Engineering topics
Publications and source records attributed to Herting, D. N..
The user's guide is a handbook for engineers and analysts who use the NASTRAN finite element computer program supplements the NASTRAN Theoretical Manual (NASA SP-221), the NASTRAN User's Manual (NASA SP-222), the NASTRAN Programmer's Manual (NASA SP-223), and the NASTRAN Demonstration Program Manual (NASA SP-224). It provides modeling hints, attributes of the program, and references to the four manuals listed.
A new method for component mode synthesis was developed for installation in NASTRAN level 17.5. Results obtained from the new method are presented, and these results are compared with existing modal synthesis methods.
The implementation of a general three dimensional hydroelastic mode analysis capability in NASTRAN is presented. Finite elements with polyhedral shapes define the fluid; existing NASTRAN plate elements define the fluid/structure interface. Efficient solution methods were implemented to allow a separate structural matrix reduction and to allow connection of the fluid mass directly to a small set of grid points or modal coordinates representing the structure. Test case results for the various solution options are presented.
A mode synthesis development to be scheduled in the NASTRAN multi-level substructuring system for general dynamics applications is described. The method combines the better features of several state of the art mode synthesis techniques, yet is general enough to provide for any arbitrary combination of boundary degrees of freedom and normal mode boundary conditions. Normal modes or complex eigenvectors may be used in the definition of a structure component which may be combined with other components of any type. Combination structures fabricated from component modes may be processed as normal substructures, including further multi-stage mode synthesis reductions. Included are discussions of the user control of the system and advantages in actual application.
A computer code for the analysis of reinforced concrete structures was developed using NASTRAN as a basis. Nonlinear iteration procedures were developed for obtaining solutions with a wide variety of loading sequences. A direct access file system was used to save results at each load step to restart within the solution module for further analysis. A multi-nested looping capability was implemented to control the iterations and change the loads. The basis for the analysis is a set of mutli-layer plate elements which allow local definition of materials and cracking properties.
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.
A computer analysis was made of the hydroelastic interaction between a shell structure representing the space shuttle solid rocket motor case and an incompressible fluid during the slapdown phase of water impact. The large motions and hydroelastic response of the system were obtained by numerical integration of the combined hydrodynamics and structural equations of motion and are analyzed for a selected interval after the initial nozzle impact. The computerization of the slapdown hydroelastic capability was incorporated into the general purpose NASTRAN computer code. The development of the theoretical basis, a guide to the program's usage, results of correlation and parameter studies, and a detailed description of the computer code are also included.
In this paper a nonlinear transient, hydroelastic method is developed for response analysis of the Space Shuttle recoverable booster on water impact. At each time step, coupled equations of fluid flow and structure dynamics are solved with an iterative, self-correcting process. Rigid body motions are represented by large angle equations. Local deformations are represented by a NASTRAN-generated model of the three-dimensional structure. The fluid is represented by series solutions of the potential flow equation which include the effects of the local structure motions. The resulting water loads and structural stresses obtained will aid in qualification of the final structural design. Comparisons are made to experimental impact data to validate the method.
Adaptation of NASTRAN program to solve acoustic mode problems of solid rocket motor cavities by finite element method
Computer programs perform landing stability studies of mechanical impact system designs for advanced spacecraft. The programs consider variation in spacecraft vertical and horizontal velocity, attitude and orientation, shock strut load-stroke characteristics, and ground coefficient of friction.