Abstract
Abrasive slurry jet (ASJ) is a promising technology to process a variety of materials with advantages of high flexibility, no heat affected zone and high cutting efficiency. In this paper, the impressions generated on a quartz crystal specimen by the impacts of micro-particles laden in a water flow and the associated impact erosion mechanisms are presented and discussed in order to effectively and efficiently control the machining quality. Both brittle and ductile mode erosions coexist in the machining process due to the influence of the fluid motion on the trajectories of particles near the target surface. Large-scale craters produced by brittle conchoidal fractures associated with crashed zone, radial and lateral cracks, dominate the erosion process at large jet impact angles while small-scale craters involving micro-ploughing and micro-cutting are produced by the ductile mode erosion at small jet impact angles. The relation between the process parameters and the overall average volume of craters has also been quantitatively analyzed. A combination of small jet impact angle and abrasive particles and low water pressure is preferred for improving the surface quality after the ASJ machining process caused by the more formation of ductile mode induced craters on the target material, but it is at the sacrifice of the material removal rate as well.
Highlights
Erosion mechanisms by the impacts of solid micro-particle are the fundamental of the abrasive slurry jet (ASJ) micro-machining technology
A combination of small jet impact angle and abrasive particles and low water pressure is preferred for improving the surface quality after the Abrasive slurry jet (ASJ) machining process caused by the more formation of ductile mode induced craters on the target material, but it is at the sacrifice of the material removal rate as well
Only a slight increment of the average crater volume is found by increasing the average particle diameter. It has been found from this study that a combination of large jet impact angle and abrasive particles, and high water pressure may increase the material removal rate in ASJ machining of quartz crystals due to large craters caused by the brittle fracture, while a combination of small jet impact angle and abrasive particles, and low water pressure is recommended to improve the surface finish after the ASJ micro-machining process due to the more micro-cutting actions of particles on the target material, but it is at the sacrifice of the material removal rate
Summary
Where ρp and dp are particle density and velocity respectively, vj is velocity of the jet, μ is viscosity of the fluid and Dn is inner diameter of the nozzle It has been found by Humphrey that the smaller values of the particle momentum number means the more tendencies of particles following the fluid streamlines. According to his research it is expected that because of the flow induced particle impact process, erosion mechanisms involved in low pressure ASJ micro-machining may be complicated, and it is necessary to further a fundamental understanding of a micro-particle impact process in order to effectively and efficiently control the ASJ micro-machining quality. The effect of fluid motion controlled by the process parameters involved in ASJ, including water pressure jet impact angle and particle size on the different types of crater formation and overall material removal will be analyzed quantitatively
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