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 = 22 mm 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.
Highlights
The design and manufacture of various industrial components, especially those using sheet forming processes, heavily rely on the knowledge of material tensile properties
Amongst the parts made from the annealed sheet, the highest strengths and the percentage differences of the yield and the ultimate strengths, keeping the annealed sheet as a reference/σannealed are exhibited by Tests 7, 8 and 9
This study has focused on the processing of the commercial aluminum sheets through the Single Point Incremental Forming (SPIF)
Summary
The design and manufacture of various industrial components, especially those using sheet forming processes, heavily rely on the knowledge of material tensile properties. These properties, e.g., yield strength, are used as design inputs to calculate the various important outputs, such as safety factors, load carrying capacity and deflections, etc. The tensile strength may serve as a basis for the determination of the onset of the plastic instability and give an insight into the necking or the initiation of the fracture It serves as a basic input to find the forming force in the conventional forming processes such as the deep drawing and the stretch-bending. The ductility (measured in terms of percent elongation) or the strain-hardening exponent may be employed in several forming processes, e.g., stamping, hydroforming and incremental sheet forming (ISF) as an indicator of the formability [2]
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