How to Calculate Bias Spring and Heating Current for SMA Spring Actuator?

[Luci]

TL;DR

Hi all ! I have to design a shape memory alloy spring as actuator.

Do you have any information's about how to calculate the bias spring or the Force needed ? the current necessary to heat the SMA spring for a 4mm stroke ?
Thank you

 

[Baluncore]

Is this homework?

You have no scale or specifications with your diagram, so the diameter and force of the spring material is not available.

To calculate the current needed to recover the SMA shape you must know it's resistivity and dimensions, thermal capacity and the insulation or heat loss situation. How long will the current pulse that resets the SMA last?

 

[JBA]

Go to the below for a paper on your design issues and required calculations:
https://pdfs.semanticscholar.org/6bba/1636233448a6630bc1f3598c16d70a1951f3.pdf

 

[Baluncore]

Which is ...
"On the Design of a Shape Memory Alloy Spring Actuator Using Thermal Analysis", 2008.