Manufacturers face challenges when dealing with abrasives that lose roundness,wear excessively,and suffer from pitting of the surface of the grinding wheel that needs rectification using dressing techniques.Nanostruct...Manufacturers face challenges when dealing with abrasives that lose roundness,wear excessively,and suffer from pitting of the surface of the grinding wheel that needs rectification using dressing techniques.Nanostructured abrasive grits manufactured by hybrid fusion processes and by sintering/extrusion/printing processes are found to reduce pitting quite significantly.The phenomenon of wheel collapse is increasing and cycle times developed during the grinding of aerospace alloys are much smaller compared to using conventional materials.This paper reviews the phenomenon of wheel collapse induced by pitting and takes a critical look at the production and analysis of hybrid fused and printed/sintered abrasives.A mathematical analysis is carried out of the diffusion of primary and secondary phases due to mechanical and ultrasonic agitation with the aim of producing abrasive grits with improved strength and retention.Current developments in extruded,printed,and sintered grits for use in precision grinding applications are critically reviewed.The paper concludes by explaining how such abrasives are used in practice by industrial manufacturers of high-precision products.展开更多
This study systematically investigates changes in both compositions and grain-sizes of magnetic minerals in the Chinese loess/paleosol samples (Yichuan, China) during thermal demagnetization processes. Between 100 and...This study systematically investigates changes in both compositions and grain-sizes of magnetic minerals in the Chinese loess/paleosol samples (Yichuan, China) during thermal demagnetization processes. Between 100 and 200℃, (1) Hc and Hcr significantly decrease while Mrs and Ms remain stable; (2) concentration of the multi-domain (MD) grains increases while that of superparamagnetic (SP) grains decreases; and (3) there exists the abnormal behavior of the thermal demagnetization in the natural remanent magnetization (NRM). In addition, the corresponding changes in all these parameters are gradually muted with the increase of the pedogenesis degree. The results indicate that the observed alteration probably relates to reducing processes caused by the burning of the organic matter in samples. Before the thermal treatment, the MD grains in loess samples had been partially altered in nature by low-temperature oxidization (LTD). This CRM can be sufficiently attenuated or even removed by the reducing展开更多
基金The author thanks Dr. Subramanian, STIMS Institute (Fig. 1)Dr. Michael Hitchiner of Saint-Gobain Abrasives (Figs. 13-16)Drs. Bhateja and Lindsay of Saint-Gobain Abrasives and SME(Figs. 2 and 3).
文摘Manufacturers face challenges when dealing with abrasives that lose roundness,wear excessively,and suffer from pitting of the surface of the grinding wheel that needs rectification using dressing techniques.Nanostructured abrasive grits manufactured by hybrid fusion processes and by sintering/extrusion/printing processes are found to reduce pitting quite significantly.The phenomenon of wheel collapse is increasing and cycle times developed during the grinding of aerospace alloys are much smaller compared to using conventional materials.This paper reviews the phenomenon of wheel collapse induced by pitting and takes a critical look at the production and analysis of hybrid fused and printed/sintered abrasives.A mathematical analysis is carried out of the diffusion of primary and secondary phases due to mechanical and ultrasonic agitation with the aim of producing abrasive grits with improved strength and retention.Current developments in extruded,printed,and sintered grits for use in precision grinding applications are critically reviewed.The paper concludes by explaining how such abrasives are used in practice by industrial manufacturers of high-precision products.
基金This work was supported by NSF (Grant Nos. EAR 0003421 and EAR/IF 9818704)the National Natural Science Foundation of China (Grant No. 49834001)All the measurements were performed at the Institute for Rock Magnetism, which is funded by the Keck Fo
文摘This study systematically investigates changes in both compositions and grain-sizes of magnetic minerals in the Chinese loess/paleosol samples (Yichuan, China) during thermal demagnetization processes. Between 100 and 200℃, (1) Hc and Hcr significantly decrease while Mrs and Ms remain stable; (2) concentration of the multi-domain (MD) grains increases while that of superparamagnetic (SP) grains decreases; and (3) there exists the abnormal behavior of the thermal demagnetization in the natural remanent magnetization (NRM). In addition, the corresponding changes in all these parameters are gradually muted with the increase of the pedogenesis degree. The results indicate that the observed alteration probably relates to reducing processes caused by the burning of the organic matter in samples. Before the thermal treatment, the MD grains in loess samples had been partially altered in nature by low-temperature oxidization (LTD). This CRM can be sufficiently attenuated or even removed by the reducing
