Finite Element Analysis

The ØDS Machinery Dynamics Group has investigated and solved many machinery problems and failures by using Finite Element Analysis.

Today, we are one of the most respected independent consulting companies in the world with state of the art FEA tools. Our experience with turbomachinery is especially strong.

• Machine Components
• Machine Foundations
• Offshore Structures
• Marine Structures
• Wind Turbines
• Piping
• Static Stresses and Strain
• Natural Frequencies and Mode Shapes
• Forced Response
• Fatigue and Lifetime Estimation
• Plasticity and Nonlinear Material

Finite Element Analysis

History
Finite element (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.

For years, the FE method has been used to solve complex problems, particularly in solid mechanics.

Approach
Today, FE analysis is used in industrial applications for:

• Structural static and dynamic analyses
• Thermodynamics
• Electro-magnetics
• Fluid mechanics

The basis for this widespread use is that the method is very flexible and can be used for comprehensive calculations.

On the other hand, one has to be very careful with verifying the results. To us this means:

• Verification of model assumptions
• Assuring mesh quality
• Comparison with physical tests

Machine Components
The FE method can be used for static evaluation of mechanical strength and safety margins on machine components. Furthermore, it can, by means of dynamic analysis, locate weak spots in the component if it is subjected to dynamic loading. Typical areas of applications are:

• Impellers
• Bladed disks
• Crank shafts
• Bearing housings

Foundations
ØDS has extensive knowledge and experience with application of the FE method on offshore and marine structures:

• Machine foundations
• Offshore platform dynamics
• Ship dynamics

In-house tools have been established for

• Automated hull and deck meshing
• Modelling of structural-hydrodynamic
  interaction
  

Piping Acoustics
ØDS has in-house as well as commercial programs for calculating acoustic pressure pulsations in process piping and other ducts.

• Process piping and funnels
• Exhaust pipes
• Resonator and silencer design

These programs are fully integrated with our FE tools for efficient mechanical response calculations.

Tools
ØDS uses state-of-the-art-tools for FE analysis, including ANSYS and I-deas. Furthermore, ØDS has developed an inhouse FE based rotor dynamic code for lateral and torsional dynamics.

These tools enable ØDS to use nonstandard methods, such as:

• Quality mesh generation
• Sub-modelling techniques
• Super elements
• Master degrees of freedom
• Contact elements
• Plastic and nonlinear elements
• Topological optimization
• Stochastic loading

Special assignments requiring tailor made tools can be performed on existing models by importing from most of the commercial FE codes.

Experience
Primarily, ØDS uses the FE method for design verification and troubleshooting.

It is our experience that many vibration problems can be avoided or resolved by the correct use of FE analysis and correlation with measurements on the physical structures where it is possible.

However, it should be emphasized that the FE method is just one of many tools. ØDS always tries to select the best tool for a given task.