Unistrut Yield Strength 2

[BSVBD]

Unistrut reported to me that their Unistrut steel is 33 ksi steel that has been cold rolled to 42 ksi.

Does that happen because of compression during the cold rolling process? If not, how, then is 33 ksi steel converted to 42 ksi?

Therefore, can i use Fy = 42 ksi?

I realize i can contact Unistrut, and i have. But, since they do not offer a phone number, their inquiry reply time is undesirable, but, will use as a secondary resource. I also want second opinions from you who may have dealt with this and may have more readily available answers.

Thank you!

 

[Ingenuity]

This may help: Link

 

[KootK]

Does that happen because of compression during the cold rolling process? If not, how, then is 33 ksi steel converted to 42 ksi?

It happens due to cold working as a result of strain hardening of the sheet stock as it's forced to yield during the cold-bending process. It's an interesting thing in that:

1) You yield the plate transverse to the member axis but get to take the increase parallel to the member axis.

2) Technically, the improvement only applies near the corners of the section where the bending has taken place. Although, I suppose, the corners tend to be the most important bits flexurally anyhow.

At least, I find those things interesting.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[XR250]

I thought it was the actual rolling of the sheet to the proper thickness that caused the strength increase, not just the bending operation.

 

[KootK]

That would make a lot more sense. Thanks XR!

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[KootK]

Actually, this blurb from Yu & LaBoube seems to confirm my assumption to some degree (radius dependency etc). I suspect the paper cited at the bottom has the answer but I'm not able to chase down a freebie to check out.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[SwinnyGG]

Whether or not your perceived problem is actually a problem or not depends on whether or not Uni-Strut buys GR33 material at non-finished thickness, rolls it to finished thickness (so that work-hardened properties are present across the full section) and then bends it, or if they buy GR33 at finished thickness and bend it only.

Even if they buy GR33 at finished thickness, perhaps they are seeing some increase in properties due to the straightening portion of the rolling mill process?

Either way, unless you can get video or actual experience in front of their rolling mill, it would be hard to know.

Edit: There is onne more possibility; is the localized Sy in the strain-hardened areas of the finished channel actually >42 ksi, while 42 ksi represents a calculated yield stress due to test loads across the section?

Once again, hard to know.