Possible bug in dpf.operators.result.element_nodal_forces() in Mechanical scripting

I have a Mechanical script that is intended to duplicate nodal force summation like FSUM in APDL. In my test model, I have several contacts scoped using named selections for which I would like to compute the surface reaction forces and moment (about the global csys). To develop this using DPF, I have force reaction probes and an APDL script which have matching results, yet the DPF script only returns correct results for one of the named selections (out of 5 or 6). The calculation is done by a loop so it should work equally well for all named selections. Would someone please verify the issue that I am seeing and file a bug if one exists?

The Static Structural system in the attached model has the test results and the attached script is what is used to export a spreadsheet to the user_files folder of the Workbench project having the reactions in it.

retrieve_nodal_force_reactions_for_named_selection.py

flanges_w_beam_conns_simplified_2024R2.wbpz

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Comments

Mike.Thompson

Try out this code. The key is to explicitly set the mesh input of the ENFO operator to make sure you only account for the elements you want.

FYI, this output matches the MAPDL values exactly.

import mech_dpf

import Ans.DataProcessing as dpf

mech_dpf.setExtAPI(ExtAPI)

import os


ds = dpf.DataSources(Model.Analyses[0].ResultFileName)

dpf_model = dpf.Model(ds)




time_scoping = dpf.TimeFreqScopingFactory.ScopingBySet(dpf_model.TimeFreqSupport.NumberSets)

print "set number: "+ str(time_scoping.Ids[0])


#Get the dpf mesh

op = dpf.operators.mesh.mesh_provider() # operator instantiation

op.inputs.data_sources.Connect(ds)

dpf_mesh = op.outputs.mesh.GetData()

#get the dpf mesh for the elements you want to use for element nodal forces calculations.

#in this case it is the solid elements of the flange bodies.

op = dpf.operators.mesh.mesh_extraction() # operator instantiation

op.inputs.mesh.Connect(dpf_mesh)

ElIds = ExtAPI.DataModel.GetObjectsByName("SolidFlangeElems")[0].Ids

sub_mesh_scoping = dpf.MeshScopingFactory.ElementalScoping(ElIds)

op.inputs.mesh_scoping.Connect(sub_mesh_scoping)

enfo_mesh = op.outputs.meshed_region.GetData()


#the named selection names to use later in a for loop

ns_names = ['flange_1_mate_nodes','flange_2_mate_nodes','flange2_top1_mate_nodes',

    'flange2_top2_mate_nodes','flange2_top3_mate_nodes','flange2_top4_mate_nodes']


for ns_name in ns_names:

    #mesh scoping for the nodes of the named selections

    mesh_scoping = dpf.MeshScopingFactory.NamedSelectionScoping(ns_name.strip().upper(), dpf_model)


    #ENFO operator

    op = dpf.operators.result.element_nodal_forces()

    op.inputs.data_sources.Connect(ds)

    op.inputs.mesh_scoping.Connect(mesh_scoping)

    op.inputs.time_scoping.Connect(time_scoping)

    #connect the mesh generated from the mesh.mesh_extraction() operator

    op.inputs.mesh.Connect(enfo_mesh)

    #get the ENFO data

    enfo_fc = op.outputs.fields_container.GetData()

    enfo_f=enfo_fc[0]


    #do the summation of the data for total forces.

    sum_op = dpf.operators.math.accumulate_fc()

    sum_op.inputs.fields_container.Connect(enfo_fc)

    fc=sum_op.outputs.fields_container.GetData()

    f=fc[0]


    print ns_name+": "+str(list(f.Data))

Mark_Lytell

Thanks. I will try this code.

A source of confusion has been that in my original code, I have verified that the number of nodes in the mesh scoping for each named selection matches the number of nodes in the corresponding worksheet-based named selection where the nodes are selected. Thus, it seems to me that the ENFO operator should have extracted the correct forces based on the list of node IDs. Also, I was hoping that the named selections wouldn't have to be in the results file since the length and name of them is shortened to 32 characters without spaces, etc., and sometimes we realize that we need a new named selection after a solve.

If an example that matches MAPDL exactly without having the named selections in the results file could be made, I think that customers would really appreciate it.