Engineering topics

Sawyer, P. L.

Publications and source records attributed to Sawyer, P. L..

6 records

NASA NTRS1980

An approach to simulation of the finite element machine

The paper describes the simulation approach for the finite element machine (FEM), a special-purpose computer for structural analysis calculations under development at the NASA-Langley Research Center. The FEM consists of an array (1000 or more) of general-purpose microcomputers performing structural analysis in an asychronous parallel manner. A simulator of sufficient flexibility to model the behavior of the FEM on many levels has been designed and coded, and verification has begun using the experimental FEM hardware. The structure of the simulator is described, and preliminary simulation results are presented.

Sawyer, P. L.↗

NASA NTRS1979

The application of microprocessor technology to in-flight computation

A modular design of a general purpose microprocessor-based computer to perform in-flight computations for cross-country soaring pilots is described. The basic requirements for the system are discussed. Several specialized applications of the computer are presented, including real-time pilot feedback and flight-test data acquisition and reduction.

Sawyer, P. L.↗

NASA NTRS1978

Numerical procedure to determine geometric view factors for surfaces occluded by cylinders

A numerical procedure was developed to determine geometric view factors between connected infinite strips occluded by any number of infinite circular cylinders. The procedure requires a two-dimensional cross-sectional model of the configuration of interest. The two-dimensional model consists of a convex polygon enclosing any number of circles. Each side of the polygon represents one strip, and each circle represents a circular cylinder. A description and listing of a computer program based on this procedure are included in this report. The program calculates geometric view factors between individual strips and between individual strips and the collection of occluding cylinders.

Sawyer, P. L.↗

NASA NTRS1978

Development of methodology for optimum design of structures at elevated temperatures

This paper surveys a number of activities aimed at applying optimum design techniques to structures where high temperatures are important design considerations. An improved variant of fully-stressed design (FSD), denoted thermal fully-stressed design (TFSD), is described which converges significantly faster than FSD for problems where thermal stresses are comparable in magnitude to mechanical stresses. Second, an optimality criterion is described for sizing structures subjected to temperature constraints. Simultaneous requirements on strength and temperatures are handled by two different techniques: (1) a state-of-the-art mathematical programming method and (2) the optimality criterion technique for temperature constraints combined with FSD for strength constraints. A method is described to optimize the insulation and ply thicknesses of an insulated composite panel with a time-varying temperature applied to the outer surface of the insulation and a general set of in-plane loads applied to the panel.

Adelman, H. M.↗

NASA NTRS1978

A multi-microprocessor system for finite element structural analysis

During the last few years, advances in microprocessor technology have spurred a renewed interest in special-purpose computers. The microprocessor has become small, inexpensive, and powerful enough to be considered as a building block for special-purpose hardware. A description is presented of the architecture of a prototype 'finite element machine' currently being built. Attention is given to details regarding the finite element analysis problem, the arrangement of the processors as finite element nodes in the structural model, the influence of the architecture on the solution algorithm, interprocessor communication primitives, and the performance of the finite element machine.

Jordan, H. F.↗

NASA NTRS1977

Inclusion of explicit thermal requirements in optimum structural design

A finite-element based procedure is described for obtaining minimum mass designs of structures subjected to combined thermal and mechanical loading and both strength and thermal constraints. The procedure is based on a mathematical programming method using the Sequence of Unconstrained Minimizations Technique (SUMT) in which design requirements are incorporated by an exterior penalty function. The procedure is limited to steady-state temperatures which are controlled by structural sizing only. The optimization procedure is demonstrated by the design of a structural wing box with both mechanical loading and external heating, subject to design constraints on stress, minimum gage, and temperature. The final design for these conditions is compared with a corresponding design in which temperature constraints are omitted.

Adelman, H. M.↗