Size effects in the axial tearing of circular tubes during quasi-static and impact loadings

An experimental investigation is reported into the size effect for thin-walled mild steel circular tubes which are axially split and then plastically rolled up on a conical mandrel when their upper ends were pressed by the cross-head of a testing machine or struck by a heavy mass with impact velocities of 9.0 and 13.5 m/s. The test tubes have scale factors of one, two and four. Deviations of 11-57 percent from the elementary geometrically similar scaling laws are observed in the maximum permanent axial deflection, u(max), tearing length, Delta a, diameter of plastically deformed curls, d, specific energy absorbed, w, and average axial force, F-ave. The material strain rate hardening effect is the main factor causing these deviations. A new scaling law including material strain rate hardening effect is suggested. (C) 2005 Elsevier Ltd. All rights reserved.