CRACK INITIATION IN FATIGUE OF METALS.
Final scientific rept.,
ENGINEERING MECHANICS RESEARCH LAB UNIV OF TEXAS AUSTIN
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The origin and progressive growth of the fatigue crack on the surface of single and polycrystalline face centered cubic metals subjected to cyclic deformation were observed with an electron microscope. Unique features of the investigation were the successive examination of a selected area on the surface of a specimen and the selection of crystal orientation so that the active slip system and the Burgers vectors of the contributing dislocations could be more accurately defined. Fatigue damage was observed to begin as a sequence of small cavities oriented on the slip traces, which increase in number and size, ultimately joining to form either a continuous microcrack or shallow surface intrusion. Variation of temperature 4.2K to 300K, stress amplitude, and number of active slip systems does not change the basic process of crack initiation, but only the rate and mode of cavity coalescence. A tentative explanation of the mechanism of fatigue is proposed based on this work and other previous investigations. Author
- Metallurgy and Metallography