Title page for ETD etd-4614156097150


Type of Document Master's Thesis
Author Medding, Jonathan A.
URN etd-4614156097150
Title Nondestructive Evaluation of Zirconium Phosphate Bonded Silicon Nitride Radomes
Degree Master of Science
Department Materials Science and Engineering
Advisory Committee
Advisor Name Title
Henneke, Edmund G. II
Kampe, Stephen L.
Duke, John C. Jr. Committee Chair
Keywords
  • silicon nitride
  • ultrasonic
  • NDE
  • radome
  • porosity
Date of Defense 1996-12-17
Availability unrestricted
Abstract

The performance advances of radar-guided

missiles have created a need for radome

materials with improved strength, toughness,

and thermal shock capabilities. Zirconium

phosphate bonded silicon nitride (Zr-PBSN),

which has a low and thermally stable dielectric

constant, high rain erosion resistance and a

low-cost processing method, has been

developed for radome applications in

advanced tactical missiles. Pressureless

sintering reduces processing costs, but is

untried for radome manufacturing. The

tendency for catastrophic failure requires that

each radome fabricated with this

material/method be inspected for defects prior

to use. Visible, thermographic and ultrasonic

nondestructive evaluation (NDE) methods

have been tested with Zr-PBSN discs

containing fabricated flaws likely to be present

in a radome.

Ultrasonic C-scanning using a 0.25" diameter,

15 MHz focused transducer with a pulse-echo

configuration was clearly superior at detecting

cracks, delaminations, impurities, voids and

porosity variation. A method for determining

local porosity via the longitudinal elastic wave

velocity was developed and can be

incorporated into an ultrasonic scanning

system. A system that uses a computer to

perform all motion control, data acquisition,

and data manipulation, but requiring a skilled

operator for scan setup and interpretation of

the data has been proposed.

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