Small-Scale Morphological Features on a Solid Surface Processed by High-Pressure Abrasive Water Jet
Being subjected to a high-pressure abrasive water jet, solid samples will experience an essential variation of both internal stress and physical characteristics, which is closely associated with the kinetic energy attached to the abrasive particles involved in the jet stream. Here, experiments were performed, with particular emphasis being placed on the kinetic energy attenuation and turbulent features in the jet stream. At jet pressure of 260 MPa, mean velocity and root-mean-square (RMS) velocity on two jet-stream sections were acquired by utilizing the phase Doppler anemometry (PDA) technique. A jet-cutting experiment was then carried out with Al-Mg alloy samples being cut by an abrasive water jet. Morphological features and roughness on the cut surface were quantitatively examined through scanning electron microscopy (SEM) and optical profiling techniques. The results indicate that the high-pressure water jet is characterized by remarkably high mean flow velocities and distinct velocity fluctuations. Those irregular pits and grooves on the cut surfaces indicate both the energy attenuation and the development of radial velocity components in the jet stream. When the sample is positioned with different distances from the nozzle outlet, the obtained quantitative surface roughness varies accordingly. A descriptive model highlighting the behaviors of abrasive particles in jet-cutting process is established in light of the experimental results and correlation analysis.
Assessment of cavitation and impingement effects of submerged water jet on Ti alloy surface
Abstract An investigation is conducted to explore the effect of submerged water jet on solid material surface. With jet pressures ranging from 80 to 150 MPa, jet impingement on Ti-6Al-4 V samples is implemented experimentally. Experiments enable a quantitative evaluation of surface morphology features, residual stress and surface roughness associated with the impinged samples. A comparison is performed between submerged and non-submerged water jets. The results show that cavitation phenomenon manifests itself in submerged water jet as a ring-shape cavity zone, and the occurrence of cavitation is confirmed by the surface morphology features and local surface roughness on impinged surfaces. An almost linear relationship between residual stress and impingement time is corroborated. As for the resultant pits on impinged surfaces, smooth perimeters are caused by submerged water jets, while non-submerged water jets give rise to rather irregular pit perimeters along with comparatively powerful impingement force.
Topographic Description of Abrasive Waterjet Machined Surfaces
The present paper is aimed at a multi-parameter surface roughness characterization and modelling via ANOVA and Response Surface Methodology of sheet steel TRIP 800 HR-FH (hot rolled) processed by Abrasive Waterjet Machining (AWJM). The design variables were: nozzle diameter, stand-off distance and traverse speed, and a number of roughness parameters were used as response variables i.e. (ISO 4287) Rt, Rsk, Rku, Rpc, (ISO 13565) ‘’Rk’’ family of Abbott curve parameters, fractal dimension, D and ACF (auto correlation function). The parameters considered showed a varying degree of association with the machining conditions. Representative AWJ machined surface profiles are proved to be: complex in shape (random and periodic), rather empty of material, of medium curvature, of medium peak density, of low complexity and of small bearing capacity at upper peak levels.