Learning Forum

[lcrisostomo9564]

Hi,

I need to define specific transformation temperatures for the martensite and austenite phase transformations of nitinol. When I use the custom material model to implement martensite start temperature, martensite finish temperature, austenite start temperature, and austenite finish temperature, then run my test model I get two errors. Is there something I need to do specifically to user-define parameters to ensure Ansys simulates the correct physics?

[Gaurav Sharma]

Hello,

Have you tried running the simulation without the custom material. If the model ends up with the same error, you need not worry about the custom material at this moment and typically the first step to deal with excessive element distortions here would be to apply the load gradually by increasing the substeps further. In case the element distortion occurs only when the custom material is included, you may focus entirely on the input values used and some more testing using a single element model may help you identify the rootcause. Following tests can be performed:

1. You may like to keep the element at a constant teperature and apply stress cycles only to see if the problem reproduces.
2. Next, repeat the same (iterate) whenat different temperatures
3. Follow the same apporach with thermal cycles applied at different constant stress values.

Considering that SMA is being used, I hope you have already ensured that:

1. Large Deflections are turned ON
2. Newton-Raphson Option is set to Unsymmetric Nonlinear Controls to Unsymmetric