Umbilical cables are composed by several internal components helically disposed and externally protected by an outer polymeric sheath. With these elements wound in different directions, internal friction is a well-known structural feature, originating hysteretic loops when umbilicals are subject to cyclic loads. On the other hand, polymeric materials represent a substantial part of an umbilical composition. These materials present a viscoelastic character, introducing a second energy dissipation mechanism to these flexible structures. Therefore, this paper aims to assess the hysteresis phenomenon observed under different periodic axial loading conditions.
The study is based on experimental campaigns carried out with two umbilical cables, proposing and testing a new experimental methodology based on standard instrumentation combined with optical tracking measurement. The hysteresis loops are evaluated considering ‘slow’ and ‘very-slow’ axial cyclic loads. The results indicates that an equivalent viscoelastic damping behavior could be adopted to model the umbilical cable response under ‘slow’ axial cyclic loads. In contrast, the ‘very-slow’ tests indicate that the energy dissipation process is dominated by a dry friction mechanism.
