Space Shuttle: The Need for Substructuring
NASTRAN and substructuring techniques for structural analysis of complex space shuttle structures
H R Grooms↗
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Comparison of the substructures and properties of nickel, TD-Ni, Chromel-A, Inconel 600, and TD-NiCr following explosive-shock deformation
Substructures and properties of Ni, Chromel A, Inconel 600 and TD-NiCr following explosive shock load deformation, using electron microscope
Foltz, J. V.↗
Applications of NASTRAN substructuring
The application of substructuring techniques are described for two example problems, a square plate and the static analysis of a frame-wall interaction problem in multistory structures. A DMAP routine for calculating the multipoint constraint forces is presented.
Narayanaswami, R.↗
Substructure analysis techniques and automation
A basic automated substructure analysis capability for NASTRAN is presented which eliminates most of the logistical data handling and generation chores that are currently associated with the method. Rigid formats are proposed which will accomplish this using three new modules, all of which can be added to level 16 with a relatively small effort.
Hennrich, C. W.↗
Application of a substructuring technique to the problem of crack extension and closure
A substructuring technique, originally developed for the efficient reanalysis of structures, is incorporated into the methodology associated with the plastic analysis of structures. An existing finite-element computer program that accounts for elastic-plastic material behavior under cyclic loading was modified to account for changing kinematic constraint conditions - crack growth and intermittent contact of crack surfaces in two dimensional regions. Application of the analysis is presented for a problem of a centercrack panel to demonstrate the efficiency and accuracy of the technique.
Armen, H., Jr.↗
The automated multi-stage substructuring system for NASTRAN
The substructuring capability developed for eventual installation in Level 16 is now operational in a test version of NASTRAN. Its features are summarized. These include the user-oriented, Case Control type control language, the automated multi-stage matrix processing, the independent direct access data storage facilities, and the static and normal modes solution capabilities. A complete problem analysis sequence is presented with card-by-card description of the user input.
Field, E. I.↗
A review of substructure coupling methods for dynamic analysis
The state of the art is assessed in substructure coupling for dynamic analysis. A general formulation, which permits all previously described methods to be characterized by a few constituent matrices, is developed. Limited results comparing the accuracy of various methods are presented.
Craig, R. R., Jr.↗
A NASTRAN DMAP alter for the coupling of modal and physical coordinate substructures
A method is described to derive a generalized coordinate model consisting of flexible cantilever modes and rigid body modes from a physical coordinate model using a direct matrix abstraction procedure alter to rigid format 3. This model can readily be coupled to other substructures using modal synthesis techniques. It allows the use of a reduced size model for structural analyses while maintaining the capability of recovering the accelerations, forces, stresses, etc., from the original, large, complex model. This output recovery is accomplished with the use of a loads transformation matrix which relates the output parameters to the modal coordinate accelerations. In addition, a method is described to synthesize structural models consisting of hybrid coordinates for use in dynamic response analyses where one structure is described using physical coordinates and the other using generalized modal coordinates.
Wilson, T. L.↗
Condensing loaded points for transients by substructuring
A technique for condensing dynamic loading points is described. The method was applied to substructure transient solutions and was found to be very effective.
Butler, T. G.↗
Development and analysis of the learjet 54/55 fuselage NASTRAN model using substructure techniques
Development and analysis of the Learjet 54/55 fuselage NASTRAN model is presented. This structure was broken down into several substructures to make the modeling and analysis effort more manageable. Since the geometry was fairly complex in some areas and in order to provide flexibility for future configuration studies, a series of local coordinate systems were used to describe the model. This work was accomplished using several different computer systems, the more recent of which were connected by a high speed data communications lines to perform the tasks of model generation and NASTRAN analysis.
Boroughs, R. R.↗
Substructure within clusters of galaxies
Surface number density contour maps based on Dressler's (1976, 1980) studies of 65 rich clusters are presented to demonstrate the frequent occurrence of substructure in these dense systems. A prescription is given for examining the significance of such structure and it is shown that structure on scales equal to or larger than 0.24 Mpc (H0 = 100 km/s Mpc) is present in approximately 40% of the clusters in this sample. Many of the remaining clusters are elongated. The contour plots are useful for comparison with X-ray surface brightness maps. Together with available velocity data, they also serve warning that many rich clusters may not be simply characterized by a single core radius and velocity dispersion.
Geller, M. J.↗
Combining Structural and Substructural Mathematical Models
Automation reduces input length and potential data-entry errors. Matrix Automated Reduction and Coupling (MARC) program used for combining NASTRAN substructural models with primary structural model MARC also constructs job-control language (JCL) stream for NASTRAN batch job that utilizes previously-written user library of dynamic models. Minimizes lengthy input and reduces potential data-entry errors. MARC procedure used in assembling Space Shuttle orbiter dynamic models since 1983 and reduced NASTRAN modeling input time by as much as 50 percent. MARC program written in FORTRAN IV for interactive execution.
Choa, V. K.↗
On substructuring algorithms and solution techniques for the numerical approximation of partial differential equations
Substructuring methods are in common use in mechanics problems where typically the associated linear systems of algebraic equations are positive definite. Here these methods are extended to problems which lead to nonpositive definite, nonsymmetric matrices. The extension is based on an algorithm which carries out the block Gauss elimination procedure without the need for interchanges even when a pivot matrix is singular. Examples are provided wherein the method is used in connection with finite element solutions of the stationary Stokes equations and the Helmholtz equation, and dual methods for second-order elliptic equations.
Gunzburger, M. D.↗
BUNVIS-RG - An exact buckling and vibration program for lattice structures, with repetitive geometry and substructuring options
The exact FORTRAN computer program BUNVIS-RG which uses an exact stiffness matrix method to find eigenvalues and modes of three-dimensional planes, is presented in detail. It is shown that BUNVIS-RG solution times can be predicted fairly accurately from two computer dependent constants, the number of nodes and members in the frame, and the maximum node number difference of any pair of connected nodes. The program's use of repetitive geometry, stayed column substructures and nonuniform member options was found to enhance efficiency and range of application.
Anderson, M. S.↗
Modeling of multi-rotor torsional vibrations in rotating machinery using substructuring
The application of FEM modeling techniques to the analysis of torsional vibrations in complex rotating systems is described and demonstrated, summarizing results reported by Soares (1985). A substructuring approach is used for determination of torsional natural frequencies and resonant-mode shapes, steady-state frequency-sweep analysis, identification of dynamically unstable speed ranges, and characterization of transient linear and nonlinear systems. Results for several sample problems are presented in diagrams, graphs, and tables. STORV, a computer code based on this approach, is in use as a preliminary design tool for drive-train torsional analysis in the High Altitude Wind Tunnel at NASA Lewis.
Soares, Fola R.↗
Dynamic substructuring for shock spectrum analysis using component mode synthesis
Component mode synthesis was used to analyze different types of structures with MSC NASTRAN. The theory and technique of using Multipoint Constraint Equations (MPCs) to connect substructures to each other or to a common foundation is presented. Computation of the dynamic response of the system from shack spectrum inputs was automated using the DMAP programming language of the MSC NASTRAN finite element code.
Mcpheeters, Barton W.↗
On the stability of the creep substructure in NaCl single crystals
Microstructural observations were conducted on NaCl single crystals after creep. The microstructure after a stress increase followed by a stress decrease consisted primarily of cells; no significant number of subgrains were observed although they were present in the microstructures produced during uninterrupted tests. Prestraining in the exponential creep regime produced an uniform distribution of dislocations and a few subboundaries which transformed to equiaxed subgrains when tested in the power law creep region. This substructure was similar to that observed in an as-received specimen deformed to an equivalent strain. Prior creep in the power law creep region produced equiaxed subgrains whose boundaries were found to be mechanically stable when the specimen was retested in the exponential creep region. The role of subboundary migration in the formation of new subgrains is discussed.
Raj, S. V.↗
Modeling of connections between substructures
It is demonstrated here that complete checkout of a basic substructure can be done under the special circumstance of a sliding connection with offsets. Stiff bar connectors make this possible so long as the bar coordinates are aligned with the displacement coordinates at the sliding surface.
Butler, Thomas G.↗