Learning Forum

[lorenzo.loria]

Good evening,

I'm working on a thermo-structural analysis in Ansys Mechanical involving two parts: a circular bar and a surrounding structure with a hole to fit the bar. There's a small gap of about 0.1mm between them.

After running the thermal simulation, I brought the thermal load into the structural analysis. My goal is to see how the stress from thermal expansion affects the hexagonal structure once the gap is filled.

I want to specify that in the thermal analysis, I decided to set a "Bonded Contac Region"; even if unrealistic, due to the gap, I thought that this could be fixed by then adding a "Contact Resistance". Instead in the structural analysis, I decided to put a "FrictionLess Contact" since in the future model I need to implement, the parts will not be "Bonded" to each other (no shared topology).

I have a couple of questions to ask:

1 - is Ansys able to understand this type of problem and transfer the mechanical stresses due to the thermal expansion from the bar to the structure once the gap is filled or do I need to set some specific contact condition to do so?

2 - Do you have any suggestions on a better way to set up the problem?

 Thank you in advance for the help.

[peteroznewman]

Is the thermal load a uniform temperature on both parts?  If so, then you don't need a thermal analysis, you can apply that load directly in Static Structural. It is called a Thermal Condition.

If the thermal load is uniform, I recommend you take advantage of symmetry. In CAD, put a plane half way along the length of the bar. Slice the parts in half and discard one half.  Put a plane parallel to the YZ plane through the center of the bar. Cut the parts using that plane and discard one half. Finally, rotate that YZ plane about the bar axis by 60 degrees. Slice the parts using that plane and discard the parts that have the 120 degree angle and keep the 60 degree parts. Now you can use 3 planes of symmetry to support the rod and hex part. You can keep the 0.1 mm gap between the parts. In Mechanical, use a Frictional or Frictionless contact between the two faces with the 0.1 mm gap. Under the Connections folder, insert a Contact Tool. Evaluate the Initial Contact Status and make sure the Contact Status is Near Open. If the rod has a larger CTE than the hex part, it will expand faster and at some temperature, the gap will close and the two parts will induce stress on each other.