Definition of Crack Tip Opening Displacement |

There are two common definitions of the crack tip opening displacement (CTOD): 1. The opening displacement of the original crack tip. 2. The displacement at the intersection of a 90° vertex with the crack flanks. These two definitions are equivalent if the crack blunts in a semicircle. |

CTOD in Specimen |

The crack tip opening displacement (CTOD) of a crack at the edge of a three-point bending specimen is shown below: where CTOD where is a dimensionless rotational factor used to locate the center of the hinge. For simplicity, let's assume that the center of the hinge locates at the center of The above hinge model may not be accurate when the displacement is mostly elastic. A more accurate approach is to separate the CTOD into an elastic part and a plastic part: where is the small scale yielding stress and |

Relationship between J and CTOD |

Consider a linear elastic body containing a crack, the J integral and the crack tip opening displacement (CTOD) have the following relationship where and Shih, C. F., 1981, took a step further and showed that a unique relationship exists between J and CTOD beyond the validity limits of LEFM. He introduced the 90° intercept definition of CTOD, as illustrated below. The displacement field is The CTOD is evaluated from u at _{y}r = r and :
^{*}Since The CTOD becomes |