Integration of CFD simulated abrasive waterjet flow dynamics with the material removal model for kerf geometry prediction in overlapped erosion on Ti-6Al-4V alloy

Abstract

Complex surfaces in difficult-to-machine materials can be milled by maneuvering the abrasive waterjet (AWJ) according to the local part geometry by suitably overlapping the kerf cross-sectional profiles (CPs). The CP of a kerf milled in a single pass (i.e., trench) and overlapped pass (i.e., cavity) erosion by the AWJ are the building blocks that need to be known apriori for developing a jet path strategy to achieve a complex surface. This demands an efficient model for the kerf CP prediction. The present work proposes a novel framework for overlapped kerf CP prediction, wherein the jet characteristics of the AWJ exiting the focusing tube are evaluated from the two-phase flow computational fluid dynamics simulation coupled with the material removal model developed based on energy conservation principles. Towards incorporating the non-linearities observed in the kerf formation from the overlapped experimental trials into the model for CP prediction enhancement, the following are considered: (i) a hypothesis: ‘secondary erosion by the jet on the previously eroded kerf increases material removal’, (ii) the varying jet-material property of the ductile material (Ti-6Al-4V alloy), and (iii) local particle impact angles. Furthermore, the variation in the above mentioned non-linearities is incorporated into the model under the change in the AWJ conditions. From the results, it is observed that the proposed models predicted (i) the trench CP with a mean absolute error (MAE) of 27 μm, and the maximum erosion depth (hmax) with an error < 2%, and (ii) cavity at different overlaps (7% – 82%) and jet traverse rate (3000 mm/min – 5000 mm/min) with a MAE of 47 μm, and the hmax with an error < 6%. The predicted geometry of the CP correlates well with the experimental ones, with an average R2 of 0.98 and 0.95 in single- and overlapped- pass erosions.