Fatigue life assessment of welded joints made of the stainless steel X6CrNiNb18-10 for thermomechanical and variable amplitude loading

2018 ◽  
Vol 49 (3) ◽  
pp. 316-331
Author(s):  
A. Bosch ◽  
M. Vormwald ◽  
S. Schackert ◽  
C. Schweizer
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Welded Joints ◽  
Life Assessment ◽  
Variable Amplitude Loading ◽  
Variable Amplitude ◽  
Fatigue Life Assessment

Equivalent crack approach for fatigue life assessment of welded joints

2015 ◽  
Vol 149 ◽  
pp. 144-155 ◽  
Author(s):  
Eeva Mikkola ◽  
Yukitaka Murakami ◽  
Gary Marquis
Keyword(s):  
Fatigue Life ◽  
Welded Joints ◽  
Life Assessment ◽  
Fatigue Life Assessment

Applicability of Equivalent Constant Amplitude Loading for Assessing the Fatigue Life of Pipelines and Risers and the Influence of Compressive Stress Cycles

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
Mohammad Iranpour ◽  
Farid Taheri
Keyword(s):  
Experimental Investigation ◽  
Fatigue Life ◽  
Compressive Stress ◽  
Time History ◽  
Life Assessment ◽  
Constant Amplitude ◽  
Safety Factors ◽  
Variable Amplitude ◽  
Fatigue Life Assessment ◽  
Stress Cycles

Fatigue life assessment of pipelines and risers is a complex process, involving various uncertainties. The selection of an appropriate fatigue model is important for establishing the inspection intervals and maintenance criteria. In offshore structures, the vortex-induced vibration (VIV) could cause severe fatigue damage in risers and pipelines, resulting in leakage or even catastrophic failure. The industry has customarily used simple fatigue models for fatigue life assessment of pipelines and risers (such as the Paris or Walker models); however, these models were developed based on constant amplitude loading scenarios. In contrast, VIV-induced stress-time history has a variable amplitude nature. The use of the simplified approach (which is inherently non conservative), has necessitated the implementation of large safety factors for fatigue design of pipelines and risers. Moreover, most of the experimental investigations conducted to date with the aim of characterizing the fatigue response of pipelines and risers have been done based on incorporation of constant amplitude loading (CAL) scenarios (which is unrealistic), or converting the variable amplitude loading (VAL) scenarios to an equivalent CAL. This study demonstrates that the use of such approaches would not be lead to accurate assessment of the fatigue response of risers subject to VIV-induced VAL. The experimental investigation performed in this study will also clarify the underlying reasons for the use of large safety factors by the industry when assessing the fatigue life of pipelines and risers. In addition, an experimental investigation was also conducted to highlight the influence of the compressive portion of VIV stress-time history on the fatigue life of such components. It is shown that the compressive stress cycles significantly influence the fatigue crack growth response of risers, and their presence should not be ignored.

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