Banca de DEFESA: Lucas de Oliveira Barros

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : Lucas de Oliveira Barros
DATE: 18/08/2023
TIME: 08:00
LOCAL: Plataforma Microsoft Teams
TITLE:

Fatigue life estimate of metal chain links of mooring systems assume out of plane bending.

KEY WORDS:

Normal stress at the hotspot; mooring-fairlead system; out-of-plane bending; fatigue life estimate; SWT approach

PAGES: 100
BIG AREA: Engenharias
AREA: Engenharia Mecânica
SUMMARY:

In this work, a numerical and analytical study of the fatigue life of chains links belonging to the mooring system of Floating, Production, Storage and Offloading (FPSO) is carried out. Initially, equations are proposed for the calculation of the normal stress at the hotspot, taking into account normal stresses generated by axial loads and the cyclic bending that occurs outside the main plane of the links, called out-plane-bending (OPB). The analytical equation considers the angle of operation of the mooring systems as well as the interlink angle of the links and angle of rotation of the fairlead. Due to the loads present in the mooring systems, there is an increase in the friction force resulting in the contact between the links, making it have a behavior similar to a crimp. The crimp behavior between the links generates transverse forces that contribute to the flexion outside the plane. The loadings are due to the conditions of operations that happen within the FPSO platform, such as the handling, transport and storage of oil and natural phenomena such as sea currents and winds, contributing to the requests in the mooring lines. All the modeling for the numerical study was done in the commercial software ABAQUS, it was considered as the material of the chains the offshore steel belonging to the grade R4. The validation of the equations is done by comparing the stress values obtained through numerical simulations of the mooring-fairlead system, where a satisfactory correlation was observed. Loads are generated with constant and variable amplitude as well as random load histories, always between the minimum and maximum operating load of the system, which corresponds to 1/6 and 1/3 of the minimum break load (MBL) of the chain link. Based on the Smith-Watson-Topper (SWT) approach, the fatigue life of the chain was estimated, considering the analytical value of the stress at the hotspot based only on the axial loading contribution and later, due to the axial and OPB contributions. Finally, it was verified that the analytical equation was able to determine the stress values at the hotspot and that the effect of normal stress at the hotspot due to OPB can cause a severe loss in the fatigue life of the mechanical component.

COMMITTEE MEMBERS:
Externa ao Programa - 1125400 - DEBORAH DE OLIVEIRA - nullInterno - 1345908 - JOSE ALEXANDER ARAUJO
Externo à Instituição - LEONEL LEONARDO DELGADO MORALES
Presidente - 1816660 - LUCIVAL MALCHER