End distortion on roll formed parts-4

On the outer surface of the channel, stress starts by causing tension at the air bending region, then changes to compression in the contact forming region, and settles to the residual tension after coming out of the forming rolls. On the inner surface of the channel, stress starts as compression at the air bending region, changes to tension in the contact forming region, and settles to the residual compression after coming out of the forming rolls.

Releasing these forces results in a leading end as shown in Figure 2:

• If the action of surface residual stress release and the action of residual moment release are the same amount, the leading end is straight.
• If the action of surface residual stress release is greater than the action of residual moment release, the leading end is flared out.
• If the action of surface residual stress release is less than the action of residual moment release, the leading end is toed in.