is intended to accompany the figures attached at the end, which will be used for presentation at the 1987 MSC World Users Conference.)

OPTIMIZATION AND FINITE ELEMENT ANALYSIS: THE STEP FROM ANALYSIS TO DESIGN
(Acrobat 1.95MB) #0387, 21 pgs.
Garrett N. Vanderplaats--University of California Santa Barbara, California

ABSTRACT: The process and prospects of coupling finite element analysis with numerical optimization is discussed. The general history of these two technologies is first reviewed to identify the present state of the art. General concepts of optimization are then outlined to identify both the methodology and the generality of these methods. The finite element method is then discussed in its simplest form and the features that make it particularly amenable to optimization are identified. The concept of using approximation techniques is then introduced as a means of dramatically reducing the number of detailed finite element analyses used by optimization. Examples are offered to demonstrate the power of optimization when coupled with finite element analysis. Finally, the present effort to incorporate optimization directly into the MSC/NASTRAN program is described. References are provided for further reading. It is concluded that optimization is a powerful design tool whose time has come.

STRESS ANALYSIS OF PLANET GEARS WITH INTEGRAL BEARINGS; 3-D FINITE ELEMENT MODEL DEVELOPMENT AND TEST VALIDATION (Acrobat 1.95MB) #0487, 14 pgs.
Raymond J. Drago and Ravi N. Margasahayam--Boeing Vertol Co., Philadelphia

ABSTRACT: The load-carrying capacity of helicopter planetary transmissions depends to a great extent on the strength of thin-rimmed, roller-supported, hollow planet gears with integral bearings. Thick-rim analogy forms the basis for planet strength evaluation in the conventional method now used. Such methods lack accuracy as the rim thickness decreases, both in the prediction of location as well as the magnitude of maximum stress. Therefore, more accurate design tools are necessary to improve the reliability of lightweight planetary gears.

This paper presents an analytical technique for the evaluation of planet gear strength based on the three-dimensional finite-element method (FEM). Full-gear tooth-rim models were developed from 8-noded CHEXA elements and were superimposed with CONROD's to simulate test placement of strain gages. Reasoning for a circumferential model comprising 3,000 to 5,000 elements, together with a brief review of related FEM effort, are presented to provide a case for full-gear three-dimensional models, especially for planet gears.

The finite-element-model-predicted shape of the stress distribution around the gear is used to evaluate the magnitude and location of maximum stress for two planet gears. A comparison of FEM-calculated stresses and those from full-scale quasistatic tests for the two planet gears indicated good correlation. The FEM technique was then extended to determine the strength of an existing designs in the absence of full-scale test data.

The effect of planet gear support on the overall gear strength, not fully addressed by the conventional method, has been demonstrated as an important factor in the design of planet gears. The ability of the present FEM analytical tool to accurately identify and evaluate alternative designs is pointed out. Finally, the applicability of three-dimensional modeling in the design optimization of planet gears with integral bearings is noted.

STRUCTURAL AND OPTICAL ANALYSIS OF A LANDSTAT TELESCOPE MIRROR (Acrobat 1.11MB) #0587, 14 pgs.
Thomas E. Wolverton and John J. Brooks--Santa Barbara Research Center, California

ABSTRACT: Finite element techniques were employed to determine distortions and subsequent image characteristics of the primary telescope mirror in a LANDSAT scanning spectral radiometer. Mirror deformations due to gravity and the presence of friction loads in kinematic mirror mounts were determined using the static analysis capabilities of MSC/NASTRAN. Displacement results were then postprocessed by PDF/PATRAN to create optical pseudo-spot diagrams indicating image degradation. These focal plane spot diagrams provide a convenient graphical method for quickly identifying critical load cases and predicting results of optical testing.

ANALYSIS OF AUTOMOTIVE AXLE CARRIER ASSEMBLY AND COMPARISON WITH TEST DATA (Acrobat 2.27MB) #0687, 26 pgs.
A.A. Herbert and A.O. Currie--Compumod Pty. Ltd.
W. Wilson--Borg Warner, Australia

ABSTRACT: This paper describes the analysis of an axle carrier manufactured by Borg Warner Australia for the Pontiac Firebird. The aims of the analysis were to model the separation of the crown and pinion gears under drive and coast load and to produce reasonably accurate stress information for the axle carrier shell. It was also intended to gain confidence in the modelling techniques so that they could be used in the design of future components.

Deflections test data was available for the actual carrier. The paper shows that good correlation (within the accuracy of the test) was achieved between the model and the results.

This paper also discusses several other points of interest in the analysis. These include the use of solid modeling to define complex surface geometry, the use of solid modelling to define complex surface geometry, the use of inclined planes to model gear tooth interaction, modelling of bearing stiffness and support conditions and the use of thermal expansion to model an interference fit.

STRUCTURAL REANALYSIS SYSTEM (SRS) FOR THE PHILLIPS PETROLEUM GROUP'S "MAUREEN" TSG PLATFORM USING MSC/NASTRAN SUPERELEMENT DATA BANK AND DMAP PROCESSING (Acrobat 1.56MB) #0787, 21 pgs.
D.R. Hummel--Phillips Petroleum Co., Ivory Coast

ABSTRACT: The Maureen Platform Structural Reanalysis Sytem (SRS), based on MSC/NASTRAN Superelement Data Bank and DMAP processing, provides a rapid and low cost computer analysis of structural integrity in the event of damage to primary steel works.

This paper describes the main components of the system and how it is used in case of structural damage.

The system is composed of:

• the "as built" MSC/NASTRAN structural model of the platform (24,000 DOFs subdivided into 5 superelements)
• the structural Data Bank, including all the input/output data relevant to the NASTRAN analyses performed on the intact structure
• a set of DMAP routines to manage the Data Bank and interactive software devoted to quick selection, sorting and visualization of data included in the Data Bank
• a set of operating manuals to guide the structural reanalysis.

The actions to be performed by the SRS in case of damage are:

• automatic identification of the structural area sensitive to the damage (critical area)
• automatic identification of the loading conditions from 200 combined loading cases that induce the maximum stresses in the elements of the critical area.
• automatic generation of a reduced structural model (i.e. damage model) in NASTRAN format, including load vectors for the critical loading conditions and relevant boundary conditions for the reduced model.
• structural reanalysis and checks of the elements in the reduced model
• visualization on a graphic screen of the required parameters (displacements, forces, safety factors, etc.) for each desired portion of the structure.

A team of engineers and computer scientists then analyze the results and reach conclusions regarding the structural integrity of the platform.

The SRS System allows all these operations to be performed in less than 24 hours, a process which in the past has taken weeks, even months to be performed.

AUTOMATED FINITE ELEMENT MODELING: HOW CLOSE IS IT? (Acrobat 1.15MB) #0887, 10 pgs.
Mark S. Shephard--Rensselaer Polytechnic Institute

ABSTRACT: This paper gives a brief overview of the progress that has been made on the development of automated finite element modeling procedures. It then gives an indication of how users may view such systems.

ASSUMPTIONS AND ACCURACIES ASSOCIATED WITH THE MSC/NASTRAN ROD, BAR, AND QUAD4 ELEMENTS (Acrobat 1.56MB) #0987,28 pgs.

ABSTRACT: A number of scattered references regarding certain MSC/NASTRAN finite elements are united in this paper to give the program user a convenient single source for the assumptions involved when modeling typical aerospace structures. Items such as mass and stiffness matrix element assumptions, implicit when using the ROD, BAR, and QUAD4 elements, are presented. In addition, the accuracies associated with their common usage are also summarized.

These elements are then used in various combinations to model a stiffened circular cylinder with features typical of many semi-monocoque structures. Finite element free vibration results are then compared with closed-form analytical solutions for both an isotropic and orthotropic thin cylindrical shell formulation to further substantiate the overall accuracy possible when modeling aerospace type structures with the above cited elements.

FINITE ELEMENT SIMULATION OF COUPLED AUTOMOBILE ENGINE DYNAMICS (Acrobat 672K) #1087, 14 pgs.
David N. Herting, David F. Bella, and Patty A. Kimbrough--MSC.Software Corporation

ABSTRACT: A procedure has been developed to simulate engine dynamics and determine displacements and forces in the reference frames of the moving components. The method is based on a harmonic domain representation of displacements and forces and the coupling between harmonics at component interfaces. A processor generates the required coupling matrices and inertial loading vectors for each harmonic. A DMAP Alter assembles the matrices, solves for the harmonic displacements and provides plots of the displacements and forces over the two revolution period of the engine. A comparison is made between an analytic solution for a rigid component engine and the simulation procedure with both rigid and flexible components.

ANALYSIS OF SPACE STATION DYNAMICS USING MSC/NASTRAN (Acrobat 1.80MB) #1187, 27 pgs.
John P. Raney--NASA Langely Research Center, Virginia
M. Kaszubowski and J. Kirk Ayers--PRC Kentron, Inc, Virginia

ABSTRACT: The Space Station Office at the NASA Langely Research Center is responsible for, among other things, conducting and coordinating analyses and trade studies which focus on Space Station structural dynamics and attitude control (station pointing). During the now-completed preliminary design phase, Phase B, of the Space Station project several studies were performed.

One study, led by Structures Division, focused on determining truss bay size by examining the relative merits of a 9 foot and a 5 meter bay size from the standpoint of station attitude control. In another study, the dynamics of a proposed Space Station precursor experiment using protoflight hardware were examined , while a companion study determined the structural effects of firing the Orbiter's primary reaction control system jets with a large structure attached.

In a more recent study, the vibration characteristics and attitude control qualities of the Space Station were determined for critical configurations during assembly and buildup. The purpose of this paper is to highlight the methodology and results of Reference 4 and, coincidentally, to discuss the environment within which MSC/NASTRAN is utilized at the Langley Research Center.

EMPLOYMENT OF MSC/STI-VAMP FOR DYNAMIC RESPONSE POST-PROCESSING (Acrobat 1.75MB) #1287, 25 pgs.
Robert N. Coppolino and David F. Bella--MSC.Software Corporation

ABSTRACT: Employment of MSC/STI-VAMP as an interactive dynamic response post-processor for MSC/NASTRAN is outlined. A new modification to SOL 3 (Normal Modes Analysis) provides for determination of quasi-static residual vectors, base motion excitation matrices and other modal quantities required by the post-processor. The general operation of a MSC/STI-VAMP dynamic response post-processor is demonstrated for frequency, transient and random response calculation.

EXPERIENCES WITH OPTIMIZATION USING ADS/NASOPT AND MSC/NASTRAN FOR STRUCTURAL DYNAMICS (Acrobat 1.39MB) #1387, 15 pgs.
Warren C. Gibson--CSA Engineering, Inc., California

ABSTRACT: ADS/NASOPT is an optimization code which works with MSC/NASTRAN to produce optimal structural designs. The user creates a design model which defines design variables (element properties), constraints (limits on displacements, stresses, natural frequencies, buckling loads,or weight), and an objective, a function to be minimized. This paper describes experiences in using ADS/NASOPT in optimizing a complex structure to weight and frequency constraints.

DYNAMIC RESPONSE OPTIMIZATION USING MSC/NASTRAN (Acrobat 2.16MB) #1487, 24 pgs.
M. Chargin and H. Miura--NASA Ames Research Center, California
G. Clifford--Cray Research, Inc., Minnesota

ABSTRACT: Numerical optimization techniques are used to modify the dynamic response at a specified point(s) of a structure due to a steady state narrow band excitation. Calculation of steady states vibration amplitude is reduced to the solution of linear equations with complex coefficients. The sensitivity of the dynamic amplitudes with respect to the structural parameter perturbations can be computed with the same technique as the one used in the static displacement sensitivity without requiring eigenvector sensitivity. Approximate models for critical structural responses are created based on the sensitivity data to reduce the amount of computational effort and to enable the design of structures of practical scale and complexity. This approach is general in that it accommodates static, dynamic, and frequency constraints simultaneously as long as their computational models are available. It can be used in optimizing mass distribution as well as stiffness modifications of practical structures.

Two example problems are solved to demonstrate the capability of these techniques. One is a simply supported beam subjected to a rotating force and static gravity load. The other example is an engine support structure which possesses significant size and complexity. It is loaded by static gravity loads and forces due to rotating mass unbalance.

THE SHAPE OF THINGS TO COME (Acrobat 832K) #1587, 19 pgs.
P.A. Zelenski--MSC.Software Corporation

ABSTRACT: The development of engineering software tools is a very specialized and complex field of endeavor. MSC has long been a leader in the development of Engineering analysis tools and has now embarked on a growth path to include an integrated interactive graphics system into its successful and capable repertoire of software products.

This paper suggests the principles involved in the design and development of such a system. The concept of "form follows function" leads to a discussion of the attributes that good engineering software ought to have and the mechanisms that software developers may use to build those attributes into the software.

Programming techniques involving rapid prototyping, artificial intelligence, new programming languages and the "object oriented" approach are discussed.

The conclusion of this presentation is the realistic and critical observation that all stages of the development activity must be done with the end user in mind. All capabilities added to the system and all techniques used in its developments must bring out the primary premise that "the User is King."

OPTIMIZATION OF THE BUCKLING STRENGTH OF CARBON-REINFORCED CYLINDERS (Oral Presentation) #1687

ABSTRACT: This paper summarizes H. Zimmerman's doctoral dissertation offering an organized approach to optimizing the buckling strength of carbon-reinforced cylinders. Also included are observations on the current and future applicability of composite materials in the European aerospace industry.

PARALLEL STATIC SOLUTION IN FINITE ELEMENT ANALYSIS (Acrobat K) #1787, 7 pgs.
Louis Komzsik--MSC.Software Corporation

ABSTRACT: The availability of parallel supercomputers created some expectations for easy and inexpensive improvements in finite element analysis. It is true that the most time consuming numerical modules of finite element analysis systems can be executed in parallel; however the conversion is not easy because sometimes new algorithms are required, which are suitable for parallelization.

In the following sections we discuss the major theoretical issues of converting finite element code to a parallel machine:

• measurement of performance gain
• the level of parallelization
• interaction with vectorization
• portability

The results presented are from benchmarks executed on CRAY/XMP and IBM 3090 computers with multiple processors.

A TOTAL FINITE ELEMENT MODELING SYSTEM FOR THE MSC/NASTRAN USER (Acrobat 392K), #1887, 3 pgs.
Gil White--Intergraph Corporation

ABSTRACT: The modern structural analyst is often confronted with a multitude of CAD/CAE systems that offer solutions to the problems of finite element model construction, analysis, and results interpretation or postprocessing. The history of computer-aided design and analysis has followed a path that provided for the quickest method for automating specific functions. This evolution has created islands of automation. Various attempts have been made to link segregated databases and form cohesive systems. Some attempts have proven successful but their efficiency is limited. Recent developments in both hardware and software have opened the door to systems of fundamental new design. The industry is now seeing the development of fully standalone workstation platforms that provide new and exciting opportunities for the MSC NASTRAN user.

EFFECTIVE USE OF MSC/NASTRAN PARABOLIC TETRAHEDRAL ELEMENTS (Acrobat 1.02MB), #1987, 8 pgs.
B. William Rudd and David Tompkins--SDRC CAE International, Ohio

ABSTRACT: Tetrahedral elements have traditionally had little use for a number of reasons:

• The linear tetrahedron is clearly to stiff for practical structural analysis applications.
• Traditional mesh generators can not easily generate the elements
• More tetrahedral elements are required to model a give geometric region than hexahedra, and each node typically has more tetrahedral elements attached to it (hence increasing analysis time).
• There are no natural planes of nodes within a tetrahedral model. This makes it difficult to perform certain checks and to review the analysis results.

In spite of the limitations, modern free mesh generation techniques that can generate models with tetrahedral elements very quickly for complex geometries have brought renewed interest in using these elements. There are certainly modeling advantages, but most users are concerned about the analysis results. Since the linear tetrahedron element has a bad reputation, users are understandably wary of using the new parabolic tetrahedron element.

MSC has added a parabolic tetrahedron element to NASTRAN. Although this element has given excellent results, there is a relatively small base of experience. SDRC has had good success in applying it in structural and heat transfer applications, and some of these experiences are documented here.

INTERACTIVE LAMINATE POSTPROCESSING OF NASTRAN STRUCTURAL ANALYSES
(Acrobat 1.46MB) #2087, 15 pgs.
Keith J. Meyer and Steven Rahmann--PDA Engineering, California

ABSTRACT: The analysis of laminated composite structures requires significant ply stress and strain data recovery to determine margins-of-safety. If obtained in batch mode for a large number of plies even a modest structural model will produce boxes of printout. An interactive laminate postprocessing feature in PATRAN was used to recover ply data for an aircraft access door cutout analysis in which several PCOMP directives were used to model increases in laminate thickness around the cutout. Both ply stresses and strains were recovered and the stresses are the same as those (fiber dominated) recovered by NASTRAN. The interlaminar shears differ only in the off-axis or angle plies where a known problem exists. The paper also presents margins-of safety for ply failure analyses based on the Tsai-Wu criteria in graphical format. These enhanced postprocessing features increase significantly the utility of NASTRAN for laminated composite structural design.

MSC/NASTRAN IN A HIGH PERFORMANCE COMPUTER ENVIRONMENT (Acrobat 914K) #2187, 9 pgs.
Ian A. Taylor and John Huseby--Floating Point System

ABSTRACT: MSC/NASTRAN has been available on high-speed computers, such as the FPS M64 Series of Minisupercomputers, for sufficiently long enough to enable the collection of a substantial body of performance results. These results indicate that elapsed job time can be significantly affected by such factors as CPU clock rate, memory and I/O bandwidth, mass memory device utilization, software constructs, and general system parameters.

We examine the performance of a typical MSC/NASTRAN job, in the context of Amdahl's Law, under varying conditions and approaches on the FPS M64 Series. Important conclusions are reached indicating that raw CPU power is not sufficient to guarantee high performance that CPU LOAD and SYSTEM I/O must be balanced, and that judicious application of system software parameters can produce impressive results.

ACCESSING AND DISPLAYING MSC/NASTRAN RESULTS USING A RELATIONAL DATABASE
(Acrobat 789K) #2287, 6 pgs.
Asbjorn Melo, Jim Ross, Richard Russell and Paul McDonald--SDRC CAE International, Ohio

ABSTRACT: Many graphical pre- and post-processing systems allow generation of specific model types and review of specific, predefined results from MSC/NASTRAN. Few if any allow the flexibility to get at the full spectrum of analysis capabilities in MSC/NASTRAN. This paper discusses a flexible approach to generating, accessing, manipulating and displaying data using a relational database. The database is an integral part of the SDRC I-DEAS Supertab® pre-post-processing software. The relational database allows the user to modify the type of model generated, add additional data to the input deck, access and review virtually any result and perform additional calculations for results understanding. A number of examples, such as creating the CHBDY convective heat boundary element, accessing frequency response data and performing fatigue life estimates, are used to illustrate application of the I-DEAS relational database with MSC/NASTRAN.

NASTRAN NONLINEAR ANALYSIS OF STIFFENED WING PANELS (Acrobat 621K) #2387, 6 pgs.
E. Chow--Douglas Aircraft Company--Long Beach

ABSTRACT: MSC/NASTRAN nonlinear analysis capability has been studied by many investigators. In this paper, Solution 66 of MSC/NASTRAN Version 64A is used to analyze stiffened panels of the wing in a large transport aircraft. Material nonlinear buckling results, obtained from Solution 66 and its DMAP Alter for nonlinear eigenvalue extraction, shows substantial agreement with the experimental test data of stiffened panel under compression. The paper also addresses the application of nonlinear analysis of MSC/NASTRAN in material evaluation and selection of structures.

PRESSURE FOLLOWER MATRIX FOR GEOMETRIC NONLINEAR FINITE ELEMENT ANALYSIS
(Acrobat 1.16MB) #2487, 23 pgs.
David N .Herting--MSC.Software Corp.
Gernot W. Haggenmacher--Consultant

ABSTRACT: The variation of pressure loads due to displacement variations in nonlinear geometric analysis is developed in terms of a tangent finite element matrix. This so-called follower force matrix is significant relative to the normal geometric tangent matrices for many problems and improves the convergence of the nonlinear solution. The effects of the follower force matrices are also important for analyzing problems of instabilities and dynamics under pressure, such as containers and tires where an accurate tangent matrix is required. Special finite elements are implemented in MSC/NASTRAN to represent the tangent stiffness of pressure loads on surfaces. Results shown for buckling solutions and normal mode analysis, indicate dramatic improvement in the results.

USE OF MSC/NASTRAN FOR THE THERMAL ANALYSIS OF THE SPACE SHUTTLE ORBITER BRAKING SYSTEM (Acrobat 1.59MB) #2587, 19 pgs.
James Shu and David McCann--Lockheed-EMSCO, Texas

ABSTRACT: The MSC/NASTRAN thermal capabilities are being employed to calculate the space shuttle orbiter braking system thermal margins and to analytically verify the current beryllium brake hardware improvements and the new structural carbon brake design.

MSC/NASTRAN thermal capabilities, transient thermal (SOL.89) and linear stress analysis (Sol. 24), are being used to conduct thermal transient and thermal stress analysis of this complex system. Three finite element models have been created to investigate the spacial and temporal temperature variations in the brake stators and the complete brake system, and to determine thermal and mechanical stress distributions in the brake stator during the braking process.

During the course of this investigation, the thermal capabilities of MSC/NASTRAN have truly been put to a thorough test. Man modeling difficulties have had to be overcome and several deficiencies in the program were discovered. This paper discusses the modeling techniques, solution methods, analytical results, comparisons with SINDA results, and experience gained in using solutions 89 and 24 for this type of application.

THE USE OF MSC/NASTRAN TO DETERMINE THE IMPACT RESPONSE OF A REACTOR CORE DUE TO SEISMIC LOADING (Acrobat 1.16MB) #2687, 13 pgs.
R.G. Hill--Advanced Nuclear Fuels Corp., Washington

ABSTRACT: The finite element analysis methodology used to determine the nonlinear mechanical response of pressurized water reactor (PWR) fuel assemblies is described. The models include nonlinearities such as impacting among the various structural components and permanent deformation of fuel assembly spacer grids during impact loading. The primary results obtained are fuel assembly impact forces and spacer grid crushing loads. The fuel assembly is modeled using a modal synthesis simulation. A combination of finite element representation of the fuel assembly and experimental results is used to develop this model. The synthesized fuel assembly is then combined with nonlinear spacer grid models to form the overall core response model for evaluation with MSC/NASTRAN. The applicability of this finite element analysis methodology is demonstrated by evaluation of a Nuclear Regulatory Commission (NRC) standard problem.

A STUDY OF THE THERMO-ELASTIC BEHAVIOR OF A CONTROLLED THERMAL EXPANSION MODULE USING LINEAR FINITE ELEMENT THEORY IN MSC/NASTRAN (Acrobat 5.61MB) #2787, 43 pgs.
F.W. Palmieri--Palmier Consulting Company, Inc.

ABSTRACT: Due to the mismatch in the coefficients of thermal expansion of leadless chip carriers and printed wire boards, cyclic changes in ambient temperature create thermal strains in solder joints which lead to premature fatigue failures. One method of precluding these failures is to manufacture electronic modules which consist of printed wire boards laminated to low expansivity metal sheets, known as controlled thermal expansion modules. It was the purpose of this study to utilize finite element techniques to qualify the relative advantage of various design alternatives by investigating the effect of variations in two design parameters (i.e., bond and face sheet thickness). Analysis of test results show good correlation of finite element predictions and experimental results.