In this work, the stress ratio effect on FCP of longitudinal welded joint regions of an API X-70 steel under constant amplitude loading and variable amplitude loading under a single cycle peak tensile application was investigated. The results obtained lead to the following conclusions. The longitudinal welded joint regions subjected to R 0.5 initially presented the highest FCP rates in the constant amplitude tests. At higher A/C values all welded joint regions present similar behaviour indicating that the FCP rates get more independent from the i-values. The similarity between crack growth rates at high A/C in each region may indicate a dominant crack growth mechanism or a decreasing of crack closure phenomena. The discrepancy between values from Paris constants may indicate an influence of the microstructure on FCP of the welded joints investigated. Single peak tensile application on variable amplitude tests promoted delays on FCP rates in all welded joint regions for both values, as expected. However, the propagation delay was not observed at elevated values. The higher amount of secondary microcracks at elevated AK values promoted by application can explain this behaviour.
Fatigue crack propagation in API 5L X-70 pipeline steel longitudinal welded joints under constant and variable amplitudes
Fatigue and Fracture of Engineering Materials and Structures ; 34 , 5 ; 321-328
2011
8 Seiten, 10 Bilder, 5 Tabellen, 30 Quellen
Article (Journal)
English
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