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Engineering Tools — Convert Nodal Forces to Pressure (00231)
What this tool does
Converts a set of nodal FORCE / MOMENT loads into an equivalent
distributed surface pressure on a chosen patch of shell elements,
preserving total load magnitude and approximate centroid.
Use this when migrating from a coarse RBE-based load application
(forces dumped on a few nodes) to a more realistic
pressure-distributed load (smeared over the contact patch), or vice
versa when you need nodal forces but only have a pressure load
available.
When you want it
- Coarse-to-fine model translation. A coarse model
applied a 1000-lb fastener load as a FORCE on one node; the fine
model has the bolt-head footprint meshed, and you want the load
smeared over the 12-element footprint as a pressure.
- Solver requirement. Some non-linear analyses
prefer pressure loads to nodal forces for contact stability.
- Result interpretation. Pressure-distributed
loads produce smoother stress concentrations around the load
application area than nodal forces.
How it works
For a selected set of nodal forces and a selected patch of shell
elements, the tool:
- Sums the total nodal force vector and the total nodal moment
about the patch centroid.
- Computes the patch's total area and centroid.
- Writes an equivalent uniform pressure on every element in the
patch such that the resultant force and approximate centroid match
the original nodal loading.
The moment about the patch centroid is approximated as zero in the
default pressure mode — uniform pressure cannot produce a
moment without a moment-arm. If the original nodal loading had a
net moment, that contribution is dropped and a warning is logged.
For loadings with significant moments, consider a tractions
formulation instead.
How to use it
- Open from Custom Tools > Load > Convert Nodal
Forces to Pressure.
- Pick the load set containing the FORCE / MOMENT entries to
convert.
- Pick the shell-element patch (a group, a property, or manually
selected elements) where the pressure should be applied.
- Choose the destination load set (existing or new).
- Click OK. The pressure card(s) are written; the original nodal
forces are left intact (toggle a checkbox to also delete them).
Failure modes
- Patch area is zero or non-contiguous. Tool exits
with a warning.
- Forces not in patch normal. Default pressure
assumes load is normal to the patch surface; off-normal components
are projected and a warning is logged.
- Net moment dropped. Logged with magnitude; if
the dropped moment is more than 5% of the force-times-characteristic-
length product, the warning escalates to a confirmation dialog.
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