ABAQUS 1D explicit beams assembly simulation problem (seems to be a simple fix but im stuck)

[H_saywhat]

Hello everyone, hope you're all doing well in this current situation, as well as your loved ones! Hope you can help me as i'm really stuck on this one.

Im applying a vertical and horizontal load on an ABAQUS 2D beam assembly as shown. I need it to be at the red point that is under the model as can be seen in one of the images, and want that point to transfer the load applied, including its moments, to the horizontal beam untop of it. I’ve done that by using an MPC constraint at that point that I specified as a Reference Point and applied two loads on the Reference Point that I have defined, as you can see in the attached image. I keep getting this error when running the job: “Too many attempts made for this increment”. I have tried to reduce the initial step time and increase the mesh, to no avail. Is there anything i’m missing here? the loads I applied were concentrated forces on the RP-1. Should I be placing boundary conditions on the axle to which the RP is constrained to? (which doesnt make sense in my opinion). Do note that when I applied loads on the axle right away as a line load, the job ran perfectly.

P.s. what im working on is a landing gear assembly simplification for the DHC-6 nose landing gear. The lower horizontal beam is the wheel axle, and RP-1 is the point of contact of the wheel with the landing strip. The two forces I applied are the drag force and vertical force on impact. I'm using a general static step.

 

[FEA way]

Are there any additional errors in msg and dat files ? How did you define this MPC between the axle and reference point ?

 

[H_saywhat]

I do keep getting this message in the msg file for the job:

***WARNING: SOLVER PROBLEM. NUMERICAL SINGULARITY WHEN PROCESSING NODE
ASSEMBLY.1 D.O.F. 4 RATIO = 4.64480E+15.

I defined this MPC between the axle and reference point by specifying a set of nodes on the axle then defining an MPC Beam constraint between the reference point and the set of nodes on the axle.

 

[FEA way]

This message means that there’s an instability in the model. Check the node indicated in the message.

So when you apply load directly to the axle, leaving all other settings (including connectors) unchanged, then the simulation works, right ?

Try applying the MPC Beam constraint directly to the geometry of the partitioned segment of the axle (without using node sets).

 

[H_saywhat]

Thank you so much! Yes, when I apply it directly to the axle, the simulation does work. I have already tried to apply the MPC Beam constraint directly to the geometry of the partitioned segment of the axle (without using node sets) and got aborted as well. I think what I have to do is prescribe a restraint (x-direction ) to the reference point where I am applying the load. Let me see how that goes.

 

[FEA way]

Could you attach the cae file here ? I would take a look and try to find a reason of this error.

 

[IceBreakerSours]

Some DOF(s) are left unconstrained.

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[H_saywhat]

Hello again, thanks for the FAQ links and the help. I have solved it. I constrained the displacement and rotation at the axle by placing a boundary condition constraining U1 and UR1 at the reference point, and it worked! That should suffice for now, since the simulation is signifying the moment of impact and my next step would be placing inertia and changing the step from static to a dynamic one, to represent taxiing and pushback.