Most of the times structures are subjected to time varying loads and boundary conditions. When such variations have an impact on the response of the structure it is important to execute a so-called transient analysis.
Transient Analysis is used to evaluate the effects of the time varying loads on the analysed components. Usually, the results of a dynamic analysis are dependent on two main factors:
- The “natural” behavior of the investigated structure.
- The load variation during the considered time.
A thorough understanding of the physic of the problem is strictly necessary when dealing with transient calculations due to the large calculation time that is normally required to analyse this kind of problems.
Therefore we apply a standard workflow to all our transient calculations:
- Preliminary static analysis to highlight the effects of possible non-linearity.
- A modal analysis to study the natural behavior of the construction.
- A simplified 1D or 2D analysis representative of the global behavior of the structure.
- More refined 2D or 3D calculations to assess the detailed and local effects that can result in issues for the structure.
Good engineering judgement is very important when dealing with transient calculations. In particular if “appropriate” results are needed in a reasonable time and “simplified” transient calculations using modal superposition or harmonic analyses can be applied.
When to use dynamic FEA
Exciting a particular mode with a high energy content can result in premature failure of a structure and this can never be evaluated by a static analysis!
Steel to steel impacts between components are a clear example of this and we have an extensive experience in analysing impact calculations and the dynamic development of stresses in the components.
Some examples where we used dynamic FEA are the analysis of the impact from Hydraulic Piling Hammer during pile driving, the effects of a ship impact on a structure like an Offshore Wind Turbine, and Train Brake disc and shoe development.