Tool-chip Interface Temperature Research Articles

Transient Temperature at Tool-Chip Interface during Initial Period of Chip Formation in Orthogonal Cutting of Inconel 718.

Machining nickel-based super alloys such as Inconel 718 generates a high thermal load induced via friction and plastic deformation, causing these alloys to be among most difficult-to-cut materials. Localized heat generation occurring in machining induces high temperature gradients. Experimental techniques for determining cutting tool temperature are challenging due to the small dimensions of the heat source and the chips produced, making it difficult to observe the tool-chip interface. Therefore, theoretical analysis of cutting temperatures is crucial for understanding heat generation and temperature distribution during cutting operations. Periodic heating and cooling occurring during cutting and interruption, respectively, are modeled using a hybrid analytical and finite element (FE) transient thermal model. In addition to identifying a transition distance associated with initial period of chip formation (IPCF) from apparent coefficient of friction results using a sigmoid function, the transition temperature is also identified using the thermal model. The model is validated experimentally by measuring the tool-chip interface temperature using a two-color pyrometer at a specific cutting distance. Due to the cyclic behavior in interrupted cutting, where a steady-state condition may or may not be achieved, transient thermal modeling is required in this case. Input parameters required to identify the heat flux for the transient thermal model are obtained experimentally and the definitions of heat-flux-reducing factors along the cutting path are associated with interruptions and the repeating IPCF. The thermal model consists of two main parts: one is related to identifying the heat flux, and the other part involves the determination of the temperature field within the tool using a partial differential equation (PDE) solved numerically via a 2D finite element method.

Modification of extended Oxley’s predictive machining theory and determination of Johnson-Cook material model constants by inverse approach

The Johnson-Cook (J-C) flow stress model, renowned for its consideration of the combined effect of strain, strain-rate, and temperature on material property, forms the cornerstone of this research. Its simplicity and applicability in numerical simulation render it widely popular. The study addresses two primary objectives: first, to modify extended Oxley’s predictive machining theory by eliminating the iterative loop for calculating the tool-chip interface temperature, and second, to utilize an inverse approach for determining J-C material model constants specific to medium carbon steel. The modified approach successfully eliminates the iterative loop, thereby streamlining the determination process and effectively reducing calculation time by 25%–40%, thereby enhancing overall efficiency. Concurrently, the study employs an inverse approach to accurately determine the J-C constants (A, B, n, C, and m). Notably, the research avoids the need for expensive and time-consuming Split Hopkinson Pressure Bar (SHPB) tests, instead opting for low-cost axial tensile tests and numerical optimization techniques to obtain the J-C constants. Thus, this study provides a practical method for determining J-C constants, pivotal for accurate material representation in numerical simulations and metal cutting applications. Standard materials and machines are employed, ensuring ease of understanding for a wider audience. The predicted values for the J-C constants are in proximity to the experimental values obtained by using SHPB test. Validated findings, achieved with precision under specified metal cutting conditions, highlight the effectiveness and applicability of the proposed approach, providing valuable insights for optimizing machining processes and improving efficiency.

Improvement of Machinability of Hardened Steel in Turning Operation Using Cryogenically Treated Cutting Tool

Hardened steels need special cutting tools like PCBN and ceramic to be machined. But these cutting tools aren’t cost-effective and require machine tool structures that are stiff and don’t let vibrations through. The current trend is to find other, less expensive ways to make these materials easier to work with. Cryo-treating cutting tools is an effective way to improve the way the tool materials work when they are cut. Cryogenically treated tungsten carbide inserts in dry turning operations were looked at in this study. For hard turning of hardened mild steel (48 HRC), the performance of cryogenically treated Tungsten Carbide (WC) inserts was compared with that of untreated inserts in terms of chip-tool interface temperature and surface roughness under dry cutting conditions. The cutting tool (Untreated and Treated), and cutting speed (375, 512, 706 rpm) were selected as experiment parameters at a constant feed rate of 0.0841mm/rev and depth of cut 1mm. The chip-tool interface temperature analysis results revealed that temperature increases with the increasing cutting velocities. A better surface finish can be found at a higher cutting speed. The lower value of Ra was found at 1.75 μm (without cryogenic treatment) and 1.05 μm (with cryogenic treatment) for cutting speed at 706 rpm.

Internally cooled tools as an innovative solution for sustainable machining: Temperature investigation using Inconel 718 superalloy

Machining is a process that involves intense heat generation at localized points within the tool-chip interface. This leads to elevated temperatures, which can be detrimental to cutting tools. This issue becomes even more crucial when dealing with superalloys like Inconel 718, as they exhibit high shear strength and good creep resistance. Consequently, a significant amount of energy is expended, increasing the cutting temperature. Until now, the primary technique employed to address this issue has been using Cutting Fluids (CFs). In machining, a portion of costs is attributed to fluid handling. It also contains harmful elements that can pose health risks, potentially leading to conditions such as cancer. Moreover, the toxic components can contribute to environmental degradation when improperly disposed of. Therefore, this study proposes an innovative cooling technique called Internally Cooled Tools (ICTs). The ICTs employ an internally circulating coolant fluid through closed cooling channels within the cutting tools, eliminating fluid dispersion into the atmosphere. The main objective was to compare the performance of ICTs in controlling the tool-chip interface temperature during Inconel 718 turning using hard metal tools. For this purpose, a complete factorial experimental design (25) was utilized, with the response variable being the temperature measured by the tool-work thermocouples technique. Beyond that, a sustainable assessment was performed using the Pugh Matrix method. Many key sustainable factors were evaluated related to three atmospheres, cutting fluids in abundance – CFA, dry machining, and ICT. The data base used was a depth literature investigation together with results found in this work. The main findings of this entire work demonstrated that an increase in cutting parameters corresponded to an increase in temperature, as anticipated. TiNAl coating reduced the temperature by up to 10% compared to uncoated tools. Similarly, applying ICTs led to temperature reductions of up to 17% compared to dry machining conditions. The Pugh Matrix made considering 12 factors showed that ICT (14 points) was the most sustainable lubri-cooling method in comparison to CFA (3) and DM (5). Ultimately, ICTs showed to be a promising eco-friendly method. It outperformed conventional methods, showcasing a remarkable heat dissipation capacity. As a result, further studies are warranted to delve deeper into this promising approach.

FE parametric evaluation of macro-to-microscale dry milling for sustainable manufacturing of aerospace alloys

Micro-end-milling of energy-efficient materials has gained prime significance in advanced manufacturing due to their excellent machining characteristics. Numerous experimental and numerical studies have been conducted to establish the optimum parameters of the micro-end-milling process. Because of the complex interaction at the tool-burr interface that involves high material strain rates, this study investigated an extensive parametric sensitivity analysis to evaluate the reliability of numerical simulations. The numerical simulations of AA2024 and Ti6Al4V alloy micro-end-milling are performed in Abaqus/Explicit using the thermo-viscoelastic Johnson-Cook damage model. The parametric sensitivity analysis of both materials is compared, and the burr morphologies are analyzed with changing material characteristics. Tool-burr interface temperature, cutting reaction forces, material plastic strain, and stresses are evaluated to analyze the effect of the change in material characteristics with cutting parameters. Computations are performed at different cutting speeds, tool edge radii, cutting feeds, and contact friction to analyze their effect on chip stress, temperature, material strain, and the tool's thrust force. Feed and contract friction demonstrated pronounced effects on the chip-tool interface temperature compared to the contact friction for both types of materials. The computational results are verified with the experimental data.

The Study of Tool Wear Mechanism Considering the Tool–Chip Interface Temperature during Milling of Aluminum Alloy

ADC12 aluminum alloy has been widely used in the aerospace, ship, and automotive fields because of its high specific strength, excellent die-casting performance, and wear resistance. Adhesion wear is the main wear mechanism of high-speed milling ADC12 aluminum alloy. The most important factor affecting adhesion wear is the tool–chip interface friction, which is directly manifested in the tool–chip interface temperature. Therefore, the temperature variation during the milling of aluminum alloy is analyzed using a temperature field model and infrared temperature measurement technology. Then, the tool wear morphology and the tool wear land width are observed using a scanning electron microscope. Finally, the tool wear mechanism considering the tool–chip interface temperature is discussed. The tool–chip interface temperature is related to the friction angle, tool–chip contact length, and friction force at the rake face, which increases first and then decreases as the cutting speed and feed rate increase. During the formation of the adhesive layer, the tool–chip interface temperature increases, the change rate of the cutting force and the tool wear rate increase, and adhesion, oxidation, and abrasive and delamination wear are generated on the tool surface. With the increase in temperature, the tool wear rate increases, the molten adhesive layer on the tool surface is accompanied by crack propagation, and adhesion wear, oxidation wear, and abrasive wear occur on the tool surface.

An enhanced semi-analytical estimation of tool-chip interface temperature in metal cutting

An accurate estimation of the temperature distribution on tool surfaces is of great industrial importance; without it, a reliable prediction of tool wear in machining, especially thermally-induced wear mechanisms such as dissolution-diffusion and oxidation, is deemed impossible. This has promoted the development of semi-analytical models for simulation of the tool-chip interface temperature, which are less time-intensive and reasonably accurate.This study aims to present an enhanced prediction of the tool-chip interface temperature within the context of the available semi-analytical solutions of the heat conduction-advection problem with a moving heat source. A novel approach is presented to obtain the variable heat flux along the tool-chip interface based on a non-uniform contribution of generated heat in the sticking and sliding zones during chip flow. The capability of the enhanced model to simulate the temperature distribution is demonstrated for machining C45 and C50 plain carbon steels using uncoated carbide tools. The predictions are validated against the results of experimental orthogonal cutting tests for the same cutting conditions. A comparative analysis is then performed to underline the importance of incorporating the variable heat flux for reliable predictions of the maximum interface temperature and its location on the rake face. The outlook for future developments is also highlighted.

Eco-friendly sustainable machining with MoS2-based solid lubricant

Machining is one of the basic and inevitable operations in the manufacturing industry. The machining performance is estimated based on various parameters like cutting forces, surface roughness, tool–chip interface temperature, and specific energy. In the traditional approach, cutting fluids are greatly utilized to dissipate the generated heat during machining, but their utilization causes a threat to nature and human being’s health. Therefore, there emerges a necessity to determine user-friendly, sustainable, and eco-friendly substitutes for traditional cutting fluids. The field of advanced tribology has proposed the usage of solid lubricants due to their inherent properties, such as excellent tribological performance, reduced machining zone temperature due to lowered friction, and enhanced tool life. Therefore, in the present study, pure MoS2 and composite MoS2–TiO2 solid lubricants have been employed in the milling process of AISI 52100 steel with HSS end mill cutter. The machining was carried out in different conditions such as uncoated tool without use of lubricant, uncoated tool with use of lubricant, coated tool without use of lubricant, and coated tool with use of lubricant that were employed to analyze their effect on machining performance. The experimental results showed substantial improvement regarding reduced cutting forces, reduced temperature at tool–chip interface, improved surface finish, and average tool wear with the application of solid lubricants. Among the various lubricating conditions, composite MoS2–TiO2-coated tool with composite MoS2–TiO2 lubricant exhibits excellent machining performance.

Machinability investigation of Chromoly steel using TiN/Al2O3/TiCN/TiOCN multilayer coated tungsten carbide tool inserts with artificial neural network methodology

AbstractEnhancing the machining efficiency of hardened steel using four‐layer coated tungsten carbide tools has gained a lot of interest among manufacturing engineers. This paper reports the machining performance of AISI 4140 steel using TiN/Al2O3/TiCN/TiOCN multilayer coated tungsten carbide tool inserts. The impact of cutting speed, depth of cut, and the nose radius on machining force, tool chip interface temperature, surface roughness, and chip forms was ascertained using full factorial machining experiments and artificial neural network (ANN) methodology. The machining force evaluated using Logistic Sigmoid activation function resulted in the highest root mean square error (RMSE) of 4.076 and regression value of 0.998. The maximum error between the ANN predicted results and experimental results for machining force, cutting temperature and surface roughness was about 2.4%, 5.3%, and 2.07%, respectively. The best architecture for ANN was “3‐6‐4” which had a coefficient of regression value of 0.97. However, in case of chip form, some of the ANN predicted values could not be mapped to ISO standard chip form and hence prediction accuracy of 80% was achieved.

Self-Propelled Rotary Tools in Hard Turning: Analysis and Optimization via Finite Element Models.

This study investigates self-propelled rotary tool (SPRT) performance in hard turning using 3D finite element (FE) models. The FE models developed in this study are based on coupled temperature-displacement analysis using an explicit time-integration scheme. The developed FE models can predict chip morphology, cutting forces, tool and workpiece stresses and temperatures. For model verification, hard turning experiments were conducted using an SPRT on AISI 4340 bars. Cutting forces and maximum tool-chip interface temperatures were recorded and compared with the model findings. The effects of different process parameters were analyzed and discussed using the developed FE models. The FE models were run with a central composite design (CCD-25) matrix with four input variables, i.e., the cutting speed, the feed rate, the depth of the cut and the inclination angle. Response surfaces based on the Gaussian process were generated for each performance variable in order to predict design points not available in the original design of the experiment matrix. An optimization study was carried out to minimize tool stress and temperature while setting limits for the material removal rate (MRR) and specific cutting energy for the process. Optimized processes were found with moderate cutting speeds and feed rates and high depths of cut and inclination angles.

Simulation of the effects of cryogenic liquid nitrogen jets in Ti6Al4V milling

In this research, a 3D Finite Element simulation model of Ti6Al4V milling with internal delivery of liquid nitrogen LN2 was developed to understand the effects of the cryogenic jets on the cutting mechanics. The numerical model was thoroughly validated comparing the simulated forces and chip morphologies with the corresponding experimental findings, obtained in different cutting conditions. In both cryogenic and dry conditions, the numerical results were in strong agreement with the experiments. Maximum errors in the average main force estimation and in the distance between chip serrations resulted to be respectively 13 % and 17.6 %. The developed model predicted the forces along other directions within an average error of 13.8 % on their maximum values and 27.7 % on their mean values. Experimental findings showed that the main cutting forces were reduced (on average by 22 %) due to cryogenic cooling, that also produced more damaged and fragmented chips. Moreover, cryogenic cooling averagely reduced (−22 %) the distance between chip serrations. The analysis of the simulation results revealed that cryogenic cooling reduced the tool-chip interface temperature of 150–200 °C due to the simultaneous cryogenic cooling action and to lower (about −35 %) tool-chip friction that limited the associated produced heat that represents at least one-tenth of the overall cutting power.

Impact of Single and Duplex Cryogenic Jets on Mechanical and Physical Characteristics in Turning of Titanium Superalloys

This analyses evaluates the cutting force , surface roughness, chip morphology, chip–tool interface temperature, tool life, and Single use of a coated carbide tool and double liquid nitrogen jets for friendly superalloy that is extremely difficult to cut being turned (Ti-6Al4V). The rake face was the only focus of the single jet, while the rake and flank surfaces were concurrently hit by the duplex jets. Liquid nitrogen jets provided the highest machining quality, reducing cutting force , temp, hardness, and, apparently, tool life. When equated to dry and single jet assist, the double liquid nitrogen jets increased life of the tool by 60% and 30%. In spite of this, chip manufacture has not changed. Using duplex liquid nitrogen jets to extend tool life, reduce tool costs, lower temperatures, improve surface quality, and most importantly, promote machinability of Ti-6Al-4V superalloy has been accepted as a sustainably booster.

Determination of the Chip–Tool Contact Length in Orthogonal Cutting

Abstract This work presents an experimental–numerical approach aimed at determining the chip–tool contact length during orthogonal cutting of annealed AISI 4340 steel (223 HV) with TiN-coated tungsten carbide inserts. Initially, pin-on-disc tests were performed, followed by orthogonal cutting tests. The components of the cutting force were used to calculate the coefficient of friction in orthogonal cutting, and its value was compared with those obtained under sliding. Moreover, the cutting force components obtained experimentally were used to assess the reliability of the finite element model and estimate the temperature in the cutting zone. The contact length between chip and rake face was calculated based on the experimental feed force and shear strength of the work material and was compared with the results provided by an analytical model. The experimental–numerical approach can be considered more accurate due to the fact that it considers the effect of the tool–chip interface temperature on the shear strength of the work material. However, the analytical model is quite straightforward, since it only requires the values of chip thickness and undeformed chip thickness to estimate the tool–chip contact length.

Machinability analysis and multi-response optimization using NGSA-II algorithm for particle reinforced aluminum based metal matrix composites

In this study the effects of reinforcement particle size and cutting parameters on machining performance variables like cutting force, maximum tool-chip interface temperature and surface roughness of the machined surface have been investigated while machining Aluminum based metal matrix composites (MMCs). MMC bars with silicon carbide reinforcement having 10 % volume fraction and particle sizes of 5 μm, 10 μm and 15 μm are machined with polycrystalline diamond (PCD) inserts. Experiments are performed using central composite design (CCD) having four parameters with three levels. Response surfaces for each performance variables are generated using polynomial models. Single variable and interaction effects have been investigated using principal component analysis and 3D response charts. Multi-response optimization has been performed to minimize surface roughness and maximum tool-chip interface temperature using non-dominated sorting genetic algorithm II (NSGA-II). In addition, constraints have been applied to the optimization search to filter design points with high cutting forces and low material removal rate. Most of the optimal solutions are found to be with moderate cutting speeds, low feed rate and low depth of cuts.

Understandings the tribological mechanism of Inconel 718 alloy machined under different cooling/lubrication conditions

Machining of Ni-based superalloys is a challenging issue, and it may lead to tool deterioration, poor surface quality, and other structural defects. Therefore, the main theme of this study is to examine the effect of different sustainable cooling/lubrication conditions on the machining performance, surface integrity, and accompanying tribological aspects of Inconel 718 superalloy. In this context, the milling experiment variables were selected as two feed rates, two cutting speeds, and four cutting environments: dry, air, synthetic oil-based MQL, and LN2-assisted Cryo. Tool wear mechanisms, surface roughness/profile/topography, cutting performance (tool-chip interface temperature and energy consumption), chip shapes, microstructures, and micro-Vickers hardness of the machined surfaces were thoroughly analyzed to assess experimental observations. The Cryo medium reduces tool wear, surface roughness, cutting temperature, and cutting energy by 67 %, 61 %, 85 %, and 33 % in comparison with a dry environment, respectively. Abrasion, adhesion, and diffusion mechanisms were supposed to be the most dominant wear types following SEM observations. Besides, the Cryo environment concluded a reduction of grain size to ⁓ 4 µm in concomitant with an increase of micro-hardness ⁓ % 15. The whole observed outcomes agreed to a great extent with each other, asserting the effectiveness of the LN2 cooling protocol in improving machining characteristics of Inconel 718 superalloy.

Modeling for prediction of tool-chip interface temperature in internal cryogenic turning considering film boiling

The cutting temperature model is critical for studying surface quality and tool wear. Cutting temperature models have been widely studied. When liquid nitrogen is used as a cooling medium in machining, the liquid nitrogen will inevitably appear Leidenfrost effect and film boiling will occur. However, the effect of film boiling on the cutting temperature is rarely concerned in the former temperature model. In this research, a novel model for tool-chip interface temperature considering film boiling is proposed. The new proposed model fully considered the thickness of the gas layer caused by the Leidenfrost effect compared with current models including Kesriklioglu's model and Rozzi's model. Based on the model, the effects of different gas layer thickness on the gas layer temperature and the tool-chip interface temperature were analyzed. The results indicate that thickness of the gas layer has a significant effect on the heat transfer properties and the tool-chip interface temperature of liquid nitrogen during the cooling process. The effect of film boiling must be considered in the temperature modeling of liquid nitrogen cooling machining. The new proposed model was accurately validated with a maximum error of less than 20% compared to previous studies and cutting experiments. It is also demonstrated that the developed liquid nitrogen internal cooling turning tool can control the gas layer thickness to about 5μ. This study reveals the heat transfer mechanism of cryogenic cooling, which helps to improve the cooling efficiency and the reliability of cryogenic cooling processing in industrial applications.

Turning performance analysis and optimization of processing parameters using GRA-PSO approach in sustainable manufacturing

The main aim of this research work is to examine the impact of input process factors (cutting speed, feed rate, and depth of cut) on machining characteristics (arithmetic mean surface roughness, tool flank face wear and tool chip interface temperature) and further to optimize during turning of Incoloy alloy 800. The cutting tool used was PVD multilayer coated (TiAlN-TIN) carbide insert. The experiment was performed based on Taguchi L27 methodology with a focus on the sustainability of turning. Sustainable manufacturing is considered for accomplishing overall efficiency with regard to economic, environmental and social aspects. The ANOVA (Analysis of Variance) was employed to assess the contributions of input process variables on cutting variable outputs. Further, the main effect diagrams exemplified the influences of main parameters on response variables. ANOVA analysis results demonstrated that the feed rate was the most leading factor that affects average surface roughness. The relationship(s) among input process factors and the evaluated measured outputs are determined using a quadratic regression model. Taguchi grey relational analysis has been implemented to trial results so as to optimize responses. The results revealed that the grey relational grade is significantly improved (0.308) through the setting of optimal parametric combinations. This integrated Grey–Taguchi approach was established quite effectual for simultaneously optimization of multifaceted machining output responses of turning process. This study provides a novel strategy to develop the machining efficiency of Incoloy 800 steel toward the improvement of sustainable processes and provide suitable applications in aerospace industry.

Effect of cutting edge radius on end milling Ti–6Al–4V under minimum quantity cooling lubrication – Chip morphology and surface integrity study

The effect of cutting edge radius (30–55 μm) during milling Ti–6Al–4V under minimum quantity cooling lubrication (MQCL) conditions is studied. A trial study is conducted to compare the performance of dry, wet, and MQCL using unprepared tools with edge radius of 30 μm alone. Subsequently, inserts having initial radius of 30 μm are prepared to 40–55 μm radius using drag finishing and milling of Ti–6Al–4V under MQCL is studied for different edge radii. Rounded edge tools are found to produce thinner and more curvilinear chips resulting in easier chip removal from the machining zone. The chip thickness and curl radius were up to 54% and 47% lower for the larger edge radius tools as compared to the 30 μm edge radius tool. This improves the penetration of the MQCL aerosol jet into the cutting zone thus producing better tribological results. The better penetration of MQCL aerosol into the cutting zone for larger edge radius tools results in lowering the resultant process forces (up to 16%), tool-chip interface temperature (15%), tool wear (40%) and surface roughness (30%) for the 48 μm radius tool as compared to the unprepared (30 μm) tool. There is deterioration in process forces, tool wear and surface integrity for the 55 μm tool possibly suggesting the existence of an optimum edge radius closer to 48 μm.

Influence of cutting parameters on end milling of magnesium alloy AZ31B

Magnesium alloys are having the characteristics like light weight, wear, and corrosion resistance. Mg alloys find usage in a wide range of applications such as engine block of automobile parts, laptop cases, aircraft fuselages and mobile outer cases. However, in dry machining, many challenges restrict its development during fitment. In this research work, conventional vertical milling machine was used to conduct end milling operation on Mg AZ31B alloy with coated carbide insert. End milling operations were performed by varying spindle speed, feed per tooth, and constant cutting depth. The chip morphology and tool chip interface temperature were investigated for various cutting conditions. Also, feed force (Fx), thrust force (Fy) and cutting force (Fz) was analyzed to understand the proper material deformation characteristics.

Modeling the effect of particle size while machining aluminum based metal matrix composite using an equivalent homogenous material approach

Due to their outstanding stiffness and resistant qualities, Metal Matrix Composites (MMCs) have exhibited extraordinary performance in a variety of industrial applications. However, due to constraints and challenges in their machining, they have not yet been fully employed. Indeed, it emphasizes the importance of obtaining essential information about their machinability. Finite element (FE) simulation is one of the most widely used and sustainable methods for studying machining mechanisms. In this study, 3D FE models based on equivalent homogenous material (EHM) approach are developed for MMCs to predict the effects of particle size on performance variables like cutting forces and maximum tool-chip interface temperatures. Turning experiments are conducted on MMC bars with 5, 10, and 15 µm' reinforcement particle sizes using the design of experiments based on the Sobol sequence. Cutting forces and other experimental data have been utilized to estimate equivalent Johnson cook parameters for the MMCs. The FE models' comparison with experiments shows good agreement for cutting force, thrust force, and maximum tool-chip interface temperatures.