Abstract
The growth of very small fatigue microcracks was studied in a powder metallurgy nickel-base superalloy. A novel specimen containing a small crack was used, with crack growth rates being measured optically at high magnification. Interaction between the crack and the material microstructure was observed in a cyclic loading stage within a scanning electron microscope.
It was found that microcracks grew initially at rates more rapid than those corresponding to conventional fracture mechanics (“large crack”) specimens. The rate undergoes a transient decrease with increasing crack length, dropping below the corresponding plot for “large” cracks, before beginning to increase in accordance with “large” crack results, ultimately merging with the latter. These results are discussed in terms of microstructure and crack growth mode, and the findings considered in light of the few studies of cyclic microcrack growth which have previously been correlated with fracture mechanics.
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Lankford, J., Cook, T.S. & Sheldon, G.P. Fatigue microcrack growth in a nickel-base superalloy. Int J Fract 17, 143–155 (1981). https://doi.org/10.1007/BF00053517
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DOI: https://doi.org/10.1007/BF00053517