Experimental investigation of forming AISI 304 stainless steel sheets using high water pressure

In this study, the water jet incremental sheet forming (WJISF) process of AISI 304 stainless steel sheets was experimentally investigated. The primary objective was to study the effects of key process parameters, including pump pressure, nozzle feed rate, sheet thickness, and the type of backing/support material, on the final characteristics of the formed part. A full factorial design of experiments (DOE) was employed to ensure accurate experimental planning, and the results were evaluated using analysis of variance (ANOVA). Experiments were conducted on sheets with thicknesses of 1 and 1.5 mm, using two different auxiliary materials to enhance the energy transfer of the forming jet. The experimental results showed that pump pressure and nozzle feed rate are the most influential parameters on forming depth. Specifically, increasing the pressure from 70 to 80 bar resulted in a 37% increase in forming depth, whereas increasing the feed rate led to a reduction in the final forming depth. Furthermore, it was found that the nozzle diameter and the type of backing material have a direct influence on surface roughness and wall flatness. The application of molten copper slag as a backing material reduced bottom thinning, while the use of sand resulted in a decrease in deformation depth. Overall, the results indicate that water jet incremental sheet forming is an effective, flexible, and non-contact sheet metal forming technique, which can be considered a suitable alternative to conventional mechanical incremental forming processes such as single-point incremental forming (SPIF) and multi-point incremental forming (MPIF).