Peened pistons

[NoHaveMSG]

Originally Posted by Ultramaroon

Ball bearing races last as long as they do because they are shot peened before they are ground to final shape.

It's another form of work hardening. All metals solidify as disorganized seeds of highly organized crystalline structures. Those grains grow into each other and remain attracted to each other less tightly than the crystals themselves. they can be displaced from each other only a certain amount until they slip and don't return to their original positions before the force was applied.

The further these grains are displaced from each other permanently, the more force it takes to reach the point where they slip again. This only goes so far before the bonds break down, but up to that point, the material is harder than it was before it was "bent."

Shot peening bends all the grains near the surface but leaves the layers underneath at rest. This increases the hardness of the surface layer relative to the desired hardness of the base material.

Metallurgy is always fascinating to me. It seems counter intuitive that the outer layer be under residual compressive stress to improve fatigue strength until you hear what’s happening at the level of the crystalline structure. We are looking at buying a shot peening machine to improve the fatigue strength of our springs.


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[Ultramaroon]

Originally Posted by NoHaveMSG

We are looking at buying a shot peening machine to improve the fatigue strength of our springs.

Ooo! There you go!

[Stonehorsw]

Originally Posted by NoHaveMSG

Metallurgy is always fascinating to me. It seems counter intuitive that the outer layer be under residual compressive stress to improve fatigue strength until you hear what’s happening at the level of the crystalline structure. We are looking at buying a shot peening machine to improve the fatigue strength of our springs.


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I learned about shot penning in a different way from what was written on the article that someone added. In the version I heard was that some industries in England started observing that some spring manufacturers that took less care of the packaging (therefore l, springs would hit each other), had a longer life. From this observation, they started investigating and then there were several methods developed to do this.

Shot peening is highly used in springs and also steering parts. There are other methods for hardening the surface and keeping the core more flexible.

[Ultramaroon]

Re-read again from the top. Realized I had forgotten about the page that @NoHaveMSG linked. Oh well, you all got to read my redundant take on it.

[NoHaveMSG]

Originally Posted by Ultramaroon

Re-read again from the top. Realized I had forgotten about the page that @NoHaveMSG linked. Oh well, you all got to read my redundant take on it.

Redundant explanations are always good. I can't count the number of times I read one take on something and didn't fully understand it, but another read through from a different source clarified it