A global-local fretting analysis methodology and design study for the pressure armour layer of dynamic flexible marine risers

• Published in: Tribology international 2020-02, Vol.142, p.105967, Article 105967
• Main Authors: O'Halloran, S.M., Connaire, A.D., Harte, A.M., Leen, S.B.
• Format: Article
• Language: English
• Subjects: Armor; Coefficient of friction; Crack initiation; Design engineering; Fatigue failure; Fatigue life; Finite element method; Flexible marine risers; Fretting; Fretting case study; Fretting fatigue; Fretting wear; Grooves; Mathematical analysis; Nub-groove contact; Risers; Ultrasonic testing
• ISSN: 0301-679X; 1879-2464
• DOI: 10.1016/j.triboint.2019.105967

In this paper, a global-local fretting design methodology for the pressure armour layer of flexible marine risers is outlined. This includes global dynamic riser analysis, geometrical and analytical sub-models and local nub-groove contact finite element analysis. Furthermore, a fretting test rig is developed and utilised to quantify coefficient of friction and wear coefficient under representative nub-groove loading conditions. The combination of the global-local computational methodology and experimental characterisation of pressure armour wire material allows for the development of running condition fretting maps. This identifies design criteria for critical riser global curvatures that are associated with minimum number of cycles to failure. The design methodology presented in this paper is applied to a realistic riser design study, using extreme sea-state loading conditions. In this case study, the predicted pressure armour fretting fatigue lives are found to be in the same range as the plain fatigue lives of the tensile armour layer. •Global-local fretting design methodology for the pressure armour layer of flexible marine risers.•Global dynamic riser analysis, geometrical and analytical sub-models and local nub-groove contact finite element analysis.•Development and utilisation of a fretting rig to quantify friction and wear coefficients under representative nub-groove loading conditions.•Identification of design criteria for critical riser global curvatures associated with minimum number of cycles to failure.•Realistic riser design study, using extreme sea-state loading conditions.