Understanding the Calculix .inp

[mainengineer]

Hi,

I'm using FreeCad 0.17 on Ubuntu 18.04 LTS.
I am doing an analysis with pressure on faces of an airfoil. I applied the pressure on the faces and wrote the analysis to the .inp
On a particular face, I applied a pressure of 0.258 kPa.
When looking at the .inp file, I see below:

***********************************************************
** Element + CalculiX face + load in [MPa]
** written by write_constraints_pressure function
** FemConstraintPressure_root_LE
*DLOAD
** FemConstraintPressure: face load
86423,P4,0.000258
86928,P2,0.000258
86946,P1,0.000258
86991,P2,0.000258
87013,P4,0.000258
87039,P4,0.000258
87044,P4,0.000258
(and so on).


When I sum up all the pressures/loads (in the last column: 0.000258), I get 0.648, which I understand is 0.648 MPa (or 648 kPa).
I don't understand how this could be.
If these were just nodal loads, it wouldn't be right because that should sum up to 2.26 N.

Can someone clear this up for me?

[ickby]

moved to FEM forum

[bernd]

for pressure it is easy. You applied 0.258 kPa, your inp file is in MPa. As you will know 0.258 kPa = 0.000258 MPa. Thus in the inp file there is 0.000258 MPa on all elementfaces.

hope that helps bernd

BTW: welcome to the world of FreeCAD FEM

[bernd]

ConstraintPressure = DLOAD in ccx inpfile, which is applied on mesh element faces in MPa

ConstraintForce = CLOD in ccx inpfile, which is applied on mesh element nodes in N

[bernd]

** Element + CalculiX face + load in [MPa]
...
86423,P4,0.000258

oder noch deutlicher ...

Code: Select all

Element, CalculiX face, load in [MPa]
86423,P4,0.000258

[Kunda1]

Also OP should probably use 0.18_pre when for FEM related tasks