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原文传递 Strain-Based Design: Strain Concentration at Girth Welds.

题名：	Strain-Based Design: Strain Concentration at Girth Welds.
关键词：	design,pipelines,guidelines/internal pressure, plastic properties, heat affected zone, submerged arc welding, gas metal arc welding, comparative evaluation, fracture toughness, cracks, tensile properties, models, stress-strain relationship/internal pressure, plastic properties, heat affected zone, submerged arc welding, gas metal arc welding, comparative evaluation, fracture toughness, cracks, tensile properties, models, stress-strain relationship
摘要：	This program aimed to improve guidelines for strain-based design of pipelines by studying cases with combinations of internal pressure and axial plastic strain in tension. Softened heat-affected zone (HAZ) regions have been observed to concentrate strain, particularly under internal pressure. HAZ softening has been observed for welds on X-70 and X-80 steels. Cases with little or no softening have also been observed for other welds in these same grades. This project extended these findings to X-100 steels, with cases of obvious softening and little or no softening observed. Higher heat inputs and larger weld volumes per pass associated with submerged arc welding (SAW) as compared to gas metal arc welding (GMAW) have been correlated with greater softening in each of these pipe grades. Finite-element modeling of girth welds was used to learn the relative effects of overall loading mode, HAZ thickness, weld metal strength, and pipe wall thickness. While strain may be severely concentrated in some cases, most cases did not show large increases in strain in the HAZ even with 10%lower tensile properties in the HAZ than in the base metal. The cases of severe strain concentration showed shear bands forming at 45 degrees to the radial direction along the internal weld toe and extending in regions of lower mechanical strength than the base metal. These bands may go away from the weld centerline or toward the weld centerline so that they cross in the weld metal. Models more representative of real welds in X-100 and in X-65 did not show high strain concentrations. These models included stress-strain relations and HAZ widths based on local mechanical testing. Some checks of strain concentration with high-low misalignment were also made using these material models. / Title Note: Final rept. / Supplementary Notes: Sponsored by Minerals Management Service, Herndon, VA. and Department of Transportation, Washington, DC. Research and Special Programs Administration. / Availability Note: Order this product from NTIS by: phone at 1-800-553-NTIS (U.S. customers); (703)605-6000 (other countries); fax at (703)605-6900; and email at orders@ntis.gov. NTIS is located at 5301 Shawnee Road, Alexandria, VA, 22312, USA. / NTIS Prices: PC A11 / Corporate Author Code: 005518251 / Classifivation: Unclassified report
报告类型：	科技报告