EXHAUSTION OF DUCTILITY UNDER NOTCH CONSTRAINT FOLLOWING UNIFORM PRESTRAINING

Earlier studies of reduction of ductility by prestraining have been extended to include behavior under severe notch constraint of uniformly prestrained and aged ABS-B and Project E-Steel. Tension bars with deep circumferential grooves of 20 deg angle and 0.030 or 0.010 or 0.003 in. notch radius were used. The depth of the grooves was sufficient to enable the more ductile bars to reach and exceed the theoretical flow limit for infinite depth based on the 0.1% offset yield stress sigma sub 0.1. Both load and elongation at the groove shoulders were measured. The average fracture stress increased with increasing prestrain at first at both the same rate as the sigma sub 0.1 stress and the corresponding flow limit and then at a slower rate, so that at a prestrain of 0.20 it was clearly below the corresponding flow limit. From there on the fracture stress gradually decreased till at 0.60 prestrain it was close to the 0.1% offset yield stress of unnotched bars. According to the criterion of average fracture stress, the transition from ductile to brittle behavior under the conditions at the notch was very gradual and occurred at prestrains close to 0.20. On the contrary the elongation at the shoulders, which is a direct measure of ductility, showed an abrupt drop at prestrains as low as 0.05, which is a tremendous reduction from the prestrain of 0.75 needed to embrittle smooth bars of ABS-B steel subjected to tension, and of 0.48 when subjected to bending. The conditions of fracture at a notch in a strain hardening material are discussed in relation with the obtained results.

  • Supplemental Notes:
    • Sponsored by the Naval Sea Systems Command, Washington, D.C. 20362.
  • Corporate Authors:

    Ship Structure Committee

    National Academy of Science, 2101 Constitution Avenue, NW
    Washington, DC  USA  20418
  • Authors:
    • Mylonas, C
  • Publication Date: 1965-11

Media Info

  • Features: References;
  • Pagination: 40 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00164226
  • Record Type: Publication
  • Source Agency: Ship Structure Committee
  • Report/Paper Numbers: SSC-173 Tech Rpt.
  • Contract Numbers: NObs-88294
  • Files: TRIS
  • Created Date: Oct 29 1977 12:00AM