Numerical simulation for thermal and RT forming light sheet materials using a new combined model of M–K theory and shear localization criterion

This paper presents a new approach of combining the Marciniak and Kuczynski (M–K) theory and the shear localization criterion (SLC) to determine the formability of light sheet materials. Due to the difficulty in determining the imperfection orientation under the uniaxial tension conditions, the M–K theory was only used to predict the right hand side (RHS) of the forming limit diagram (FLD), while the left hand side (LHS) of the FLD was predicted by the SLC as it has the advantage of dealing with strain path non-linearities. At the conjunction point between the LHS and RHS of the FLD (i.e. the plane strain conditions where minor strain ε2=0), the critical plane strain was first calculated by using the M–K theory, and it was then used to determine the parameters involved in the SLC. As a consequence, the proposed combined model was employed to predict the formability of two typical light sheet materials, Mg alloy AZ31B and Al alloy AA5754-O, at elevated and room temperature (RT) respectively; the predicted results showed a good agreement with the experimental results. Therefore, the combined model of M–K theory and SLC is able to provide a new effective numerical modelling for formability prediction in the thermal and RT forming of light sheet materials.