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
We need to understand what decide the strength of a material. Solid are a bunch of small particles (called atoms) tied together. Solid have a relatively rigid structure. Depending on the material, some are somewhat malleable other are not. Those that are not malleable are more likely to outright snap under tension. Those that are malleable can instead deform slightly to prevent breaking. A simple concept of bend or break.
We use metals (in particular steel) because they are quite malleable (they will bend rather than breaking) without being soft. This mean we can build lot of stuff from it without fear of it breaking, and yet we can still make stuff that need to not move too much (like bridges or buildings, or car). But nothing is perfect. The more something is forced to bend, the more thee bonds between atoms are damaged. While bending prevent things from completely ripping apart immediately, it weaken the bond and make breaking more likely. Of course, in many cases, we can keep doing it without problem for a very long time. While it does become weaker, it’s not too impactful in short terms.
But for heavy machinery, most often those that work non stop (Factories, reactors, trains, buildings, etc…) the material slowly become weaker and weaker. That process is called “metal fatigue”.
The best way to solve it simply to smelt the metal back and reforge it. By doing so, all the bond will break and form anew when cooling. You’ll have a brand new piece to work with.
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