Prediction Equations Relating High Velocity Jet Cutting Performance to Stand Off Distance and Multipasses

Abstract

A previously derived equation for continuous jet penetration of solids (1) is combined with empirical equation for jet spreading and velocity decay in air. These equations are used to study the effects of stand off distance and multipasses on cutting depth, volume removal and specific energy. Predicted trends are compared with limited published experimental data for wood, limestone and coal. Predicted cutting depths for single and multipass cutting are in reasonable agreement with measurements. Volume removal predictions are lower than measured values because other mechanisms such as brittle fracture and reverse jet flow not included in the present penetration model contribute to total material removal by widening of the kerf beyond the effective jet width. The equations confirm the existence of optimum stand off distance and the benefits of multipasses for certain combinations of jet, material and cutting speed parameters. Numerical values of the governing nondimensional groups for optimum performance are identified for conditions encountered in typical industrial applications.

A study of abrasive waterjet characteristics by CFD simulation

“…For example, the water-particle interaction in the mixing unit is extremely intricate while the ultrahigh velocity and small nozzle and particle dimensions make the investigation of the jet and particle behaviour difficult. Nevertheless, some important investigations have been reported on understanding the AWJ dynamic characteristics for relatively low velocity AWJs and for particular jet cutting status through theoretical [10,11] and experimental [12,13] studies as well as CFD simulation [14,15]. However, research on ultrahigh pressure waterjets and abrasive waterjets to arrive at a comprehensive understanding of the jet properties has received little attention [3,16].…”

Progress in fluidized bed assisted abrasive jet machining (FB-AJM): Internal polishing of aluminium tubes

“…Most of these studies argue over the hydrodynamic characteristics of abrasive jets [7][8][9][10][11][12][13][14]; hence, ascertaining the influence of all operational variables on process effectiveness including abrasive type, size and concentration [7][8][9], impact speed [10], and angle [11]. Other papers found new problems concerning carrier gas typologies, nozzle shape, size and wear, jet velocity and pressure, stand-off-distance (SOD), or nozzle-tip-distance (NTD) [12][13][14]. These papers express the overall process performance in terms of material removal rate, geometrical tolerances and surface finishing of workpieces, as well as in terms of nozzle wear rate.…”

Study on the influence of standoff distance on substrate damage under an abrasive water jet process by molecular dynamics simulation

“…Generally, the depth of cut will almost linearly decrease as the standoff distance increases during AWJ operation [6,7]. In addition, the optimum standoff will occur for material-removal processes, or surface damage of impacted substrates [8,9].…”