Investigation on Offshore Floating Mooring Chains Failure
Document Type
Article
Publication Date
Summer 10-27-2022
Abstract
The mooring system is essential for floating structures withstanding harsh environmental conditions, such as corrosion and variant wave loads. Failures of mooring systems has attracted researchers in different fields related to on-shore and off-shore activities. In this work, a study is conducted on a failed chain by conventional metallurgical failure analysis procedure including chemical analysis, tensile testing, and fracture surface examination. The studied samples included the failed section and samples from further region away from the failure. A 3D simulation model for the chain was demonstrated using ABAQUS Simula 2018. The results show that the maximum Von-Mises stress is around 790 MPa which exceeds the breaking load of R3 steel. On the other hand, using R4 steel, which has a higher UTS of 860 MPa, would have assured a safer design as the stresses generated at the same conditions are lower than the breaking load of R4 steel, compared to R3 steel. The microstructure confirmed that the material is low carbon alloy steel with ferrite and perlite grains along with iron oxide pits, which would be presumed to have made the material rather brittle. Despite the fracture of the tensile samples showed ductile features, the fractographic analysis of the failed part reveals that the chain was fractured catastrophically in a brittle manner. FEA results are in accordance with the fractographic analysis. Finite element analysis of R3 steel shows that the stress magnitude caused by out of plane bending (OPB) forces is 15% greater than that of ultimate tensile strength.
Recommended Citation
Salem, Serag, "Investigation on Offshore Floating Mooring Chains Failure" (2022). Mechanical Engineering. 71.
https://buescholar.bue.edu.eg/mech_eng/71