How to Decide Element Size in FEA?

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How to Decide Element Size in FEA?
The size does matter.

➛ Creating a high-quality mesh is one of the most critical factors that should be considered to ensure simulation accuracy.

💡 Coarse meshes may give inaccurate results if the stress gradients are too large for the elements to capture properly, For complex geometries, the determination of the element size may not be straightforward, but a reasonable estimation will generally be sufficient for the initial mesh sizing.

💡 Too small of an element size will unnecessarily increase the computation costs and solution times, Mesh influences the accuracy, convergence, and speed of the simulation. Computers cannot solve simulations on the CAD model’s actual geometry shape as the governing equations cannot be applied to an arbitrary shape.

💡 Element size is a significant metric used to control accuracy (element type and shape also affect accuracy). Assuming no singularities are present, a very fine mesh will produce results with high accuracy.

💡 Local mesh refinement in the critical area is the best option to choose for good quality results and control over the total number of node counts, we should be able to test the convergence of a model by refining the mesh only in the regions of interest, and retain the unrefined (and probably unconverted) mesh elsewhere. We should also have transition regions, from coarse to fine meshes, suitably distant from the region of interest (at least 3 elements away for linear elements).

💡Creating quality mesh is all about balancing accuracy versus computational expense. More elements mean that more equations need to be solved at each time step, increasing both solution time and memory requirements.

💡 FEA engineers can restrict areas of high mesh density to areas of interest in their analysis. This is usually confined to areas in the load path of the model, where there is a significant stress level.

➤  A practical way of deciding element size is :

★ Based on previous experience with a similar type of problem (Successful correlation with experimental results).

★ Type of analysis: Linear static analysis could be easily carried out quickly with a large number of nodes and elements but crash, nonlinear, CFD, or dynamic analysis takes a lot of time, keeping control of the number of nodes and elements is necessary.

★ Hardware configuration and graphics card capacity of the available computer an experienced CAE Engineer knows the limit of the nodes that can be satisfactorily handled with the given hardware configuration.

💡 While the proper element size may not be known before the solution, there are post-processing settings, such as results averaging and nodal differences to check the appropriateness of the element size specified.

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