Cutting Edge Radius Research Articles

МОДЕЛИРОВАНИЕ УСКОРЕННЫХ ИСПЫТАНИЙ НОЖЕЙ РЕЖУЩЕ-ИЗМЕЛЬЧАЮЩИХ АППАРАТОВ КОРМОУБОРОЧНЫХ КОМБАЙНОВ

A method is proposed and a technique is developed for accelerated bench tests in laboratory conditions of knives of cutting-reducing devices of forage harvesters. One of the main purposes of the developed method is an experimental comparative assessment of the long-term performance (according to the wear resistance criterion) of various knife options (according to the materials for their manufacture and structural and geometric parameters). The proposed test method solves the problem of assessing the wear resistance of agricultural harvester knives by two parameters: physical depreciation and dulling of their cutting edge. A flexible belt with an abrasive fixed on one of its surfaces is used as counter-specimens during testing, which allows for wear with sliding impact and thereby significantly accelerates the process of knives damage. The technique makes it possible to test simultaneously two knives made using different technologies, under comparable conditions. In addition, to speed up testing, not one, but several counter-specimens are mounted on the test equipment. As a result of such tests, the process of impact-fatigue loading with slipping is simulated and the damage to the knife is reproduced, which is close to the operational one: wear and an increase in the cutting edge radius. Using the developed technique, comparative accelerated tests of imported steel and domestic cast iron (produced by OJSC “Gomselmash”) knives made using various technologies were carried out. The tests conducted made it possible to quantify the difference in the service characteristics of the cutting drum knives made using various technologies, which confirms its usefulness and efficiency. The developed technique was approved in accordance with the established procedure and is used for bench testing of knives at OJSC “Gomselmash”.

Monitoring Shearing-Plowing Transitions in Micro-Milling Using Fluctuations in Cutting Forces

Abstract In micromilling, understanding transitions between the desired shearing-dominant to the undesired plowing-dominant cutting mechanism could help obtain high quality microfeatures. This work investigates the transitions in cutting mechanisms in micromilling using fluctuations in cutting force signals, characterized by using a fluctuation parameter. A new analytical model correlating fluctuation in force signals to the transitions in cutting mechanism has been developed. Two types of slot milling experiments were performed to understand the transitions in cutting mechanisms, as a function of processing parameters, and over the entire life of micro-endmills. The proposed model was found to agree with experimental values of forces within 15% error. The limiting value of the fluctuation parameter has been estimated as 0.01, which corresponds to a limiting feed of 1 μm/tooth. Feed per tooth and cutting edge radius are the important parameters that affect transitions in cutting mechanisms. The cutting mechanism changes from shearing to plowing and vice-versa over the entire life of the tool. Shearing-dominant mechanism prevailed in the first region due to the sharper cutting edges with radius less than 9 μm. Though plowing-dominant cutting mechanism prevails in the remaining two regions, the mechanism comes closer to shearing-dominant near the end of tool life. This is primarily because of the generation of localized sharpness on tool cutting edges due to chipping. Furthermore, it was evident that cutting mechanism changes from shearing to plowing due to wear, when surface roughness increases above 400 nm Ra.

Multi-objective Optimization of Turning Tool Geometric Parameters Based on Kriging Model

Cutting performance parameters of turning tool in different geometric parameters are obtained using finite element model, and the Kriging models of cutting stress and temperature are constructed, taking the cutting performance parameters as training samples. The multi-objective optimization model of turning tool geometric parameters is established based on the constructed cutting performance Kriging models, in which the design variables are rake angle, relief angle and cutting-edge radius, the objective parameters are cutting stress and temperature. The multi-island genetic algorithm is used to obtain the optimum turning tool geometric parameters: rake angle γo is 10.59°, relief angle λs is 6.15°and cutting-edge radius γE is 0.73mm. The simulation results after optimization demonstrate that the corresponding cutting temperature reduces 263.1°C, cutting stress drops by 550.8MPa.

Prediction of Nonlinear Micro-Milling Force with a Novel Minimum Uncut Chip Thickness Model.

The minimum uncut chip thickness (MUCT), dividing the cutting zone into the shear region and the ploughing region, has a strong nonlinear effect on the cutting force of micro-milling. Determining the MUCT value is fundamental in order to predict the micro-milling force. In this study, based on the assumption that the normal shear force and the normal ploughing force are equivalent at the MUCT point, a novel analytical MUCT model considering the comprehensive effect of shear stress, friction angle, ploughing coefficient and cutting-edge radius is constructed to determine the MUCT. Nonlinear piecewise cutting force coefficient functions with the novel MUCT as the break point are constructed to represent the distribution of the shear/ploughing force under the effect of the minimum uncut chip thickness. By integrating the cutting force coefficient function, the nonlinear micro-milling force is predicted. Theoretical analysis shows that the nonlinear cutting force coefficient function embedded with the novel MUCT is absolutely integrable, making the micro-milling force model more stable and accurate than the conventional models. Moreover, by considering different factors in the MUCT model, the proposed micro-milling force model is more flexible than the traditional models. Micro-milling experiments under different cutting conditions have verified the efficiency and improvement of the proposed micro-milling force model.

Effect of cutting edge geometry change due to tool wear on hole quality in drilling of carbon fiber reinforced plastics using advanced ceramic coated tools

This paper aims to study the evolution of cutting edge geometry due to tool wear and discuss its impact on the hole quality of a carbon fiber reinforced plastic (CFRP) laminate. A drilling experiment was conducted using three types of twist drills: uncoated, BAM (AlMgB14) coated, and (AlCrSi/Ti)N nanocomposite coated tungsten carbide tools. After generating 120 holes, the uncoated drill had the largest cutting edge radius (∼36 µm), while the BAM coated drill had the most extensive flank wear (∼287 µm) among the three drills. This relatively rapid tool wear results in a reduction of average hole size and a considerable variation on the hole profiles. The worn drills with the cutting edge radius greater than 19.3 µm form the fiber pull-outs in not only the 135° plies but also the adjacent 45° and 90° plies from the cutting direction, creating deep void networks. This type of networked fiber pull-out damage was observed with the holes machined by the uncoated and BAM coated drills. The (AlCrSi/Ti)N coated drill, which experienced the least amount of flank wear and the least increase of cutting edge radius, generated consistently sized holes up to 120 holes. However, the relatively sharp (AlCrSi/Ti)N coated tool results in the higher arithmetic roughness average (Ra) and the maximum roughness height (Rz) values than the other tools due to the localized fiber pull-outs and the absence of severe matrix smearing.

Multi-scale numerical analysis and experimental verification for nano-cutting

The development of numerical models applicable to ultra-precision machining presents serious challenges. Molecular dynamics methods can effectively capture nano-cutting operations at the micro-nanoscale but fail to accurately capture the realistically large-scale deformations involved in material removal, while it can be addressed by finite element methods but lacks the precision required for modeling nanoscale behaviors. The present study addresses this issue by developing a multi-scale numerical modeling method, the optimized Quasicontinuum (QC) method. Compared with the original QC method, the optimized QC method adds the material removal function, avoids unreasonable lattice excessive distortion and large-area, deep dislocation slip. The optimized QC method can more truly simulate the large deformation and material removal phenomenon of cutting, and greatly improve the calculation speed. The influence of cutting parameters such as cutting depth, tool rake angle and rounded tool cutting edge radius on cutting force is studied. The change of cutting depth has the most significant influence on cutting force, while the influence of tool rake angle and rounded tool cutting edge radius are relatively small. Therefore, the effect of cutting depth on cutting force is studied through the experiment of single crystal copper nano-cutting to verify the effectiveness of multi-scale method. The experimental results show that it is proportional to the simulation results.

Experimental Investigation and Numerical Prediction of the Effects of Cutting Tool Geometry During Turning of AISI 316L Steel

In this work, a numerical and an experimental study aimed to gain a better understanding of the impact of tool geometry such as (rake angle and cutting edge radius) on the temperature distribution and residual stresses in machining surface of AISI 316L stainless steel have been presented. To evaluate the experimental results, various experimental equipment was used, such as a conventional lathe to carry out the machining operations, the cutting force was measured using a Kistler dynamometer and X-ray diffraction technique was employed for determination of the residual stresses distribution on the machined surfaces. In addition, A thermo-mechanically coupled finite element (FE) analysis for cutting process is developed through ABAQUS code to predict the temperature distribution and residual stresses using an Arbitrary Lagrangian-Eulerian (ALE) approach. An inverse identification method has been used to determine the adequate Johnson-Cook (JC) material model parameters to obtain a good correlation between the cutting force measurements and numerical one. The FE model was then validated by comparison of the numerical results of residual stresses with experimental measurements for different tool geometries, which revealed a reasonable agreement.

Evaluation of Ball End Micromilling for Ti6Al4V ELI Microneedles Using a Nanoadditive Under MQL Condition

The use of nanoadditives in lubricants has gained much attention to the research community due to the enhancement of tribological properties and cooling capabilities. This paper studies the advantages of using a MQL (Minimum Quantity of Lubrication) system and nanoadditive in the manufacture of microneedle arrays in Ti6Al4V ELI alloy. Tungsten carbide ball nose tools with a cutting diameter of 200 µm were used in experimental tests. Surface and dimensional characterization was performed to evaluate the impact of a nanoadditive to a vegetable-based oil. Additionally, cutting forces and cutting edge radius (CER) were measured while needles were machined. Experimental tests confirmed that micro end milling with nanoadditives provide slightly better dimensional features and low cutting forces compared to oil. The performance of nanoadditives resulted in a reduction of surface roughness (~ 0.3 μm). Qualitative study of microneedles illustrated burr formation on needle surface manufactured without a nanoadditive solution. Results reveal an increment of CER using low feed rate values (2.0 µm/flute) while a reduction of CER was observed with feed rates up to 2.5 µm/flute. Our results indicated that the addition of nanoadditives to vegetable oil promotes a better product surface topography and cutting tool performance.

Turning-induced surface integrity for a fillet radius in a 316L austenitic stainless steel

Turning is a machining process extensively applied to produce revolution parts. Durability of these parts are known to depend on the turning process signature that is often referred as surface integrity. The surface integrity generated in a fillet radius has been barely studied in the literature so far, despite the well-known geometrical stress concentration factor of such singularities. Therefore this paper deals with the investigation of machining-induced surface integrity when turning a fillet radius in a 316L austenitic stainless steel. Different characterization methods are used for that purpose - SEM, EBSD, nanoindentation and X-Ray diffraction. It points out that the turning-induced consequences are not homogeneous along the machined profile. Residual stresses are strongly affected and microstructure is highly modified over a depth of 80 μm that leads to a mechanical properties gradient. It is evidenced that the average uncut chip thickness is the main governing parameter regarding surface integrity. It is also reported that deformation twins appear in the affected zone. It highlights that turning-induced microstructure evolution at a given depth is rather a consequence of severe plastic deformation at high strain rate than dynamic recrystallization. • For the first time, turning-induced surface integrity in 316L is studied along a fillet radius. • Turning-induced affected depth depends on angular position in the fillet radius. • Affected depth is twice larger for longitudinal turning than for face turning. • Microstructure evolution is correlated with average uncut chip thickness parameter and cutting edge radius. • Severe plastic deformation at room temperature or/and high strain rate governs microstructural evolution (deformation twins).

Effects of cutting edge radius in vibration assisted micro machining

It is important for vibration-assisted machining (VAM) to incorporate the cutting edge radius (re) at microscale machining to understand the tool-workpiece contact relationship and the underlying cutting mechanism. re is absent so far in the analysis of VAM conducted by various researchers. It is difficult to understand the tool edge contact mechanism with the workpiece at microscale cutting simply by theoretical or mathematical analysis. Hence, the contact phenomenon for both 1D and 2D VAM has been investigated through finite element (FE) simulation using the Coupled Eulerian-Lagrangian (CEL) approach. Practical experiments with varying re are conducted to verify the observations. The chip thickness increases in 1D VAM with increased re which remains unchanged in 2D VAM. Although the cutting force increases at a different rate for both 1D and 2D VAM, the thrust force is significantly higher in 2D VAM. Ploughing increases significantly in 2D VAM than 1D VAM. The workpiece surface improves in 2D VAM whereas the change is very little in 1D VAM. The experimental findings with varying re support the FE simulation model of contact relationship and evaluate the cutting performance with re in both 1D and 2D VAM.

Influence of Cutting Parameters on the Surface Quality of High Volume Fraction SiCp/Al2024 Composite

This paper studies the milling process of SiCp/Al2024 composite with high volume fraction and large particle size. The milling mechanism of SiCp/Al2024 composite is analyzed. The influence of cutting depth and feed per tooth on surface quality is analyzed. It reveals the influence of the feed per tooth on the subsurface damage of the workpiece. The results show that in the milling process of high volume fraction SiCp/Al2024 composite, because the cutting edge radius is much larger than the particle radius, the main form of particle removal is crushing. The surface defects of the workpiece mainly include pits, cracks, scratches and indentations. Appropriately increasing the depth of cut can improve the surface quality of the workpiece. The increase in feed per tooth will result in increased surface defects of the workpiece and deterioration of surface quality. When the feed per tooth increases from 4 μm to 8 μm, the thickness of the subsurface damage layer of the workpiece increases from 47.7 to 60.5 μm. The ratio between the minimum cutting thickness of the SiCp/Al2024 composite and the radius of the blunt circle should be less than 8%.

Change in Edge Radius of Cutting Tool from Surface Tension Between Solid Materials

In this study, the “surface tension defined from stress” was used to predict the change in the cutting edge radius in the tool’s initial-stage wear regime. An analysis of the “surface tension defined from the stress” between solids showed that the flow of the material and the adhesion phenomenon must occur simultaneously at the interface. From the experimental and simulation results, it was confirmed that the proposed model can be used to predict the stress distribution acting on the cutting tool and evaluate the “surface tension defined from the stress” at the tool and workpiece interface. It was also verified that the cutting-edge radius under a state of equilibrium changes based on the cutting condition. These results indicate that simply using a cutting tool with a smaller cutting-edge radius will lead to a rapid increase in the cutting-edge retreat at the beginning of the cutting. For the unmanned operation of the cutting processes, it is desirable to use a cutting tool with a cutting-edge radius under a state of equilibrium at the beginning of the cutting to improve the cutting efficiency and reduce the cutting cost.

Damage formation mechanisms of sintered silicon carbide during single-diamond grinding

In this research, a single-diamond grinding test was performed on sintered silicon carbide (SSiC) to explore the damage formation mechanism. A scanning electron microscope and a transmission electron microscope (TEM) were used to examine the surface and subsurface morphologies of the grinding groove, respectively. The characteristics of the ground surface morphologies reveal that the single-diamond grinding process of SSiC can be classified into purely ductile, primarily ductile, primarily brittle, and purely brittle stages. Based on the high-resolution TEM (HRTEM) images and the corresponding Fast Fourier transform images of the near-surface region, results reveal that the high density of dislocations and amorphization of SiC grains are responsible for the plastic deformation of SSiC. Most of the cracks congregate on the top grains of the ground surface due to the distinct obstruction of the grain boundary on the cracks propagation, and the cracks generated at the grain boundaries emit into the top grain interiors and go up toward the exposed surface for the distortedly deformed region with higher strain energy; Furthermore, stress concentration caused by the dislocation pileups at grain boundaries represents the crack initiation mechanisms for SSiC. Finally, based on the dislocations pile-up theory, a critical undeformed chip thickness model for boundary crack system nucleation is established, which considers the cutting-edge radius, grinding wheel speed, material properties, and grain size of ceramics.

Feasibility of Cobalt-Free Nanostructured WC Cutting Inserts for Machining of a TiC/Fe Composite.

The paper presents results of investigations on the binderless nanostructured tungsten carbide (WC) cutting tools fabrication and performance. The scientific novelty includes the description of some regularities of the powder consolidation under electric current and the subsequent possibility to utilize them for practical use in the fabrication of cutting tools. The sintering process of WC nanopowder was performed with the electroconsolidation method, which is a modification of spark plasma sintering (SPS). Its advantages include low temperatures and short sintering time which allows retaining nanosize grains of ca. 70 nm, close to the original particle size of the starting powder. In respect to the application of the cutting tools, pure WC nanostructure resulted in a smaller cutting edge radius providing a higher quality of TiC/Fe machined surface. In the range of cutting speeds, vc = 15–40 m/min the durability of the inserts was 75% of that achieved by cubic boron nitride ones, and more than two times better than that of WC-Co cutting tools. In additional tests of machining 13CrMo4 material at an elevated cutting speed of vc = 100 m/min, binderless nWC inserts worked almost three times longer than WC-Co composites.

The effect of mesh parameters on computational cost and results in simulation of milling in Inconel 718

The Finite Element Method analysis of machining processes has become a ubiquitous feature to the area, however, there sometimes occur considerable deviations between experimental and simulated results due to the inherent complexity of the process. The basis for such may conceivably be related to imprecisions in the material and friction modelling, besides improper setup of mesh parameters. Elements should be small enough to allow for the proper representation of the chip formation, but taking into account that the computational time increases accordingly with mesh downsizing. Simulations of the milling process of Inconel 718 were conducted using the software Thirdwave AdvantEdge under different cutting conditions for three different meshes. Power and temperature output were compared to experimental results, most of which were measured via Hall-effect sensors and thermographic camera, respectively. The tool cutting edge radius was found to be an important factor and was estimated using Scanning Electron Microscope images. The influence of the finite element mesh size was higher for harsher cutting conditions, with effects felt on machining power only. In this case, finer mesh produced results that showed a higher agreement with experimental data, but at higher computational cost as shown by analysis of elapsed processing time. Although errors higher than 40% were observed, power and temperature trends from simulations were always in accordance with that found in experimental tests. Comparisons with experimental data from other studies showed the errors tend to grow for higher feed and cutting speed, which indicates the constitutive model of the material is more adequate for softer machining conditions. Simulation time seemed to be exponentially proportional to the inverse of minimum element size, and measured values might serve as a reference for other users.

Study of temperature and stresses using finite element analysis in turning of C45 material

Parts machined by high cutting speeds can often exhibit high fatigue strength, increased micro-hardness in the surface layers and plastic deformations, due to the tool cutting edge radius associated with the induced stresses. The changing of rake and clearance angles has an important influence on the chip formation, cutting forces, residual stresses, temperatures in both the workpiece and the tool. International research on the influence of geometric parameters of the tool on the entire cutting process, are of particular importance to understand this process development. The approach of this study, considers the parametric realization of the cutting tool profile - a coated TiC turning chisel, which will be used in the finite element simulation of the orthogonal turning process. Deform 2D application, which is a powerful simulation engine was chosen and allows the correct simulation of the cutting process in real machining conditions. Deform 2D enables the automatically meshing and remeshing generation and also the optimization whenever needed and wherever is required a high accuracy, thereby reducing the overall difficulty of the problem and the computational requirements. Using Lagrangian discretization, the machining process was simulated and made possible to observe and present a series of conclusions and own points of view regarding the temperature distribution at the tool tip and in the workpiece, the effective stresses distribution and the cutting force variation under the rake and clearance angles influences.

FE analysis of the effects of process representations on the prediction of residual stresses and chip morphology in the down-milling of Ti6Al4V

Abstract In part II of these two-part papers, the effects of four FEM representations of the milling process on the prediction of chip morphology and residual stresses (RS) are investigated. Part II focuses on the milling of conventional uncut chip thickness h with finite cutting edge radius and flank wear, while part I of these two-part papers has reported on the results in the case of milling small uncut chip thickness in the micrometre range with finite cutting edge radius. Two geometric models of the flank-wear land composed of flat and curved wear land are proposed and assessed. The four process representations are: i) orthogonal cutting with flat wear land and with the mean uncut chip thickness h ¯; ii) orthogonal cutting with flat wear land and with variable h, which characterises the down-milling process and which is imposed on a flat surface of the final workpiece; iii) modelling the true kinematics of the down milling process with flat wear land and iv) modelling the true kinematics of the down milling process with curved wear land. They are designated as Cte-h, Var-h, True-h and True-h*. The effectiveness of these representations is assessed when milling Ti6Al4V with a flank-wear land of VB = 200µm.

FE analysis of the effects of process representations on the prediction of residual stresses and chip morphology in the down-milling of Ti6Al4V

Abstract Part I of these two-part papers will investigate the effect of three FEM representations of the milling process on the prediction of chip morphology and residual stresses (RS), when down-milling small uncut chips with thickness in the micrometer range and finite cutting edge radius. They are: i) orthogonal cutting with the mean uncut chip thickness t, obtained by averaging the uncut chip thickness over the cutting length, ii) orthogonal cutting with variable t, which characterizes the down-milling process and which is imposed on a flat surface of the final workpiece, and iii) modelling the true kinematics of the down milling process. The appropriate constitutive model is identified through 2D FEM investigation of the effects of selected constitutive equations and failure models on the prediction of RS and chip morphology in the dry orthogonal machining of Ti6Al4V and comparison to experimental measurements. The chip morphology and RS prediction capability of these representations is assessed using the available set of experimental data. Models featuring variable chip thickness have revealed the transition from continuous chip formation to the rubbing mode and have improved the predictions of residual stresses. The use of sequential cuts is necessary to converge toward experimental data.

Investigation on the size effect in micro end milling considering the cutting edge radius and the workpiece material

Abstract. Previous research has found that the peripheral and end cutting edges of the cutter had different cutting mechanisms in the micro end cutting process considering the size effect. This investigation is a further study on this point considering the cutting edge radius of the cutter and the material of the workpiece based on the methods of finite element simulation and the micro end cutting experiment. This study adopts a combination of simulation and experiment research methods and the cutting edge radius and the workpiece material as two variables. Considering the cutting mechanisms of the peripheral cutting edge and the end cutting edge are different, the peripheral cutting edge and the end cutting edge are studied respectively. Meanwhile, the minimum undeformed chip thickness (MUCT) value is determined in three ways, chip morphology, cutting force, and surface roughness, so the final result obtained by comparing three kinds of results has a very important reference value. Not only are the chip morphology obtained by finite element simulation and the surface roughness obtained by the micro end cutting experiment used to identify the MUCT value, but also the cutting force. The simulation and experimental results show that the cutting force can be used to identify the MUCT value for the peripheral cutting edge, but it cannot be used for the end cutting edge. The MUCT value increases with the increase of the cutting edge radius, no matter which process it is. The material property has some effects on the MUCT value; even the cutting parameters and the cutting edge radius remain unchanged for the peripheral cutting edge. However, the material property has no effect on the MUCT value for the end cutting edge. In this study, the influence of important variables on MUCT is studied as much as possible to reflect a real application situation.

Analytical prediction of cutting tool temperature distribution in orthogonal cutting including third deformation zone

The present study introduces a novel model for the prediction of temperature in a cutting tool while the effects of all three deformation zones are considered. The model considers the effect of cutting-edge radius and the third deformation zone for the first time in the literature in terms of temperature prediction using thermo-mechanical approach with dual-zone friction model. The material behavior is defined by the Johnson-Cook constitutive model. For the calculation of heat flux on the rake and flank faces, a dual-zone model was used. The temperature distributions at the tool-chip and tool-workpiece boundaries were determined analytically, and the temperature distribution inside the tool was calculated using the Finite Difference Method. In order to verify the model, experiments were performed with AISI1050 steel and Al7075 workpiece materials using tungsten-carbide cutting tools. A good agreement is observed between the model predictions and the test results. This study also examined the effects of cutting-edge geometry and cutting conditions on cutting temperature, which can be used in optimized selection of cutting parameters and tool geometry.