Simcenter 3D Solutions How to determine the accuracy of FEA finite element results?

Simcenter Nastran Simcenter 3D


FEA Finite Element Analysis is an approximate method. Sometimes Users need to determine the accuracy of results i.e. the error of approximation especially in critical locations. Similarly Users sometimes ask about how fine a mesh should be as well as mesh quality like aspect ratio. This FAQ discusses those issues.


The best and easiest way to determine the accuracy of results is to plot the raw, unaveraged and unsmoothed/banded data.  Displacements are continuous across element boundaries i.e. from element-to-element but stresses are discontinuous.  The color bands will be jagged across element boundaries which are edges for 2D elements and faces for 3D elements.  How smoothly the color bands are from element-to-element is a qualitative indication of the accuracy of the results in that location.

First, to plot unsmoothed/banded stress contours in SC3D Simcenter 3D and SC Femap, the location of the commands is as follows:

SC3D:  Results tab, Display group, Banded Display or Menu, Tools, Results, Banded Display

Femap:  F6 or View, Options, PostProcessing, Contour Type, Level Colors

Second, to plot raw/unaveraged stress contours, the location of the commands is as follows:

SC3D:  Results tab, Result group, Average On/Off or Menu, Tools, Results, Average On/Off

Femap:  F5 or View, Select, Deformed and Contour Data, Contour Options, Contour Type - Elemental, Element Contour Discontinuities, No Averaging

Third, about mesh size and element quality e.g. aspect ratio, which are problem dependent, whether or not they are sufficient is determined by the above process.  There's no need to start with an overly fine or well-shaped mesh.  Based on the above the mesh can be refined even locally if needed.

Reference:  None

KB Article ID# KB000122307_EN_US



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