Tool-workpiece Interface Research Articles

Prediction and optimization of cutting temperature on hard-turning of AISI H13 hot work steel

In the below investigation, the impact of speed, feed, depth of cut, and workpiece hardness on the cutting temperature at tool-workpiece interface on hard-turning of the American Iron and Steel Institute (AISI) H13 tool steel parts will be investigated. It is worth noticing that the inclusion of workpiece hardness as an input variable in discussing cutting temperature wasn’t widely investigated in the literature. Dry cutting experiments were done and the outcomes showed that the cutting temperature is highly influenced by the workpiece hardness. Also, it was noted that though the effect of depth of cut is statistically insignificant, yet it was found that the cutting temperature is an increasing function of the cutting depth. Furthermore, a predictive model for predicting cutting temperature was developed using response surface methodology (RSM) and artificial neural network (ANN) based on the inputs. The mean relative error was employed for testing the adequacy of the created predictive models, and its value was 3.56% and 0.844% for RSM and ANN respectively. Moreover, the new optimization algorithm, cuttlefish algorithm (CFA) was employed for optimizing the cutting temperature and the results were compared with those from the genetic algorithm (GA). The CFA obtained the best results at the least convergence rate.

Experimental Evaluation for Improving Multiple Quality Characteristics of Drilled Holes: A Case Study on Drilling of Ti6Al4V

Titanium alloys find increased applications in many engineering fields such as bio-medical, aerospace, electronics and automobile industries due to their superior physical properties such as high specific strength, weight to strength ratio, corrosive resistant and toughness. Low thermal conductivity of titanium alloys makes it difficult to machine since high cutting temperature is generated at tool work piece interface. As it is highly chemically reactive at high temperature, work piece is adhered to the tool surface. The present work aims at investigating the effect of drilling process parameters viz. spindle speed, drill bit diameter and feed rate on machining performance measures such as burr height at entry and exit, surface roughness and circularity at entry and exit. In order to optimize all the performance measures simultaneously, the present investigation utilizes a hybrid approach known as superiority and inferiority ranking method combined with technique for order preference by similarity to ideal solution (SIR-TOPSIS) to convert these characteristics into single equivalent characteristic ([Formula: see text]-flow). A statistically valid empirical relationship is developed for r-flow in terms of machining parameters using nonlinear regression technique. The study aims at attaining optimal parametric setting that maximizes [Formula: see text]-flow. To optimize [Formula: see text]-flow, an improved version of meta-heuristic evolutionary algorithm known as harmony search (HS) algorithm is implemented. The confirmatory experiment suggests the robustness of the methodology in optimizing the drilling operation.

Influence of Wax Lubrication on Cutting Performance of Single-Crystal Silicon in Ultraprecision Microgrooving

Lubrication can improve the tool-workpiece interface condition in ultraprecision machining, especially in microgrooving processes. The aim of this study was to compare the effects of dry, liquid (cutting oil), solid (wax) and hybrid (cutting oil and wax) lubrication conditions, on the creation of arc-sectioned microgrooves on single-crystal silicon wafers using a single-crystal diamond tool. Micro cutting forces, chip morphology, and surface quality at different locations of the grooves were investigated. Rose-shaped continuous chips were observed in dry cutting, indicating stable ductile mode material removal. The entrance side of the groove was always smoother than the exit side with a higher degree of phase transformation. Chip adhesions on the tool edge were found in dry and oil lubricated cutting, whereas wax coating could prevent the adhesion. Wax coating played the dual roles of a chip breaker as well as a high-performance lubricant, thus improved the surface integrity. This study demonstrated the capability of using wax coating as an environmentally friendly solid lubricant for microgrooving of single-crystal silicon and possibly for other hard brittle materials.

On the turning of electron beam melted gamma-TiAl with coated and uncoated tools: A machinability analysis

Abstract Electron beam melting (EBM) is one of the promising technologies with the capability of producing complex near-net shapes from difficult to process materials such as titanium alloys. However, the parts produced from the EBM process suffer from the poor surface quality and machining is required to finish the EBM parts to achieve the necessary surface quality. Unlike the reported studies in the literature, the current study employs both uncoated, and PVD multi-coated (TiAlN/Al2O3/ZrCN) carbide inserts for the finishing of the electron beam melted γ-TiAl (Ti-48Al-2Cr-2Nb) and compares the machinability performance to identify the suitable type of the tool and the corresponding machining conditions. The obtained results indicate that the performance of the uncoated inserts is far superior as compared to the coated inserts in terms of producing lower tool wear and cutting forces, improved surface finish and morphology, and less subsurface microstructural and hardness alterations. The poor performance of the coated inserts is due to the high-temperature accumulation at the tool-workpiece interface due to the thermal shielding effect of the coatings, leading to severe built-up layer formation resulting in cascading effect of higher cutting forces, tool wear and oxidation, and poor workpiece surface integrity.

Cooling/Lubrication Performance of Dry and Supercritical CO2-Based Minimum Quantity Lubrication in Peripheral Milling Ti-6Al-4V

Cryogenic environments are often adopted in machining difficult-to-cut materials such as Ti-6Al-4V alloy to control its cutting heat and improve machinability. This paper aims to study the machinability of Ti-6Al-4V in finish milling process under four green cutting environments (CEs), i.e. dry, supercritical carbon dioxide (scCO2), supercritical CO2-based minimum quantity lubrication with water-based cutting fluid (scCO2-WMQL), supercritical CO2-based minimum quantity lubrication with oil-on-water droplets cutting fluid (scCO2-OoWMQL). Peripheral finish-milling of Ti-6Al-4V was conducted under various cutting speeds, feed rates, radial depth of cut and CEs. The cutting force, cutting temperature, surface morphology and surface roughness were analysed. The experiment results show that the minimum cutting force and its coefficients, cutting temperature and surface roughness are obtained in scCO2-OoWMQL environment because of its excellent cooling/lubrication and chip evacuation performance, whereas the worst friction in the tool-workpiece interface leads to the worst performance under scCO2 CE. Additionally, the machined surface profile, cutting force and their spectrums under four CEs were studied. The fundamental frequency of machined surface profile is equal to that of cutting force envelope under dry and scCO2 CEs, which is also called beat frequency, therefore scCO2-WMQL and scCO2-OoWMQL CEs can improve the milling stability. The results indicate that scCO2-OoWMQL provides the best performance with regard to cutting force, cutting temperature, surface finish and clean production.

Physicochemical properties of degradable vegetable-based oils on minimum quantity lubrication milling

With increasing attention being paid to environmental and health problems in metal machining, developing an environmentally friendly cutting fluid is an urgent need. Degradable vegetable oils with non-toxicity and renewability are becoming increasingly popular. However, the mechanism of physicochemical properties of different vegetable oils is not clear on minimum quantity lubrication (MQL) milling. In the study, five typical vegetable oils (i.e., cottonseed, palm, castor, soybean, and peanut) were selected as base oil to experimentally evaluate the lubrication performance of the tool–workpiece interface compared with synthetic cutting fluid. With Grade 45 steel as workpiece material, the lubrication performance was evaluated in terms of milling force, surface roughness and surface morphology, as well as the composition, molecular structure, and viscosity of vegetable oils. Results showed that the vegetable-based oils achieved lower milling force and better surface quality than the synthetic cutting fluid. Among them, palm oil obtained the lowest milling force (Fx = 309 N, Fy = 154 N) at 7.76% and 13.6% lower than that of synthetic cutting fluids. The surface quality obtained by vegetable-based oils is superior to that of the synthetic cutting fluid, and the cottonseed and palm MQL acquired the best surface, while soybean obtained the worst surface. Furthermore, the results of surface roughness are consistent with those of surface morphology. Finally, according to the analysis of composition and molecular structure, palm and cottonseed with high content of saturated fatty acids are more suitable as MQL base oils.

Finite-Element Modelling of Forging with Torsion: Investigation of Heat Effect

The modern trend in material forming is the application of the combined processes for forging. Forging with torsion (FWT) is a non-conventional combined forging technology which is a sequential combination of two processes – the upsetting (axisymmetric compression) and the torsion (pure shear). The FWT is a relatively new forging process, preferably used for manufacturing the axisymmetric parts like disk or flange made of either continuous (bulk, casted or extruded) either discrete (powders and chips after machining) or additively manufactured parts. There are no limitations on the type of the materials treated by means of FWT. Some examples of worth-studying aspects in FWT are as follows: (1) the effect of the roughness on the material flow on tool-workpiece interface, (2) the effect of the severe plastic deformation on the microstructure of the obtained part, and (3) the effect of heat on material flow, especially the material flow on tool-workpiece interface. This article focuses on the investigation of the heat effect in FWT based on a finite-element simulation by QFORM-3D. The results presented in the article demonstrate the first approach to understand properly the phenomenon at the tool-workpiece interface. It is assumed that the heat effect could be decomposed, at least, into two components, viz., the heat effect of plastic deformation of a workpiece and that due to the contact friction on a tool-workpiece interface. The developed finite-element model allows to investigate the effect of friction factor on the temperature of the material within the deformation zone as well as at the tool-workpiece interface for different values of the angular speed of a rotating tool.

Tribological characterization of electrostatically developed Al2O3 coated cutting tool material

Wear mechanism plays a dominant part in minimizing the tool life in the course of machining difficult to machine materials. Issues related to wear mechanisms, namely spring back, variation in chips, and high-pressure loads, are accountable for tool wear. For machining numerous tool materials are not suitable due to volume specific heat and low thermal conductivity, which results in high cutting temperature. To address the above problem, electrostatic spray coating (ESC) coating technology is used to form Aluminum oxide (Al2O3) coating to enhance the life of cutting tool material. Aluminum oxide (Al2O3) having high hardness and chemical inertness will serve as a thermal barrier coating. This research work focuses on the effects of Al2O3 coating on the tool-workpiece interface. ESC technique was utilized for coating the Tungsten Carbide pin specimen with Al2O3. Utilizing the pin-on-disc tribometer, the wear and friction behavior of coatings were examined. Disc material being Ti-6Al-4V and pin (tungsten carbide) coated with Al2O3 were used to execute the dry sliding wear test at ambient atmosphere. The parameters, such as coefficient of friction, temperature, wear rate, and mass loss, were considered in this article. The performance metrics were analyzed from friction coefficient and frictional torque values obtained after the completion of tribological test from the pin on disc tribometer. Considerable endurance towards temperature and wear has been accomplished by Al2O3 coating.

Experimental investigation to study the performance of solid lubricant during turning EN31 steel and Ti-6Al-4V alloy

In the present day manufacturing industry, achieving machining accuracy, high production rate, and high material removal rate and increasing tool cutting life is becoming more vital and challenging task. Machining of hard materials is difficult to carry out because of high temperature generation between tool-workpiece interface which results in significant reduction in surface quality, tool life and high wear rates of the cutting tools are experienced. The use of proper lubrication in machining processes is critically important to modify the conditions of contact area by effective control over frictional interaction which should ensure change in tool-chip interface and machining mechanics. This paper present some preliminary results on experimental studies on EN31 and Ti-6Al-4V alloy materials on NC lathe machining using TiN coated cutting tool. MoS2 type of solid lubricants were used as lubricants. High velocity minimum quantity solid lubricant experimental setup is fabricated to supply graphite solid lubricant into tool-chip-workpiece interface. The present investigation concentrates in comparing the cutting force and surface roughness both in solid lubricant and dry conditions.

Optimization of cutting forces by cryogenic treatment on tungsten carbide inserts during dry turning of the P 20 tool steel

The cryogenic treatment is proven to be enhancing the properties of the material. The cryogenic surface treatment not only enhances the mechanical properties but can support the improvement of cutting parameters. The aim of the research conducted is to show the effect of cryogenic treatment on the Tungsten carbide tool insert to optimize the cutting parameters. The cutting force is selected as the parameters to improve as it is one of the key reasons to create stress at the tool-workpiece interface. Hence the comparison of untreated and cryogenically treated inserts was carried out to analyse the effect of surface treatment. Machining at higher speed and depth of cut can generate the higher stress and forces at the interface point. From experiments, it had been observed that the generation of the cutting forces reduces at the same cutting parameter configuration due to cryogenic surface treatment. Different trials were conducted using Taguchi's L27 orthogonal array. The results are also simulated on Matlab surface plot and ANN to study the optimization of parameters for every configuration and its effect.

Multi-objective optimization of WEDM process by hybrid methodology

Wire electro-discharge machining (WEDM) is an extensively used non-conventional, thermo-electrical machining process where the generated energy from the electrical sparks that occur in the tool-workpiece interface melts and removes the metal from the workpiece. It is largely used in machining difficult-to-cut temperature-resistant alloys, which have high strength. The workpiece material is taken as AISI P20 tool steel, a special purpose tool steel that is used to make plastic dies and molds. This has high wear-resistance, toughness and hardness. Servo voltage (Sv), Peak current (Ip), Pulse-off-time (Toff) and Pulse-on-time (Ton) are taken as process parameters and Kerf Width (KW) together with Material Removal Rate (MRR) are considered as the responses. In order to attain the optimum processing condition, Fuzzy- Technique for Order Preference by Similarity to Ideal Solution (TOPSIS), a hybrid multi-objective optimization technique is used.

Probing residual stresses in stationary shoulder friction stir welding process

Stationary shoulder friction stir welding (SSFSW) is a new variant of the conventional FSW with rotation of only the tool probe to reduce the rate of heat generation along the tool–workpiece interface and hence, weld joint residual stresses. Studies on the evolution of residual stresses in SSFSW are rare as the process is new. A detailed investigation on the evolution of welding-induced residual stress is reported here for SSFSW and the conventional FSW of four different aluminum alloys. A finite element method–based numerical model, JWRIAN-Hybrid, is used for the three-dimensional heat transfer and thermo-mechanical stress analyses. The computed results are validated extensively with the corresponding experimentally measured results. The results show approximately 10% to 20% reduction in the peak residual stresses in SSFSW under identical welding conditions.

Finite element simulations of conventional and ultrasonically assisted turning processes with plane and textured cutting inserts

This paper investigates the performance of conventional turning and ultrasonically assisted turning (UAT) processes with plane and textured cutting inserts. Simulations based on the finite-element method were carried out using a software package ABAQUS/Explicit (Dassault Systemes, France). The obtained results were validated experimentally by employing a specially developed UAT setup. The purpose of the paper is to analyze cutting-force variation by the use of textured cutting inserts. Optimized dimensions of the texture pattern were used to model textured cutting inserts. The cutting-force variation in UAT was assessed with finite-element method, confirming diminishing cutting forces at a tool–workpiece interface during a noncontact time. The use of the textured cutting inserts in the UAT process resulted in the lowest cutting forces when compared to a plane tool in UAT as well as both plane and textured tools in the conventional turning process.

Measurement and analysis of thrust force and torque in friction drilling of difficult-to-machine materials

Thrust force and torque applying in friction drilling contain some important information related to sufficient heat generation which can improve product quality and reduce tool wear. This concern becomes more challengeable when friction drilling is applied on difficult-to-machine materials. In the present study, temperature, thrust force, and torque for friction drilling of difficult-to-machine materials namely AISI304 and Ti-6Al-4V and Inconel718 are measured and analyzed. It contributes to provide an enhanced understanding of how friction in workpiece-tool interface increases the temperature. Subsequently, the sufficient heat generation, the effective thrust force, and torque that are needed to form a proper bushing with optimum features can be predicted. It is found that increasing in number of drilled holes reduces the quality of bushing shape. It is observed that thermal conductivity of workpiece material has significant effect on bushing formation quality. The findings indicate that better bushing formation and longer tool life are obtained from friction drilling of Inconel718. The microstructural changes of workpiece and tool wear are also analyzed and a relationship between them, temperature, thrust force, and torque, is explored. The maximum tool wear is observed on conical region where the process is in critical cycle time and temperature is on peak point.

Interrelation of Surface Temperature and Tribological Characteristics of a Protective Coating on a Tool

The study investigates the thermal and tribological characteristics of an uncoated P10 carbide tool and one coated with titanium carbide. Turning tests were conducted on AISI 1020 steel at four spindle speeds (80, 315, 500, and 800 rpm), two feed rates (0.2 and 0.5 mm/rev), and two cut depths (0.5 and 0.7 mm). The temperature change at the tool–workpiece interface, flank wear width, lifetime of tools, and roughness of the machined surface were determined. It is shown that the TiC coating significantly reduces temperature rise and flank wear during cutting. The lifetime of coated tools is about four times longer compared to uncoated tools. Coated tools also showed improved surface quality.

A comprehensive review on minimum quantity lubrication (MQL) in machining processes using nano-cutting fluids

The cutting fluid is significant in any metal cutting operation, for cooling the cutting tool and the surface of the workpiece, by lubricating the tool-workpiece interface and removing chips from the cutting zone. Recently, many researchers have been focusing on minimum quantity lubrication (MQL) among the numerous methods existing on the application of the coolant as it reduces the usage of coolant by spurting a mixture of compressed air and cutting fluid in an improved way instead of flood cooling. The MQL method has been demonstrated to be appropriate as it fulfills the necessities of ‘green’ machining. In the current study, firstly, various lubrication methods were introduced which are used in machining processes, and then, basic machining processes used in manufacturing industries such as grinding, milling, turning, and drilling have been discussed. The comprehensive review of various nanofluids (NFs) used as lubricants by different researchers for machining process is presented. Furthermore, some cases of utilizing NFs in machining operations have been reported briefly in a table. Based on the studies, it can be concluded that utilizing NFs as coolant and lubricant lead to lower tool temperature, tool wear, higher surface quality, and less environmental dangers. However, the high cost of nanoparticles, need for devices, clustering, and sediment are still challenges for the NF applications in metalworking operations. At last, the article identifies the opportunities for using NFs as lubricants in the future. It should be stated that this work offers a clear guideline for utilizing MQL and MQL-nanofluid approaches in machining processes. This guideline shows the physical, tribological, and heat transfer mechanisms associated with employing such cooling/lubrication approaches and their effects on different machining quality characteristics such as tool wear, surface integrity, and cutting forces.

Evaluating the Rheological and Tribological Behaviors of Coconut Oil Modified with Nanoparticles as Lubricant Additives

In metal-forming processes, the use of lubricants for providing desirable tribological conditions at the tool–workpiece interface is critical to increase the material formability and prolonging tool life. Nowadays, the depletion of crude oil reserves in the world and the global concern in protecting the environment from contamination have renewed interest in developing environmentally-friendly lubricants derived from alternative sources such as vegetable oils. In the present study, the rheological and tribological behavior of coconut oil modified with nanoparticle additives was experimentally evaluated. Two different nanoparticle additives were investigated: Silicon dioxide (SiO2) and copper oxide (CuO). For the two conditions, nanoparticles were dispersed at different concentrations within the coconut oil. The effects of concentration and shear rate on the viscosity were evaluated and the experimental data was compared with conventional models. A custom-made tribotester was used to evaluate the effect of concentration on the tribological performance of the nano-lubricants. The experimental results showed that wear volume loss was lowered by 37% and 33% using SiO2 and CuO nanoparticles, respectively. Furthermore, the addition of SiO2 and CuO nanoparticles decreased the coefficient of friction (COF) by 93.75% and 93.25%, respectively, as compared to coconut oil without nanoparticles.

Design of a device for testing and analyzing the friction coefficient during metal cutting

This paper seeks to illustrate the development of a device for tribotesting and analysing of friction and normal forces in orthogonal cutting. In order to investigate the friction and normal forces, the objective of the device will be focused on the analyzing of the behavior of the tool-chip (rake surface) or tool-workpiece interface (flank surface) under dry metal cutting conditions. The device will simulate an orthogonal cutting process conditions that can be afterward modified for another cutting process basically with different geometries. The testing setup allows the friction coefficient to be estimated using the well-known Coulomb’s friction law. Experimental procedures were conducted to validate the new device. The experiments were carried out using a tungsten carbide P20 as insert and C45 as the workpiece material, and the results showed that the coefficient of friction is dependent on the area of contact between the tool and workpiece.

Flank tool wear prediction of laser-assisted milling

An analytical predictive model for flank tool wear in laser-assisted milling is proposed based on the principles of abrasive, adhesive, and diffusive wear. The laser effect is included by treating the laser beam as a heat source on top surface. Heat convection between top surface and the environment is factored into account. Isothermal boundary conditions are assumed for the laser-affected area. The laser preheating temperature field is averaged along the tool-workpiece interface as initial temperature. Next, the milling configuration is treated as orthogonal cutting followed by angular-dependent coordinate transformation at each instance. The effective force due to flank wear is calculated by integrating the stress component along the chip cross section and wear land, and the average stress on tool-workpiece interface due to flank wear is calculated based on the effective force and contact area. The average temperature along the interface is derived through imaginary heat source method with secondary and rubbing heat sources considered. The flank wear rate prediction considers abrasion, adhesion, and diffusion. The proposed model is validated through experimental measurements on the laser-assisted milling of K24 nickel-based superalloy, and a sensitivity analysis with respect to three cutting and two laser parameters is conducted. The proposed predictive model is able to match the wear progressions during steady state wear region in less than two minutes with high accuracy of 6.48% error on average. Therefore, it is valuable for providing a fast, credible, and physics-based method for the prediction of flank tool wear in laser-assisted milling of various materials. Through sensitivity analysis, the model is able to guide the selection of cutting and laser parameters when the flank tool wear is the main concern.

Experimental Investigation of Bubble-Mixed Cutting Fluid Delivery for Micro Deep-Hole Drilling

In drilling, chip-clogging results in increased drilling temperature, excessive tool wear, and poor hole quality. Especially, in microdrilling, low rigidity of the tool and inability of cutting fluid to penetrate narrower tool–workpiece interface significantly reduce the drilling performance. A novel bubble-mixed cutting fluid delivery method proposed in this research aims toward achieving a high-performance micro deep-hole drilling process with a significant reduction in the consumption of cutting fluid. Experimental results show that the bubble-mixed cutting fluid delivery method achieves lower thrust force during drilling, higher drilled depth before tool breakage, and lower dimensional and circularity errors when machining deep holes in comparison with dry cutting or conventional flood delivery method. It is also found that the smaller-sized bubbles effectively penetrate the tool–workpiece interface during the drilling producing deeper holes by better chip evacuation and cooling.