Active Fatigue Management

Light Structures offers services in data management onshore to help the maintenance planners and other onshore personnel manage the assets in the best way. Reports, which summarize the hull condition, are available based on data from the HSM system. Data can be transferred for onshore analysis on backup media. Regular condition reports are a supplement to inspections and provide hull status documentation that can be used towards maintenance planning, customers, authorities, environmental groups and potential buyers.

Our recommendation for analysis of actual fatigue life in hotspots, is to place a fiber optic strain sensor in a location near the hotspot(s) of interest, where the stress is well defined (no gradients), and calculate the hotspot stress and consequent fatigue damage using Stress Concentration Factors found from the design calculations (hotspot locations and SCFs are yard supply). One strain sensor can be used to calculate stress and fatigue in several nearby hotspots, based on individual SCFs for the hotspots. Individual SN-curves may also be defined.

Comparison of actual fatigue life with design fatigue life is a standard function in the SENSFIB system. The result is normally presented based on the latest half hour of data (single point in time) with a bar graph, and the time history of the comparison implemented as an onshore function. An online graphical representation of the timeline can be implemented onboard as a custom function in the Human-Machine Interface. In case there is a significant difference between the actual fatigue life and the design life, the system can provide the user with advice on the cause of this difference. The standard function is to present the overall fatigue life calculation together with the contribution due to wave loading (included in design life) and contributions due to vibrations (not included in design life). With access to a full set of design parameters and environmental data, including wave data, it is possible to extend the advisory function to include a comparison of the actual loading conditions with the loading conditions used for design life calculations, as well as a comparison of the actual wave scatter with the design wave scatter.