Accession Number:

AD0687415

Title:

FRACTOGRAPHIC AND THERMAL ANALYSES OF SHOCKED ALUMINA

Descriptive Note:

Technical rept.

Corporate Author:

NORTH CAROLINA STATE UNIV AT RALEIGH

Report Date:

1969-04-01

Pagination or Media Count:

108.0

Abstract:

This report is concerned with energy absorption processes in ceramic materials exposed to highly dynamic strains capable of causing fracture. Optical and electron fractographic analyses, and direct transmission electron microscopy, were employed in characterizing fracture in ballistically damaged sapphire single crystals and alumina ceramics. Impact fractures were compared with slow break fractures in bars cut from large polycrystalline fragments. Using electron microscopic and dynamic differential calorimetry techniques, explosively shocked alumina particulate also have been examined for evidences of residual strain and annealable excess energy. The findings produced many mutually supporting evidences of local plastic deformation and energy absorption associated with fracture processes in aluminum oxide ceramics and sapphire single crystals. Microscopic evidences from replication fracography, and particularly from direct transmission electron microscopy, strongly support the concept of localized plastic deformation processes associated with fracture. Exothermic energy releases observed during heating of explosively shocked materials over the range 800 - 1200C were estimated at least 14.6 calg.

Subject Categories:

  • Ceramics, Refractories and Glass
  • Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE