Chip Radius Research Articles

Investigation on cutting deformation behavior of Al/SiCp composites considering particle feature distributions

Al/SiCp composite machining is considerably difficult owing to the presence of abrasive particles that results in weak synergetic deformation capacity during cutting. Therefore, to enhance the machinability of Al/SiCp composites, investigations on the cutting deformation behavior are imperative through finite element simulation. Aiming to address the limitations of conventional finite element models in accurately representing the actual microstructure of Al/SiCp composites, this study proposes a realistic microstructure-based finite element model to investigate the cutting deformation and damage behavior. The microstructural characteristics of the composites namely, particle feature distributions, including size distribution, aspect ratio distribution, and spatial aggregation of SiC particles, are analyzed and extracted based on the microstructure image of composite and the Gaussian stochastic model. Then, the particle feature distributions are incorporated into the microstructure-based model for the first time. Besides, all the failure mechanisms (i.e., the brittle fracture of SiC particles, the elastoplastic damage of Al matrix, as well as the particle-matrix decohesion) and the tool-chip contact behavior are comprehensively integrated into the modeling. The experimental results show that as the particle volume fraction and size increase, the chip radius and the number of chip curls decrease, the chips vary from little waviness to prominent saw-tooth type, and more particles are broken or debonded. According to the comparison with experimental results, the finite element model can effectively capture the deformation and failure process, as well as the characteristics of chip morphology, cutting force, and machined surface quality. In addition, the comparisons further demonstrate that SiC particles with large size, slender shape, and aggregation are prone to fracture and detachment in the cutting deformation. Finally, the influences of the particle feature distributions on the machinability of Al/SiCp composites are discussed in detail. It is found that decreasing the dispersion degree of particle size and aspect ratio distribution as well as minimizing the degree of particle clustering degree benefit the machinability of Al/SiCp composites.

Study on tool wear mechanism and chip morphology during turning of Inconel 713C by textured inserts

The present study aims to analyze the tool wear mechanism and chip morphology during dry (D) and graphene solid-lubricant (S), turning of Inconel 713C with a new novel textured (honeycomb (T2) and rectangular(T3)) and further compare with the textured dimple tool (T1). In addition, the performances were compared with the untextured tool (T0). The machining tests for all conditions were carried out at different levels of cutting speeds (75 m/min and 150 m/min), feed rate (0.1 mm/rev and 0.2 mm/rev), and a constant level of depth of cut (0.5 mm). Honeycomb-textured cutting tools performed better. Improvements of 33.3 % (T1D), 50 % (T3D), and 75 % (T2D) without graphene and 66.6 %(T1S), 75 % (T3S), and 100 %(T2S) with graphene are observed compared to T0. The primary mechanism for the better performance of T2S was the reduced tool chip contact length (8–50 %), chip width (30.4 %), friction coefficient (57.4 %), chip thickness (17.8 %), and higher shear angle (14.2 %) compared to dry textured and untextured tools at the end of tool life. Additionally, the T2S (solid lubricant-impregnated honeycomb) demonstrates a decrease in equivalent chip thickness (19.8 %) and an increase in shrinkage factor (17.2 %) at worn-out tool life conditions at high cutting speed and feed rate. Under the same conditions, T2S has 27.3 % lower cutting force and 36.2 % lower surface roughness of machined workpieces compared to the untextured tool at the end of tool life. The chip micrograph reveals the chips are shorter, and the chip radius is lower for T2S tools with smooth friction tracks and fine deformed lamella on the free surface of the chip. Under SEM, flank wear, adhesion materials, abrasion, micro-chipping coating peeling, and BUE were dominant wear mechanisms. However, T2S tools effectively reduce Ni elements' diffusion and suppress the built-up edge's adhesion by improving friction characteristics at the tool-chip interface region. Lastly, the outcomes of experimental results suggest that the honeycomb texture for dry machining of Inconel 713C.

Forming process and evaluation of chip in machining of high-strength steel by an independent-developed microgroove turning tool.

Chip morphology is one of the evaluation indexes of cutting performance of cutting tools, and chip forming process has a direct and important influence on chip morphology. High-strength steel 40CrMnMo is one of typical oil country tubular goods (OCTG) and difficult-to-cut materials, and its chip morphology represents the machining quality of OCTG. The chip forming process of a new independent-developed microgroove turning tool for turning oil country tubular goods 40CrMnMo is researched, combining machining experiments with theoretical analysis. Research results show that with the increase of cutting speed, the initial radius of curvature of the chip fluctuates slightly, but the overall trend is upward. However, the ultimate radius of curvature decreases and the chip's radius ratio also decreases. The relative ideal chip can be obtained if the proper cutting velocity and feed rate are given. Chip morphology results from the comprehensive effect of the two processes: The fracture and separation process of the workpiece during passing through the shear deformation zone and the process of curling and breaking away of the chip after passing through the rake face of the tool. The research results have a certain guiding significance for controlling the cutting process of machining the other material with similar performance.

Cutting performance of micro-textured PCBN tool

To study the effect of micro-texture on the cutting performance of polycrystalline cubic boron nitride (PCBN) tools, five types of micro-textures (circular pits, elliptical grooves, transverse grooves, composite grooves, and wavy grooves) were applied to the rake surface of PCBN tools by an optical fiber laser marking machine. Through a combination of three-dimensional cutting simulations and experiments, the influences of micro-texture on chip–tool contact area, cutting force, chip morphology, shear angle, and surface roughness during the cutting process were analyzed. The results indicated that the chip–tool contact area and cutting force of both non-textured and micro-textured tools increased with increasing cutting speed, while the shear angle decreased with increasing cutting speed. The chip–tool contact area and cutting force of the five types of micro-textured tools were smaller than those of the non-textured tool. The chip–tool contact area and cutting force obtained by the wavy-groove micro-textured tool were the smallest. The chip radius produced by the five types of micro-textured tools was smaller than that produced by the non-textured tool, and the chip morphology was more stable. The transverse-groove micro-textured tool had a better chip breaking effect. The chip radius generated by the elliptical-groove micro-textured tool was 0.96 cm, while that generated by the wavy-groove tool varied from 0.55 cm to 1.26 cm. The presence of a micro-texture reduced the surface roughness of the workpiece by 11.73%–56.7%. Under the same cutting conditions, the five types of micro-textured tools gave a smaller chip–tool contact area, cutting force, chip radius, and surface roughness and a larger shear angle than the non-textured tool. In addition, the elliptical-groove and wavy-groove micro-textured tools had better cutting performance.

Considering multiple process observables to determine material model parameters for FE-cutting simulations

Analyzing the chip formation process by means of the finite element method (FEM) is an established procedure to understand the cutting process. For a realistic simulation, different input models are required, among which the material model is crucial. To determine the underlying material model parameters, inverse methods have found an increasing acceptance within the last decade. The calculated model parameters exhibit good validity within the domain of investigation, but suffer from their non-uniqueness. To overcome the drawback of the non-uniqueness, the literature suggests either to enlarge the domain of experimental investigations or to use more process observables as validation parameters. This paper presents a novel approach merging both suggestions: a fully automatized procedure in conjunction with the use of multiple process observables is utilized to investigate the non-uniqueness of material model parameters for the domain of cutting simulations. The underlying approach is two-fold: Firstly, the accuracy of the evaluated process observables from FE simulations is enhanced by establishing an automatized routine. Secondly, the number of process observables that are considered in the inverse approach is increased. For this purpose, the cutting force, cutting normal force, chip temperature, chip thickness, and chip radius are taken into account. It was shown that multiple parameter sets of the material model can result in almost identical simulation results in terms of the simulated process observables and the local material loads.

Fuzzy Logic-Based Prediction of Drilling-Induced Temperatures at Varying Cutting Conditions along with Analysis of Chips Morphology and Burrs Formation

Friction and plastic deformation at the tool–chips interaction during a dry drilling process results in temperature rise and promotes tool wear and surface roughness. In most of the components produced in industries, a drilling process is used to make a hole for final assembly. Therefore, knowledge of temperatures produced during drilling operation at various machining input parameters is required for the best quality product. A fuzzy logic-based algorithm is developed to predict the temperature generated in the drilling process of AISI 1018 mild steel. The algorithm used speed and feed rate of the drill bit as input parameters to the fuzzy domain. A set of rules was used in the fuzzy domain to predict maximum temperature produced in the drilling process. The developed algorithm is simulated for various input speed and feed rate parameters and was verified through the maximum temperature measured during drilling of the studied material at selected speed–feed combinations. Experiments were conducted to validate the results of developed fuzzy logic-based algorithm by using non-contact infrared pyrometer for drilling of AISI 1018 steel. A good agreement between the predicted and experimentally measured maximum temperature was observed with an error less than 6%. It is found that temperature increases with increase in cutting speed and feed rate. Size of roll back burr formation at the hole perimeter significantly increases with increase in drill speed and feed rate. Segmental continuity in spiral or helix chips morphology is more at low feed and high cutting speed. Chip radius increases with increase in feed rate and results in damaging of the machined surface and causes burr formation while the radius decreases with cutting speed along with improved hole surface finish.

Transient Temperature Field Analysis of Thyristor Turn-on Process under Narrow Pulse Width and Large Current

Thyristor will damage because of local overheating under narrow pulse width and large inrush current, if the selection is unreasonable. In this paper, the thermal field model of thyristor opening process is established and the transient temperature field distribution of thyristor is obtained by simulation. Simulation results show that under the narrow pulse width and large current, the temperature distribution on the silicon chip is not uniform, the temperature at the center gate is the highest, and the temperature is gradually decreased from the center point along the radius. The effect of current rise rate and chip radius on thyristor temperature distribution are simulated. Simulation results show that the higher the current rise rate, the higher the temperature of the thyristor center gate. The effect of chip radius on thyristor temperature is related to the pulse width of large inrush current. When the chip radius is smaller than the extended radius corresponding to the current pulse width, the smaller the radius, the higher the maximum temperature rise. When the radius of the chip is equal to or greater than the extended radius corresponding to the current pulse width, increasing the radius of the chip has no effect on the highest temperature rise.

A new hybrid model based on the radius ratio for prediction of effective cutting limit of chip breakers

Determination of accurate limit of cutting condition in order to obtain broken chips for various chip breaker geometries is essential to improve the machinability. This work presents a hybrid model based on the ratio of broken chip radius to the initial radius of chip to predict the type of chip regarding the characteristics of a chip breaker geometry and cutting parameters. An analytical geometrical model was developed to calculate the initial radius of chip. After running experimental tests for four types of chip breaker geometries and calculation of their chip ratio, type of chips and tool–chip contact were selected as two criteria for classifying chip ratio into three limits representing usable, acceptable, and unacceptable chips. Finally, the normalized data were used to train a neural network model to predict the type of chip which was verified by experiments carried out on a new chip breaker geometry. The trained network could predict the type of chip accurately by providing the geometrical details of the chip breaker and cutting parameters for the network.

Cutting Tool Crater Wear Measurement in Turning Using Chip Geometry and Genetic Programming

Tool wear prediction plays an important role in industry automation for higher productivity and acceptable product quality. Therefore, in order to increase the productivity of turning process, various researches have been made recently for tool wear estimation and classification in turning process. Chip form is one of the most important factors commonly considered in evaluating the performance of machining process. On account of the effect of the progressive tool wear on the shape and geometrical features of produced chip, it is possible to predict some measurable machining outputs such as crater wear. According to experimentally performed researches, cutting speed and cutting time are two extremely effective parameters which contribute to the development of the crater wear on the tool rake face. As a result, these parameters will change the chip radius and geometry. This paper presents the development of the genetic equation for the tool wear using occurred changes in chip radius in turning process. The development of the equation combines different methods and technologies like evolutionary methods, manufacturing technology, measuring and control technology with the adequate hardware and software support. The results obtained from genetic equation and experiments showed that obtained genetic equations are correlated well with the experimental data. Furthermore, it can be used for tool wear estimation during cutting process and because of its parametric form, genetic equation enables us to analyze the effect of input parameters on the crater wear parameters.

Investigation of machining performance in high pressure jet assisted turning of Inconel 718: A numerical model

This study aims at investigating the effects of high-pressure jet assistance (HPJA) in rough turning of Inconel 718. A finite element (FE) model for orthogonal machining has been developed in order to reach additional data, compare trends to the experimental ones and understand the influence of the jet on the cutting process. Mechanical and thermal loads induced by the jet are considered. Consequences on the primary and secondary shear zones, chip formation and tool rake face have been studied on a whole pressure range (30–130 MPa) and compared to dry cutting. It is shown that the jet is able to decrease the cutting forces, chip radius and tool–chip contact length. Contact pressure and temperature fields on the cutting tool are also reduced as well as the sticking part of the contact zone. Authors confirmed that the effects of convection are able to change and even amplify the influence of the pure mechanical load induced by the jet.

Influence of Chip Curl on Tool-Chip Contact Length in High Speed Machining

The tool-chip contact length, as an important parameter controlling the geometry of tool crater wear and understanding chip formation mechanism, is widely investigated in machining. The aim of this paper is to study the influence of chip curl on tool-chip contact length by means of experimental observations with high cutting speed. The relationship between tool-chip contact length, chip radius of curvature and uncut chip thickness was investigated. Experimental results show the effect of increasing spiral chip radius on tool-chip contact length with low uncut chip thickness in high speed machining.

Investigation of dry machining with embedded heat pipe cooling by finite element analysis and experiments

This paper investigates the performance of a cutting tool embedded with a heat pipe on reducing cutting temperature and wear in machining. The temperature of a tool plays an important role in thermal distortion and the machined part’s dimensional accuracy, as well as the tool life in machining. A new embedded heat pipe technology has been developed to effectively remove the heat generated at the tool–chip interface in machining, thereby, reducing tool wear and prolonging tool life. In particular, the technique can effectively minimize pollution and contamination of the environment caused by cutting fluids, and the health problems of skin exposure and particulate inhalation in manufacturing. The ANSYS finite element analysis simulations show that the temperature near the cutting edge drops significantly with an embedded heat pipe during machining. Temperature measurements at several locations on the cutting tool insert agree with the simulation results both with and without the heat pipe. Experiments were carried out to characterize the temperature distributions when performing turning experiments using a cutting tool installed with an embedded heat pipe. The performance of the heat pipe on reducing the cutting tool temperature was further supported by the observations of cutting tool material color, chip color, and the chip radius of curvature.

An analysis of strain in chip breaking using slip-line field theory with adhesion friction at chip/tool interface

A slip-line field model for orthogonal cutting with step-type chip breaker assuming adhesion friction at chip/tool interface is developed using Kudo's basic slip-line field. An alternative method is suggested for estimation of breaking strain in the chip. The model proposed predicts that with decrease in distance of chip breaker from the cutting edge of the tool, the breaking strain and shear strain in the secondary deformation zone increase while the total plastic strain decreases. The breaking of the chip is found to be solely dependent on the breaking strain, and not on ‘material damage’ or the specific cutting energy. The chip radius of curvature, cutting ratio, range of position of chip breaker for effective chip breaking are computed. The calculated results are found to be in general agreement with experimental measurements.

Investigation of the direction of chip motion in diamond turning

Management of the chips generated in diamond turning is often critical since contact between chips and the workpiece can result in superficial damage to the finished surface. Controlling chip motion is not a trivial process as the proper positioning of an oil or an air stream requires an understanding of the dynamics of a diamond turned chip and the machining parameters that affect it. Previous work [1] introduced the chip curvature parameter, χ, which is useful in predicting chip radius of curvature over a wide range of cutting speeds, depths of cut, tool geometries and workpiece material properties. To control chip motion, however, an understanding of the direction chips leave the tool/workpiece interface must also be obtained. Cutting experiments were performed investigating the influence of cutting speed, depth of cut, feed rate, tool path angle, tool geometry and tool orientation on the directional characteristics of the motion of diamond turned chips. Flow angle measurements obtained during cutting were found to remain within ± 10° of predictions from a simple geometrical model originally proposed for conventional machining.

Investigation and prediction of chip geometry in diamond turning

Management of the chips generated in diamond turning is often critical, because contact between chips and the workpiece can result in superficial damage to the finished surface. Controlling chip motion is not a trivial process as the proper positioning of an oil or air stream requires an understanding of the dynamics of a diamond turned chip and the machining parameters that affect it. Work has been performed to investigate the effects of cutting speed, depth of cut, tool geometry, tool wear, and workpiece material properties on chip motion and geometry. Utilizing radius of curvature data from cutting experiments, a parameter has been proposed that can be used to predict chip radius of curvature for a wide range of machining conditions. This chip curvature parameter, χ, exhibits a power law relationship with chip radius of curvature as a function of tool geometry, depth of cut, cutting speed, and both elastic and plastic properties of the workpiece material.

Slip-line solution for orthogonal cutting with a chip breaker and flank wear

A slip-line field model for orthogonal cutting with chip breaker and flank wear has been developed. For a worn tool, this slip-line field includes a primary deformation zone with finite thickness; two secondary shear zones, one along the rake face and the other along the flank face; a predeformation zone; a curled chip; and a flank force system. It is shown that the cutting geometry is completely determined by specifying the rake angle, tool-chip interface friction and the chip breaker constraint. The chip radius of curvature, chip thickness, and the stresses and velocities within the plastic region are readily computed. Grid deformation patterns, calculated with the velocity field determined, demonstrate that the predicted effects of changes in frictional conditions at the tool-chip interface and of the rake angle on chip formation are in accord with experimental observations. The calculated normal stress distribution at the tool-chip interface is in general agreement with previously reported experimental measurements. The model proposed predicts a linear relationship between flank wear and cutting force components. The results also show that non-zero strains occur at and below the machined surface when machining with a worn tool. Severity and depth of deformation below the machined surface increases with increasing flank wear. Forces acting on the chip breaker surface are found to be small and suggest that chip control for automated machining may be feasible with other means.

Effect of head/Disc imperfections on gas lubricated slider performance

The effect of head/disc imperfections on gas lubricated slider performance is investigated using a numerical simulation. The imperfections considered are warping and chipping/pimpling of the rails and waviness and asperities on the disk. A predictor-corrector numerical marching scheme is employed to obtain the solutions for the system of governing equations which includes the Reynolds equation and the slider equations of motion. The warp length of the slider seem to affect the trailing edge flying height considerably and is more critical at low frequency waviness of the disk. Trailing edge flying height increases with increasing chip radius and decreases with increasing dimple radius for all disk waviness frequencies.

Some aspects of chip control in profile boring

The problems associated with chip removal during profile boring are highlighted and the effect of using a chip curler pad on the rake face of ISO triangular inserts investigated. The chip types obtained by varying the geometry of the chip curler pads are observed and the conditions under which a forward flowing continuous helical chip is obtained are determined. This chip type is of use when machining ‘through holes’ where the chip can flow along the bore in advance of the boring bar, through the hollow lathe spindle to be collected at the rear of the lathe. This method of chip collection simplifies chip removal problems in profile boring. Some illustrative examples of the effect of cutting conditions on chip radius and pitch of the chip helix are given and the chip form is shown to depend on the workpiece geometry in addition to the Cutting tool/chip curler geometry.

Metal cutting: Mechanics, surface physics and metallurgy

Orthogonal planing experiments have been carried out on 70/30 brass workpieces in the cutting speed range 0·3–150 ft/min. Measurements of chip radius, shear plane angle and the average coefficient of friction between chip and tool have been made and their inter-relationships are successfully explained in terms of a slip line field theory. For a non-hardening workpiece, chip shape is completely determined by the friction stress distribution between chip and tool, but three parameters are required to define this sufficiently, rather than the one, the coefficient of friction, of earlier theories. Lathe turning experiments on a large number of different metals in the speed range 200–800 ft/min indicate that for these materials, chip shape is also determined by the friction stress distribution between chip and tool. The friction stress distribution is determined both by the mechanical strength, under the deformation conditions of the cutting experiment, of the chip material adjacent to the rake face of the tool and by the distribution over the rake face of the ratio of the real to apparent area of contact between chip and tool.

Analysis of Rod Shaving and Orthogonal Cutting

The relationship between shaving and drawing or extension is discussed. For small reduction ratios, this relationship is evidenced by a transition from converging flow of the metal to shaving as the tool angle is increased. This transition is defined as the critical rake angle for shaving. An expression for the relative pressure required for orthogonal cutting is derived through the upper-bound approach. With this as a basis, an approximate upper-bound solution for shaving is obtained. This equation gives the relative stress or pressure required for shaving as a function of the process variables, both dependent and independent. The independent variables are rake angle (α), reduction ratio (R0/Rf), relative back stress (σzb/σ0), and friction factor (m). The dependent variables are defined as relative chip radius (r0/t0), relative chip velocity (ωr0/v0), and built-up edge angle (α1). Results of a computer minimization procedure for this equation are presented. In this technique, the required relative stress for shaving is determined through trial-and-error variation of the dependent variables for selected combinations of the independent variables. These results are used to predict the critical rake angle for shaving and the critical rake angle for disappearance of the built-up edge. Comparison with experimental results indicates that the prediction of the critical angle for shaving is useful.