Dear Michal,

I suggest that you use one of the two mean stress correction equations: Smith-Watson-Topper or Walker. The references for those equations are as follows:

SWT:

K.N. Smith, P. Watson, T.H. Topper: A stress-strain function for the fatigue of metals. J. of Materials, 5 (1970) 767-778.

Walker:

K. Walker: ASTM STP 462, (1970)1-14.

Good luck.

For the NiTi wires, the fatigue is most cases controlled by the presence of inclusions. It this is also the case for your wires, you can also try to correct the S-N diagram by doing a simple estimation of propagation lifetime. 

This analysis has been presented in: Shape Memory & Superelasticity. The crack growth data were taken by a paper of R. Ritchie.

http://link.springer.com/article/10.1007/s40830-015-0016-1

Dear Sir, 

I want to do fatigue analysis for my model with NiTi as material in Ansys

From where I can get the SN curve value for the same. 

Hello Arvind,

Please have a look at the attached reference materials and let me know if they come in handy in line with your query.

Thanks Jimmy 

Dear Jimmy, 

How to define alternating stress value with no of cycle for NiTi. 

Actually I wanted to do simulation of fatigue life by stress life analysis and for that I need to define SN curve that is alternating stress value with no of cycle to failure. 

Thanks