Search

The abrasive flow precision machining method is used to smooth the inner wall of the valve sleeve. A method to control the quality of the inner surface of the valve sleeve for precision machining by the abrasive flow was established. Through the method of large eddy simulation and a reasonable sub-grid model, the processing pressure and abrasive particle size are selected to perform numerical simulation analysis on the inner surface of the abrasive flow processing valve sleeve to predict the material removal efficiency and surface processing quality. Analyze the influence of wall shear force, dynamic pressure, particle pressure, and the existence of vortex on particle flow under different processing pressures and particle sizes. The mechanism of precision machining of the inner wall surface of the valve sleeve by abrasive flow is obtained. The experiment of abrasive flow precision machining was carried out by response surface methodology. The results show that the processing pressure and the number of abrasive mesh have a significant impact on the abrasive flow processing. Through the quadratic response surface plot and contour plot, it is found that the roughness has a minimum point and the best process parameters are obtained. The inner wall surface roughness value of the valve sleeve after precision machining by an abrasive flow can reach 0.218 μm. Finally, the roughness prediction model is established by the method of variance analysis, and the quality control method of the inner wall surface of the valve sleeve is obtained by abrasive flow processing. [ABSTRACT FROM AUTHOR]

Although abrasive flow technology is a non-conventional approach to finishing in precision machining, it offers particular advantages when machining micro-hole workpieces. This paper combines theoretical, numerical, and experimental methods to study the use of abrasive flow technology in this way. The nature of the collision of abrasive particles with a workpiece is analyzed to reveal the exact mechanisms involved in removing material using an abrasive flow. The experimental results show the importance of the plowing effect of the abrasive grains on the surface of the workpiece. The results are discussed in relation to the surface morphology of the workpiece before and after the application of the abrasive flow. After abrasive flow machining the surface roughness values were greatly reduced, achieving measures of between 0.418 and 0.285 μm in some areas. It is concluded that abrasive flow technology holds great promise for the production of high-quality workpiece surfaces in precision engineering. The results of this research offer particular insights for the further development of abrasive flow technology. [ABSTRACT FROM AUTHOR]

Multifunctional sorbents, activated carbons (AC), were prepared by one-step microwave activation utilizing peanut shells and sunflower seed husks. The influence of the original particle size of raw materials on the yield and specific surface area of AC was studied, which reached 33.5 % and 1133.27 m/g, respectively. The repetitive and competitive uptakes of perfluorooctane sulfonate (PFOS) and chromium were applied to investigate the sorption properties of AC. The sorption mechanisms were demonstrated using sulfur K-edge X-ray absorption near edge structure analysis (XANES). In the repetitive experiment, AC made from peanut shells (AC) still retained 70 % removal efficiency of PFOS after the fourth sorption because sorbed PFOS might form a new organic phase that supplied effective sites for the hydrophobic partition of PFOS. However, the removal efficiency of Cr(VI) decreased dramatically from 60 to 11 % after the fourth uptake because electrostatic attraction was its only removal pathway. In the binary solutes system, AC possessed perfect sorption performance for both PFOS and Cr(VI), which were 885 and 192 mg/g, respectively. In the multivariate solutes system, the XANES spectra indicated that the thiol functional group existed in the resulting AC and a metal chelate was formed between thiol and Zn/Cu. Hence, the presence of Zn/Cu further promoted the removal of PFOS and Cr(VI) through the electrostatic attraction between the anions and positive metal chelate. [ABSTRACT FROM AUTHOR]