Ballistic and Metallurgical Investigation of Helmets Edge-Annealed in a 'Tocco' Induction Heating Unit

摘要

The edge annealing of the entire circumference of the M1 helmet in a 'Tocco' induction heating unit was found to satisfactorily stress relieve the edge. Ballistic testing of the edge annealed zone and the transition zone show ballistic characteristics identical to those of un-annealed helmets. No tendency towards crack fromation exists. Ninety degree band tests reveal the improved ductility of the annealed zone. Hardness surveys and metallographic examination indicate a zone of completely recrystallized, dead-soft metal at the edge of the helmets.