Accession Number : AD0761148

Title :   Ligament Instability Model for Stress Corrosion and Fatigue Crack Propagation in a 4340 Steel.

Descriptive Note : Interim rept.,

Corporate Author : NAVAL RESEARCH LAB WASHINGTON D C

Personal Author(s) : Krafft,Joseph M. ; Smith,Herschel L.

Report Date : APR 1973

Pagination or Media Count : 47

Abstract : The model is one which explains the growth of cracks in terms of the economics of maintaining stability of plastic flow at the crack tip. The material there is taken to be subdivided into tensile elements, units of size d sub T. There instability is induced by corrosion by stress relaxation, by contraction in area due to stretching; their stability is restored by strain hardening, but this requires strain and this, at constant load, crack growth. The model is tested in terms of data on the aqueous stress corrosion cracking and corrosion fatigue crack propagation in an AISI 4340 steel, quenched and tempered back at 204, 316, 427 and 538C. Data from the literature on another 4340 and on A533 B-1 pressure vessel steel is also examined. Tensile as well as cyclic stress-strain curves were analyzed for each material. (Modified author abstract)

Descriptors :   (*STEEL, *STRESS CORROSION), FATIGUE(MECHANICS), CRACKS, CRACK PROPAGATION, TENSILE PROPERTIES, CREEP, CORROSION, MATHEMATICAL MODELS

Subject Categories : Properties of Metals and Alloys

Distribution Statement : APPROVED FOR PUBLIC RELEASE