Numéro : 2782 - Year : 2022
Parametric method for the assessment of fatigue damage for marine shaft line
Corentin GUELLEC - NAVAL Group, France et ENSTA Bretagne - IRDL – UMR CNRS 6027, France
Ludovic JIAN - NAVAL Group, France
Cédric DOUDARD, Bruno LEVIEIL, Sylvain CALLOCH - ENSTA Bretagne - IRDL – UMR CNRS 6027, France
Anthony EZANNO - DGA Techniques navales, France
A parametric method is introduced for the assessment of the fatigue life of marine shaft lines. The particularity of the method lies in the fact that it introduces relevant load modelling around a limited number of parameters specific to marine shaft lines while depicting the loading complexity (multiaxiality, mean stress effect, non-proportionality of the loading path). The loading of shaft lines is mainly composed of three types of loading acting at the same time. The first loading is the rotational bending induced mainly by the weight of the shaft and the weight of the propeller. The second loading is the torsion resulting from the torque generated by the engine and the propeller. Finally, the last loading is the compression resulting from the thrust imposed by the propeller on the shaft line. The differences in frequencies existing between these loadings imply effects of non-proportionality as well as mean stress within the shaft line. An adapted modeling is introduced in order to preserve the properties of the loading while not relying on expensive cycle counting algorithms to perform an analysis.
The original method is designed to allow fatigue damage assessments for both in-service shafts and pre-design phase shafts, working towards a particular fatigue damage mode. The observations made in this study show two damage modes. On one hand, a damage mode issued from multiaxial cycles and associated with ship maneuvers, corresponding to HCF regime. On the other hand, there is a damage mode in the VHCF regime resulting from bending stress cycles due to the structure rotary bending.