Frank L. Chen

Striation formation mechanisms on the jet cutting surface

An understanding of the mechanisms of striation formation on the surfaces produced by abrasive water jet (AWJ) cutting is a crucial step in reducing or eliminating the striations. Various reported investigations and findings in this regard are reviewed and discussed. The sources of striation formation are classified into three groups; namely the nature of the step formation inherent to a jet cutting process, the dynamic characteristics of the water jet, and the vibration of the machining system. It is believed that all these sources contribute to the formation of striations although it is difficult to separate their effects in practice. Recommendations are finally made on the future work and the approaches to reducing or eliminating striations on the AWJ cut surfaces.

The effect of cutting jet variation on surface striation formation in abrasive water jet cutting

Abstract Abrasive water jet machining is an emerging technology which can shape almost all engineering materials, but also produces a characteristic striated surface finish which limits its potential applications. In this study, the characterisation of different materials’ cut surfaces is investigated using a scanning electron microscope. The effect of abrasive particle distribution in the jet on striation formation is detailed. A non-invasive technique: laser Doppler anemometry is used to analyse the abrasive particle distribution in the jet. Furthermore, the mechanisms of striation formation are discussed in detail and an effective striation minimisation technique applied to the cutting process is outlined.

Improving the cut surface qualities using different controlled nozzle oscillation techniques

One of the principle deficiencies of the abrasive water jet (AWJ) cutting process is wavy striations on the generated cut surface in relatively thick workpieces. A desirable surface finish can be obtained only when the thickness of the workpiece is less than the depth of the smooth zone. Due to the limitation of the waterjet pressures from the current pumping technology, minimisation of striations without the sacrifice of the cutting speed and so increasing the smooth zone depth would constitute a marked improvement in the AWJ machining. In this study, different nozzle oscillation cutting techniques were developed to optimise the AWJ machining process. A comparative study was conducted using different surface texture parameters among straight cutting and different oscillation cutting methods under the same input cutting parameters. Detailed analyses of the cutting results indicate that a significant enhancement in the cut surface quality was obtained by using the controlled cutting nozzle oscillation techniques.

Minimising particle contamination at abrasive waterjet machined surfaces by a nozzle oscillation technique

In this paper, the experimental study and microstructure analysis using scanning electron microscope (SEM) and advanced surface analysis techniques were performed to quantitatively evaluate particle embedment at abrasive waterjet (AWJ) generated mild steel surfaces. It is found that particle embedment depends on cutting depth, traverse speed and pump pressure. A new nozzle oscillation technique was applied to the AWJ cutting process in order to reduce contamination by embedded particles. It was found that, under identical input cutting conditions, the particle embedment at the surface could be reduced up to 200% by using the new nozzle oscillation technique compared to the traditional AWJ technique.