Influence of precatastrophic extension and other effects on local stresses in cracked plates under bending fields

Using the technique of stress freezing and slicing, a set of photoelastic experiments was conducted on plates, each containing a single through internal crack in a remote cylindrical bending field, where each crack suffered precatastrophic extension on the tensile side of the plate as well as closure on the compression side. Resulting stresses were compared with the Sih-Hartranft theory. Results indicate substantial stress relaxation near the tensile side of the plate due to precatastrophic extension. It is concluded that: (1) the Sih-Hartranft theory may be used to estimate local elastic stresses on the tensile side of the plate even when closure and precatastrophic extension occur; (2) complex coupling of closure and precatastrophic extension effects preclude the use of simple correction factors for existing mathematical models except for relatively small precatastrophic extension.