The influence of discontinuity and orthotropy of fracture toughness on conditions of fracture initiation in singular stress concentrators

This paper deals with assessment of conditions of fracture initiation in singular stress concentrations that are modeled by a bi-material notch composed of two orthotropic materials. Within the assessment of the stress concentrators, the stability criteria based on standard linear elastic fracture mechanics can lead to incorrect results due to discontinuity and orthotropy of fracture toughness. Procedures in literature suggested for assessing the critical applied loading and fracture initiation direction usually consider only the change of elastic constants of the material and do not consider the change of fracture toughness. The stability criterion considering fracture toughness dependent on the direction of presupposed fracture initiation is shown in the paper. It is concluded that the criterion of this kind can qualitatively and quantitatively influence the estimated fracture initiation conditions, and it contributes to more reliable assessment of components with geometrical and/or material discontinuity.