Assessment of Danger Due to Cracks in Structural Elements of Different Shapes and Geometry

Abstract

In the paper the analytical relations for calculations of stress intensity factor $K_{I}$ and their change ${{dK_{\text{I}} } \mathord{\left/ {\vphantom {{dK_{\text{I}} } {da}}} \right. \kern-0pt} {da}}$ (a – characteristic size of crack-like defect) at the crack tip in the structural elements during crack growth are presented. For each structural element with a crack-like defect of assigned shape and location the dimensionless dependences like $({{\sqrt t } \mathord{\left/ {\vphantom {{\sqrt t } p}} \right. \kern-0pt} p}) \cdot ({{dK_{\text{I}} } \mathord{\left/ {\vphantom {{dK_{\text{I}} } {da}}} \right. \kern-0pt} {da}}) = F(a/t)$, where t – the size of structural element in the crack growth direction; p – internal pressure. These dependences have certain specific features: There is some defect size $(a/t)_{ * }$, beginning from which the rate of SIF $K_{I}$ variation significantly increases. Hear are considered on example of the few pipeline systems with defects of different shape and location under internal pressure. In the paper was constructed the depending on the characteristic values $(a/t)_{ * }$ of the ratio of sizes of the pipeline and were analysed pipelines with existing crack-like defects of various shapes and geometry. The proposed approach can serve as tools for more detailed proximate analysis not only of pipeline systems, but also other structural elements that may occur in engineering.