SPRINGBACK

[Webster]

Your Google Fu is weak, Grasshopper.

http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392017000501291

or

https://pdfslide.net/documents/the-...ers-on-springback-in-v-the-evaluation-of.html

The study was done on sheet metal, not catridge brass but I would expect it's conclusions to bear some relationship to brass.

Thanx for finding the entire report.

 

[LC Tikka]

Like bending most things cold, you have to over bend a fair amount due to spring back. Holding the material at the peak of the bend or releasing at once really doesn't matter if the final size or shape meets spec, holding the bend just adds time to the process.
L

 

[Brians356]

My girlfriend says to keep it in the die for a full minute.

Did she mention rotating it 180-deg halfway through?
-

 

[Brians356]

The study was done on sheet metal, not catridge brass but I would expect it's conclusions to bear some relationship to brass.

Hmmm, I wonder. We're compressing, not bending.
-

 

[Rocketvapor]

"Hmmm, I wonder. We're compressing, not bending."
Imagine a point on the shoulder to body.
We're sliding that point where?
Or a point on the neck to shoulder.
While maybe less of an angle than bending sheet brass, we do strange things to the shape when we resize.

 

[dcali]

This is for sheet aluminum in a very specific loading condition - I wouldn't count on it being true for brass sizing. The material they've used is nearly pure aluminum with a yield strength that is close to zero that is being bent under very high local stress.

 

[Webster]

This is for sheet aluminum in a very specific loading condition - I wouldn't count on it being true for brass sizing. The material they've used is nearly pure aluminum with a yield strength that is close to zero that is being bent under very high local stress.

The yield strength of Al 1050-0 Alloy is 4060 PSI. I originated the post and I have decided that I have no interest in hold time to reduce spring back in brass a tiny mount. If you size cases the same way each time regardless of the method you get the same results. I don't care if I get 1%, 2% or 2.7% springback. All of my cases get sized the same amount and they don't have to conform to some springback value. My varmint rifles shoot very small groups for what they are. Very few of the non-comp shooters at the range shoot smaller groups than I do with much more expensive rifles.

 

[Gappmast]

My girlfriend says to keep it in the die for a full minute.

or longer

 

[Gappmast]

I have always wondered if vibration like you see in an ultrasonic cleaner would help

 

[TC260]

Like bending most things cold, you have to over bend a fair amount due to spring back. Holding the material at the peak of the bend or releasing at once really doesn't matter if the final size or shape meets spec, holding the bend just adds time to the process.
L

For most practical applications that's definitely true. Reading through the paper, it looks like they're doing the research so designers of flexforming molds can model springback more accurately in FEA simulations in order make molds as accurately as possible in the first iteration to avoid modifications afterward. In college my senior project was on incremental forming sheet metal for the same purpose, to develop data for more accurate FEA models in order to better predict metal forming behavior. Being used to manufacture one-off or limited production parts, there's a strong interest in being able to make parts accurately in the first pass.