FRACTOGRAPHIC AND THERMAL ANALYSES OF SHOCKED ALUMINA
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 cal/g.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 1969
- Accession Number
- AD0687415
Entities
People
- C. E. Zimmer
- C. H. Kim
- D. R. Johnson
- H. Palmour Iii
Organizations
- North Carolina State University