Introduction of the delta concept for characterising pipe yield strength

The rapidly increasing demand for cleaner energies has significantly driven the need for natural gases. Consequently, pipeline manufacturing industries are flourishing, as pipelines can efficiently transport gas. A critical quality measure for these pipelines is their yield strength, because applying a higher operating pressure can reduce the transmission cost; a reasonable range of yield strength also ensures protection from failure. Studies regarding the yield strength change from a plate to pipe have been conducted over the decades and are still garnering a strong interest from steel and pipe-manufacturing companies, who need to ensure a high quality of their products. Hitherto, an effective universal measure that characterises the yield strength change from a plate/coil to a pipe has not been established. This implies that with existing measures, the pipe yield strengths can vary significantly for the same steel grades manufactured by the same groups (or by different groups across different times). The current study proposes a novel measure δ for characterising/indicating/predicting the change in pipe yield strength that is based on the recognition of the dominant role of plastic deformation. The authors argue that δ could be developed into a universal measure for steel and pipe-manufacturing industries. To verify its generality, δ was first implemented to process a wide range of pipe data collections from systematically conducted numerical simulations, followed by a series of tests conducted using a laboratory pipe-manufacturing facility, and historical experimental results conducted by different groups at different times. It was demonstrated that δ exhibited a critical advantage over the traditionally used measure (t/D ratio). Finally, a (extra) discussion on industrial data processing is provided such that this study can contribute to a larger community.