Model Updating for Vibration Analysis of Finite Element and Numerical Models
Why is model updating important?
To minimise the error between the analytical/FEA model and the physical item/structure.
Why? Because the analysis could be incorrect, as it is well known that finite element predictions are often questioned when conflict with test results. This is our experience over 3 decades, and therefore have updated our models since 2004.
What is model updating?
Model updating is an iterative process using measured data to update an analytical model or a finite element model of a structure, machine, vehicle etc. to obtain a model of representative dynamic behaviour to the physical structure.
In structural dynamics, measured and analysed vibration data, from experimental modal analysis, is used to update an analytical model or a finite element model.
How do we perform model updating?
We update models by:
Analysing the structure in FEA
Measuring the structural behaviour of that structure
Analysing that structural data
Iteratively update the model to reduce the error
When is it beneficial to use model updating?
Model updating ensures that the model is a true representation of the physical item.
Companies that manufacture any item that causes vibration in its structure and items that are subjected to vibration in the immediate environment, will benefit from model updating in their design and analysis processes.
What advantage is there in model updating?
When model updating is used extensively in a company, the constraints and assumptions made for modelling are updated, and then used for future analysis.
When model updating in implemented as a process, the numerical models over time will become more representative of the physical item, and the error between the model and the physical item will decrease and eventually be negligible.
At this stage, the assumptions and constraint made in the model, can be trusted, and then testing is only conducted for, i.e. certification, and can be just a tick in the box.
Modelling assumptions and constraints are made when modelling an item in finite elements. To verify that these assumptions are correct, a physical item is tested
An example of model updating as a process
Assume a company designs and manufactures electric generators for aircraft. The company will design, analyse and test the generators to prove that they operate reliably.
But when they test the generators, they fail; but finite element analysis was performed and all results were favourable - but they were not, as the unit failed.
So modal analysis and test data is used to update the model. Once the model is updated, a design flaw is revealed, and corrected. And then manufactured and tested again.
Over time, the iterative updates correct the assumptions, and the FEA models become more accurate.
Resulting in more trust in the FEA results and performing testing just as a formality.
This process takes investment, but inevitably saves time overall, and becomes an efficient process.
How we can help you
If you need help updating a FEA model or to investigate unwanted vibration, we can use our model updating skills and experience to help you. Please call 01908 643433 to speak to a mechanical engineering consultant
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