Estimating stress hardening of mild steels

[Myndex]

Hello,

I'm working on a piece of furniture, and according to an FEA study one of the parts (the lower frame) needs a yield strength of roughly 65,000 PSI to pass certain certification tests.

There are two versions of the chair, one made from mild steel and the other from stainless steel.

The lower frame is cut from 3/8" plate, and then formed. The main span of the frame is roller formed to impart a curvature with a radius of 100".

I want to estimate the degree that this curvature increases the yield strength of the material. My guesstimate is that starting with a 50,000 PSI minimum material like A572 grade 50, the forming would take the frame up to the needed strength. But I also wonder how far this forming will take 30,000 PSI material such as Stainless 304.

My expectation has been that if forming from stainless, that I'd have to use 410 so that I can heat treat for increased yield strength. It would be useful to know if this forming would be sufficient (I'm thinking it isn't) so that heat treating is not needed for the stainless version.

Attached in a drawing of the lower frame for reference - I'd appreciate any comments.

Best

Andy

Andy Somers
Myndex Technologies Inc.

 

[CoryPad]

You need to determine the strain imparted to the piece. Then, compare that strain to a stress-strain curve for your material. Then, you will have the increased strength.

Regards,

Cory

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