Formability Limits and Microstructural Features of Parts Made by Single-Point Incremental Forming

Abstract

Single-point incremental sheet forming processes represent today a promising alternative to traditional sheet forming operations for producing low batches or even prototypes without the use of expensive dies. Several investigations have been carried out in recent years to study the fundamental aspects of incremental sheet forming operations, with particular attention to determination of material formability. In this framework, the Authors propose to study the material tendency to be formed by incremental forming, called SPIFability, through different indicators, and to evaluate this tendency as a function of the process parameters, with particular regard to the relative velocity between the tool and the blank. Other reported studies — based on both experimental and numerical studies — have tried to give a comprehensive explanation of the deformation mechanisms that arise during incremental sheet forming, and that possibly affect the material formability. However, none of the proposed theories are today fully accepted by the scientific community. In order to study the relevant deformation mechanisms, the Authors propose to analyze the microstructural characteristics of the formed parts by means of optical microscopy and the fracture surfaces by means of scanning electron microscopy. The investigated case study is an axi-symmetric part characterized by a varying slope with depth, made from blanks of the aluminum alloy AA5182. The parts were formed on a CNC machine until the first crack appeared, and then were measured by means of a Coordinate Measuring Machine to evaluate their thickness profile and geometrical parameters.