Stress Intensity Factor and Shape Coefficient Correction of Non-Penetrating Three-Dimensional Crack for Brittle Ampoule Bottle with V-Shaped Notch

Abstract

The automatic opening of an ampoule bottle is key to making the operation of the sterility inspection automatic. During the automatic opening, the fracture characteristics on the neck of ampoule bottle need to be deeply understood to avoid the contamination of the samples by preventing the glass fragments from dropping into the ampoule bottle. This paper presents the calculation of fracture characteristic parameters, such as the coefficient K of the stress intensity factor (SIF) and the coefficient F of shape factor (shape coefficient), based on the finite element method (FEM) for a non-penetrating three-dimensional crack. Mechanical and mesh models were built for the special structure of an ampoule bottle with a V-shaped notch, and the influence of mesh size on the coefficient K was evaluated. The mathematical expressions of stress intensity factor and shape coefficient of three types of cracks were established. The results demonstrate that the crack ellipticity (a/c) and crack relative depth (a/t) have significant effects on the KI, KII, and KIII of the SIFs. The KI plays a dominant role, which follows a symmetrical distribution at the symmetrical position on both sides of the deepest crack point, whereas the KII and KIII can be negligible. The corrected shape coefficient FI decreases with increasing ellipticity a/c and increases with increasing relative depth a/t under the combined tensile stress and bending loads. The comparison to the literature shows the calculation of the corrected shape coefficient has a high accuracy based on the FEM, which will be applicable and reliable for non-penetrating three-dimensional cracks.