Comparison of Bitumen’s Large Strain Viscoelastic Properties in Cables and Umbilicals to Small Strain Rheometer Measurements Available to Purchase

When a steel wire armored cable or umbilical is bent, the armor wires will move relative to the underneath layer if the wires are free to move. If this movement is restricted by friction or stiff bitumen, the bending will result in shear stress in the armor wires. In the case of bitumen, the bitumen will behave as a viscoelastic material dependent on temperature, frequency, and strain. Comparison of measurements of bitumen with small and large strain shows that the viscoelastic properties of bitumen are highly affected by the size of the strain. Therefore, the small strain rheometer measurements are not suitable for describing the viscoelastic properties of bitumen in the case of repeated bending of the cable or umbilical to a certain curvature.