Papers by Author: Quan Lai Li

Abstract: Micro abrasive air jet (MAAJ) cutting technology is being increasingly used in the precision machining of hard and brittle materials, due to its distinct advantages of negligible heat effect zone and small cutting force. In this paper, an experimental study on the kerf characteristics, especially for the effect of cutting parameters on the top edge definition, is presented. It shows that the top kerf edge is straight but not sharp. The top edge definition of the kerf improves with a decrease in the air pressure, while the effect of abrasive flow rate and nozzle traverse speed are hardly discernible. The optimum jet incidence angle for highest top edge definition of the kerf is 60°. The results of this paper may be useful for the cutting parameters optimization in the precision three-dimensional micro-structural machining.

Abstract: Micro abrasive air jet machining technology is being increasingly used in the fields of micro cutting. Since the aspect ratio is a major interest characteristics of kerf in micro cutting, an experimental investigation is carried out to study the effect of cutting process parameters on the aspect ratio in this study. It is found that the aspect ratio increases with an increase in air pressure, abrasive flow rate and jet incidence angle, while decreases with an increase in nozzle traverse speed. Furthermore a predictive model for aspect ratio is developed using the dimensional analysis technique. It is shown that the model predictions are in good agreement with the experimental results. The research results may be meaningful to efficiently control the aspect ratio.

Abstract: This paper conducts a study on a precision micro abrasive waterjet (PMAWJ) machining system. A new kind of precision micro abrasive water jet system is designed and tapped. The flux and the flow velocity of the PMAWJ system are tested by experiments. Using the micromachining system, a group of polishing experiments is conducted for two kinds of hard-brittle materials such as silicate glass and silicon nitride. The results show the feasibility and the advantage of the PMAWJ machining system for polishing hard-brittle materials.

Abstract: The abrasive waterjet machining is a powerful tool in processing various materials, especially, for brittle materials, such as ceramic, glass and so on. However, the material removal of a brittle material when impacted by abrasive waterjet is not understood in detail. In this paper, the material removal model in fracture erosion of brittle materials by abrasive waterjet has been developed.

Abstract: In this paper, the impact pressure of abrasives acting on the polished materials was deduced by Field Theory and the model of surface roughness for polishing super hard materials with Abrasive Water Jet (AWJ) was established. The model indicates that the surface roughness increases linearly with an increase in the maximum depth of abrasives indenting into materials and that the relationship between the surface roughness and polishing parameters including water pressure, abrasive pressure, the impact angle, the hardness of the polished material, the elastic distortion of abrasive, abrasive size, abrasive density, nozzle diameter and standoff.

Abstract: The erosion process of abrasive waterjet (AWJ) on target material is very complicated and a complete clear understanding about material removal mechanisms in AWJ machining has not been obtained. In this paper, an experiment study on AWJ machining mechanisms of brittle materials is introduced so as to understand the actions of water jet and abrasive particle in material removal process and some experiment evidences of the change of material removal mechanisms have been obtained.

Abstract: Simulation on velocity field of gas-solid flow in the abrasive air jet nozzle was studied by the computed fluid dynamics(CFD) software. The velocity field of the two-phase flow in the abrasive air jet nozzle can be obtained by means of simulation. The effect of the nozzle diameter on the velocity field shows that the velocity field in the nozzle with a smaller diameter is more well-distributed. The velocity distribution along the nozzle axis and the radial direction of the nozzle outlet was also simulated.

Abstract: The potential of abrasive waterjet technology was investigated as a method to polish Z-blocks of synthetic quartz crystals. The polished surfaces were characterized by surface roughometer and scanning electron microscopy. The main factors affecting the surface roughness and the erosion mechanisms related to material removal were analysed. It is found that abrasive mesh, water pressure and jet incidence angle are the main factors affecting the surface roughness. By contrast, the influence of traverse speed on the surface roughness is small. Under certain controlled conditions, the erosion mechanisms of synthetic quartz crystals are plastic flow, leaving a crack-free surface by low-middle pressure micro abrasive waterjet.