In Abaqus I need to rotate a curved rod fixed in number of screw heads while the screw heads should not rotate and just translate. In other words, I want to apply the forces applied in x,y,z only to the screw heads to translate and not the rotate. Has anybody done that before?
Hi,
I'm not sure that I exactly understand your question (or rather your objectives), but may be using a rigid body element (RBE) that would only transmit the translational degrees of freedom would work.
The RBE would link a master node (or groupe of nodes) from the rod and transmit the translational displacements to the screw head.
Hello, Laurent,
Think of two boxes that are linked to each other. One is rotating around a point which is not the center of the box so regarding the global coordinate system its angle is changing. At the same time, the second box is linked to the first box and is translating with the first box but its angle with respect to the global coordinate system is not changing. I do not know how to apply it in abaqus but it is simply like two boxes coupled in only x, y and z directions but not the rotations. However, when I apply this in abaqus it is not working. Please let me know if you have any suggestions. Thanks.
That would be as I suggested before, by using multi point constraint equations (MPC). In most software that I'm used to, the most often used MPCs are Rigid body elements (RBE). There is an stiff one (RBE2) which does not allow any relative movements between the master node and the slave nodes, that is the distance between the master and slave remains the same.The other (RBE3), is somewhat flexible and allows some change between the node distances. The farther the nodes initially are, the more 'flexible' the link is. I vaguely recall having seen that for ABAQUS the RBE2 is called 'kinematic coupling' and RBE3 is distributed coupling.
The difficulty here is to make sure that nothing is over constrained, yet ensuring that the master node is correctly 'told how to behave' and the relationship between master and slave node is not ill defined. Conflicts with other boundary conditions should also be checked for.
Otherwise, you might be able to link displacement degrees of freedom through boundary conditions or equations.
Best regards,
Laurent
Dear Laurent,
Many thanks for your helpful answers. There is still an issue that I could not figure out which is that by the use of MPCs in abaqus they are activating from the first step, however I need them to be activated from the second step since I have to translate the rod inside the screw then rotate the rod. How can I use MPCs from the second step. since if I use the MPC from the first step, by translating the rod towards the screw the screw would be translate as well.
Many thanks in advance.
Ardalan
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