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Q & A: spring fatigue

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Most recent answer: 10/22/2007
Q:
Can you break a spring if you squeeze it too much (I know you can by pulling the ends to far apart)?
- Owen (age 16)
Chicago
A:
That's an interesting question. Usually coil springs are made with the coils wound fairly tightly. You can't squeeze them very far before the coils bump into each other. That's rarely enough to break the metal.

If you repeatedly squeeze and release the spring, it very likely will ultimately break. Metals that are repeatedly strained will "fatigue", meaning that tiny defects (departures from the regular lattice arrangement of the atoms) in the metal move around and lump up into bigger defects. This process accelerates because a metal that has been strained frequently becomes harder and more brittle, meaning that more force is necessary to stretch it or squeeze it, and more damage is done more quickly. Eventually, the spring will crack if it is fatigued enough. How many squeezes it takes before the spring breaks will depend a lot on how tightly coiled it was to begin with and what metal it was made of.

(published on 10/22/2007)

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