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Role of Crack Tip Strain Rate on the Fatigue and Fracture Behavior of Line Pipe Steel in Sour Environments

Fatigue and fracture of line pipe steels in a sour inhibited environment is presented. Fatigue crack growth rate (FCGR) was investigated as a function of frequency at several different K values at a pH of 3.5 and 0.21psia (0.00144MPa) H2S. 

Product Number: 51317--9203-SG
ISBN: 9203 2017 CP
Author: Thodla Ramgopal
Publication Date: 2017
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Fatigue crack growth rate (FCGR) behavior and fracture toughness of strained and aged line pipe steel was investigated in a sour inhibited environment. The effect of varying frequency and DK were investigated on the FCGR. The effect of wave form was investigated at a frequency of 0.1Hz to investigate the effect of crack tip strain rate. Tests were performed over a range of DK. The da/dN data was modelled based on the crack tip strain rate at each DK. Rising displacement fracture toughness tests were performed at a slow K-rate to determine initiation fracture toughness. The effect of loading mode was determined by comparing the crack growth rate (CGR) obtained under constant load versus constant displacement.The CGR from the rising displacement and the FCGR at various DK and frequency were related to each other based on a crack tip strain rate model. The results appear to indicate that the CGR under rising displacement and the CGR under cyclic loading were part of continuum that were related through the crack tip strain rate.

Key words: Sour Service, Fatigue Crack Growth Rate, Static Crack Growth Rate, Frequency Scans,

Fatigue crack growth rate (FCGR) behavior and fracture toughness of strained and aged line pipe steel was investigated in a sour inhibited environment. The effect of varying frequency and DK were investigated on the FCGR. The effect of wave form was investigated at a frequency of 0.1Hz to investigate the effect of crack tip strain rate. Tests were performed over a range of DK. The da/dN data was modelled based on the crack tip strain rate at each DK. Rising displacement fracture toughness tests were performed at a slow K-rate to determine initiation fracture toughness. The effect of loading mode was determined by comparing the crack growth rate (CGR) obtained under constant load versus constant displacement.The CGR from the rising displacement and the FCGR at various DK and frequency were related to each other based on a crack tip strain rate model. The results appear to indicate that the CGR under rising displacement and the CGR under cyclic loading were part of continuum that were related through the crack tip strain rate.

Key words: Sour Service, Fatigue Crack Growth Rate, Static Crack Growth Rate, Frequency Scans,

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51312-01477-Environmental Effects on Fatigue Crack Growth Rates in Sour Environments

Product Number: 51312-01477-SG
ISBN: 01477 2012 CP
Author: Ramgopal Thodla
Publication Date: 2012
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