Filling analysis and initial sheet geometry design in the radial sheet hydroforming process to produce stepped parts with different geometry by sensitivity analysis method

In this research, for complicated rectangular parts such as oil and gas tanks, and using hydroforming, forming of three geometries of simple, middle-step and the side-step, rectangular cups were investigated, and by examining the effect of geometrical parameters such as pressure, punch radius, and height, change in the initial shape of the sheet and the filling at different heights are compared. Moreover, by performing optimization and increasing the maximum pressure in middle-stepped and side-stepped cups to 30 and 40 MPa, the maximum filling can be increased by 8 and 12%, respectively. Also, by changing the height and drawing ratio in the stepped parts, the optimal shape of the initial sheet changes for conforming the curve of the formed sheet and the modified target contour. This change is variable for the coordinates of the node in the transverse wall, longitudinal wall, and corner radius of the optimal initial sheet.