In Chapter I, metallographic evidence of the existence of the surface layer is given. Using etch-pit techniques on an iron-silicon alloy, it is shown that the dislocation concentration of strained specimens decreases away from the surface. In Chapter II, a relationship is given between the surface-layer stress and fatigue failure. When surface-layer stress attains a critical value, the specimens fracture. An excellent correlation is reported between the life predicted from surface-layer stress data and fatigue life found experimentally. In Chapter III, surface-layer stress at the root of notches is reported. The surface-layer stress was found to increase rapidly as the stress concentration increased. In Chapter IV, the crack propagation rate for an iron-silicon alloy is reported. The crack propagation rate under plane stress conditions decreased in specimens given the SLE treatment. An examination of the surfaces showed that the dislocation concentration was much lower in the SLE-treated sample than in the untreated specimens. Chapter V reports an unsuccessful attempt to detect slip-line formation and strain under sustained loads up to 500 hr. It is believed that greater measurements sensitivity is required for successful detection.

  • Corporate Authors:

    Army Materials and Mechanics Research Center

    Watertown, MA  United States  02172
  • Authors:
    • Kramer, I R
    • Kumar, A Senthil
    • Balasubramanian, N
  • Publication Date: 1972-7

Media Info

  • Features: References;
  • Pagination: 67 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00041363
  • Record Type: Publication
  • Source Agency: Ship Structure Committee
  • Report/Paper Numbers: AMMRC CR 71-2/4
  • Contract Numbers: DAAG 46-70-C-0102
  • Files: TRIS
  • Created Date: Mar 2 1973 12:00AM