Journal Published Online: 01 September 1999
Volume 27, Issue 5

Effect of Crack Front Curvature and Side Grooving on CTOD δ and -Integral in CT and 3PB Specimens

CODEN: JTEVAB

Abstract

Fracture testing on compact tension (CT) and threepoint bend (3PB) specimens is preceded by fatigue precracking. Fatigue cracks have curved crack fronts. Nevertheless, crack front curvature is not taken into account in numerical modeling of fracture toughness testing procedures. In this paper we analyze actual fatigue cracks in CT specimens and show that the difference between crack depth at the center plane and at the surface of specimens is typically 0.01 to 0.03 of the specimen width. Three-dimensional elastic-plastic finite element analyses were performed for CT and 3PB specimens with crack fronts of different curvatures, and the CTOD δ5 and the J-integral were determined. It is found that the ratio δ5Cδ5 is sensitive to the crack front curvature and strongly affected by side grooves. It is also shown that crack front curvature variations that are within the limits given by the test standards affect to a certain extent the η factor employed for the determination of the experimental value of the J-integral using the area under the force versus load-point displacement record. These facts should be kept in mind when toughness is measured.

Author Information

Nikishkov, GP
Institute of Materials Research, GKSS Research Center, Geesthacht, Germany
Heerens, J
Institute of Materials Research, GKSS Research Center, Geesthacht, Germany
Hellmann, D
Institute of Materials Research, GKSS Research Center, Geesthacht, Germany
Pages: 8
Price: $25.00
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Details
Stock #: JTE12231J
ISSN: 0090-3973
DOI: 10.1520/JTE12231J