Interpreting the results of an FEM simulation is an essential skill for any engineer working with this type of analysis. The Finite Element Method (FEM) is a wonderful tool that lets us visualise and understand the behaviour of structures and materials under different conditions. But what do those colourful plots and numbers that come out of the process really mean? Here is a helping hand so you can get the most out of your FEM simulations.
Understanding the results of an FEM simulation
FEM simulation results are usually presented as a distribution of stresses, displacements and strains in the model under study. This data is fundamental for assessing the performance of a structure or component under specific loading and constraint conditions.
Why is it important to analyse stress tensors?
When you run an FEM simulation, one of the most common results you get is the stress tensor. It is critical because it reveals how stress is distributed inside the material. If the stresses exceed the strength of the material, you could be facing a potential failure. This is especially important in industries such as aeronautics or automotive, where safety is paramount.
When looking at the stress distribution, look for the red areas, which typically indicate stress concentrations. These areas may suggest the need to redesign or reinforce the structure.
How to interpret displacements?
Displacement is another classic output of an FEM simulation, showing how much a specific point of the model is moving because of the applied loads. The visualisation can show you whether there is excessive displacement, which could indicate that the component will not fulfil its function or that it will clash with other elements.
Pay attention to any anomalous displacement; in most cases, you should see smooth, continuous displacements. Abrupt jumps could be a sign of a modelling error or incorrectly applied boundary conditions.
Detecting errors in the simulation
Sometimes the results do not seem to make sense, and that is when you have to consider possible errors. Remember to check the support and load conditions first. Did you apply them correctly? Another key point is the mesh: it must be fine enough in critical areas to ensure the analysis is accurate.
Always check your results against the basic laws of physics; for example, by making sure that the sum of forces or moments equals zero, as Newton’s laws dictate. One of the common mistakes is forgetting to change units. Make sure your whole model uses a consistent system.
Practical application of FEM results
A concrete case could be the design of a bridge. You use FEM to simulate traffic loading. You observe an intense concentration of stresses in the lateral portals. With this information, you decide to reinforce these critical points or select a stronger material there. This ensures that the bridge can withstand the expected traffic without risk of structural failure.
As a general rule, simulations are guided by specific standards, such as the Eurocode for structures. When interpreting the results, you must make sure that stresses and temperatures do not exceed the limits set by the applicable regulations.
Having good fundamentals will help you interpret the results with judgement and make the necessary adjustments to the design. Whether you are an experienced engineer or someone just starting with FEM, a deep understanding of the results can make a difference to the quality of the final project.
Frequently asked questions about FEM simulations
What does colour mean in the visualisation of results?
The colours in FEM visualisations usually indicate the magnitudes of certain parameters, such as stresses or displacements. Red indicates high levels, while blue indicates low levels.
How can I improve the accuracy of my FEM simulation?
Make sure you use an adequate mesh, define the boundary conditions correctly and make sure the material properties are accurate.
Is it necessary to validate FEM results with physical tests?
Yes, it is always advisable to validate your FEM simulation results with real tests whenever possible, to ensure that the model behaves as expected in the physical world.
