Investigation of the Influence of Low Cycle Alternating Bending Loads on the Properties of Thin Sheets Possessing Different Crystal Lattice Structures

Low cycle, alternating bending is a common type of forming during the manufacture and processing of thin sheets. This forming occurs during the rolling-up into and rolling-out from coils, whilst passing through rolling equipment during the etching process, washing, coating, straightening, bending and deep drawing. Investigations of the mechanical properties, the microstructure and texture of sheets made of the magnesium alloy AZ31, technically pure aluminium and low carbon steels were carried out following cyclic bending on a 3-roller bending machine and on an 11-roller straightening machine. A significant influence of this type of forming on the sheet's properties was established, in particular for materials possessinghcp crystal lattice structures. Pronounced anisotropic properties were observed in the latter material which can be explained by the effect of texture softening. This can be attributed to the activation of twin formation mechanisms in the bending direction. The influence of the prior rolling, the bending regime and the annealing was demonstrated on improving the properties of the sheets made of the magnesium alloy AZ31.