Metal that changes color upon impact

[VictorValencia]

Does anyone know of a metal that changes color when struck and eventually goes back
to it's original color? An example of this is a material that is as strong as steel
and when you strike it with a hammer it darkens at the spot of impact and then
returns to its original state after a short period of time (say < 30 seconds).

I'm not even sure if such a material exists that is strong like steel. I know
that piezoelectric materials change color under stress but they're not very strong.
I need something that can withstand a powerful impact.

Victor

 

[cloa]

How about just a coating?

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[1gibson]

To elaborate, how about a thermochromatic coating. A decent impact should create localized increase metal temperature that should show up as a color change.

 

[IRstuff]

How big an impact? I've seen thermal effects on wrecking balls bashing steel reinforced concrete, but that's a different regime and they faded in less than a couple of seconds.

Even with ceramics, which have very poor thermal conductivity, short duration thermal effects fade within about 20ms; this is with a 30mJ laser with 11-ns pulsewidth, which is a peak power of 2.2 MW.

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[VictorValencia]

The force would be about 600N which is about 1350 lbs. A coating is not a bad idea as long as it is tough
enough to withstand repeated impacts (1000's).

Victor

 

[StoneCold]

What about detecting the deflection of the steel on the backside? Like with a force beam sensor, like below.

Regards
StoneCold

 

[VictorValencia]

Interesting idea. The problem is that I can't really change the dynamics of the device being struck
by adding circuitry although it is something to consider.

 

[StoneCold]

There are optical units that don't actually touch the item being measured. I don't know what the cost is though.

Regards
Stonecold

 

[IRstuff]

Over what area? 500N*10um/1ms = 5W, which is not much at all.

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[IRstuff]

What exactly is the intent of this?

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[VictorValencia]

I would imagine that the force is spread over 0.5 - 1 square inch. The application is confidential at this
point so there is not much I can say until I get a patent application in the works. I'd be more than happy
to speak with someone via private email though (vavalencia --at-- gmail.com) if you need more details.

Also, a big thanks to all that have participated in this discussion. I really appreciate the help!

Victor