STP1114

    Fracture Toughness and Fatigue Crack Initiation Tests of Welded Precipitation-Hardening Stainless Steel

    Published: Jan 1991


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    Abstract

    An analysis is described of a welded stainless steel box beam that experienced a structural failure during fatigue testing. Cracks initiated at notches caused by partial penetration welds and grew to a length of several centimetres in about 1000 load cycles.

    The objective here is to describe the characterization of fracture toughness and fatigue crack initiation for the precipitation-hardening stainless steels used for the welds and parent plate of the beam. Three-point bend specimens were used to measure both fatigue crack initiation life and the J-integral fracture toughness of the parent plate and weld metal in various conditions. The notch fatigue analysis method of Barsom and Rolfe was used to analyze the crack initiation test results. The crack was grown further, side notches were added, and JIc tests were performed using ASTM Test Method for JIc, a Measure of Fracture Toughness (E 813-87) with a modified load-line-displacement unloading-compliance procedure to measure crack growth.

    Conclusions drawn from the work include the following: (a) JIc can be accurately determined with a three-point bend test using load-line displacement to measure crack growth by unloading compliance (An accurate expression for a/W in terms of load-line displacement was developed.); and (b) fatigue crack initiation life and JIc fracture toughness of stainless steels in various conditions were characterized. The welded and aged condition, with no intermediate solution treatment, showed unstable, cleavage-type fracture and resulted in a low JIc value and a short initiation life.

    Keywords:

    elastic-plastic fracture, test methods, fracture toughness, J, -integral, welds, stainless steels, fatigue initiation, unloading compliance


    Author Information:

    Underwood, JH
    Research engineer, mechanical engineer, mechanical engineer, mechanical engineering technician, and mechanical engineer, Army Armament RD&E Center, Watervliet, NY

    Farrara, RA
    Research engineer, mechanical engineer, mechanical engineer, mechanical engineering technician, and mechanical engineer, Army Armament RD&E Center, Watervliet, NY

    O'Hara, GP
    Research engineer, mechanical engineer, mechanical engineer, mechanical engineering technician, and mechanical engineer, Army Armament RD&E Center, Watervliet, NY

    Zalinka, JJ
    Research engineer, mechanical engineer, mechanical engineer, mechanical engineering technician, and mechanical engineer, Army Armament RD&E Center, Watervliet, NY

    Senick, JR
    Research engineer, mechanical engineer, mechanical engineer, mechanical engineering technician, and mechanical engineer, Army Armament RD&E Center, Watervliet, NY


    Paper ID: STP16855S

    Committee/Subcommittee: E08.08

    DOI: 10.1520/STP16855S


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