Fractographic study of mechanisms of fracture in cropping thin-walled steel tubes

Abstract

Cropping is generally used to obtain metal billets from long bars and tubes. These billets are later formed by means of a wide variety of deformation processes. Cropping is used mainly because of its economic viability and productivity. Various mechanisms of fracture in cropping thin-walled tube are identified by fractographic studies. Tearing and shear patterns are observed which suggest that opening and shear modes of ductile fracture predominate in stainless steel billets produced by cropping. It is shown that fracture in brittle materials used as fillers in thin-walled metallic tubes, such as alumina and glass, originates at mechanical defects such as cracks, pores, and inclusions. Fractographic studies confirm that tube cropping is complex in that it is a combination of different processes such as bending, stretching, and tearing of grains and fibres for a certain depth on both sides of the final separation plane.