Nanofluid Minimum Quantity Lubrication Grinding Research Articles

Atomization mechanism and machinability evaluation with electrically charged nanolubricant grinding of GH4169

Nanofluid minimum quantity lubrication (NMQL), which offers excellent economic and environmental benefits, has the greatest potential to replace traditional metal grinding with fluids. However, insufficient infiltration performance, poor atomization properties, and inferior controllability are found in pneumatic atomization minimum quantity lubrication (MQL), hindering the improvement of grinding performance. Electrostatic atomization MQL (EMQL) is expected to address the coexistence of grindability and sustainability through electrical charge empowerment. Nevertheless, studies addressing the effects and mechanisms of electrically charged nanolubricants in the grinding of nickel-based superalloys remain scarce. In this study, the atomization characteristics of EMQL are experimentally investigated, and results show that the droplet volume average diameter and diameter Rosin–Rammler distribution span of EMQL decreased by 7.1 % and 40.3 %, respectively, in comparison with those of MQL. Then, a series of grinding experiments on GH4169 with different cooling conditions are conducted. Results show that compared with those for MQL grinding, the coefficients of friction for EMQL and NMQL grinding decreased by 9.35 % and 15.62 %, the specific grinding energies decreased by 16.71 % and 29.06 %, and the values of surface roughness Sa decreased by 3.04 % and 14.33 %, respectively. The optimal combination of atomization method and medium for grinding GH4169 is EMQL and nanolubricant. Sa showed a 16.12 % decrease for the surface machined via the optimal combination compared with the surface machined via flooding. Last, to support the interpretation of the grinding outcomes, the antifriction mechanisms of electrically charged nanolubricants are analyzed in combination with the wetting, infiltration, and film-formation capabilities of droplets. The findings of this work are expected to provide experimental references for the surface integrity improvement of the nickel-based superalloy grinding process.

Surface morphology assessment of CFRP transverse grinding using CNT nanofluid minimum quantity lubrication

Carbon fiber-reinforced polymer (CFRP) composites are of high interest in the field of aerospace because of their extremely high strength-to-weight and stiffness-to-weight ratios. Dry processing has been widely applied due to the hygrothermal aging of CFRP using flood lubrication. However, severe conditions of dry machining lead to an abundance of multifarious defects and dust harmful to humans and the environment. The increasing vegetable oil-based nanofluid minimum quantity lubrication (NMQL) involving CNTs with excellent heat transfer and friction reduction could solve the above technique bottleneck. Grinding experiments under different conditions were conducted to investigate the CFRP grindability of NMQL. Results show that compared with dry grinding, the surface roughness Ra, Rz, and RSm values of CNT NMQL in the feed direction (fiber direction) are reduced by 17.70%, 20.78%, and 25.40% (12.68%, 25.06%, and 11.43%), respectively. Furthermore, the 3D fractal dimension of NMQL grinding was the lowest, and the spectral width and difference were decreased by 21.76% and 31%, respectively. The texture features of the machined surface roughness of NMQL demonstrated the least changes, in which the energy proportion of the high-frequency detail signal was reduced by 46.85% compared with dry grinding. The energy proportion of detail sub-images in the NMQL grinding SEM wavelet decomposition diagram was the lowest (0.4214). The proportion of the defect characteristics in the horizontal direction (0.155) was less than the vertical direction (0.1952). This finding was consistent with the energy proportion of the surface roughness signal wavelet analysis. This study demonstrated the feasibility of CFRP precision machining using NMQL.

Surface morphology evaluation of multi-angle 2D ultrasonic vibration integrated with nanofluid minimum quantity lubrication grinding

Nanofluid minimum quantity lubrication (NMQL) is an emerging cleaner and sustainable technique. However, the effective immersion of nanofluids in the grinding zone in NMQL grinding limits the extensive application of this technique. Ultrasonic vibration can exert a pumping effect that injects nanofluids into the interface between the grinding wheel and workpiece. Furthermore, technique integration benefits the infiltration state transition of micro-droplets. However, evaluation of the coupling effect and surface morphology of multi-angle 2D ultrasonic vibration integrated with NMQL has rarely been performed. This study aims to address these research limitations. A kinematics model was developed, and the grain and workpiece relative motion trails in 2D ultrasonic vibration-assisted grinding (UVAG) were simulated at different resultant vibration angles (θ). The grain’s cutting characteristics were then analyzed and found to be conducive to the full infiltration of nanofluids into the grinding zone. Moreover, the surface characterization of multi-angle 2D UVAG coupled with NMQL was evaluated experimentally. Results showed that the optimal θ was achieved at 45° due to the differential cutting action of the follow-up grain. NMQL obtained a better result than flooding at the same θ. When the gain effect of the coupling techniques was reflected in surface roughness, the Ra value decreased by 19.5 % (compared with UVAG) and 39.9 % (compared with NMQL). The autocorrelation function curves presented periodic and continuous local oscillations under the grinding conditions of 2D UVAG with θ = 45° and θ = 135°.

Specific Energy and G ratio of Grinding Cemented Carbide under Different Cooling and Lubrication Conditions

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.

Spraying parameter optimization and microtopography evaluation in nanofluid minimum quantity lubrication grinding

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.

Temperature field model and experimental verification on cryogenic air nanofluid minimum quantity lubrication grinding

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.

Analysis of single-grain interference mechanics based on material removal and plastic stacking mechanisms in nanofluid minimum quantity lubrication grinding

Numerous researchers made theoretical and experimental approaches for force prediction in surface grinding under dry condition. However, the combined effect of both material removal and plastic stacking on single-grain interference mechanics has not been reported yet. The main objective of the work presents to propose an single-grain interference mechanics with the consideration of material removal and plastic stacking mechanism. Interference action of a single grain and plastic/fracture deformation condition of workpiece material were analysis, critical stress was obtained. Further, scratch test of single-grain was carried out under nanofluids minimum quality lubrication. the relationship of grain-cutting efficiency (β) and cutting depth (ag) was obtained. Results indicated that the variation trend of the β presents an S-shaped trend as the ag increases. Grain states, including cutting and ploughing, are decided by cutting efficiency (β). For experiment implemented scratch tests of workpiece material (stainless steel 440 C, Ra = 0.04–0.05 μm), the plough phenomenon appeared at ag=0.023 μm, that is, the range 0~0.023 μm indicates the sliding stage. The cutting stage started at ag=2.84μm. Unlike traditional grinding theory, after the end of the ploughing stage, the β curve suddenly increased and then entered the transition stage. The transition from the ploughing stage into the cutting stage is a progressive process. After cutting stage, β gradually tended to be a constant.

Finite difference simulation and experimental investigation: effects of physical synergetic properties of nanoparticles on temperature distribution and surface integrity of workpiece in nanofluid MQL grinding process

Application of nanofluids in minimum quantity lubrication (MQL) system in grinding has been proven as an effective approach to counter the negative effects of high temperature evolution in grinding process. However, the cooling and tribological properties of nanolubricants are physical synergetic as the morphology, atomic structure, and physical properties of nanoparticles are determining factors on their performance in MQL systems. Graphite and CuO nanoparticles are representatives of nanoparticles with different atomic structures and physical properties. In this study, a finite difference model based on exponential distribution of moving heat source in wheel-workpiece contact area has been developed to determine the energy partition and temperature distribution of workpiece in nanofluid MQL grinding process using graphite and CuO nanofluids as lubricants. In order to study the effects of atomic structures of nanoparticles on the tribological properties of nanofluids, surface roughness and SEM images of ground surfaces have been evaluated. The results showed that CuO nanofluids with rolling action of nanoparticles in the contact area provide lower energy partition and better surface quality of workpiece in comparison with that of graphite nanofluids with sliding mechanism of atomic planes of nanoparticles at the wheel-workpiece interface during grinding process.

Performances of Al2O3/SiC hybrid nanofluids in minimum-quantity lubrication grinding

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.

Technological Investigation about Minimum Quantity Lubrication Grinding Metallic Material with Nanofluid

In the recent years, a number of patents have been developed to improve grinding techniques that will be beneficial to the environment. Among them, nanofluid minimum quantity lubrication (MQL) has emerged as the extremely significant aspect in grinding because of environmentally friendly, energy efficient and cost-effective properties. One patent is about a supply system for the grinding fluid in nano-particle jet MQL, which produced MQL lubricant by adding solid nanoparticles in degradable grinding fluid. During grinding process, grinding fluid could be served in lubrication, cooling, cleaning and rust prevention, thus enabling to prolong service life of the grinding wheel, protect workpiece processing quality and precision, improve production efficiency, and lower cost. In considering of environmental protection, low carbon, processing performance and economical efficiency, flood grinding could not adapt to the concept of green manufacturing and sustainable development any longer. The clean and pollution-free MQL grinding technique has attracted wide research attentions. Particularly, with the continuous development of nanotechnology, nanofluid MQL grinding which combines nanotechnology and MQL grinding technique further improves the poor cooling effect of MQL grinding and becomes the frontier research topic of grinding process. This paper describes research progresses of nanofluid MQL grinding mainly from different nanofluids, different base oil, different nanofluid concentrations and efflux parameters, and proposes the development trend of nanofluid MQL grinding. Keywords: Friction coefficients, MQL grinding, nanofluid, nanoparticles jet flow, specific grinding energy, G-ratio, surface roughness.

Experimental evaluation of the lubrication performance of MoS2/CNT nanofluid for minimal quantity lubrication in Ni-based alloy grinding

A nanofluid minimum quantity lubrication with addition of one kind of nanoparticle has several limitations, such as grinding of difficult-to-cutting materials. Hybrid nanoparticles integrate the properties of two or more kinds of nanoparticles, thus having better lubrication and heat transfer performances than single nanoparticle additives. However, the use of hybrid nanoparticles in nanofluid minimum quantity lubrication grinding has not been reported. This study aims to determine whether hybrid nanoparticles have better lubrication performance than pure nanoparticle. A hybrid nanofluid consisting of MoS2 nanoparticles with good lubrication effect and CNTs with high heat conductivity coefficient is investigated. The effects of the hybrid nanofluid on grinding force, coefficient of friction, and workpiece surface quality for Ni-based alloy grinding are analyzed. Results show that the MoS2/CNT hybrid nanoparticles achieve better lubrication effect than single nanoparticles. The optimal MoS2/CNT mixing ratio and nanofluid concentration are 2:1 and 6wt%, respectively.

Investigation on the Effect of Nanofluid Parameters on MQL Grinding

Nanofluid minimum quantity lubrication (MQL) method was used in the grinding process to replace conventional fluid grinding for overcoming ecological and economical problems. Although previous researchers have studied the lubricating and cooling performance of nanofluid MQL grinding, a systematical analysis of the effect of nanofluid parameters on grinding performance has not been done yet. In this study, nanofluid surface grinding experiment with MQL method under different nanofluid parameters was accomplished. The grinding properties, such as grinding force, grinding force ratio, grinding temperature, and ground surface roughness were investigated. It is found that the lubricating and cooling performance in the grinding zone are improved with the increase of the nanoparticle concentration. Therefore, nanofluid MQL grinding with higher concentration nanoparticle has lower grinding force, grinding temperature, and surface roughness in comparison with lower concentration nanoparticle. When the diameter of nanoparticle increases, tangential grinding force decreases slightly, and the peak grinding temperature is similar. However, the surface finish is deteriorated with the increase of the diameter of nanoparticle. The experimental results also show that the lubricating performance of water-based nanofluid is worse than that of oil-based nanofluid, but the cooling effect is just reverse.

Investigation of grinding characteristic using nanofluid minimum quantity lubrication

Conventional grinding fluid is widely used in grinding process, which results in high consumption and impacting the environment. The promising alternative to conventional dry and fluid coolant application is minimum quantity lubrication (MQL). It is known that the cooling and lubrication performance of the grinding fluid is the key technical area for the success application of MQL grinding process. In this study, Water based Al2O3 nanofluid was applied to grinding process with MQL approach for its excellent convection heat transfer and thermal conductivity properties. The grinding characteristics of hardened AISI 52100 steel were investigated and compared with those of wet, dry and pure water MQL grinding. Experimental results show that water based Al2O3 nanofluid MQL grinding can significantly reduce the grinding temperature, decrease the grinding forces, improve the ground surface morphology and reduce the surface roughness in comparison to pure water MQL grinding. Furthermore, the cooling and lubricating mechanism for nanofluid MQL grinding was discussed in detail.

Application of Nanofluids in Minimum Quantity Lubrication Grinding

This research investigated the wheel wear and tribological characteristics in wet, dry, and minimum quantity lubrication (MQL) grinding of cast iron. Water-based Al2O3 and diamond nanofluids were applied in the MQL grinding process and the grinding results were compared with those of pure water. During the nanofluid MQL grinding, a dense and hard slurry layer was formed on the wheel surface and could benefit the grinding performance. Experimental results showed that G-ratio, defined as the volume of material removed per unit volume of grinding wheel wear, could be improved with high-concentration nanofluids. Nanofluids showed the benefits of reducing grinding forces, improving surface roughness, and preventing workpiece burning. Compared to dry grinding, MQL grinding could significantly reduce the grinding temperature.