SEDL / STP / STP536-EB / STP49641S

Effect of a Loading Sequence on Threshold Stress Intensity Determination

Harrigan, W. C.
Members of the Technical Staff, The Aerospace Corporation, Los Angeles, Calif.

Dull, D. L.
Members of the Technical Staff, The Aerospace Corporation, Los Angeles, Calif.

Raymond, L.
Members of the Technical Staff, The Aerospace Corporation, Los Angeles, Calif.

Pages: 11    Published: Jan 1973

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Abstract

The effect of a loading sequence on the stress corrosion cracking of AISI 4340 steel and Ladish D6AC steel in an aqueous environment has been studied with double-cantilever beam specimens. The loading sequence was found to influence an incubation time period for the initiation of crack propagation as the stress intensity (K) changed. When the stress intensity was decreased during stress-corrosion testing, the incubation time was dependent upon the change in stress intensity and the final stress intensity (Kf). When the stress intensity was increased, an incubation time was not found. However, the loading sequence did not influence the steady-state crack growth rates. The loading sequence effect is shown to cause interpretation problems when specific time periods are used for the determination of the threshold stress intensity (KIscc), especially after the specimens have been prestressed.