Hi all, I know this is a bit off topic but I figure there must be some overlap with LS Dyna users and I did use PrePoMAX as the preprocessor.
What should be a very simple problem that is driving me completely insane. I can run the main models without a problem. Frankly LS Dyna is much easier to work with in many ways than Calculix but this is just too simple or something.
This little calibration case just won’t run and provide reasonable results. I have tried all sorts of approaches but I just can’t get it to work, generally the rotation at the ends is the problem but in this version, I think the input file syntax etc correct and the model runs but there is no displacement.
I expect the problem has something to do with how I am constraining the ends. (just a simple SPC on a node set does not work, I am trying to use nodal_rigid_body and then constrain the master nodes)
The idea is to determine what the failure strain should be used for MAT24 material (I expect somewhere around 0,22-0,24) so in this case the failure strain is set high to prevent failure.
(I added an “inp” to the end of the file so I could upload it.
Also why do both Ansys mechanical workbench and LS prepost produce files full of syntax errors? Practically for a program as expensive as Ansys, that is just really unacceptable.
I expect to end up working in the text file but would rather start without first hunting for generated syntax errors.
It works fairly well to convert exported inp files from PPM into LS PrePost k files but there are some things, like boundary conditions that are rather different between Calulix/Abaqus and LS Dyna .
Rigid body constraints are risky if you are exporting them from PrePoMax - keep in mind that CalculiX has the ROT NODE, which is not used in Abaqus. Are you exporting the PrePoMax model to CalculiX or Abaqus .inp ?
Hi, I am using calculix inp files at a starting point but replace things like boundary conditions in the text after converting to a K file in LSPrePost.
My problem is something in the LS dyna file and likely has nothing to do with Calculix/PPM. I am just seeing if I can find anyone who knows LS dyna better than I do. the manual is only 1400 pages long and not that intuitive
I am onto a new version if anyone does want to take a look at the file
I converted your file to Abaqus format and there’s an error that nodes 36 and 37 have BCs specified, but these nodes are not active in the model. Aren’t these nodes supposed to be used as reference nodes of rigid body constraints ? They aren’t currently - nodes 1 and 2 are specified as REF NODES.
Perhaps the converter to Abaqus format incorrectly assigned nodes specified as nid2 under *SET_NODE_LIST_TITLE to rigid body constraints instead of their pnode entries. Swapping the reference nodes makes the file run correctly in Abaqus.
But I’m surprised it doesn’t work even if you use regular BCs: *BOUNDARY_PRESCRIBED_MOTION_SET_ID and *BOUNDARY_SPC_SET_ID.
Prescribed motion cannot be applied to more than one node of a rigid body. The preferred method of prescribing motion to a rigid body is via *BOUNDARY_PRESCRIBED_MOTION_RIGID in which the motion is defined with respect to the center-of-mass of the rigid body.
Though nodal single-point-constraints (*BOUNDARY_SPC) on nodes of rigid bodies will internally be converted by LS-DYNA into an equivalent set of constraints on the rigid body’s center-of-mass, the preferred method of constraining rigid body motion is via Card 2 of *MAT_RIGID, or if the rigid body is defined as a nodal rigid body, via *CONSTRAINED_NODAL_RIGID_BODY_SPC. *BOUNDARY_PRESCRIBED_MOTION_RIGID would be another acceptable means of constraining a rigid body (velocity or displacement could be prescribed as zero).
