SYMPOSIA PAPER Published: 01 January 1993

Study of a Crack-Tip Region Under Small-Scale Yielding Conditions


The computer-assisted moire technique was used to measure displacements and strains in the neighborhood of a crack tip. An aluminum 6061-T6 compact tension specimen was utilized to perform the measurements. The u (parallel to the crack direction) and v displacement fields (perpendicular to the crack direction) were determined, as well as the corresponding strains. Tension and fracture tests were performed to obtain the properties of the material. The stress-strain curve was fitted with a Ramberg-Osgood type of constitutive law. The stresses were computed from the strains using a two-dimensional generalization of the Ramberg-Osgood constitutive equation. The J-integral was computed along several paths. Good agreement was found between the KI computed from the J-integral with the KI obtained from the application of the ASTM Test Method for Plane-Strain Fracture Toughness of Metallic Materials (E 399-83) standard polynomial. The HRR solution was compared to the experimental results. Some important conclusions can be obtained: 1. In small-scale yielding, the HRR field can only be observed very close to the crack tip. 2. The region dominated by the HRR field is only a few crystalline grains in size. 3. The HRR field models the radial stresses very poorly but gives a good estimate of the tangential stresses. 4. The experimental results support the view point that in small-scale yielding, the J-dominance is independent of the validity of the HRR solution.

Author Information

Sciammarella, CA
Experimental Mechanics of Materials Laboratory, Illinois Institute of Technology, Chicago, IL
Albertazzi, A
University Federal de Santa Catarina, Brazil
Mourikes, J
Illinois Institute of Technology, Chicago, IL
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Developed by Committee: E08
Pages: 344–364
DOI: 10.1520/STP24277S
ISBN-EB: 978-0-8031-5241-0
ISBN-13: 978-0-8031-1867-6