EXPERIMENTAL DETERMINATION OF PLASTIC CONSTRAINT AHEAD OF A SHARP CRACK UNDER PLANE-STRAIN CONDITIONS

An experimental method of identifying the plastic constraint ahead of a sharp crack loaded under plane-strain conditions is proposed. The method is based on the idea that the cleavage stress--which can be measured with unnotched bars--is the peak stress developed ahead of a crack just prior to crack extension. Ways of calculating the strain, strain rate, and yield stress appropriate for the plastic region just ahead of the crack are developed. The ratio of the cleavage stress to the local yield stress identifies the plastic constraint factor at the stress level corresponding to crack extension. Experimental results recently reported by Krafft are shown to be consistent with this interpretation. With these data, the following expression for p.c.f., the plastic constraint factor, is deduced: p.c.f. = 1+2 K/Y, where Y is the yield stress, K the stress intensity parameter, and the numerical constant, 2, has the dimensions inches -1/2. This result offers a way of formulating K sub Ic, the fracture toughness for crack extension by cleavage, in more basic terms and sheds some light on the metallurgical origins of K sub Ic.

• Corporate Authors:

  Ship Structure Committee

  National Academy of Science, 2101 Constitution Avenue, NW
  Washington, DC  United States  20418
• Authors:
  • Hahn, G T
  • Rosenfield, A R
• Publication Date: 1966-5-1

Media Info

• Features: References;
• Pagination: 12 p.

Subject/Index Terms

• TRT Terms: Cracking; Fracture properties; Plastic analysis; Structural analysis
• Identifier Terms: Ship Structure Committee
• Uncontrolled Terms: Crack propagation
• Old TRIS Terms: Plane strain fracture toughness test
• Subject Areas: Marine Transportation; Materials;

Filing Info

• Accession Number: 00164221
• Record Type: Publication
• Source Agency: Ship Structure Committee
• Report/Paper Numbers: SSC-180
• Contract Numbers: NObs-92383
• Files: TRIS
• Created Date: Oct 29 1977 12:00AM