A semi-quantitative model of pop-in behavior

Tough maraging steel fibers were embedded in a relatively brittle maraging steel matrix by a special diffusion bonding and heat treating technique. Three indices of fracture toughness were computed. KIc as recommended by the ASTM, Komax, the fracture toughness based on the maximum load and initial crack length and Kimax, the fracture toughness based on the maximum load and instantaneous crack length. While KIc for the fibrous composite was no higher than KIc for the matrix material, both Komax and Kimax were significantly higher for the composite. Since fracture of the fibrous composites occurred in a stable manner (fast fracture was not observed) the load displacement records were converted into crack growth resistance curves. The R curves exhibited a serration at GIc, but continued to increase significantly above GIc and multiple serrations, apparently as a result of the fibers, were present. An approximate calculation shows that the increase in crack growth resistance cannot be attributed solely to plastic deformation of the fibers. Scanning electron microscopy revealed local decohesion between the fibers and the matrix and the character of the R curve was attributed to local crack front pinning by blunting or reduction in constraint. As a model of delamination in a fibrous structure, holes were drilled perpendicular to the parting plane in 7075-T6 aluminum specimens. The load versus displacement and R curves were similar to those observed in the fibrous composites. In addition, pinning of the fatigue crack was observed in the vicinity of the holes.

show abstract

Fracture Toughness of Duplex Structures: Part II — Laminates in the Divider Orientation

Antolovich

Kasi

Chanani

1972

Fracture Toughness: Part II

View full text Add to dashboard Cite

Laminates containing 25 percent of tough (unaged) maraging steel plates and 75 percent of brittle (aged) maraging steel plates were prepared by a special diffusion bonding and heat treating technique so that the thickness of the tough constituent was either 0.02, 0.04, 0.06, or 0.08 in. Compact tension fracture toughness specimens were machined so that the laminates were parallel to the sides of the specimens. They were then fractured according to the recommendations of the ASTM and three indices of toughness were measured: KIc, as recommended by the ASTM, Komax based on the maximum load and original crack length and Kimax, based on the maximum load and instantaneous crack length. Four tests were performed at each thickness of the tough constituent; two each at crack lengths of approximately 0.30 and 0.55 in. The plane-strain fracture toughness of the laminates was slightly higher than KIc of the monolithic brittle constituent and was independent of either crack length or the dimensions of the tough constituent. Regardless of the thickness of the tough phase the composite toughness was highest for specimens containing cracks 0.30 in. long when the throughness was measured in terms of Komax or Kimax. The thoughnessas a function of thickness exhibited a relative maximum when the tough phase was 0.04 in. thick and a relative minimum when the tough phase was 0.06 in. thick for both the 0-30 and 0.55-in. crack lengths. The experimental results are in broad agreement with a proposed model for crack extension in the divider orientation.

show abstract

A semi-quantitative model of pop-in behavior

Abstract: The cOr.1plex material behavior associated wi t'Y-.

Cited by 3 publications

References 5 publications

Fatigue crack propagation in iron and two iron binary alloys at low temperatures

Fatigue crack propagation in iron and two iron binary alloys at low temperatures

Fracture Toughness of Duplex Structures: Part I — Tough Fibers in a Brittle Matrix

Fracture Toughness of Duplex Structures: Part II — Laminates in the Divider Orientation

Contact Info

Product

Resources

About