Hello fellow Abaqus users!
I have already constructed a model of two parts that are connected with a pin. In the model there is no physical pin. Two reference points are assigned in the centre of pin hole of each part and each R.P. is kinematically coupled with the surrounding surface. The two R.P.s are then pinned with each other via mpc pin constraint. If nlgeom is OFF, the analysis is completed successfully, but when I use nlgeom ON the increment is reduced and reduced and after 0.12% of the total time minimum increment size limit is reached and analysis shuts. Have anyone had the same problem? Could you think of a parameter that might be useful to check?
Thank you in advance for any answers!
Without seeing the model, it is hard to say. Possibly you reach some kind of instability, e.g. a kind of buckling or unconstrained plastic flow if the model contains plasticity. Check the msg-file for the reason the increments are cut back.
Dear Martin,
thank you for you answer.
There is no plasticity considered in the model.
Hereby I present a view of the model. The two solid parts are modeled with wedge 3D stress elements while the two wires shown in red colour are modeled as beams with B33 elements. The model uses 4 Reference Points. RPs 1 and 2 are used to create the pin between the two solid parts (kinematic coupling constraints) and RPs 3 and 4 are used to provide supports for the beams.
Thank you once again for any help.
It's difficult to say without having the full model. It seems to me that your model is symmetric - if so, there might be an instability with respect to deflection to one side vs. the other.
Thank you for your remark!
I have also checked that possibility and I have assigned as a boundary condition the movement on a particular plane (i.e. XY plane). The Z translational degree of freedom as well as the rotations around the X and Y axes are restrained. Thus the only possible translational and rotational movements are on XY plane.
I have uploaded the input file of a test model I run if you would like to check for more info.
Having a short look at the model, I see that the problem (largest residual force) is at the end-points of the beams. I don't really get how the beams/wires interact with the rest of the model since they seem to run through one of the parts.
Looking at the run with NLGEOM=off, I see that the wires don't just contract/elongate, but they also start to rotate around their support.
I also noted that in the model definition, you constrain DOF 3 of Pickedset28, but in the step definition you don't.
Sorry, apart from that, I've no clue what's going wrong.
Thank you for your feedback! I really appreciate it!
The wires do not interact with the right part (shown in picture above). Thus, for simplicity reasons, they run through the particular part. Regarding the rotation you mentioned, the constraint used for the wires is pin, in order to simulate a particular connection. The main purpose of the wires is to provide a certain degree of stiffness on the left part of the mechanism when it is under load. Finally, regarding the Pickedset28 you mention I am going to check it in order to see why there is no step definition.
Thanks for the help!!!
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