Pencil slip in beta-tin single crystals

Abstract

Pencil slip was observed when a punch was pressed over the (0 0 1) surface of a β-tin single crystal. A bulge of similar size and shape as the punch appeared at the opposite surface directly across the thickness of the crystal. Slip line observations inside the sample showed slip activity confined to a cylindrical shell whose inner diameter was the same as the punch and whose axis was parallel to the [0 0 1] direction. The thickness of the slip shell increased with the punching stress and with the ratio between punch diameter and sample thickness. The effects of punching stress on the entering velocity of the punch and on the exiting velocity of the bulge were studied and the results compared with those of impression creep reported previously. The situation in which the bulge was not allowed to form was also studied.