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Constraint Corrected - Curve and its Application to Fracture Assessment for X80 Pipelines Pages: 17 Published: Jan 2007
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View License Agreement Source: STP1480-EB Abstract Single specimen curve testing for X80 pipeline steel was conducted using single edge notched bend (SENB) and single edge notched tension (SENT) specimens with various crack lengths. Test data indicate that the curves for this steel are strongly constraint dependent. To facilitate transferability of experimental curves to those for actual cracked components, this paper develops a constraint corrected curve for X80 steel. A modified theory that can consider the global bending stress influence is proposed so as to correctly quantify constraint effect on the crack-tip fields and the curves. Results show that the modified solution can well match numerical crack-tip fields for bending specimens, with being a load-independent constraint parameter under large scale yielding. Based on the experimental data and numerical analysis, a constraint corrected curve is formulated as a function of the parameter and crack extension a for X80 steel. A general procedure to predict curves for actual cracked components is then outlined.Comparison indicates that the predicted curves developed in this paper agree well with the experimental data for both SENB and SENT specimens. To demonstrate its application in failure assessment, the constraint corrected curve for X80 steel is used to determine failure loads for a surface cracked pipeline. Reasonable agreement to available analytic solution is achieved.
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