Extracting stresses from Python

Question

Hi, 
 I try to extract stress from the python. The extracted results are different from the plots. soilS1 = g_o.getresults(g_o.Phases[- 1 ], g_o.ResultTypes.Soil.SigmaTotal1, 'node' ) . 
 or 
 
 sd1 = g_o.getsingleresult(g_o.Phases[-1], g_o.ResultTypes.Soil.SigmaTotal1, position) 
 
 Could you please help me with this? 
 Thanks,

Stefanos Papavasileiou · Answer

Dear Douglas, 
 Firstly, one difference arises from the fact that you are checking results for stresses that are primarily computed on stresses but via nodes (extrapolated results). 
 You can run the command: soilS1 = g_o.getresults(g_o.Phases[-1], g_o.ResultTypes.Soil.SigmaTotal1, 'stress point') 
 The getsingleresult command works in a different way. You specify a position and the value will get extrapolated from the closest stress points available. 
 Therefore checking stress results on stress points is the most accurate, but when looking at nodes and on a random location requires an extrapolation process which depending on the mesh density may affect the results.

Stefanos Papavasileiou · Answer

Dear Douglas, 
 The difference highly depends on the size of the generated elements. 
 The smaller they are the more accurate the node results will be. I would recommend checking directly on stress points if you want high accuracy on results that are purely computed on integration points, e.g. stresses.