Vibration analyses would typically consist of vibration prediction and vibration reduction recommendations, with proposals for improved structural design. Calculations are based on the finite element technique.
The Finite Element (FE) analysis is a powerful tool for vibration prediction, natural frequency and mode shape analysis and forced response calculation.
The FE analysis builds on the simple concepts of linearization, discretization, and interpolation. The infinite number of degrees of freedom in a continuous system is reduced to a finite representation well suited for numerical analysis.
A specific use of FE technique is made on marine structures in order to:
- Verification of ship vibrations with regard to acceptable levels defined in building specifications
- Avoid resonance conditions in new-buildings
- Evaluate dynamic properties, e.g. mobility / stiffeners of machinery foundations and shaft bearing supports
Lloyd's Register ODS uses state-of-the-art-tools for FE analysis, including ANSYS, NASTRAN and I-deas and can offer more than 20 years of experience within the industry. In addition to this, Lloyd's Register ODS also uses in-house developed FE code for special applications. The combination of these tools enables Lloyd's Register ODS to use nonstandard methods such as:
- Quality mesh generation
- Automated hull meshing
- Modelling of structural-hydrodynamic interaction
- Sub-modelling techniques
- Super elements
- Master degrees of freedom
- Contact elements
- Plastic and non-linear elements
- Topological optimization
- Stochastic loading
Special assignments requiring tailor made tools can be performed on existing models by importing data from most commercial FE codes.
Lloyd's Register ODS also participates in the proper choice of propeller design and aft body lines to achieve the best possible noise and vibration performance of the propeller. Our Boundary Element based PROPULSE computer model is used for prediction of propeller cavitation and vibration characteristics.
For detailed information on how Lloyd's Register ODS engineers can help you with your vibration analyses initiatives, please contact us.
