On the Assessment of the Failure Strains in Conventional and Incremental Forming of Polymer Sheets

This article presents an experimental research carried out on polymer sheet deformed by conventional forming, i.e. tensile and Nakajima tests, as well as by single point incremental forming (SPIF). The analysis is performed for polycarbonate (PC) polymer sheet material within the framework developed in previous recent papers of the authors, which the aim of defining a complete testing methodology for assessing formability and failure by necking and fracture of polymeric sheets. In the case of SPIF, truncated pyramid and cone test geometries are selected, enabling a variety of strain states from plane to biaxial strains. The results obtained allow an accurate evaluation and assessment of the forming limits by necking and fracture within the material forming limit diagram (FLD), and also include an analysis of the influence of the process parameters on the formability and failure modes attained in the case of incremental forming.