Abaqus FEA Problem - Displacing an Entire Part at Once

[tomtom412]

Hi all,

I have a personal project I am working on in Abaqus CAE/Explicit 2017. I have a tube, that I am trying to advance into a larger tube with a bend in it. The idea is that the small tube enters and then deforms around the bend as it comes into contact with the radius of curvature of the larger bend.

The problem I am having is that I do not know how to displace the smaller tube a fixed distance. I had applied a displacement/rotation to the proximal end, hoping it would advance the entire part along the distance specified. However it simply "crushed" the prox face in on itself, not moving the entire part; even though there were no boundary conditions on the distal end, i.e. fixing it in place etc..

Is there a function I am unaware of that will do this for me? My goal is to measure the stress distributions in the tube as it deforms around the bend.

Any guidance at all would be greatly appreciated, I have a decent understanding of most aspects of the software from college work, but this is throwing me big time!

Thanks in advance!
Tom

 

[jrmichler]

I had similar problems when using ABAQUS to model sheet metal forming. I was modelling the process of pulling a strip of sheet metal through a test machine. I started by defining a velocity for the end nodes of the modeled strip. That blew up right away. The root problem is that, in FEA land, the part being modeled has exactly zero damping between each and every node. I pulled the end nodes a distance of (velocity X time step), which created a large strain (and stress) in the end elements after the first time step. At the second time step, the second row of nodes jumped forward because of the high stress, and the whole process went into positive feedback. I ended up pulling the strip through a spring and dashpot to make the model work.

Take hard look at your material density, element sizes, velocity, and time step size. You could be inadvertently hitting the end of your tube at high velocity before the rest of your part has a chance to move.