Controlling material flow in incremental sheet-bulk metal Forming by thermal grading

The requirements towards lightweight components and cost-efficient processes call for innovative developments. In the case of load-adapted components with functional elements, incremental Sheet-Bulk Metal Forming (iSBMF) presents a suitable approach. Nevertheless, secondary issues such as an inhomogeneous thickness increase at the sheet-edge are unsolved so far. This inhomogeneous thickness increase leads to geometrical deviations during the subsequent forming of functional elements such as gears. To solve this problem a new process design is proposed which enables a targeted control of the material flow by thermal grading. Numerical modelling of this new process design verifies that a well-designed temperature distribution enables locally controlled yielding. Thus, the conflict of aims among high heating rates and a small heated area is investigated. The required electrical current and contact surface leads to thermal welding of the electrodes. As a result, a stick slip effect between electrodes and workpiece causes an inhomogeneous temperature distribution and impedes reaching the required temperature increase. (C) 2020 The Authors. Published by Elsevier B.V.