BRITTLE FRACTURE PROPAGATION STUDIES
This investigation was undertaken to study low-velocity brittle fracture in wide steel plates. The detailed results of two tests of 6-ft-wide prestressed steel plates are presented along with pertinent observations from tests of similar specimens conducted as one of the last phases of Project SR-137. Also, results of nineteen tests of 2-ft-wide centrally notched plates, a majority of which had a longitudinal butt weld are presented. In 6-ft-wide prestressed plates, the residual stress field (longitudinal tensile stresses at the edges of the plate balanced by compressive stresses throughout the central portion) made initiation possible with no external applied stress, and had a significant effect on the fracture propagation. Fracture speeds were high (4000-6000 fps) near the edges of the plates and decreased rapidly to as low as 165 fps as the fracture propagated into the region of compressive stresses. In the low-speed regions the magnitude and extent of the dynamic strain field associated with the crack tip was considerably less than had been recorded in earlier tests of high-speed fractures in plain plates. For the 2-ft-wide centrally notched and welded plates in which the fractures were initiated statically, fracture speeds as high as 5000 fps were recorded in the zone of high residual tensile stresses near the weld; the speed apparently stabilized at about 1800 fps after the fractures had propagated out of the high tensile stress field. The dynamic strain field associated with the intermediate-speed fractures (1800 fps) were roughly commensurate with that which would be expected for this fracture-velocity level. The fracture initiation observations indicated that the tensile residual stress alone was not sufficient to insure low-applied-stress fracture initiation; also, metallurgical effects associated with high-heat input during welding are not necessary in all cases for low-stress initiation. Indications are that strain cycling of the material in the notch region arising from welding may play an important role in the initiation of brittle fractures.
University of Illinois, Urbana-ChampaignUrbana, IL United States 61801
Ship Structure CommitteeNational Academy of Science, 2101 Constitution Avenue, NW
Washington, DC United States 20418
- Videon, F F
- Barton, F W
- Hall, W J
- Publication Date: 1963-8-20
- Features: References;
- Pagination: 35 p.
- TRT Terms: Cracking; Fracture mechanics; Metals; Notching (Cutting); Plate bearing test; Repeated loads; Strength of materials
- Identifier Terms: Ship Structure Committee
- Uncontrolled Terms: Crack initiation; Crack propagation; Notch sensitivity
- Old TRIS Terms: Cyclic fatigue
- Subject Areas: Marine Transportation; Materials;
- Accession Number: 00331930
- Record Type: Publication
- Source Agency: Ship Structure Committee
- Report/Paper Numbers: SSC-148 Prog Rpt.
- Contract Numbers: NObs-65790
- Files: TRIS
- Created Date: May 21 1981 12:00AM