STP821

    Use of a Load-Pulsing Technique to Determine Stress Corrosion Crack Velocity

    Published: Jan 1984


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    Abstract

    A load-pulsing technique has been used to determine the velocity of transgranular stress-corrosion cracks in Admiralty Metal tested in a 15N aqueous ammoniacal solution. In this technique, small load pulses are periodically superimposed onto an otherwise constant tensile load during crack propagation, producing markings on the fracture surfaces which delineate the positions of the crack front. The spacing between crack-front markings (Δx) was measured for values of the time interval between pulses (Δt) in the range 2 to 500 s. A one-to-one correspondence was observed between pulses and markings in this range, so that the crack velocity was given by Δxt. The velocity was found to be constant over much of the crack length for each value of Δt, indicating that an extensive Stage II region exists in this system. The Stage II velocity was constant: 1.9 × 10−7 m s−1 for values of Δt greater than 100 s; this value of velocity is approximately five times larger than those obtained by conventional methods, and this difference is attributed to the influence of grain boundaries in the latter case. The Stage II velocity increased with decreasing Δt for Δt < 100 s, and this is attributed to fatigue effects. It is concluded that the load-pulsing method can provide a convenient and reliable technique for the determination of Stage II velocities for transgranular stress-corrosion cracking.

    Keywords:

    Admiralty Metal, fractography, stress corrosion cracking, stress corrosion crack velocity


    Author Information:

    Slattery, PW
    National Bureau of Standards, Gaithersburg, Md.

    Smit, J
    National Bureau of Standards, Gaithersburg, Md.

    Pugh, EN
    National Bureau of Standards, Gaithersburg, Md.


    Paper ID: STP34445S

    Committee/Subcommittee: G01.06

    DOI: 10.1520/STP34445S


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