Chip Morphology Research Articles

Toward understanding the drilling performance of thermoplastic CF/PEEK and thermoset CF/epoxy composites using special drills

Thermoplastic carbon fiber reinforced polyetheretherkrtone (CF/PEEK) and thermoset carbon fiber reinforced epoxy (CF/epoxy) composites are being widely applied in aviation and aerospace fields for their excellent performance. To compare the drilling characteristics of two typical carbon fiber reinforced composites under varying feed speeds, drilling experiments were carried out using three different special drills involving twist, brad, and dagger drills. The drilling performance of CF/epoxy and CF/PEEK composites was analyzed in terms of chip morphology, drilling temperature, thrust force, delamination damage, and surface morphology. The results show that CF/PEEK composites produced continuous chips, so that CF/PEEK composites generated higher drilling temperature and thrust force than that of CF/epoxy composites. CF/epoxy composites showed larger delamination damage and poorer machined surface than CF/PEEK composite due to its poor interlaminar toughness. Burrs produced agglomeration and crimping at the hole edges of the CF/PEEK composites due to PEEK resin is softened by heat, matrix plastic deformation. Brad drill revealed fewer burrs and merely a tearing damage at the exit. Dagger drill showed more burrs. The hole wall damage is minimal for brad drill. The results provide guidance for drilling of high quality thermoset and thermoplastic composites.

Understanding tool chip interaction through experimental and numerical analysis during vibration assisted turning of AISI D3 steel

Vibration Assisted Turning (VAT) is a hybrid machining process where the material is machined with the help of a tool vibrating at ultrasonic frequency. VAT results in significant changes in process characteristics compared to conventional machining, like reducing the machining forces and tool wear. The chips produced during the machining operation can provide valuable insight into the process characteristics like machining zone temperature, friction at the tool-chip interface and chip load that primarily alter the process performance. One can understand and have a better control on the machining process performance by studying the formation of these chips and the tool-chip interaction. The work presents an experimental and numerical study to analyze the chip formation during VAT while machining AISI D3 steel. The chips formed while machining at different vibration amplitudes were observed to be of different colors, widths, and thicknesses. These were found to correlate to the forces generated and the surface integrity produced. A decrease in the chip width and thickness was observed with an increase in the amplitude that helps to reduce the chip load and hence forces. Also, the temperature at the machining zone increased with an increase in amplitude as seen from different color of chips produced and carbon content of the chip. The numerical model, developed to analyze the effect of the vibration amplitude on the contact pressure at the chip-tool interface, showed that the average contact pressure reduced upon applying ultrasonic vibration to the tool, thereby reducing the coefficient of friction and frictional forces. Also, with increase in vibration amplitude, the coefficient of friction was found increasing but it still remained lower than that in conventional turning. The study would help to understand the reduction the overall machining forces and chip morphology and thereby to have a better control on the process performance.

Modeling and simulation of the negative angle cutting with a combined constitutive model for U71Mn rail steel

Due to the increasing train axle load, running speed and traffic volume, rails are prone to severe rolling contact fatigue (RCF) defects. Repairing the rail profile by milling is the latest technology to solve the above hidden problems, but there are few related studies in recent years. In this paper, the milling maintenance process of rails is studied by using finite element method(FEM). This study examines the fracture behavior of U71Mn steel rail under various stress triaxiality conditions, temperatures, and strain rates. An electronic universal testing machine is utilized to conduct the experiments, and a Johnson-Cook (J-C) failure model for U71Mn steel rail is developed. A 3D cutting simulation model was developed using the Johnson-Cook (J-C) combined constitutive model. The accuracy and reliability of the numerical simulation model were confirmed by comparing the cutting force and chip morphology obtained from both simulation and experimental results. The cutting simulation model had an error rate of within 10 % when predicting the cutting force. Following that, the fracture zone and chip portion of the tensile specimen were metallographically analyzed. The applicability of the ductile failure criterion in describing the observed failure in the U71Mn rail has been proven.

Influence of Technological Parameters on Chip Formation and Chip Control in Precision Hard Turning of Ti-6Al-4V.

This article presents the results of an experimental investigation into the effect of process parameters in the precision hard turning of Ti-6Al-4V on chip morphology at both macro and micro levels. It also reports on the control of chip generation to improve chip evacuation and breakability at the macro level by varying the process parameters, namely, feed rate, cutting speed and depth of cut during turning tests. A scanning electron microscope (SEM) was used to examine the chips produced for a better understanding of chip curling mechanisms at the micro level. Surface roughness of the machined specimens was measured to assess the effect of chip evacuation on obtainable surface quality. From the results, it was found that the interaction of process parameters has a significant effect on the control of chip formation. In particular, the interaction of higher cutting speeds and greater depths of cut produced chip entanglement with the workpiece for all values of feed rates. Using relatively higher feed rates with a low depth of cut showed good results for chip breaking when machining at higher cutting speeds. Different chip curling mechanisms were identified from the SEM results. Chip side-curl formation showed different segmentation patterns with an approximately uniform chip thickness along the chip width, while chip up-curl occurred due to variations in chip thickness. Finally, it was found that the tangling of the chip with the workpiece has a significant effect on the final surface quality.

On the formation of Ti2AlN MAX phase coatings and improvement in tool life by superimposing on tungsten carbide cutting tool for machining Ti-6Al-4V alloys

This paper presents the development of (002) textured Ti2AlN coated wear resistant tool utilizing reactive magnetron co - sputtering. The Ti2AlN coating was developed in two different Argon, Nitrogen ratios such as 64:3 and 64:4, the influence of these parameters was identified using crystallographic, microstructural, mechanical and tribological studies. Experimental studies were performed to compare the cutting force as well as the tool life of superimposed Ti2AlN tool with a commercial tool by turning titanium alloy (Ti-6Al-4V). Results from the experimental analysis revealed an 80–85 % increase in hardness, a 13–20 % decrease in wear rate and a 27 % increase in tool life for Ti2AlN coated cutting tool. According to chip morphology, there is a 12 % increase in shear angle, 43 % and 51 % decrease in friction angle and coefficient of friction respectively. The nanomechanical studies were performed which show a maximum hardness of 29.12 ± 5.4 GPa and minimum wear rate of 10.078 × 10−9 mm3/mN.m−1 for superimposed Ti2AlN.

Analysis of Tool Wear and Chip Morphology during Turning of AZ31B Magnesium Alloy under Dry Environment

The present research investigated the turning of AZ31B magnesium alloy in a dry environment using carbide tool inserts coated with tungsten carbonitride (TiCn) and thin alumina (Al2O3). A Box–Behnken design based on fifteen experiments showed a proportional increasing trend of flank wear with all three machining parameters, i.e., cutting speed, feed rate, and depth of cut. The most influential parameter is the cutting speed. A maximum flank wear of 299.34 µm due to excessive adhesion of work material on the tool face was observed at a high cutting speed. Machining at low speed resulted in a significant reduction in tool wear due to less chipping. The tool wear and chip morphology study confirmed the results.

Surfactant free enhancement to thermophysical and tribological performance of bio-degradable lubricant with nano-friction modifier for sustainable end milling of Incoloy 925

An efficient method of lubrication and cooling for green machining is nanofluid minimum quantity lubrication (NMQL). Compared to other vegetable-based oils, coconut oil has the highest viscosity index, lubricity, and oxidative characteristics, making it a popular trending lubricant for decreasing friction. However, its performance at higher temperatures degrades owing to higher saponification value. In order to improve its performance, the solid nano-friction modifier (hBN) is dispersed in it, and the colloid is called a nanofluid. UV–Vis–NIR spectrophotometer, HR-TEM, and FTIR spectroscopy characterize nanofluid. The stability of nanofluid at 0.3 vol% of hBN has been observed to be the highest compared to other volume fractions. Compared to coconut oil, prepared nanofluid is superior in terms of increased thermal conductivity, thermal stability, and viscosity for all the tested temperature ranges. Nanofluid shows increased viscosity index (VI) by 20%, reduced contact angle by 45%, and lower coefficient of friction (COF) by 32% compared to coconut oil. Further performance of this modified biodegradable nanofluid under Minimum quantity lubrication (MQL) on end milling of Incoloy 925 has been studied. In order to compare the machining performance under different cutting environments, cutting temperature, cutting force, specific cutting energy, power consumption, carbon emission, chip morphology, surface topology/topography, and tool wear were evaluated. Finally, sustainability assessments for different cutting environments have been performed. Biodegradable oil-based NMQL-assisted machining has performed better than dry and MQL-assisted machining.

The analysis of the effect of varying feed values in each pass on tool wear and surface roughness in turning of AISI 4140

Machining is a complex process between the cutting tool and the workpiece, and in this process, the cutting tool constantly wears out with various wear mechanisms. Tool-wear estimation in turning is a complicated process; thus, there is a need for a study to reveal the time-dependent behavior of tool wear. In this study, tool wear and surface roughness change during the turning process of AISI 4140 steel at low cutting speeds were examined in detail with variable feed values for the first time. For this purpose, a half-minute cutting time was applied for each pass to analyze the tool wear as gradually as possible. Tool wear (flank, notch, and nose), surface roughness (Ra, Rz, and Rt), and chip morphologies were examined after each turning operation. The flank wear reached 0.3 mm, which is one of the tool life criteria according to ISO 3685, and the experiments were terminated at the 149th minute. Initially, a significant surface improvement (approx. 300%) was observed due to the decrease in feed values. In subsequent experiments, the effect of feed was significantly reduced due to increased tool wear, and limited surface roughness improvement (approx. 30%) was observed. At the beginning of the experiment, the chip breaker function of the cutting insert was successful at almost all feeds. However, in subsequent experiments, it was found that even at higher feeds, the chip breaker geometry of the insert deteriorated due to tool wear, causing changes in chip morphology, and resulting in long and undesirable chips.

Cutting performance and failure mechanisms of TiB2-TiC-Al2O3 multi-dimensional gradient ceramic tool in intermittent turning of hardened steel

The TiB2-TiC-Al2O3 multi-dimensional gradient ceramic tool (MDGCT), whose composition varied in two directions, were designed and fabricated via hot-pressed vacuum sintering. The cutting performance, including cutting force, cutting temperature and chip morphology, and failure mechanisms of MDGCT with different orientation angles in intermittent turning of SKD11 hardened steel were investigated in comparison with the homogeneous commercial ceramic tool CC650 at different depths of cut and cutting speeds. And the distribution of thermal residual stress of MDGCT was investigated employing FEM analysis. Results showed that the multi-dimensional gradient ceramic tool with orientation angle of 15 degree (TT3A15) had the optimal comprehensive cutting performance. The main failure mechanisms of CC650 tool were chipping and fracture caused by crack propagation, while the crack propagation was effectively inhibited in the TT3A15 tool, and its failure mechanism was chipping at the tool nose. The contribution of multi-dimensional gradient structure of TT3A15 tool to the increasing residual compressive stress of minor cutting edge, the favorable anti-crack capacity of flank face and the heterogeneity of physical and mechanical properties of rake face were responsible for its optimal cutting performance.

Exploring the Impact of the Turning of AISI 4340 Steel on Tool Wear, Surface Roughness, Sound Intensity, and Power Consumption under Dry, MQL, and Nano-MQL Conditions

Optimizing input parameters not only improves production efficiency and processing quality but also plays a crucial role in the development of green manufacturing engineering practices. The aim of the present study is to conduct a comparative evaluation of the cutting performance and machinability process during the turning of AISI 4340 steel under different cooling conditions. The study analyzes cutting operations during turning using dry, minimum quantity lubrication, and nano- minimum quantity lubrication. As control parameters in the experiments, three different cooling types, cutting speeds (100, 150, 200 m/min), and feed rate (0.1, 0.15, 0.20 mm/rev) levels were applied. The experimental results show that the optimal output values are found to be Vb = 0.15 mm, Ra = 0.81µm, 88.1 dB for sound intensity and I = 4.18 A for current. Moreover, variance analysis was performed to determine the effects of input parameters on response values. Under dry, minimum quantity lubrication, and nano-minimum quantity lubrication processing conditions, parameters affecting tool wear, surface roughness, current by the motor shaft, and sound level were examined in detail, along with the chip morphology. The responses obtained were optimized according to the Taguchi S/N method. As a result of optimization, it was concluded that the optimum values for cutting conditions were nano-minimum quantity lubrication cooling and V = 100 m/min, f = 0.1 mm/rev cutting. Finally, it was observed that there was a 13% improvement in tool wear, 7% in current, 9% in surface roughness, and 8% in sound intensity compared to the standard conditions. In conclusion, it was determined that nano-minimum quantity lubrication with the lowest level of cutting and feed rate values provided the optimum results.

The mechanism of anisotropic micro-milling properties in additively manufactured Ti-6Al-4V alloy

Selective Laser Melting (SLM) technology offers great flexibility in manufacturing complex parts. However, secondary processing of selective laser melted (SLMed) parts is essential due to the poor surface morphology. This study investigated the influence of microstructural anisotropy in SLMed Ti-6Al-4V alloy on micro-milling performance. The orthogonal milling tests were conducted on the top, front, and side surfaces of specimens. Parameters including cutting force, chip morphology, burr morphology, surface quality, microhardness, and microstructure were evaluated to represent the anisotropy. The experimental findings demonstrated that the tool's orientation relative to the columnar grains influenced the slip strain modes and the density of grain boundaries in the shear band, thereby determining the correlation of the cutting force with the machined surface and feed direction. The variations in grain boundary density in different machining regions caused plastic anisotropy, which affects chip morphology, burr formation, and machined surface roughness. This research could provide valuable insights for manufacturers in selecting appropriate machining methods for precision processing.

Influence of nanoparticle concentration in nanofluid MQL on cutting forces, tool wear, chip morphology when milling of Inconel 718

Influence of nanoparticle concentration in nanofluid MQL on cutting forces, tool wear, chip morphology when milling of Inconel 718

Novel use of cryogenic cooling conditions in improving the machining performance of Al 8011/nano-SiC composites

The inclusion of nanoparticles makes the composite not only stronger but also lighter and highly resistant towards wear among many other positive attributes. However, the high hardness and abrasive characteristics of the composites make machining a formidable task. Hence to surmount these challenges, various coolant conditions have been entailed like dry machining, flood cooling, minimum quantity lubrication (MQL), and cryogenic (cryo) CO2 cooling. This investigation encompasses the influence of diverse coolant techniques during the machining of as casted aluminium with nano silicon carbide (Al/n-SiC) composite. This study further incites the analysis of the machining temperature, surface characteristics, flank wear, and chip morphology under each coolant techniques. The outcomes of this investigation furnish a comprehensive understanding of the impact of distinct coolant environments on the machining performance of Al/n-SiC composite. The cutting temperature under cryo-CO2 was found to be lowered by 41–47%, 15–21%, and 8–12% when compared to the usage of dry, flood, and MQL, respectively. The study unveils that cryo-CO2 cooling developed the lowest machining temperature, followed by MQL, flood cooling, and dry machining. Furthermore, cryo-CO2 cooling and MQL exhibited the best outcome in terms of flank wear and surface characteristics. The verdicts of this investigation suggest the use of cryo-CO2 cooling and MQL makes eloquent improvement in the machining performances of Al/n-SiC composites.

Influence of the microstructure of a Ti5553 titanium alloy on chip morphology and cutting forces during orthogonal cutting

Influence of the microstructure of a Ti5553 titanium alloy on chip morphology and cutting forces during orthogonal cutting

Machinability of Selective Laser Melted 17-4 PH Stainless Steel in Turning Process

This paper investigates the machinability of Selective Laser Melted 17-4 Precipitation Hardening Stainless Steel (17-4 PH SS). For this purpose, turning tests were carried out on wrought and SLM specimens and the results were compared. Wear tool, surface roughness, surface integrity and chip morphology were analyzed for both materials. For the tested cutting conditions, the machinability of the SLM material was inferior to that of the commercial material. Dissimilarities in machinability between both materials are a consequence of variations in their microstructures resulting from the manufacturing process.

Performance evaluation of developed new textured tools during turning of AISI 321 material

ABSTRACT Nowadays, productivity enhancement in machining operations in eco-friendly machining environment is a front-end requirement in the machining industries. In general, minimizing tool wear (Vb) and surface roughness (Ra) in machining processes can directly boost productivity. Therefore, the current effort attempts to improve productivity by regulating tool wear and surface roughness in an environmentally friendly machining environment. In this study, innovative textured tools (TT) were created, and the machinability performance of the produced tools was assessed under dry, conventional, and MQL conditions. According to the study’s findings, MQL cooling with TT considerably reduced the cutting temperature (T), Vb, and Ra to maximum values of 13%, 17%, and 29%, respectively, over untextured tools (UT). In addition, it was shown that MQL cooling considerably enhanced turning performance in both tools compared to without cooling and conventional cooling, respectively. Additionally, chip morphology research was done and showed promise using textured tools in MQL conditions as opposed to other machining settings.

Experimental study of plastic cutting in laser-assisted machining of SiC ceramics

In this paper, the cutting process of laser-assisted machining (LAM) of SiC ceramics is studied. Three processing states of brittleness, plasticity and thermal damage are determined based on the characterization analysis of surface integrity, tool wear and chip morphology, and the surface roughness and tool wear regression model established under the plastic processing state are verified. Firstly, the surface integrity, tool wear and chip morphology are investigated by the single-factor experiment of laser power to explain the material removal mechanism according to the material fracture theory and to determine the laser power range of plastic cutting (185 W–225 W). Then the Box-Benhnken experimental scheme is designed to establish a multivariate prediction model based on the response surface methodology (RSM) to obtain the regression equation of surface roughness and tool wear and further analyze the interaction between process parameters. Finally, the experimental values of surface roughness and tool wear are compared with the predicted values through optimization analysis. The results show that the maximum error is 5 % and 7.57 % respectively, which proves that the model has good prediction ability. The surface roughness and tool wear regression prediction models provide guidance for the selection of plastic cutting process parameters for SiC ceramics.

Machinability and tribological analysis of used cooking oil for MQL applications in drilling AISI 304 using a low-cost pneumatic operated MQL system

Developing low-cost MQL systems and application of used/waste cooking oil (generated in restaurants/homes), which poses a health risk if it enters the food chain again, as feedstock for MQL applications can increase the adoption of MQL by smaller manufacturing industries. A low-cost pneumatic-based MQL system that works only on compressed air is developed and tested. The droplet size and velocity of the MQL aerosol are analysed using CFD to arrive at an optimum nozzle design and the nozzle spray characteristics are studied using a Phase Doppler Particle Analyzer. Drilling of AISI 304 using the MQL system with commercial MQL oil and used cooking oil is carried out and the results are compared with flood cooling. The thrust and radial forces are comprehensively analysed and related to the tool wear, built-up edge (BUE) formation along the drill cutting edges, and chip morphology. It is found that a steady drilling process is obtained with used cooking oil because of its superior viscosity (resulting in lower friction) and lower surface tension (leading to smaller droplet size and better wettability).

Developing a novel ultrasonic atomization-based cutting fluid spray system and evaluating its performance during milling processes

Cutting fluid has been widespread in the metal cutting industry due to its cooling and lubrication properties. However, the excessive application of cutting fluids can lead to significant environmental issues and raise machining costs. Recently, the ultrasonic atomization-based cutting fluid (UACF) spray using minimum quantity has shown superior cooling and lubrication performance during machining processes, while the precise management of UACF spray and its influence on machining performance requires further comprehension. In this case, this paper developed a novel ultrasonic atomization-based cutting fluid (UACF) spray system, featuring a specialized nozzle unit that included an internal droplet nozzle and an external gas nozzle. Subsequently, the dynamics of droplet impingement on a rotated surface were analyzed, and the spray characteristic parameters were investigated. Then, comparative milling experiments were conducted under different cooling conditions, including dry cutting, flood cooling, high-pressure air cooling, and UACF. The influence of these cooling conditions on machining performance was investigated, in terms of cutting force, temperature, surface roughness, and chip morphology. The results obtained indicate that the critical velocity of droplet spreading was dependent on the cutting fluid properties, ultrasonic frequency, and velocity of the rotated surface. The droplets generated by ultrasonic atomization follow a Gaussian distribution. Flood cooling and UACF exhibit similar effects in reducing cutting force, temperature, and surface roughness due to the efficient penetration of liquid film into tool-workpiece interfaces. Additionally, UACF can significantly reduce the consumption of cutting fluid by up to 98.5 % compared to flood cooling. The effective cooling and lubrication in UACF can improve the surface quality and suppress machining vibration. Moreover, the appropriate droplet velocity can ensure the formation of a thin film on the tool surface, thereby enhancing cooling and lubrication performance in the UACF process.

A modified constitutive model considering dynamic recrystallization behavior for cutting Inconel 718

The microstructure evolution significantly affects the cutting process by modifying the workpiece material mechanical behavior. Dynamic recrystallization (DRX) in the cutting process of Inconel 718 induces significant microstructure evolution below the machined surface, leading to changes in output responses including cutting force, temperature distribution, residual stress and so on. In this work, a material constitutive model including the effect of DRX behavior on the flow stress for cutting Inconel 718 alloy is developed. The volume fraction of DRX is introduced as an internal state variable of Johnson-Cook (JC) constitutive model. The DRX kinetics model parameter is determined by using Oxley's parallel-sided shear zone theory for the orthogonal cutting. Orthogonal cutting experiments with high cutting speed and a series of finite element (FE) simulations by the modified model, JC model and TANT model are carried out. And the effectiveness of the modified model is verified by the comparison of the experimental and simulated data. The results show that the proposed material model not only has higher prediction accuracy on the cutting force compared with JC model and TANT model, but also can accurately predict the chip morphology. And the microstructure distribution in chip simulated by the modified material model is consistent with the experimental results. This model will be attractive to the FE simulation of the microstructure evolution for cutting Inconel 718 alloy.