Accession Number:

AD0603214

Title:

EXHAUSTION OF DUCTILITY AND BRITTLE FRACTURE OF E-STEEL CAUSED BY PRESTRAIN AND AGING.

Descriptive Note:

Progress rept. no. 2,

Corporate Author:

BROWN UNIV PROVIDENCE R I

Personal Author(s):

Report Date:

1964-07-01

Pagination or Media Count:

43.0

Abstract:

The investigation of static brittle fracture initiation in engineering structures requires first the establishment of a criterion of brittle behavior of the structure as a whole. Such a criterion is obtained by a comparison of the fracture load with the flow limit of an idealized perfectly plastic material. The difference between static fractures at high and low load was related to the magnitude of the plastic strains at regions of strain concentration and to the ductility of the steel. It was found that the ductility depends on the whole history of strain and temperature and is suddenly and drastically exhausted by cold straining of a closely determined amount, and far more easily by straining at about 500 F. This led to the first systematic static brittle fracture initiation of unwelded steel plates at low average net stress, as low as 10 of yield. The ductility of cold strained steel is restored by a heat treatment at about 1100 F or higher. The required duration of heat treatment is shorter for hot than for cold-strained bars and appears to increase with the amount of prestrain, and to decrease when the temperature is raised. A better understanding of the mechanism of fracture initiation makes it now possible to express qualitative macroscopic criteria of fracture based on the strain hardening law and the ductility of embrittled steel and on the strain and stress distribution at a sharp notch in such material. Author

Subject Categories:

Distribution Statement:

APPROVED FOR PUBLIC RELEASE