Two-layer metallic sheets have wide applications in various industries due to their superlative characteristics. This paper presents analytical model to investigate the formability of two-layer sheets based on Marciniak and Kuckzinsky (M-K) method using Barlat and Lian non-quadratic yield criterion. FEM simulation is also performed to calculate the forming limits based on bifurcation theory. Forming limit diagrams (FLDs) and forming limit stress diagrams (FLSDs) determined by analytical and numerical approaches are compared with experimental results of Al3105-St14 two-layer sheet to verify the validity of theoretical models. The formability of two-layer sheet is also compared with the formability of its components. The results show that the forming limit diagram of two-layer sheet is located between the FLDs of separate layers. The effects of the anisotropy and the orientation of layers on formability of two-layer sheet are studied. The higher formability will be achieved in the case of coincidence of rolling directions of layers. پرونده مقاله

In this paper, 5056 aluminum alloy foams with different percentages of calcium carbonate as foaming agents have been produced, and the physical and mechanical properties of the foams have been studied. Quasi-static compression tests have been carried out to determine the mechanical properties of foamed material. The effects of the amount of calcium carbonate on the size of the pores, the minimum thickness of the walls, density, compressive strength and energy absorption capacity of foams have been investigated. The uniform structure of the pores has been observed in foam specimens with 1.5, 1.8 and 2.1 wt% CaCO3. Increasing the amount of CaCO3 foaming agent from 1.5% to 2.1% has increased the average size of the pores by more than 180% and reduced the thickness of cell walls by 90%. So, the density and the relative density of the aluminum foams have been reduced by 28.6%. The results also show that increasing the amount of CaCO3 foaming agent decreases compressive strength, the absorbed energy and the elastic modulus of 5056 aluminum foams. By increasing the amount of foaming agent from 1.5% to 2.1%, the elastic modulus has reduced by about 16%, and a decrease of 21% has been seen in the energy absorbed by the foam at the strain of 0.4. پرونده مقاله