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Dimensional tolerances for high-speed-machined aluminum products continue to tighten due to the demand for automated assembly of complex monolithic parts in aerospace and other industries. Understanding the contribution of inherent residual stress in wrought Al 7050-T7451 plate, common in aircraft manufacture, to distortion of high-aspect-ratio machined parts is critical but remains problematic due to the alloy's low residual stress magnitude over large geometries. Prior investigations into residual stress effects on machined part distortion suffer inadequate characterizations of the wrought material stress field, either because of low fidelity due to "slitting" methods, confounding effects in machined-layer removal methods, or small sample size when using neutron diffraction (ND). In this work, inherent residual stress is measured via ND at 860 locations in a 90.5 mm thick Al 7050-T7451 plate having dimensions 399 mm in the rolling direction and 335 mm in the transverse direction. Unlike prior studies, the ND residual stress is reconstructed using an iterative algorithm to ensure fully compatible, equilibrated 3D field prior to examining its effect on distortion. The findings from simulations and experiments show that inherent residual stress alone could distort a high-aspect-ratio part beyond aerospace industry requirements, that slitting measurements may not sufficiently characterize residual stress for predicted distortion, and that parts machined from different plate thickness locations could exhibit reversed distortion patterns. Thus, research into distortion prediction that considers machining should carefully characterize and reconstruct inherent residual stress so that the coupled machining effects are accurately modeled. [ABSTRACT FROM AUTHOR]

Machined surface localization tends to occur due to the impact of thermo-plastic propagation effect under high cutting speed, leading to the machined surface evolution from deformed layer to white layer. To investigate the thermo-plastic characteristics of machined surface localization in high-speed machining, the formation model of machined surface layer was further developed through considering the propagation effect of thermo-plastic shear wave. The continuum governing equations and the constitutive relations of the rigid-plastic and thermo-plastic zones were established. Considering the energy dissipation states in the rigid-plastic and thermo-plastic zones, the propagation angle of thermo-plastic shear wave, the critical surface energy of white layer formation, and its corresponding surface layer thickness were yielded and verified through the high-speed machining experiment of rail steel and the microscopic examinations. On this basis, both stable and unstable solutions for the dependent variables were explicitly solved through the perturbation analysis method. The thermal and mechanical coupling mechanisms of the dependent variables which involve deformation, stress, temperature, and energy in the time-spatial domain during machined surface localization were further discussed with the numeral solutions. The numeral solutions and the perturbation solutions reasonably revealed that the machined surface localization experienced a thermo-plastic transformation process from stability to instability in the whole time-spatial domain. [ABSTRACT FROM AUTHOR]

Nanofluids play an important role in machining processes for lubrication and cooling action. However, conventional fluids put the environment and operator health in risk due to its hazardous nature. This paper attempts to develop and characterize a novel sustainable and eco-friendly nanofluids for machining applications. In this study, deionized water-based Al2O3, TiO2 and MWCNT nanoparticles dispersed nanofluids and its hybrids Al2O3–TiO2 (50:50) and Al2O3-MWCNT (90:10) with varying concentration (0.5, 1.0, 1.5 and 2.0 vol%) having sodium lauryl sulfate as surfactant were developed and characterized for rheological, thermal and wettability properties at near room temperature. The experimental results show that nanofluid's thermophysical properties were better than the base fluid. The thermal conductivity of all the nanofluids produced in this study is more than 0.611238 W/m K which is more than the thermal conductivity for deionized water. Similarly, surface tension obtained for various nanofluids is comparatively lower than deionized water, i.e., 0.072 N/m. As the concentration of nanoparticles increases from 0.5 to 1.5 vol%, it leads to an increase in thermal conductivity, but the increase of nanoparticles concentration beyond 2% has a very minimal effect on thermal conductivity. The rate of transmittance % is as follows: 0.5 vol% > 1.0 vol% > 1.5 vol% > 2.0 vol%. It has been observed that zeta potential values are above ± 30 mV, thus indicating a stable formation of nanofluids due to non-agglomeration of nanoparticles. Hence, the following properties of nanofluids will help in high-speed machining applications. [ABSTRACT FROM AUTHOR]

The aim of this paper was to develop and verify a method for evaluating the high-performance milling of Inconel 718 alloy under accelerated tool wear conditions. The method considered parameters such as cutting-force components, total machine power consumption, cutting-edge wear, and material removal rate. The study compared high-feed milling and plunge milling, using sets of cutting parameters that are appropriate for both techniques. The results indicate that high-feed milling was more efficient, achieving higher material removal rates and lower tool wear. On the other hand, plunge milling was characterized by a lower axial force component (Fz), which can positively affect machining accuracy. The paper highlights that the proposed evaluation method can also be applied to other hard-to-machine materials, and plunge milling offers a competitive alternative for roughing operations in the milling of Inconel 718 alloy. [ABSTRACT FROM AUTHOR]

Due to its exceptional mechanical and chemical properties at high temperatures, Inconel 718 is extensively utilized in industries such as aerospace, aviation, and marine. Investigating the flow behavior of Inconel 718 under high strain rates and high temperatures is vital for comprehending the dynamic characteristics of the material in manufacturing processes. This paper introduces a physics-based constitutive model that accounts for dislocation motion and its density evolution, capable of simulating the plastic behavior of Inconel 718 during large strain deformations caused by machining processes. Utilizing a microstructure-based flow stress model, the machinability of Inconel 718 in terms of cutting forces and temperatures is quantitatively predicted and compared with results from orthogonal cutting experiments. The model's predictive precision, with a margin of error between 5 and 8%, ensures reliable consistency and enhances our comprehension of the high-speed machining dynamics of Inconel 718 components. [ABSTRACT FROM AUTHOR]

Grinding is one of the most complex techniques of removing material from parts by the countless number of hard and sharp abrasive grains. Grinding creates a substantial amount of heat, which causes surface or subsurface damage, thermal damage, change in the metallographic structure of the material surface. In order to lesson these phenomena, cutting fluids are frequently used in the grinding zone. Minimum Quantity Lubrication (MQL) was suggested as a cost-effective and environmentally friendly lubrication for reducing heat and the expenses of grinding fluid. Despite the fact that MQL plays a crucial role in increasing machining performance, reviews on its use in high-speed machining are conflicted. This review article examines some of the most frequent nanofluids used in MQL systems during grinding processes. Nanofluids in MQL technique are a cutting-edge and eco-friendly approach that substitutes both traditional MQL and flood coolant in the grinding process. The effects of nanofluids on workpiece surface roughness, tangential force, coefficient of friction, G-ratio, grinding specific energy, wheel wear, grinding temperature, workpiece hardness and residual stress are thoroughly discussed and the findings were compared. After reading this review article, one may quickly gain an overview of existing research in the fields of nanofluids. Finally, this study looks at the thermo-physical characteristics of different nanofluids such as contact angle, thermal conductivity, and viscosity. [ABSTRACT FROM AUTHOR]

The study of chip morphology during high-speed milling is crucial in determining processing quality, but the relationship between chip formation mechanisms and process parameters in titanium alloy high-speed machining has been a difficult issue. This paper investigates milling force and temperature variation, as well as chip morphology and surface quality after milling to improve workpiece surface quality and machining efficiency and provide guidance on selecting milling parameters. Factorial analysis confirms that milling speed worsens the serrated layer of chips. In addition, the experiment confirms the influence of tool rake angle on shear strain in the milling zone, the impact of rotational speed on tool wear, and the effect of tool wear on chip morphology. The results show that increasing milling speed worsens chip serration and increases tool wear. [ABSTRACT FROM AUTHOR]

The Ti-5Al-5V-5Mo-3Cr (Ti-5553) alloy is a relatively novel difficult-to-cut material with limited machinability and tool life analysis available in the literature, and hence requires further investigation. This study focuses on the machining and tribological performance of Ti-5553 under high-speed finish turning (150 m/min, 175 m/min, and 200 m/min) via novel mono/bi-layered PVD-coated WC tools. A base AlTiN coating is used as the reference monolayer coating, with AlCrN, diamond-like ta-C, and TiAlSiN coatings each deposited on top of a base AlTiN coating, totaling four separate coated tools (one monolayer and three bi-layer). Tool life, cutting forces, workpiece surface quality, and tribological chip analysis are among the subjects of investigation in this study. Overall, the AlTiN/AlCrN coated tool outperformed all the other combinations: an improvement of ~19% in terms of tool life in reference to the base AlTiN coating when averaging across the three speeds; lowest surface roughness values: ~0.30, 0.33, and 0.64 µm; as well as the lowest chip back surface roughness values: ~0.80, 0.68, and 0.81 µm at 150, 175, and 200 m/min, respectively. These results indicate that the AlTiN/AlCrN coating is an excellent candidate for industrial applications involving high-speed machining of Ti-5553. [ABSTRACT FROM AUTHOR]

AISI 4340 is a medium-carbon low-alloy steel that has gained distinctive attention due to its advanced properties including high strength, high toughness, and heat resistance. This has led to its commercial usage in a wide variety of industries such as construction, automotive, and aerospace. AISI 4340 is usually machined in a hardened state through a hard-turning process, which results in high heat generation, accelerated tool wear, low productivity, and poor surface quality. The application of high-speed machining helps improve the material removal rate and surface finish quality, yet the elevated temperature at the cutting zone still poses problems to the tool's lifespan. Apart from using advanced cutting tool materials, which is costly, researchers have also explored various cooling methods to tackle the heat problem. This paper presents a review of a sustainable cooling method known as minimum quantity lubrication (MQL) for its application in the high-speed turning of AISI 4340 steel. This study is centered on high-speed turning and the application of MQL systems in machining AISI 4340 steel. It has been observed that the hard part turning of materials with a hardness exceeding 45 HRC offers advantages such as improved accuracy and tighter tolerances compared to traditional grinding methods. However, this process leads to increased temperatures, and MQL proves to be a viable alternative to dry conditions. Challenges in optimizing MQL performance include fluid penetration and lubrication effectiveness. [ABSTRACT FROM AUTHOR]

To investigate the effect of drilling speed on the molecular dynamics and subsurface defect evolution mechanism of 3C-SiC single crystals, a coupled molecular dynamic model for drilling is established. A multi-scale molecular dynamic potential energy function is established by combining the variational potential energy between C–Si bonds, based on this, the mechanical response coupling model is developed. By analyzing factors such as molecular dynamics temperature and periodic boundaries, a molecular dynamic differential ensemble environment drilling is constructed to achieve a constant temperature and pressure simulation environment for the evolution of sub-surface defects in single crystal 3C-SiC molecular dynamics. At drilling velocities of 30 m/s, 60 m/s, and 90 m/s, dislocation exchange occurs that the load stability is affected. When the drilling reaches a certain depth, the load tends to be constant, with values of 5.22 × 104 eV/Å, 3.36 × 104 eV/Å, and 0.58 × 104 eV/Å. Load changes during differential drilling impact single crystal 3C-SiC irreversibly. By comparing and analyzing the simulation results at different drilling speeds, it offers ideas for understanding the material response of single crystal 3C-SiC during high-speed machining from the point of view of dislocation energy changes. [ABSTRACT FROM AUTHOR]

Inconel 657, also known as 50Cr-50Ni, is a high-temp, corrosion-resistant Ni-Cr alloy with excellent fuel-ash corrosion resistance against sulfur and vanadium. To make components from Inconel 657, it undergoes casting and machining for dimensional accuracy and surface finish. This study explores the effect of cutting speed on tool wear in turning Inconel 657, focusing on carbide and CBN tools. Higher cutting speeds led to increased flank wear for both tools. Carbide tool wear rose by 16% and 25% at 60 and 120 m/min compared to 30 m/min. CBN tool wear increased by 15%, 29%, and 66% at 120, 250, and 400 m/min compared to 60 m/min. CBN inserts showed 39% less wear than the carbide tool at 60 m/min and 35% less at 120 m/min. Therefore, the carbide tool suits low-speed turning, while the CBN tool is ideal for high-speed machining operations. [ABSTRACT FROM AUTHOR]

This paper presents the experimental results of a study investigating the impact of machining parameters on 3D surface roughness after rough, dry milling. The following 3D roughness parameters were analysed: Sa (arithmetic mean height), Sq (root mean square height), Sz (maximum height), Sku (kurtosis), Ssk (skewness), Sp (maximum peak height), and Sv (maximum pit height). Roughness measurements were made on the end face of the specimens. Additionally, 3D surface topography maps and Abbot-Firestone material ratio curves were generated. Carbide end mills with variable rake and helix angles were used in the study. Experiments were conducted on AZ31B magnesium alloy specimens using a contact-type profilometer. The machining process was conducted using the parameters of so-called high-speed machining. Three variable technological parameters were analysed: cutting speed vc, feed per tooth fz, and axial depth of cut ap. The results showed that the surface roughness of the rough-milled specimens depended to a great extent on the tool geometry and applied machining parameters. Feed per tooth was found to have the greatest impact on surface roughness parameters. Lower values of the analysed surface roughness parameters (and therefore higher surface quality) were obtained (in most cases) for the tools with a rake angle γ of 5° and a helix angle λs of 50°. The results provided both theoretical and practical knowledge about the achievable surface roughness after rough milling using tools with different tool blade geometry. It was shown that rough milling is an effective and efficient type of machining for the AZ31B alloy. [ABSTRACT FROM AUTHOR]

This study examines the process of optimising machining parameters in the turning of EN8 steel. The PROMETHEE-II multicriteria decision-making technique is utilised for this purpose. The analysed machining variables consist of Material Removal Rate (MRR), Surface Roughness (SR), Acceleration (Ac), and Tool Wear (TW). These variables are influenced by the cutting speed (Vc), Feed Rate (FR), and Depth of Cut (DoC) which serve as input parameters. The experimental trials were performed utilizing Taguchi's L27 orthogonal array on a CNC lathe. The ANOVA analysis showed that Vc had the most substantial effect on MRR, SR, and Ac, whereas FR had the greatest influence on TW. The PROMETHEE-II approach determined that the most favourable machining settings are a cutting speed (Vc) of 200 m/min, an FR of 0.08 mm/rev, and a DoC of 0.2 mm. Given these circumstances, the MRR achieved a value of 2.887 cubic millimetres per second, the SR was minimized to 0.744 micrometres, the Ac was decreased to 0.026 meters per second squared, and the TW was restricted to 0.026 millimetres. The study finds that PROMETHEE-II is a highly successful method for optimizing multiple machining reactions, resulting in substantial enhancements in machining performance. [ABSTRACT FROM AUTHOR]

Due to their homogeneity and excellent ratio between load capacity and weight, thinwalled aluminum structures are used as structural parts in the aerospace, automotive and military industries. The manufacture of these thin-walled structures is mainly done by removing a large amount of material from full raw pieces, sometimes up to 95% of their initial mass. Because of a large volume of material removing, it is necessary to achieve high productivity, which is limited by the lack of rigidity of the thin walls of these structures. As a result, errors occur, while reducing accuracy and machining quality. The main subject and objective of this paper is related to the optimization of high-speed machining parameters of linear thin-walled structures made of aluminum alloy Al7075 from the aspect of surface quality of processed superficial as a goal function. For this purpose, experiments were carried out based on which conclusions were made of the influence of input parameters on the surface roughness. [ABSTRACT FROM AUTHOR]

The analysis focuses on how the physical parameters of the attachment–workpiece and tool–chuck systems affect the stability when milling aviation materials that are hard to machine. Methods of stabilizing the milling process in terms of vibration are outlined, as well as means of increasing the productivity without damage to the equipment. Examples are given of stable and unstable machining of titanium alloy by end mills and its influence on the cutting process. [ABSTRACT FROM AUTHOR]

To curtail the negative effects of traditional flood machining, dry cutting using carbide tools has emerged as a prominent alternative for manufacturers, owing to its low cost and phenomenal surface qualities. In line with this view, high-speed machining of high-strength AISI 4340 alloy steel was carried out using multilayer Al2O3/TiCN-CVD and TiAlN/AlCrN-PVD carbide tools in a dry environment. The experimental scheme was adopted, as per Taguchi's L18 orthogonal array, to investigate the two most crucial machinability aspects, namely tool life and surface roughness. An analysis of variance (ANOVA) was performed on the obtained data, and it was inferred that the feed rate exhibited the strongest effects on both the tool life and surface roughness, with corresponding percentage contributions of 46.22% and 68.96%, respectively. The longest tool lives of 14.75 min and 10.08 min were obtained at a low cutting speed and feed rate for CVD and PVD tools, respectively. However, the lowest surface roughness of 0.276 µm and 0.307 µm was achieved at a high cutting speed and low feed rate for PVD and CVD tools, respectively. The evolution of tool wear, studied through the microscopic images of the worn tools, revealed that a high cutting speed and feed rate accelerated the flank wear for both types of tools. Nevertheless, the CVD tool exhibited better results due to the thick and effective Al2O3/TiCN coating layer, which protected the carbide substrate against thermal–mechanical loads. Moreover, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) performed on the worn tools revealed that adhesion, oxidation, diffusion, and abrasion were the main wear mechanisms for both types of tools. [ABSTRACT FROM AUTHOR]

This study investigates the intricate relationship between surface roughness (Ra) and the extent of chip segmentation (Gs) during the milling process of A7075 aluminum alloy across a wide range of cutting speeds. The experimental setup involves variations in feed rate (F) from 0.1 to 0.3 (mm/rev), depth of cut (t) from 0.9 to 1.6 mm, and normal cutting speed (V) ranging from 200 to 500 m/min. By rigorously analyzing experimental data, a robust model is developed, elucidating the complex interdependence of cutting parameters (V, F, t) on surface roughness and chip segmentation. Particularly noteworthy is the significance of this relationship in high-speed machining, specifically ranging from 900 to 1200 m/min. Our clarified findings confirm that feed rate (F) and depth of cut (t) have negligible effects on both surface roughness (Ra) and chip segmentation degree (Gs), while cutting speed (V) significantly influences surface roughness (Ra) and the degree of chip segmentation (Gs) in high-speed machining. This influence becomes particularly prominent at higher speeds, as indicated by ANOVA analysis. Cutting speeds ranging from 900 to 1600 m/min exert an 84.9% influence on chip segmentation degree (Gs) and an 85.4% influence on surface roughness (Ra). The derived mathematical model is rigorously validated under standard and high-speed machining conditions, demonstrating a maximum deviation of 8.58% for Ra and 8.4% for Gs at V = 450 m/min. Notably, this deviation reduces to 4.03% for Ra and 1.92% for Gs at a cutting speed of V = 1200 m/min. To enhance the model's applicability, a comprehensive dataset spanning cutting speeds of 250 to 2000 m/min was utilized. The resulting mathematical relationship between Ra and Gs was rigorously validated against experimental data, revealing evenly distributed bias data with a mean deviation of 3.11% for Gs and 3.54% for Ra. [ABSTRACT FROM AUTHOR]

The aim of this paper is to establish a valid procedure for better understanding all of the phenomena associated with the high-speed machining of glass fiber-reinforced plastic (GFRP) composites. Both rectangular and circular specimens were machined at high cutting speeds (up to 50 m/min) in order to understand what occurred for all values of fiber orientation angles during machining operations. An innovative testing methodology was proposed and studied to investigate the phenomenon of burr formation and thus understand how to avoid it during machining operations. To this end, the forces arising during the machining process and the roughness of the resulting surface were carefully studied and correlated with the cutting angle. Additionally, the cutting surface and chip morphology formed during cutting tests were examined using a high-speed camera. Close correlations were found between the variations in the cutting forces' signals and the trends of the surface roughness and the morphology of the machined surface. [ABSTRACT FROM AUTHOR]

Ti-6Al-4V, a titanium alloy, is widely employed in various engineering sectors due to its attractive combination of strong corrosion resistance and specific strength. However, titanium alloys frequently result in serrated chips, which present considerable machinability issues compared to other materials. The cutting medium plays a vital role in the chip formation mechanism, further affecting the machined part integrity and thermo-mechanical properties. Chip morphological parameters such as shear angle, compression ratio, and segmentation degree are essential aspects of estimating machined part surface roughness, tool wear, cutting forces, and energy consumption. Therefore, it is important to understand the entire mechanism of chip formation in terms of chip morphology in high-speed cutting. This fundamental research aims to analyze and compare the shear angle model and chip formation of titanium alloy Ti-6Al-4V for cutting speeds ranging from 50 m/min to 150 m/min and feed rates ranging from 0.12 mm/rev to 0.24 mm/rev under dry and cryogenic cutting environments. Single-point turning experiments were conducted on Ti-6Al-4V workpieces with uncoated tungsten carbide inserts (without chip breakers), which are advantageous for heat transfer. After the chip analysis, it was observed that the shear angle obtained practically with model-4 is the most appropriate model for shear angle calculation, and the cryogenic cutting medium is suitable for Ti-6Al-4V machining. At the feed rate of 0.12-0.24 mm/rev and cutting speed of 50-150 m/min, the shear angle in dry-medium machining ranges from 32° to 42°, while in cryogenic medium machining, it ranges from 34.6° to 44.6°. Overall, a larger shear angle has been observed in cryogenic turning compared to dry turning, which is advantageous for reduced cutting forces owing to a lesser shear plane. The tool-chip contact length, which is the intimate contact between the tool face and chip surface, significantly decreases under cryogenic media. A smaller tool-chip contact length results in an elevated shear angle, which improves process sustainability and economy during cryogenic turning, as described. [ABSTRACT FROM AUTHOR]

Machining of Incoloy 800 is challenging, which can be attributed to the low thermal conductivity, hot strength, accord for insert material and propensity to work harder. This study evaluates the influence of carbide tool-insert wear (rake, flank) and surface roughness (Ra) under process variables (cutting speed, feed rate and depth of cut) in high-speed dry turning of Incoloy 800. The essence of chip formation in Incoloy 800 in the context of coolant-less turning operation was also investigated. The turning experiments were performed in relation to Taguchi’s experimental design, with three factors with three levels: cutting speed (175, 200 and 225 m/min), feed rate (0.15, 0.2 and 0.25 mm/rev) and depth of cut (0.6, 0.8 and 1 mm). The experimental observations confirm that abrasion, adhesion and diffusion are the prime tool wear mechanisms responsible for tool failure. The formation of built-up edge (BUE) during the turning process was predominant, and excess BUE was observed at higher cutting parameters. The crater formation was found to be more severe at higher cutting conditions. The cutting speed has a firm hold on tool wear and surface roughness. The variation of surface roughness showed almost a cyclic trend and was found to decrease with an increase in the nose radius.

This paper investigates the impact of high-speed machining with heat-assisted machining (HAM) on the machinability of heat-treated SKD61 steel, utilizing alloy cutting tools. The study encompasses microstructure analysis, mechanical properties evaluation, chip color examination, surface roughness assessment and cutting force measurement during the machining process. Experiments are conducted under controlled conditions with advanced equipment. Findings indicate that at 200°C and 350°C, SKD61 steel's microstructure remains unchanged, while at 500°C, there's a superficial alteration of approximately 0.05 mm thickness. Material hardness remains consistent across temperatures. Unique chip color variations serve as temperature indicators. Cutting force consistently decreases with rising temperature, highlighting the intricate relationship between temperature, material behavior and cutting mechanics. Surface roughness improves with higher temperatures, emphasizing the potential benefits of HAM in precision manufacturing. [ABSTRACT FROM AUTHOR]

High speed machining (HSM) is an attractive process for numerous applications due to its potential to increase production rates, reduce lead times, lower costs, and enhance part quality. In this study, high-speed turning operations on AISI D2 steel using a coated carbide cutting tool under dry conditions were conducted. The cutting parameters examined in this investigation were Vc, f , and ap, while the outputs measured were surface roughness (Ra), cutting temperature (T), and flank wear (VB). To obtain reliable and accurate results, a Taguchi L27 orthogonal array for the 27 experimental runs was employed as well as analysis of variance (ANOVA), response surface methodology (RSM), and artificial neural network (ANN) to develop a constitutive relationship between prediction responses and the cutting parameters. The ANOVA results showed that Vc had a significant effect on T (36.81%) and VB (27.58%), while f had a considerable influence on Ra (24.21%). Additionally, nonlinear prediction models were created for each measured output and their accuracy was evaluated using three statistical indices: coefficient of determination (R 2), mean absolute percentage error (MAPE), and root mean square error (RMSE). Finally, multi-objective optimization was successfully carried out using the desirability function (DF) approach to propose an optimal set of cutting parameters that simultaneously minimized Ra, T , and VB. The optimized cutting parameters were Vc = 477.28 m/min, f = 0.08 rev/min, and ap = 0.8 mm, resulting in Ra = 1.23 μ m, T = 1 2 9. 9 ∘ C, and VB = 0.049 mm. [ABSTRACT FROM AUTHOR]

Ti2AlNb intermetallic alloy is currently the most promising lightweight high-temperature resistant material in the aerospace industry, owing to its high specific strength, favourable room temperature plasticity, outstanding temperature strength, and creep resistance. High speed cutting technology is characterized by low cutting force, minimal thermal deformation, high material machining efficiency and precision, which is widely used in machining TiAl intermetallic alloys and associated key components to ensure superior machined surface quality and dimensional accuracy. However, there are serious tool wear during high speed cutting of Ti2AlNb intermetallic alloys because of its high specific strength and temperature strength, and the tool wear mechanism is unknown. In this paper, the high-speed face milling trials of Ti2AlNb intermetallic alloys are performed to investigate tool wear evolutions and wear mechanisms. More specifically, tool wear morphologies, tool tip breakage, machined surface roughness, and cutting forces are investigated in detail. Results indicate that high-speed face milling results in severe tool wears, leading to a rapid increase in cutting forces and machined surface roughness during the severe wear stages. The tool's service life is limited to 228 s due to tool tip breakage resulted from coating delamination, cracking, and mechanical impact. Tool wear morphologies encompass tool rake face and flank face wear, exhibiting typical characteristics of coating delamination and microchipping. Adhesive wear and oxidation wear are the primary mechanisms of tool wear, occurring on both the rake face and flank face. The experimental results can provide a reference for high speed machining of TiAl material and promote the application of the material. [ABSTRACT FROM AUTHOR]

In high-speed machining (HSM), process performance is closely linked to the optimization of cutting conditions and spindle exploitation. Keeping high levels of productivity and machine availability with limited costs is important. However, machining incidents, such as abnormal vibration or tool failure, can cause spindle failure and machine downtime. Consequently, identifying which kind and which severity of machining incident can damage an HSM spindle is critical (as well as which evolution of spindle vibration signature reveals a damage). For that purpose, in-process monitoring data and spindle condition monitoring data are analyzed by knowledge discovery in database (KDD), with a dedicated method to the machining process. Since daily spindle vibration signatures are measured, the in-process monitoring data needs to be daily aggregated. An original unsupervised co-training by genetic algorithm is then proposed for the diagnosis of an HSM spindle, in order to determine which machining events are critical for the spindle condition. Afterwards, preventive actions can be taken. The approach was applied to three spindle lifetimes, during which the monitoring data were collected for two years of machining of aeronautic structural components. Two major causes of spindle failure were then identified. [ABSTRACT FROM AUTHOR]

Recently, the toolpath generation for high-speed machining of curved surfaces has become a non-trivial task. The approximated linear segments (G01-based) are widely used in commercial computer-aided manufacturing (CAM) systems. Due to the machine tool's acceleration/deceleration (Acc/Dec) control characteristics, there is a difference between the actual feed rate, the toolpath, and the commanded values when machining with CNC machine tools. This leads to the toolpath trajectory error. In addition, the cutting force applied to the cutting tool causes tool deflection. These factors cause errors between the designed and machined surfaces. In order to, therefore, predict the machined surface shape of a workpiece, it is necessary to predict the actual toolpath trajectory. The main objective of this study is to predict the actual toolpath trajectory by modeling the speed change. Furthermore, several toolpath generation methods in the postprocessing level are proposed to reduce the error between the actual toolpath and the commanded toolpath. The effectiveness and reliability of the methods are verified by experimental results. [ABSTRACT FROM AUTHOR]

The aim of this paper was to develop and verify a method for evaluating the high-performance milling of Inconel 718 alloy under accelerated tool wear conditions. The method considered parameters such as cutting-force components, total machine power consumption, cutting-edge wear, and material removal rate. The study compared high-feed milling and plunge milling, using sets of cutting parameters that are appropriate for both techniques. The results indicate that high-feed milling was more efficient, achieving higher material removal rates and lower tool wear. On the other hand, plunge milling was characterized by a lower axial force component (Fz), which can positively affect machining accuracy. The paper highlights that the proposed evaluation method can also be applied to other hard-to-machine materials, and plunge milling offers a competitive alternative for roughing operations in the milling of Inconel 718 alloy.

The severe plastic deformation process induces dynamic recrystallization in the machined surface and the adiabatic shear band during high-speed machining. It is a desirable approach to directly improve the machined surface integrity by the ultra-fine grains generated from the finish machining. The grain size modification mechanism depends on the incorporated effects of high strain, strain rate, and temperature in machining. The Zener-Hollomon (Z-H) model has been a popular approach to predicting the dynamic recrystallization behavior in grains in processing. The model combines strain rate and temperature into a single parameter, Z, to achieve simplicity in prediction. However, it cannot achieve reliable prediction in high-speed machining involving large strain, high strain rate, and high temperature. Hence, based on the original Z-H model, a modified dynamic recrystallization model is proposed particularly for high-speed machining. In the modified model, the competitive roles of strain rate and temperature are emphasized since extremely high strain rate induced dynamic recrystallization and high temperature promoted dynamic recovery. Additionally, large plastic strain, neglected in the original Z-H model, is treated as a control variable to capture the behavior of grain dynamic recrystallization. Furthermore, an incremental formulation based on the modified dynamic recrystallization model is proposed to accurately explore the evolution of grain size to overcome the unpredictable abrupt changes in grain sizes generated from the original Z-H model. The results demonstrate the effective enhancement of predicted accuracy in terms of the evolution behavior of dynamic recrystallization in high-speed machining of titanium alloy. [ABSTRACT FROM AUTHOR]

The chip transition from continuously serrated to discontinuously segmented is one of the most fundamental and challenging problems in metal cutting. In this work, a reliable finite element model for high speed cutting of Ti-6Al-4 V was developed based on the high speed cutting experiments. The Johnson–Cook (J-C) constitutive parameters of the Ti-6Al-4 V were optimized using the response surface method (RSM) and multi-objective genetic algorithm to accurately describe the plastic behavior of Ti-6Al-4 V alloy in high speed cutting. With using the optimized constitutive parameters, the simulated chip morphologies and cutting forces match well with the experimental results in a wide range of cutting speed from 0.05 to 86.5 m/s. The formation mechanism of the discontinuously segmented chip was further studied based on the validated finite element model. The results reveal that three distinct cracks form successively in the segmented chip formation process: crack I forms at the chip root, cracks II and III initiate at the primary shear zone center and chip-free surface respectively and propagate along the direction of maximum stress triaxiality to separate the chip and workpiece. Crack I, which forms at the chip root due to the maturely evolved shear banding, is the key reason for the transition of chip formation from continuously serrated to discontinuously segmented. [ABSTRACT FROM AUTHOR]

This study conducts comprehensive mesh independence tests to identify the optimum mesh independence parameters that offer the most feasible Computational Fluid Dynamic (CFD) analysis on cryo-CO2 temperature variations and its heat transfer performance under cryo-CO2 cooling strategy in metal cutting. ANSYS Fluent was used to conduct the CFD study with its mesh control parameters (relevance center and smoothing) designed using Response Surface Methodology (RSM) under Central Composite Design (CCD). An Analysis of Variance (ANOVA) was applied to analyse how the controlled factors influenced the cryo-CO2 flow temperature when it flowed from the nozzle to the tooltip. The analysis found that the relevance centre was more significant in influencing the accuracy of the response value. For optimization, the combination of medium relevance center and smoothing meshes was suggested to develop the lowest cryo-CO2 flow temperature at 256.85 K. This is crucial since most machining outputs are heat dependent. Experimental data sets were used to validate the predicted result. Distances between 3.6 to 18 mm showed an acceptable deviation of ~0.4 - 0.6% and ~0.4 - 4.2% for simulated and experimented work, respectively. This value is acceptable, and the generated quadratic model equation can be applied for prediction. The heat transfer performance of the cryo-CO2 flow at tool-chip and tool-workpiece interfaces under high-speed machining was also discussed. Moreover, further analysis using the optimal solution has led to a better understanding of heat transfer in cryogenic carbon dioxide (CO2), resulting in enhanced cooling of the cutting zone and improved machining processes. [ABSTRACT FROM AUTHOR]

Machining of Incoloy 800 is challenging, which can be attributed to the low thermal conductivity, hot strength, accord for insert material and propensity to work harder. This study evaluates the influence of carbide tool-insert wear (rake, flank) and surface roughness (Ra) under process variables (cutting speed, feed rate and depth of cut) in high-speed dry turning of Incoloy 800. The essence of chip formation in Incoloy 800 in the context of coolant-less turning operation was also investigated. The turning experiments were performed in relation to Taguchi's experimental design, with three factors with three levels: cutting speed (175, 200 and 225m/min), feed rate (0.15, 0.2 and 0.25 mm/rev) and depth of cut (0.6, 0.8 and 1 mm). The experimental observations confirm that abrasion, adhesion and diffusion are the prime tool wear mechanisms responsible for tool failure. The formation of built-up edge (BUE) during the turning process was predominant, and excess BUE was observed at higher cutting parameters. The crater formation was found to be more severe at higher cutting conditions. The cutting speed has a firm hold on tool wear and surface roughness. The variation of surface roughness showed almost a cyclic trend and was found to decrease with an increase in the nose radius. [ABSTRACT FROM AUTHOR]

Titanium and nickel alloys are used in the creation of components exposed to harsh and variable operating conditions. Such components include thin-walled structures with a variety of shapes created using milling. The driving factors behind the use of thin-walled components include the desire to reduce the weight of the structures and reduce the costs, which can sometimes be achieved by reducing the machining time. This situation necessitates, among other things, the use of new machining methods and/or better machining parameters. The available tools, geometrically designed for different strategies, allow working with similar and improved cutting parameters (increased cutting speeds or higher feed rates) without jeopardizing the necessary quality of finished products. This approach causes undesirable phenomena, such as the appearance of vibrations during machining, which adversely affect the surface quality including the surface roughness. A search is underway for cutting parameters that will minimize the vibration while meeting the quality requirements. Therefore, researching and evaluating the impact of cutting conditions are justified and common in scientific studies. In our work, we have focused on the quality characteristics of horizontal thin-walled structures from Ti6Al4V titanium alloys obtained in the milling process. Our experiments were conducted under controlled cutting conditions at a constant value of the material removal rate (2.03 cm3⁄min), while an increased value of the cut layer was used and tested for use in finishing machining. We used three different cutting tools, namely, one for general purpose machining, one for high-performance machining, and one for high-speed machining. Two strategies were adopted: adaptive face milling and adaptive cylindrical milling. The output quantities included the results of acceleration vibration amplitudes, and selected surface topography parameters of waviness (Wa and Wz) and roughness (Ra and Rz). The lowest values of the pertinent quantities were found for a sample machined with a high-performance tool using adaptive face milling. Surfaces typical of chatter vibrations were seen for all samples. [ABSTRACT FROM AUTHOR]

Cutting temperature is a crucial factor in high-speed machining processes. In 1931, Dr. Carl Salomon proposed the fascinating hypothesis that the cutting temperature increases with the cutting speed to a critical point and then decreases as the cutting speed continues to climb, which provides a successive impetus for developing high-speed machining technology. Despite extensive studies over the past several decades, Salomon's hypothesis has not been fully verified. In this study, a unique measuring technique was developed, which combines a light gas gun-based ultra-high-speed cutting setup with an infrared detector-based high-speed transient temperature measuring system. Using this technique, the cutting temperatures for the most typically difficult-to-cut and widely used Ti-6Al-4V alloy are measured over a broad spectrum of cutting speeds ranging from 7.5 to 212.6 m/s. The experimental results show that the measured temperature at the tool tip first increases with increasing cutting speed to a critical point of 125.2 m/s and then decreases as the speed continues to increase, providing solid evidence for the Salomon's hypothesis. We further reveal that the tool temperature decreases at ultra-high cutting speeds stems mainly from less heat generation in the primary shear zone and more heat convection by high-speed chip flow. [ABSTRACT FROM AUTHOR]

Al 2 O 3 /SiC w ceramic end mill was prepared via spark plasma sintering (SPS). The grain growth kinetics, densification mechanism and effect of SiC w on Al 2 O 3 ceramics were studied. Cutting performance of the Al 2 O 3 /SiC w ceramic end mill was evaluated by high-speed machining Inconel 718. The results showed that the densification mechanism of Al 2 O 3 ceramics was dominated by grain boundary diffusion when the sintering temperature was lower than 1500 °C. The Al 2 O 3 /SiC w ceramic end mill with a 25 wt% SiC w content, prepared at 1400 °C and the holding time of 5 min, possessed the most optimal mechanical properties. The relative density, Vickers hardness and fracture toughness were 99 ± 0.1%, 21.9 ± 0.8 GPa and 6.9 ± 0.4 MPa m1/2, respectively. The ceramic end mill exhibited satisfactory performance in cutting with Inconel 718 workpieces, and the tool failure was mainly caused by wear. [ABSTRACT FROM AUTHOR]

The α/β-SiAlON ceramic was joined to WC-8Co cemented carbide with Ti-Cu by spark plasma sintering. Interfacial microstructure and phases of the joints were studied. The effects of joining temperature, holding time, and pressure on the shear strength of the α/β-SiAlON/WC-8Co joints were investigated. The typical interfacial microstructure of α/β-SiAlON/Ti-Cu/WC-8Co joint was α/β-SiAlON/TiN + Ti 5 Si 3 + TiCu + TiCu 2 + Cu + Cu-Co solid solution/WC-8Co. In comparison with pressure, temperature and holding time had greater impacts on the degree of interfacial reaction during the joining process. When the joining temperature, holding time, and pressure were 900 °C, 5 min and 40 MPa, the highest shear strength (246.3 MPa) of α/β-SiAlON/WC-8Co joint was achieved, which is qualified for the high-speed machining of superalloy. [ABSTRACT FROM AUTHOR]

Wear resistance is a critical property of tool coatings for high-speed machining, which depends on mechanical properties and oxidation resistance of the coatings. Many works have demonstrated that AlTiSiN coating has good mechanical properties. Additionally, AlCrN coating exhibits excellent oxidation resistance. The multilayered structure has proved to improve comprehensive properties of the coatings. Therefore, AlCrN/AlTiSiN multilayer coating has a high potential to be used in machining applications. This paper focuses on the high-temperature tribological behavior of AlCrN/AlTiSiN multilayer coating. The results show that AlCrN/AlTiSiN coating exhibits good to acceptable wear resistance up to 800 °C. Meanwhile, AlCrN/AlTiSiN coating also displays the lowest friction coefficient of ∼0.5 and a wear rate of 1.8 × 10−6 mm3/N m at 800 °C, which is about 58.13% and 64.0% lower than that of AlCrN and AlTiSiN coatings, respectively. The imaging and composition analysis of the high-temperature wear tracks allowed for explaining the differences in wear mechanisms. At 800 °C, a dense thin tribofilm is formed on the surface of AlCrN/AlTiSiN coating, which acts as a glaze layer to impede wear. It provides a strategy for enhancing the wear resistance of monolayer coating in high temperatures, which combines the advantages of both high oxidation resistance of one layer and high hardness of the other layer. [ABSTRACT FROM AUTHOR]

In the die-molding industry, milling steels in a hardened condition is common. Tool wear and cutting-forces occurring during this process must be considered for better surface quality. The cutting performance of nano-layered AlTiN/TiN coated carbide cutting-tools in AISI D2 face-milling was evaluated in this work. Single-layer hard-coated carbide cutting-tools and uncoated cutting-tools were used to compare cutting performance testing. All cutting-speeds nano-layer AlTiN/TiN coated carbide cutting tool presented longer cutting-length than TiAlN and TiN coated ones and uncoated tool. Notch wear is an overriding wear mechanism, followed by build-up edge formation for all cutting-tools. Using a nano-layer AlTiN / TiN hard-coating, cutting-force values were lowered in all experiments.

This review paper critically emphasizes the possibilities and recent developments for producing high-performance conventional cutting tools that are in demand in the traditional machining industry. These cutting tools are considered for use in traditional machining of materials that provide a high strength-to-weight ratio for various applications with high precision. This review focuses on the machinability of turning, milling, drilling, and other special tools manufactured using various additive manufacturing methods. The materials and methods used are also studied, enabling us to understand the vast requirements of tool materials and the additive manufacturing methods available for production. The critical suggestions discussed would establish a platform for the selection of printing methods and printing strategies to develop cutting tools with complex internal geometries.

In this research, sustainable machining of the aluminum alloy (Al 6061-T6) is considered. Aluminum is a durable and infinitely recyclable material as well as light in density, causing no environmental effects in comparison with other materials including steel or plastic. Currently, due to a lack of understanding and inefficient application of modern sustainable manufacturing tools and technologies, around 20% of the investment made in metal cutting tools was reported to have been wasted. The constitutive law describing the thermo-mechanical behavior of workpiece material significantly affects the success of any finite element modeling (FEM). Different values of Johnson–Cook (JC) material constants determined through different methods are found in the literature which consequently affects the predicted results. Current research used an inverse methodology to determine the JC material constants and compare them with published literature. The proposed JC material model was then verified through orthogonal machining of Al 6061-T6 alloy at different machining conditions. Cutting forces at high-speed machining were found to decrease remarkably due to adiabatic heating conditions and short contact time between the workpiece and tool material. The JC material constants determined through the current approach produced better predictions of the cutting forces at high-speed machining conditions suitable for sustainable manufacturing. [ABSTRACT FROM AUTHOR]

Since difficult-to-machine materials are widely used in high-end equipment such as aerospace and marine components as well as precision molds, the development of high-performance cubic boron nitride (cBN) tools has been an important area of research. In this paper, we evaluate a new type of finer-grained, binderless end mill (binderless nano-polycrystalline cBN, BNNC) by comparing it to polycrystalline cBN (PcBN) end mills for high-speed machining of hardened steel. First, the process of tool preparation based on the above novel cBN is described and high-speed milling experiments were designed. Then, the cutting performance of the BNNC and PcBN tools during high-speed milling is analyzed and compared in four aspects: the cutting force coefficients, the friction coefficient of the rake face, the milling temperature and the tool wear. In addition, the wear mechanism of the two types of end mills was analyzed by energy dispersive X-ray (EDX). Afterwards, the trend of cutting temperature was further investigated by 2D finite element simulation. Finally, grey correlation analysis was applied to describe the correlation between the above factors and tool wear. This study shows that compared with PcBN end mills, BNNC end mills have longer tool life under the same cutting condition and are more reliable at high temperatures, which exhibit great application potential. [ABSTRACT FROM AUTHOR]

High-speed ultrasonic vibration cutting shown great advantages by cutting temperature reduction due to periodic opened cutting interfaces for direct heat convection with coolants. To figure out accurate heat transfer ability, a 2-dimensional simplified model was developed and computational fluid dynamics (CFD) was used to calculate heat flux and Nusselt number. Three flank wear lengths for initial, initial-stable transition and stable stages were chosen and comparisons made between CFD results and wear progresses indicated that heat transfer ability demonstrated better performance during the stable wear stage at low cutting speed. As cutting speed increased the effect of ultrasonic vibration was weakened. [ABSTRACT FROM AUTHOR]

Ceramic tool materials possess a wide range of potential in machining nickel‐based superalloys due to their superior wear resistance, high‐temperature hardness, and strong chemical stability. Herein, a structural optimization scheme of self‐developed silicon nitride ceramic end mill based on stiffness enhancement and performance improvement is proposed, and the key geometric angular parameters scope of the self‐developed ceramic end mills are prioritized via the finite‐element simulation method. Through precision grinding manufacturing and sandblasting pretreatment, the cutting performance and tool wear behavior of three optimized self‐developed silicon nitride ceramic end mills (called S4‐1, S4‐2, S4‐3 respectively) are comprehensively analyzed in comparison, including cutting force, milling temperature, surface quality, and tool life. The results indicate that the cutting force and cutting temperature of all the optimized ceramic end mills are effectively restrained compared with the nonoptimized ceramic tool(S4), and the final workpiece surface roughness is significantly reduced. Further, better surface quality can be obtained by optimized ceramic mills. In terms of tool life, ceramic end mill with optimized construction in best can be increased by up to 1.9 times. The wear mechanism and pattern of the three optimized ceramic milling tools are similar, which is adhesive wear, diffusion wear, and notch wear. Overall, the effectiveness of the optimization scheme for ceramic end mill is successfully verified. [ABSTRACT FROM AUTHOR]