This report outlines revisions made to IACS(International Association of Classification Societies Ltd.) UR M68 and the properties of an intermediate shaft material developed by Kobe Steel, Ltd. (40CrMo8). The company received special approval from ClassNK in February 2014 for this steel material, which has a minimum tensile strength greater than 800N/mm2.
The material has a torsional fatigue strength equal to or greater than that of conventional steel. Furthermore, the material does not exhibit any deterioration of notch sensitivity despite an increase in tensile strength.
Using this high strength intermediate shaft material is expected to increase permissible torsional vibration stresses and reduce shaft weight.
