Material Removal Temperature Research Articles

Fast determination of thermal conductivity of aluminum alloy by laser-induced breakdown spectroscopy

Abstract The matrix thermal properties are closely linked to laser-induced plasma, because it is the heat effect predominantly governs the process when the nanosecond-pulsed laser acting on the material, particularly in metallic materials. In the study using a series of pure metal samples, We detected a substantial inverse linear relationship linking the matrix’s thermal storage coefficient of the material to the temperature of the plasma. This discovery reveals that metals exhibiting reduced thermal conductivity or lower specific heat capacity necessitate a smaller amount of laser energy to achieve thermal spreading and to facilitate the transitions to the melted and vaporized states, which consequently results in a higher rate of material removal and higher plasma temperatures. Based on this correlation, a prediction model for the thermal conductivity of aluminum alloys has been developed, employing LIBS technique as analysis method, alongside PLS regression, with a relative error of below 1.5%. It presents a pioneering technique for the swift evaluation of thermal conductivity in aluminum alloys.

Effect of temperature on the material removal mechanism of LIPAA process

Laser induced plasma assisted ablation (LIPAA) is a new processing technology for transparent hard and brittle materials. During LIPAA processes, high temperature plasma thermal ablation and ion mechanical removal are coupled in the process of material removal. In this paper, an experimental method to study the effect of temperature on LIPAA process was presented. By using different metal targets (pure copper and pure iron) to carry out LIPAA processing experiments on sapphire C surface, the single-pulse energy threshold, microgroove morphology, microgroove surface roughness, material removal rate and temperature field of the processing area were compared. It was verified that the thermal properties such as the thermal conductivity of the metal target had a great influence on the processing results. The molecular dynamics simulation method was introduced to assist the theoretical analysis. The results showed that the material removal mechanism of laser-induced plasma processing sapphire was mainly thermal ablation. The mechanical energy generated by the shock wave of the plasma plume would assist the thermal energy to remove the material. The research results have guiding significance for exploring the sapphire LIPAA processing mechanisms at different temperatures and different targets.

Multi-Objective Optimization of AISI P20 Mold Steel Machining in Dry Conditions Using Machine Learning—TOPSIS Approach

In the present research, AISI P20 mold steel was processed using the milling process. The machining parameters considered in the present work were speed, depth of cut (DoC), and feed (F). The experiments were designed according to an L27 orthogonal array; therefore, a total of 27 experiments were conducted with different settings of machining parameters. The response parameters investigated in the present work were material removal rate (MRR), surface roughness (Ra, Rt, and Rz), power consumption (PC), and temperature (Temp). The machine learning (ML) approach was implemented for the prediction of response parameters, and the corresponding error percentage was investigated between experimental values and predicted values (using the ML approach). The technique for order of preference by similarity to ideal solution (TOPSIS) approach was used to normalize all response parameters and convert them into a single performance index (Pi). An analysis of variance (ANOVA) was conducted using the design of experiments, and the optimized setting of machining parameters was investigated. The optimized settings suggested by the integrated ML–TOPSIS approach were as follows: speed, 150 m/min; DoC, 1 mm; F, 0.06 mm/tooth. The confirmation results using these parameters suggested a close agreement and confirmed the suitability of the proposed approach in the parametric evaluation of a milling machine while processing P20 mold steel. It was found that the maximum percentage error between the predicted and experimental values using the proposed approach was 3.43%.

The Removal Mechanism of Monocrystalline Si in the Process of Double Diamond Abrasive Polishing by Molecular Dynamics Simulation

In order to clarify the mechanism of polishing of double diamond abrasive particles, in this study, the mechanism of material removal and the evolution of single crystal Si workpiece surface under the three-body polishing condition were investigated. The effect of the depth of polishing and the transverse/longitudinal spacing of the double abrasive grains on the three-body polishing were examined. The purpose is to reveal the phase transition, surface morphology, surface damage, material removal rate, temperature, potential energy, and friction force for polishing Si wafer. The analysis of coordination number clarified that the number of phase transition atoms by polishing and abrasion increased with increasing polishing depth and transverse distance of the nanoparticles on the Si work surface, but not especially obvious with increasing longitudinal spacing. Temperature analysis shows that when the polishing depth is 1 nm, the polishing temperature is 456 K, while when the polishing depth is 3 nm, the polishing temperature is 733 K. The temperature difference between the longitudinal group and the transverse group is only 30–40 K. The larger the transverse abrasive grain spacing or the smaller the polishing depth, the smaller the surface roughness; however, the longitudinal abrasive grain spacing has no obvious correlation with the surface roughness.

Analysis of multi-spark in wire electrical discharge machining

Electrical discharge machining plays a vital role in precision manufacturing processes. It is a non-conventional machining process in which electrical energy is converted into thermal energy by means of spark in a Di-electric fluid medium. Due to generation of temperature above melting point the material removal takes place. This paper presents the analysis performed on Aluminium 6061 – T6 Alloy with single-spark and multi-spark machining situations to predict temperature distribution and material removal rate. Gaussian heat flux distribution is used to simulate heat flux and four pulses are considered in multi-spark case in thermo-physical model. The results of single-spark and multi-spark simulated machining process were compared and it is observed that material removal rate and temperature distribution are higher in multi-spark simulated machining as compared to single spark.

To study the effect of different reinforcements on various parameters in aluminium matrix composite during CNC turning

Metal matrix composites are catching the eyeballs of various industries because of their enhanced properties like higher strength value over lesser weight, good stiffness and satisfies wide applications throughout. But to bring composite to use, always necessitate some machining process which remain a challenge for its user. In current research work, three Aluminum Metal Matrix composite (AMC) have been prepared by stir casting technique-AMC with eggshell (6% wt, 104 μm), AMC with boron carbide (6%wt, 104 μm) and hybrid AMC(6%wt egg shell+6%wt B4C, 104 μm). After preparation of composites, CNC turning is conducted at fixed process parameters of cutting speed 500 rpm, feed rate 0.1 mm/rev and depth of cut 0.5 mm. After the experiments, the responses such as material removal rate (MRR), surface roughness, residual stress and temperature between tool-work piece interfaces are recorded and evaluated. The experimental study revealed that MRR of hybrid and eggshell AMC's are found 43.24% more than the base alloy. It has also been observed that minimum surface roughness (Ra) of 2.2252 μm has been recorded for hybrid AMC. Base alloy shows the highest value of residual stress both, normal residual stress with value equal to (−) 48.5 MPa as well as shear residual stress with value (+)20.5 MPa whereas maximum average temperature of 51.1 °C recorded for hybrid composite among all the AMC's and base alloy.

Tool characteristics for better performance in machining ohns steel using coated tungsten carbide tool inserts

Turning Process is a significant machining process in which TiAlN covered tipped cutting tool inserts additions expel material from the outside of a pivoting round and hollow work piece. Machining of Oil Hardened Non Shrinking (OHNS) Steel is a challenge for production engineers in tool industry. In this examination paper, an investigation on turning OHNS Steel utilizing tungsten carbide instrument additions is made by shifting profundity of cut, feed rate and cutting rate each in turn and keeping other two consistent. The effect on process parameters like surface finish, material removal rate, tool wear, cutting force, thrust force and temperature distribution on tool tip are discussed.

Experimental investigation and optimization of micro-drilling parameters on Inconel 800 superalloy

ABSTRACT This work presents the experimental study and optimizing the micro-drilling parameters on geometrical accuracy in micro-drilling on Inconel 800. The geometrical accuracy of the holes is incorporating circularity, overcut, hole damage factor, and taper ratio. In addition to that, material removal rate, machining time, and temperature are taken for study. Micro-holes, based on Taguchi orthogonal array (L27) design, are drilled on the workpiece of 2 mm thickness using uncoated tungsten carbide tools. Medium tool diameter, low spindle speed, and high feed rate resulted in the reduction in the magnitude of machining temperature, machining time, minimum circularity, overcut, hole damage factor, and taper ratio with increased material removal rate. The feed rate, tool diameter, and spindle speed are the order of the influencing parameter on the geometrical accuracy of the hole. The number of holes drilled before tool breakage is 120 in magnitude. Further, the increase in circularity error by 1.12%, overcut, and taper ratio decrease by 60% and 25% from 1st to 120th hole at an optimal level of medium tool diameter, low speed, and high feed rate. From the investigation, 0.8 mm tool diameter can be chosen for micro-drilling of cooling holes in jet engines, printed circuited boards, and biomedical elements.

Performance analysis of cryogenically assisted high speed micro drilling of Incoloy 800 super alloy

Micro drilling is an advanced and precise process of producing down scale holes on various work materials. The superalloys play a major role in the present developing engineering field because of their predominant properties at a higher temperature. In this work micro drilling operations are conducted on Incoloy 800, superalloy at higher speeds using untreated and cryogenically treated drill bits to analyze the effect on response parameters such as material removal rate, surface roughness, thrust force and temperature. The experiments are executed by considering tool diameter, feed and speed of the spindle as the process parameters which are varied by three levels as per Taguchi L27 orthogonal array design. The optimized combination of process parameters are obtained by using grey relational analysis.

Optimization of Material Removal Rate and Temperature in Magnetic Abrasive Finishing Process for Stainless Steel 304

The effect of the magnetic abrasive finishing (MAF) method on the temperature rise (TR), and material removal rate (MRR) has been investigated in this paper. Sixteen runs were to determine the optimum temperature in the contact area (between the abrasive powder and surface of workpiece) and the MRR according to Taguchi orthogonal array (OA). Four variable technological parameters (cutting speed, finishing time, working gap, and the current in the inductor) with four levels for each parameter were used, the matrix is known as a L16 (44) OA. The signal to noise ratio (S/N) ratio and analysis of the variance (ANOVA) were utilized to analyze the results using (MINITAB17) to find the optimum condition and identify the significant parameters affecting on the TR., and MRR of the steel 304. IR camera was used to measure the experimental temperature. The results showed that the optimum temperature in contact area of workpiece is 70.7 °C.

A study on preheating temperature and heat affected depth according to various laser beam angle for laser-assisted machining

Laser-assisted machining (LAM) is a new method and actively researched for various difficult to machine materials. In LAM, machining is carried after prediction of material removal temperature (preheating temperature) for material with fixed cutting depth using a laser source. Among the various difficult-to-cut materials, Inconel 718, nickel-based super alloys, is difficult to machine due high strength at elevated temperature and low thermal conductivity. Studies on machining of Inconel 718 using a laser has been performed for various position of laser source to reveal the process benefits of Inconel 718 with fixed cutting depth. But there are no studies and results on prediction of heat affected depth for preheating temperature using laser assisted machining of Inconel 718 on various laser beam angle. So, in the present study, the effect of application of laser when applied at different angles is studied by two different methods- one with offset and other without offset. Finite element method is used to perform the simulations. This contribution brings a new novelty to the present research work on metal cutting domain using laser. The heat affected depth was also found and compared with depth obtained through experiments. And, the error percentage found for heat affected depth and preheating temperature is about 11%. The experimental results reveal that laser beam at an angle of 60° has maximum depth of cut, while minimum depth of cut is found at 90°.

Experimental and numerical investigations of machining depth for glass material in electrochemical discharge milling

Electrochemical discharge milling (ECDM) is one of the best alternatives for microchannel fabrication in non-conducting materials. The ECDM is a complex process which makes difficult the prediction of the material removal rate (MRR). The prediction of the machining depth in the microchannel fabricated with electrochemical discharge milling (ECD milling) was an interesting research subject. This study attempts to present a thermal model based on the finite element method (FEM) to predict the machining depth in ECD milling. The input parameters of the FEM model were calculated based on different machining conditions such as machining voltages and electrolyte concentrations. The model is validated by conducting experiments in the same ECD milling conditions. In the FEM model, the different criteria for the material removal temperature (Teq) were applied and the machining depths were calculated. The comparisons of the results show that there is good agreement between FEM models and experimental results when the Teq were selected between 600 to 850°C. It seems that the softening Littleton point of 720°C is a good suggestion as a criterion for the material removal temperature in ECD milling.

Analytical Solution of Transient Three-Dimensional Temperature Field in a Rotating Cylinder Subject to a Localized Laser Beam

Laser-assisted machining (LAM) is a growing trend in machining of hard to cut materials. In most experimental cases, LAM is carried out in two stages; first, laser and machine parameters are tuned to adjust the temperature at the material removal point (Tmr), and second, the cutting tool is engaged to cut the points that have already been heated by the laser. Alternatively, an analytical model for the prediction of temperature filed can replace lengthy experimentation needed for tuning the material removal temperature. This paper presents an analytical solution to the transient temperature field in a rotating cylinder subject to a localized laser heat source based on Green's functions. The analytical solution is validated by comparing the surface point temperatures to thermal experiments on DIN 1.7225 steel, which shows good agreement in trend and values. Furthermore, a finite element model is developed and verified by the results of the same experiments, providing a more detailed investigation on the performance of the analytical model. The developed analytical scheme can be used to readily calculate pointwise temperatures on workpiece surface and internal points which can be used as a tool for designing machining conditions.

Improved machinability of SiC/SiC ceramic matrix composite via laser-assisted micromachining

This study is focused on numerical modeling and experimental evaluation of laser-assisted micromachining (LAMM) of SiC/SiC ceramic matrix composite (CMC) materials. A novel experimental setup consisting of a fiber laser and the necessary optics, a three-axis CNC linear stage, and a high-speed spindle was used to implement the LAMM process. The laser-assisted micro-milling system provides unique micro-milling capabilities for flexible machining of very difficult-to-machine materials, such as ceramics, composites, and high-temperature alloys. The integrated high-power laser beam is flexibly focused on arbitrary positions around the cutting tool at a low incidence angle with a very small focused spot, thus making the system suitable for a wide range of micro-milling methods. Micro-end mills of cubic boron nitride (CBN) tools were used to perform slotting operations with and without laser preheating on CMC materials for comparative assessment. A three-dimensional (3D) transient finite-element-based thermal model was used to analytically predict appropriate process parameters on the basis of material removal temperature (Tmr). The effects of LAMM on the tool wear and tool life were evaluated experimentally. In addition, an economic analysis was carried out to compare LAMM of CMC materials with conventional micromachining methods.

Design and implementation of a system for laser assisted milling of advanced materials

Laser assisted machining is an effective method to machine advanced materials with the added benefits of longer tool life and increased material removal rates. While extensive studies have investigated the machining properties for laser assisted milling(LAML), few attempts have been made to extend LAML to machining parts with complex geometric features. A methodology for continuous path machining for LAML is developed by integration of a rotary and movable table into an ordinary milling machine with a laser beam system. The machining strategy and processing path are investigated to determine alignment of the machining path with the laser spot. In order to keep the material removal temperatures above the softening temperature of silicon nitride, the transformation is coordinated and the temperature interpolated, establishing a transient thermal model. The temperatures of the laser center and cutting zone are also carefully controlled to achieve optimal machining results and avoid thermal damage. These experiments indicate that the system results in no surface damage as well as good surface roughness, validating the application of this machining strategy and thermal model in the development of a new LAML system for continuous path processing of silicon nitride. The proposed approach can be easily applied in LAML system to achieve continuous processing and improve efficiency in laser assisted machining.

Cutting performance and coated tool wear mechanisms in laser-assisted milling K24 nickel-based superalloy

Laser-assisted machining (LAM) offers the ability to machine superalloys more efficiently and economically by providing the local heating of the workpiece prior to material removed by traditional cutting tool. The effectiveness of LAM was studied by measuring the cutting forces, surface roughness, and tool wear under various material removal temperatures (Tmr). It is demonstrated by an appropriate 30–70 % decrease in cutting force, an obvious reduction in the surface roughness, and an appropriate 46 % increase in coated tool life over conventional machining (CM). Machining experiments are then carried out to evaluate the wear behavior of different commercially available coated tools (TiCN, TiAlN, Ti(CN)/Al2O3/TiN). These coatings were selected since they have the capability to withstand the temperatures experienced in LAM. The results of laser-assisted milling experiments indicate that abrasive and adhesive wear were the dominant wear mechanisms, controlling the deterioration of the carbide tools. The TiAlN-coated tools exhibited the highest wear resistance at normal cutting speeds of 30 m/min. The triple layer CVD coated tool failure mode was non-uniform flank wear due to the adhesion and depth-of-cut notching. TiCN performed poorly due to their inferior adhesion characteristics with the base material. The main failure mode for TiCN was non-uniform flank wear and chipping, and also, a significant notch was observed. Sub-surface quality has been evaluated by observing the microstructure of cross sections and measuring the micro-hardness.

An experimental investigation of pulsed laser-assisted machining of AISI 52100 steel

Abstract Grinding and hard turning are widely used for machining of hardened bearing steel parts. Laser-assisted machining (LAM) has emerged as an efficient alternative to grinding and hard turning for hardened steel parts. In most cases, continuous-wave lasers were used as a heat source to cause localized heating prior to material removal by a cutting tool. In this study, an experimental investigation of pulsed laser-assisted machining of AISI 52100 bearing steel was conducted. The effects of process parameters (i.e., laser mean power, pulse frequency, pulse energy, cutting speed and feed rate) on state variables (i.e., material removal temperature, specific cutting energy, surface roughness, microstructure, tool wear and chip formation) were investigated. At laser mean power of 425 W with frequency of 120 Hz and cutting speed of 70 m/min, the benefit of LAM was shown by 25% decrease in specific cutting energy and 18% improvement in surface roughness, as compared to those of the conventional machining. It was shown that at constant laser power, the increase of laser pulse energy causes the rapid increase in tool wear rate. Pulsed laser allowed efficient control of surface temperature and heat penetration in material removal region. Examination of the machined subsurface microstructure and microhardness profiles showed no change under LAM and conventional machining. Continuous chips with more uniform plastic deformation were produced in LAM.

Experimental Study on Hybrid Ultrasonic and Plasma Aided Turning of Hardened Steel AISI 4140

Several methods such as plasma enhanced turning (PET) and ultrasonic-aided turning (UAT) have been introduced to assist conventional turning (CT) in order to overcome the difficulties of hard turning. There exist extensive experimental researches which have shown the feasibility of PET and UAT in hard turning. This paper investigates the cutting force and surface roughness in hybrid plasma and UAT hybird turning (HYT) on the AISI 4140 hardened steel. The studied parameters are turning parameters (cutting speed, feeding rate, and depth of cut), tool material, plasma, and ultrasonic parameters. For this purpose, a model was developed to relate current of plasma to the material removal temperature. The plasma and ultrasonic equipment were installed on the lathe, then hybrid ultrasonic and plasma aided machining was applied on AISI 4140 hardened steel for experiment using Taguchi design. Results showed the reduction of cutting forces in hybrid machining in comparison with CT, PET, and UAT; and depending on cutting conditions, workpiece surface roughness can be improved in hybrid machining in comparison with CT, PET, and UAT.

IMPROVING MACHINABILITY OF HIGH CHROMIUM WEAR-RESISTANT MATERIALS VIA LASER–ASSISTED MACHINING

The machinability of high chromium wear resistant materials is poor due to their high hardness with a large amount of hard chromium carbides. This study is focused on improving the machinability of high chromium wear resistant materials with different microstructures and hardness levels via laser-assisted machining (LAM). A laser pre-scan process is designed to preheat the workpiece before LAM to overcome the laser power constraint. A transient, three-dimensional LAM thermal model is expanded to include the laser pre-scan process, and is validated through experiments using an infrared camera. The machinability of highly alloyed wear resistant materials of 27% and 35% chromium content is evaluated in terms of tool wear, cutting forces, and surface integrity through LAM experiments using cubic boron nitride (CBN) tools. With increasing material removal temperature from room temperature to 400°C, the benefit of LAM is demonstrated by 28% decrease in specific cutting energy, 50% improvement in surface roughness and a 100% increase in CBN tool life over conventional machining.

A study on laser assisted machining using a laser area analysis method

In general, errors by mechanical and thermal deformation are resulted from the cutting forces and heat generation in cutting zone, respectively, while in machining operation. In the case of a laser integrated machine, which is used to process difficult-to-cut materials, High material removal temperature by laser preheating produces greater thermal deformation errors than that of conventional machines. However, there are difficulties in thermal analysis because a laser heat source has a very small input area and a large energy density and represents a sudden change in temperature due to its movement. In addition, it takes a long time to predict the surface temperature distribution of workpiece in existing analysis methods. Therefore, this study is aimed to predict such deformations caused by laser beams and machining processes using large-area analysis method which can reduce computation time.