Tuesday, 24th December 2013
What do you ThInK?
In this series named “What do you ThInK?” we challenge you to find and solve model/simulation
errors.
Nr. 8 – Enforced displacement analysis
A student creates a model of a plate with a hole for linear static analysis,
The model is set up with properly assigned material and property with thickness.
The model is constrained ass shown in the image below
Next the student applies an enforced displacement to the model as shown, by changing the load
type to spcd in the constraints panel
On running the analysis the student gets the error that no enforced displacement is applied
On checking he finds that the spcd and spc are placed in the same load collector and
referenced only once as spc in the loadcase.
load
After organizing the loads as shown into another loadcollector called spcd
And referencing the spcd as the load in the loadstep
He gets another error
What do you ThInK?
What’s wrong? What needs to be changed to run this analysis?
analysis
Find a likely answer below
What do you ThInK? Answers
Nr. 8 - Enforced displacement analysis
The reason is that the nodes that are constrained with spcd must also be constrained with spc with
the same dof with the same enforced displacement value
You can see only the spc loadcollector active in the above image
You can see only the spcd in the above image, so in this correct modelling we have the same nodes
constrained the same way with spc and spcd.
The loadcase definition can be the same as below for correct results
Alternatively the SPCD constraints can also be placed in the same collector as the spc and referenced
in the loadstep, the only point to remember is that the nodes with enforced displacement must have
an spc and spcd definition. This will also give the correct results
ve image how the spc and spcd referring the nodes that require enforced
Notice in the above
displacement are placed in the same loadcollector called spcs and they are referenced only once as
spc without any reference for load in the loadstep definition.