I want to apply a displacement at each of these three point in a given sequence. For example
hold points 2 and 3 fixed, displace down on point 1, then hold that, displace down on point 2 and hold it there and finally displace 3 down and hold it. I’m displacing 0.1mm in this example and what I would have expected is that the final displacement is 0.1 in Y for example. Instead it looks like that is not how “fixed” works. I started looking for answers and found several posts with similar questions. it looks like the locations just reset:
It seems like one has to change a key word
*Boundary, op=New
to this:
*Boundary, op=Mod
But it is not clear. I’m going to try that now and see if that solves it. the only issue is that one has to run this out of prepomax because the keyword is not modifiable in prepomax as far as I can tell.
I figured it out! Its actually kind of an ignorant move of me to set 3 rigid body points to the same element set. I Separated the rigid constraints into 3 separate ones and that worked. The rod bends one way first, then another way next. Its great.
Yeah, it ignores all the rigid body constraints applied to the same nodes apart from the first one. There are warnings about that:
*WARNING reading *RIGID BODY: dof 1
of node 1 belonging
to a rigid body is detected
on the dependent side of
another equation; no rigid
body constrained applied
Abaqus would throw error messages and refuse to run the analysis.
Yes it did. Probably not exactly what you were looking for since this is only displacements. I didn’t have to use the “Fix” BC. I used displacement BCs set to either 0.1mm or “Fixed” in the vertical direction.
As far as I know, Calculix does not recognize “op=New,” even though it is listed as a valid option in the Calculix documentation itself. Consequently, I chose to omit the optional parameter by simply deleting it, leaving only “Boundary.”
“op=mod” represents the default behavior in Calculix, so it reverts to this mode.
Doesn’t it apply to some old releases of CalculiX ? I’ve seen several cases where there was an expected difference when OP=MOD was used vs OP=NEW (e.g. fixed BC wasn’t redefined leading to non-convergence).
This warning is weird, I will ask Guido if it’s necessary when I contact him about other issues. But apparently it just means that MOD is used by default and doesn’t have to be specified. If NEW is specified then there are no such warnings and a proper change in behavior can be observed. Thus, it seems that it’s all working as it should and maybe just the warning is obsolete or the parameter should be NEW or not added at all (then it behaves like with MOD).
