This idea came to me as I explored ways to make holes on sheet metal to make it lighter. Quite obviously, if the manufactured product has a small thickness, making holes would reduce its stiffness and rigidity. It is also questionable whether the reduction on thin sheets are worth the effort in trying to save weight.
When we look at areas to lighten, we would also need to take into account the loss of this rigidity. This means torsional forces causes material failure. Such was what had happen in the racing scene may years before. The race officials then banned the holes if it was not designed into the production. Steel material would need considerable amount of force to cause it to break. Front bumpers for many years have been intended to be broken and not just dent. A snap of a known material size is equivalent to the accidental forces. Flanging or belling reinforce the strength of that material simply by cold working the holes. The shape of the flange itself is not important. What does effect is the stressing of the material increases its strenght. Much like Reinforced Concrete. The bars are actually strained to increase its rigidity.
This article reminded me of the wooden tools that I used to see when I was in Secondary school. Its quite odd to find such tools nowadays. As the world moves on to machined manufacturing, we loose knowledge on proven skill based method of steel working. I used to think of using the mechanical draw method to make these flanges. This article showed me of the die method using hardwood to form metal which remains an option to me.