Evaluation of the Work-Hardening of Brass Sheets Following Strain Path Changes

The strain paths followed by metals during sheet forming can be quite complex, especially when successive forming steps are involved. The work hardening of metals associated with these strain paths differs from that caused only by monotonic straining, such as simple tension or compression. It is important to have an adequate description of the work hardening of the material under processing, especially when numerical simulations of the forming are used. The experimental evaluation of the effect of strain path changes on the material work hardening is usually performed through tensile testing following the strain path changes. This technique, however, demands complex machining operations of the formed sheets and the imposed strain is severely limited by impending necking. The present paper utilizes simple shear as a tool for the determination of the work hardening of CuZn34 brass sheets following various strain path changes associated with combinations of different modes of deformation such as rolling, tension, cyclic and forward shears. The results indicate that the cyclic shearing delays the occurrence of plastic instabilities for brass previously tensioned, occurring the opposite for final monotonic shearing. These phenomena were correlated with the probable microstructural evolution of the CuZn34 brass.