If I bend a piece of metal forward and back a bunch of times, eventually it will break even if I couldn’t break it in the beginning. I believe that is due to metal fatigue(?) How does that work? What’s specifically getting “tired”? the chemical bonds? the structural integrity?
Say I have a piece of metal that I bent and unbent thousands of times. If I melt it back and recreate the shape, does the fatigue “go away”? How does it work?
In: Engineering
Metal is a crystal structure. All the atoms line up in neat little rows.
But these rows aren’t perfect, especially where two “crystals” meet.
When you bend and unbend the metal, these tiny tiny little flaws in the crystal end up grouping together. The more bending you do, the bigger these “voids” end up being. As this happens, the metal in the area gets harder but more brittle. It can’t bend as easily because of the voids getting in the way of all the. Structure moving.
Eventually it gets so stiff and so weak that it just snaps.
Just bending it back straight does not fix metal fatigue. The only real way to get the fatigue gone, forever, is heat it back up to where the atoms can move freely and then re-cool it. (Re-smelt it).
It’s all to do with the crystal lattice and how the different areas of Crystal lattice interact.
[interesting paper ](https://www.nde-ed.org/EducationResources/CommunityCollege/Materials/Structure/strengthening.htm)
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