Accession Number : AD0637143

Title :   EXHAUSTION OF DUCTILITY UNDER NOTCH CONSTRAINT FOLLOWING UNIFORM PRESTRAINING.

Descriptive Note : Progress rept. no. 5.

Corporate Author : BROWN UNIV PROVIDENCE R I

Personal Author(s) : Mylonas,C. ; Kobayashi,S. ; Armenakas,A.

Report Date : AUG 1966

Pagination or Media Count : 50

Abstract : The purpose of the work was to measure the amount of uniform precompression of ABS-B and Project E-steel resulting in brittle fracture under the stron constraint of a subsequently machined severe circumferential groove. The elongation at the shoulders, measured with a special extensometer, was found to be a far more sensitive measure of brittleness than the average fracture stress. Prestrains as low as 0.05 caused a reduction of the elongation at the shoulders from about 0.017 - 0.050 in. to about 0.003 - 0.006 in. At low prestrains average fracture stress equaled or exceeded the theoretical flow limit of 2.68 sigma 0.1, where sigma 0.1 is the 0.1% offset yield stress in simple tension at the same prestrain. At a prestrain of 0.20 the fracture stress fell below the flow limit and at 0.60 it was close to sigma 0.1. The conditions of fracture at a notch in a strain hardening material are discussed. The total plastic elongation of a region surrounding a sharp notch in prestrained steel determines whether or not fracture will be initiated in large structures, hence is a direct and realistic measure of the remaining ductility and provides an excellent test of the material's resistance to embrittlement. (Author)

Descriptors :   (*STEEL, DUCTILITY), (*FRACTURE(MECHANICS), STEEL), BRITTLENESS, STRAIN(MECHANICS), STRESSES, NOTCH SENSITIVITY, LOADS(FORCES), RODS, COLD WORKING, AGING(MATERIALS)

Subject Categories : Metallurgy and Metallography

Distribution Statement : APPROVED FOR PUBLIC RELEASE