Chip Compression Ratio Research Articles

Evaluation of lubrication mechanism of hybrid nanolubricants in turning hardened AISI D6 tool steel

Turning of hardened tool steels has posed a significant challenge for machining professionals. Usually, hardened tool steels are machined under dry with ceramic or PCBN inserts. However, dry machining imposes a condition where high cutting temperatures are developed, which becomes prohibitive when the part's geometric and dimensional accuracy is required. On the other hand, using mineral oil-based cutting fluid has encountered increasing restrictions because of its unsustainable nature. In this context, developing new sustainable lubri-cooling techniques, such as using vegetable oils blended with nanoparticles, could be an appropriate alternative. Thus, the main objective of this study was to investigate the performance of three different vegetable oil-based nanolubricants blended with three different nanoparticles (CuO, a-C:H, and CuO + a-C:H), applied under MQL when machining a quenched and tempered AISI D6 tool steel. For this purpose, facing turning trials were performed using solid PCBN inserts with the following cutting parameters: Vc = 100 m/min, ap = 0.3 mm, and f = 0.1 mm/rev. For comparison, facing turning tests were performed under dry and pure vegetable oil (without nanoparticles) and applied under MQL. Output variables included average surface roughness (Ra), flank wear (VBC), wear mechanisms of the cutting edge, chip shape, and chip compression ratio (Rc). The results showed that the vegetable oil-based nanolubricants applied under MQL improved the tribological conditions in the chip-tool and workpiece-tool interfaces, mainly in the case of CuO + a-C:H nanolubricant. In this case, it enhanced the lubricating action of the vegetable oil, decreasing cutting tool wear probably because of the combination of rolling mechanism, - provided by the CuO nanoparticles, and the formation of a protective film, supplied by the a-C:H nanoparticles.

Determination of Chip Compression Ratio for the Orthogonal Cutting Process

The chip compression ratio is the most important characteristic of various machining processes with chip generation. This characteristic enables the determination of kinetic and other energy loads on the tool and the machined material. This provides an overall evaluation of the machining process and the possibility of its subsequent optimization. This paper presents the results of determining this cutting characteristic by experimental method, analytical calculation, and numerical modeling. For the analytical calculation of the chip compression ratio, an analytical cutting model developed based on the variational principle of the minimum potential energy was used. A finite element model of orthogonal cutting was used for the numerical simulation of the above process characteristic. Experimentally, the chip compression ratio was determined by the ratio of the chip thickness to the cutting depth (undeformed cutting thickness). The chip thickness was determined by direct measurement using chip slices obtained during the cutting process. The Johnson–Cook constitutive equation was used as the machined material model and the Coulomb model was used as the friction model. The generalized parameters’ determination of the constitutive equation was performed through a DOE (Design of Experiment) sensitivity analysis. The variation range of these parameters was chosen based on the analysis of the effect of individual parameters of the constitutive equation on the chip compression ratio value. The largest deviations between the experimental and analytically calculated values of the chip compression ratio did not exceed 21%. At the same time, the largest deviations of simulated values of the indicated cutting characteristic and its experimental values did not exceed 20%. When comparing the experimental values of the chip compression ratio with the corresponding calculated and simulated values, the deviations were within 22%.

Extracting information from the cutting force signal to explain and exploit its discrepancy between up and down slot milling at the same chip thickness

In milling, different cutting forces can occur at the same undeformed chip thickness depending on process kinematics and feed. To clarify and exploit this phenomenon, which has not been reported in the technical literature, the cutting force was recorded during full-width orthogonal milling. The latter process was chosen as the same undeformed chip thickness is developed at certain tool rotation angles and at different feeds, thus allowing the exploration of the effect of these parameters on the cutting force. Using analytical methods to describe the cutting kinematics, the exact rotation angle of the tool corresponding to its engagement with the workpiece was calculated. In addition, the precise relationship between chip thickness and occurring cutting force in up and down slot milling at various feeds was determined. Herein, for increasing the accuracy, the tool path was considered as trochoidal rather than circular. In addition, analytical methods were developed to calculate the cutting force direction, shear angle and chip compression ratio. The measurements of the deformed chip thickness over the deformed chip length verified the assumptions and correctness of the developed analytical procedures. Additionally, based on a FEM simulation of the developed stress fields during material removal, the stress field depth parameter ds was introduced. Using ds and the calculated direction of the cutting force towards the instantaneous workpiece surface, regions of effective material strengthening or weakening were detected within the developing stress field during up and down milling respectively, which change the cutting force. In this way, the discrepancies between the cutting forces occurring in up and down milling at the same undeformed chip thickness and various feeds were clarified and process conditions were proposed to exploit them to reduce cutting loads and energy requirements.

Optimizing Machining Efficiency in High-Speed Milling of Super Duplex Stainless Steel with SiAlON Ceramic Inserts

Super duplex stainless steels (SDSSs) are widely utilized across industries owing to their remarkable mechanical properties and corrosion resistance. However, machining SDSS presents considerable challenges, particularly at high speeds. This study investigates the machinability of SDSS grade SAF 2507 (UNS S32750) under high-speed milling conditions using SiAlON insert tools. Comprehensive analysis of key machinability indicators, including chip compression ratio, chip analysis, shear angle, tool wear, and friction conditions, reveals that lower cutting speeds optimize machining performance, reducing cutting forces and improving chip formation. Finite element analysis (FEA) corroborates the efficacy of lower speeds and moderate feed rates. Furthermore, insights into friction dynamics at the tool–chip interface are offered, alongside strategies for enhancing SDSS machining. This study revealed the critical impact of cutting speed on cutting forces, with a significant reduction in forces at cutting speeds of 950 and 1350 m/min, but a substantial increase at 1750 m/min, particularly when tool wear is severe. Furthermore, the combination of 950 and 1350 m/min cutting speeds with a 0.2 mm/tooth feed rate led to smoother chip surfaces and decreased friction coefficients, thus enhancing machining efficiency. The presence of stick–slip phenomena at 1750 m/min indicated thermoplastic instability. Optimizing machining parameters for super duplex stainless steel necessitates balancing material removal rate and surface integrity, as the latter plays an important role in ensuring long-term performance and reliability in critical applications.

A novel finite element model for thermally induced machining of Ti6Al4V

Titanium alloys, including Ti6Al4V, are considered hard to cut materials due to their low thermal conductivity, low elastic modules and high chemical reactivity. This leads to high cutting forces and high surface roughness. Thermal assisted machining is used to improve the machinability of Ti6Al4V. To improve the performance of thermal assisted machining, this study investigates how are the cutting force, cutting zones temperatures, chip morphology, shear plane angle and strain rate are affected by the cutting speed and the heating element characteristics during thermally assisted machining of Ti6Al4V. A 2D numerical model simulating orthogonal cutting process was created using ABAQUS/Explicit software. In this model, Johnson Cook constitutive model was used to describe the material behavior during cutting process. Also, Johnson Cook damage model was used to simulate chip separation mechanism. After the verification of the model by comparison with results found in the literature, a number of simulations were run at different levels of four factors: cutting speed (40, 60, 80, 100, 120 and 140 m/min), heat source temperature (200, 400 and 600 °C), heating source distance from the cutting tool (0.3, 0.6 and 0.9 mm) and heating source size/diameter (0.6, 0.8 and 1 mm). Taguchi L18 orthogonal mixed level design was used to plan for simulation runs using Minitab software. ANOVA analysis was used to investigate the significance of the four factors. The response table of means and the main effect of means are used to compare between the four factors and find their ranking. Based on 95% confidence Interval (CI), the results show that cutting speed has a significant effect on cutting force, strain rate, chip compression ratio, cutting tool nose temperature, cutting tool and chip temperature in the secondary deformation zone, average chip thickness at peaks and average chip thickness at valleys and average pitch. This conclusion is based on the P-values which are << 0.05 and the contribution which reaches 99.01%. Similarly, based on P-values (< 0.05) and contributions (up to 12.16%), the heating source temperature has a significant effect on average chip thickness at valleys, chip compression ratio and strain rate. The cutting speed has Rank 1 among the four factors affecting cutting force, cutting zones temperatures, chip morphology, shear plane angel and stain rate. The effect of instantaneous heating directly before cutting process is negligible compared to the effect of plastic deformation and fracture mechanism in the cutting zone.

Analysis of chip compression ratio in turning of polyoxymethylene copolymer

The turning process is influenced by a synergy of various parameters that affect the machining mechanisms and the resulting process efficiency. Among these factors, the evaluation of chip morphology is of paramount importance and can often be quantified by the chip compression ratio. This key figure serves as a quantitative measure of the overall plastic deformation and provides information about the energy expended during cutting and the friction behavior at the interface between the chip and the cutting tool. This research is specifically concerned with modeling and analyzing the chip compression ratio during dry turning of polyoxymethylene copolymer (POM-C) using a polycrystalline diamond (PCD) tool. The experimental setup comprised a face-centered, central compound test in which three main parameters — depth of cut, feed rate and cutting speed - were adjusted to each other. After conducting the turning experiments and collecting the measurement data, a second-order mathematical model was formulated to establish the relationship between the turning parameters and the chip compression ratio. Statistical analysis of the results revealed notable main effects of depth of cut and feed rate, a quadratic effect of depth of cut and an interaction effect between feed rate and cutting speed, all of which have a significant effect on the change in chip compression ratio.

Selection of the numerical formulation for modeling the effect of tool cutting edge microgeometries in machining of Ti6Al4V titanium alloy

The Finite-element method (FEM) is often used to simulate the metal machining process. Currently, several formulations are used in metal cutting simulation, such as Lagrangian (LAG), Eulerian (EUL), Arbitrary Lagrangian–Eulerian (ALE), and Coupled Eulerian–Lagrangian (CEL). The selection of the numerical formulation that better reproduces the material separation in machining to form the chip is a critical issue. This is quite important when the ratio between the uncut chip thickness and the cutting edge microgeometry, often represented by a cutting edge radius, is very low. In this study, orthogonal cutting of Ti6Al4V titanium alloy using different tool edge microgeometries is investigated using LAG and CEL approaches. In the case of LAG approach, two types of cutting models were develop: one using a sacrificial layer (hereby called LAG-SL), and another without sacrificial layer (hereby called LAG-nSL). The cutting models have included a constitutive model (both plasticity and damage) considering the effects of strain, strain rate, temperature, and state of stress, which have proved to be accurate enough to represent the mechanical behavior of the Ti6Al4V alloy in machining. Comprehensive comparisons between CEL and LAG-based cutting models and experimental results are carried out in terms of chip morphology, forces, and residual stresses. When compared to the experimental results, LAG-nSL model gives the best predictions of the maximum chip compression ratio (CCRm) with an error of 9.5%, cutting force (12.8%) and thrust force (9.3%) than the other two models. In the case of the of residual stress profiles, LAG-SL offers good predictions of the maximum compressive residual stress by a preference ratio of 75%. Although CEL yields the worst predictions of chip morphology and forces, it is preferred from the perspective of the thickness of the layer affected by residual stress.

Chip morphology and tool wear investigation in high-speed machining of AZ61 magnesium alloys using vegetable-oil based cutting fluid

ABSTRACT Lightweight alloys play a vital role in the development of automotive, biomedical and aerospace industries as well as other industrial sectors. The current study investigates the machinability of AZ61 magnesium alloy within a vegetable-oil-based MQL environment through high-speed orthogonal cutting. A tool wear and chip morphology examination are conducted along a full factorial experimentation to allow for adequate machinability testing. The usage of Grey Relational Analysis was invoked to allow for a multi-variant optimisation of input parameters such as MQL flow rate, cutting speed, and feed based on output responses, such as chip compression ratio, chip segmentation ratio, tool-chip contact length, and shear angle as well as tool wear evolution. Through the analysis of the formulated signal-to-noise data, it was found that the optimal cutting parameters were an MQL flow rate of 80 ml/h, cutting speed of 250 m/min and feed of 0.3 mm/rev. The optimal cutting conditions resulted in a Grey Relational Grade improvement of 0.177 as compared to the referenced experimental trail. The analysis of variance further concluded that the feed was the highest contributing input parameter at 38.04% followed by the MQL flow rate and the cutting speed.

Constitutive modelling of Ti6Al4V alloy fabricated by laser powder bed fusion and its application to micro cutting simulation

Although there is a rising interest in applications of metal additive manufacturing (AM) for fabrication of highly complex metallic components, poor surface quality of AM parts is an inherent limitation of this technology. Therefore, post-process machining operations are frequently performed to meet the necessary requirements for the application. When compared to wrought Ti6Al4V, the distinct metallurgical and mechanical characteristics of Ti6Al4V fabricated by laser powder bed fusion (LPBF) can lead to very different mechanical behavior, thus different machinability. Therefore, to properly perform the numerical modelling of the cutting processes, it is important to accurately define material mechanical behavior of LPBF Ti6Al4V. This study presents the experimental determination of the coefficients of the Johnson-Cook (J-C) constitutive model and the numerical simulation of orthogonal micro cutting process of hot isostatic pressed (HIP) LPBF Ti6Al4V. Besides, the results were also compared to the wrought Ti6Al4V. For that purpose, quasi-static and dynamic behaviors of wrought and LPBF Ti6Al4V were investigated by quasi-static tensile tests at several temperatures (0.001 s−1 at 20, 400, 600 °C) and at high strain rates using the split Hopkinson pressure bar (SHPB) tests (∼1000-5000 s−1 at 20, 400 °C). Orthogonal micro cutting simulations were performed using experimentally obtained J-C model of wrought and LPBF Ti6Al4V. A series of orthogonal micro cutting tests at different cutting speeds (75, 100, 150 m/min) and uncut chip thickness values (2.5, 5, 7.5, 10 μm) were performed to compare the measured forces and chip compression ratio (CCR) with those obtained by simulation. Good predictions of main cutting force and maximum CCR were obtained for both wrought and LPBF Ti6Al4V under different cutting conditions. Several critical points to be considered for better prediction of thrust force and chip geometries in future studies were highlighted.

Machinability analysis of Ti-6Al-4V under cryogenic condition

Aerospace alloys are termed as hard to cut materials owing to their low thermal conductivity, high temperature strength and elevated chemical reactivity. Cryogenic conditions can be effectively deployed to improve the machinability and productivity while addressing environmental and sustainability concerns connected with high tool wear and the use of conventional cutting fluids. Current work was undertaken to develop a novel tool wear map under cryogenic condition using cutting speed and feed rate as input variables. The developed map was demarcated into regions of low, moderate and high tool wear zones in addition to an unusually high wear zone, termed as avoidance zone existing between cutting speeds of 65–95 m/min and feed rates of 0.18–0.22 mm/rev. Characterization of developed map in terms of tool chip contact length revealed its direct relationship with cutting speed and feed rate accounting for the formation of different wear regions. Elemental analysis of avoidance zone detected high presence of TiN which results in larger tool chip contact length owing to its higher thermal conductivity. Chip morphology characterization highlighted an increase in chip compression ratio and decrease in shear angle due to the reduction of effective tool rake angle, further elevating the cutting zone temperature promoting wear. SEM and EDS spot analysis indicated the presence of adhesive and diffusion-dissolution wear mechanisms as the tool wear progresses. Comparative analysis with dry condition indicated that tool life is enhanced up to 100% using cryogenic media. Analysis of cryogenic tool wear map underscored the importance of careful choice of machining parameters in terms of increase in MRR up to 36% and tool life up to 58%. Overall, cryogenic tool wear map presents graphical interpretation of the machinability of Ti–6Al–4V in terms of tool wear.

Sustainable Vegetable Oil-Based Minimum Quantity Lubrication Assisted Machining of AZ91 Magnesium Alloy: A Grey Relational Analysis-Based Study

The implementation of magnesium alloys in a multitude of industries has been proven to be a mere effect of their attractive light weight, corrosion resistant, and biodegradable properties. These traits allow these materials to portray an excellent sustainable machinability. However, with increasing demand, it is essential to explore sustainable means of increasing production while mitigating reductions in sustainability. The current work aims to assess and optimize the high-speed machinability of AZ91 with the use of a vegetable oil-based minimum quantity lubrication (MQL) system using the grey relational analysis (GRA) on the basis of chip morphology and tool wear. The investigation entailed a full factorial design with MQL flow rate, cutting speed, and feed rate as the control parameters and flank wear, land width, chip contact length, saw-tooth pitch, chip segmentation ratio, chip compression ratio, and shear angle as the output responses. The optimal control parameters predicted and experimentally confirmed were an MQL flow rate of 40 mL/h, cutting speed of 300 m/min, and feed rate of 0.3 mm/rev. The usage of said optimal parameters results in a grey relational grade improvement of 0.2675 in comparison to the referenced first experimental run. Moreover, the MQL flow rate was regarded as the critical variable with a contribution percentage of 20% for the grey relational grade.

INVESTIGATION OF CHIP MORPHOLOGY ON TURNING OF MONEL UNDER NANOGRAPHENE AND NANO CuO COOLANTS

This paper deals with experimental investigation on chip formation of machining of Monel K500 and its characteristics are studied. Two different nanocutting fluids namely nanoCuO and nanographenes are used for turning operation and the performance of the two cutting fluids is evaluated and the corresponding responses are recorded for the selection of better cutting fluid. This experiment is carried out with the help of SEM which picturizes the microstructure and surface distribution of the chips. The various output responses like chip thickness, chip compression ratio, and surface roughness are portrayed. The desirable effects on the properties of the machined material obtained by the variation of process parameters like cutting speed, cutting depth, and feed rate are analyzed. Results show that the thickness of chips (corresponding metal removal rate) is reduced considerably by 10–15% and the surface roughness is reduced by 20–30% when nanographene cutting fluids are used.

Effects of tool angles and uncut chip thickness on consumption of plastic deformation energy during machining process

Research on the underlying mechanism that controls the chip deformation and energy consumption is a basis to instruct the cutting process planning and improve the machining efficiency. The metal cutting process can be treated as purposeful separation of workpiece material, and the stress state located at the tool tip has great effect on the fracture of material being removed. Through studying the relationship between the stress triaxiality and chip formation process, this paper aims to reveal the effects of tool rake angle, inclination angle and uncut chip thickness on chip deformation behavior and associated energy consumption during machining of 1045 steel based on finite element method (FEM). A two-dimensional FEM model for orthogonal cutting is developed to study the effect of tool rake angle and uncut chip thickness on chip deformation, while a three-dimensional FEM model for oblique cutting is developed to investigate the effect of tool inclination angle. The parameter of chip compression ratio (CCR) is adopted to assess the chip plastic deformation and energy consumption under varied machining conditions. The cutting force component calculated based on CCR is compared with the total cutting force to demonstrate the dominant role of chip plastic deformation in cutting energy consumption. The results indicate that larger rake angle and smaller inclination angle of cutting tools as well as larger uncut chip thickness lead to increase of stress triaxiality near the tool tip, which can reduce the material fracture strain and be beneficial for the separation of material being removed from the bulk workpiece. This paper will be attractive from both practical and fundamental perspectives devoted to instructing the optimization of cutting parameters to improve the processing efficiency and reduce the energy consumption.

Simulation and analytical studies of chip formation processes in the cutting zone of titanium alloys

The low machinability of titanium alloys is determined by the physical, mechanical, and chemical properties of these materials and their mechanical characteristics. It is also evident in the hardened state of the material being processed during cutting, as well as in the initial state. This phenomenon is caused by thermodynamic parameters that determine the properties of titanium material at elevated temperatures. The peculiarities of the cutting and chip formation processes during titanium alloy machining are presented in this article. The peculiarity of the described approach is the analysis of the results of simulation modeling of cutting in Deform 2D software. It is proved that the frictional factor in the formation of the thermal characteristics of the cutting process, which arises as a result of the chip sliding along the tool, dominates the load factor (caused by force and deformation processes in the chip root). It has been established that the length of contact between the chips and the tool’s rake face has a certain tendency to change: the contact length first increases and then decreases with increasing cutting speed. An analysis of the dependence of the chip compression ratio on changes in cutting speed has shown that with an increase in cutting speed, the average value of the compression ratio practically does not change, but the amplitude of its oscillation increases significantly, which is equivalent to a change in the shear angle. This parameter changes dynamically due to the adiabatic nature of chip formation

Experimental Investigation on the Machinability Improvement in Magnetic-Field-Assisted Turning of Single-Crystal Copper.

The single-point diamond-turning operation is a commonly used method for ultra-precision machining of various non-ferrous materials. In this paper, a magnetic field was introduced into a single-point diamond-turning system, and magnetic-field-assisted turning experiments were carried out. The results revealed that the magnetic field affects the metal-cutting process in the form of the cutting force, chip morphology, and surface quality. Compared with traditional turning, magnetic-field assisted turning increases the cutting force by 1.6 times, because of the additional induced Lorentz force, and reduces the cutting-force ratio and friction coefficient on the rake surface by 16%, with the improved tribological property of the tool/chip contact-interface. The chip morphology in the magnetic-field-assisted turning shows the smaller chip-compression ratio and the continuous side-morphology. With the magnetoplasticity effect of the metal material and the friction reduction, magnetic-field-assisted turning is helpful for improving metal machinability and achieving better surface-quality.

Determination of the Shear Angle in the Orthogonal Cutting Process

Determination of the shear angle by experimental and analytical methods, as well as by numerical simulation, is presented. Experimental determination of the shear angle was performed by analyzing the chip roots obtained by the method of cutting process quick stop through purposeful fracture of the workpiece in the area surrounding the primary cutting zone. The analytical determination of the shear angle was carried out using the chip compression ratio and was based on the principle of a potential energy minimum. Measurement of the shear angle in the numerical simulation of orthogonal cutting was performed using the strain rate pattern of the machined material at the selected simulation moment. It was analyzed how the parameters of the Johnson–Cook constitutive equation and the friction model affect the shear angle value. The parameters with a predominant effect on the shear angle were determined. Then the generalized values of these parameters were established with a software algorithm based on identifying the intersection of the constitutive equation parameter sets. The use of generalized parameters provided the largest deviation between experimental and simulated shear angle values from 9% to 18% and between simulated and analytically calculated shear angle values from 7% to 12%.

Regime features of austempered ductile iron cutting

Machining regimes and sub-regimes of dry straight finish-turningof structural austempered ductile iron (ADI) with low cBN-content PcBN-based cutting inserts were examined. The global and local characteristics of TC contact and chip formation processes tied to this turning, as estimated by Katuku [Journal of Manufacturing Processes 78, 2022, 288–307], were used in this attempt. The significance of each prominent feature of these regimes was discussed from multiple perspectives. Across primary deformation zones (PDZs) and secondary deformations zones (SDZs), drag-controlled (or shock-induced) and defect-controlled plasticity regimes are, in turn, dominant and secondary. Coupled shear localisations in PDZs and SDZs occur via strain softening for cutting speeds beyond ~175 m min−1. BUE softening turns active at ~650 °C (~125 m min−1). Two bordering machining regimes emerged in close link with this cut-off temperature alongside a ⁓16 % cut-off SDZPDZ softening-degree, to name a few. Higher SDZPDZ softening-degree and moderately low mean contact stresses (high TC contact-length factor), TC contact temperature and sliding-friction coefficient, prevailing for Machining-regime-I (50–150 m min−1), hint at lower-pace wear regimes. The opposite conditions, standing for Machining-regime II (200–800 m min−1), suggest temperature-affected and stress-backed higher-pace wear regimes. Mean total energy levels (3476–7122 and 4364–4596 MPa) imply residual stresses built-up and microstructure damage below the machined surface. Machining sub-regimes are linked to solid-state phase transformations in PDZs/SDZs. Shear energy stored in PDZs/SDZs (166–291/1.5–43 MPa and 159–134/33–72 MPa) matches these transformations. Machining sub-regimes are sensitive to shallow variations in TC settings past ~175 m min−1. Powder lubrication by smeared-out graphite nodules is worthless in Machining-regime II. Cutting speeds of 150–400 m min−1 (TC contact temperature of ~685–930 °C and chip compression ratio of 3.4–2.32), sampled at the confluence of Machining-regimes I and II, are recommended for dry straight finish-turning structural ADI with low cBN-content PcBN-based cutting inserts.

Evaluation of the efficiency of an ultrasonic atomization-based coolant (uACF) spray system in external turning using different nozzle tips

Recently, the atomization-based coolant (ACF) spray system has shown promising cooling and lubrication effects in machining, but its effectiveness on machining processes has not yet been adequately studied. This paper proposes a new compact system which is developed based on the ultrasonic atomization of metalworking fluid used in machining and called the Ultrasonic Atomization-based Cutting Fluid (uACF) spray system. This study aims that, on turning AISI 1050 plain carbon steel, the effectiveness of the uACF spray system made with simple, economical, and accessible equipment is evaluated by comparing it with different cooling conditions. In this study, three different nozzle outlet tips called long wide nozzle (LWN), long narrow nozzle (LNN), and flat wide nozzle (FWN) have been used in the uACF system. Several experiments have been conducted to study the effects of the nozzle outlet tips on performance characteristics such as the main cutting force (Fc), cutting temperature (Tc), average surface roughness (Ra), and chip compression ratio (ζ). In addition, similar tests were also made for dry (DRY), compressed air (AIR), and dense coolant spraying (SPR) conditions and the test results were compared with each other. It was determined that there were statistically significant differences between the conditions of the uACF system and other classical cooling conditions. The uACF system created significant differences, especially in Fc and Tc. It was determined that the use of FWN in the uACF system was more effective than SPR on Fc, and was as effective as SPR on Tc. While the fluid consumption rate of FWN in the uACF system is 1.5 ml/min, the SPR has a fluid consumption of 20 ml/min. It has been found that the uACF spray system with a lower fluid consumption outperforms other cooling conditions, thus further enhancing the performance of the environmentally friendly production process. The effectiveness and potential of the uACF spray system on machining processes possess high efficiency and cost-effective benefits to substitute the traditional cooling-lubrication applications. The results obtained from this study have the potential to be helpful to other researchers for a similar type of study and a guide for further research on the development of different cooling systems.

Modelling and Optimization of Machining of Ti-6Al-4V Titanium Alloy Using Machine Learning and Design of Experiments Methods

Ti-6Al-4V titanium is considered a difficult-to-cut material used in critical applications in the aerospace industry requiring high reliability levels. An appropriate selection of cutting conditions can improve the machinability of this alloy and the surface integrity of the machined surface, including the generation of compressive residual stresses. In this paper, orthogonal cutting tests of Ti-6Al-4V titanium were performed using coated and uncoated tungsten carbide tools. Suitable design of experiments (DOE) was used to investigate the influence of the cutting conditions (cutting speed Vc, uncut chip thickness h, tool rake angle γn, and the cutting edge radius rn) on the forces, chip compression ratio, and residual stresses. Due to the time consumed and the high cost of the residual stress measurements, they were only measured for selected cutting conditions of the DOE. Then, the machine learning method based on mathematical regression analysis was applied to predict the residual stresses for other cutting conditions of the DOE. Finally, the optimal cutting conditions that minimize the machining outcomes were determined. The results showed that when increasing the compressive residual stresses at the machined surface by 40%, the rake angle should be increased from negative (−6°) to positive (5°), the cutting edge radius should be doubled (from 16 µm to 30 µm), and the cutting speed should be reduced by 67% (from 60 to 20 m/min).

A Fuzzy Logic Model for the Analysis of Ultrasonic Vibration Assisted Turning and Conventional Turning of Ti-Based Alloy.

Titanium and its alloys are largely used in various applications due its prominent mechanical properties. However, the machining of titanium alloys is associated with assured challenges, including high-strength, low thermal conductivity, and long chips produced in conventional machining processes, which result in its poor machinability. Advanced and new machining techniques have been used to improve the machinability of these alloys. Ultrasonic vibration assisted turning (UVAT) is one of these progressive machining techniques, where vibrations are imposed on the cutting insert, and this process has shown considerable improvement in terms of the machinability of hard-to-cut alloys. Therefore, selecting the right cutting parameters for conventional and assisted machining processes is critical for obtaining the anticipated dimensional accuracy and improved surface roughness of Ti-alloys. Hence, fuzzy-based algorithms were developed for the ultrasonic vibration assisted turning (UVAT) and conventional turning (CT) of the Ti-6Al7Zr3Nb4Mo0.9Nd alloy to predict the maximum process zone temperature, cutting forces, surface roughness, shear angle, and chip compression ratio for the selected range of input parameters (speed and depth-of-cut). The fuzzy-measured values were found to be in good agreement with the experimental values, indicating that the created models can be utilized to accurately predict the studied machining output parameters in CT and UVAT processes. The studied alloy resulted in discontinued chips in both the CT and UVAT processes. The achieved results also demonstrated a significant decline in the cutting forces and improvements in the surface quality in the UVAT process. Furthermore, the chip discontinuity is enhanced by the UVAT process due to the higher process zone temperature and the micro-impact imposed by the cutting tool on the workpiece.