Hello everyone,
I am trying to solve below problem in ProPomax .
May I know how to apply torsional load which is specified in Load condition 4
Thanks!!
You can use a rigid body constraint to apply a torque to the selected surface (the one that would be twisted normally). It can’t be applied directly because nodes of solid elements don’t have rotational DOFs.
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it seems not simple case even PrePoMax has advanced feature in compression only support or constraint, below similar problem of my approach using rigid body for fast checking. Refine model is required to eliminate over-stiffenning by means of coupling type distribution.
as can be seen, discrepancy is too high and it could be better to represent by truly solid bolt models.
ps. try to eliminate rigid body in bolt model by traction force (opposite sign) or coupling type.
Apply load condition 2 eccentrically
another model approach by couple force but seems too high,
result of full model for comparison (reduced loads):
as in early mentioned, this is not simple case since compression only support lead to lower loads in transferring. Rigid body in plate hole perimeter is way of from contact, couple forces ignore non-uniform stress distribution along thickness. Torque force can switch to fixed support in my models but a problematic to OP global models, the behavior only can be captured by full models.
I would use a shell model to analyse this fitting. In fact the design looks too bulky in the body. I don’t think a full 3D model can provide much more insight in the design of this type of fitting.
is there any example of full model including complete part has been built? interesting how physically tested and torque works in such models.
here you can find the step file for the problem.
I have created a reference point which is the CG for the two surfaces where the bolt is inserted.
and I have created a rigid body with this reference point.
and applied a moment
Is this the right way to apply moment?. Seems like even this option is selected in PrePomax, in input file the moment applied still uses concentrated load (*Cload) card
Yes, that’s how moment needs to be applied. It’s just *CLOAD added to the ROT NODE of a rigid body constraints whose DOFs correspond to rotations about the 3 axes (so 2 means rotation about Y axis).
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is the part with purple colors look like a bolt actually is not? rigidly connected can not represent contact. PrePoMax can generate gap element for compression only in sub analysis. Single bolt contact analysis only required low hardware resource, modeling and setup also can fast and quite easy.
but, all depend on analyst and it’s free to choose any approach by simplification until physically built tested.
All models are equivalent in terms of geometry, mesh, and load (2000Nm) for correct comparison.
From left to right:
Compression Only Support
Rigid
Distributing
Full model
If BC are correctly set up and stud is close fit (which is not the case in your benchmark), Compression Only and Contact should be very close in results as shown.
rough approach i will use are based on Hertz contact bearing pressure distribution at some width, force applied in opposite direction to represent torque.
(image from Wikipedia)