FEM Software in Kyma: an Advanced Tool for Structural Design
The advanced structural design of megayachts, pleasure vessels typically having a total length of more than 50 meters, using FEM (Finite Element Method) software begins in Kyma in 2014 to meet the convergent needs of Classification Societies on the one hand and the design freedom of designers on the other.
FEM Analysis: a Combination of Safety and Style
FEM analysis meets the combination of two different and equally important needs: compliance with the increasingly stringent safety criteria imposed by the regulations of the Classification Societies and the demands of the great names of architects and designers to verify increasingly sinuous and complex hull parts and superstructures.
Large glass openings and large portions of cantilever decks are increasingly present in projects and require the use of advanced computing resources for an effective design that combines safety, durability, efficiency, and lightness.
The simulation software chosen in Kyma are those of Hexagon© which, for decades, support the technical study and structural design from the early stage of pre-processing, where the calculation models are prepared, up to the post-processing, where the results are interpreted.
MSC Apex: Between Pre-Processing and Defeaturing
MSC Apex is a state-of-the-art software, which, thanks to its features dedicated mainly to pre-processing, allows our FEM analysts to prepare calculation models very quickly. The estimate of the reduction in the time taken to obtain calculation models necessary to meet the design criteria, in fact, is reduced by about ten times compared to traditional methods.
This software is an indispensable tool for the preparation of complex geometries, and it interfaces perfectly with the most common 3D CAD export used in the naval field.
Among its main features there is the possibility to quickly simplify three-dimensional structural geometries in solid format (in which the thickness of the structure is also represented), extracting its own mid-plane and greatly benefiting the phase, as tedious as delicate, of defeaturing. During this phase of simplification of the geometries, in fact, the analyst FEM must be able to recognize if and where it’s possible realize simplifications or approximations (defections) to the geometry of the calculation model, that could affect the final result.
MSC Nastran: the Beating Heart of the FEM Equations
MSC Nastran is the solver and the beating heart of the resolution of equation systems based on the Finite Element Method: developed in the late 60s and compiled mainly in Fortran language, is one of the most consolidated historical calculation codes for naval design.
This software allows to solve and verify complex structural systems through the structural discretization called mesh or calculation grid. It contains different resolution methods that offer designers the possibility to examine the structure by reflecting in the most precise way possible the real physical behaviour, starting from static and dynamic (linear and non-linear) analyses up to the calculations of instability, proper modes of vibration, fatigue life, thermal analysis, etc.
MSC Patran: Preparation of the Calculation Model and Post-Processing of the Results
MSC Patran is the iconic graphical interface of the software house Hexagon© and is among the most used in the industrial environments. Given its longevity, its graphical interface, spartan and not very user-friendly compared to the latest software generation, over the years has been expanded with many tools essential for the creation of reliable calculation models and the correct processing of results.
Kyma uses this powerful tool both for the preparation of the calculation model, as some features have not yet been implemented in MSC Apex, both for the processing of the output generated by the solver MSC Nastran.
This software has, among its most important features, specific tools to the correct visualization and interpretation of the results that allow the correct verification and validation of the analyzed structure.
FEM Software: the Encounter Between Engineering Challenges and Structural Assessments
The use of FEM software dedicated to structural analysis combined with the experience accumulated in over 20 years of activity allow our FEM analysts to cope with any engineering challenge necessary to meet all safety and reliability requirements necessary in the structural design of a recreational vessel.
FEM analyses, typically developed in Kyma for the validation of the megayachts structure, can be grouped into three macro-categories:
• Global Assessments affect hull girder and global vibrations and are used for the overall validation of the structure subjected to stress in still and rough water. With these analyses it is possible to predict the vibration levels generated by the propulsion system and the machines installed on board, which are the main cause of structural noise.
• Local Assessments: they concern foundations (such as fin stabilizers, cranes, propulsion systems, windlass etc.), helicopter landing, mooring areas, grillage structures and cantilevered decks, hatches and doors, large glazed openings, etc. These tests are carried out when, in order to verify and validate a very precise portion of the structure, local calculation models are created that help designers in identifying any criticalities or weaknesses.
• Detailed Assessments: are carried out on welds, structural hotspots, holes and cutouts, fatigue life, bolted connections etc. In these cases, the structure is placed under the magnifying glass of the FEM analyst, which will analyze in detail all the constructive details with which the megayachts will be realized.
FEM Analysis in Kyma: Safety, Performance and Space Optimization
Kyma has been investing in these types of software for years because the quality of the structural design provided has a strong impact on the demands of Italian and foreign shipbuilding.
The demand for structural assessments and optimizations is constantly growing and essential to deal with the increasing rise in the cost of materials used for the construction of megayachts such as steel and aluminium alloys.
In Kyma we can carry out a structural design that can efficiently reconcile both the required safety requirements both the lightness of the structure that, in synergy with the most modern propulsion systems, also reduce the emission of aquatic and atmospheric pollutants. The FEM analysis, moreover, allowing the minimization of the structural dimensions, allows to maximize the usable spaces on board leaving more space to the creative vision of architects and designers for the furnishing of the interior spaces.
