Chip Formation Research Articles

Numerical and Experimental Investigation of the Thermomechanical Loads on the Machined Surface when Cutting Inconel DA718

In metal cutting processes, the thermomechanical loads lead to modifications of the residual stress state of the workpiece rim zone. Especially for aerospace components, such as turbine disks made of nickel-based alloys, this modification affects the functionality and dimensional accuracy of the machined part. Therefore, the thermomechanical loads occurring in the orthogonal cutting of Inconel DA718 are investigated in this paper and chip formation simulations are performed and evaluated with the experimental results. The outcome of this work forms the basis for a research project, where it is intended to develop a multiscale prediction model for residual stresses.

Chip Morphology Prediction in Inconel 718 Milling through Machine Learning to Control Surface Integrity

A nickel-based aerospace superalloy, Inconel 718 presents machining challenges because of its hardness and strength. Monitoring and predicting chip morphology during milling is essential for early defect detection and process optimisation. This study examines the correlation between sensor signals with surface roughness and chip morphology in milling Inconel 718 using machine learning (ML). Due to progressive tool wear and heat generation, the surface roughness varies in addition to the chip exhibiting different morphologies, such as continuous, discontinuous, and oxidised chips. AE signals were analysed in the time and frequency domains to identify chip morphology transitions. An accelerometer captured cutting vibration signals that showed higher instability during discontinuous chip formation. Chip colour due to oxidization varies with milling forces as a result of tool wear. Based on multiple sensor data fusion, a random forest model predicts better chip morphology from different machining parameters. The integrated ML system enables real-time monitoring of chip morphology mechanisms through diverse signals. This permits early diagnosis of surface integrity and chip morphologies indicating imminent tool wear. The approach enhances process stability and tool life when milling difficult-to-machine alloys. It demonstrates the viability of relating sensor signals to fundamental mechanisms through AI for intelligent machining.

РАЗРАБОТКА МАТЕМАТИЧЕСКОЙ МОДЕЛИ КОЛЕБАТЕЛЬНЫХ ПРОЦЕССОВ ПРИ ТОКАРНОЙ ОБРАБОТКЕ МАТЕРИАЛОВ С ОБРАТНЫМ РАСПРЕДЕЛЕНИЕМ ТВЕРДОСТИ

For technological guarantee of the required quality indicators of the surface layer of metallic rotation body parts at finishing machining needs the correct assignment of technological modes. During finishing turning, vibrational processes have a significant (and often decisive) effect on the formation of surface roughness. It is necessary to choose such values of technological modes, which provide an acceptable level of vibration (previously it is advisable to solve this problem by modelling). Mathematical model was carried out based on the determination of the turning tool deformations under the influence of cutting forces. To determine the amplitudes of the cutter oscillations, the Mohr integral was used, and the amplitude-frequency characteristics were determined using the Duhamel integral. Cutting forces were determined taking into account the shape and nature of chip formation, the value of technological modes and processing conditions. As the material to be machined, the authors considered the cast iron with a layer hardened by diffusion alloying. Determination of input data for model was carried out directly during machining on the lathe and with the help of measurements of chip parameters. As cutting tools, we used standard cutters with mechanically fastened plates. The evaluation of the modelling results showed high convergence with the experimental results: the error in amplitude was 8.5 percent, in oscillation frequency - 12.3 percent; in general, the error did not exceed 15 percent. Thus, the developed model can be used for preliminary vibration assessment at the design stage of turning operations.

Simultaneous high-speed cutting and high-feed milling: An investigation on surface integrity

In this article, the potential of high-speed machining with an inverse cutting ratio b/h < 1 (uncut width of chip b to uncut chip thickness h) is presented based on the evaluation of surface integrity. If the machining is realized with a low cutting ratio many process quantities and chip formation mechanisms are fundamentally changed. As a result, the cutting process is stabilized through reduced feed forces and improved chip removal conditions. For the investigations, face-milling trials were carried out on an aluminum alloy (EN AC-42100) under conventional and high cutting speeds with variation of the feed per tooth and the use of cemented carbide and polycrystalline diamond tools. It is shown that when both machining strategies are combined, there is no further reduction in force components or improvement in surface topography. When the feed per tooth is increased at high cutting speeds, there is a linear increase in force components but surface roughness remain almost unchanged. After an initial increase in surface residual stresses, increasing the cutting speed leads mainly to compressive surface residual stresses. Overall, the surface integrity is influenced by the choice of cutting material and the micro-geometry of the cutting edge radius.

Finite element simulation of the mechanical loads during low frequency vibration-assisted drilling utilizing the CEL-method

Poor chip evacuation during drilling leads to increased heat generation in the contact zone and a decreased in borehole quality. This disadvantage can be overcome by low frequency vibration assisted drilling (LFVAD), which produces small, uniform shaped chips that allow better chip evacuation. The study presents the results of simulations of chip formation in conventional drilling (CD) and LFVAD based on the Coupled Eulerian-Lagrangian (CEL) method. The method does not require time consuming remeshing despite the high strains and strain rates that occur. In this work, a mesh refinement analysis in different spatial directions is performed in order to reduce the computational effort and preserve the accuracy of the numerical results.. A comparison with experimental data is performed for validation.

Force coefficient characterization in machining of UD-CFRP using numerical-analytical approach

A numerical-analytical approach was utilized to construct a predictive model of cutting force for machining unidirectional carbon fiber reinforced polymer (UD-CFRP) laminates. The force coefficients in the model, which include friction angle, shear plane angle, shear strength, and rebound height, can be characterized by the fiber orientations ranging from 0° to 180°. The accuracy of the model was confirmed through experimental verification. The results indicate good agreement between the predicted and experimental values, with relative errors below 14.8%, except for the thrust force at 90°. Additionally, the study examined the influence of rake angle and flank angle on the cutting force, revealing two critical points in the predicted cutting force curve throughout the fiber orientation. These turning points shifted with changes in the rake angle. For instance, the value of the first critical point changes from 60° to 45° when the rake angle range shifts from [0°, 5°] to [10°, 15°]. This indicates that a larger rake angle facilitated an earlier transformation of chip formation mode, leading to a decrease in cutting force. Furthermore, the cutting force decreased as the rake angle increased between the two turning points. The impact of the flank angle on the cutting force was determined to be minimal, and the turning points’ positions remained consistent as the flank angle increased.

Eksperimentalna procena biomaziva sa dodatkom nanočestica kalcijum karbonata (CaCO₃) iz otpada ljuske kapice kao tečnosti za sečenje korišćenjem minimalne količine podmazivanja (MKL) u CNC procesu glodanja

Nano-cutting fluid sprayed using the minimum quantity lubricant (MQL) method is one example of a green manufacturing process. Meanwhile, vegetable oil is an appropriate lubricating base oil as it offers very high lubricating performance and environmental friendliness. Further, CaCO₃ nanoparticles are popular for their capacity to improve lubrication properties and performance. However, the optimum impact of utilizing different types of vegetable oil remains inadequately investigated. Therefore, this study aims to analyze the effect of CaCO₃ nanoparticles on the performance of cutting fluid, specifically on the thermophysical, rheological, and tribological properties in the CNC milling process of AISI 1045 Steel material. The nano-cutting fluid was prepared using different vegetable oils (canola, corn, soybean) added with CaCO₃ nanoparticles with a mass concentration of 0.15%. The results showed that the thermophysical properties, including density and viscosity, were highest when using canola oil, and the addition of CaCO₃ to all samples did not significantly affect thermal conductivity. Meanwhile, for the rheological properties, we observed Newtonian for all cutting fluid samples. For tribological properties, canola, and corn oil were better for obtaining a minimum Ra value, while soyabean oil was more effective in reducing cutting temperature. Based on the results of tool wear calculations, each oil presents the best performance in reducing wear, especially with the addition of CaCO₃. For chip formation, on average, the samples produce irregular tooth morphology with C-type, comma, and elongation shapes. Meanwhile, the resulting chip color was dark purple, which changed to dark brown and light brown, then turned silvery white due to wear and tear on the different sides of the chisel.

Effects of cutting conditions on the cutting forces in machining additively manufactured Ti6Al4V alloy

Machining of additive manufacturing (AM) process results in excessive consumption of the cutting power due to the high strength and hardness of the material produced that led to high cutting forces and short tool life during machining process. This paper aims to investigate the effect of cutting conditions and coefficient of friction on the cutting forces, during finite element analysis (FEA) of an orthogonal cutting of AM Ti6Al4V alloy bar. The FEA simulation considers three different experiments at low, medium, and high cutting conditions. The result shows that as the depth of cuts gets deeper and the cutting speed increases, the cutting forces were found to increase, leading to serrated or segmented chips formation. A cutting force of 1300.36N was observed at a cutting speed of 150 m/min and a coefficient of friction of 0.9. The cutting force was found to be weaker at the higher shear plane angle of 42.2o and higher at a smaller angle of 37.57o. The coefficient of friction was observed to be insignificant at lower value of 0.09 and was seemed to affect the cutting force at value around 1.

Performance of Liquid Nitrogen (LN2) on Machining Pure Titanium (Grade 2): A Comparative Study

The biggest challenge for manufacturing industries is machining super alloys due to their properties. Titanium grade 2 also comes under the category of difficult cut material. In this present investigation, the green manufacturing technology was applied to cut the titanium grade 2. The comparison study was carried out between dry and cryogenic machining. The turning trails were performed using TiN-coated carbide cutting tools. Cutting force measurements surface roughness as well as the tool wear studies were carried out with the Kistler dynamometer, SURFCOM and SEM analysis. From the responses, under cryogenic cooling 32.5% of main cutting force reduction was observed when contrasted to dry condition at a cutting speed of 282 m/min. The 24 % of improved surface quality was observed under cryogenic cooling approach, more fracture on tool rake face was observed under dry condition and the favorable chip formations were also noted under cryogenic cooling approach.

Численное моделирование стружкообразования при лезвийном резании волоконно-армированной композитной заготовки объемного плетения. Часть 1: Обзор и модели материалов

Edge cutting machining is more commonly used to produce precise parts made of fiberreinforced composite (FRC) with three-dimensional woven orthogonal structure. The disadvantage of this machining method is increased hairiness of the machined surface, fiber-matrix debonding, peeling and chipping. One possible solution to minimize this disadvantage is to use rational tool parameters and rational tool wedge motion in relation to the axes of the fibers. Such motion can be identified using numerical computer micro modeling of the chip formation process. The difficulty of such modeling it the need to have available both a geometric model of the composite itself and models of composite components, including a model of matrix-fiber boundary layer. Modeling based on the method of smoothed particle hydrodynamics -Smooth Particle Hydrodynamics (SPH) is the most promising type of machining process micro modeling. Currently, no publications, which present SPH micro models of three-dimensional woven composites with the description of matrix-fiber boundary layers, have been found. It was also not possible to find specific models for the matrix-fiber boundary layers. In order to solve the problem of rational machining of FRC workpieces using edge cutting tools, an analysis of published material models and parameters of such models was carried out. These models should be subsequently used for SPH modeling of the machining process. The analysis made it possible to select the required material models and their parameters for fiber and matrix materials of a metal composite. The analysis of the graphical relationships obtained from the publications, made it possible to select the parameters for the fiber-matrix boundary layer model. This selection is based on the hypothesis that the boundary layer should be described by the same model, that is used for the matrix itself, but with parameters that determine lower failure stresses. The obtained solutions are planned to be used to simulate machining process of a workpiece made of three-dimensional woven FRC in the second part of the presented research.

An improved Lagrange-based numerical model for machining Ti-6Al-4V alloy concerning tool cutting edge microgeometry

Current Lagrange-based machining models usually involve a sacrificial layer (LAG-SL) to facilitate the chip formation. Otherwise, severe element distortion error arises especially when tool cutting edge microgeometry is considered. In view of this limitation, an improved Lagrange-based machining model is proposed that acquires no sacrificial layer (LAG-nSL) and can simulate completely the cutting, unloading and cooling process. Through comparisons with plenty of experimental measurements, the presented model is found not only applicable for machining using tool with various edge radii, but also yields better outcomes of chip morphologies, forces and residual stress distribution.

In-situ test of full field deformation and chip formation mechanism during machining of Ti2AlNb intermetallic with digital image correlation method

Ti2AlNb intermetallic, as a relatively new high temperature-resistant structural material, belongs to typical difficult-to-machine material due to its excellent mechanical properties. This paper aims to investigate the dynamic deformation behavior in chip shear deformation zone and associated chip formation mechanism during the machining of Ti2AlNb intermetallic. A specialized cutting platform combined with a high speed imaging system is developed to realize in-situ detection of full field deformation and corresponding signal processing during the machining process. The high speed imaging system can capture in-situ material deformation images with a frequency of 100 kHz during cutting process while the digital image correlation method is adopted to characterize chip dynamic deformation signals quantitatively. A series of orthogonal cutting experiments for Ti2AlNb is conducted at different cutting depths and cutting speeds, based on which the influences of cutting parameters on chip morphologies and material removal process are studied. The distribution of material flowing velocity, as well as the strain rate fields within shear deformation zone in chip removal process of Ti2AlNb are analyzed. Finally, the formation mechanism of periodic built-up edge formed in the cutting speed range of 60–120 m·min−1 is elucidated.

Analysis of Polyurethane Foam Machining Parameter Influence: Current Status and Perspective

Nowadays, polyurethane (PU) foam has successfully replaced various engineering materials in many applications due to its many advantages in mechanical and thermal properties. In various applications, PU foam must be formed into various 3-dimensional models according to user requirements by utilizing CAM software and CNC milling machining to manufacture a product. Thus, the selection of cutting parameters in the milling machining process in terms of the nature and character of the material and cutting tools is essential and significantly influences the geometric structure and surface roughness of the PU foam products produced. Based on the review of this article, several machining parameters must be appropriately considered, including spindle rotation speed, depth of cut, cutting tool selection, and feed rate. Vibration will increase as the spindle rotation speed increases, which brings cutting tools but results in better surface quality. Continuous chip formation can be achieved by selecting the proper cut depth and producing low surface roughness values. Selecting suitable cutting tools and geometries that match the material characteristics can reduce the risk of material damage during the machining process, thereby reducing the surface roughness value. Finally, a low cutting rate will minimize surface roughness but increase the risk of cutting-edge wear.

A Detailed Study on Algorithms for Predictive Maintenance in Smart Manufacturing: Chip Form Classification Using Edge Machine Learning

A Detailed Study on Algorithms for Predictive Maintenance in Smart Manufacturing: Chip Form Classification Using Edge Machine Learning

Chlorhexidine and doxycycline gel versus chip as adjuncts in oral hygiene among Indians.

The effectiveness of newly released medications such as Chlorhexidine (CHX) chip, Doxycycline hyclate (DH) chip, CHX gel, DH chip as adjunct to scaling and root planing in the treatment of chronic periodontitis is important. 90 adult Indian patients with moderate chronic periodontitis were enlisted. It was observed that reduction in periodontal pocket depth (PPD) and increase in clinical attachment level (CAL) was seen in patients in CHX group as compared to DH treated study participants. It was observed that CHX and DH in gel form were more effective in improving periodontal health as compared to CHX and DH in chip form in this group of subjects.

Chip formation mechanism in milling metallic glasses based on Drucker-Prager (D-P) constitutive model

In this paper, further in-depth research on chip formation mechanism is conducted on the cutting of metallic glasses. The study of chips contributes to a better understanding of the machining nature of materials, which is of significant importance for improving product quality, reducing energy consumption, and resource utilization. This paper employs a combination of simulation and experimental methods, wihch not only analyzes the mechanism of chip formation in depth, but also investigates the time-varying characteristics of cutting forces. The results indicate that, when comparing simulation with experiments, the average error in cutting forces is 7.62%, and the chip morphology is also quite similar. Observations in the simulation show that as the cutting thickness increases from 7.96 μm to 23.87 μm, the free surface of the chip exhibits serrated features, and the main shear zone of the chip becomes clearer. Cutting forces exhibit periodic variations, with alternating peaks and valleys representing the formation of shear zones in the chip. In the experiment, observed chips displays a wrinkled free surface and a smooth non-free surface, with some chip edges exhibiting a burr phenomenon. By selecting appropriate machining parameters, the generation of secondary shear bands on the free surface was effectively reduced. By observing the chip morphology, it is found that the chip formation is accompanied by the material removal of plasticity and brittleness, which is the result of the combined action of heat, stress, and free volume. It should be considered to lower temperature to reduce the phenomenon of chip adhesion, providing guidance for further optimizing the cutting process of metallic glass. This paper can provide to readers further understanding of the chip formation mechanism in milling metal glass.

Material Removal Mechanism and Evolution of Subsurface Defects during Nanocutting of Monocrystalline Cu

Multigroup large-scalenanocutting models of monocrystalline Cu were established by molecular dynamics simulations to investigate the influence of cutting parameters on the material removal mechanism. The formation and distribution of subsurface defect structures were revealed, and the evolution behavior of the complete prismatic dislocation loop was analyzed in depth. It was demonstrated that the chips and machined surface of monocrystalline Cu were mainly formed under the coupling effect of shearing and extrusion forces. A diamond tool with a larger edge radius or a negative rake angle could produce a noticeable suppression on the chip formation. The corresponding relationship between the location of defect atoms and the distribution of von Mises stress was studied, which indicated that the shear stress would become larger at the subgrain boundaries, dislocation lines, and the amorphous atoms than that in their nearby regions. The complete prismatic dislocation loop was formed by cross-slip between two sets of stacking faults; meanwhile, the generated multiple Lomer–Cottrell locks hindered its movement and promoted the work-hardening phenomenon. These research results are of great theoretical value to enrich the nanocutting mechanism and technology of plastic materials.

Study of a Methodology for Calculating Contact Stresses during Blade Processing of Structural Steel

The article presents data about the distribution of contact stresses on the rake surface of the cutter when turning steel (Fe-0.4 C-1Cr), which were obtained by the split cutter method. The article also provides graphs of the effect of the uncut chip thickness a and the rake angle γ on the main parameters of the plots of shear τ and normal σ contact stresses. For this case, The initial data were obtained by longitudinal turning of a steel workpiece with the measurement of the technological components of the cutting force by a three-component Kistler dynamometer, followed by the calculation of the physical components of the cutting force. The rake angle varied widely, from +35 to −10°, and the uncut chip thickness a varied from 0.05 to 0.37 mm. A decrease in the rake angle from +35 to −10° leads to a significant increase in the maximum normal contact stress at the cutting edge σmax: from 400 to 1400 MPa with the uncut chip thickness a = 0.37 mm. In the area of small uncut chip thickness, a (less than 0.1 mm), the paradoxical increase in the magnitude of the greatest normal contact stress with a large positive rake angle (more than +15°) is explained by the indentation (pressing) of the being machined material under the rounded cutting edge of the cutter in the chip formation zone, and their paradoxical decrease with a negative rake angle is due to the presence of a sag (deflection) of the transient surface. According to the magnitude of the reference points obtained on the basis of experimental data, it is possible to plot the contact stresses epures on the rake surface of the cutting tools when machining steel.

Assessment of Machinability of ADI Using Surface Roughness and Resultant Chip Formation as Criteria

Assessment of Machinability of ADI Using Surface Roughness and Resultant Chip Formation as Criteria

Performance evaluation of glycerol and coconut oil added cutting fluid in EN31 turning process

The primary goal of this project is to create a cutting fluid from biodegradable materials that has adequate lubrication and cooling properties to compete with standard commercial cutting fluid, which is non– biodegradable due to the presence of numerous chemicals. This is accomplished through the use of mixed glycerol (GLY) and coconut oil (COCT). Based on the literature review, no one has tried combining glycerol and coconut oil as a cutting fluid. So, in this work, different volume ratios of glycerol and coconut oil were used, and the tribological behavior was studied. The results show that a 50 % GLY + 50 % COCT oil combination had the lowest coefficient of friction. In the turning process, EN31 and a carbide insert were used. The turning was completed in Dry, commercial cutting fluid and the novel cutting fluid (50 % GLY + 50 % COCT).The Surface roughness, temperature, cutting force and chip formation were all taken into account during the machining process the result was compared with commercial cutting fluid. In cutting force,temperature and surface roughness point of view the blended GLY + COCT is best replacement for the existing commercial cutting fluid.