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I'm having some difficulty with a shrink-fit contact (attempting to use thermal loading to relax the interference)

Question asked by Joshua White on Feb 12, 2015
Latest reply on Feb 19, 2015 by Jared Conway

Hello Simulators;

 

This is my first time posting on the forum, although I am a frequenter.  I have been working with an issue for a little while with no progress.  I am hoping there is just something I'm simply overlooking (a quick fix).  I have confidence in you guys!

 

I am analyzing a coupling/pipe connection for the oil and gas industry.  It's basically an API connection.  I'm doing an axisymmetrically simplified, nonlinear static study.  The threads are mated by load flank and there is some interference built into the study.  I am gradually applying contacts to each thread, but have chosen to move one at a time for now so I can catch any problems immediately as they arise.  After applying the shrink-to-fit contact to the innermost thread (left-most) of the coupling and the pin's corresponding "trough" or root, I ran the study and everything worked fine.  I then proceeded to do the same with the next thread; this is when I was prompted with my error that the incremental strain is too high (along with two other suggestions).  To remedy this, I have attempted to apply a thermal load to allow the coupling to move from an expanded state to a contracted (back to initial) state in which the interference would be built up.

 

I excluded the other component from the analysis so I could see the effects of the thermal load.  I applied my thermal load so the temperature would begin higher than the one I specified as its "temperature of zero strain" and would then decrease to the zero strain temperature.  I also added a moving fixture to the left side of the coupling to move with the thermal contraction so as not to allow stress buildup, although I made it stationary to simplify things.  I then ran the study (again, with the other part excluded from the analysis).

 

The study gave results that the coupling was contracting, but that it was doing so from the zero strain position, thereby ending in strain at a more contracted size.  I have been tampering with this for a while, but I cannot get it to do what I need for it to do.  Is there something I am doing wrong?

 

Please help me out here!

 

Edit:  Still no answer to why the thermal load can't contract the part from a strained, expanded position.  Nobody has experienced this before??

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