Effects of Loading Spectra on High pH Crack Growth Behavior of X65 Pipeline Steel
| Autor: | Erwin Gamboa, Lyndon Lamborn, Karina Chevil, Weixing Chen, Hao Zhang, Hamid Niazi |
|---|---|
| Rok vydání: | 2020 |
| Předmět: |
Materials science
020209 energy General Chemical Engineering Pipeline (computing) 02 engineering and technology General Chemistry Strain rate 021001 nanoscience & nanotechnology mental disorders 0202 electrical engineering electronic engineering information engineering General Materials Science Anodic dissolution Stage (hydrology) Stress corrosion cracking Composite material 0210 nano-technology |
| Zdroj: | Corrosion. 76:601-615 |
| ISSN: | 1938-159X 0010-9312 |
| DOI: | 10.5006/3472 |
| Popis: | The effects of mechanical factors on crack growth behavior during the second stage of high pH stress corrosion cracking in pipeline steel were investigated by applying several loading scenarios on compact tension (CT) specimens. The main mechanism for stage 2 of intergranular crack propagation is anodic dissolution ahead of the crack tip which is highly dependent on crack-tip strain rate. The maximum and minimum crack growth rates were 3 × 10−7 mm/s and 1 × 10−7 mm/s, respectively. It was observed that several factors such as mean stress intensity factor, amplitude, and frequency of loading cycles determine the crack-tip strain rate. Low R-ratio cycles, particularly high-frequency ones, enhance secondary crack initiation, and crack coalescence on the free surface. This mechanism accelerates crack advance on the free surface which is accompanied with an increase in mechanical driving force for crack propagation in the thickness direction. These findings have implications for pipeline operators and could be used to increase the lifespan of the cracked pipelines at stage 2. For those pipelines, any loading condition that increases the strain rate ahead of the crack tip enhances anodic dissolution and is detrimental. Additionally, secondary crack initiation and coalescence could be minimized by avoiding internal pressure fluctuation, particularly rapid large pressure fluctuations. |
| Databáze: | OpenAIRE |
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