Accession Number:

AD0256121

Title:

THE MICROMECHANISM OF BRITTLE FAILURE IN STEEL

Descriptive Note:

Corporate Author:

FOREIGN TECHNOLOGY DIV WRIGHT-PATTERSON AFB OHIO

Personal Author(s):

Report Date:

1960-11-03

Pagination or Media Count:

1.0

Abstract:

Study was made of the micromechanism of brittle failure of low carbon steels. Individual stages were studied of brittle failure during impact bending of prismatic specimens, 10 x 10 x 55, with standard notches and V-notches 2.0 mm deep and having a base radius of 0.25 mm. The specimens were made of steel A open-hearth steel MST-3 in a post-heat-treatment state heated at 1100 degrees for 1.5 hr and cooled in the furnace, steel B ordinary hot-rolled Bessemer steel, brand B steel 3, 18 mm thick, and steel C forged technical iron ingots, 16 mm thick. The process of brittle failure may be represented as follows As a result of the load applied, some of the most favorably oriented grains break down into finer grains blocks, and deformation occurs as a result of the movement of these finer grains within the limits of the initial grain, thus causing a change in the general form of the grain. This, in turn, causes the initial grains to shift with respect to each other along the boundary between them. A temperature reduction and an increase in the deformation rate cause the shear strength along the boundary to increase, which, in turn, increases the stress necessary for the shifting of one grain with respect to another. As a result of the difficulty of the process of plastic deformation, favorable conditions for twinning and formation of microcracks are created by the rotation of the grains. Author

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Distribution Statement:

APPROVED FOR PUBLIC RELEASE