Volume 16, Issue 1 (January 1988)
Load-Point Compliance of a Three-Point Loaded Cracked-Notched Beam
Load-point compliances are determined for several three-point loaded notched-cracked beam configurations utilized by ASTM as standard test specimens. A method of accounting for the crack starter notch configuration as well as the crack itself is presented. Results from this analysis are compared with tabular data included in ASTM Test for JIc. A Measure of Fracture Toughness (E 813-81). Because load-point compliance is a sensitive indicator of crack growth and of general interest, two additional beam test configurations standardized by ASTM are examined: Test for Plane-Strain Fracture Toughness of Metallic Materials (E 399-83) and Test for Crack Strength of Slow Bend, Precracked Charpy Specimens of High-Strength Metallic Materials (E 812-81). These results are also compared with an available method that predicts compliance based on an idealized crack representing a crack starter notch. Results show, where accuracy is required, as specified in ASTM E 813, that the presence of the notch geometry and be considered.
A regression analysis was accomplished to provide convenient formulae that describe load-point compliance and inverse compliance for particular three-point loaded cracked-notched beams as specified in ASTM E 813, E 399, and E 812. These expressions should be useful for fracture testing including fatigue crack growth rate measurements.