Strain–life characterization of lead sheath for submarine cables using small-scale and full-scale bending fatigue tests

The lead (Pb) water barrier in submarine power cables is a key component that prevents seawater ingress; however, due to its high ductility, it is vulnerable to cyclic bending loads during manufacturing, transportation, and long-term operation. In particular, after installation, the J-tube exit region is exposed to seawater-induced cyclic bending, leading to a high risk of fatigue failure. Existing high-cycle fatigue (HCF) fatigue-life data is limited to elastic stressrange conditions, which restricts accurate life prediction under operating conditions where large deformation may occur. In this study, low-cycle fatigue (LCF) tests were conducted on the lead water-barrier material using a bending fatigue test method at room temperature (20°C) and operating temperature (80°C), thereby obtaining strain–life data in the plastic regime. In addition, four-point bending fatigue tests were performed on a single-core cable to verify consistency with the material-level test results. The results confirm that the bending fatigue life of the lead water barrier under large-deformation bending can be quantitatively predicted based on the LCF test data.