Numerical analysis of the effect of coefficient of friction on the formability behaviour of aluminium AA1060 in the stretch-forming process

Abstract

In sheet metal forming processes, the success of the forming process depends on several primary parameters such as the geometry of the tool, Sheet Material Properties, and the Friction in the contact area (tool/workpiece interface). In addition, the process parameters like punch crosshead, deformation temperature, surface roughness of both punch head and sheet blank, lubricant state, and the value of the applied load. Friction in the actual contact area plays a significant effect in obtaining a high-quality part and reducing the production cost. The study provides a new idea to specify the suitable Coefficient of Friction (COF) used when forming Aluminium AA1060, taken according to Coulomb’s Friction Law and Stribeck Diagram for different lubricant states. The methodology of this research is based on the finite element analysis using ABAQUS/CAE 2020 of the Nakajima Formability Test for different Coefficients of Friction (COF) that are taken from Stribeck’s Diagram according to sheet material type, where the suitable Coefficient of Friction (COF) that achieves ISO 12004-2 condition to consider the sheet material successful in the test and valid for use in the manufacturing process. Results show that the Coefficient of Friction (COF) significantly affects the Formability behaviour and specifies the Location of Tearing (crack), where at higher (COF), the Formability of Aluminium AA1060 is decreased. The Tearing (crack) occurs near the circumference of the sample. Consequently, the sample was considered failed in the test and invalid to use in manufacturing processes. At the same time, when (COF) is low, the Formability of the sheet material increases, and tearing occur near the centre of the sample apex, so the sample is considered successful in the test and valid to use in the manufacturing process according to ISO 12004-2.