Ok, let’s take it again. I simplified a 3D-case down to 2D by taking a slice perpendicular to one rotation axis through the model. Other axels, being parallel to the slicing surface, disappear in 2D case. Since the model is attached on top of a rigid body, the only meaningful item of it in this case is it’s top surface, which reduces to top line in the 2D slice. Rotation axis reduces to a rotation point (you called it REF node), which I located to (9,0.5) so that there are no cos and sin terms present in rotation lever arms, also didnt take any other linear accelerations than gravity in account. As said, in real world rigid bodies have up to six active DOF:s, as is the situation in my case, the motions and accelerations are spectral, from which we have only “snapshots” from some instantaneous time moments, e.g. totally static conditions. Time is not present, and superposition is valid. Please don’t get confused with possible rotations, they only rotate the gravity vector and the world doesn’t turn upside down in the analysis. Constant velocity does not generate mass forces, so velocities are omitted.

Loads are forces caused by the accelerations affecting on any masses: element integration points, point masses etc. Since there is no angular acceleration load option present in CalculiX, one has either to generate equivalent forces to the masses somehow or manipulate the acceleration routine.

For that purpose I’m studying different options how that could be done. Both user cload and user dload have some necessary parameters and returning options missing from their calls. The more I study them, the more acceleration routine manipulation sounds tempting. What’s your opinion?

With user cload for each node

-How to get the necessary mass information into user subroutine.

-How to get list of all elements connected to a node.

-Calculating fractions of joining element masses. Sounds to be too big job.

-Calculating spatial accelerations and mass forces for the node.

-User cload seems to have idof in call, is it called from CalculiX automatically for all DOF:s?

With user dload for each integration point and point mass

-How to get integration point masses into the routine? Are they in an array in Common area? Haven’t found them. For efficiency, I’d like to use the CalculiX internal mass information instead of recalculating it. By default it must have been done before the steps.

-Calculating spatial acceleration and mass force to the integration point.

-Defining loadtype to acceleration or mass force (if they are available).

-Returning acceleration or mass force.

-How to return acceleration direction/componets? This is not explained in the manual.

Manipulating acceleration routine

One could write own acceleration interpretation routine to feed spatial accelerations into mass force calculation. So far I have consumed about ten pots of coffee browing thrue the fortran codes. Any hint of modules involved would be of great help!