This paper studies the strength of inplane and antiplane stress singularities near the apex of a structure formed from the dental restoration of premolar class II cavity. In order to exclude the probability of failure, it is necessary to find the conditions such that singularity orders are kept to a minimum or inplane and antiplane stress fields are non-singular.The effects of enamel anisotropy on the stress singularities are emphasized at two critical positions in the restoration structure: (1) the apex of the enamel and restoration interface, and (2) the apex of the enamel, dentine and restoration junction. In the second case, the interface between the restoration and enamel may be bonded or debonded. The results of this paper show that the recommended cutting angles are strongly affected by the ratio R of transverse stiffness to the longitudinal stiffness. Besides, if the stiffness of the restoration material is close to the transverse stiffness of the enamel, the singularity orders will be reduced. The results of previous studies, in which the enamel is considered to be isotropic, should be modified.

Leak-before-break (LBB) assessment of nuclear piping involves ductile fracture analysis of pipes or elbows with postulated through-wall cracks. Due to the fact that the crown part of an elbow is one of the positions that crack initiation occurs in most frequently, the calculation of J-integrals to investigate fracture behavior are important research topics. This paper proposes a 3-D finite element model of an elbow embedded with an axial through-wall crack to estimate the J-integral parameters under bending moment. The J-integral values can be calculated by using ABAQUS and taking into account the effects of geometrical and model of material in non-linear analysis. The results show that the non-linear deformation and contact condition of crack surfaces play important roles for the J-integral values. In addition, the J values estimated by the proposed model are more conservative and realistic than previous studies.