Fig.4.8: Simulated and experimental chip morphology under (a) dry, (b) MQL with cutting fluid and (c) MQL with nano-fluid conditions when turning Ti-6Al-4V alloy with uncoated carbide insert. Fig.4.9: Simulated and experimental chip morphology under (a) dry, (b) MQL with cutting fluid and (c) MQL with nano-fluid conditions when turning Ti-6Al-4V alloy with coated carbide insert.
Introduction
Literature review
- Problems regarding Ti-6Al-4V alloy machining
- Effects and control of high cutting temperature
- Effects of conventional cooling methods
- Effects of sustainable cooling methods
- Performance enhancement of MQL technique
- Summary of the review
Moreover, high cutting force and the cutting temperature during Ti-6Al-4V machining are formed due to its hot hardness [Pervaiz et al., 2019]. As a result, the thermal wear of the tool was reduced and the surface finish was improved [KE et al., 2009].
Objectives of the present work
Outline of the thesis
This chapter also contains the objective of the present paper along with the thesis outline. The design and fabrication of the MQL dual-jet delivery system for blowing the mist into the cutting areas is fully described in this chapter.
Experimental Investigations
Experimental procedure and conditions
The first phase of the investigation involved the design of a dual jet MQL delivery system. Fig.2.6 Photographic view of the tool-work thermocouple calibration setup The variation of temperature with different thermoelectric voltage (mV) for the thermocouple of tungsten carbide (tool material) and Ti-6Al-4V alloy is in Fig.2.7 plotted.
Desirability-based RSM technique
The MQL parameters for the validity test of the empirical models are shown in Table 2.9. Optimization of the process inputs was performed for the required value of the process responses. The main effect and interaction graph of cutting temperature for turning Ti-6AL-4V alloy with respect to different cutting parameters (speed, feed rate and depth of cut), nanoparticle concentration and tool type are shown in Fig.3.3 and Fig. 3.4.
For these reasons, the reduction in cutting force for the coated tool is small. An FE model aimed at studying the effect of the definition of constitutive parameters on the simulation of the machining of Ti-6Al-4V alloys has been proposed by Yaich et al. The mesh distribution of the assembly is shown in Figure 4.2, where the different densities can be seen.
In addition, the improved thermal conductivity of the nano-fluid helps to cool the cutting zone easily. In this research, all responses have been given equal importance in the case of multi-response optimization.
Design and fabrication of double jet MQL system
Preparation and characterization of nano-fluid
The thermal performance, such as thermal conductivity and convective heat transfer coefficient of the nanofluid, can be largely improved compared to simple base fluids [Yu et al., 2008]. When preparing hybrid nanofluids, a trade-off took place between the advantages and disadvantages of the individual nanofluids [Minea and Moldoveanu, 2018]. Due to the improvement of the stability of the nanofluid, the addition of surfactants or sonication can be used.
It is expected that each solid particle usually increases the thermal conductivity of the fluid. Using Fourier's law with the temperature of the coaxial cylinders, the thermal conductivity of the liquid samples in the gap can be calculated. The plug and jacket apparatus is based on the concept of the cylindrical cell method previously used to measure the thermal conductivity of nanofluids [Vajjha and Das, 2009].
Experimental results
- Chip morphology
- Cutting temperature
- Cutting force
- Tool wear and tool life
- Surface roughness
- Dimensional deviation
Variation of cutting temperature with machining time for uncoated and coated carbide insert under different cooling environments is shown in Fig.2.23. Fig.2.23 Variation of cutting temperature (T) with machining time for (a) uncoated and (b) coated carbide insert under different cooling environments. Fig.2.24 Variation of main cutting force (F) with machining time for (a) uncoated and (b) coated carbide insert under different cooling environments.
Variation of surface roughness (Ra) with machining time for uncoated and coated carbide inserts under different cooling conditions is shown in Fig.2.29. Fig.2.29 Variation of surface roughness (Ra) with machining time for (a) uncoated and (b) coated carbide inserts under different cooling environments. Fig.2.30 Variation of dimensional deviation with machining time for (a) uncoated and (b) coated carbide inserts under different cooling environments.
Optimization of Process Parameters
Empirical modeling of machining responses
Plots for the residual analysis of the final models are also presented, followed by the ANOVA tables. Because the shearing of the work metal and the friction at the tool-chip interfaces increase with higher cutting speed [Kumar et al., 2013]. Cutting force is an important machinability index that is directly related to the energy consumption of the machining process.
Due to the increase in viscosity, the lubrication at the chip tool and work tool interfaces is increased, but the penetration of the cutting fluid at the interface may be hindered due to the higher viscosity. But, if the depth of cut is less than the nose radius of the tool, then a vibration may occur in the tool which is responsible for the higher roughness. In this research, turning with 0.5 mm of depth of cut (< nose radius 0.8), the highest surface roughness of the product was achieved.
Optimum process parameters selection by desirability approach
But after a specific C, nanoparticles act as an abrasive during cutting and negatively affect the surface finish [Lee et al., 2017]. The higher force and temperature of the uncoated tool can cause higher tool wear [Qin et al., 2016], which is responsible for higher surface roughness when the cutting parameters are fixed. In this work, the surface roughness produced by the coated carbide tool is less compared to the uncoated carbide tool under the same machining conditions.
From the main effect plot, it can be revealed that the average surface roughness obtained by the coated carbide insert is 0.77 µm, while, for the uncoated carbide insert the average surface roughness is 0.9 µm. Moreover, multi-response optimization is very common in any engineering problem and it facilitates the improvement of the overall system performance [Amrita et al., 2020]. Composite desirability of 0.9858 was achieved by the final optimization, which is very close to 1, indicating that this institution can obtain favorable results for the optimization of multiple responses completely [Ola et al., 2019].
Numerical Evaluation of Cutting Temperature and Chip
Temperature and chip formation modelling using FEM
In this study, the thermo-visco-plastic behavior of the specimen has been expressed using the J-C constitutive material model. Corresponding coating properties of the composite layer have been calculated according to the method used in a study by Yen et al. The geometry of the workpiece and the tool have been sketched taking into account the real dimension and the materials have been assigned.
In this particular machining process, two tool edges are involved in cutting, such as The tool consists of a CPE4RT and some triangular elements, but of variable length. Figure 4.4 Surface film condition for MQL on inclined and side tool surfaces In this study, VG 68 cutting oil and hybrid nanofluid were used as MQL fluid.
![Table 4.1 Johnson-Cook model and progressive damage parameters for Ti-6Al-4V [Wang and Liu, 2014]](https://thumb-ap.123doks.com/thumbv2/filepdfnet/10825786.0/110.892.128.789.599.752/table-johnson-cook-model-progressive-damage-parameters-wang.webp)
Experimental validation of the FE model
- Average chip-tool interface temperature
- Chip morphology
Fig.4.6 Chip tool interface temperature under (a) dry, (b) MQL with cutting fluid and (c) MQL with nano-fluid conditions in turning Ti-6Al-4V alloy with uncoated and coated carbide inserts wearing It can also be observed from Fig.4.6 that there is a clear difference in the cutting temperature distribution during machining from uncoated and coated carbide inserts. In the FEM, the temperature distribution at the chip-tool interface can be observed and the average temperature of the chip-tool interface is calculated.
The variations of average chip-tool interface temperature generated during machining and FEM for turning Ti-6Al-4V alloy from uncoated and coated carbide inserts are shown in Fig.4.7. The maximum discrepancy in average chip tool interface temperature from uncoated and coated carbide inserts was calculated and found to be 6.6% and 8.6%. Simulated and experimental (SEM) chips for machining in different environments for different tool materials are shown in Fig.4.8 and Fig.4.9.
Discussions on Experimental Results
- Chip morphology
- Cutting temperature
- Cutting force
- Tool wear and tool life
- Surface roughness
- Dimensional deviation
Turning of Ti-6Al-4V alloy from coated and uncoated carbide inserts was carried out by dry machining, single-pass MQL, two-pass MQL and two-pass MQL with nano-fluid. The performance of MQL with nano-fluid was better compared to conventional cutting fluid in terms of tool wear. In the case of a single jet, the tool life of the MQL hybrid nano-fluid tool is increased with dual cutting oil jet and dual jet.
In the case of single jet, double jet with cutting oil and double jet with hybrid nanofluid MQL coated carbide tool life increased by 15.6. In the case of DJMQL with nanofluid, the wear was shifted from the nose to the main flank surface. The effect of double jet MQL and nanofluid-based MQL on dimensional deviations was not found in the previous literature.
Conclusions and Recommendations
Conclusions
In addition, MQL with hybrid nano-fluid performs better compared to MQL with conventional cutting oil. iv) Statistical analysis indicated that process inputs (cutting speed, feed rate, depth of cut, nanoparticle concentration and tool type) have a significant effect on cutting temperature, cutting force and surface roughness when turning Ti-6Al-4V alloy under hybrid nano-fluid-based MQL. Empirical models for predicting the responses as a function of significant process inputs were formulated and validated based on the experimental data. Optimum cutting speed, feed rate, depth of cut and particle concentration and the tool type combination were found to be, 48.48 m/min, 0.1 mm/revolution, 0.5 mm, 1.07 vol % and coated tool for improving the machinability of Ti-6Al-4V alloy considering multi-objectives. f).
A finite element model (FEM) for the turning of Ti-6Al-4V alloy by carbide insert under different cooling environments was formulated and experimentally validated. For cutting temperature, simulated responses for turning through uncovered insert show better agreement with the experimental results. While, for chip morphology, simulated responses for turning through coated insert match better with the experimental results.
Recommendations
Hegab, H., Kishawy, H.A., Umer, U., Mohany, A. A Model for Nano-Additive Based Minimum Amount Lubrication Machining", International Journal of Advanced Manufacturing Technology, Vol. Kim, J.S., Kim, J.W., Lee , S.W. Experimental characterization of titanium alloy microend milling using cold gas nanofluid minimum lubrication", International Journal of Advanced Manufacturing Technology, Vol. Morgan, M.N., Barczak, L., Batako, A Minimum Lubrication (MQL) Fine Grinding Temperatures", International Journal of Advanced Manufacturing Technology, Vol.
Pervaiz, S., Anwar, S., Qureshi, I., Ahmed, N Recent advances in titanium alloy machining using minimum quantity lubrication (MQL) based techniques, International Journal of Precision Engineering and Manufacturing- Green Technology, Vol . 6 (1-2), pp Revuru, R.S., Posinasetti, N.R., Vsn, V.R., Amrita, M Use of cutting fluids in titanium alloy machining—a review", International Journal of Advanced Manufacturing Technology, Vol. Rotella, G., Dillon, O.W., Umbrello, D., Settineri, L., Jawahir, I.S. Effects of cooling conditions on surface integrity in Ti6Al4V alloy machining", Int International Journal of Advanced Manufacturing Technology, Vol.71, p. .
