BRITTLE-FRACTURE PROPAGATION IN WIDE STEEL PLATES

The experimental phases of the program involved tests of 3/4-in.-thick structural-steel plate specimens, either 2 ft or 6 ft in width. In most cases the plate specimens were stressed uniaxially to about 19,000 psi, cooled to about 0 deg F, and a fracture was started with the notch-wedge-impact method of fracture initiation. Measurements of the strain distribution on the surface of the plate and the crack speed were made as the fracture traversed the plate. Recorded strains generally remained elastic even though the peak magnitudes, in some cases, exceeded 5000 microin./in. The majority of the recorded fracture speeds ranged from 2000 to 4000 fps. For the particular specimen geometry used and associated test conditions, the strain field surrounding the tip of an advancing fracture appears to remain essentially unchanged after traversing about one-third the width of a 6-ft-wide plate. Exploratory studies were also made of the propagation of brittle fractures in prestressed plates. Measured fracture speeds ranged from about 4000 fps in the region of high tensile strain near the initiation edge to as low as 50 fps in the compressive strain region. The intensity of strain in the field associated with the tip of the moving crack diminished as the speed of the fracture decreased. The visual appearance of the future surface was unusually smooth when the crack had run at low velocity, with no evidence of the familiar herringbone pattern. The results indicate clearly that a residual strain field can have a marked effect on the ease of initiation and propagation of a brittle fracture. Analytical studies of plate response were undertaken by representing the plate as a series of initially perpendicular, rigid bars connected at their points of intersection by a deformable node and interconnected at their midpoints by a shear element. Although the grid used was rather coarse, studies with this plate analog indicate that the lattice representation is a promising method of studying plate response during fracture propagation.

• Corporate Authors:

  University of Illinois, Urbana-Champaign

  Urbana, IL  United States  61801

  Ship Structure Committee

  National Academy of Science, 2101 Constitution Avenue, NW
  Washington, DC  United States  20418
• Authors:
  • Hall, W J
  • Rolfe, S T
  • Barton, F W
  • Newmark, N M
• Publication Date: 1961-10-3

Media Info

• Pagination: 30 p.

Subject/Index Terms

• TRT Terms: Cracking; Deformation curve; Fracture mechanics
• Identifier Terms: Ship Structure Committee
• Uncontrolled Terms: Crack propagation
• Subject Areas: Marine Transportation; Materials;

Filing Info

• Accession Number: 00331919
• Record Type: Publication
• Source Agency: Ship Structure Committee
• Report/Paper Numbers: SSC-131 Final Rpt.
• Contract Numbers: NObs-65790, NObs-72046
• Files: TRIS
• Created Date: May 21 1981 12:00AM