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51318-11204-Nondestructive Evaluation for Yield Strength and Toughness of Steel Pipelines

This paper describes two new and complementary mechanical testing methods recently applied to vintage pipeline steels as input to integrity management.

Product Number: 51318-11204-SG
Author: S. D. Palkovic / K. Taniguchi / S. C. Bellemare
Publication Date: 2018
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Material mechanical property data including fracture toughness help address potential integrity threats such as material loss through corrosion, stress corrosion cracking (SCC), and fatigue. In- the-ditch (ITD) nondestructive evaluation (NDE) of mechanical properties has expanded beyond traditional hardness testing to provide measurements of strength and fracture toughness of metals without the need for sample removal and laboratory testing. This paper describes two new and complementary mechanical testing methods recently applied to vintage pipeline steels as input to integrity management. In the first method, hard blunt styluses of different geometries slide over the pipe surface at constant loads to measure material hardness. The hardness values for dissimilar styluses are input into predictive equations to determine the yield strength and ultimate tensile strength of the steel. When performed over longitudinal seams or girth welds, the tests identify the heat treatment including normalization. In the second method, the instrument is equipped with a wedged-shaped stylus that includes an opening, or stretch passage, where material is locally subjected to tension that results in microvoid growth and coalescence that match laboratory ductile fracture. The material response is correlated with the fracture toughness through measuring the crack tip opening displacement. Field studies and validation provide examples of application of the methods.

 

 

Material mechanical property data including fracture toughness help address potential integrity threats such as material loss through corrosion, stress corrosion cracking (SCC), and fatigue. In- the-ditch (ITD) nondestructive evaluation (NDE) of mechanical properties has expanded beyond traditional hardness testing to provide measurements of strength and fracture toughness of metals without the need for sample removal and laboratory testing. This paper describes two new and complementary mechanical testing methods recently applied to vintage pipeline steels as input to integrity management. In the first method, hard blunt styluses of different geometries slide over the pipe surface at constant loads to measure material hardness. The hardness values for dissimilar styluses are input into predictive equations to determine the yield strength and ultimate tensile strength of the steel. When performed over longitudinal seams or girth welds, the tests identify the heat treatment including normalization. In the second method, the instrument is equipped with a wedged-shaped stylus that includes an opening, or stretch passage, where material is locally subjected to tension that results in microvoid growth and coalescence that match laboratory ductile fracture. The material response is correlated with the fracture toughness through measuring the crack tip opening displacement. Field studies and validation provide examples of application of the methods.

 

 

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