For an idea of what happens with both dents and bulges, see the link below on work hardening. I know people have had certain experiences that might indicate deformed metal is weaker than originally, but it's rarely the case with these soft steels. Many many steel products are not only produced by cold deformation forming, but also rely on the deformation process to strengthen the product.

http://www.engineersedge.com/material_science/work_strain_hardening.htm