3. A review on the law of grinding thermodynamics

#### 3.1. A review on grinding forces under NMQLC condition

More research has been done on the lubrication effect of the NMQLC technique based on published literatures. A good lubrication in the grinding zone can reduce the grinding wheel/ workpiece friction, thereby reducing grinding force and heat generation [30–32]. Manojkumar and Ghosh [33] found that nanofluid could substantially outperform soluble oil in terms of grinding force and G ratio (representing wheel life) under NMQLC. Setti et al. [34] showed that NMQLC could reduce normal force (Fn) on an average of 12 and 28% and reduce Ft on an average of 15 and 27% compared to flood and MQL. Sinha et al. [35] reported that grinding forces, coefficient of friction (μ) can be reduced to the maximum by nanofluids. Kalita et al. [36] measured a decline of 45–50% in force-ratio against grinding with flood cooling and MQL. Shen et al. [37] showed that lubricants with MoS2 nanoparticles significantly reduce the Ft and the overall grinding performance. Jia et al. [38] found that soybean/castor mixed oil obtained the optimal results and lubricating effect compared to castor oil and other mixed base oils. Zhang et al. [39] reported that the energy ratio coefficient of flood lubrication, MQL, and NMQLC was 36.8, 52.1, and 41.4%, respectively, indicating that NMQLC realized a lubrication cooling effect close to that of flood lubrication. Zhang et al. [40, 41] found that NMQLC grinding using mixed nanoparticles obtain lower grinding force ratios and surface roughness (Ra) values, showing that mixed nanoparticles is superior to pure nanoparticles. Lee et al. [42, 43] carried out micro scale grinding experiments under different lubrication conditions and experimental results demonstrated that NMQLC could significantly reduce the grinding forces and enhance the surface quality. Yang et al. [44] investigated the critical maximum undeformed equivalent chip thickness for ductile-brittle transition (DBhmax-e) of zirconia ceramics under different lubrication conditions and found that lubrication condition affects the normal force and ultimately influences the resultant force on workpiece, making DBhmax-<sup>e</sup> decreases with increasing friction coefficient.

Table 1 summarizes the details of investigations on nanofluid parameters for the application of

Figure 1. Specific tangential grinding force and frictional coefficient under different lubricating conditions [6]. (a) Specific

Thermodynamic Mechanism of Nanofluid Minimum Quantity Lubrication Cooling Grinding and Temperature Field…

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65

NMQLC technique was first proposed to solve the problem of inadequate cooling of MQL in grinding [45–48]. Grinding temperature is usually measured by thermocouples. The thermocouples can be placed on the workpiece or on the surface of the grinding wheel. As shown in Figure 2 [49], a thermocouple forms a junction when the grinding wheel passes over the exposed single pole. The pole is smeared onto the workpiece, thereby forming a junction with

Mao et al. [50] analyzed the effect of nanofluid parameters on grinding performance. It is found that the cooling performance in the grinding zone is improved with the increase of the nanoparticle concentration and nanoparticle diameter. Yang et al. [51] studied the effect of different nanoparticles and concentrations on the temperature field of micro grinding. It was found that different thermal physical properties of nanoparticles have different effects on the temperature field. Yang et al. [52] investigated the dynamic heat flux in micro grinding using different sizes of Al2O3 nanoparticles. Results showed that temperatures under NMQLC using nanofluids (30, 50, 70, and 90 nm) are 21.4, 17.6, 16.1, and 8.3% lower, respectively. Li et al. [53] studied the grinding temperature using six types of nanoparticles (MoS2, ZrO2,CNT, polycrystalline diamond, Al2O3, and SiO2), and found that CNT nanofluid results in the lowest grinding temperature of 110.7C with the associated energy proportionality coefficient of 40.1% and

NMQLC technique in improving lubrication.

tangential grinding force. (b) Frictional coefficient.

the ground surface.

3.2. A review on grinding temperature under NMQLC condition

the highest heat transfer coefficient of 1.3 104 W/(m K).

Figure 1(a) and (b) show the specific tangential grinding force and μ under dry, flood, MQL, and NMQLC conditions in the investigation of Jia et al. [6]. The maximum specific tangential grinding force and μ were obtained in dry grinding. Compared with dry grinding, the specific Ft under MQL, NMQLC, and flood conditions decreased successively by 45.88, 62.34, and 69.33%, respectively. Therefore, flood grinding realized the optimal lubrication effect, followed by NMQLC. It can also be seen from Figure 1 that the specific tangential grinding force and μ, which NMQLC realized a lubrication cooling effect close to that of flood lubrication.

Thermodynamic Mechanism of Nanofluid Minimum Quantity Lubrication Cooling Grinding and Temperature Field… http://dx.doi.org/10.5772/intechopen.74969 65

Figure 1. Specific tangential grinding force and frictional coefficient under different lubricating conditions [6]. (a) Specific tangential grinding force. (b) Frictional coefficient.

Table 1 summarizes the details of investigations on nanofluid parameters for the application of NMQLC technique in improving lubrication.

#### 3.2. A review on grinding temperature under NMQLC condition

the liquid drops under electric charge through high-voltage electrostatic field after nanofluids are sprayed out from the nozzle so as to form electrically charged liquid drop flocks, which will be controllably and orderly transported onto workpiece surface under the effect of electric field force. For ultrasonic atomization, micro shock waves are generated during ultrasonic cavitation and bubble closing process in the liquid to damage the interaction between liquid molecules and then liquid particles are dragged out from liquid surface to form liquid drops [29].

More research has been done on the lubrication effect of the NMQLC technique based on published literatures. A good lubrication in the grinding zone can reduce the grinding wheel/ workpiece friction, thereby reducing grinding force and heat generation [30–32]. Manojkumar and Ghosh [33] found that nanofluid could substantially outperform soluble oil in terms of grinding force and G ratio (representing wheel life) under NMQLC. Setti et al. [34] showed that NMQLC could reduce normal force (Fn) on an average of 12 and 28% and reduce Ft on an average of 15 and 27% compared to flood and MQL. Sinha et al. [35] reported that grinding forces, coefficient of friction (μ) can be reduced to the maximum by nanofluids. Kalita et al. [36] measured a decline of 45–50% in force-ratio against grinding with flood cooling and MQL. Shen et al. [37] showed that lubricants with MoS2 nanoparticles significantly reduce the Ft and the overall grinding performance. Jia et al. [38] found that soybean/castor mixed oil obtained the optimal results and lubricating effect compared to castor oil and other mixed base oils. Zhang et al. [39] reported that the energy ratio coefficient of flood lubrication, MQL, and NMQLC was 36.8, 52.1, and 41.4%, respectively, indicating that NMQLC realized a lubrication cooling effect close to that of flood lubrication. Zhang et al. [40, 41] found that NMQLC grinding using mixed nanoparticles obtain lower grinding force ratios and surface roughness (Ra) values, showing that mixed nanoparticles is superior to pure nanoparticles. Lee et al. [42, 43] carried out micro scale grinding experiments under different lubrication conditions and experimental results demonstrated that NMQLC could significantly reduce the grinding forces and enhance the surface quality. Yang et al. [44] investigated the critical maximum undeformed equivalent chip thickness for ductile-brittle transition (DBhmax-e) of zirconia ceramics under different lubrication conditions and found that lubrication condition affects the normal force and ultimately influences the resultant force on workpiece, making DBhmax-<sup>e</sup>

Figure 1(a) and (b) show the specific tangential grinding force and μ under dry, flood, MQL, and NMQLC conditions in the investigation of Jia et al. [6]. The maximum specific tangential grinding force and μ were obtained in dry grinding. Compared with dry grinding, the specific Ft under MQL, NMQLC, and flood conditions decreased successively by 45.88, 62.34, and 69.33%, respectively. Therefore, flood grinding realized the optimal lubrication effect, followed by NMQLC. It can also be seen from Figure 1 that the specific tangential grinding force and μ,

which NMQLC realized a lubrication cooling effect close to that of flood lubrication.

3. A review on the law of grinding thermodynamics

3.1. A review on grinding forces under NMQLC condition

64 Microfluidics and Nanofluidics

decreases with increasing friction coefficient.

NMQLC technique was first proposed to solve the problem of inadequate cooling of MQL in grinding [45–48]. Grinding temperature is usually measured by thermocouples. The thermocouples can be placed on the workpiece or on the surface of the grinding wheel. As shown in Figure 2 [49], a thermocouple forms a junction when the grinding wheel passes over the exposed single pole. The pole is smeared onto the workpiece, thereby forming a junction with the ground surface.

Mao et al. [50] analyzed the effect of nanofluid parameters on grinding performance. It is found that the cooling performance in the grinding zone is improved with the increase of the nanoparticle concentration and nanoparticle diameter. Yang et al. [51] studied the effect of different nanoparticles and concentrations on the temperature field of micro grinding. It was found that different thermal physical properties of nanoparticles have different effects on the temperature field. Yang et al. [52] investigated the dynamic heat flux in micro grinding using different sizes of Al2O3 nanoparticles. Results showed that temperatures under NMQLC using nanofluids (30, 50, 70, and 90 nm) are 21.4, 17.6, 16.1, and 8.3% lower, respectively. Li et al. [53] studied the grinding temperature using six types of nanoparticles (MoS2, ZrO2,CNT, polycrystalline diamond, Al2O3, and SiO2), and found that CNT nanofluid results in the lowest grinding temperature of 110.7C with the associated energy proportionality coefficient of 40.1% and the highest heat transfer coefficient of 1.3 104 W/(m K).


the thermal and flow model for the micro-scale grinding process with experiments. Results showed that the grinding temperatures grinding heat flux into the workpiece and grinding energy partition under NMQLC were much lower than those in the cases of compressed air lubrication and pure MQL. Mao et al. [56] investigated the grinding characteristic under different cooling conditions and the results show that NMQLC grinding can significantly reduce the grinding temperature in comparison to pure water MQL grinding as shown in

Thermodynamic Mechanism of Nanofluid Minimum Quantity Lubrication Cooling Grinding and Temperature Field…

Table 2 summarizes the details of investigations of nanofluid parameters for the application of

Authors Nanoparticle Particle size (nm) Base fluid Concentration

Yang et al. [52] Al2O3 30, 50, 70, 90 Normal saline 2 vol.%

Lee et al. [55] Nanodiamond 30 Paraffin oil 4% vol.% Mao et al. [56] Al2O3 40 Water 1.2 wt.%

Table 2. Details of investigations for application of NMQLC in enhanced heat transfer in grinding zone.

Mean particle size is 50 nm, mean length of CNTs is 10–30 μm

Mean particle size is 50 nm, mean length of CNTs is 10 ~ 30 μm

length of CNTs is 10–30 μm

water, canola oil

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67

Normal saline 2, 4, 6, 8,

Palm oil 6 wt.%

Palm oil 0.5~4 vol.%

1, 3, 5 vol.%,

10 wt.%,

Mao et al. [50] Al2O3 40, 70, 80 Deionized

NMQLC technique in enhanced heat transfer in grinding zone.

Figure 3. Grinding temperatures under different cooling conditions [56].

Yang et al. [51] Hydroxyapatite, SiO2, Fe2O3, CNTs

Al2O3, SiO2

polycrystalline diamond,

Li et al. [54] CNT Mean particle size is 50 nm, mean

Li et al. [53] MoS2, ZrO2,CNT,

Figure 3.

Table 1. Details of investigations on nanofluid parameters for the application of NMQLC in improving lubrication.

Figure 2. Schematic of single pole configuration thermocouple: where 1-workpiece, 2-workpiece base, 3-thermocouple, 4 mica, 5-varnish layer, 6-grinding wheel [49].

Li et al. [54] analyzed grinding temperature based on the thermal conductivity, viscosity, and contact angle of the nanofluids, and found a lower particle concentration can get a smaller contact angle, thus achieving the optimal heat transfer performance. Lee et al. [55] analyzed the thermal and flow model for the micro-scale grinding process with experiments. Results showed that the grinding temperatures grinding heat flux into the workpiece and grinding energy partition under NMQLC were much lower than those in the cases of compressed air lubrication and pure MQL. Mao et al. [56] investigated the grinding characteristic under different cooling conditions and the results show that NMQLC grinding can significantly reduce the grinding temperature in comparison to pure water MQL grinding as shown in Figure 3.

Table 2 summarizes the details of investigations of nanofluid parameters for the application of NMQLC technique in enhanced heat transfer in grinding zone.

Figure 3. Grinding temperatures under different cooling conditions [56].

Li et al. [54] analyzed grinding temperature based on the thermal conductivity, viscosity, and contact angle of the nanofluids, and found a lower particle concentration can get a smaller contact angle, thus achieving the optimal heat transfer performance. Lee et al. [55] analyzed

Figure 2. Schematic of single pole configuration thermocouple: where 1-workpiece, 2-workpiece base, 3-thermocouple, 4-

Authors Nanoparticle Particle size (nm) Base fluid Concentration

Sinha et al. [35] Ag, ZnO 10 (Ag), 25 (ZnO) Deionized water 10~30 vol.% (Ag),

Setti et al. [34] Al2O3 40 Water 1 vol.%

40 nm along minor axis

40 nm along minor axis

Jia et al. [38] MoS2 50 Castor, palm, soybean, peanut,

Zhang et al. [40] Al2O3/SiC 50 Synthetic lipids 6 wt.% Zhang et al. [41] MoS2 50 Palm oil 2 vol.%

Yang et al. [44] MoS2 50 Palm oil 2 vol.% Jia et al. [6] MoS2 50 Soybean oil 6 wt.%

Table 1. Details of investigations on nanofluid parameters for the application of NMQLC in improving lubrication.

Kalita et al. [36] MoS2 70 nm along major axis and

Shen et al. [37] MoS2 70 nm along major axis and

MWCNT Not mentioned Deionized water, soluble oil 0.6, 1 vol.%

0.01~0.5 vol.% (ZnO)

5, 20 wt.%

2, 4, 6, 8, 10 wt.%

Paraffin oil 2, 8 wt.%

Paraffin oil, CANMIST oil,

rapeseed, sunflower, maize oil

soybean oil

50 Soybean oil 1, 2, 3 vol.%

30, 150 Paraffin oil 2, 4 vol.%

Manojkumar and Ghosh [33]

66 Microfluidics and Nanofluidics

Zhang et al. [39] MoS2, CNT,

Lee et al. [42, 43] Nanodiamond, Al2O3

ZrO2

mica, 5-varnish layer, 6-grinding wheel [49].


Table 2. Details of investigations for application of NMQLC in enhanced heat transfer in grinding zone.
