This paper describes scanning electron-microscope studies made in an attempt to resolve current confusion in the literature about how fatigue cracks begin. It has been said that they normally grow by a Stage I process of shear, on the grounds that they form along slip bands, which are known to tend to directions of maximum shear. It is found that in fact cracks started by slip do not necessarily follow the Stage I shear rule, but may follow random paths; and that optimum condition for Stage I cracking is indeed absence of slip. Further, it is shown that much of the confusion disappears if a distinction is made between "plastic" metals, in which cracking is started rather by local inhomogeneous strains and internal stresses and may have little to do with slip.

  • Corporate Authors:

    George Washington Transportation Research Institute. Center for Intelligent Systems Research

  • Authors:
    • Gilmore, C M
    • MacDonald, D E
    • Wood, W A
  • Publication Date: 1972-7

Media Info

  • Features: References;
  • Pagination: 17 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00041383
  • Record Type: Publication
  • Source Agency: Ship Structure Committee
  • Report/Paper Numbers: 12 Tech Rpt
  • Contract Numbers: N00014-67-A-02140011
  • Files: TRIS
  • Created Date: Mar 2 1973 12:00AM