Current needed to heat nitinol to 70°C

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Hello Members

Im currently working on the material Nitinol, which is a shape memory alloy. Nitionol changes to its permanent trained shape by the addition of heat.

I am currently investigating the effects of Nitinol. In order to heat the Nitinol I plan to use an electric current passing through it. The Nitinol's activating temperature is 70 degrees celsius.

I have extensive material properties of Nitinol and would like some help on determining the current required to heat the material to around 70 degrees.

Thank you Kindly
Any help will be greatly appreciated
 

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neolin said:
Hello Members

Im currently working on the material Nitinol, which is a shape memory alloy. Nitionol changes to its permanent trained shape by the addition of heat.

I am currently investigating the effects of Nitinol. In order to heat the Nitinol I plan to use an electric current passing through it. The Nitinol's activating temperature is 70 degrees celsius.

I have extensive material properties of Nitinol and would like some help on determining the current required to heat the material to around 70 degrees.

Thank you Kindly
Any help will be greatly appreciated

Welcome to the PF.

I googled bare wire temperature versus current, and got lots of good hits. I even got an old PF thread that discussed it, and has some links that may be useful:

https://www.physicsforums.com/showthread.php?t=270177

.
 
Hi ther. Thanks for your reply. I had a look at them and it looks quite complex. I am having a hard time figuring this out but I will look into it further.
 
neolin said:
Hi ther. Thanks for your reply. I had a look at them and it looks quite complex. I am having a hard time figuring this out but I will look into it further.

As mentioned as an option in the thread, can you just run some experiments to make your own table of current versus temperature?
 
From: http://www.nodna.org/product_info.php?language=en&products_id=1493

For example, 400 mA of electrical current through the 6-mil nitinol wire will produce a maximum pull of 11 ounces and full contraction in one second. Reaction time can be faster, in the millisecond range.
To achieve this high current short duration pulses are used.
When doing this consideration must be given to the mass and speed of the material to move.
The faster you move a given mass the greater the inertia that must be overcome.
If the inertia becomes greater than 6 lbs. for the 6-mil wire, it will snap.


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From: http://www.imagesco.com/articles/nitinol/06.html


Direct Electrical Heating Nitinol wire can be activated using a low voltage DC (6-12volts) power supply. A simple circuit can be constructed using a battery, switch and a small length of nitinol wire, see figure 7. When activating a Nitinol wire wire using DC current it is important not to overheat the wire by keeping the current on too long. Overheating the Nitinol wire will degrade its properties. DC current doesn't heat the wire evenly. An electrical circuit that uses Pulse Width Modulation (PWM), shown on the next page, heats the wire more evenly and is better for activating Nitinol wire.


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Note: For futher info please view the above sites. For extended info, I used the following phrase in GOOGLE:
"activating nitinol electricity" without the qoutes.

Hope this helps.
 
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