Rake Face Temperature Research Articles

Analytical model of modified diamond tools temperature by focused ion beam in dry diamond turning

The contact process between the chip and the rake face is directly affected by the temperature of the rake face, and then tool wear and machining quality is indirectly influenced by it. In this study, a temperature prediction model for the rake face of modified diamond tools during dry turning of the 6061 aluminum alloy was established based on the moving heat source method. The shear heat source, rake face chip friction heat source, cutting edge-workpiece ploughing effect heat source, cutting edge workpiece roll burnishing heat source, and flank face workpiece elastic recovery heat source were considered by this model during the dry diamond turning, simultaneously considering the non-uniformity of heat source intensity and heat distribution ratio, as well as the influence of ion implantation on the temperature of the tool rake face. The experimental results indicate that this model successfully predicts the temperature of the modified tool rake face, and it is found that an increase in dose will promote a decrease in the temperature of the rake face. Theoretical analysis reveals that modified cutting tools have the characteristic of reducing the temperature of the rake face, revealing the essence of the influence of “modification” on the temperature of the rake face from the perspective of the cutting mechanism, and providing a theoretical basis for optimizing modification parameters.

Comparison of the performance of the internally cooled tool in closed circuit against standard PCBN tools in turning AISI D6 hardened

Machining is a widely used manufacturing process that involves removing material from a workpiece. During this process, more than 95 % of the mechanical energy from the machine tool's electrical motor is converted into heat. This can cause the cutting tool's temperature to soar to extremely high levels, reaching up to 1200 °C or even higher, especially when working with hardened steels. To cool down the machining region, cutting fluids are commonly employed in industries. However, these fluids are not considered sustainable because they pose environmental pollution risks, are costly, challenging to dispose of properly, and can also be hazardous to operators' health. Moreover, in some applications, cutting fluids are not recommended. Considering these issues, this research aims to propose and test a more sustainable approach. The method involves using a closed-circuit system where a mixture of water and ethylene glycol circulates internally in polycrystalline cubic boron nitride (PCBN) tools. These tools are employed in the turning operation of AISI D6 hardened steel and are compared with conventional dry machining. The study utilizes a design of experiment (DOE) and analysis of variance (ANOVA) to plan and analyze the results with statistical reliability. Key output variables considered include cutting temperature, tool life, cutting forces, and surface roughness. The implementation of the internally cooled tool (ICT) system has shown significant benefits. It notably reduces the temperature of the tool's rake face, as measured using a thermographic camera. Despite not being the main variable affecting the maximum temperature, the cooling system plays a crucial role in achieving these improvements. The ICT system also substantially increases the tool life in comparison to conventional dry machining across all tested cutting conditions. While the feed rate remains the most influential factor affecting cutting forces due to increased cutting area, the cooling system also plays a significant role. The ICT system, with reduced temperatures, performs better in this regard. As for surface roughness, the condition of the tool edge emerges as the sole significant factor. Surprisingly, the worn tool provides better surface finishing due to the presence of crater wear. With conventional dry machining, higher cutting temperatures lead to increased tool wear, primarily caused by abrasion and attrition.

Research on cutting temperature distribution of carbide cutter rake face considering sticking-welding layer

In the process of cutting 2.25Cr1Mo0.25V material with carbide cutter, the cutter-chip element diffusion occurs, which will cause sticking-welding layer easily produced on rake surface. In order to study the influence of the sticking-welding layer on the temperature distribution and gradient of rake face, the thermal conductivity of sticking-welding layer on rake face was calculated by using the Maxwell-Eucken diffusion phase continuum principle. According to the heat conduction theory, the theoretical model of heat transfer with or without the sticking-welding layer on rake face was established, and combined with the finite element simulation model, the temperature distribution of rake face is studied by combining model calculation and numerical simulation. The results show that: when there is sticking-welding layer on rake face of cutter, this specified layer will play the role of heat insulation, leading to relatively low temperature of rake face. The presence of sticking-welding layer will cause the temperature fluctuation of cutter rake face, and the temperature also increases with the increase of the thickness. At the same time, the variation trend of temperature gradient in sticking-welding layer is similar with different layer thickness, whereas the larger the thickness, the greater the variation of temperature gradient due to the thermal resistance. By comparing and analyzing the average cutting temperature of rake face of the actual cutting and simulation, it is concluded that the temperature simulated by the finite element model will be closer to the actual measured temperature, and the measurement error is less than 10%, which provides a theoretical basis for delaying the tool life.

A simulation-based analysis on the cooling effect and the tool temperature distribution in modulated turning (MT)

Modulation assistance is widely used for breaking chips of highly ductile materials in turning. This process is also known as the “modulated turning” (MT) or the “modulation assisted machining (MAM)”. The process transforms continuous single point turning into an intermittent cutting process where the tool tip briefly disengages from the workpiece generating discrete short chips. Resembling the milling process mechanics, periodic tool disengagements in modulated turning introduces cyclic cool-down periods and thus it can potentially attenuate tool-tip temperatures. It has been hypothesized that this effect can greatly lower maximum and the average tool-tip temperatures improving wear resistance of the process. This paper presents a thermal model to predict the tool-tip temperature distribution in modulated turning. A generalized chip formation formulation is first developed to predict the uncut chip thickness variation, cutting forces and the tool engagement/disengagement phase durations. Thermomechanical behavior of tool-chip contact is then modeled to predict the rake face temperature distribution. Simulation studies are presented to analyze the temperature distribution and understand peak temperature (hot) spots on the rake face. It has shown that the phase angle parameter – the frequency ratio between workpiece rotation and tool modulation– of MT plays a key role in controlling the hot spots on the rake and can be used as a tool to influence the wear regime.

Thermomechanical Simulation of Orthogonal Metal Cutting with PFEM and SPH Using a Temperature-Dependent Friction Coefficient: A Comparative Study.

In this work, we apply the Particle Finite Element Method (PFEM) and Smoothed Particle Hydrodynamics (SPH) to simulate the orthogonal cutting chip formation of two workpiece materials, i.e., AISI 1045 steel and Ti6Al4V titanium alloy. A modified Johnson-Cook constitutive model is used to model the plastic behavior of the two workpiece materials. No damage or strain softening is included in the model. The friction between the workpiece and the tool is modeled following Coulomb's law with a temperature-dependent coefficient. The accuracy of PFEM and SPH in predicting thermomechanical loads at various cutting speeds and depths against the experimental data are compared. The results show that both numerical methods can predict the rake face temperature of AISI 1045 with errors less than 34%. For Ti6Al4V, however, the temperature prediction errors are significantly higher than those of the steel alloy. Errors in force prediction were in the range of 10% to 76% for both methods, which compare very well with those reported in the literature. This investigation infers that the Ti6Al4V behavior under machining conditions is difficult to model on the cutting scale irrespective of the choice of numerical method.

Analytical and experimental investigations of rake face temperature considering temperature-dependent thermal properties

In metal cutting, rake face temperature is a critical factor affecting the quality of processed parts and tool wear. However, this temperature is difficult to estimate because of the high strain rate and barrier effect of chips. This paper presents an integrated analytical and experimental approach to predict rake face temperature, which proposes an improved analytical model considering temperature-dependent thermal properties. The considered temperature properties mainly include thermal conductivity (TC) and thermal diffusivity (TD) of the workpiece and cutting tool, which has rarely been considered in previous studies. With the measured cutting force and tool–chip contact length, the improved analytical model can predict the tool temperature based on an adaptive method to match the thermal properties and temperature at an arbitrary point. Moreover, a relatively new in situ measurement method for directly capturing the radiation of the rake face temperature using a two-colour pyrometer and slotted workpiece is presented. This new technique can eliminate the barrier effect of the chip without interrupting the cutting process. This experimental method is proved to be able to stably measure the rake face temperature with a deviation less than 3%, furthermore, the captured temperatures are much higher when compared with conventional methods under the comparable cutting conditions. The comparison of rake face temperature between the predicted and the measured results shows an average prediction error of 8.6% of the proposed method, proving its superiority over conventional models using constant thermal properties.

The relationship between adhesion morphology and cutting force in orthogonal cutting of 6061-T6 aluminum alloy

Due to the sticky and soft characteristics of aluminum alloy, it is easy to form adhesion on the tool rake face during cutting process. In this work, the orthogonal cutting tests for 6061-T6 aluminum were carried out at cutting speeds of 20–300 m/min and feed rates of 0.05–0.3 mm, and the relationship between adhesion and cutting force has been explored. A slip-line model was used to separate the edge force of cutting edge to obtain the pure friction force of tool rake face, thereby obtaining the average friction coefficient. Adhesion morphologies were observed under the scanning electron microscope (SEM) and compared with the average friction coefficients. It was found that different adhesion morphologies correspond to different friction coefficient ranges. Simultaneously, the relationship between the temperature and normal stress on the tool rake face and the adhesion morphology and friction coefficient was investigated. The results showed that the temperature is the major factor of adhesion evolution and friction coefficient change. Combining the tool rake face temperature and the adhesion morphology, it was noted that the reduction of the friction coefficient is not only owing to the self-lubrication caused by thermal softening, but also due to the decrease of the total shear force caused by the incomplete contact. Finally, the relationship between the friction coefficient of tool rake face and the cutting force and specific cutting energy was discussed, with the conclusion that the friction coefficient has an impact on the cutting force and specific cutting energy by changing the shear angle.

A Numerical-Experimental Study on Orthogonal Cutting of AISI 1045 Steel and Ti6Al4V Alloy: SPH and FEM Modeling with Newly Identified Friction Coefficients

Numerical simulation of metal cutting with rigorous experimental validation is a profitable approach that facilitates process optimization and better productivity. In this work, we apply the Smoothed Particle Hydrodynamics (SPH) and Finite Element Method (FEM) to simulate the chip formation process within a thermo-mechanically coupled framework. A series of cutting experiments on two widely-used workpiece materials, i.e., AISI 1045 steel and Ti6Al4V titanium alloy, is conducted for validation purposes. Furthermore, we present a novel technique to measure the rake face temperature without manipulating the chip flow within the experimental framework, which offers a new quality of the experimental validation of thermal loads in orthogonal metal cutting. All material parameters and friction coefficients are identified in-situ, proposing new values for temperature-dependent and velocity-dependent friction coefficients of AISI 1045 and Ti6Al4V under the cutting conditions. Simulation results show that the choice of friction coefficient has a higher impact on SPH forces than FEM. Average errors of force prediction for SPH and FEM were in the range of 33% and 23%, respectively. Except for the rake face temperature of Ti6Al4V, both SPH and FEM provide accurate predictions of thermal loads with 5–20% error.

Approach for multiscale modeling the thermomechanical tool load in gear hobbing

In this report, an approach is presented how a geometric penetration calculation can be combined with FE simulations to a multiscale model, which allows an efficient determination of the thermomechanical load in gear hobbing. FE simulations of the linear-orthogonal cut are used to derive approximate equations for calculating the cutting force and the rake face temperature. The hobbing process is then simulated with a geometric penetration calculation and uncut chip geometries are determined for each generating position. The uncut chip geometries serve as input variables for the derived equations, which are solved at each point of the cutting edge for each generating position. The cutting force is scaled according to the established procedure of discrete addition of the forces along the cutting edge over all individual cross-section elements. For the calculation of the temperature, an approach is presented how to consider a variable chip thickness profile. Based on this, the temperature distribution on the rake face is calculated. The model is verified on the one hand by cutting force measurements in machining trials and on the other hand by an FE simulation of a full engagement of a hob tooth.

Temperature calculation of the tool and chip in slicing process with equal-rake angle arc-tooth slice tool

As a new gear processing technology, gear slicing technology has the characteristics of high efficiency, high precision and environmental protection. In this paper, the slicing process with equal-rake angle arc-tooth slice tool (ERA-ATST) is taken as the research object. Considering the particularity of the slicing process, a theoretical calculation method of tool and chip temperature is proposed. By analyzing the characteristics of the slicing process with ERA-ATST, a cutter tooth of the ERA-ATST is divided into several sections along the cutting edge, which are called micro-section tooth. For each of the micro-section tooth, the slicing process is simplified and equivalent to oblique cutting process. Comprehensively considering the influence of cutting speed, chip force and tool-chip contacting characteristics in slicing process, a temperature calculation model is established based on the generation mechanism of slicing heat. The tool and chip temperature is derived by averaging the results of several micro-section teeth. With the established model, an inner arc-spur gear slicing with the ERA-ATST is used as an example to calculate the temperature on the chip and rake face. The gear slicing test is carried out on the slicing machine tool. The measured chip temperature and rake face temperature are compared with the corresponding calculation results to verify the temperature calculation model. The proposed temperature calculation method provides a theoretical basis for the analysis and control of slicing heat in the gear slicing process.

In-situ measurement of rake face temperatures in orthogonal cutting

In machining, the thermal load significantly influences the tool wear and the workpiece quality, thus limiting the productivity. Therefore, a new experimental setup for the high-speed measurement of the rake face temperature in orthogonal cutting without substantially affecting the chip formation was developed. The investigations focus on the influence of different rake face preparation methods and cutting parameters on the temperature of the rake face, measured in the immediate vicinity of the cutting edge. The presented results significantly improve the understanding of the process and provide new insights for the tool development and the validation of cutting models.

Experimental study on the formation of TCR and thermal behavior of hard machining using TiAlN coated tools

Thermal contact resistance (TCR) is formatted at tool-chip interface during metal cutting process, which will influence on cutting temperature distribution. This study analyzed the formation mechanism of TCR in initial and stable stages in H13 hardened steel cutting process. Dry orthogonal cutting experiments were carried out with TiAlN coated tools. The cutting temperatures at the tool-chip contact zone and tool substrate were investigated. Scanning electron microscope (SEM) and energy dispersive spectrometry (EDS) were used to characterize the tool rake face and fracture cross-sectional morphology of TiAlN coated tool. By analyzing the experimental results, the TCR was caused by original defects of TiAlN coating such as particles and pits in the initial cutting stage. In the stable cutting stage, the TCR was generated by the Al2O3 oxide layer and the uneven adhesion of the chip material on tool rake face. A finite element (FE) model based on Arbitrary-Lagrangian-Eulerian (ALE) approach was applied to simulate the influence of TCR on cutting process. The FE simulation results indicated that the maximum cutting temperature of the tool rake face decreased with the increase of TCR. On the contrary, the maximum cutting temperature of tool-chip contact area increased with TCR. This proposed formation mechanism of TCR at tool-chip interface was helpful to better understand the cutting heat transfer in machining process.

Determination of emissivity and temperature of tool rake face when cutting AISI 4140

A method for measuring tool temperature in the tool/chip contact zone of the rake face of a tool during dry orthogonal cutting using thermography is presented. This method used a new calibration method that combined with a standard camera calibration allows to estimate surface emissivity. The effect of material deposition and tool oxidation on the emissivity is analyzed. These techniques effectively showed thermal field on the rake face when machining AISI 4140.

Measurement of Rake Face Temperature and Characteristics of Heat Transfer in Cryogenic Machining

Measurement of Rake Face Temperature and Characteristics of Heat Transfer in Cryogenic Machining

Effects of Thermo-physical properties of Ti0.41Al0.59N coating on transient and steady cutting temperature distributions in coated cemented carbide tools

Coated cutting tools have such advantages as high thermal shock resistance, excellent properties of anti-wear and anti-chemical corrosion compared with uncoated ones. However, the role and influence mechanism of coatings on thermal shock resistance and thermal barrier performance of cutting tools have not been clear. Firstly, the effects of Ti0.41Al0.59N coating on the temperature distribution within the rake face area during cutting process are quantitatively analyzed using one-dimensional transient and steady-state models proposed in this paper. The thermo-physical properties of coating and substrate with temperature are considered as varying with tool rake face temperature. The results demonstrate that lower thermal conductivity of the coating material and lower thermal diffusivity of the substrate material will generate instantaneous thermal barrier effect. The effects of Ti0.41Al0.59N coating on the thermal barrier performance and the decrease of internal temperature within the tool body are more remarkable at high temperature. Secondly, the interval time of temperature distribution within cutting tool from the transient state to the steady state is proposed and quantitatively analyzed. The interval time is mainly depended on the thermo-physical properties of the substrate material. It decreases with the increase of the tool substrate thermal conductivity, while increases with the increase of the tool substrate thermal diffusivity. Finally, the simulated experiments of heat transfer for Ti0.41Al0.59N coated cutting tools are designed to verify the numerical results. The research results provide the basis for understanding of the thermal barrier performance of Ti0.41Al0.59N coating as well as the choice of reasonable physical properties for the cutting tool materials.

New calibration method to measure rake face temperature of the tool during dry orthogonal cutting using thermography

A new method for measuring temperature in the rake face of a tool during dry orthogonal cutting using thermography is presented. In addition, a new technique is also used to calibrate the infrared camera. Using this technique, real temperature values from camera response are directly obtained without the need for emissivity correction. Emissivity is thus not an uncertainty source. These techniques were applied to machining AISI 4140. Rake face temperatures are reported and correlation with cutting forces outlined. The set-up effectively showed temperature distribution on the rake face.

Investigation of temperature distribution in orthogonal cutting through dual-zone contact model on the rake face

A two-dimensional analytical model to calculate the temperature distribution in orthogonal cutting with dual-zone contact on the rake face is presented. The study considers heat generation in the primary shear zone and on the rake face. The material behavior in the primary shear zone is represented by Johnson-Cook constitutive equation while the contact on the rake face is modeled by sticking and sliding friction zones. This new temperature distribution model is used to determine the maximum temperature on the rake face and two-dimensional temperature distribution in the chip and on the tool surface. The dual-zone contact model on the rake face and convection boundary condition on the flank face are the important contributions of this work. The simulation results of the developed model are compared with experimental results where a good agreement is demonstrated.

Heat partition and rake face temperature in the machining of H13 steel with coated cutting tools

Lots of heat generated in the cutting deformation zone can cause the temperature rising of cutting tool and workpiece during the cutting process. Tool temperature is mainly depended on the heat energy entering into tool in the secondary deformation zone. Higher working temperature can weaken the cutting tool strength and then deteriorate the tool wear. Advanced coating layer deposited on the tool substrate can change the tool-chip friction and affect the heat partition in the tool-chip interface. In order to reveal the mechanism of heat conduction in the secondary deformation zone, the model of heat partition into cutting tool was built. With the aid of finite element method (FEM), the relative parameters which were necessary for the solving of heat partition model were quantified. Actual cutting experiments were carried out to the verification of the FEM models by means of the cutting force and temperature measurement. Influences of coatings (i.e., coating materials, coating thickness) and cutting speeds on the heat partition were analyzed. And then, rake face temperatures obtained at four kinds of coated tools were compared. The investigation results showed that TiC coating appears as the maximum value and Al2O3 coating appears as the minimum value of heat partition coefficient into cutting tool among these four kinds of coatings (i.e., TiC, TiN, TiAlN, Al2O3). With the increasing of coating thickness and cutting speeds, heat partition into cutting tool all showed a decrease trend. Al2O3-coated tool had the maximum rake face temperature among these four kinds of coated tools; however, the location of peak temperature on the rake face of Al2O3-coated tool was the shortest distance from the tool tip.

Prediction of cutting temperature distributions on rake face of coated cutting tools

Coated cutting tools have been widely employed in metal cutting operations owing to its excellent abrasion resistance and heat transfer performances. Rake face temperature is the primary factor that determines the temperature distribution in the cutting tool body. Based on the heat source theory, a new prediction model is proposed in this paper to forecast the temperature distribution on the rake face. Infrared image is used to develop a new turning experimental apparatus to measure the rake face temperature of coated tool during the cutting process. Rake face temperature measurement results are used to verify the proposed model prediction results of temperature distribution. Several cutting tests are carried out with monolayer coated tools in the machining of H13 hardened steel. The rake face temperature in monolayer coated tool for machining H13 shows an increase trend as the cutting speed increases. The influence parameters including thermo-physical properties and tool/workpiece frictional coefficient of coating material on temperature distribution in coated tools are discussed and illustrated. The research results presented in this paper can help to access the potential of coated tools used in the hardened steel machining.

Rake Face Temperature When Machining with Coated Cutting Tools

Infrared thermography through transparent cutting tools has been used to measure the chip-tool interface temperature. It is of interest to extend this technique to study changes in interface temperature when tool coatings are used. An initial attempt is made here to measure the chip-tool interface temperature distribution when cutting Ti6Al4 V with a TiN coated YAG tool. The TiN coating thickness is kept low at about 100 nm to minimize the temperature difference between the front (chip-TiN interface) and the back (TiN-YAG interface) faces of the coating. The transparency of the YAG tool allows near infrared radiation emitted by the back face of the TiN coating to be imaged. A novel method is used to measure the emissivity of the TiN/YAG interface. Using this method, and the available blackbody calibration of the temperature vs. intensity response of the imaging system, the images are converted into temperature maps. The performance of the coated tool is also evaluated in terms of machining force and tool wear characteristics. Coatings that remain intact during the experiments will reduce ambiguity in interpretation of the results.