transform static loads from element faces to nodes?

[jaredmagnusson]

Hello,
I'm looking to convert pressures known at element nodes and faces into forces at the nodes (FEA tool I'm using wants nodal values). Getting forces is straightforward at the face centroids (pressure*Area), but robustly getting a "nodal area" is more difficult across different element types and orders. Preferably, I'd like that interpolation to account for and conserve energy using something like weighted areas (shape functions?).

I saw this functionality in v1.1.0 in pyNastran/bdf/cards/loads/static_loads.py for the PLOAD4 card, a method called transform_load. It didn't take into account area weightings (simply divided the total load by number of nodes), but otherwise looked good. Somewhere in either v1.2.0 or 1.3.0 that functionality went away.

What do you think the best approach would be to perform that kind of operation now? I see a more general transform_load now in the loads.py file, but it only works between 2 existing CID, so I don't think that'd work with an element face center. If there's a better way go about this let me know.

[SteveDoyle2]

There is a force to pressure code outside of the total loads summation. The right way to do it is by using the shape functions, but I'm far from an expert in fea theory. Even the loads summation tool ignores the moment generated by pressure. The transform_load method in pyNastran/bdf/utils, but it's used to transform reduced forces/moments.into different coordinate frames.

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On Mon, Dec 9, 2024 at 7:03 AM jaredmagnusson ***@***.***> wrote: Hello, I'm looking to convert pressures known at element nodes and faces into forces at the nodes (FEA tool I'm using wants nodal values). Getting forces is straightforward at the face centroids (pressure*Area), but robustly getting a "nodal area" is more difficult across different element types and orders. Preferably, I'd like that interpolation to account for and conserve energy using something like weighted areas (shape functions?). I saw this functionality in v1.1.0 in pyNastran/bdf/cards/loads/static_loads.py for the PLOAD4 card, a method called transform_load. It didn't take into account area weightings (simply divided the total load by number of nodes), but otherwise looked good. Somewhere in either v1.2.0 or 1.3.0 that functionality went away. What do you think the best approach would be to perform that kind of operation now? I see a more general transform_load now in the loads.py file, but it only works between 2 existing CID, so I don't think that'd work with an element face center. If there's a better way go about this let me know. — Reply to this email directly, view it on GitHub <#812>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAICUWNG34BJR7TCPRPKZBL2EWWKZAVCNFSM6AAAAABTJBBW5GVHI2DSMVQWIX3LMV43ASLTON2WKOZSG4ZDOMZTG44DMOI> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[jaredmagnusson]

Ok thank you. Where's the force to pressure code located?

[SteveDoyle2]

pyNastran.bdf.mesh_utils.force_to_pressure

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On Tue, Dec 10, 2024 at 6:25 AM jaredmagnusson ***@***.***> wrote: Ok thank you. Where's the force to pressure code located? — Reply to this email directly, view it on GitHub <#812 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAICUWI5B2UHUNDBHHOEEE32E32WDAVCNFSM6AAAAABTJBBW5GVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDKMZRG44DGMBUGQ> . You are receiving this because you commented.Message ID: ***@***.***>

[jaredmagnusson]

Thank you