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Due to the stringent requirements of carbon emissions, traditional cutting using a large amount of mineral-based metal cutting fluid for lubrication no longer fulfilled the rigorous requirements of policies and standards. Nanofluid minimum quantity lubrication has been proven to be a new process to achieve clean manufacturing. However, due to adhesive contact friction, lubricant droplets cannot effectively penetrate the tool and workpiece interface during continuous turning. Changing the microstructure of the rake face of the tool, such as the micro-texture, may provide a geometric channel for the diffusion of the lubricant. However, the effects of micro-texture geometry and arrangement on the film formation and tribological properties of droplets have not been revealed yet. The spreading behavior of minimum quantity lubrication atomized microdroplet on the textured surface was calculated by hydrodynamic modeling. It was proven that the microchannel can effectively store the lubricating medium atomized by compressed air pneumatics. Furthermore, a comparative experiment was conducted on the influence of the texture arrangement on the cutting performance through the turning experiment. Results show that the microgrooves in the direction perpendicular to the main cutting edge obtained the lowest cutting force. The feed force, radial force, and tangential force were reduced by 13.46%, 16.23%, and 6.34%, respectively. Meanwhile, the texture arranged parallel to the cutting edge and crosswise increased the cutting force. The arrangement of the texture perpendicular to the main cutting edge direction obtained the optimal workpiece surface, the smallest chip curling radius, and the smoothest chip surface. Under the optimized texture arrangement, the anti-wear and anti-friction properties of nanofluids in the cutting area are enhanced.

The conventional flood cooling is neither economically viable nor eco-friendly in the cutting process. The vegetable oil is biodegradable and environmentally friendly used as base oil for the minimum quantity lubricant (MQL) cutting, but the temperature field in the milling zone with different vegetable oils as lubricants remains unclear. The temperature of the MQL milling of the 45 steel was studied with cottonseed, palm, castor, soybean, and peanut oils as base oils. The effects of the fatty acid composition, carbon chain length, thermal conductivity, and viscosity on the milling temperature were also considered. The temperature distribution of the milling of the 45 steel with five different vegetable oils was simulated, showing that the cottonseed and the palm oils had good cooling effect. Experimental results were consistent with the findings obtained using the temperature simulation analysis. Compared with that of the flood milling, the temperature of the MQL milling with different vegetable oils decreased, and the temperature was reduced by 67.4% when the cottonseed oil was used. The surface quality of the workpiece was improved during the MQL milling. When the cottonseed oil was used as lubricant, the surface roughness (Ra) values decreased by 41.5%, 53%, and 50.2% when the cottonseed, palm, and castor oils, respectively, were used as lubricating fluids, which indicated that the advantages of biolubricants as base oils especially cottonseed, palm, and castor oils could be used as base oils for the MQL milling.

Nanofluid minimum quantity lubrication (NMQL) is a resource-saving, environment-friendly, and efficient green processing technology. Cottonseed oil can form a strong lubricating film owing to its abundant saturated fatty acids and monounsaturated fatty acids, which have excellent lubricating properties. The physical and chemical properties of nanofluids change when Al2O3 nanoparticles are added. However, the effects of cottonseed oil–based Al2O3 nanofluid concentrations on the milling force and workpiece surface quality remain unclear. To address this limitation, 45 steel was used to conduct NMQL milling experiments of cottonseed oil–based Al2O3 nanofluids with different mass fractions. Results showed that the minimum milling force was obtained at a concentration of 0.2 wt% (Fx = 58 N, Fy = 12 N). The minimum surface roughness value (Ra = 1.009 μm, RSm = 0.136 mm) was obtained at a mass concentration of 0.5 wt%, and the micromorphology of the workpiece/chip was optimal.

Workpiece surface integrity deterioration is a bottleneck in minimum quantity lubrication (MQL) grinding cemented carbide. However, nanofluids prepared by adding nanoparticles with excellent antifriction and antiwear properties achieve improved lubrication characteristics. In this study, a surface grinding experiment under four working conditions (i.e., dry, flood, MQL, and nanofluid minimum quantity lubrication (NMQL)) with cemented carbide YG8 is conducted to confirm the effectiveness of NMQL grinding. Results show that the minimum specific grinding force (Ft′ = 13.47 N/mm, Fn′ = 2.84 N/mm), friction coefficient (μ = 0.21), specific grinding energy (U = 17.02 J/mm3), and the largest G ratio of 6.52 are obtained using NMQL grinding. Furthermore, no evident furrow and large deformation layers are found on the surface of the workpiece. Moreover, the scanning electron microscope (SEM) images display that the debris is strip-shaped and slenderer than that under the other working conditions. Meanwhile, the blockage of the wheel pore is improved. Therefore, the validity of NMQL in grinding cemented carbide is verified.

In nanofluid minimum quantity lubrication (NMQL) grinding of titanium (Ti) alloy, existing nanoparticles cannot solve the technical bottleneck of high surface integrity. Therefore, graphene (GR) nanoparticles, which have excellent lubrication performance, were applied in NMQL. The tribological properties of GR nanofluid on wheel–workpiece interface were studied by friction and wear test. In the experiment, 0.5–3 nm thick GR nanoparticles were used to prepare 3% vol. palm oil-based nanofluid. Ball-disc experiment under grinding conditions was carried out on the friction and wear tester. Grinding balls with SiC abrasive grains (to simulate the grinding wheel) and Ti-6Al-4V disc (to simulate the workpiece) were used. Load force was set for simulation of pressure boundary condition of the grinding wheel–workpiece interface. Stratiform nanoparticles (MoS2, MoO3, and HBN) were used as the comparison group. Results demonstrated that GR nanofluid achieved smaller friction coefficient (0.295), error bars (0.0029), and area of scratches (182,940 μm2). GR nanoparticles with small gravity and large specific surface area improved the viscosity of nanofluid and consequently the lubrication performance. The plane hexagonal honeycomb structure determines the strong lubrication stability and abrasive resistance of the GR nanoparticles. The scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) images of the scratch surface also verified the above conclusions.

To overcome environmental problems, nanofluid minimum quantity lubrication (NMQL) has been utilized as a burgeoning alternative technique to conventional flood machining, which consumes a large quantity of cutting fluid. Furthermore, spraying parameter optimization is a prerequisite of an effective NMQL grinding and a key to achieving a new sustainable grinding process. However, the spraying parameters of NMQL are multifarious and have varying degrees of influence on lubri-cooling performance. The main objective of this work is to first obtain good spraying parameters in NMQL grinding through the analysis of signal-to-noise ratio and analysis of variance based on orthogonal experiment results. Furthermore, an experimental verification is carried out on the basis of the relative optimization of several groups of spraying parameters from the orthogonal experiments. Power spectral density function (PSDF) and energy spectrum are used to analyze the workpiece and debris microtopography. Consequently, the optimal spraying parameter is obtained. The spraying parameter (palm oil as the base oil, 2 vol% nanoparticle concentration, 0.6 MPa air pressure, and 0.4 gas–liquid flow ratio) achieved the lowest proportionality coefficient (0.245) of PSDF in the low-frequency band and the highest (0.142) in the high-frequency band. Meanwhile, the optimal grinding performance is validated by the workpiece and debris microtopography and long-strip debris morphology.

Minimum quantity lubricant milling (MLQM) with nanofluids is one of the main processing methods used in sustainable green manufacturing. Nanoparticles can drastically enhance the heat transfer ability of metalworking fluids. Thus, nanofluids modified with different nanoparticles have important applications as milling coolants. Nevertheless, few studies have investigated the influence of different nanoparticles on the cooling mechanisms of nanofluids. An experimental study was conducted to explore the cooling performances of different nanofluids in the MQLM of Ti–6Al–4V. Cottonseed oil was used as the nanofluid base and was modified with six different nanoparticles at the mass ratio of 1.5%. Cooling performance was evaluated with several milling parameters, including milling force, instantaneous temperature, and surface roughness, which was represented as the arithmetic average height (Ra) of the workpiece surface. The microtopography of the final milled samples was also examined. Results demonstrated that the mean of the milling force peak in the X direction under milling with SiO2 nanofluid was 436 N, which was lower than that under milling with MoS2 nanofluid (445.5 N). The lowest milling temperature was obtained with SiO2 nanofluid. This result indicated that SiO2 nanoparticles had the strongest cooling capacity. Workpiece temperature rapidly decreased to a low value under milling with SiO2 and Al2O3 nanofluids. The most drastic temperature drop was observed in MQLM with SiO2 nanofluid, followed by that in MQLM with Al2O3 nanofluid. The lowest Ra value was obtained under milling with Al2O3 nanofluid (0.59 μm), followed by that obtained under milling with SiO2 nanofluid (0.61 μm). The Ra value acquired under milling with Al2O3 nanofluid was 66.7% lower than that of acquired under milling with pure cottonseed oil. Given that Al2O3 and SiO2 nanoparticles demonstrated the best cooling performance, they are highly suitable as additives for the base oil.

The objective of this research is to experimentally evaluate the lubrication performances of different nanofluids in milling titanium alloy Ti-6Al-4V. Six types of nanofluids, namely, Al2O3, SiO2, MoS2, CNTs, SiC, and graphite, were selected. Cottonseed oil was used as the base oil. The lubrication performance was investigated in terms of milling force, surface roughness, and morphology of workpiece surface. Experimental results demonstrated that the Al2O3 nanoparticle obtained the minimal milling force (Fx = 277.5 N, Fy = 88.3 N), followed by the SiO2 nanoparticle (Fx = 283.6 N, Fy = 86.5 N). The surface roughness obtained by the Al2O3 nanofluid was the minimum (Ra = 0.594 μm), whereas it was the maximum by using minimum quantity lubrication (Ra = 1.772 μm). The surface roughness of the six nanofluids was described by the following order: Al2O3

The grindability and sensibility analysis of surface roughness of powder metallurgy nickel-base superalloy FGH96 were studied in comparison to the wrought nickel-base superalloy GH4169. The effects of grinding parameters (such as workpiece infeed speed, depth of cut, and abrasive wheel speed) on grinding force, grinding temperature, specific grinding energy, abrasive wheel wear, and surface roughness were analyzed. The results show that the grinding force, grinding temperature, and specific grinding energy of GH4169 are usually higher than those of FGH96 under the given experimental conditions. However, the wear behavior of the brown corundum abrasive wheels when grinding these two kinds of nickel-base superalloy material is generally identical. The sensitivity of GH4169 workpiece surface roughness to depth of cut and workpiece infeed speed is higher than that of FGH96, but the sensitivity of GH4169 to abrasive wheel speed is less than that of FGH96. Finally, it is inferred that the grinding performance of FGH96 is slightly better than that of GH4169.

Nanofluid minimum quantity lubrication (NMQL) technique has many technological and economic advantages in grinding operation. NMQL can improve grinding performance in terms of cooling and lubrication and is ecofriendly because it consumes a small amount of grinding fluid. Ultrasonic machining can improve grinding performance owing to its reciprocating vibration mechanism and furrow widening. Consequently, the simultaneous utilization of these techniques is anticipated to improve the surface quality, especially for hard brittle materials. In this research, multiangle two-dimensional (2D) ultrasonic vibration is utilized in zirconia ceramic grinding. Results reveal that the adhesion and material peeling phenomenon on the workpiece surface is obviously reduced compared with dry grinding without ultrasonic vibration. The synergistic effect of multiangle 2D ultrasonic and NMQL is also studied. With increased angle, the roughness value is found to initially increase (from 45° to 90°) and then decreases (from 90° to 135°). Moreover, the lubricating effect under 90° is the poorest, with the highest Ra and RSm values of 0.703 μm and 0.106 mm, respectively; conversely, the minimum Ra value (0.585 μm) is obtained under 45°, and the lowest RSm value (0.076 mm) is obtained under 135°.

Processing of Ti alloy is often accompanied with large frictions and high temperature. Nanofluids prepared by adding nanoparticles show good lubrication performance due to the excellent antifriction and antiwear of nanoparticles. The physicochemical properties of nanoparticles are important factors that influence the lubrication performance of nanofluid minimum quantity lubrication (NMQL). An experimental study on Ti alloy (Ti–6Al–4V) milling was conducted to explore the lubrication performance of minimum quantity lubrication (MQL) using different nanofluids. Cottonseed oil was used as the base oil, and the tribological properties of several typical nanoparticles (i.e., Al2O3, MoS2, SiO2, carbon nanotubes, SiC, graphite) were studied. The lubrication performance was evaluated by milling parameters, including milling force, surface roughness (Ra, RSm, Rmr), friction coefficient, microstructures of debris and workpiece surface, and energy spectra of the workpiece surface. Results demonstrated that the milling process based on Al2O3 nanofluid achieved the minimum milling force and friction coefficient, whereas the milling process based on SiO2 nanofluid had the minimum surface roughness value (Ra). Furthermore, the physicochemical properties of nanoparticles and the viscosity of nanofluid were analyzed. Spherical Al2O3 and SiO2 nanoparticles improved the lubrication effect of base oil mostly. The Al2O3 nanoparticles exhibited high hardness, which was conducive to reducing milling force. SiO2 nanofluid demonstrated high viscosity, which could improve workpiece surface quality.

Considering the poor lubricating effect of cryogenic air (CA) and inadequate cooling ability of nanofluid minimum quantity lubrication (NMQL), this work proposes a new manufacturing technique cryogenic air nanofluid minimum quantity lubrication (CNMQL). A heat transfer coefficient and a finite difference model under different grinding conditions were established based on the theory of boiling heat transfer and conduction. The temperature field in the grinding zone under different cooling conditions was simulated. Results showed that CNMQL exerts the optimal cooling effect, followed by CA and NMQL. On the basis of model simulation, experimental verification of the surface grinding temperature field under cooling conditions of CA, MQL, and CNMQL was conducted with Ti–6Al–4V as the workpiece material. Simultaneously, CNMQL exhibits the smallest specific tangential and normal grinding forces (2.17 and 2.66 N/mm, respectively). Further, the lowest grinding temperature (155.9 °C) was also obtained, which verified the excellent cooling and heat transfer capabilities of CNMQL grinding. Furthermore, the experimental results were in agreement with theoretical analysis, thereby validating the accuracy of the theoretical model.

Nanofluid minimum quantity lubrication (NMQL) is one of the main modes of sustainable manufacturing. It is an environment-friendly, energy-saving, and highly efficient lubrication method. With the use of nanoparticles, the tribological properties of debris–tool and workpiece–tool interfaces will change. However, spectrum analyses of force and power spectral density (PSD) of surface microstructures are limited. In the present work, the milling force, friction coefficient, specific energy, surface roughness, and surface microstructure of debris were evaluated in milling of 45 steel for different lubrication conditions, namely, dry, flood, minimum quantity lubrication, and Al2O3 NMQL. Results demonstrated that compared with other lubrication conditions, NMQL achieves minimum milling force peak (Fx = 270 N, Fy = 160 N, Fz = 50 N), friction coefficient (μ = 1.039), specific energy (U = 65.5 J/mm3), and surface roughness value (Ra = 2.254 μm, RSm = 0.0562 mm). Furthermore, a spectrum analysis of the milling force and PSD of the surface microstructure was conducted for validation. The spectral analysis of milling force revealed that NMQL obtained the lowest milling force and amplitude in the middle-frequency region, thereby indicating the minimum abrasion loss of the tool. Meanwhile, the PSD analysis indicated that NMQL had the lowest proportional coefficient in the low-frequency region (0.4766) and the highest proportional coefficient in the high-frequency region (0.0569). These results revealed that the workpiece surface gained by Al2O3 NMQL obtained higher wave fineness than other working conditions. By combining with the lowest Ra, NMQL contributes the best workpiece surface quality. Therefore, machining experiments using NMQL showed the best lubrication performance.

This study investigated the grinding temperature of minimum quantity lubricant cooling (MQLC) for heat transfer. Three typical workpiece materials, namely, 45 steel, Ni-based alloy, and nodular cast iron, were surface grinded. These materials are the most frequently used for mechanical processing. Palm oil with good lubrication and heat transfer performance was chosen as the base oil for the nanofluids. Carbon nanotube (CNT) nanofluids with volume fractions of 2 and 2.5%, as well as excellent heat transfer performance, were prepared for the MQLC fluid. Results showed that the 45 steel grinding had the highest temperature (363.9 °C), and the grinding temperature of the 2% nanofluid (363.9 °C) was slightly higher than that of the 2.5% nanofluid (352.9 °C). A numerical simulation heat transfer model conducting the finite difference method was established for the numerical analysis of the MQLC grinding temperature. Results indicated that the model predictions and experimental results are in good agreement, with 4.8% average model error. The heat transfer mechanism of the nanofluids was also analyzed. This study confirmed that nucleate boiling heat transfer was achieved when grinding the Ni-based alloy.

In order to reduce the grinding temperature and improve the lubrication and cooling performance of grinding process, a spiral orderly distributed fiber tool was proposed. The simulation of flow field in cutting zone for spiral orderly distributed fiber tool and the grinding experiment were carried out. The results indicate that the useful flow of cutting fluid for the spiral orderly distributed fiber tool is increased obviously, in comparison to the traditional grinding wheel with disordered arrangement of grains. When the fiber number per unit area for the fiber tool is kept constant, the useful flow of cutting fluid is increased with increment of the fiber pitch. When the fluid jet speed or the exit height of the spray nozzle is increased, on the one hand, the useful flow of cutting fluid is increased; but on the other hand, the utilization rate of the useful flow of cutting fluid is reduced. The useful flow of cutting fluid supplying with an angle of 15° on the horizontal direction is significantly higher than that in the horizontal direction. The computational model is validated by cutting experiments with a corundum grinding wheel.

Palm oil was used as the base oil of minimum-quantity lubricant cooling (MQLC) grinding of Ni-based alloy. Eight nanofluids with different volume fractions of 0.5, 1, 1.5, 2, 2.5, 3, 3.5, and 4 % were prepared by using carbon nanotube (CNT) nanoparticles for the experiment on MQLC grinding of Ni-based alloy. Grinding force, grinding temperature, and proportionality coefficient of energies transferred into the workpiece were analyzed and discussed based on the thermal conductivity, viscosity, and contact angle of the nanofluid. Heat exchange performances of the eight prepared nanofluids were studied in sequence. The volume fraction of 2 % nanofluid achieved 21.93 N grinding force, the lowest grinding temperature of 109.8 °C, and the lowest proportionality coefficient of 42.7 %. The high thermal conductivity of nanofluids is conducive to quick heat transfer. High viscosity promotes the lubrication effect and can reduce energy input and the production of grinding heat. The contact angle and surface tension of eight kinds of nanofluids showed a trend of 2 % < 2.5 % < 4 % < 3.5 % < 3 % < 1.5 % < 1 % < 0.5 %. Thus, the volume fraction of 2 % nanofluid-based MQLC grinding Ni-based alloy achieved the optimal lubrication and heat transfer performance.

The present research investigated the lubrication performances of Al2O3/SiC nanofluid minimum-quantity lubrication (MQL) grinding in accordance with recent technologies used in conducting minimum-quantity lubrication grinding with nanofluids. The mean grain size of the Al2O3 and SiC nanoparticles (NPs) was set to 50 nm, and the difficult grinding Ni-based alloy was used as the workpiece material in the experiment. Grinding force was measure by using a three-component dynamometer and then used to calculate grinding force ratio (R). Workpiece surface roughness was measured by a roughness tester. Five groups of NPs were mixed with synthetic lipids at a mass fraction of 6 %. The lipids were then used as the grinding fluid for the nanofluid MQL grinding. Results showed that, compared with pure SiC NPs, pure Al2O3 NPs obtained lower R = 0.3, lower specific grinding energy (U = 75.93 J/mm3), and lower surface roughness (Ra = 0.386 μm), indicating better lubrication performance. The mixed NP consisting of Al2O3 and SiC NPs achieved even lower R and surface roughness than pure NPs because of the “physical synergistic effect.” The optimal ratio of the effect of mixed NPs was explored based on this finding. The Al2O3/SiC (2:1) mixed NPs obtained the smallest R = 0.28 and specific grinding energy (U = 60.68 J/mm3), thus indicating the best lubrication performance. Therefore, 2:1 is the optimal ratio for mixed NPs.

In previous studies, the improvement of the useful flow and flow rate of grinding fluid has been investigated via modeling, simulation, and experiment. Optimized grinding parameters have been achieved. A detailed assessment of the improvement in the useful flow rate of grinding fluid, which optimizes the grinding fluid supply, has been published in the International Journal of Advanced Manufacturing Technology (Li et al. Int J Adv Manuf Technol 75:1587–1604, 2014). Then, a detailed experimental study on the improvement in the useful flow rate of grinding fluid has been published in the International Journal of Advanced Manufacturing Technology (Li et al. Int J Adv Manuf Technol 1–10. doi: 10.1007/s00170-015-7230-z , 2015), in which the influence of grinding wheel speed, grinding fluid jet velocity, particle size, and bulk porosity on useful flow and useful flow rate was analyzed. In this paper, a new method of air scraper is presented and simulated with focus on the air boundary layer and reflux around the grinding wheel. In view of the influence of the gas barrier of grinding wheels on the effective supply of grinding fluid, the effect of the scraper on the gas barrier layer was analyzed through the grinding flow field simulation under unified grinding parameters. Using the air scraper to destroy the gas barrier layer is proposed, and a supply scheme is designed to improve the useful flow rate. Results show that using the scraper has a certain effect on the weakening of the grinding gas barrier layer. In the grinding process, using the scraper can reduce the obstacles to grinding fluid supply, thereby improving the useful flow of grinding fluid into grinding wheel workpieces. The distance between the front end of the plane scraper and the grinding wheel is 10 μm, with a large circular boot-shaped nozzle. Alternatively, the distance between the front end of the nozzle and the grinding wheel surface is 50 μm, which can increase the useful rate of flow of grinding fluid.

Based on research on nanofluid minimum quantity lubrication (MQL) in grinding, a plane grinding experiment was performed on Ni-based alloy using a K-P36 precision numerical control surface grinder. Uniform grinding parameters were used in the experiment, but three groups of MQL jet parameters were changed. The grinding force was measured using a YDM-III99 three-dimensional dynamometer to calculate the specific grinding energy and coefficient of friction. The surface roughness of the workpiece was measured using a TIME3220 roughness tester. An experimental research was also conducted on the droplet size and velocity of the jet using a high-speed camera system. Results showed that the most ideal lubricating effect was achieved under 0.5 MPa compressed gas, 0.4 gas–liquid ratio, and 0.005 kg/s liquid flow rate. Under the best jet flow condition, the specific tangential grinding force, specific grinding energy, and coefficient of friction were 1.45 N/mm, 74.57 J/mm3, and 0.414, respectively. The surface roughness of the workpiece was at its most ideal at this point, where Ra, Rz, and RSm were 0.249 μm, 1.972 μm, and 0.028 mm, respectively. Based on high-speed continuous shooting at the jet, the mean droplet size was about 171.82 μm under the optimum jet parameters, and the droplets exhibited variable accelerations at a high accelerated velocity (>500 m/s2).

To overcome strong drilling force and significantly high temperature during orthopedic surgery, two medical drills with different geometrical shapes were designed by using superhard materials. The bone-drilling temperature fields under different cutting parameters and cooling modes were simulated by using a brazed step drill and a brazed twist drill. Results showed that given a fixed feed speed, the maximum bone-drilling temperature using the brazed step drill under 500 rpm was 33.5 °C, which increased to 58 °C under 2000 rpm. Meanwhile, the maximum bone-drilling temperature using the brazed twist drill under 500 rpm was 42.9 °C, which increased to 70.1 °C under 2000 rpm. Given a fixed drill speed, the maximum bone-drilling temperatures of both drills varied as feed speed first increased and then decreased. When the feed speed increased from 0.5 to 1.7 mm/s, the maximum bone-drilling temperature of the brazed step drill was proportional to the feed speed. With the further increase in the feed speed from 1.7 to 2.0 mm/s, the maximum bone-drilling temperature decreased. The bone-drilling temperature of the brazed twist drill varied similarly, except for reaching the peak at 1.4 mm/s. The bone-drilling temperature of the brazed step drill was always lower than that of the brazed twist drill under all cutting parameters. The normal saline spray cooling had the best cooling effect, followed by the normal saline pouring cooling and air cooling. The maximum temperatures of these three cooling modes were 43.8, 52.6, and 70.1 °C using the brazed step drill.

The mathematical model of the useful flow and flow rate of grinding fluid under casting surface grinding condition has been established. A detailed assessment of the improvement in the useful flow rate of grinding fluid, which optimizes the grinding fluid supply, has been published in the International Journal of Advanced Manufacturing Technology (Modeling and simulation of useful fluid flow rate in grinding; 2014, 75 (9-12):1587-1604). However, the experiment has not been further verified. In this paper, the useful flow and flow rate of grinding fluid under casting surface grinding condition were extensively studied through experimentation. A collection device for the useful flow of grinding fluid was designed. Moreover, the influence of the speed of the grinding wheel, grinding fluid jet velocity, particle size, and bulk porosity on useful flow and useful flow rate was analyzed. Results show that experimental and simulation results differ slightly under certain grinding parameters. This difference is mainly due to the different peripheral velocities of the grinding wheel and grinding fluid jet velocities. The effect of the gas barrier layer causes the grinding fluid to penetrate the surface pore, which has different coefficients. Meanwhile, the filling coefficient is 0.5 in the simulation settings. A large filling coefficient results in a high useful flow rate. When the grinding fluid jet velocity is increased, the capability to overcome the gas barrier layer is strengthened. Thus, the filling coefficient becomes large. When the speed of the grinding wheel is low, the gas barrier layer is weak. Hence, the filling coefficient is relatively high. The distribution of the simulation results is in agreement with that of the experimental results. This condition verifies the accuracy of the mathematical model and simulation analysis of the useful flow rate of grinding fluid.

Nanoparticles are solid nanoscale particles with features such as antiwear, antifriction, and high load-carrying capacity. This research applied nanoparticles in the cooling lubrication of grinding and theoretically analyzed the impact of cooling lubrication on the grinding surface through the energy ratio coefficient and specific grinding energy. First, the workpiece surface temperature was measured using a thermal infrared imager. A three-dimensional dynamometer was used to identify the tangential grinding force during grinding. Results showed that, with different cooling lubrication approaches, the grinding surface was distributed to workpiece, grinding wheel, grinding fluid, and abrasive debris according to different energy ratio coefficients. The calculation demonstrated that the energy ratio coefficient of dry grinding reached 64.3 %. However, the energy ratio coefficient of flood lubrication, minimal quantities of lubricant (MQL), and nanoparticle jet MQL was 36.8, 52.1, and 41.4 %, respectively. These findings indicated that nanoparticle jet MQL realized a cooling effect close to that of flood lubrication. The specific grinding energy of nanoparticle jet MQL was 35 J/mm3, which was close to that of flood lubrication at 29.8 J/mm3. This finding indicated that the lubrication effects of nanoparticle jet MQL were also similar to those of flood lubrication. Moreover, molybdenum disulfide, carbon nanotube (CNT), and zirconium oxide nanoparticles were added in the grinding fluid to conduct the grinding experiment with nanoparticle jet MQL. The comparison of energy ratio coefficients showed that the cooling performance of CNT nanoparticles was satisfactory. CNT nanoparticles were subsequently added into the grinding fluid at the volume concentrations of 1, 2, and 3 % for the grinding experiment. The results showed that the best cooling effects occurred under the 2 % volume concentration of CNT nanoparticles. Through rounds of selections and optimizations, our research acquired the nanoparticle types and volume concentration that had satisfactory cooling effects and should therefore be added in the grinding fluid.

This research established a mathematical model of the useful grinding fluid flow rate of a rough grinding wheel. The abrasive distribution matrix of the grinding wheel surface topography was programmed on the MATLAB software platform to obtain the grinding wheel porosity φ at different particle sizes. The grinding fluid flow field was simulated and studied by using the volume of fluid multiphase flow model of FLUENT. Results showed that given a certain circular velocity of the grinding wheel, a larger grinding fluid jet velocity resulted in greater useful grinding fluid flow. When the grinding fluid jet velocity was set, the useful grinding fluid flow increased with increasing circular velocity of the grinding wheel. With the increasing velocity of the grinding wheel, as affected by the airbond layer, the increasing rate of the useful grinding fluid flow decreased, and the flow likewise showed a tendency to decrease. With a certain grinding fluid jet velocity, the useful flow rate of the grinding fluid was positively proportional to the useful flow. When the grinding fluid jet velocity changed and grinding wheel velocity was set, the grinding fluid jet velocity increased as the useful flow rate decreased. When the grinding fluid jet velocity was equivalent to the grinding wheel velocity, the useful flow rate of the grinding fluid was positively proportional to the useful flow. When the minimum clearance of grinding zone h increased, the useful grinding fluid flow and useful flow rate likewise increased. When the grinding fluid jet velocity was equivalent to the grinding wheel velocity, a larger nozzle gap width increased the flow supply for the grinding fluid and the useful grinding fluid flow. However, the increase in the useful flow rate of the grinding fluid was significantly smaller than that of the nozzle flow. This condition decreased the useful flow rate of the grinding fluid.

This study investigates the grinding process of the common grinding wheel under nanoparticle jet flow minimal quantity lubrication. This study establishes a kinematics model, elastic deformation model, and plastic accumulation model of a single grinding wheel, simulates the grain distribution on the surface of the common grinding wheel by using the grain vibration method, and examines the effect of different grinding parameters on the surface topography of the workpiece. Results show that the peaks and valleys on the profile curve of the workpiece surface increase and the corresponding R a and R z heights decrease, as the peripheral velocity of the grinding wheel increases. The peaks and valleys on the profile curve of the workpiece surface decrease, and the corresponding R a and R z heights increase as the feed speed of the workpiece increases. The number of grinding cracks on the surface of the workpiece decreases, the length of each crack increases, and the bump height on the surface increases slightly as the grinding depth increases. Experiments are conducted to verify the simulation results. The results show that the simulation method can predict the surface roughness of the workpiece, which is a factor in selecting the grinding parameters.