Revisiting Formability and Failure of AISI304 Sheets in SPIF: Experimental Approach and Numerical Validation

Single Point Incremental Forming (SPIF) is a flexible and economic manufacturing process with a strong potential for manufacturing small and medium batches of highly customized parts. Formability and failure in SPIF have been intensively discussed in recent years, especially because this process allows stable plastic deformation well above the conventional forming limits, as this enhanced formability is only achievable within a certain range of process parameters depending on the material type. This paper analyzes formability and failure of AISI304-H111 sheets deformed by SPIF compared to conventional testing conditions (including Nakazima and stretch-bending tests). With this purpose, experimental tests in SPIF and stretch-bending were carried out and a numerical model of SPIF is performed. The results allow the authors to establish the following contributions regarding SPIF: (i) the setting of the limits of the formability enhancement when small tool diameters are used, (ii) the evolution of the crack when failure is attained and (iii) the determination of the conditions upon which necking is suppressed, leading directly to ductile fracture in SPIF.