Improving Hole Expansion Ratio by Parameter Adjustment in Abrasive Water Jet Operations for DP800 05-11-03-0023

The use of Abrasive Water Jet (AWJ) cutting technology can improve the edge stretchability in sheet metal forming. The advances in technology have allowed significant increases in working speeds and pressures, reducing the AWJ operation cost. The main objective of this work was to determine the effect of selected AWJ cutting parameters on the Hole Expansion Ratio (HER) for a DP800 (Dual-Phase) Advanced High-Strength Steel (AHSS) with s₀ = 1.2 mm by using a fractional factorial design of experiments for the Hole Expansion Tests (HET). Additionally, the surface roughness and residual stresses were measured on the holes looking for a possible relation between them and the measured HER. A deep drawing quality steel DC06 with s₀ = 1.0 mm was used for reference. The fracture occurrence was captured by high-speed cameras and by Acoustic Emissions (AE) in order to compare both methods. Results indicated that using, regardless of the material, a small standoff distance, high water pressure, and slow traverse speed and cutting the sample underwater will delay the fracture in a hole expansion operation. Furthermore, the AE have proven to be adequate to measure cracks when optical methods are not feasible. In conclusion, based on the impact of the aforementioned parameters, it is possible to select, appropriately, the AWJ operation parameters to achieve the edge stretchability required for each forming process.