Three-dimensional theoretical and experimental researches on quarter circular corner cracks in finite bodies

The corner crack is a typical crack widely existing in three-dimensional(3D) structures, especially for the quarter circular corner crack. For a curved 3D crack such as the corner crack, the fracture prediction results will usually be imprecise if the plane-strain fracture criterion is used. In order to improve the accuracy of fracture prediction, a 3D fracture prediction method induced a new T _z -based equivalent thickness model is adopted to deal with the fracture strength for a circular corner crack in a finite body. It is found that the strongest T _z constraint plane will shift far from the mid-plane (45° normal plane along the crack front line) with increasing c/W (ratio of crack depth c to plate width W ) in finite bodies. Based on systematic finite element analyses, a new equivalent thickness equation for the circular corner crack in a finite body is obtained. A new stress intensity factor equation is developed based on the Newman's equation, the upper limit of the c/W is extended from 0.2 to 0.95. In order to verify the 3D fracture prediction method, a new fracture test on the circular corner crack is conducted. The experimental results show that the new 3D method is more accurate than the traditional 2D fracture criterion. For a given specimen with a circular corner crack, the prediction error decreases from 35.3–2.2% under tensile loading.