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    Influence of Specimen Geometry on the Random Load Fatigue Crack Growth

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    The aim of this study was to evaluate and compare, using linear elastic fracture mechanics (LEFM), the fatigue behavior of a low alloy steel using compact-type and surface-crack bend specimens at constant amplitude and random loading. The material tested is relevant to offshore oil platforms and other large structures. It was found that the crack growth rate in the compact type specimens was substantially higher than in surface crack bend specimens. The crack growth results under constant amplitude loading showed a small mean-stress effect. There was much greater effect of mean stress on crack propagation results under random loading than under constant-amplitude. The triple-peaked spectrum signal produced faster growth rate results compared with the other two signals. The random-load crack-growth results were faster in the steady-state (regime II) than in constant amplitude loading. The results suggest that the use of data from constant amplitude tests do not necessarily reflect fatigue crack growth rates data from random loading particularly where there are changes also involved in geometry, thickness, R-ratio, mean load, frequency and material condition.


    random fatigue, compact type specimens, surface crack bend specimens, LEFM, crack growth rates, geometries of fatigue specimens, plastic zones, power-spectrum shapes

    Author Information:

    Radon, JC
    Imperial College, London,

    Nikbin, K
    Imperial College, London,

    Committee/Subcommittee: E08.07

    DOI: 10.1520/STP10585S