I want to calculate the equivalent stress for an elasto-plastic analysis.Which is the correct way to do it:
1) Calculate stresses at each Gauss Point and then evaluate equivalent stress at each Gauss point or
2) Calculate stresses at each Gauss Point,extrapolate stresses at element nodes and then evaluate equivalent stress
Both the methods are used in practice. To extrapolate the stresses at nodes, one can first compute the stresses at gauss points. There are various methods of extrapolating. However, stresses at nodes are usually of more interest and commercial software by default provide extrapolated values. One of the reasons for more interest in nodal stresses is that nodes can be located on the surface where the stresses can be usually higher than the interior. Note that while computing the nodal stresses by extrapolation, elements sharing a node usually do not predict the same stress.
Commercial FEM codes do method 2).
Otherwise you need to provide also the coordinates of Gauss points, where the stress has been computed
Dear Eirini Pitsiougka
Commercial FEM codes do method 2 because these method is more reliable and It is more in line with reality.
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