1983 World Users' Conference

The conference proceedings for the 1983 World Users' Conference are now available on-line in Adobe Acrobat PDF format. (The Adobe Acrobat Reader software is available for free download from Adobe's web site at www.adobe.com).

MSC/NASTRAN STATUS REPORT (Acrobat 2.08MB) #0183, 29pgs.
R.H. Macneal and M.A. Gockel -- The MacNeal-Schwendler Corporation

A PowerPoint presentation.

MSC/NASTRAN AND THE APOLLO COMPUTER (Acrobat 397K) #0283, 7pgs.
C.W. McCormich -- The MacNeal-Schwendler Corporation

Charts and graphs.

DIFFUSE ILLUMINATION WITH MSC/NASTRAN (Acrobat 1.29MB) #0383, 18pgs.
Victor Genberg -- University of Rochester
Don Oinen and Sharon Fronheiser -- Eastman Kodak Company

ABSTRACT: The reflection of light from ideal Lambertian (diffuse) surfaces follows the same physical laws as the radiation of heat. Thus, the thermal radiation capabilities of MSC/NASTRAN can be used by analogy to analyze the behavior of illumination systems containing diffuse surfaces. The view factor calculation capability and the mesh generation capability within MSC/NASTRAN facilitate the analysis. A model (description included) of a simple illumination system are shown to agree closely with measured values.

CRACK PROPAGATION ANALYSIS USING NASTRAN SUPERELEMENT CAPABILITY
(Acrobat 615K) #0483, 10pgs.
Zvi Zaphir -- Israel Aircraft Industries, LTD

ABSTRACT: Crack propagation in a Delta wing skin of an aircraft is analyzed. The main effort in this analysis is the NASTRAN finite element (FE) computation needed to evaluate the stress intensity factor KI. KI is computed using the energy release rate G obtained by a numerical differentiation of the strain energy with respect to the crack-length. The strain energy difference is evaluated from a finite element analysis of the wing structure carried out for different crack-lengths.
The FE calculation is performed with NASTRAN using the superelement option. The FE mesh consists mainly of the CQUAD4 isoparametric fournode elements. The crack origin and direction of propagation were chosen to conform with the Australian Mirage III wing test results. Good correlation is obtained when comparing the FE results of KI with those of Rooke and Cartwright. Good correlation is also obtained between test results and the crack growth analysis, showing that this analytical approach is suitable for engineering purposes.

SOLID MODELING TECHNIQUES APPLIED TO A COMPLEX SOLID TURBINE BLADE
Paul A. Zelenski-- PDA Engineering

No text or abstract available.

MODELING THE INTERFACE BETWEEN SHELL AND SOLID ELEMENTS (Acrobat 2.76MB) #0683, 43pgs.
Denis J. Feld and Jean G. Soudry -- Goodyear Aerospace Corporation

ABSTRACT: In many practical finite element models, some portions of the structure are best modeled with shell elements and others with solids. This paper evaluates several alternatives to modeling the interface between the shell and solid elements. The alternative methods are screened on a simple Timoshenko beam whose solution is known. It is demonstrated that there are acceptable and poor methods of modeling the interface. The acceptable methods are characterized by satisfying kinematic relationships of displacements between the solid and shell elements - without overconstraint. A plate finite element model loaded in bending is used to further verify the acceptability of using the NASTRAN rigid elements at the interface of shell and solid elements. Two basic methods applicable to a wide range of modeling situations are suggested. Either RBAR of RBE3 interfaces produce acceptable results if properly applied.

DESIGN SENSITIVITY ANALYSIS IN MSC/NASTRAN (Acrobat 1.01MB) #0783, 18pgs.
Robert S. Lahey -- The MacNeal-Schwendler Corporation

ABSTRACT: The purpose of this paper is to describe the capabilities and theoretical basis for Design Sensitivity Analysis in MSC/NASTRAN. Design Sensitivity Analysis (DSA) is a design tool for estimating effects of many interrelated design variables such as element properties and materials on the structural response. The primary functions of DSA are to compute the values of the design constraint functions and the design sensitivity coefficients. The design constraint functions are a set of upper/lower bounds on the structural response quantities such as grid point displacement, element force and stress, buckling load factor and natural frequency. The design sensitivity coefficients are defined as the gradients of the design constraint function with respect to the design variables at the current design point. The computation of the design sensitivity coefficients constitutes the major task of design sensitivity. The design sensitivity coefficients are useful in themselves as they give the designer a feel as to how the structure will respond to a proposed design change. In addition, these data are required by many optimization algorithms.

NONLINEAR ANALYSIS OF THE TEREX SCRAPER ROLLOVER PROTECTOR CAP
(Acrobat 1.71MB) #0883, 21pgs.
Charles Hunckler -- Engineering Methods, Inc.
Randy D. Austin -- Terex Corporation

ABSTRACT: A rollover test of the Terex Roll-Over Protective Cab has been conducted using finite element analysis. MSC/NASTRAN Version 61B, which has the capability of including geometric nonlinearities and material nonlinearities, was used. The analysis predicted the extent of permanent deformation of the compartment and energy absorbed during the load test. The analysis was done at lower cost than hardware testing of a prototype would involve. In the future, this nonlinear finite element analysis can be used to finalize operator compartment designs before hardware tests are conducted. The method requires the number of hardware tests and hardware changes required, and, therefore, reduced the cost and time to develop the product.

MSC/NASTRAN SOLUTION 99 EXPERIENCE (Acrobat 1.08MB) #0983, 18pgs.
Joel Gerdeen and Shan Lin -- FMC Corporation

ABSTRACT: Geometric and material nonlinearity is a common occurrence in dynamic analysis of structures and machinery. The MSC/NASTRAN SOL 99 procedure became available in Version 62 to analyze GNL and MNL transient loading problems. This paper illustrates SOL 99 analysis of industrial gear train applications with primary emphasis on use of the gap element to represent backlash. A small drop container analysis is also presented with comparisons made to the ANSYS gap element in transient analysis.

SHUTTLE TILE THERMAL ANALYSIS VIA NASTRAN (Acrobat 885K) #1083, 14pgs.
Marcus S. Murbach -- Informatics General Corporation

ABSTRACT: The Space Shuttle Columbia carried a Tile Gap heating Experiment designed to measure the temperatures within the gaps of the Thermal Protection System (TPS) on the underside of the spacecraft. The thermal analysis entailed the derivation of appropriate boundary conditions from thermocouple data and the calculation of heating rates using NASTRAN. The resulting temperature distributions and heating rates provide information concerning the dependence of convective flow on tile-gap geometry. Results of the work will provide a data base for improved TPS design for future entry vehicles.

MODELING OF NONLINEAR ELASTIC STRUCTURES USING MSC/NASTRAN (Acrobat 2.49MB) #1183, 46pgs.
Ken Blakely and William B. Walton -- Anco Engineers, Inc.

ABSTRACT:There are numerous structures that contain nonlinear elastic elements. Such elements possess nonlinear force-deflection relationships, yet they are elastic since they load and unload along the same force-deflection curve. Representing nonlinear elastic behavior can be accomplished using the pseudo-force procedure for which the system stiffness matrix remains unchanged, and the deviations from linearity are treated as additional applied loads. This approach, utilizing the MSC/NASTRAN NOLIN1 dynamic load in the linear transient analysis procedure, is computationally no more expensive than is a comparable, purely linear analysis.
Nonlinear elastic elements are described for actual structures. Then, the theory behind the pseudoforce technique is briefly discussed. Next, two large sample problems are presented: in the first, base motion is applied to a structural system supported by nonlinear rubber shock isolators; in the second, snapback and high-level seismic excitations are applied to a piping system supported by nonlinear hangers. Results from the snapback simulations are compared to experimental measurements, and inclusion of the nonlinear supports is shown to more accurately reproduce the test data than does an equivalent linear model. Finally, some considerations are given in regard to modeling techniques and time step selection for analyzing nonlinear elastic structures via the pseudoforce approach.

DYNAMIC ANALYSIS AND STRESS CONTOUR PLOTTING (ORAL PRESENTATION)
W.E. Capers -- Ford Motor Company

ABSTRACT: Dynamic analysis is playing an ever increasing part in engineering analysis of component parts. Designs that appear favorable under static analysis, using normal operating load condition, occasionally develop cracks or outright failures during prototype testing. Ford Motor Company deals with this problem by theoretical analysis, and laboratory evaluation of prototype parts. The theoretical approach involves using MSC-NASTRAN solution 30. Solution 30 can become tedious due to the large number of grid points on the FEA model required to completely define the regions of high stress on the component. This problem has been eliminated by the development of a d-map alter for MSC-NASTRAN Solution 30. The alter allows stress contour and displacement plots to be obtained from Solution 30 for any selected frequency range.

RANDOM VIBRATIONS IN COMPLEX ELECTRONIC STRUCTURES (Acrobat 1.30MB ) #1383, 13 pgs.
A. Hatheway -- Alson E. Hatheway, Inc.

ABSTRACT: Finite element methods can predict the stresses and strains in complex electronic structures. The accuracy of the results are effected by the modeling strategy used and the distribution of mass, stiffness and damping in the structure. Mass and stiffness are distributed during the normal modeling procedure of defining geometry, elements and materials. Damping, however, is usual distributed "uniformly" through the model or sometimes specified as a function of frequency, as in modal damping. Various damping distributions have been explored with the use of material damping entered on the MAT1 card. The redistribution of material damping has been found to influence the computational results and some combinations of material damping have substantially improved the correlation between MSC/NASTRAN analysis and random vibration test data.

EVALUATING MODAL CONTRIBUTIONS IN A NASTRAN FREQUENCY RESPONSE ANALYSIS (Acrobat 2.14MB) #1483, 27 pgs.
G.R. Parker and J. J. Brown -- Hughes Helicopter, Inc.

ABSTRACT: A special purpose (alter) program has been added to the MSC/NASTRAN modal frequency response rigid format (Solution 30), via the direct matrix abstraction program (DMAP) capability. The DMAP program allows an in-depth analysis of the frequency response on a per-mode basis. An example of how the program was applied to the modal frequency response analysis of Hughes Advanced Attack Helicopter is presented along with some unexpected results.

DMAP FOR DETERMINING MODAL PARTICIPATION (Acrobat 2.75MB) #1583, 45 pgs.
D.V. Schiavello -- D.V. Schiavello Enterprises, Inc.
J.E. Sinkiewicz -- The MacNeal-Schwendler Corporation

ABSTRACT: When performing eigenvalue analyses, it is usually necessary to establish the significance of individual modes. Parameters that are commonly used to assist in determining Modal Participation include Generalized Mass, Modal Participation Factors, and Effective Modal Mass. MSC/NASTRAN currently calculates only Generalized Mass when performing eigenvalue analysis. A DMAP alter package has been developed to provide MSC/NASTRAN users with additional information concerning Modal Participation. Features include: Modal Participation Factors; Effective Modal Mass; maximum values of eigenvectors; and Generalized Mass based on normalized eigenvectors of the physical structure. The last two items are particularly useful when Generalized Dynamic Reduction is used or when the "MASS" method of normalization is selected on the EIGR Bulk Data card. The theory and procedure required for the DMAP alter package, as well as a verification problem, are discussed. In addition, a method for calculating and plotting "Proportional Eigenvectors" is presented to provide a graphical representation of Modal Participation.

NONLINEAR PERTURBATION METHODS IN DYNAMIC REDESIGN (Acrobat 1.02MB) #1683, 12 pgs.
William J. Anderson, Ki-Ook Kim, Bingchen Zhi, Michael M. Bernitsas, Curtis Hoff, and Kyu-Nam Cho -- The University of Michigan

ABSTRACT: Many mechanical systems have poorly placed natural frequencies and undesireable mode shapes. Current methods of dynamic redesign work well for small changes in the eigenproblem. Practical dynamic redesign, however, often involves moderate changes in stiffness. The present research includes all nonlinear terms in an inverse perturbation procedure. Two new approaches allow moderate and large change. One method uses a penalty function with a minimum weight objective and a penalty term containing error in equilibrium for a given vibration mode. The other is a predictor-corrector approach based on an energy balance in a truncated set of modes. Both methods use the finite element code MSC/NASTRAN and require only one finite element analysis -- that of the original problem. The methods are more powerful than competing Taylor series methods, which have limited radii of convergence.

PREDICTION OF DAMPING IN STRUCTURES WITH VISCOELASTIC MATERIALS USING MSC/NASTRAN (Acrobat 2.74MB) #1783, 34 pgs.
Conor D. Johnson and David A. Kienholz -- CSA Engineering

ABSTRACT: This paper describes an efficient method for finite element modeling of structures containing a viscoelastic material. Modal damping ratios are estimated from undamped normal mode results by means of the modal strain energy method. Comparisons are given between results obtained by the MSE method implemented in MSC/NASTRAN, by various exact solutions for approximate governing differential equations, and by experiment. Results are in terms of frequencies, modal damping ratios, and mechanical admittances for simple beams, plates, and rings, as well as for an actual hardware application. Use of the finite element/MSE method in design of integrally damped structures is discussed.

A COMPARISON OF FREE COMPONENT MODE SYNTHESIS TECHNIQUES USING MSC/NASTRAN (Acrobat 2.65MB) #1883, 39 pgs.
D.R. Martinez and D.L. Gregory -- Sandia National Laboratories

ABSTRACT: MSC/NASTRAN was used to compare three techniques of component mode synthesis (CMS) using free modes. A free-free beam model was analyzed by the three methods and compared to the finite element results for the entire beam. The three CMS techniques use different combinations of assumed displacement vectors. Two of the techniques are available as standard options within MSC/NASTRAN. The third utilizes residual terms and is ideally suited to using results from an experimental data base to describe a portion of the model. For this technique, we have studied the effects of including residual terms only in the stiffness matrix or in both the mass and stiffness matrices, as well as neglecting the off-diagonal residual terms. Significant divergence of low frequency system modes was obtained when using one technique while excellent and identical convergence was obtained using the other two. Results are given for modal frequency convergence.

APPLICATION OF NASTRAN TO DESIGN AND ANALYSIS OF SPACESHIP EARTH (Acrobat 969K) #1983, 11 pgs.
Atis A. Liepins -- Simpson Gumpertz & Heger, Inc.

ABSTRACT: Spaceship Earth is the central pavilion of Disney's latest showcase, Epcot Center, at Walt Disney World in Orlando, Florida. It is the home of a ride and show depicting the history of communications. The structure is a complete geodesic sphere, 160 feet in diameter, elevated 14 feet above the ground, and supported by six legs. The focus here is on the design and analysis of the structural sphere and the transition structure.

CASING DEFLECTION ANALYSIS OF A TURBOFAN ENGINE (Acrobat 768K) #2083, 15 pgs.
O. Funatogawa -- Ishikawajima-Harima Heavy Industries Company, LTD.

ABSTRACT: The use of NASTRAN in carcass deflection analysis on a turbo-fan engine is described. The main purpose of the analysis in an early stage of a new engine development is to optimize engine geometrical configurations from the viewpoint of engine performance. Engine structural members are replaced by a mathematical model and NASTRAN input data is generated by an in-house pre-processor SANA/MESH. Some static analysis results are presented.

STRUCTURAL ANALYSIS OF A THERMOELECTRIC GENERATOR ELEMENT (Acrobat 1.17MB) #2183, 18 pgs.
James M. Newell -- Fairchild Space Company

ABSTRACT: Fairchild Space Company is currently assisting in a DOE program to develop a nuclear-powered thermoelectric generator for long distance space voyages. Known as the Modular Isotopic Thermoelectric Generator, the device differs from previous RTG designs in that it is built from identical generator sections or "slices", each producing the desired output voltage, which may be combined to meet the power requirements of any particular space mission. This paper outlines the structural analysis of the thermoelectric module or multicouple used in the MITG, as aided by the MSC/NASTRAN finite element code.

THREE-DIMENSIONAL STRESS ANALYSIS OF A HELICOPTER MAIN ROTOR HUB USING CYCLIC SYMMETRY (Acrobat 2.37MB) #2283, 43 pgs.
Richard L. Rotelli, Jr. -- Jordan, Apostal, Ritter Associates, Inc.

ABSTRACT: A three dimensional stress analysis of the new Main Rotor Hub design for the SH-2F helicopter was performed using the cyclic symmetry feature of MSC/NASTRAN. The FEMGEN interactive graphics mesh generator was used to create the one-eighth symmetric finite element model. The structural response of the rotor hub to several different loading conditions, as predicted by MSC/NASTRAN, was displayed graphically by the FEMVIEW interactive results viewing program. Presented in this way, the results of the NASTRAN analysis had a positive impact on the new design of the Main Rotor Hub.

RESULTANT FORCES AND MOMENTS IN STATIC AND DYNAMIC ANALYSIS
(Acrobat 573K) #2383, 11 pgs.
Peter Woytowitz -- Ford Aerospace and Communications Corporation

ABSTRACT: The theory and DMAP instructions for obtaining resultant force and moment vectors of an arbitrary set of static or dynamic forces are presented. The resultant moment vector is defined with respect to any point specified by the analyst. DMIG card are used to define the portion of the structure for which the resultant force and moment vectors are desired. Rigid body displacement vectors are used to calculate and sum the contributing moments and forces. The use of optional pre-processing programs for generation of the DMIG cards is discussed along with examples.