Punching of Copper Under Pressure

Abstract

Punching of copper sheet at atmospheric pressure and under environmental pressures up to about 160,000 psi showed the following: The fraction of slug thickness that is burnished is essentially independent of the thickness of the metal specimen; finite pressures can be used for complete burnished punching (about 70,000 to 110,000 psi for the soft copper and about 70,000 to 120,000 psi for the hard copper); hard copper requires higher pressure to achieve the same fraction of burnished zone as soft copper at the lower pressures, but requires the same pressure at higher pressures; and, the effect of clearance is complex inasmuch as small clearance yields larger burnished zones at atmospheric pressure, but the reverse is true at the highest pressures, with a crossover in between at about 70,000 psi.