Hamid Gorji

In this research, an innovative method has been applied to obtain the shape of initial sheet in the forming of different rectangular geometries. So that we can define rules that automatically determine the optimal shape of the initial sheet at different heights. Sensitivity analysis method was used for optimization, and Python software was used to link with Abaqus software. By examining the geometrical parameters and forming pressure, a flowchart was presented to determine the appropriate pressure. By examining the height changes in different geometries, it was found that the optimization reduces the maximum pressure and the maximum radius of the punch, which were obtained by 4 and 8%, respectively. It was found that the difference in the size of the longitudinal and transverse sides of the section has a direct effect on the changes in the node coordinates to plot the target curve and reduces the number of optimization steps. According to the results, it was shown that by automation and determining the pressure flowchart, the shape of the initial sheet can be determined without repeating the optimization stages and experimental tests. It also prevents material waste.

Incremental hole-flanging (IHF) is a process in which a sheet with a pre-cut hole is flanged by the single point incremental forming (SPIF) process. Fracture prediction in IHF, such as SPIF, is associated with many challenges due to the deformation mechanisms. The purpose of this paper is to overcome the existing limitations and challenges, and thus, to predict accurately failure in single, and multi-stage IHF processes. To this end, the modified Mohr-Coulomb (MMC) criterion was implemented using an appropriate user subroutine in a finite element method (FEM) model. The AA6061-T6 aluminum alloy sheet, which has low formability, and is fractured from its free edges in the IHF process, was examined as an example. Initially, a linear damage accumulation law, in which the prediction error is high due to the non-linear stress and strain states in the IHF, was used to predict the fracture. Therefore, in the next step, a non-linear damage accumulation function was utilized. While the non-linear accumulation accurately predicts the single-stage IHF fracture, it is not able to predict the fracture well in the multi-stage IHF. It was observed that in multi-stage IHF, the rate of damage accumulation decreases with increasing the number of forming stages. Accordingly, a new non-linear damage accumulation rule was developed. Experimental and numerical results indicated acceptable accuracy of the proposed non-linear accumulation in the fracture prediction in the single and multi-stage IHF process.