Stress in roll formed steel panels

UBM:
As you already know, the type(s) of materials being formed, bend radii, feed rate, etc. are just a few factors which will affect the mechanical properties of rolled materials.

I have audited a number of roll-forming facilities, most of these companies have gone through a "learning period" with regards to panel fabrication. The panels' geometry is what provides strength (or lack thereof).

An assumption would be made on my part that these panels have been through an engineering review process and/or R&D prior to an expensive start-up operation. Testing would be dependant on the end user, the jursidcition where the panels would be installed, the designers specifications, etc. Typically panels are required to comply with UBC/IBC or AISI criteria which I would also assume is inclusive to the these panels during the design phase.

Normally in the carbon steels when you deform the steel you make it stronger. As long as you havent torn any of the metal, or thinned it too much, you should see a higher strength in worked matl. This strength increase is easily shown with the Rockwell B test. The hardness increase is an indicator that the yeild strength of the metal has increased due to cold working.

Your steel is:

.060" thick and has a yeild strength of 50ksi?

What is the chemistry or spec. you are buying to .

I know that there are some grades of steel that will have a yeild of ~50ksi and an ultimate Tensile strength of 100+ ksi.

If you still dont think that the panels will survive the stresses they will encounter in service than by all means test some of the material after its been formed. I am certain that you see a significant increase in strength.


Nick
I love materials science!

UBM:
I am building Roll Forming Machinery and roll forming is a process where the theory and exact engineering calculations are not aplicable. In the process of roll forming the stress deviates and creates:
SIDE EFECTS OF ROLL FORMING

Side effects can be expected with the first time running the material such as:

 Bow
 Cross bow
 Twist
 Camber
 Edge waviness
 Herring bone effect

Cause of such effect can be as a result of:

 Tight tolerances
 Not appropriate bending radiuses with a respect of material thickness and material properties
 Not sufficient roll tool design
 holes are too closed to the edges in pre-notching and pre-punching stage
 Stress concentration in the material
 Your roll mill is too old and you have difficulties maintaining shafts parallel in horizontal and vertical direction.
 Your roll mill is not set up properly

Solutions for such effects:

 Evaluate the product with all tolerances, holes location, thickness, mechanical properties etc. before offering Roll Forming technology
 Require good roll tool design (to avoid re-cutting)
 Good Roll Mill condition and efficient set up
 Evaluate the work done by each pair of rolls for each pass
 Require side roll passes
 Require strengtheners
Your structural engineers can calculate the moments of bent and draw the diagram based on your structural application,
but final load test is required by your end user
dako@kolev.com