1993-1999 MSC Users' Conference Proceedings

Categories

Nonlinear Analysis

BUCKLING AND GEOMETRIC NONLINEAR ANALYSIS OF A TIE ROD IN MSC/NASTRAN VERSION 68 (Acrobat 630K) #1594, 15 pgs.
George Campbell -- Ford Motor Company
Wen Ting -- Ford Motor Company
Peyman Aghssa -- The MacNeal-Schwendler Corporation
Claus C. Hoff -- The MacNeal-Schwendler Corporation

ABSTRACT: The improved geometric capability in MSC/NASTRAN Version 68 is tested on a large scale finite element model of a tie rod. The static buckling load of a tie rod is analyzed. The results of the finite element model are compared with experimental results. The analysis is performed in three steps. First, linear buckling is analyzed with SOL 105. Second, a nonlinear static analysis with arc-length method is performed in SOL 106 to determine the instability behavior of the structure. In the last step, a nonlinear buckling analysis is done with restart into SOL 106 to determine the nonlinear buckling load. The tie rod has a strongly nonlinear behavior which is due to material yield and geometric nonlinear effects. It is shown that MSC/NASTRAN's computed buckling load agrees well with the experimental buckling load.

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, 22 pgs.
S. Basic--Morrison Knudsen Corporation

ABSTRACT: This paper extends applicability of the fundamental theory of compressed shells to the refinement of a linear finite element model.

In light of Von Karman's, Trefftz's, Cox's and Marguerre's interpretations of elementary elastic instabilities, the compression end-load member quad element thicknesses have been determined to take into account, with a reasonable degree of approximation, the main non-linear responses of a shell subjected to compression. Consequently, the Modal and the Static Finite Element Method Results will be improved.

FULLY NONLINEAR HYPERELASTIC ANALYSIS OF NEARLY INCOMPRESSIBLE SOLIDS: ELEMENTS AND MATERIAL MODELS IN MSC/NASTRAN (Acrobat 1MB) #2995, 16 pgs.
Katerina-D. Papoulia--MacNeal-Schwendler 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.

A NEW METHOD DEVELOPMENT TO PREDICT BRAKE SQUEAL OCCURRENCE (Acrobat 453K) #1494 , 12 pgs.
Lajos I. Nagy -- Ford Motor Company
James Cheng -- Ford Motor Company
Yu-Kan Hu -- BQUAD Engineering, Inc.

ABSTRACT: A new method to predict brake squeal occurrence was developed by MSC under contract to Ford Motor Company. The results indicate that the stability characteristics of this disc brake assembly are governed mainly by the frictional properties between the pads and rotor. The stability is achieved when the friction coefficient of the pads is decreasing as the contact force increases. Based on the results, a stable brake system can be obtained without changing the brake structure by incorporating the appropriate frictional coefficient in the brake system. The method developed here can be also used as a tool to test the quality of any brake design in the early design stage.

NONLINEAR ANALYSIS OF FREE FLIGHT ROCKETS USING MSC/NASTRAN (Acrobat 511K) #3694, 16 pgs.
David S. Livshits -- TAAS - Israel Industries Ltd.
David Saltoun -- MSI Engineering Software Ltd

ABSTRACT: A finite element model for nonlinear dynamic analysis of a free flight rocket is developed in this paper. The rocket response time history is calculated as a result of aerodynamic loads, dynamic imbalance and thrust misalignment. The aerodynamic loads are calculated using combinations of NOLINs. The model can perform aeroelastic stability analysis and loads distribution calculations as a function of time. A nonlinear aerodynamic behavior can be included in the model for large angles of attack.

PRODUCTION ORIENTED NONLINEAR ANALYSIS OF SOLIDS AND STRUCTURES (Acrobat 917K) #0394, 14 pgs.
H. D Hibbitt -- Hibbitt, Karlsson & Sorensen, Inc.

ABSTRACT: Requirements for modeling nonlinear effects in routine analysis applications have grown to the point where "general purpose" finite element-based programs are expected to offer significant nonlinear modeling capabilities. One result of this market demand has been this year's announcement of the establishment of a long term relationship between The MacNeal-Schwendler Corporation and Hibbitt, Karlsson Sorensen, Inc. ("HKS"), whereby MSC will package a substantial set of the capabilities offered by HKS's ABAQUS/Standard program with MSC/ARIES, to supplement the nonlinear capabilities of MSC/NASTRAN and MSC/DYTRAN for applications in solid and structural analysis. MSC will provide full support of these capabilities, as it does for its other analysis products.

Nonlinear effects introduce a broad range of issues which might deter the analyst who is unfamiliar with this type of problem from trusting such modeling as a basis for achieving design goals and schedules. Once nonlinearity is introduced into a model, uniqueness and stability of the solution may be (and often are) lost, and issues of convergence, choice of nonlinear solution algorithm, etc. must be considered. Nevertheless, the analyst may have no choice but to face up to these problems: he cannot analyze a design for certain events, or design the manufacturing process to create a product, without considering nonlinearity. The viewpoint taken in this paper is that, with mature software such as the ABAQUS-based products that MSC now offers, some nonlinear effects of practical importance can be modeled on a routine, production, basis. The spectrum of difficulty ranges from such cases all the way to problems that are still research topics. One purpose of this paper is to suggest what level of difficulty might be anticipated in modeling various nonlinear effects that are commonly encountered, thus providing some guidance to the analyst in determining the extent to which expertise is needed in order to utilize nonlinear analysis software.

SPACE STATION FREEDOM SOLAR ARRAY WING NONLINEAR TRANSIENT ANALYSIS OF PLUME IMPINGEMENT LOAD (Acrobat 767K) #3594, 17 pgs.
C. C. Tang -- Lockheed Missile & Space Company

ABSTRACT: This paper describes the nonlinear transient analysis of the Space Station Freedom Solar Array (SSFSA) wing for on-orbit plume impingement bad due to Space Shuttle berthing. Design features and the finite element model of the SSFSA wing are briefly described. Nonlinear transient analysis is performed using MSC/NASTRAN SOL 99 (V67) with blanket tensioning accomplished by restarting with static solution results. The blanket tensioning is from tension mechanisms. Transfer function (TF), scalar point (SPOINT), nonlinear load (NOLIN1), and damper (CDAMP2) are used to describe the nonlinear characteristics of the tension mechanisms. Stiffness updates for capturing the nonlinear geometrical stiffness changes due to tension variation in the solar array blankets is utilized in the iterative nonlinear solution. Results, when compared to that from linear transient analysis, showed that the beam-column effect for the slender mast of the solar array wing is insignificant, and the assumptions made in the linear transient analysis are acceptable.

STABILITY ANALYSIS OF PERFECT AND IMPERFECT CYLINDERS USING MSC/NASTRAN LINEAR AND NONLINEAR BUCKLING (Acrobat 1.48MB) #2795, 16 pgs.

M. H. Schneider, Jr.--McDonnell Douglas Aerospace

R. J. Feldes--McDonnell Douglas Aerospace

J. R Halcomb--MacNeal-Schwendler

C.C. Hoff--MacNeal-Schwendler

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, 21 pgs.

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. Nonlinsar 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/NASTRmN SOL 106 (V67.7) are described in this paper.

THREE-DIMENSIONAL SLIDELINE CONTACT IN VERSION 68 (Acrobat 553K) #1694, 15 pgs.

Rakesh Allahabadi -- The MacNeal-Schwendler Corporation

Dianxiang Xiang -- The MacNeal-Schwendler Corporation

Detlef Liebe -- MSGmbH

Glenn C. Grassi -- The MacNeal-Schwendler Corporation

Peyman Aghssa -- The MacNeal-Schwendler Corporation

Behrooz K. Shahidi -- Ford Motor Company

ABSTRACT: Slideline contact was first introduced in Version 67.5 of MSC/NASTRAN through a standalone DMAP alter - 'contact.v675' available in the /misc/sssalter directory. This DMAP alter is applicable only for solving static problems. Starting with Version 68, the slideline contact capability is available for solving both nonlinear static (SOL 106) and nonlinear transient (SOL 129) problems as a standard feature. The use of the DMAP alter is no longer required.

This paper shares the experience of using the MSC/NASTRAN slideline contact capability. It (a) demonstrates the capability through real life applications and (b) provides guidelines for effective usage.

VULNERABILITY ANALYSIS OF AIRCRAFT FUSELAGE SUBJECTED TO INTERNAL DETONATIONS

(Acrobat 990 K) #3494, 17 pgs.

Geetha Bharatram -- Wright Patterson AFB

Capt. Scott A. Schimmels -- Wright Patterson AFB

Dr. Vipperla B. Venkayya -- Wright Patterson AFB

ABSTRACT: The Air Force, in support of the FAA's (Federal Aviation Administration) Aircraft Hardening Program (AHP), is conducting an extensive test program involving simple cylinders to full scale aircraft such as the B-52s as well as representative commercial airplanes. The purpose of this program is to ascertain the extent of the damage caused by internal explosions and to develop strategies to protect the safety of the passengers. The effects of the internal explosion are very complex, and the tests alone can not provide an adequate understanding to develop protection strategies. The purpose of this paper is to present the analysis results of the B-52 aircraft subjected to internal explosions. In addition analysis results are compared to those obtained from the test program conducted at Davis Monthan Air Force Base.

Two types of analysis will be addressed in this paper:
 
1. Fluid structure interaction (blast pressures and airframe interaction) using MSC/DYTRAN.
2. Joint and buckling analysis of a B-52 panel using MSC/DYTRAN.

The ultimate goal of the proposed analysis is to develop a vulnerability map of the entire fuselage. This map can be used to make cost effective decisions on hardening of the aircraft against bomb blasts.

Nonlinear Applications

LARGE DEFORMATION HYPERELASTIC ANALYSIS IN MSC/NASTRAN VERSION 67.5 (Acrobat 586K) #5693, 13 pgs.

Katerina-D. P. Papoulia -- The MacNeal Schwendler Corporation

Steve S. Hsieh -- The MacNeal Schwendler Corporation

ABSTRACT: Version 67.5 of MSC/NASTRAN includes finite deformation analysis for problems that involve large strain and large rotation. The material law is Green-elastic (hyperelastic) with a strain energy function of the generalized Rivlin type, extended to include the effect of compressibility at the nearly incompressible limit. The stress-strain relations are discussed in some detail as well as the approach taken to avoid the occurrence of volumetric locking. Examples are presented that illustrate the capabilities of the formulation to model problems with large strain and large rotation.

NONLINEAR SEISMIC ANALYSIS OF BRIDGES: PRACTICAL APPROACH AND COMPARATIVE STUDY (Acrobat 721K) #5793, 19 pgs.

Yohchia Chen, Ph.D., P.E. -- Pennsylvania State University

ABSTRACT: A simplified numerical model with an efficient computational scheme is proposed for nonlinear seismic analysis of bridges. The results obtained from the simplified model are compared to those from the refined model and other methods. The proposed model is shown to be especially effective for obtaining maximum responses, and is practical and economical. Effects of bridge skews on responses are also carefully examined. The paper concludes with a number of bridge examples and design recommendations.

NONLINEAR SUPERELEMENT ANALYSIS TO MODEL ASSEMBLY PROCESSES (Acrobat 1.09MB) #5993, 18 pgs.

Mark J. Stone -- Eastman Kodak Company

Vic Genberg -- Eastman Kodak Company

ABSTRACT: It is often desirable to know the residual effect of assembly processes on the final product. Although only a linear static analysis may be desired, the changes in loads and constraints throughout the assembly process prevent the use of a simple linear solution. If the product is fairly complex, it is often necessary to use a large finite element model. This paper describes the use of a single nonlinear solution (MSC/NASTRAN V66A SOL 66) using superelements to analyze a large model subjected to varying loads and constraints. As the load and support change in each subcase, the structural deflection changes by adding to or subtracting from the previous deformation state. The model used represents the High Resolution Mirror Assembly (HRMA) for NASA's Advanced X-Ray Astrophysics Facility (AXAF). The process represented is the alignment and assembly of the AXAF mirrors to the support structure.

SNAP-THROUGH BUCKLING ANALYSIS OF A SHALLOW GEODESIC DOME USING MSC/NASTRAN (Acrobat 758K) #5893, 24 pgs.

S. Loganathan, BSc Eng Civil (Hons), M. Eng, PhD -- BHP Engineering

R.C. Morgan, BE, M.Eng Sc MIE Aust -- BHP Engineering

ABSTRACT: This paper illustrates the nonlinear analytical and experimental study of a shallow geodesic dome comprising thin walled circular hollow sections. A 156-member shallow geodesic dome that has a rise to span ratio of 1:10 (i.e. a rise of 0.6m to span of 6.0m) was constructed and tested experimentally. The present investigation is focused to study the snap-through phenomena of the dome subjected to a static load at the centre of the dome. The dome is discretized as 156 beam elements and its perimeter supports are assumed as ideal pin supports. Displacement control of the load point was employed to trace snap-through and this prevents any possible dynamic jump in the vicinity of the snap-through region. Experimental observation shows that the members near the loading point deformed severely under the applied load without resulting in any damage to the welded joints, apart from material yielding in certain members.

MSC/NASTRAN Version 67 installed on the BHP Research CRAY-YMP (EL) SuperComputer was used as the numerical tool to validate the complex nonlinear behaviour of the dome. The results of geometrical and material nonlinear analysis of the dome from MSC/NASTRAN compare well with the experimental results for cases where the displacements can be reasonably measured with the linear transducers employed. A second nonlinear large displacement analysis was carried out with MSC/NASTRAN on a Schwedler dome in which the connection details are based on the Harley Spaceframe structures. The Schwedler dome considered has a rise-to-span ratio of 1:4 (i.e., a rise of 2.5 m to span of 10.0 m).

Nonlinear Methods

IMPROVEMENTS IN LINEAR BUCKLING AND GEOMETRIC NONLINEAR ANALYSIS FOR MSC/NASTRAN'S SHELL ELEMENTS (Acrobat 543K) #4993, 26 pgs.

Claus C. Hoff -- The MacNeal-Schwendler Corporation

ABSTRACT: This paper presents an improved approach for linear buckling and geometric nonlinear analysis in MSC/NASTRAN. The differential stiffness and the internal forces of the QUAD4 and TRIA3 shell elements have been corrected in MSC/NASTRAN Version 68. The linear stiffness of the shell elements has not been changed. With the corrections in Version 68, two major capabilities have been improved. The eigenproblem in linear buckling analysis of thin shells is free of spurious modes which have been observed in Version 67.5 and earlier Versions. Furthermore, the shell elements converge better in geometric nonlinear analysis. The theoretical concept of the corotational formulation in MSC/NASTRAN is summarized briefly. The corrections of the internal forces and tangent stiffness are explained. Examples are presented which illustrate the improved behavior of the shell elements in Version 68 as compared to Version 67.5.

NONLINEAR ANALYSIS USING A MODAL BASED REDUCTION TECHNIQUE (Acrobat 530K) #5193, 13 pgs.

D. Shalev -- Israel Aircraft Industries

A. Unger -- Israel Aircraft Industries

ABSTRACT: This paper presents a solution to nonlinear formulated problems using eigenfunctions computed by a linear free vibration solution. The system of equations is extremely reduced. The solution is unique in its formulation as the governing equations represent the problem continuously and do not require an iterational or incremental solution. Energy consideration is used and the Ritz method is applied to render the governing equations. An integrated system was built in which the current analysis functioned as a MSC/NASTRAN dummy module integrated with MSC/NASTRAN SOL 3 and SOL 24 to render the mode shapes and geometrical and material properties respectively. Several numerical examples are presented and compared to solutions from the literature.

NONLINEAR GAP-TYPE SOLUTIONS USING A LINEAR F.E.A. CODE (Acrobat 733K) #5093, 13 pgs.

R. D. Hilton -- Bell Helicopter Textron

ABSTRACT: The most common form of structural Finite Element Analysis (FEA) is the linear static solution, in which the behavior of each element can be characterized as a linear equation. Linear static FEA cannot be used for problems with nonlinear gap-type elements, as their load vs. deflection behavior cannot be expressed with a single linear equation. Examples of gap-type elements include a cable (an axial element which can transfer tension between its ends, but not compression) and a bearing contact (two interfering surfaces that can compress against each other, but do not adhere when separated). For a gap element, the load vs. deflection equation depends on the sense and magnitude of deflection each loading condition imposes on the element.

Many common FEA codes do not support gap elements; for those that do, adding a gap element complicates the solution by requiring extensive changes to the linear model, and by increasing the CPU time required (often several times over). As the gap behavior can vary from one loading condition to the next, a separate solution for each condition must be obtained.

The Enforced Strain Method uses an approach in which a compensating enforced strain is used to give linear elements gap-like load vs. deflection behavior. The technique can be used with linear FEA codes that do not support gap elements, or can be used as an alternate solution for gap-capable codes. Benefits of the method are reduced CPU requirements, the ability to run multiple loading cases, and no need for superelements.

The Enforced Strain Method is a more efficient gap solution, particularly when a given model has a relatively small proportion of gaps, and when multiple loading conditions are required. An example problem is presented in which the required CPU time was reduced by 43% as compared to the fastest MSC/NASTRAN gap solution. Though presented as a program external to MSC/NASTRAN, the method could be implemented through DMAP alters to the standard linear static solution. Run as a DMAP, CPU time savings for the example problem would have increased from 43 to 66% as compared to MSC/NASTRAN's nonlinear gap Solution 66.

THREE DIMENSIONAL SLIDELINE CONTACT (Acrobat 938K) #4893, 22 pgs.

Rakesh Allahabadi --The MacNeal-Schwendler Corporation

ABSTRACT: Slideline contacts in MSC/NASTRAN model the separation and sliding of finite amplitude between three dimensional deforming bodies. The modeling of contact requires the user to specify slideline planes in which the interaction can occur. The sliding between bodies occur along lines, specified by lists of grid points, within the slideline planes. The bodies can have large relative motions within the slideline planes. However, relative motions outside the slideline planes are ignored; therefore, they must be small compared to a typical slideline element.

The finite element formulation for both contact and friction is based on the penalty method. But, the user need not specify the penalty values as the program automatically calculates them. The slide line element force vector and the stiffness matrix are derived from a variational principle using a consistent linearization procedure. The formulation is capable of modeling nonlinear contact geometry and inelastic material behavior including large deformation.

The three dimensional slideline contact is a standard feature in Version 68 for quasi-static analyses (SOL 106). However, a special DMAP is required for Version 67.5.

Nonlinear Transient Response

APPLICATION OF MSC/DYTRAN TO THE HYDRODYNAMIC RAM PROBLEM (Acrobat 1.43MB) #1295, 20 pgs.

Geetha Bharatram--Wright Patterson AFB

Capt. Scott A. Schimmels--Wright Patterson AFB

Dr. Vipperla B. Venkayya--Wright Patterson AFB

ABSTRACT: An analysis method for studying hydrodynamic ram effects in a fluid-filled structure is developed using MSC/DYTRAN. In this study a high velocity projectile is shot into a structure, depositing energy into the contained fluid and transmitting an impulse to the structure. The coupled fluid-structure interaction response is studied using MSC/DYTRAN. An Arbitrary Lagrange Euler (ALE) coupling is defined between the structure and the internal fluid and a general coupling is defined between the penetrating projectile and the fluid.

A second case is also studied, in which the penetrating projectile explodes at a predetermined time inside the fluid. Combined effects of the explosive blast and the hydrodynamic ram effects are studied. Preliminary results are presented in this paper.

EXTENDING MSC/DYTRAN FOR THE NUMERICAL SOLUTION OF THE NAVIER-STOKES EQUATIONS (Acrobat 1.08MB) #5295, 21 pgs.

Ortwin Ohtmer--California State University, Long Beach

ABSTRACT: MSC/DYTRAN contains two finite element processors, Lagrangian (finite element) and Eulerian (finite volume).

In the Eulerian processor, the grid points are fixed in space and the elements are simply partitions of the space defined by connected grid points. The Eulerian mesh is then a fixed frame of reference. The material of a body under analysis moves through the Eulerian mesh, and the mass, momentum, and energy of the material is transported from element to element. In ALE applications, the Eulerian gridpoints may move in space, whereby the material flows through a moving and deforming Eulerian mesh. It is important to realize that the Euler gridpoint motion is uncoupled from the material motion.

MSC/DYTRAN is efficient and extensively vectorized. It provides cost-effective solutions on the latest generation of computers ranging in size from engineering workstations to the largest supercomputers.

Based on many publications, summarized by H.Oertel Jr., the FINITE VOLUME Method, implemented in MSC/DYTRAN is successfully applied today for the numerical fluid flow simulation. Therefore it makes sense to modify and extend MSC/DYTRAN to solve the three-dimensional NAVIER-STOKES Equations. The governing equations in integral form of conservation are applied for the computation of the compressible airfoil-flow within the FINITE VOLUME Method using MSC/DYTRAN and the menu-driven ME-Software Bank to demonstrate the numerical procedure.

NONLINEAR IMPACT ANALYSIS OF INTERNATIONAL SPACE STATION ALPHA MODULE BERTHING USING MSC/NASTRAN (Acrobat 1.59MB) #5095, 20 pgs.
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.

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.

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.

Numerical Methods

A BREAKTHROUGH IN PARALLEL SOLUTIONS OF MSC.SOFTWARE (Acrobat 260K) #2899, 12 pgs.
Louis Komzsik, Paul Vanderwalt, Petra Poschmann, and Reza Sadeghi--MSC.Software Corporation
Stefan Mayer--MSC.Software Corporation, München, Germany

ABSTRACT: More than a decade ago MSC offered the first parallel production system of MSC.NASTRAN. During this decade MSC has intensified its effort on parallel processing and is now ready to deliver MSC.NASTRAN V70.7 and MSC.MARC V9.1, both of which contain very important new parallel features.

This paper describes these exciting features and provides preliminary performance results. We believe that these systems mark the best in parallel performance in commercial finite element analysis ever and present a breakthrough in parallel computing in our market.

DISTRIBUTE MEMORY PARALLEL MSC.NASTRAN ON AN IBM WORKSTATION CLUSTER AT FORD COLOGNE (Acrobat 130K) #3099, 16 pgs.
Ulrich Viersbach, Dr. Matthias Weinert, and Christian Wilmers--Ford Werke Aktiengesellschaft, Germany
Dr. Stefan Mayer--MacNeal-Schwendler GmbH, Germany

ABSTRACT: MSC.NASTRAN is the main structural FE code and the second most used CAE code on compute servers at Ford worldwide. To reduce costs, alternative ways of computing are being investigated such as using idle cycles on the large number of available Ford workstations. While smaller analyses run efficiently on single workstations, more complex calculations require larger computer resources as potentially available with several workstations clustered together using a distributing memory parallel code.

The presented paper outlines results from evaluating and benchmarking a V70.7 development version of the distributed memory parallel MSC.NASTRAN code on an IBM RS/6000 model 590 workstation cluster at Ford Cologne. It covers linear static (solution 101), normal modes (solution 103) and direct frequency response (solution 108) analyses which were carried out for the first time ever on a workstation cluster. Cluster turnaround times are compared with those on IBM compute servers and Cray C90.

The evaluation showed that the development version has great potential for typical jobs used for the analysis of Ford body structures. Good speed-up with an increasing number of processors is achieved on the workstation cluster. The cluster with 8 workstations showed better turnaround times than the Cray C90 for SOL101 benchmark cases. When using latest technology workstations the cluster is expected to show even better turnaround times with also superior performance to the C90 for SOL103 and SOL108. The turnaround target of overnight completion could be achieved with 8 cluster workstations for all benchmark cases. The IBM SP compute server at MSC.Software's office in Los Angeles which is equipped with similar processors as the cluster workstations showed similar performance as the cluster. The IBM SP compute server at IBM's benchmark center at Poughkeepsie/USA using 8 latest technology processors and a superior I/O subsystem was performing better than the workstation cluster with 8 processors and the Cray for all benchmark cases.

As next steps Ford is planning to carry out runs with the distributed memory parallel version 70.7 on a Ford compute server once this version is officially released and consider production implementation depending on results. Ford is also planning to evaluate the code with our largest CAE models on the above workstation cluster and in a production environment. Ford will encourage MSC.Software to implement several improvements to MSC.NASTRAN such as the integration of the code with a workload management package to enhance cluster robustness.

NVH

ACOUSTIC PREDICTION MADE PRACTICAL: PROCESS TIME REDUCTION WITH PRE/SYSNOISE, A RECENT JOINT DEVELOPMENT BY MSC & LMS (Acrobat 260K), #3699, 10 pgs.
L.Cremers, O. Storrer, and P. van Vooren--LMS International NV

ABSTRACT: Finite element models for structural dynamic analysis and boundary elements models for acoustic radiation analysis have different meshing requirements. Acoustic boundary element analysis requires a mesh of the sound radiating surface with a uniform discretization of about six degrees of freedom per shortest acoustic wavelength whereby small details, relative to the acoustic wavelength, can be omitted. In most cases the acoustic analyst needs to generate the acoustic boundary element mesh from the original detailed structural finite element mesh as no geometry information is available for the model. This so-called mesh coarsening process involves in general four phases, i.e. mesh processing, subdomaining, creation of surfaces and re-meshing. Pre/SYSNOISE, a joint-development by MSC and LMS, is a powerful tool to help the acoustic analyst in this tedious task. It combines both the geometry and finite element meshing tools of v8.0 and an advanced set of automatic mesh coarsening routines. The different techniques involved in the mesh coarsening process will be explained along with a practical real-life example.

BRAKE ANALYSIS AND NVH OPTIMIZATION USING MSC.NASTRAN (Acrobat 423K) #1699, 15 pgs.
Dr. Himanshu Misra--NEC Systems, Inc.
Dr. Wayne Nack--General Motors Corporation
Dr. Tom Kowalski--MSC.Software Corporation
Dr. Louis Komzsik--MSC.Software Corporation
Dr. Erwin Johnson--MSC.Software Corporation

ABSTRACT: Brake Analysis and NVH (Noise, Vibration and Harshness) Optimization have become critically important areas of application in the Automotive Industry. Brake Noise and Vibration costs approximately $1Billion/year in warranty work in Detroit alone. NVH optimization is now increasingly being used to predict the vehicle tactile and acoustic responses in relation to the established targets for design considerations. Structural optimization coupled with frequency response analysis is instrumental in driving the design process so that the design targets are met in a timely fashion. Usual design targets include minimization of vehicle weight, the adjustment of fundamental eigenmodes and the minimization of acoustic pressure or vibration at selected vehicle locations.

Both, Brake Analysis and NVH Optimization are computationally expensive analyses involving eigenvalue calculations. From a computational sense and the viewpoint of MSC.Nastran, brake analysis exercises the CEAD (Complex Eigenvalue Analysis Dmap) module, while NVH optimization invokes the DSADJ (Design Sensitivity using ADJoint method DMAP) module. In this paper, two automotive applications are presented to demonstrate the performance improvements of the CEAD and DSADJ modules on NEC vector-parallel supercomputers. Dramatic improvements in the DSADJ module resulting in approx. 8-9 fold performance improvement as compared to MSC.Nastran V70 were observed for NVH optimization. Also, brake simulations and experiences at General Motors will be presented. This analysis method has been successfully applied to 4 different programs at GM and the simulation results were consistent with laboratory experiments on test vehicles.

FUTURE TECHNIQUES FOR HIGH FREQUENCY NVH (Acrobat 423K) #0799, 11 pgs.
Stan Posey and Cheng Liao, PhD--SGI Mtn View, CA
Christian Tanasescu, PhD--SGI Munich, GR

ABSTRACT: The use of NVH analysis provides essential benefits towards designing vehicles for ride comfort and quietness, an increasingly competitive advantage in today's global automotive market. Requirements for NVH analysis at increasingly higher excitation frequencies is driving NVH modeling promoters beyond practical limits for conventional NVH methods. This paper examines details behind conventional NVH practice, NVH modeling directions for the future, and an alternative to conventional NVH that will allow future modeling targets to be achieved.

LINEARISATION OF STIFFNESS AND DAMPING CHARACTERISTICS OF RUBBER VANISHES IN VEHICLE DYNAMICS BY USING FREQUENCY RESPONSE ANALYSIS OF MSC.NASTRAN (Acrobat 780K) #1399, 14 pgs.
Dr. Plank and Dr. Merk--AUDI AG
Dr. Stefan Dömök--Peters & Zabransky, Germany

ABSTRACT: For vehicle dynamics analysis detailed modelling of bushes is necessary. The following paper describes different possibilities to use measurement data of rubber bushes by linearisation of stiffness and damping characteristics in frequency response analysis.

A NONLINEAR SIMULATION OF CAR VIBRATION BY MSC/NASTRAN (Acrobat 943K) #2999, 12 pgs.
Sergey Sergievsky and Sergey Purgin--OJSC "GAZ"
Boris Shatrov--The MacNeal-Schwendler GmbH, Russia

ABSTRACT: Setting the task of creating a modern competitive vehicle, the designers need the more exact estimation of the degree of their design optimum at the early stages of the work. According to this, besides the traditional methods of analysis (static analysis, normal modes analysis and frequency response analysis), the transient response analysis of the car real loading becomes more interesting. This type of analysis provides the data, which are the close analogue to the test results and allows, later on, to go over to the fatigue analysis.

In this article the example of the nonlinear simulation of the car vibration in time domain by MSC/NASTRAN is considered.

SIMULATION OF VEHICLE PANELS WITH MULTILAYER DAMPING TREATMENT (NOT PRESENTED) (Acrobat 1.1MB) #3999, 17 pgs.
Shu Wang and Hinne Bloemhof--Rieter Automotive, Switzerland

ABSTRACT: By using equivalent material parameters and a special equivalent shell element, multi-layer damping treatments can be integrated into simulations of structural vibrations without significan increase of either modelling or computing efforts. The treatment representations are used to conduct classical single-layer FE calculations and determine the frequency response functions of the structure in which the individually treated panels (non-flat) are now included. The procedure presented here does not increase the number of active degrees of freedom, so that it is possible to include the effect of these treatments in large system level models. Two representative examples have been numberically investivgated and a practical aplication of the procedure to a real car floor has been conducted (comparing simulation with measurement). These examples confirm the accuracy, the efficiency and the flexibility of the procedure.

Optimization

CAD BASED OPTIMIZATION (Acrobat 98 K) #0498, 10 pgs.
Celso Barcelos-- MacNeal-Schwendler Corporation

ABSTRACT: In one form or the other one of the primary goals of simulation technology over the years has been to optimize designs. On the whole this has been a manual process involving the generation of multiple mathematical models which have been used to validate a given design, and also to compare different configurations of a design. Although the use of simulation techniques has proven to be an invaluable part of the engineering design cycle they has not yet had the impact everyone desires. In order to help engineers to shorten the design cycle optimization software has been added to existing packages. Even with these new technologies we are still not seeing the kinds of efficiencies that design firms have hoped for. The reasons for why simulation applications, and FEA in particular, have not had their fullest impact to obtain optimized designs are long and varied. Some of these factors include:

• FEA has been hard to use and therefore has been relegated to just a handful of specialist rather than mainstream design engineers.
• Optimization technology itself has been slow to mature.
• The CAD software used for design, and FEA software used for simulation have been stand-alone systems which simply don't talk to each other very well.

This paper describes a system which marries geometric construction tools, simulation software, along with topology and shape optimization technologies which can be utilized by engineers early in the design cycle to reduce the time needed to bring new products to market. By integrating these formerly disparate functions under one umbrella we have taken a giant step forward to achieve efficiencies which were unthinkable just a few years ago.

DESIGN OPTIMIZATION USING HYPERSIZER (Acrobat 5.6MB) #0698, 12 pgs.
Craig Collier, Phil Yarrington, and Mark Pickenheim Collier--Research Corporation

ABSTRACT: This paper identifies an existing commercial solution that MSC users can benefit from for automated stress analysis and sizing. The HyperSizer software is mathematically coupled with MSC/NASTRAN to provide an integrated solution for quick and accurate design optimization. Though specifically developed for the aerospace industry, the approach and methods apply to any industry. A reusable launch vehicle, which contains 7 assemblies, 21 optimization groups, and 203 structural components is used as an example. MSC/NASTRAN is used as the loads model and the entire plane is optimized using HyperSizer's analysis methods that range from closed form, traditional hand calculations repeated every day in industry, to more advanced panel buckling algorithms. Margin-of-safety reporting for every possible failure provides the engineer with a powerful insight into the structural problem. The engineer is able to provide 'real-world' expertise in the optimization process by interacting with HyperSizer for designs on the fly.

DESIGN SENSITIVITY ANALYSIS FOR DURABILITY DESIGN OF BODY STRUCTURES (Acrobat 655KB) #4895, 19 pgs.

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.  

DYNAMIC CORRELATION STUDY TRANSFER CASE HOUSINGS (Acrobat 224KB) 1996, 17 pgs.
William R. Kelley--Borg-Warner Automotive
L. Dean Isley--Borg-Warner Automotive
Thomas J. Foster--Borg-Warner Automotive

ABSTRACT: The process of casting design in the automotive industry has been significantly refined over the years through the capabilities of advanced computer aided design and engineering tools. One of the significant benefits of these computer aided capabilities is the direct access to CAD geometry data, from which finite element models can be quickly developed. Complex structures can be meshed and analyzed over a relatively short period of time. The application of advanced finite element analyses such as structural modification and optimization are often used to reduce component complexity, weight and subsequently cost. Because the level of model complexity can be high, the opportunity for error can also be high. For this reason, some form of model verification is needed before design decisions made in the FEA environment can implemented in production with high confidence. Dynamic correlation, comparison of mode shapes and natural frequencies, is a robust tool for evaluating the accuracy of a finite element model. This paper describes the application of dynamic correlation techniques for verification of mass and stiffness distribution in two complex FEA models of aluminum die cast housings.

FE-OPTIM AND MSC/NASTRAN FOR A FREQUENCY RESPONSE OPTIMIZATION (Acrobat 291K) #0798, 14 pgs.
Dr. Stefan Döemöek and Andreas von Mach--P+Z Engineering GmbH
Dr. Jürgen Merk--AUDI AG

ABSTRACT: FE-OPTIM, a software tool developed by P+Z Engineering GmbH, supports the MSC/NASTRAN optimization (Solution 200) in all its key features. The use and the benefits of FE-OPTIM, combined with MSC/NASTRAN SOL 200, is demonstrated on an example of an AUDI project.

HANDLING OF WELDS IN SHAPE VECTORS GENERATION FOR FINITE ELEMENT SHAPE OPTIMIZATION - A CASE STUDY (Acrobat 33K) #2498, 5 pgs.
Murali M.R. Krishna--DANA Corporation

ABSTRACT: Design analysts, who work with finite element shape optimization, face a daunting task of handling welds. When the designer wants to find the optimum width of the leg of a bracket, which is welded to a base rail, the analyst has to remove the old welds, remodel and re-create new welds after extension of the bracket, and iterate. This method is not suitable for shape optimization. A numerical interpolation method based on 'Autodv', has been recommended to handle welds without remodeling. This method is very effective for finite element shape optimization. A case study has been given to illustrate the method using MSC/NASTRAN.

INNOVATIVE USES OF SYNTHETIC RESPONSES IN DESIGN OPTIMIZATION (Acrobat 701KB) #4995, 14 pgs.
Erwin H. Johnson--MacNeal-Schwendler 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.

LINEAR CORRECTION OF BUCKELED PANELS USING SOL 200 (Acrobat 153K) #0998, 20 pgs.
Michael C Kobold--Northrop Grumman Corporation

ABSTRACT: A method to account for the buckling of skin panels on stiffened shell structures using MSC/NASTRAN SOL 200 linear static optimization is shown. This builds on previous work, shows conservatism of the classical manual methods, and introduces several ways to tackle the problem. The Finite Element Analysis (FEA) involves the comparison of the use of Design Optimization (SOL 200) for effective width and thickness changes, to example A20.4 of Bruhn's text ¹ . The Finite Element model uses a small fuselage section with a height of 50 inches, width of 30 inches. The foundation work for crippling strength calculation software is provided in an Appendix. This work is applicable to curved shell buckling issues in its use of empirical data available in the literature. This method's best implementation will be with p-elements due to their geometry information. The method has application to general stiffened curved panel structural analysis.

MSC/CONSTRUCT - FEATURES AND CAPABILITIES (Acrobat 2.3MB) #0898, 18 pgs.
Dr. Hans Sippel--MSC, Munich

ABSTRACT: For design engineers and analysts MSC/CONSTRUCT¹⁾ provides an exceptionally fast and easy-to-use, conceptional design tool consisting of two options:

• MSC/CONSTRUCT TOPOLOGY is the topology optimization option, which distributes material within a design space envelope based on the optimum load paths.
• MSC/CONSTRUCT SHAPE is the non-parametric shape optimization option, which homogenizes the stress distribution (Fully Stressed Design).

Both of these options are FEM-based and use an efficient optimality criteria technique. In the optimization cycle MSC/NASTRAN is used as the analysis engine. This guarantees reliable results and highest performance.

MSC/CONSTRUCT V2.5 was released in Q3/98. Major highlights are:

1. A graphical user interface within MSC/PATRAN
2. A restart option
3. High performance improvements which significantly increase the throughput
4. An automatic shape basis vector generation for MSC/NASTRAN's SOL 200 by MSC/CONSTRUCT

Especially items 3. and 4. will be presented by customers' real life examples.

NASOPT: A FLEXIBLE OPTIMIZATION CAPABILITY FOR MSC/NASTRAN (Acrobat 64KB) 1996, 14 pgs.
Harold Thomas--Structural Optimization Specialists

ABSTRACT: NASOPT, a software product that runs in conjunction with MSC/NASTRAN, provides a flexible optimization capability for analysis types not supported by Sol 200. The design variables can be any real number in the input data, such as element properties, material properties, and/or loads, as well as shape design variables. The objective function and constraint responses can be any quantity calculated by MSC/NASTRAN. NASOPT runs in conjunction with any structured or unstructured solution sequence, as well as with any DMAP run. In addition to structural optimization, NASOPT can perform parametric studies and system identification. NASOPT was developed under an Partner Interface Development Agreement with The MacNeal-Schwendler Corporation.

NONLINEAR ADAPTIVE ANALYSIS VIA QUASI-NEWTON APPROACH WITH MSC/NASTRAN

(Acrobat 802KB) #1394, 16 pgs.

Ortwin Ohtmer -- California State University, Long Beach

ABSTRACT: The Quasi-Newton method has proven to be the most efficient optimization method. The purpose of this paper is to apply this numerical procedure for optimization problems as well as large deflection analysis and animation. A FORTRAN program developed to calculate constrained optimization problems is used as the basic code within an iterative nonlinear adaptive analysis. The new numerical procedure calculates the displacements of an elastic structure due to given loading conditions. Then the displacements are added to the joint coordinates. In the deformed position the degrees of freedom of the structure are supported and the negative displacements are applied as loadings, to move the structure back to the old undeformed position. The difference of the reaction forces in both positions specifies the geometric nonlinear adaptive loading conditions. These additional forces are applied in an iteration procedure, until equilibrium is achieved. The software ME-BANK (Mechanical Engineering Program-Bank), written in C-language, was developed to execute MSC/NASTRAN and a constrained optimization FORTRAN-code via the SYSTEM-function within an iteration procedure.

NVH OPTIMIZATION ON NEC SUPERCOMPUTERS USING MSC/NASTRAN
(Acrobat 1.7MB) #0599, 14 pgs.
Dr. Himanshu Misra--NEC Systems, Inc.
Dr. Erwin Johnson and Dr. Louis Komzsik--The MacNeal-Schwendler Corporation

ABSTRACT: NVH (Noise, Vibration and Harshness) Optimization has now gained popularity in driving the automotive design process using frequency response analysis of detailed full vehicle structural-acoustic models. Usual design targets include minimization of vehicle weight, the adjustment of fundamental eigenmodes and the minimization of acoustic pressure at selected vehicle locations. Typical NVH Optimization analyses require considerable computational resources, both in terms of cputime as well as memory. The availability of state-of-the-art high performance hardware coupled with software advances and improved methodology has made it possible to solve complicated NVH dynamic response problems very efficiently.

With the introduction of Adjoint Sensitivity Method in V70, MSC/NASTRAN has been increasingly used to perform large NVH Optimization analyses that were unimaginable with the Direct Method. The Adjoint Method usually requires a fraction of the computer resources to produce sensitivity coefficients as compared with the Direct Method. However, for extremely large NVH Analyses, the sensitivity calculations are very demanding in terms of cputime, especially in the context of Vector machines. The calculation of sensitivity coefficients is done inside the DSADJ module of MSC/NASTRAN. For V70.5 and V71, NEC initiated a project with MacNeal-Schwendler Corporation to address the performance bottleneck in the DSADJ module of MSC/NASTRAN. The DSADJ Module Performance Enhancement Project was done with the guidance of MSC and these enhancements are available exclusively on NEC platforms.

The DSADJ module was totally redesigned to improve vectorization and to exploit the vector architecture of NEC SX-4 and SX-5 Series Supercomputers. In this paper, automotive customers’ NVH Optimization applications are presented to demonstrate the performance improvements of the DSADJ module. Dramatic improvements in the DSADJ module resulting in approximately 8-9 fold performance improvement as compared with V70 were observed for NVH Optimization. With the tremendous improvements in the performance of the DSADJ module, and the fact that the eigenvalue analysis involved in NVH Optimization is inherently highly vectorized, NEC Supercomputers are well suited for running large NVH Optimization Analyses using MSC/NASTRAN.

OPTIMIZATION OF DAMPED STRUCTURES IN THE FREQUENCY DOMAIN (Acrobat 625KB) #2893, 18 pgs.
Tsung-hsiun Li -- Iowa State University
James E Bernard -- Iowa State University

ABSTRACT: This paper presents a way to efficiently compute the sensitivities of steady state resonant response and discusses the utility of these sensitivities in redesign and optimization. The resonant response sensitivities are calculated by combining the new capabilities of MSC/NASTRAN v67 in SOL 108,111 and DMAP solution sequences. Two examples illustrate the approach.

OPTIMIZATION TRIAL ANALYSIS OF A JOURNAL/THRUST BEARING STRUCTURE (Acrobat 779KB) #2993, 19 pgs.

Takao Miki -- Mitsubishi Heavy Industries, Ltd.

Mitsuru Kondo -- Mitsubishi Heavy Industries, Ltd.

Fumio Mizuguchi -- Mitsubishi Heavy Industries, Ltd.

Yasuhisa Ogino -- Ryoyu System Engineering, Ltd.

ABSTRACT: Recently, due to the need to minimize structural weight and reduce material cost, several programs are offering optimization capabilities. An optimization capability has been added to MSC/NASTRAN in V66 and has been enhanced in V67. With V68, it will be also possible to optimize the shape of a structure.

This paper presents a trial analysis of optimization capability using the current version (V67) performed on a journal/thrust bearing structure. While supporting the static load and satisfying design constraints on stress and displacement, weight is minimized.

This trial analysis demonstrates the effectiveness of the optimization capability in MSC/NASTRAN in achieving satisfactory results while saving much of the designer time which is currently used in a manual iterative optimization procedure. Improvements such as easiness of use and shape optimization would help to put this capability to extensive use in design.

OPTIMAL DESIGN OF A SIMULATOR MODULE FRAME (Acrobat 384KB) #1595, 6 pgs.
S.C. McIntosh, Jr.--McIntosh Structural Dynamics, Inc.
Erwin H. Johnson--MacNeal-Schwendler 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, 13 pgs.

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.

PARAMETRIC DESIGN/ANALYSIS WITH MSC/PATRAN- A NEW CAPABILITY
(Acrobat 4.7MB) #0899, 17 pgs.
James G. Crose, Douglas A. Marx, Mark Kranz, Paul Olson and Carl Ball--MacNeal Schwendler Corporation

ABSTRACT: This paper describes a new capability of PATRAN to provide for automated parametric analysis in support of complex design processes. Computational resources are available today that can efficiently permit at least an order of magnitude more analysis support to the design process than was available only a few years ago. MSC has been participating in DARPA's RaDEO(Rapid Design Exploration and Optimization) project with Ford Motor Company and the Rocketdyne and St.Louis divisions of Boeing Aircraft Company. That project has developed a new computer program to facilitate robust design processes that involve orders of magnitude more analytical simulation than is typically applied in design. The Robust Design Computational System (RDCS) computer program provides for automation of design processes such as parametric design scanning, application of Taguchi concepts, optimization and probabilistic analysis. It (RDCS) depends on the automation of multi-disciplinary parametric math models that simulate the behavior of the object being designed. It is this requirement for automation that is addressed in the paper.

MSC is supporting RDCS by creating a powerful parameterization capability with the PATRAN pre and post-processor. The present result of this effort is a modification of PATRAN that permits the use of named variables to replace the usual fixed numerical values of the modeling parameters. These variable names are captured in the session file along with a default value. In addition, the values of these parameters different than the prescribed default can be provided in an external file that can be produced by another code such as the RDCS code referred to above. The goal of the PATRAN parameterization project is to make it possible for the user to use names and default values for variables (parameters) in every entry point on every form that can be accessed for modeling purposes. This goal has now been met for a large fraction of all the PATRAN forms. Similarly, we have provided for the definition and output of named response parameters such as maxima and minima of stress, strain, displacements and complex functions of results ( e.g.,Von Mises stresses or other measures of failure). These responses are directed to an output file for use by other codes such as the RDCS code referred to above.

Since a PATRAN session file can be re-run in a batch mode, including running the analysis preference, the parameterized version of this file can also be executed in batch mode. This makes it possible to simulate the response of an unlimited number of design variations and capture the responses as a function of the parametric variables and do so in batch mode without user intervention.

This paper will present a description of this new capability that can be added to PATRAN and show numerous examples of its use. Also, the coupling with RDCS will be described

PRACTICAL GLOBAL-LOCAL DESIGN OPTIMIZATION OF VEHICLE BODY-IN-WHITE STRUCTURES (Acrobat 1MB) 1996, 10 pgs.
Paramjot Bedi--Ford Motor Company
Metin Dede--Ford Motor Company
Greg Moore--The MacNeal-Schwendler Corporation

ABSTRACT: In structural analysis and optimization, local design features often will have a driving effect on global structural responses. Capturing the design possibilities in a manner that is useful to the optimizer may, however, result in physical designs that are unreasonable from a manufacturing point of view.

Vehicle body-in-white structures are a good illustration of this global-local phenomenon. Although the stiffnesses of the vehicle's joints strongly influence the global modes, the optimizer may have difficulty making design decisions owing to the detail inherent in the joints' description. Design variable linking is the obvious solution to the problem but it, in a sense, forces a constraint on the type of redesign the optimizer can perform.

In this paper, MSC/NASTRAN's design optimization capabilities, coupled with image superelements for the vehicle's joints are used to tune the global modes of a complex vehicle structure, while providing joint stiffness targets for subsequent local redesign.

SHAPE OPTIMIZATION OF A CAST TURBINE MANIFOLD (Acrobat 1.4MB) 1996, 13 pgs.
W.A. Holzmann--GenCorp Corporation
V.J. Wagner--The MacNeal-Schwendler Corporation

ABSTRACT: This paper discusses the application and lessons learned using the Shape Optimization capabilities in MSC/NASTRAN to analytically modify the existing design of a cast turbine manifold. Figure 1 shows a model of a typical cross section of the manifold. The objective of the analysis was to minimize weight while satisfying several load conditions as well as manufacturing and assembly constraints. Using MSC/PATRAN, a solid finite element wedge model of the cross section of the manifold was created. Basis vectors were generated with the analytical boundary method and used as shape design variables. The approach and results are discussed, as well as recommendations for future production use of the optimization capability.

SHAPE OPTIMIZATION USING SHAPE BASIS VECTORS (Acrobat 428KB) #4795, 9 pgs.
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 MacNeal-Schwendler 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.  

SHAPE PARAMETERIZATION AND OPTIMIZATION USING THE BOUNDARY SHAPES CONCEPT

(Acrobat 1.10MB) #1194, 18 pgs.

Hemant D Patel -- The MacNeal-Schwendler Corporation

ABSTRACT: The concept of boundary shapes for parameterization of design boundaries in shape optimization is introduced. In this concept the boundary definition of the finite element geometry is designed. In addition the requirement for use of shape basis vectors with low mesh distortion properties is ideally satisfied by interpolating domain point sensitivity by applying the boundary shapes or forms as enforced displacements and updating the shape basis vectors at each design cycle based on current geometry. This results in smooth mesh changes and minimizes the need for intermediate remeshing for small to moderate design changes. To support ease of use and provide flexibility in the prescription of boundary shapes the concept of auxiliary boundary models as been incorporated in MSC/NASTRAN as an integral part of the analysis model. The boundary shapes are generated with auxiliary boundary model analysis by exploiting available options in static analysis of applied loadings and multiple boundary conditions. Basic design examples demonstrating the power of the boundary shape approach are presented.

STRUCTURAL OPTIMIZATION WITH SOLUTION 2001 IN THE DESIGN PROCESS (Acrobat 2.57MB) #0494, 25 pgs.

Ingo Raasch -- BMW AG, Munich, Germany

ABSTRACT: The paper will explain the initiation and capabilities of S0L2001, a MSC/NASTRAN DMAP for structural optimization. The reminder will describe example problems, where 50L2001 has successfully used. Two examples show the achievements in concept design, followed by an example of a car body in white. Finally some shape optimization problems of engine components will be shown. A short outlook to the optimization capabilities of Version 68 will be given. In the conclusions it will be stressed that optimization is a very valuable (even in the meaning of $$) tool in the design process.

TOPOLOGY OPTIMIZATION USING MSC/NASTRAN (Acrobat 990KB) #1294,19 pgs.

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

C M. Lu -- The University of Texas at Arlington

R.J. Yang -- Ford Motor Company

ABSTRACT: Recently, Bendsoe and Kikuchi developed a homogenization method which can be applied to find the optimal topology of a continuum in a fixed domain. The homogenization approach is based on an artificial but physical micro-structure whose properties are homogenized. Alternatively, it has been demonstrated that the solution of the optimum material distribution problem can be considerably simplified by employing a density-dependent isotropic material without a specific physical micro-structure. In this paper, topology optimization for minimum compliance under static loading and for maximum eigenvalue using this approach has been implemented using MSC/NASTRAN. Optimal topology for a plate under in-plane and bending loads is presented. Optimal material distribution for a plate to maximize the first frequency is also presented.

THREE DIMENSIONAL SHAPE OPTIMIZATION WITH PROBABILISTIC CONSTRAINTS USING PARAMETRIC SESSION FILES(Acrobat 130 K) #0699, 15 pgs.
Jeffrey M. Brown--Air Force Research Laboratory, Wright Patterson AFB

ABSTRACT: Probabilistic analysis is rapidly developing into a desirable tool to improve design processes. Incorporating probabilistics with optimization of three dimensional components is a step towards improving many current deterministic design systems. This paper develops a general purpose method using MSC/PATRAN and MSC/NASTRAN for three dimensional shape optimization that incorporates probabilistic calculations. A parametric finite element model calculates design point responses and semi-analytic geometry sensitivities. The Advanced Mean Value First Order Second Moment Method is used for reliability calculations while sensitivities to the probability constraints are calculated analytically. Demonstration problems are conducted on a cantilever beam, turbine engine disk, and turbine engine blade.

USAGE OF OPTIMUM USAGE OF OPTIMIZATION TOOLS IN THE DESIGN PROCESS AT BMW (Acrobat 33 K) #0598, 10 pgs.
Ingo Raasch--BMW AG, Munich

ABSTRACT: The usage of optimization tools in structural mechanics has a long history at BMW, and it is very much connected with MSC/NASTRAN. Sizing is a standard procedure in body design with constraints on static and dynamic response. Shape optimization with MSC/NASTRAN was an initial success. However, at present it is performed most often with other programs owing to the ease-of-use and integration within CAD systems. The definition of shape vectors is still time consuming in both MSC/NASTRAN and other programs. Optimality-criteria methods such as MSC/CONSTRUCT SHAPE improved the ease-of-use, but with a sacrifice in the generality of the objective and constraints definitions. However, a combination of optimality criteria, mathematical optimization methods, and automatic shape generation has proven to be a more general and efficient approach.

Topology optimization is finally being used in the concept design phase. The definition of the design space can be accelerated tremendously by using the VOXEL technique of CAD systems. In this technique, a given volume is filled with cubes of equal size, in order to estimate the volume or detect component collisions. These cubes are directly used in the finite element design space definition.

Concept design relies heavily on beam/shell models with beam cross sections as design variables. However, given the short time frame for the concept design phase, optimization is still hampered by the lack of pre/processing tools for the design model definition and post processing of results, as well as the necessity for heavy computing resources.

USE OF DSA ANALYSIS RESULTS FOR RITZ FAST ANALYSIS OF PERTURBED MODELS
(Acrobat 228K) #0799, 11 pgs.
Dr. J.N Bricout and J.M. Leduigou--Centre National d'Etudes Spatiales

ABSTRACT: Finite element analysts often have to perform analysis of perturbed models in order to validate
the dimensioning through sensitivity analysis. This is also the case during Finite Element model
updating process or for stochastic dynamic analysis where we want to obtain a statistical
description of a solution, provided the statistical distributions of some design driving physical
parameters. These analyses often lead to a huge amount of calculations if the analysis is
performed using a loop inside a Finite Element software.
CNES has developed a fast dynamic reanalysis method based on a Ritz formulation using the
results of a Design Sensitivity Analysis performed with MSC/NASTRAN in order to introduce
the variation of some physical parameters in the analysis. This paper presents the basic
developments and implementation of this method.

USING OPTIMIZATION IN MSC/NASTRAN TO MINIMIZE RESPONSE TO A ROTATING IMBALANCE (Acrobat 1.11MB) #1695, 17 pgs.

Ted Rose--MacNeal-Schwendler 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.

USING DESIGN SENSITIVITY FOR STATISTICAL RESPONSE ANALYSIS (Acrobat 690KB) #2793, 19 pgs.

Ken Blakely -- The MacNeal-Schwendler Corporation

ABSTRACT: Statistical response analysis computes the statistical distribution of responses, given the distribution of design variable values. Variation in design variable values can result from manufacturing tolerances, and it can also be attributed to a level of uncertainty about the finite element input. Statistical distributions discussed herein are the standard deviation and variance.

Statistical response analysis can be accomplished in MSC/NASTRAN by using SOL 200 and DMAP alters in Version 67.5. This paper describes the theory, alters, and examples.

Optimization and Nonlinear

ADJOINT SENSITIVITY ANALYSIS IN MSC/NASTRAN, (Acrobat 322KB) #2897, 12pgs.
Erwin H. Johnson--The MSC.Software Corporation

ABSTRACT: The Adjoint Method for sensitivity analysis can sometimes produce sensitivities at a fraction of the computer resources required by the Direct Method. This paper presents the motivation, theory, implementation and selected results from installing this technique in Version 70 of MSC/NASTRAN. The application of the method to large scale design tasks is seen to "enables" the practical solution to design tasks driven by NVH (noise, vibration and harshness) considerations. Concluding comments summarize the results and discuss possible further developments.

BOSS-QUATRO AND MSC/PATRAN: A NEW GENERATION OF OPEN-ARCHITECTURE MULTIDISCIPLINARY OPTIMIZATION SOFTWARE, (Acrobat 215KB) #2497, 16pgs.
Patrick Morelle--SAMTECH s.a.John Klintworth--MSC Ltd.

ABSTRACT: Today's design in industry is in fact a combination of techniques whose primary goal is to understand the model's behavior. The next step is then to analyze the performance of the model using numerical simulation. Various sequences of trade-off, parametric analysis, sensitivity analysis, are then performed in order to formulate the final optimization problem properly. A basic feature of many design problems is their multi-disciplinary nature. As a result, more and more physical phenomena are being modeled and taken into account in the design problem formulation. This has required the use of more disparate and heterogeneous analysis and simulation software.

For those reasons, Samtech s.a. has developed an open design and optimization architecture: BOSS-QUATTRO. This new software has been applied with success in multi-disciplinary (e.g. fluid/structure) analysis and optimization as well as in parametric studies and Monte Carlo analysis. In particular, a very powerful system has been built by linking the BOSS-QUATTRO system to the MSC/PATRAN environment, providing new capabilities for multi-disciplinary optimization by taking advantage of MSC/PATRAN's existing links to multiple analysis codes.

The BOSS-QUATTRO environment is designed as an application manager: it includes existing analysis chains in arbitrary loops and sequences, and provides new capabilities like parametric studies, Monte-Carlo simulation, sensitivity analysis or optimisation. BOSS-QUATTRO is linked to application programs in a standard way through drivers. This open architecture means that the system is able to exchange information with present and future commercial products as well as with in-house codes. For example, drivers exist for popular commercial software MSC/PATRAN, MSC/NASTRAN, SAMCEF, PRO-ENGINEER and CATIA. In addition, any application using a text file for input and output can be linked through a flexible "neutral" driver.

Within the present paper, two applications developed in the context of a BRITE/EURAM project (MODSYSS, CT94-0590) are presented. The first takes advantage of links between MSC/PATRAN and several analysis codes to perform multidisciplinary analyses on a component. The second links a parametric CAD system to an analysis code to allow full three-dimensional shape optimization. These examples demonstrate the ability to link together disparate commercial software systems to perform effective design optimization.

DETERMINISTIC DESIGN, RELIABILITY-BASED DESIGN AND ROBUST DESIGN, (Acrobat 78KB) #2597, 11pgs.
Wei Wang and Justin (Y.T.) Wu--Southwest Research Institute
Robert V. Lust--General Motors Research & Development Center

ABSTRACT: Due to the inherent uncertainties or variabilities in loads, materials and manufacturing quality, variabilities are unavoidable in structural responses. To ensure the reliability of a structure, these uncertainties or variabilities must be considered during structural design. Through a simple cantilever box beam example, the concepts and practices of three design methodologies: deterministic design, reliability-based design, and robust design, are examined in this paper. Particular attention is given to the meaning of robust design and its definition in the context of reliability-based design. Several robustness criteria are studied and proposed in an attempt to search for a proper objective function in a reliability-based design framework. The stress analysis is carried out using both MSC/NASTRAN and an analytical formula.

NEXT GENERATION STRUCTURAL OPTIMIZATION TODAY, (Acrobat 1.1MB) #2697, 14pgs., color
Craig S. Collier, P.E., Mark Pickenheim, and Phil W. Yarrington--Collier Research & Development Corporation

ABSTRACT: Characteristics of a next generation software product are presented for a coupled MSC/NASTRAN FEA and structural optimization system. These characteristics include methods for automated structural analysis and optimization such as a statistical approach for determining 'design-to' loads and analytical/numerical 'zooming' for detailed global to local response. Software characteristics include a collection of standard panel and beam concepts, and an object oriented approach to strength and stability failure analyses. These features are provided in a multiproject, multiuser, secure database environment where the Internet standard Virtual Reality Modeling Language (VRML) is used for visual interpretation of results.

NONLINEAR STRENGTH AND STABILITY ANALYSIS OF A LANDING GEAR COMPONENT, (Acrobat 1.17MB) #2797, 15pgs.
Andrew Mera--The Boeing Company

p-elements

THE APPLICATION OF INTERFACE ELEMENTS TO DISSIMILAR MESHES IN GLOBAL/LOCAL ANALYSIS (Acrobat 704KB) 1996, 16 pgs.
John E. Schiermeier--The MacNeal-Schwendler Corporation
Jerrold M. Housner--NASA Langley Research Center
Jonathan B. Ransom--NASA Langley Research Center
Mohammad A. Aminpour--Applied Research Associates, Inc.
W. Jefferson Stroud--NASA Langley Research Center

ABSTRACT: When performing global/local analysis, the issue of connecting dissimilar meshes often arises, especially when refinement is performed. One method of connecting these dissimilar meshes is to use interface elements. In MSC/NASTRAN Version 69, interface elements have been implemented for the p–shell elements. This paper will discuss the elements and present examples.

PCL

CFD DATA TRANSFER TO STRUCTURAL ANALYSIS (Acrobat 2.9MB) 1996, 19 pgs.
W. Scott Taylor--Sverdrup Technology, Inc.

ABSTRACT: This paper describes the development of a procedure to transfer computational fluid dynamics (CFD) results entities to structural analysis. This procedure is a subset of a larger effort at NASA/Marshall involving interdisciplinary data transfer between a number of traditionally somewhat isolated disciplines. A brief discussion of that effort will also be included. The specifics of translating CFD structured grid results entities in Plot-3D binary format to a dissimilar finite element mesh for load re-interpolation permitting subsequent structural analysis is demonstrated. MSC/PATRAN Command Language was used to automate various features of this capability. The procedure resulted in a major productivity enhancement due to the fact that previously, there was no convenient method to get vehicle or other complex geometry CFD results on to structural analysis models. The procedure is being used routinely for similar interdisciplinary data transfers.

CUSTOMIZATION OF WING ANALYSIS (Acrobat 33K) #3698, 7 pgs.
Wang Linjiang--Nanjing University of Aeronautics and Astronautics, PR China
Matthias Haupt--TU Braunschweig, Germany

ABSTRACT: This article is concerned about the customization of creating a FEM model of a wing structure. The row and column method is used to number the structure parts(ribs, spars, skins), then the property parameters of all parts can be respectively inputted using the spreadsheet in which data can be inputted easily and correctly. A PCL(MSC/PATRAN Command Language under MSC/PATRAN 6.0) code is developed for the customization from constructing airfoil curves to creating the entire wing FEM model. A zigzag wing is demonstrated to verify the code. At last a VFW614 wing is analyzed from creating airfoil curves to the show of stresses that are calculated using MSC/NASTRAN 68. The results shows that this customization is very effective and efficient, it makes such a difficult work of creating a wing FEN model become much easier. This method can likewise be used to fuselage and other complicated structures.

ENVELOPING RESULTS OF MULTIPLE LOAD CASES (Acrobat 65K) #3498, 10 pgs.
Victor Genberg--Eastman Kodak Company
Justin Vianese--The MacNeal-Schwendler Corporation

ABSTRACT: Many structures such as those used in the aerospace and the automotive industry are subjected to multiple load conditions. Software has been developed to scale, combine, and sort stresses, forces, and displacements from a few unit load cases. The procedure saves creating and running many load cases, requires much less plotting, and prevents errors of omission. A launch load event of 128 combinations can be analyzed from 7 unit load cases combined into a single plot. This technology is now available as MSC/PATRAN shareware.

AN INTEGRATED COMPUTER AIDED ENGINEERING TOOL FOR AIRCRAFT TRANSPARENCY DESIGN ANALYTICAL DESIGN PACKAGE--ADP (Acrobat 4.2MB) 1996, 25 pgs.
J.E. Wuerer--The MacNeal-Schwendler Corporation
M. Gran--Wright-Patterson AFB
T.W. Held--University of Dayton Research Institute

ABSTRACT: The Analytical Design Package (ADP) has been developed as a part of the Air Force Frameless Transparency Program. ADP is an integrated design tool consisting of existing analysis codes and Computer Aided Engineering (CAE) software. The objective of the ADP is to develop and confirm an integrated design methodology for frameless transparencies, related aircraft interfaces, and their corresponding tooling. The application of this methodology is intended to generate a high confidence for achieving a qualified part prior to mold fabrication.

ADP is a customized integration of analysis codes, CAE software and material information databases. The primary CAE integration tool for the ADP is MSC/PATRAN, a commercial-off-the- shelf (COTS) software tool. The open architecture of MSC/PATRAN allows customized installations with different application modules for specific site requirements. Integration of material databases allows the engineer to select a material and those material properties are automatically input into the relevant analysis code. The ADP materials database supports two independent schemas: (1) CAE Design Properties and (2) Processing and Test Data.

The design of the ADP places major emphasis on the seamless integration of CAE and analysis modules with a single intuitive graphical interface. This tool has been designed to serve and be used by an entire project team, i.e., analysts, designers, materials experts and managers. The final version of the software was delivered to the Air Force in June 1995. The Analytical