Why is FEA needed?

Shipyards and Naval Architects know them all to well – rules and regulations for classification.  To verify your designs you sure will come across Lloyd’s Register or other classification autorities. According to Lloyd’s rules for Special Service Craft – Finite Element Analysis is required for any steel or aluminium mono-hull craft with a rule length greater than 75 meters.

Femto Engineering assists Dutch shipyards and naval architects with global hull analyses and harmonic response analysis. We can build all necessary FE-models, perform all the needed analyses, post-process the results and write reports according to Lloyds Register or other classification authorities.

Our approach

A coarse model of the full ship will be made using CAD input to assess yield and the buckling of critical areas. Modelling and element requirements are given by the classification rules.

At first, a Global Hull Analysis will be performed. The primary structural components of the hull and (mostly aluminium) upper structure have to resist lateral hydrodynamic and hydrostatic pressure and global loads. We focus on parts in the ship that show high stress peaks (hatches, crane-, rudder- and stabilizer foundations) that need to be analysed in more detail. When needed we make recommendations on how to meet the acceptance criteria.

Femto will use the FE-model created for the Global Hull analysis, with which the lowest natural frequencies and accompanying mode shapes will be calculated. Also an overview of the critical areas, including suitable solutions to meet the requirements will be made.

At the end of a verification project a report is made in accordance to Lloyds Register’s “Lloyds Direct Calculations for Special Service Craft of Metallic Construction” or another classification authority.

If you are interested in the services that Femto provides concerning this topic please do not hesitate to contact us for more information.

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