I'd not advise repair, but am interested in the metallurgy of the question. As I understand stress-strain diagrams, after the metal yields, increased stress is required for further strain increases. That is, the metal is now stronger; often referred to as work hardening. I think, at least in theory....
I believe this has been brought up regularly. I wonder though, those stress strain charts fall off very rapidly. How can one determine if the bulge stopped on the safe side of the curve.
Maybe, if a bulged area survives the hammer back that's a bit of indication that it's okay? Seems like it's a technique that's regularly mentioned in the old literature. I'd think modern alloys may behave very differently.
