Learning Forum

[geecee]

Greetings everyone 

I am trying to run the simulation to calculate the fatigue life of nitinol wire for this i need to impart the strain on the wire by varying the mandrel diameter which has an oscillating motion.  I am attaching the picture of the experimental set up can anyone help me with how to capture the oscillating motion of the mandrel.

[peteroznewman]

Please reply with a schematic drawing and label the mandrel, and the wire.

I see a rectangular bar that oscillates vertically.  There are a couple of posts on that bar.  Does the wire pass between the posts?  Is that what you mean by mandrel?

[geecee]

I apologize for the confusion. I am attaching pictures of experimental set up. The main idea is to impart the strain from the vertically oscillating bar by varying the diameter of mandrels and to estimate the fatigue life of the wire, can anyone help me to understand

1) how can I capture the motion of vertical bar which is driving force in imparting strain on wire

2) how can I set up my wire model so that it accounts for the possible bending

 

                                           

[peteroznewman]

It looks like you have a fixture that will measure the fatigue life of the wire. 

What do you hope to add by trying to simulate what the fixture is doing?

In order to predict a fatigue failure of a part, you need fatigue data on the material from a fatigue testing machine. Do you have that data for nitinol wire?

[geecee]

 Thank you very much for your kind reply yes I do have the fatigue data from flex bending fatigue  testing machine. Now, I want to run fem simulation to estimate the fatigue life of wire 

can you give me head start on how to set up boundary conditions so that it accounts for

1) vertically moving bar which imparts strain( couldn't do this in static structural)

2) how can I set up boundary conditions of wire so it is fixed at both the ends but it allows for bending in the middle?

 3)how can I include the effect of non- metallic inclusions(microscopic defects) on wire can I do this in Ansys?

1

 

[peteroznewman]

Assume symmetry and cut the model in half. Now you have a face on the wire that has a symmetry boundary condition.

You can have contact between the wire and the half mandrel.

The half mandrel can move vertically in a Static Structural model.

You can have contact between the wire and a roller nip off to the side.

You can apply displacement to the end of the wire on the far side of the nip to keep it level while allowing it to be free along the horizontal.

You can apply a horizontal force to the end of the wire to create tension in the wire.

[geecee]

Thankyou very much i will work on it