Accession Number : AD0473496

Title :   MICRO- AND MACROCRACK FORMATION.

Descriptive Note : Progress rept. no. 7,

Corporate Author : MASSACHUSETTS INST OF TECH CAMBRIDGE

Personal Author(s) : Averbach, B. L.

Report Date : OCT 1965

Pagination or Media Count : 30

Abstract : The formation of cleavage microcracks with a length of the order of one grain diameter is considered to be the initial step in fracture. It is assumed that the stress concentration required for cleavage is supplied by thick slip or twin bands, and the critical width of these yield bands is calculated. For example, in iron with a grain radius of 0.01 cm, the critical slip band width is 0.00002 cm, and this value is compatible with observations in the vicinity of microcracks. The second stage of crack formation involves the simicontinuous propagation of microcracks to form unstable macroscopic cracks. Work is required to extend the initial microcracks, and this incremental work is used to calculate the crack-extension force, G sub c, which is required in linear fracture mechanics. (Author)

Descriptors :   *IRON), (*FRACTURE(MECHANICS), (*STEEL, FRACTURE(MECHANICS)), CRYSTAL DEFECTS, SINGLE CRYSTALS, GRAIN BOUNDARIES, GRAIN STRUCTURES(METALLURGY), METAL CRYSTALS, TRANSITION TEMPERATURE.

Distribution Statement : APPROVED FOR PUBLIC RELEASE