Accession Number:

ADA230682

Title:

A Comparison of the Optimization and Analysis of Doubly Curved Shells Using MSC/NASTRAN and ASTROS

Descriptive Note:

Master's thesis

Corporate Author:

AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING

Personal Author(s):

• Dewsnap, John R.

Report Date:

1990-12-01

Pagination or Media Count:

88.0

Abstract:

This study identified techniques and software available for the optimization of doubly curved shells and applied them in the context of a large nozzle shape. An optimality criteria scheme that can reduce solution time was evaluated and compared to the Method of Feasible Directions. MSCNASTRAN and ASTROS were used to perform finite element analysis and optimization, and the results were compared to the theory. The programs give virtually identical results, and if plates and shells are carefully modeled, then stresses, displacements and modes are accurate to within ten percent. A Mindlin-type axisymmetric finite element was implemented in ASTROS that preserved accuracy and reduced the size of the stiffness matrix by a factor of four. Nozzle optimization was performed using static pressure and thermal loads, constrained by the Von Mises stress criteria. Software errors were documented in ASTROS, and four characteristic stress regions identified for the optimized nozzle.

Descriptors:

• *STRESSES
• COMPUTER PROGRAMS
• OPTIMIZATION
• MATRICES(MATHEMATICS)
• FINITE ELEMENT ANALYSIS
• LOADS(FORCES)
• COMPARISON
• STIFFNESS
• DISPLACEMENT
• SHAPE
• ACCURACY
• SHELLS(STRUCTURAL FORMS)
• REGIONS
• TIME
• CURVATURE
• SOLUTIONS(GENERAL)
• ERRORS
• NOZZLES
• PRESERVATION
• COMPUTER PROGRAM VERIFICATION
• STATIC PRESSURE
• THERMAL PROPERTIES

Subject Categories:

• Numerical Mathematics
• Computer Programming and Software
• Fluid Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE