Accession Number : ADA191485

Title :   Role of Cracks in the Creep of Structural Polycrystalline Ceramics.

Descriptive Note : Final rept. 15 Apr 85-30 Sep 87,

Corporate Author : VIRGINIA POLYTECHNIC INST AND STATE UNIV BLACKSBURG DEPT OF MATERIALS ENGINEE RING

Personal Author(s) : Hasselman, D P ; Donaldson, Kimberly Y ; Venkateswaran, Anuradha

PDF Url : ADA191485

Report Date : 15 Jan 1988

Pagination or Media Count : 122

Abstract : A study was conducted of the role of crack formation in the non-linear stress-strain behavior of a fine-grained polycrystalline aluminum oxide at high temperature under conditions of displacement-rate-controlled mechanical loading. The observed deformation behavior could be divided into three regimes. At the lowest values of deformation rate the load levelled off to a constant value without crack formation, consistent with deformation by diffusional creep. Over a range of intermediate values of deformation considerable non-linear deformation took place, manifested by a decrease in stress with increasing strain as the result of strain-softening due to the formation and growth of cracks. At the highest rates of displacement, specimen fracture occurred by the formation of a single crack without significant non-linear deformation and without the formation of additional cracks. These results are discussed in terms of the general mechanisms and kinetics of the deformation of non-ductile solids. Keywords: Crack propagation; Cracking; Ceramics; Aluminum; Crystal lattices; Composite materials.

Descriptors :   *CERAMIC MATERIALS, *DEFORMATION, *POLYCRYSTALLINE, *ALUMINUM OXIDES, ALUMINUM, COMPOSITE MATERIALS, CRACK PROPAGATION, CRACKS, CREEP, CRYSTAL LATTICES, DISPLACEMENT, STRESS STRAIN RELATIONS, GRAIN BOUNDARIES, MICROCRACKING, FAILURE(MECHANICS), PHOTOMICROGRAPHY

Subject Categories : Ceramics, Refractories and Glass
      Inorganic Chemistry

Distribution Statement : APPROVED FOR PUBLIC RELEASE