Date of Award

Fall 1992

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical & Aerospace Engineering

Program/Concentration

Engineering Mechanics

Committee Director

R. Prabhakaran

Committee Director

J. C. Newman, Jr.

Committee Member

S. G. Cupschalk

Call Number for Print

Special Collections; LD4331.E57B76

Abstract

A 38 inch diameter hot pressed beryllium telescope mirror was analyzed for structural integrity using finite-element modeling and a fracture mechanics analysis program, ZIP3D, developed for three-dimensional (3-0) solid and cracked bodies. The calculation of stress and mixed-mode fracture mechanics parameters for the mirror critical stress area was the objective of the mirror analysis.

Finite-element modeling for ZIP3D solution was performed in two stages. The first stage modeling modeled the mirror configuration on a global basis for calculation of accurate nodal displacements. The second stage modeling reduced the modeled mirror configuration to a set of localized models for calculation of accurate mirror stress concentration , and more importantly, fracture mechanics parameters.

Three global model mesh configurations were analyzed to determine convergence of nodal displacement output. One local model mesh was analyzed to determine maximum stress concentration response. Three localized models containing a crack at different orientations were analyzed to determine the maximum total strain-energy-release rate, Gr, and J-integral response.

Input parameters to the mirror finite-element analysis were based on the expected applied loading, assembly induced preload, and the physical condition of the mirror.

Analysis results for the local stress concentration model indicate that no failure is expected to occur from stress concentration effects. Analysis results for the three local crack models indicate that no fracture is expected to occur. For the three local crack models analyzed, total strain-energy-release rate output was used to calculate effective stress-intensity factors (KEFF) which were well below the lower bound beryllium material Mode I fracture toughness limit.

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DOI

10.25777/zmbz-bb33

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