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

Abstract

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, Δ 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.