Titanium alloys are widely used in important structures of aerospace vehicles, but the low thermal conductivity and high chemical activity make them difficult to process. As an untraditional machining technology, abrasive water jet (AWJ) has been proven to be an effective method for this kind of material. Aimed at further improving the cutting performance, reverse cutting with variable standoff distance (SOD) strategy was put forward, and experiments of titanium alloy Ti6Al4V machined by AWJ were conducted. The influence of SOD with different reverse cutting types on the kerf quality was studied to obtain the optimal SOD combinations. Ra, Sa and kerf taper were used to evaluate the quality of the machined surface. Moreover, the results of reverse cutting at the same speed and efficiency and single cutting at the constant SOD were compared and analyzed. It was found that the proposed strategy results in higher kerf quality in the aspect of surface roughness, compared to the single cutting. To be more specific, for the reverse trimming cutting, the improvements of Ra and Sa can reach up to 62.8% and 73.1% respectively under the condition of the SOD of the second cutting is 8mm. Furthermore, the kerf taper can be reduced 26.1% when the SOD of the second cutting is 2mm. With respect to the reverse deepening cutting, even the traverse speed of reverse cutting is set as twice as that of a single cutting, the kerf quality is still better. Additionally, when the SOD of the second cutting is 4mm, the improvements of Ra and Sa can reach up to 51.7% and 14.9%, respectively, and the kerf taper is reduced by 20.2%. This study provides a new method for improving the machined surface quality of hard materials, especially for Ti6Al4V.

No abstract

No abstract

A jet pump is used to transport a variety of working media and is especially suitable for dredged soil transporting. In this study, a three-dimensional numerical study of a jet pump that is used for slurry delivery was carried out. The characteristics of the internal flow field of the mixing chamber with different working parameters were comprehensively analyzed. The results indicate that the pressure of the axial line decreases with increasing flow ratio (ratio of suction flux and inlet flux) while the pressure of the injected slurry shows a downward trend. With the increase in the flow ratio, the pressure ratio (difference between inlet pressure and suction pressure divided by the difference between exit pressure and suction pressure) falls off while the efficiency presents a parabolic distribution. The pressure ratio can be promoted by properly increasing the length of the mixing chamber so that the available efficiency is broadened. When the mixing chamber length is L = 2.5Dn~4.0Dn (Dn is nozzle outlet diameter), the highly efficient area is wide; in particular, when L = 3.5Dn, the jet slurry pump with the highest efficiency of 27.6% has the best performance.

Mr. Ziquan Wu from Shenyang All-Powerful Science & Technology Stock Co., LTD. also made a contribution to this paper regarding to the idea of using abrasive waterjet for rail treatment, shown in Fig. 1.Publisher's note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.