TABLE OF CONTENTS David W.A. Rees
Department of Systems Engineering, Brunel University, Middlesex, UK
Sheet metals used to produce metal cans possess a wide variation in strength and ductility depending upon the components produced from them. Body material requires ductility for ironing and final stiffness. Contoured ends and stiffened tabs require only moderate formability for shallow pressing. This paper examines the properties of two, nominal 3 mm thick materials under simple tension and bulge forming. Tensile strengths of heavily rolled canning steels lie in the range 450 550 MPa with approximately 5% elongation at fracture. Body material displays Hollomon hardening in tension ( n = 0.10) while end material approximates more closely to elastic-perfectly behaviour. Bulging through elliptical apertures provides the hardening parameters in biaxial stress applications where the ductility of each material is extended. In addition to using r-values, the spread in flow curves, found from tension in different orientations, indicates the degree of in-plane anisotropy. Tension and bulge flow curves remain distinctly different. A satisfactory degree of equivalence between them is found from the Hill (1948) theory. However, to improve predicted flow behaviour under uniaxial and biaxial stress states, the Hollomon law should be based upon the acting stress state.
Referring to figure 1a, the rolling direction 1 is inclined at ? to the axis 1' of a tensile test piece, along which the stress is ?. Also, let axes I and II lie perpendicular and parallel respectively, to the direction of a local...
