Engineering | Finite Element Analysis | Stress
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An important step in the Finite Element Analysis process is simplification of the part model prior to analysis. There are usually some features on the component, such as small holes and fillets, that are insignificant from the analysis point of view, but which complicate matters during mesh generation. Detail suppression involves removing insignificant features from the model. St Venant's principle states that local stress concentrations have only local effect (usually cause a disturbance no more than three times the objects size), and so do not affect the overall stress distribution within the model. This means that many features such as holes, fillet radii, shoulders, slots, and bosses, can be removed to produce a coarser, less distorted mesh, enabling much quicker analysis, without seriously affecting the overall accuracy of the results. However, deciding which details to remove and which to keep, whilst keeping errors minimal, requires careful evaluation of each feature's shape, size and location relative to the rest of the model.
St Venant's principle states that local stress concentrations have only local effect (usually cause a disturbance no more than three times the objects size), and so do not affect the overall stress distribution within the model. This means that many features such as holes, fillet radii, shoulders, slots, and bosses, can be removed to produce a coarser, less distorted mesh, enabling much quicker analysis, without seriously affecting the overall accuracy of the results. However, deciding which details to remove and which to keep, whilst keeping errors minimal, requires careful evaluation of each feature's shape, size and location relative to the rest of the model.
Designers may also perform feature suppression from within CAD software, removing unnecessary features in CAD before sending the designs to to the analysis environment. This is usually an explicit feature deletion exercise, but in some instances, you may specify which features you would like to ignore, or simply mesh across, if there are meshing capabilities in the CAD package.
If you are interested in the fatigue life of the component then it is important not to suppress features of high stress concentration in areas of high nominal stress. Fatigue induced cracks nearly always originate from small features such as holes and fillets. Examples of how stress concentration is found with hand calculations and how this affects FEA models is included in our Finite Element Course.
FEM Simplification
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