Study Of Chip Formation Research Articles

Chip formation mechanism in machining of Al/SiCp composites based on analysis of particle damage

Particles cracking and debonding are important damage modes that affect the manufacturing processes of Al/SiCp composites. The study of chip formation is the most effective and cheapest way to understand the machining characteristics of a material. Therefore, a comprehensive investigation of the effects of particle damage on the chip formation is of great significance for optimizing the manufacturing processes of Al/SiCp composites. This paper aims to investigate the forming mechanism of particle damage and the effects of particle damage on the chip formation in machining of Al/SiCp composites. The followings are the contributions of this study: (1) According to microscopic observations of chip roots, the forming mechanism of particle damage was revealed. (2) Based on the microscopic observations of cross-section and fracture surface of chips, the effect of particle damage on chip formation was investigated systematically in machining of Al/SiCp composites with varying particle contents and sizes under different cutting conditions. (3) Based on different degrees of particle damage in the chip formation, three novel conceptual models of the chip formation for various fracture types were proposed to visually describe the forming process of chips in machining of Al/SiCp composites.

Numerical study of chip formation and cutting force in high-speed machining of Ti-6Al-4V bases on finite element modeling with ductile fracture criterion

This paper suggests a novel numerical model to accurately simulate the chip formation for a wide range of high cutting speeds. It consists of finite element (FE) modeling of orthogonal machining of titanium alloy (Ti-6Al-4V) in which the Johnson–Cook (JC) material law which can reflect the strain rate hardening and thermal softening influences, and the JC damage law coupled with the displacement-based ductile failure criterion are implemented during the chip formation. Orthogonal machining simulations are performed in a conventional high cutting speed range of 170 to 250 m/min and at the extreme high cutting speeds ranging from 1200 to 4800 m/min, and saw-tooth chips are occurred. The development of chip serration and cutting force are analyzed. It is found that saw-tooth chip formation in high-speed machining of Ti-6Al-4V is the result of ductile fracture. When the cutting speed is increased from conventional to extreme high speeds, the chip morphology changes with varying the fracture behavior. The numerical model is also verified by comparing predicted results with available experimental data in the literature. The results indicate that chip morphology and cutting force can be accurately acquired using the ductile failure criterion in high-speed machining of Ti-6Al-4V.

Experimental evaluation of the minimum uncut chip thickness (MUCT) in AISI H13 steel, using the end milling operation

The increasing market demand for smaller products requires the development of micromachining processes. This, in turn, enhances the importance of knowledge about the phenomenon of chip formation and its characteristics at the microlevel. Conventional machining generally assumes that the tool cutting edge is perfectly sharp, and that it usually does not affect the chip formation process. However, in micromachining, the magnitude of the edge radius (re) is often the same as that of the chip thickness, thus significantly affecting the process. Moreover, the study of chip formation at the microlevel is even more complex. In micromachining, as the chip thickness decreases, it reaches a minimum thickness at which a chip is still formed, called the minimum uncut chip thickness (MUCT). Therefore, the purpose of this work is to use an experimental method, based on milling, to reach the MUCT (hmin) by simulating a micromilling operation. AISI H13 steel was used in two conditions: hardened and as received, with around 60 and 25 HRc, respectively. The experiments were performed according to a novel method simulating end milling in orthogonal cut. It was found that hmin varied from 0.56re to 2.5re, and that this range depends not only on re but also on the material being machined and on the mechanical compliance of all the equipment used in the test. Based on the theory of contact mechanics, it was possible to explain that a chip is formed only after the cutting edge has attained the necessary stresses to cause failure of the material being tested, and this knowledge is fundamental to understand the occurrence of hmin. In addition, the method used here was successful in reaching hmin values typically obtained in milling conditions. Using the same method proposed herein, future studies of MUCT can be performed employing even conventional machine tools.

Chip formation during thermal friction turn milling

This paper presents the results of chip formation studies in the processing of 30KhGSA steel by thermofriction turn-milling. When studying the process in this work there are presented the results of studying chip formation when the processing of chip formation there is used the metallographic method. Chip root area investigated.The dependence of the chip shrinkage coefficient on the cutting speed and feed was also investigated. It is established that with increasing supply S the value of the chip shrinkage coefficient K decreases. The higher the chip shrinkage factor, the more work will be required to cut the chips and the more complex the processing process.

A Study of Chip Formation on Turning with Minimum Quantity Lubrication Method (MQL)

The cutting fluid is one of the essential factors in machining to increase machinability. The issuance of ISO 14000 about reducing the use of cutting fluid for its danger for operator and environment has encouraged many researchers to find ways to minimize its use. The Minimum Quantity Lubrication (MQL) is an answer to it. To further reduce the use of cutting fluid, a device that complies with MQL criteria for controlling the spray based on the tool temperature has successfully designed. This paper is discussing the effect of applying this device to the chips formation. The experiments were on turning of AISI 4340 using carbide tools. The Taguchi method L9 used to design the experiments. The variations made on the method of applying the cutting fluid, depth of cut, and cutting fluid composition. The chips formation was calculated based on the value of the degree of serration. Analysis of the S/N ratio, followed by ANOVA, revealed that the cutting fluids application method is the least factor affecting the chips formation. In contrast, the depth of cut influences the chips formation by 75 per cent more. The highest degree of serration achieved when applying the combination of depth of cut of 1.8 mm, the composition of 5:5, and flood method of applying cutting fluid.

Comparative Study of Chip Formation in Orthogonal and Oblique Slow-Rate Machining of EN 16MnCr5 Steel

In today’s unmanned productions systems, it is very important that the manufacturing processes are carried out efficiently and smoothly. Therefore, controlling chip formation becomes an essential issue to be dealt with. It can be said that the material removal from a workpiece using machining is based on the degradation of material cohesion made in a controlled manner. The aim of the study was to understand the chip formation mechanisms that can, during uncontrolled processes, result in the formation and propagation of microcracks on the machined surface and, as such, cause failure of a component during its operation. This article addresses some aspects of chip formation in the orthogonal and oblique slow-rate machining of EN 16MnCr5 steel. In order to avoid chip root deformation and its thermal influence on sample acquisition, that could cause the changes in the microstructure of material, a new reliable method for sample acquisition has been developed in this research. The results of the experiments have been statistically processed. The obtained dependencies have uncovered how the cutting tool geometry and cutting conditions influence a chip shape, temperature in cutting area, or microhardness according to Vickers in the area of shear angle.

Experimental and numerical study of chip formation in orthogonal cutting of Ti-5553 alloy: the influence of cryogenic, MQL, and high pressure coolant supply

This study presents investigation of chip formation process of Ti-5553 alloy that is a next generation near beta titanium alloy and has potential to be replaced with commonly used Ti-6Al-4V due to its superior properties such as high corrosion and fatigue resistance. Experimental part of this study includes orthogonal cutting process of Ti-5553 alloy under dry, cryogenic, minimum quantity lubrication (MQL) and high pressure coolant (HPC) conditions. Various cutting speeds were taken into account to observe chip-tool contact length, forces, temperature, chip morphology resulting from various machining conditions. Experimental study demonstrates that HPC and cryogenic help to improve chip formation process of this alloy. By implementing Johnson–Cook model, orthogonal cutting process of this alloy in dry and cryogenic conditions is simulated utilizing Deform 2D commercial software. Predicted force, temperature, and chip morphology show good agreement with experimentally measured data.

Chip formation characteristics of selective laser melted Ti–6Al–4V

In this research work, chip formation characteristics of selective laser-melted (SLM) Ti–6Al–4V in both ‘as built’ and ‘heat treated’ conditions are studied and compared with conventional wrought Ti–6Al–4V. Machined chips and partially deformed chips were collected from turning trials and quick stop experiments to study the nature of chip formation characteristics. Chip formation studies reveal that, ‘segmented’ or ‘saw tooth’ chips were produced during machining of SLM Ti–6Al–4V materials. The tendency to form segmented chips was higher in SLM Ti–6Al–4V materials as compared to conventionally produced wrought Ti–6Al–4V. In addition, cracks were found to be a common feature in primary and secondary deformation zones of SLM Ti–6Al–4V chip samples, illustrating that periodic crack initiation is the root cause of ‘saw tooth’ formation during machining. Furthermore, the tendency to form build up edge during machining was less in SLM Ti–6Al–4V materials compared to wrought Ti–6Al–4V, influencing the machined surface finish.

SPH Simulation of single grain action in grinding

The paper presents a study of chip formation in single grain grinding using a convenient FEM formulation, the Smooth Particle Hydrodynamics (SPH) method. The chip formation process was geometrically idealized. It was simulated as an inclined linear scratching of a cuboid part. After a systematic study, the results prove that this approach is useful to study the influence of grinding speed, friction conditions and uncut chip thickness on grinding forces, stresses and strains occurring during the grain action.

Multi-scale study of initial tool wear on textured alumina coating, and the effect of inclusions in low-alloyed steel

When turning low-alloyed steel with hard inclusions, scores and grooves have been observed in the wear of the alumina coating in CVD coated cutting tools. This study focuses on detailed understanding of flank wear in the textured alumina coating and the relation to the workpiece׳s inclusions.For chip formation studies, a quick stop device has been used. A topography analysis for the worn coating was performed in the micro scale. Studies at lower scales were performed using TEM. This allowed the study of wear on the coating crystalline structure and the embedment of workpiece material on its surface.Based on the results, the mechanism behind the initial wear was analyzed and an abrasion wear model is proposed.

Material constitutive model and chip separation criterion influence on the modeling of Ti6Al4V machining with experimental validation in strictly orthogonal cutting condition

The titanium alloy Ti6Al4V, although widely used in machining, is a hard-to-machine material, particularly due to the production of saw-toothed (or segmented) chips. The phenomena leading to this kind of chips are still an ongoing problem in the current literature, as well experimentally as numerically. An experimental orthogonal cutting setup on a milling machine is presented as a benchmark to validate finite element models. Its ease of implementation and near-to-zero cost should enable it to be used for any material, as long as the cutting speed is achievable by the feed rate of the machine. In addition to the study of chip formation, this setup could also allow to carry out long, although interrupted, machining tests to analyze tool wear. A numerical finite element model is then introduced to model the chip formation in the same cutting conditions. The comparison of the numerical results with the experiments shows that the level of the forces is mainly influenced by the material constitutive model, while the chip morphology is mostly impacted by the chip separation criterion. Either experimentally or numerically, the mechanism leading to the formation of a Ti6Al4V saw-toothed chip, for the cutting conditions of this study, is the conjunction of the adiabatic shear band in the primary shear zone, followed by the propagation of a crack into it.

Study of Chip Formation in Hard Turning of AISI 4340 Alloy Steel in Different Cutting Environments

Study of Chip Formation in Hard Turning of AISI 4340 Alloy Steel in Different Cutting Environments

A study of chip formation in ductile-regime machining of 6H silicon carbide by molecular dynamics

Much effort have been devoted to the ductile regime machining of silicon carbide (SiC) in recent years. However, a thorough understanding on the mechanism of chip formation has not been achieved. In this study, large scale molecular dynamics simulations are performed to investigate the ductile-regime machining of 6H SiC. It is found that the mechanism of chip formation transforms from shearing to extrusion when the tool rake angle varies from 0° to −40°. The nature of plastic deformation is slipping processes on the basal slip system of 6H SiC and shearing along several inclined planes. Under a rake angle of −40°, a 'pseudo edge' is observed in front of the cutting edge throughout the cutting process. Under a rake angle of −20', a periodic process of formation and vanishing of 'pseudo edge' is observed. The formation of 'pseudo edge' leads to a decrease in the principle cutting force, and its vanishing is followed by increase of principle cutting force.

Quantitative Characterization of Chip Morphology Using Computed Tomography in Orthogonal Turning Process

The simulation of machining process has been an area of active research for over two decades. To fully incorporate finite element (FE) simulations as a state of art tool design aid, there is a need for higher accuracy methodology. An area of improvement is the prediction of chip shape in FE simulations. Characterization of chip shape is therefore a necessity to validate the FE simulations with experimental investigations. The aim of this paper is to present an investigation where computed tomography (CT) is used for the characterization of the chip shape obtained from 2D orthogonal turning experiments. In this work, the CT method has been used for obtaining the full 3D representation of a machined chip. The CT method is highly advantageous for the complex curled chip shapes besides its ability to capture microscopic features on the chip like lamellae structure and surface roughness. This new methodology aids in the validation of several key parameters representing chip shape. The chip morphology's 3D representation is obtained with the necessary accuracy which provides the ability to use chip curl as a practical validation tool for FE simulation of chip formation in practical machining operations. The study clearly states the ability of the new CT methodology to be used as a tool for the characterization of chip morphology in chip formation studies and industrial applications.

Analysis of Chip Formation Mechanism in Mill-grinding of SiCp/Al Composites

SiCp/Al composites are one kind of difficult-to-machine material. The material removal mechanism of this material is complex due to the existence of SiC reinforcement. The chip formation reflects its material removal process to a certain extent. In this article, a study of chip formation is described, and a basic physical cutting model is presented to help reveal chip formation mechanism in mill-grinding of SiCp/Al composites. The scanning electron microscope photos are used to analyze the characteristic of chip morphology. Observed results based on the materials used in the experiment indicated that there were mainly four typical chip shapes, among them schistose chips being dominant. The chip formation mechanism depended much on plastic deformation of aluminum matrix, contact position between SiC particle and diamond grit, and the removal mode of SiC particle. Under the same machining conditions, the chips generated are irregular and uneven, and include several kinds of shapes. The effect of size of SiC particles on the morphology of chips formed was also analyzed based on correlational studies and the physical cutting model for SiCp/Al composites.

High-Speed Photographic Study of Chip Formation during End Milling of GFRP Composites

The chip forming process during end milling of glass fibre reinforced composites has been investigated in this study. The qualitative results from a high speed video camera has showed that discontinuous and fracturing of chips has been created due to the heterogeneity and insufficient ductility of the composite materials. The high-speed photography footage has also disclosed that a layer of delaminated chip can be formed as the tool cutting edge fractured the workpiece along the fibre orientation. The fracture of chips into smaller segments accelerated as the cutting speed increases. Likewise, shorter fragment of chips were created as the tool cut at different fibre orientation or angle. This makes it difficult to denote any chip formation processes during the end milling experiments.

Influence of graphite particles on surface roughness and chip formation studies in turning metal matrix composites

This study presents an experimental investigation on surface roughness and chip formation in turning of Al 2219/15SiCp and Al 2219/15SiCp-3Gr (hybrid) composites. Experiments were conducted with different cutting conditions using carbide, coated carbide and polycrystalline diamond (PCD) tools. The results reveal that the surface roughness values are less for coated carbide tools compared to carbide and are minimum for PCD tools. The incorporation of graphite in Al 2219/15SiCp composite increases the surface roughness. This is due to smearing and removal of softer and amorphus graphite particles on the surface of the specimen, creates pits on the machined surface which increases the surface roughness values. The graphitic composite produced discontinuous chips leads to easy machining. PCD tool performs better than carbide and coated carbide tools.

Chip formation studies in machining fibre reinforced polymer composites

The use of end milling process for machining of fibre reinforced polymer composites has been widespread in various industries. Until recently, very little work has been reported with regard to characterisation of chip formation mechanisms while end milling these composite materials. This paper reports such study which was accomplished via high speed photography and quick stop procedure. It is apparent that the heterogeneity and insufficient ductility of the composites have produced discontinuous and fracturing chips. Information disclosed by the high-speed photography footages has shown that a layer of delaminated chip was formed as the tool cutting edge fractured the workpiece along the fibre orientation at the lowest cutting speed. The increased cutting speed accelerates the fracture of chips into smaller segments, which make it difficult to denote any chip formation processes. Similarly, shorter chip fragments were created as the tool cut at different fibre orientation (45° and 90° with respect to tool feed direction).

Experiment Study of Chip Formation and Cutting Force of Hardened AISI 1045 Steel in High Speed Machining

Orthogonal cutting experiments of hardness AISI1045 steel( HRC45) are performed. The change of chip formation and cutting force with cutting conditions are investigated through metallurgical observation, and the critical cutting speed of adiabatic shear of AISI1045 steel at different cutting depths and rake angles are given. In addition, the saw-frequency and space length of serrated chip and the influence of serrated chip on cutting force are also studied. The critical cutting speed decreases with the increase of cutting depth, but increases with the increase of rake angle. The saw-frequency of serrated chip is found to be independent of the cutting depth, and increases with the increase of cutting speed and rake angle. The cutting force decreases with the increase of cutting speed and rake angle, but increases with the increase of cutting depth, and there isn’t a sudden change of cutting force at the onset of adiabatic shear.

Experimental and Numerical Machining of AA 5083

The experimental machining and finite element modeling of 2D turning of AA5083 is presented. The ABAQUS/Explicit machining simulation software is applied for the finite element modeling. The experimental orthogonal machining for were conducted to investigate the effects of various machining parameters on chip morphology, machined surface condition, and resulting cutting forces. The measured cutting forces was compared to finite element modeling results with good agreement. The effects of cutting speed and rack angle of tool cutting factor for productivity in AA5083 machining, depth of cut, on the peak tool temperature are investigated. 2D Finite Element Model (FEM) of chip formation process, set up with an Arbitrary Lagrangian-Eulerian (ALE) formulation, proposed in the software ABAQUS/Explicit .the thermo-viscoplastic behavior of the workpiece material is modeled by the Johnson-Cook (JC) constitutive law. This study explores the use of experimental and finite element modeling to study the cutting force. Results of this research help to guide the design of new cutting tool materials and coatings and the studies of chip formation to further advance the productivity of AA5083 machining.