Hello everyone,

I am working on an Abaqus/Explicit simulation of a metal forming (shearing/cutting) process. The setup is as follows:

• Material/mesh: The rod is modeled as a 3D deformable steel part with a ductile damage criterion (while the pipe is a discrete rigid body). Mesh uses C3D8R elements with enhanced hourglass control, distortion control on, and element deletion enabled. All other parts (pipe, tools) are modeled as discrete rigid bodies.

Motion:

• The rod must rotate with the carrying pipe (rotation about the 2-axis) while also feeding forward horizontally.

• A reference point (RP) was created on the pipe end surface, with a coupling constraint applied between this RP (as control point) and the rod end surface. All DOFs were released except UR2, so that the rod rotates synchronously with the pipe.

   

• For the RP, I applied a Displacement/Rotation BC with all DOFs fixed except UR2, and then prescribed an angular acceleration of 16 rad/s² about AR2.
• For the rod’s end surface, I applied a Displacement/Rotation BC with UR1 and UR3 fixed, and prescribed a forward velocity of 45,000 mm/s in V1.

Problem:
During the simulation, the rod undergoes significant unintended twisting while rotating with the pipe. Eventually, the analysis terminates with the error: "Excessive element distortion in element set ErrElemExcessDistortion".

In other words, the rod begins twisting far more than expected, even though this behavior is not physically intended.

Question:
What is causing this excessive distortion in my setup? Is it due to the way I applied coupling constraints and boundary conditions?? What would be the recommended way to correctly impose simultaneous rotation and translation of the rod in this type of cutting simulation?

Any guidance would be greatly appreciated.