MSC 1996 World Users' Conference Proceedings

The conference proceedings for the 1996 World Users' Conference are now available on-line in Adobe Acrobat PDF format. In addition, the papers that won the prize for best example of the conference theme from both 1995 and 1996 are available in HTML format. The papers have been categorized by topic.

Categories

• Aircraft
• Automotive
• Civil
• Composites
• Design/Manufacturing Methods
• DMAP
• Electronics
• Fatigue Analysis
• General Stress Analysis
• Optimization
• p-elements
• PCL
• Spacecraft
• Test/Analysis Correlation
• Thermal Analysis

Aircraft

ADVANCED COMPOSITES REPAIR ANALYSIS TOOL (ACRAT) (Acrobat 64KB)

Thomas E. Mack--The MSC.Software Corporation

James Y. Song--USAF Advanced Composites Program

ABSTRACT: The Advanced Composites Repair Analysis Tool (ACRAT) has been under development for the USAF Advanced Composites Program Office under an Ogden ALC Design Engineering Program (DEP) Contractual Engineering Task (CET) Order. ACRAT is an integrated prototype software system consisting of commercial-off-the-shelf (COTS) and public domain CAE simulation codes and customized databases. The objective has been to develop Beta versions of this computer aided composite repair design and assessment engineering tool following the provisions and procedures of the ASTM Standard E 1340-90 (Reference 1). The standard guide produces working models early in the development cycle, which allows users and developers to learn functional requirements and appropriate system design details by actually interacting with a series of prototypes. Two Beta versions, of a planned six Beta cycle development effort (three-year program), have been completed to-date. The proposed ACRAT solution will reduce the Air Force's dependence on airframe manufactures for engineering assistance, reduce component scrap rates, reduce aircraft down-time while repairs are being designed or because spare parts are not available, and reduce the manpower spent removing and reinstalling aircraft parts that could have been repaired on-aircraft.

ACRAT's software system design emphasis has been focused on standardized methods of electronic data modeling and exchange; a UNIX-less process management environment which insures geometric configuration management and material release control; integration of COTS and/or public domain software wherever possible to reduce the cost of development while maximizing system functionality and reducing future costs of ownership (upgrading/porting supportability); and a single user friendly graphical user interface (GUI) capable of supporting a wide range of perspective users (field technician or expert CAE/composites engineer).

Four (4) customized database schemas (M&P, Aircraft Design, Composite Repair, Component Test) were designed and sufficiently populated to evaluate each data model's ability to meet specific ACRAT system requirements. These prototype databases, coupled with the ACRAT Executive Control System (ECS) database, represent the foundation upon which the fully self contained ACRAT software system has been built.

 

CALCULATION WITHIN MSC.Nastran OF THE FORCES TRANSMITTED BY MULTIPOINT CONSTRAINTS (MPC) AND THE FORCES GENERATED IN SUPPORT CONSTRAINTS (Acrobat 128KB)

E. de la Fuente--Instituto Nacional de Técnica Aeroespacial (INTA)

J. San Millán--Instituto Nacional de Técnica Aeroespacial (INTA)

ABSTRACT: This paper describes a procedure that permits the calculation of the forces generated in MPC and SUPORT constraints, in STATIC and DYNAMIC (Frequency response) load cases. These constraints are extensively used in MSC.Nastran. In the paper the theoretical bases of the procedure are given, as well as DMAP sequences that allow to calculate these forces, and demonstration examples.

 

COMBINING ACCELERATION AND DISPLACEMENT DEPENDENT MODAL FREQUENCY RESPONSES USING AN MSC.Nastran DMAP ALTER (Acrobat 96KB)

Alan R. Barnett--Analex Corporation

Timothy W. Widrick--Analex Corporation

Damian R. Ludwiczak--NASA Lewis Research Center

ABSTRACT: Solving for dynamic responses of free-free launch vehicle/spacecraft systems acted upon by buffeting winds is commonly performed throughout the aerospace industry. Due to the unpredictable nature of this wind loading event, these problems are typically solved using frequency response random analysis techniques. To generate dynamic responses for spacecraft with statically-indeterminate interfaces, spacecraft contractors prefer to develop models which have response transformation matrices developed for mode acceleration data recovery. This method transforms spacecraft boundary accelerations and displacements into internal responses. Unfortunately, standard MSC.Nastran modal frequency response solution sequences cannot be used to combine acceleration- and displacement-dependent responses required for spacecraft mode acceleration data recovery. External user-written computer codes can be used with MSC.Nastran output to perform such combinations, but these methods can be labor and computer resource intensive. Taking advantage of the analytical and computer resource efficiencies inherent within MSC.Nastran, a DMAP Alter has been developed to combine acceleration- and displacement-dependent modal frequency responses for performing spacecraft mode acceleration data recovery. The Alter has been used successfully to efficiently solve a common aerospace buffeting wind analysis.

 

EMB-145 NOSE LANDING GEAR DOOR STRESS ANALYSIS (Acrobat 1.6MB)

Francisco K. Arakaki--EMBRAER-Empresa Brasileira de Aeronáutica

Filipe K. Honda--EMBRAER-Empresa Brasileira de Aeronáutica

Maria Luci P. Salomão--EMBRAER-Empresa Brasileira de Aeronáutica

ABSTRACT: In the present report the structural analysis of EMBRAER's EMB-145 Aircraft Nose Landing Gear Door (N.L.G.D.) is shown.

The EMB-145 Nose Landing Gear Door is attached to the aircraft fuselage through three hinges which are driven by a hydraulic actuator attached to the central hinge. The EMB-145 N.L.G.D. structure, is made of two solid prepreg carbon/epoxy laminated skins, cold bonded and fastened. Carbon/epoxy tape is used in order to avoid panel buckling and to increase the required stiffness of the Aerodynamic Smoothness Requirements for EMB-145. The hinges are machined from aluminum alloy, attached to the structure by titanium alloy bolts.

The EMB-145 Nose Landing Gear Door is designed to resist the critical aerodynamical loading in normal condition and in case one of the hinges fails.

The EMB-145 Nose Landing Gear Door structural analysis including finite element data, boundary conditions and acting loading are presented in this report. The present output results in MSC.Nastran allow one to obtain the most critical condition among all subcases very quickly, when post-processed.

 

EVALUATION OF AN ANALYTICAL DESIGN TOOL FOR BALLISTIC DYNAMICS SIMULATION (Acrobat 672KB)

Ashish K. Sareen--Bell Helicopter Textron, Inc.

Michael R. Smith--Bell Helicopter Textron, Inc.

ABSTRACT: Usefulness of ballistic dynamics simulations as a design tool in assessing ballistic tolerance and as an aid in pretest guidance is studied. Accurate simulations of hydraulic ram, including failure mode prediction, can be useful in enhancing survivability and in guiding pretest specimen setup to ensure projectile strike and exit at critical locations, thereby minimizing the cost of expensive development tests. To understand the potential of ballistic simulation as a design tool, MSC/DYTRAN code has been evaluated at Bell Helicopter Textron, Inc. by conducting simulations using projectiles of different sizes to impact and penetrate a generic fluid-filled tank and a composite wing structure containing fuel cells. Projectile trajectory, fluid pressures in the fuel tank, and wing structural response from the analysis are compared with the measured data. The physics of the phenomenon appears to be accurately simulated, indicating that MSC/DYTRAN could be a useful design tool for enhancing ballistic tolerance.

 

A MSC/DYTRAN SIMULATION OF THE LYNX HELICOPTER MAIN LIFTFRAME COLLAPSE (Acrobat 480KB)

Marcio J. Cavalcanti--Brazilian Navy

Rade Vignjevic--Cranfield University

ABSTRACT: MSC/DYTRAN, an explicit nonlinear finite element code, was used to determine the collapse characteristics of the Lynx helicopter main liftframe, for the vertical crash case. The liftframe was modelled by the Belytschko-Tsay four node shell elements. The analysis of the influence of the collapse velocity on the component structural failure modes and a sensitivity analysis of the material failure criteria were performed. The increase in crashing velocity from 4 to 8 m/s changed the mode of structural failure from torsional buckling, to bending/axial failure. The material failure criteria, however, did not significantly affect the structure collapse mechanism nor the force vs. displacement results. The MSC/DYTRAN simulation results showed good agreement with the full scale test data.

 

MSC.Nastran FLUTTER ANALYSES OF T-TAILS INCLUDING HORIZONTAL STABILIZER STATIC LIFT EFFECTS AND T-TAIL TRANSONIC DIP (Acrobat 768KB)

Emil Suciu--Gulfstream Aerospace Corporation

ABSTRACT: An existing method for calculating the effect of static lift of the horizontal stabilizer in yaw and the effect of static deflection of the horizontal stabilizer on T-tail flutter is appended to the MSC.Nastran flutter solution. The application of the method to a T-tail of interest shows the expected trends. A strip theory correction scheme is proposed to permit separation and factoring of C L a and C l b on the horizontal stabilizer by different factors. A refinement of the T-tail transonic dip calculated with classical methods is obtainable this way.

 

MSC.Patran AS A PART OF A TOOL IN THE FIELD OF STATIC AND DYNAMIC AEROELASTICITY (Acrobat 1MB)

Jari Hyvärinen--Anker-Zemer Engineering AB

Per Kjellgren--Anker-Zemer Engineering AB

ABSTRACT: This paper uses two measures for stability when studying aeroelastic behaviour in problems which require Non-linear fluid mechanics modelling for the solution. One measure is defined for static stability and the other for dynamic stability. The simulation performed on the fluid-structure interaction of a 2D ellipse in a sub critical Reynolds number flow field is shown in this paper.

 

PREDICTION OF BREAK-OUT PATTERNS FOR AIRCRAFT CANOPIES FRAGILIZED MECHANICALLY OR WITH DETONATING CORD (Acrobat 160KB)

Rocky Richard Arnold--Leapfrog Technologies, Incorporated

Patrick S. Collins--Leapfrog Technologies, Incorporated

ABSTRACT: This paper presents a methodology for predicting the fragilization behavior of aircraft canopies subjected to either mechanical loading or explosive pressures, or both. Fragilization refers to the process whereby an intrinsically strong and tough polymer canopy material (such as stretched-acrylic or polycarbonate) is cracked, damaged or otherwise weakened in such a manner as to destroy its resistance to mechanical loading created by an egressing pilot or crewmember. The approach adopted uses MSC.Nastran as the foundation of a computational procedure that uses fracture mechanics principles to predict crack generation, growth, and propagation (including branching). The computational procedure, called PACE, for Program for Automatic Crack Extension, automatically reconstructs finite element grids according to the growth of crack(s). MSC.Nastran is used to predict the dynamic state of stress at, and around a crack tip(s), and PACE includes fracture mechanics modules which use the existing stress state to predict propensity for further cracking. The entire process is automated allowing users to perform a complete analysis without concern for the need for new finite element meshes. At conclusion, the trace of cracks provides the break-out pattern. Ideally, the break-out pattern generates small pieces of material which are estimated to not be harmful to the pilot and crewmembers. This paper reviews the progress of work accomplished to date.

 

SIMULATION OF A HELICOPTER COCKPIT AIR BAG SYSTEM WITH MSC/DYTRAN (Acrobat 416KB)

David Furey--Simula Government Products, Inc

Arjaan Buijk--MSC.Software Corporation

Lindley W. Bark--Simula Government Products

ABSTRACT: In the development of inflatable restraints for automobiles, engineers have become increasingly reliant on analytical methods to support design efforts. Current efforts to develop inflatable restraints for helicopter cockpits are also relying on analytical methods to gain efficiency in the design process. Applying inflatable restraint technologies to a helicopter cockpit is often a retrofit system integration, since typical airframe service lives are on the order of 30 years and new aircraft models remain rare. Thus, since the placement of air bag components is usually not optimum, the trajectory of the deploying air bag must be precisely controlled. This is accomplished with innovative folding schemes and prescribed bag-structure and bag-occupant contacts that will guide the air bag to its desired position. In the majority of helicopter applications, adequate air bag load-bearing surfaces do not exist. This drives the air bag shapes to be fairly complex, compared to an automotive air bag. To meet the challenges of this modeling effort, the MSC/DYTRAN code was selected and modeling techniques have been developed to realistically simulate single- and multiple-bag helicopter air bag systems.

 

TURBINE ROTOR BURST CONTAINMENT ANALYSIS USING MSC/DYTRAN AN ANALYTICAL APPROACH TO PREDICTING PRIMARY CONTAINMENT (Acrobat 768KB)

Kelvin Y. Ng--Hamilton Standard

ABSTRACT: With the common use of turbo-fluid machinery in the aerospace industry, rotor burst containment is an important design requirement. More demanding weight reduction goals are pushing containment structures to the brink of containment efficiency. Design engineers at Hamilton Standard have been reliant on design similarities and empirical data, to predict containability. However, limitations in the current methodology make detailed predictions difficult, especially if the geometry is not based on a previous design. In some cases, the limitations in the empirical method can lead to many costly tests. With the use of MSC/DYTRAN, and the help of the MacNeal-Schwendler Corp., Hamilton Standard has been developing an analytical method to predict rotor burst containment. Preliminary case studies have shown that MSC/DYTRAN can handle the physics involved with turbine rotor containment. Using the analytical methodology, structural damage and material response are characterized from the physics. Therefore, the prediction is independent of similar designs.

 

A VULNERABILITY MAP OF A COMMERCIAL AIRCRAFT (Acrobat 1.5MB)

Y. I. Moon--Wright Patterson AFB

G. Bharatram--Wright Patterson AFB

Capt. S. A. Schimmels--Wright Patterson AFB

Dr. V. B. Venkayya--Wright Patterson AFB

ABSTRACT: A method of developing a vulnerability map of a commercial aircraft is presented using MSC/DYTRAN and MSC.Nastran. The intent of the map is to establish the vulnerability of every point in the cargo hold where a bomb can explode. One might interpret each point in the cargo bay as having four dimensions. Three are spatial coordinates and the fourth is the maximum size of the bomb the structure can withstand without catastrophic failure. The vulnerability of the aircraft is examined from two distinct failure scenarios. The first is the response immediately after the bomb explosion. The second is the subsequent flight to the nearest airport for safe landing.

The immediate response analysis is determined with MSC/DYTRAN and the post explosion analysis is made by MSC.Nastran. A complete vulnerability map requires many failure scenarios and a large number of MSC/DYTRAN and MSC.Nastran analyses. Six points in the cargo hold were critically examined to demonstrate the concept.

Automotive

ANALYTICAL PREDICTION OF LEAF SPRING BUSHING LOADS USING MSC.Nastran AND MDI/ADAMS (Acrobat 2MB)

Shahriar Tavakkoli--Ford Motor Company

Farhang Aslani--Ford Motor Company

David S. Rohweder--Ford Motor Company

Satyendra Savanur--Automated Analysis Corporation

ABSTRACT: Analytical loads in leaf spring bushing can be used to perform finite element analysis on brackets that connect the leaf spring to a truck frame. Two models of leaf springs in MSC.Nastran and MDI/ADAMS were created to compare the bushing loads predicted by each model. The geometric nonlinear capability of MSC.Nastran (SOL 106) was used to predict the bushing loads in MSC.Nastran model. The quasi-static simulation capability of MDI/ADAMS was used to predict the bushing loads in MDI/ADAMS model. The analyses simulated the standard jounce and roll tests at The University of Michigan Transportation Research Institute (UMTRI). An accurate prediction of loads in MSC.Nastran model provides the benefit of integration that allows us to include the leaf spring model in a full vehicle model to simulate full vehicle lab tests as well as proving ground durability events. Good correlation was obtained between the two models in jounce condition. More effort is underway to establish satisfactory correlation for roll condition.

 

BACK LOAD CALCULATION: A METHOD OF MEASURING COMPONENT LOADS WITHOUT LOAD CELLS (Acrobat 1.6MB)

R. Ilankamban--Ford Motor Company

P. R. Perumalswami--Ford Motor Company

A. J. Page--Ford Motor Company

ABSTRACT: In general, FEA is used to find stress/strain in a structure once the loading on the structure is known. In this paper, a method to calculate load from known strain using FEA is presented. Compared to the conventional load measurement method, the proposed method produces more accurate loads with less cost and time. In the conventional method, parts of the component in critical load paths are removed and specially designed load cells are welded in their place. This changes the stiffness and mass of the component, altering the load environment. Resulting load path change in the system could become a major source of discrepancy between the measured load and the load in the actual system. Further, due to space limitation, it may not be possible to instrument for simultaneous measurement of all the loads on the component. These limitations are overcome in the proposed measurement technique by using the whole component, unaltered, as its own load cell. Strains at specific strategic locations on the component are measured and load is back calculated from these strain readings. In this method, except to place strain gages on the component surface, no modification is done to the component. To identify the proper locations for strain gage measurements and to back calculate the load from strain, a software developed in-house, called BLC (Back Load Calculator), is used in conjunction with Finite Element Analysis.

This technique is applied to an automobile suspension component. Results show excellent correlation of back calculated load with the actual load. Also a conventionally instrumented (with designed load cell) component is used for comparison. The proposed method consistently showed considerable improvement over the conventional method.

 

THE CONTRIBUTION OF PASSENGER SAFETY MEASURES TO THE STRUCTURAL PERFORMANCE IN SPORTS RACING CARS (Acrobat 1.1MB)

Mark Roots--Cranfield University

Jason Brown--Cranfield University

Neil Anderson--Cranfield University

Thomas Wanke--Cranfield University

Marco Gadola--Cranfield University

ABSTRACT: This report deals with the modelling of an Automotive Chassis using MSC.Nastran. The torsion stiffeness of the chassis was able to be increased by 500% over the initial configuration by judicious design.

In an effort to allocate more science to the problem of roll cage design it was proposed that nonlinear finite element analysis using MSC.Nastran would give a good indication of the true load carrying capacity and deflection under load of the roll cage/frame. The analysis carried out was verified by the test programmme on a full scale chassis. This analysis gave results within an accepatable 10% of the test results despite the simplifying assumptions.

This application of MSC.Nastran is new as most small automotive manufacturers rely on past experience for their development. This works well for evolutionary design but not for major structural modifications as were carried out. This report highlights the value of MSC.Nastran in this application.

 

FINITE ELEMENT ANALYSIS OF AUTOMOBILE CRASH SENSORS FOR AIRBAG SYSTEMS (Acrobat 288KB)

Christopher A. Leger--Breed Technologies, Inc

Claude A. Bryant--Breed Technologies, Inc

ABSTRACT: Automobile spring bias crash sensor design time can be significantly reduced by using finite element analysis as a predictive engineering tool. The sensors consist of a ball and springs cased in a plastic housing. Two important factors in the design of crash sensors are the force-displacement response of the sensor and stresses in the sensor springs. In the past, sensors were designed by building and testing prototype hardware until the force-displacement requirements were met. Prototype springs need to be designed well below the elastic limit of the material. Using finite element analysis, sensors can be designed to meet force-displacement requirements with acceptable stress levels. The analysis procedure discussed in this paper has demonstrated the ability to eliminate months of prototyping effort.

MSC/ABAQUS has been used to analyze and design airbag crash sensors. The analysis was geometrically nonlinear due to the large deflections of the springs and the contact between the ball and springs. Bezier 3-D rigid surface elements along with rigid surface interface (IRS) elements were used to model ball-to-spring contact. Slideline elements were used with parallel slideline interface (ISL) elements for spring-to-spring contact. Finite element analysis results for the force-displacement response of the sensor were in excellent agreement with experimental results.

 

NONLINEAR DYNAMICS OF BRAKE SQUEAL (Acrobat 128KB)

M. L. Chargin--NASA Ames Research Center

L. W. Dunne--CDH GmbH

D. N. Herting--CDH GmbH

ABSTRACT: An efficient procedure for the analysis of brake squeal using MSC.Nastran models is described. A unique nonlinear method accounts for both superelement modes and surface friction data. The motions at the pad/rotor interface are described by small velocities and pressures relative to the steady-state condition. Both Transient Analysis and Complex Eigenvalues are provided analysis of brake systems.

 

TRUCK INTERIOR NOISE PREDICTION BY FEM AND BEM (Acrobat 3.8MB)

Amiya R. Mohanty--Ford Motor Company

Barry D. St. Pierre--Ford Motor Company

P. Suruli-Narayanasami--Ford Motor Company

ABSTRACT: A Computer Aided Engineering (CAE) method is developed for noise prediction in a truck cab interior. The finite element (FE) and the boundary element method (BEM) are used to characterize the acoustic field of a truck cab interior in terms of its natural frequencies and mode shapes. Structural vibration responses of the cab are computed for excitations at the cab mounts in a frequency range from 50 to 250 Hz. Then interior noise levels at the driver's right ear location are computed using the boundary element method for such excitations at the cab mounts.

 

Civil

IMPACT ANALYSIS OF A CONCRETE STORAGE CONTAINER (Acrobat 6MB)

H.P. Lee--Ontario Hydro

ABSTRACT: A concrete container with impact limiters is analyzed for a 9m free drop to a rigid ground. The complete finite element model is built using MSC.Patran. Analysis is then carried out using DYNA3D. Results are again completely processed using MSC.Patran in terms of time history plots of energy, momentum and contact force; deformation of the container during impact; and stress/strain distribution in the container at different times.

 

NON-LINEAR FINITE ELEMENT ANALYSIS OF REINFORCED CONCRETE MEMBERS USING MSC.Nastran (Acrobat 64KB)

Sreekanta Das--University of Wollongong

Dr. Muhammad N.S. Hadi--University of Wollongong

ABSTRACT: Non-linear finite element (FE) analysis of reinforced concrete (RC) members like beams, slabs etc. using the majority of available commercial finite element software poses many numerical difficulties. Major difficulty is faced because of strain-softening behavior of concrete once it is yielded. These commercial finite element software of FE analysis remain totally inadequate in handling strain-softening behavior of concrete. This is because these software offer only the traditional non-linear solution techniques like Newton-Raphson (N-R), modified Newton-Raphson (mN-R) methods etc. which can not handle the non-linear post-yielding analyses of members made of materials like concrete, soil, rock etc. which exhibit strain-softening behaviors after their yielding. MSC.Nastran, however, offers many advanced solution techniques like Crisfield's arc-length (CA) method, Riks' arc-length (RA) method, and modified Riks' arc-length (mRA) method. These methods can handle the strain softening behavior adequately.

This paper presents the uses of MSC.Nastran and advantages of using this software for non-linear analyses of RC members. Brief discussion on modeling procedures and discussion of results of three RC shallow beams are also presented to illustrate the degree of accuracy in results which could be achieved from non-linear post-yielding analyses of R.C. members by using MSC.Nastran.

 

PENETRATION ANALYSES DUE TO PIPEWHIP LOADS (Acrobat 448K)

H.P. Lee--Ontario Hydro

ABSTRACT: A steel penetration embedded inside a concrete containment structure is analyzed using MSC.Nastran. Four separate loads of axial, shear, moment and torsion as generated by a postulated pipewhip accident are applied at the end flange of the penetration. For each load case, stress distribution across and along the penetration as well as the interface between the penetration and the surrounding concrete are described in details.

 

Composites

COMPOSITE BLADE DESIGN FOR BIRDSTRIKES USING MSC/DYTRAN: AN AUTOMATED APPROACH TO ENABLE RAPID SCREENING OF COMPOSITE LAY-UPS (Acrobat 2.6MB)

John C. Lambert--Hamilton Standard, a Division of United Technologies

ABSTRACT: As the aerospace industry continues to strive for lighter weight, more cost effective solutions, the emphasis on composite fan blades has become intense. Composite blades must be designed to meet tough, FAA, foreign object damage requirements. In order to meet these goals, the design engineer must intelligently manage the variation of large numbers of lay-up parameters. This requires an analysis system that couples the Aerodynamic, Design and Structural disciplines and proves rapid evaluation of composite lay-up changes. Hamilton Standard and the MSC.Software Corporation have developed a shell element based, composite blade analysis system, to evaluate composite blade bird strikes. Using this rule based, MSC/DYTRAN analysis system, Hamilton Standard can provide same day blade impact screening, starting from an aerodynamic blade definition and ending with stresses & strains for a fully prestressed plate model.

 

DESIGNING OPTIMUM FIBRE LAYOUT FOR COMPOSITE SANDWICH PANELS (Acrobat 32KB)

W Boruszewski--Instituto Nacional de Pesquisas Espaciais

M Kataoka-Filho--Instituto Nacional de Pesquisas Espaciais

ABSTRACT: The design of composite sandwich panels in terms of face sheet fibre orientation layout is examined searching for a maximum stiffness with total mass constant. Two basic layouts are considered: the first using constant fibre orientation and the second having a different fibre angle for each panel quarter. Specimens are tested showing good agreement with the first natural frequencies calculated for their finite element models. Taking fibre angles as design variables both layouts are maximized for the first eigenvalue. Two subsequent partitions are modeled with important stiffness increases achieved.

 

AN INTEGRATED FEA AND DESIGN OPTIMIZATION SYSTEM FOR COMPOSITE STRUCTURES (Acrobat 704K)

Craig S. Collier--Collier Research & Development Corporation

ABSTRACT: The benefits of a software program which couples with the MSC.Nastran™ FEA package is presented. The software, called HyperSizer™, performs panel and beam structural sizing optimization with metallic and composite materials. Applications in the aerospace and transportation industries are presented. The aerospace application, and X-34x experimental vehicle, emphasizes capabilities and accuracy required for a high speed flight, thermomechanical environment. The transportation application emphasizes practical and inexpensive capabilities suitable for a cost driven, manufacturing oriented environment.

 

A SIMPLE MODEL TO ANALYZE THE THROUGH-WIDTH DELAMINATIONS (Acrobat 96KB)

Francisco Kioshi Arakaki--EMBRAER-Empresa Brasileira de Aeronáutica

Sérgio Frascino Müller de Almeida--ITA-Instituto Tecnológico de Aeronáutica

ABSTRACT: In the most of the studies, if not all, the composite stress analysis is made considering the unidirectional graphite/epoxy prepreg (tape). However, in the practical design, in many situations it is interesting to use the woven graphite/epoxy prepreg (cloth). Therefore, this report outlines the preliminary results in through-width delamination specimens made of graphite/epoxy prepreg tape with graphite/epoxy prepreg cloth.

Initially, a simple model based on the results presented in ref. [ 1 ] was made, analyzed and compared with MSC.Nastran, ref. [ 2 ]. This model considered a two-dimensional geometrically nonlinear finite element. The results obtained by MSC.Nastran in finite element model with 153 nodes and 128 four-node isoparametric elements were in very good accordance when compared to classical theory, presented in ref. [ 1 ]. The model contained four sub-structures with a total of 813 nodes and 740 four-node isoparametric elements.

The next step was to analyse through-width delaminations in specimen made of graphite/epoxy tape with graphite/epoxy cloth. This specimen not only contains two types of graphite/epoxy, tape and cloth, but also presents a non-symmetrical laminated. The results obtained by MSC.Nastran were compared with the classical theory and were found to be in very good accordance. This report shows how these results were obtained.

 

Design/Manufacturing Methods

1995 World Users' Conference Winner: Best Exemplifies Conference Theme of Improving Engineering Productivity Through Analysis

Combining MSC.Nastran, Sensitivity Methods, and Virtual Reality to Facilitate Interactive Design (HTML)

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

 

1996 World Users' Conference Winner: Best Exemplifies Conference Theme of Applications of Predictive Engineering

Modeling of Die Surface Features on Integrated Circuits to Improve Device Reliability

HTML Version
Adobe Acrobat Version (1.9MB)

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

 

AN INTRODUCTION TO TOLERANCE ANALYSIS OF FLEXIBLE ASSEMBLIES (Acrobat 256K)

K. G. Merkley--Brigham Young University

K. W. Chase--Brigham Young University

E. Perry--Brigham Young University

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

 

DMAP

A DMAP ALTER TO ALLOW AMPLITUDE-DEPENDENT MODAL DAMPING IN A TRANSIENT SOLUTION (Acrobat 224KB)

Ted Rose--The MSC.Software Corporation

Martin McNamee--The MSC.Software Corporation

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

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

 

MSC.Nastran BASED COMPONENT MODE SYNTHESIS ANALYSIS WITHOUT THE USE OF DMAPS (Acrobat 64KB)

Tarun Ghosh--Rockwell International Corporation

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

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

 

Electronics

STRUCTURAL ANALYSIS OF KA-BAND GIMBALED ANTENNAS FOR A COMMUNICATIONS SATELLITE SYSTEM (Acrobat 192KB)

Hong Su--COM DEV Ltd.

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

 

3D MSC/EMAS SIMULATION OF A THREE PHASE POWER TRANSFORMER BY MEANS OF ANISOTROPIC MATERIAL PROPERTIES (Acrobat 544KB)

Dr. E. Schmidt--University of Technology, Vienna

S. Ojak--University of Technology, Vienna

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

 

Fatigue Analysis

A SPOT-WELD FATIGUE ANALYSIS MODULE IN THE MSC/FATIGUE ENVIRONMENT (Acrobat 256KB)

Peter Heyes--nCode International Limited

Mikael Fermér--Volvo Car Corporation

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

 

A STEPWISE APPROACH FOR FATIGUE EVALUATION OF ENGINE ACCESSORIES PRIOR TO PROTOTYPING USING HYBRID MODELLING TECHNOLOGY (Acrobat 1.7MB)

L. Gielen--LMS International

M. Brughmans--LMS International

C. Petellat--MACK

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

 

General Stress Analysis

APPLICATIONS OF FINITE ELEMENT ANALYSIS FOR AN IMPROVED MUSICAL INSTRUMENT DESIGN (Acrobat 896KB)

Mark Carlson--Fender Musical Instruments Corporation

ABSTRACT: Implementation of finite element analysis and proof of its power as a design tool to an industry unfamiliar with this type of technology will be demonstrated through the use of MSC.Nastran and MSC/ARIES to develop a comprehensive guitar neck system. This system will provide a better playing, better sounding instrument by accounting for the following:

• bending and twisting of the neck due to string forces
• bending and twisting of the neck due to moisture content expansion forces
• the cylindrical orthotropic nature of wood
• individual musician's preferences (neck adjustment capability)
• elimination of less resonant "dead spots" which occur for certain notes on the neck

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

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

 

COMPARISON OF THE MSC.Nastran AND HOLOGRAPHIC INTERFEROMETRY DATA ON A LOCAL STRAIN/STRESS EVALUATION IN THE ELASTO-PLASTIC RANGE (Acrobat 992KB)

A.S. Dzuba--Moscow Institute of Physics and Technology

V.D. Grigoriev--Moscow Institute of Physics and Technology

V.S. Pisarev--Moscow Institute of Physics and Technology

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

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

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

 

COMPARISON OF MSC.Nastran ANALYSIS RESULTS TO SOME WELL KNOWN CLOSED FORM SOLUTIONS TO GUIDE MODELING OF VEHICLE STRUCTURES (Acrobat 1.3MB)

Bijan K. Shahidi--Ford Motor Company

John V. Fazio--Ford Motor Company

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

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

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

 

MSC'S SOLVERS PREDICT THE BEST ATTACHMENT OF THE SUNBEAM TIGER FIBERGLASS FRONT-END (Acrobat 160KB)

Gert Lundgren--LAPCAD Engineering

ABSTRACT: This paper demonstrates how MSC's finite element technology can be utilized by the individual hobbyist, for the purpose of solving what traditionally is considered to be a task for the specialist. It shows how the solver helps the individual understand the problem, via the use of modal analysis. It also highlights how finite element analysis is used as a 'what if' tool, and thereby helps the user focus on a practical solution.

 

STRESS DISTRIBUTIONS IN MANDIBLES AROUND OSSEO-INTEGRATED IMPLANTS, ACCORDING TO THE OCCLUSION PATTERN, USING MSC.Nastran THREE-DIMENSIONAL MODELING (Acrobat 1.8MB)

Wolodymir Boruszewski--Instituto Nacional de Pesquisas Espaciais

Pedro Tortamano Neto--Universidade de São Paulo

Tetsuo Saito--Universidade de São Paulo

ABSTRACT: Stress distribution induced by mastication loads in bones holding osseointegrated implants, has been studied by many authors. One of the main reasons for that research is that stress concentration in a specific bone region, can unchain the process of bone reabsorption (loss with contraction) and, consequently, the failure of the implant-based therapy.

The proper choice of the occlusion pattern, hereafter considered the way prosthetic and dental cusps fit together, is fundamental for the homogeneous distribution of mastication loading around implants that totally support the prosthesis.

Through the Finite Element Method, the stress distribution around the prosthesis supporting implants has been studied. Two kinds of occlusion patterns have been considered: canine guide and balanced occlusion. The three-dimensional finite element model of the lower jaw with a prosthesis supported by six osseointegrated implants was developed and analyzed regarding both loading (occlusion) conditions. MSC/XL was used for pre and post-processing and MSC.Nastran for the analysis. Considering just the biomechanical aspects, it was observed that:

• The balanced occlusion shows stress distributions around the implants more homogeneous than the canine guide;
• The regions around distal (border) implants on both sides of the mandible were the most stressed;
• The working side shows higher stress concentration in both simulations. Many interesting challenges were identified allowing to expect for increasing interest in this interdisciplinary field of research.

 

Optimization

DYNAMIC CORRELATION STUDY TRANSFER CASE HOUSINGS (Acrobat 224KB)

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.

 

NASOPT: A FLEXIBLE OPTIMIZATION CAPABILITY FOR MSC.Nastran (Acrobat 64KB)

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 MSC.Software Corporation.

 

PRACTICAL GLOBAL-LOCAL DESIGN OPTIMIZATION OF VEHICLE BODY-IN-WHITE STRUCTURES (Acrobat 1MB)

Paramjot Bedi--Ford Motor Company

Metin Dede--Ford Motor Company

Greg Moore--The MSC.Software 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)

W.A. Holzmann--GenCorp Corporation

V.J. Wagner--The MSC.Software 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.

 

p-elements

THE APPLICATION OF INTERFACE ELEMENTS TO DISSIMILAR MESHES IN GLOBAL/LOCAL ANALYSIS (Acrobat 704KB)

John E. Schiermeier--The MSC.Software 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)

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.

 

AN INTEGRATED COMPUTER AIDED ENGINEERING TOOL FOR AIRCRAFT TRANSPARENCY DESIGN ANALYTICAL DESIGN PACKAGE--ADP (Acrobat 4.2MB)

J.E. Wuerer--The MSC.Software 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 Design Package (ADP) is intended to facilitate technology transfer to industry. The analysis system is capable of a wide range of design and manufacturing applications.

 

INTEGRATION OF MSC.Patran WITH SANDIA NATIONAL LABORATORY'S EXODUS II DATABASE SYSTEM (Acrobat 640KB)

Ken Walker--The MSC.Software Corporation

ABSTRACT: This paper highlights the development, enhancement and use of the MSC.Patran "Preference" at Sandia. This preference integrates MSC.Patran with the EXODUS II database. The development of the preference demonstrates the flexibility of MSC.Patran's open architecture. There were some interesting challenges not normally encountered when integrating MSC.Patran with commercial FEA codes. Also, as the preference has been enhanced and upgraded through four MSC.Patran release cycles several development concepts have been discovered. Production use of the preference is now expanding at Sandia and other locations. Several examples will be presented of models developed at the labs. Finally, future development options will be outlined.

 

INTERFACING MSC.Patran WITH EXTERNAL SURFACE MESHERS (Acrobat 256KB)

R. Shanmugasundaram--Computer Sciences Corporation

Jamshid Samareh--Computer Sciences Corporation

ABSTRACT: This paper describes interfacing external unstructured meshers with MSC.Patran. The developed interface called GUMPI (Geolab Unstructured Mesher/Patran Interface) is a collection of PCL(Patran Command Language) and ANSI-C codes that manages the data between MSC.Patran and an external unstructured mesher. The details of the data management is transparent to the user. However, efforts were made so that the user inputs to the external mesher is a simple to use as the internal meshing capabilities within MSC.Patran. Specifically, two different advancing front unstructured meshers called FELISA (Finite Element London Imperial Swansea Ames) and Vgrid have been interfaced with MSC.Patran through GUMPI. The interface demonstrates the ease at which external codes can be interfaced to MSC.Patran.

 

USING MSC.Patran FOR PRE- AND POSTPROCESSING FOR SPECIALIZED FEM CODES WHICH ARE NOT IN THE STANDARD MSC.Patran LIBRARY (Acrobat 448KB)

Daniel D. Jensen--University of the Pacific

ABSTRACT: MSC.Patran is commonly used in industry and academia as a pre- and postprocessor for commercially available FEM codes like MSC.Nastran, ANSYS, ABAQUS and others. However, a significant amount of analysis and research continues to be done with specialized FEM codes which do not have built in interfaces to MSC.Patran or any other widely available pre- or post processor. The present work provides a basic interface which allows models built in PATRAN access to the data necessary to build standard input decks for specialized FEM codes which are not supported by PATRAN. In addition, details are given for importing the results from analysis done with a specialized code back into PATRAN for visualization. An example is given which shows the ease of use of the interface. The interface presented provides an extremely expedient solution to the alternative of writing your own pre-and postprocessor.

 

Spacecraft

APPROXIMATE DYNAMIC MODEL SENSITIVITY ANALYSIS FOR LARGE, COMPLEX SPACE STRUCTURES (Acrobat 416KB)

Timothy S. West--McDonnell Douglas Aerospace

ABSTRACT: During the design of large, complex space structures, the structural analyst needs to understand the sensitivity of transient load predictions to uncertainties in critical structural vibration modes and forcing inputs. These questions arise both early in the design cycle, when models are simple and unrefined, and in the later stages of design, when models can be very complex and expensive to analyze. Therefore, the need for rapid, inexpensive assessment of these sensitivities exists at all design stages. Large, complex space structures such as International Space Station (ISS) are expensive to analyze with traditional sensitivity methods because of the tremendous number of design variables and analysis degrees of freedom. A rapid, inexpensive model sensitivity analysis method has been developed that uses modal information from a baseline model analyzed with MSC.Nastran Normal Modes Analysis. The method develops the system transfer function, and randomly alters the frequency and mode shape parameters of selected structural modes in the frequency domain to produce new, altered models. These new models are then used to calculate variations in transient response to known forcing inputs. The method produces approximate sensitivity information rapidly and inexpensively and can be used to assess designs at any time in the design cycle. It has been used to study ISS structural interface load sensitivities to dynamic model uncertainties. The method is presented with simple examples to illustrate its use.

 

DEVELOPMENT OF SPACE STATION LOADS DUE TO ON-ORBIT THERMAL ENVIRONMENTS (Acrobat 288KB)

Charles A. Jacobson, Jr--McDonnell Douglas Aerospace

Robert A. Rudd--McDonnell Douglas Aerospace

ABSTRACT: The International Space Station (ISS) primary structural elements are to be assembled and operated in the severe on-orbit thermal environment. This environment is widely varying, resulting in a broad range of structural load conditions defined by parameters such as spacecraft articulating geometry, orbit inclination, flight attitude and altitude, and the annual solar cycle. This paper describes the integrated analysis approach developed using detailed MSC.Nastran structural models, to compute thermally induced loads and deflections specifications for the ISS pre-integrated truss (PIT) segments. Fatigue load spectra development due to orbital thermal cycling is also described. Aspects of interface attachment mechanisms to accommodate thermal expansion and contraction and allow autonomous alignment and mating of the ISS PIT segments are described. An approach is also presented for evaluating thermal/structural effects for the large array of thermal conditions under which on-orbit assembly operations can occur.

 

Test/Analysis Correlation

HIGH CONFIDENCE PERFORMANCE PREDICTION TO IMPROVE THE VEHICLE DEVELOPMENT PROCESS (Acrobat 32KB)

N. Purushothaman--Ford Motor Company

M. Menon--Ford Motor Company

P. Randle--Ford Motor Company

C. Rivard--Ford Motor Company

H. Chen--Ford Motor Company

ABSTRACT: Ford is increasingly using CAE tools to speed up the product development process and replace hardware prototypes while bringing new products to market. The use of an analytical prototype allows performance to be predicted in advance of hardware proveout. Many design iterations can be performed, thus producing a world class vehicle. The accuracy of these predictions for a given attribute, and how the resultant design recommendations are integrated with other attributes has remained a major issue for the CAE community. During the recent development of a new vehicle all CAE disciplines (Safety, NVH, Durability, Vehicle Dynamics, etc.) were successfully combined to "sign-off" a design based entirely on CAE.

This paper explains how the Durability and NVH CAE attributes employed MSC.Nastran to produce high confidence results as part of an integrated process which allowed the vehicle to be verified for the Global and local performance at approximately 3 years to job 1.

 

Thermal Analysis

IMPLEMENTATION AND VERIFICATION OF A COUPLED FIRE MODEL AS A THERMAL BOUNDARY CONDITION WITHIN P3/THERMAL (Acrobat 64KB)

D. M. Hensinger--Sandia National Laboratories

L. A. Gritzo--Sandia National Laboratories

J. A. Koski--Sandia National Laboratories

ABSTRACT: A user-defined boundary condition subroutine has been implemented within P3/THERMAL to represent the heat flux between a non-combusting object and an engulfing fire. The heat flux calculation includes a simple two dimensional fire model in which energy and radiative heat transport equations are solved to produce estimates of the heat fluxes at the fire-object interface. These estimates reflect the radiative coupling between a cold object and the flow of hot combustion gasses which has been observed in fire experiments. The model uses a database of experimental pool fire measurements for far field boundary conditions and volumetric heat release rates. Taking into account the coupling between a structure and the fire environment is an improvement over the sT 4 approximation frequently used as a boundary condition for engineered system response and is the preliminary step in the development of a fire model with a predictive capability. This paper describes the implementation of the fire model as a P3/THERMAL boundary condition and presents the results of a verification calculation carried out using the model.

 

THERMAL CONDUCTION AND THERMAL CONVECTION AS A SINGLE THEORY SOLVED WITH FINITE ELEMENT METHOD (Acrobat 64KB)

Mircea Bocioaga

ABSTRACT: This paper presents a theory in which thermal conduction and thermal convection is solved with a single equation. This equation is a generalised form of Fourier law. The paper presents a method, based on Ritz-Galerkin theory, for solving this equation. A main application for this equation could be the heat transfer study between a fluid flow and a solid body. The most important element is, that this theory is done without the convection theory and without the computation of a convection coefficient. The domain in which the equation is solved is a finite element. The solution is a linear equation system where the unknown quantities are the temperature in the finite element nodes.

 

THERMAL DESIGN OF POWER MOSFETS OPERATING IN PARALLEL (Acrobat 256KB)

V. Parameswaran--Rockwell International

ABSTRACT: The objective of this paper is the thermal design analysis of power MOSFETs operating in parallel and which uses phase change immersion cooling. The heat generation (electrical power dissipation) in such devices is a function of the device resistance and the current through the device, both of which are functions of junction temperature of the device. The junction temperature, in turn, depends on the thermal resistance between the junction and the fluid which is a function of the boiling heat transfer coefficient, and the power dissipated. The analysis presented in this paper considers this complex interdependency in the design of heat sinks such that the temperature is below the limit required by reliability consideration. Thermal coupling of MOSFETs minimizes the junction temperature.

 

USE OF FINITE ELEMENT MODELS FOR DETERMINING RADIATION GEOMETRIC VIEW FACTORS (Acrobat 64KB)

Patrick Edson--Eastman Kodak Company

Victor Genberg--Eastman Kodak Company

ABSTRACT: Geometric view factor data is compared, using curved and planar surfaces, to determine the model detail necessary to accurately obtain radiation results for models of curved objects with planar finite elements. A finite cylinder with closed ends, for which the closed-form solution is known, is used as the reference. The results demonstrate that a moderately detailed mesh provides accurate solutions, allowing the use of a single condition and radiation model for models of this nature.