How to get stress results on a node closest to a given coordinate?

Jimmy He

If I have a set of coordinates, how can I locate the node closest to this coordinate and extract the stress results on it? What happens if this node happens to be a mid-side node?

Jimmy He

You can use the following script to get the nodes closest to a set of given coordinates and extract the nodal-averaged stress at those nodes. To handle stress results at mid-side nodes (if those are requested), the elemental nodal stresses at the surrounding elements are first extracted. Those stress values are then extended to the mid-side nodes, and finally averaged to the nodes based on connectivity.

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

#Data sources
dataSources = mech_dpf.GetDataSources(0)

# Get Mesh
op = dpf.operators.mesh.mesh_provider() # operator instanciation 
op.inputs.data_sources.Connect(dataSources) 
my_mesh = op.outputs.mesh.GetData() 
mesh_info = op.outputs.getmesh()

# Create 10 coordinates to get nearest nodes
point_field=dpf.FieldsFactory.CreateVectorField(10,3,"Nodal")
for n in range( 10 ):
    c = 0.1 + n * 0.05
    point_field.Add( n+1 , [c,c,c] )
point_field.Unit = "mm"

# Find nearest nodes
op = dpf.operators.mesh.point_cloud_search() # operator instantiation
op.inputs.search_domain.Connect(point_field)
op.inputs.reference_domain.Connect(my_mesh)
op.inputs.exclusive_search.Connect(True)
my_search_indices = op.outputs.search_indices.GetData()
relevant_node_ids = list( op.outputs.reference_indices.GetData().Ids )
print( relevant_node_ids )


# Get Connected Elements for all nodes requested
all_involved_elements = []
EIDS = mesh_info.ElementIds
NCPF = mesh_info.NodalConnectivityPropertyField
for nid in relevant_node_ids:
    eidx = NCPF.GetEntityDataById(nid)
    all_involved_elements += [ EIDS[_] for _ in eidx ]
print( len(all_involved_elements) )


# Get element nodal stress results
scoping = dpf.Scoping()
scoping.Ids = all_involved_elements
scoping.Location = 'ElementalNodal'

# Stress X direction
stressXOp = dpf.operators.result.stress_X()
stressXOp.inputs.mesh_scoping.Connect(scoping)
stressXOp.inputs.data_sources.Connect(dataSources)
sX = stressXOp.outputs.fields_container.GetData()

#Extend stress result also to mid side nodes
mid_op = dpf.operators.averaging.extend_to_mid_nodes_fc()
mid_op.inputs.fields_container.Connect(sX)
s_field_corner_mid = mid_op.outputs.fields_container.GetData()

# Average to all nodes
op = dpf.operators.averaging.elemental_nodal_to_nodal_fc() # operator instantiation
op.inputs.fields_container.Connect(s_field_corner_mid)
op.inputs.extend_to_mid_nodes.Connect(True)# optional
s_field_nodal = op.outputs.fields_container.GetData()


# Get the averaged stress at the requested nodes
Stress_data = []
for nid in relevant_node_ids:
    S = [ s_field_nodal[_].GetEntityDataById( nid )[0] for _ in range(n_time_step) ]
    Stress_data.append(S)

Mike.Thompson

FYI an alternate way for only a few points is to use a worksheet named selection where you use the smallest distance to a local CS. You can then scope a stress object to that single-node NS.