The results show that the nanofluids with a volume fraction of 2% have good comprehensive properties for lubrication. However, this study only concentrates on workpiece material—nickel base alloy. Based on literature analysis, researchers have carried out a large quantity of researches on NMQL grinding of different workpiece materials including hard steel HSS, quenched steel 100Cr6, nickel base alloy, Ti-6Al-4V alloy, soft steel CK45, and cast iron. They have mainly focused on grinding force, surface roughness, etc. The heat transfer state of nanofluids is neglected, and the research on the heat transfer mechanism of grinding temperature is lacking. Therefore, grinding temperatures obtained through MQL grinding with different concentrations of vegetable oils-based nanofluids as well as their heat transfer mechanism are investigated through simulation and experiment in this chapter.
Top10.1 Introduction
Removing the unit volume of metal through grinding requires high-energy input, especially for materials that are difficult to machine. However, almost all energy conversions are concentrated in the grinding zone;much energy is converted into heat and accumulates in the grinding zone (González-Santander, Fernández, Martín, & Arrazola, 2016). If the generated heat cannot be timely transmitted to the grinding zone, then the temperature in the grinding zone will sharply increase and cause various forms of thermal damage, such as burns, metallurgical changes, cracks, and residual stress, to the workpiece (Malkin & Guo, 1991). Hence, the vital link is an available cooling lubrication that can reduce the temperature and effectively improve the quality of the grinding process. With environmental issues becoming increasingly prominent, the conventional cooling lubrication called flood cooling no longer meets the needs of modern development. New green processing methods mainly include dry grinding, low-temperature cooling grinding, minimum quantity lubrication (MQL), and nanofluidMQL grinding. The lubrication of dry grinding and low-temperature cooling grinding should be enhanced, but the limitations of these two methods can be improved by MQL. This technology provides effective lubrication by atomizing and injecting the lubricant liquid into the grinding zone while maintaining high-speed air flow throughout the grinding zone. Convective heat transfer occurs between the grinding wheel and the workpiece, thereby reducing the temperature of the workpiece. Hafenbraedl and Malkin (Hafenbraedl & Malkin, 2001) found that MQL technology can improve the performance of lubrication and reduce the specific grinding energy as compared with conventional processing methods. However, the limited cooling performance of compressed air affects the application of MQL technology in mechanical machining. With the development of nanotechnology, the in-depth study of nanofluids, and the consideration of the green environmental protection and energy saving requirements, nanofluid MQL has been regarded as an effective way for cooling and lubrication (Tasdelen, Thordenberg, & Olofsson, 2008).