Abstract

The process of a cluster-containing water jet impinging on a monocrystalline silicon substrate was studied by molecular dynamics simulation. The results show that as the standoff distance increases, the jet will gradually diverge. As a result, the solidified water film between the cluster and the substrate becomes “thicker” and “looser”. The “thicker” and “looser” water film will then consume more input energy to achieve complete solidification, resulting in the stress region and the high-pressure region of the silicon substrate under small standoff distances to be significantly larger than those under large standoff distances. Therefore, the degree of damage sustained by the substrate will first experience a small change and then decrease quickly as the standoff distance increases. In summary, the occurrence and maintenance of complete solidification of the confined water film between the cluster and the substrate plays a decisive role in the level of damage formation on the silicon substrate. These findings are helpful for exploring the mechanism of an abrasive water jet.

Highlights

  • Abrasive water jet (AWJ) operation is described as the impact or collision process of the mixture of the water column and abrasives or clusters

  • AWJs are widely used in the machining filed, in processes such as abrasive water jet cutting, water jet cleaning, and abrasive water jet polishing (AWJP) [1−3]

  • The cluster surface and the inner surface of the silica pipe wall were composed of silicon atoms, bridging oxygen (BO) atoms bonded to two silicon atoms, and non-bridging oxygen (NBO) atoms bonded to one silicon atom

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Summary

Introduction

Abrasive water jet (AWJ) operation is described as the impact or collision process of the mixture of the water column and abrasives or clusters. Based on the experimental phenomena mentioned above, the studies on the influence of standoff distance on substrate damage were conducted by Kordonski et al They found that because of a combination of the absence of lateral limit by nozzle, surface tension variances, and aerodynamic disturbances, the degree of jet divergence increases progressively with the standoff distance [10] This can make the energy density decrease and eventually lead to a lower jet penetration depth [11]. The mechanism of the collision process between the silicon substrate and the water jet, which contains an amorphous silica cluster under different standoff distances, was studied by molecular dynamics simulation at the nano-scale. The influence of standoff distance on the damage of the silicon substrate would be analyzed through the variance of a five-fold coordination number of silicon atoms

Simulation model
The calculation of local temperature and pressure
The calculation of water film layer density
The calculation of cluster force
Simulation results
Analyses and discussions
Discussions
Findings
Conclusions

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