Investigation of the Effect of Grain Size on Forming Forces in Single Point Incremental Sheet Forming

Incremental Sheet Forming (ISF) is one of the manufacturing technologies to produce small batch sized components by moving a small size punch along the user defined path. This paper presents a theoretical, experimental and numerical study to find the effect of grain size on the forming forces in the ISF process. This is necessary as the actual sheets used for forming are not cystallographically uniform but contains some inherent impurities and defects, which leads to increase in hardness and conventional yield stress with an excessive reduction in ductility, which is due to change in grain boundaries. The grain size also increases with increase in temperature. Experiments are performed on samples heat treated at different temperatures and hence, different grains to evaluate the effect on forming forces. It is observed that the increase in grain size results in decrease in the peak value of forming force. An empirical model is proposed, which establishes the mathematical relationship between the forming force and forming depth, with change in grain size.