Influence of forming parameters on the mechanical behavior of a thin aluminum sheet processed through single point incremental forming

Abstract

Incremental sheet forming (ISF) is an economical process for batch production. This paper investigates post-forming mechanical properties with an emphasis on the relationship between residual stresses, strengths, micro-hardness and the strain-hardening exponent. Moreover, the influence of important process parameters on the post-forming tensile properties and hardness is analyzed. A Taguchi statistical analysis method is applied to study the effect of forming parameters and identify the best combinations to enhance the mechanical properties of the commercial aluminum. The results reveal that direct relationships exist for the plots of: (i) the strain-hardening exponent vs. the post-necking strain and (ii) difference of post-forming strengths vs. the strain-hardening exponent. Furthermore, the post-forming yield strength can be enhanced by 66.9% through the Single Point Incremental Forming (SPIF). Similarly, the ductility can be doubled by conducting the SPIF after performing the annealing of the as-received rolled sheet. In the present study, parts formed at a wall angle (θ) of 40◦ with a tool diameter (d) of 6 mm exhibit the highest strength. Moreover, most ductile parts will be obtained at ω = 1500 rpm, d = 22mm and θ = 20◦. It has also been shown that the compressive residual stresses are favorable for higher yield strength and improve hardness of the formed parts.