Average Interface Temperature Research Articles

Decision Tree-Supported Analysis of Gallium Arsenide Growth Using the LEC Method

In this study, an axisymmetric Czochralski furnace model for the LEC growth of gallium arsenide is presented. We produced 88 datasets through computational fluid dynamics simulations. Among the many parameters that affect crystal growth, a total of 13 input parameters were selected, including the geometry and material parameters of the hot zone (crucible, heaters, radiation shield, and crystal), as well as the process parameters (such as pulling and rotation rates, heating power, etc.). Voronkov criteria (v/Gn), interface deflection, and the average interface temperature gradient were selected as the output parameters. We carried out a correlation analysis between the variables and used decision trees to study the impact of the 13 input variables on the output variables. The results indicated that in the growth of gallium arsenide, the main factor affecting interface deflection and the average interface thermal gradients is the crucible rotation rate. For v/Gn, it is the pulling rate.

Thermal rectification in polytelescopic Ge nanowires

Herein we served non-equilibrium molecular dynamics (NEMD) approach to simulate thermal rectification in the mono- and polytelescopic Ge nanowires (GeNWs). We considered mono-telescopic structures with different Fat-Thin configurations (15-10 nm-nm or Type (I); 15-5 nm-nm or Type (II); and 10–5 or Type (III) nm-nm) as generic models. We simulated the variation of thermal conductivity against interfacial cross-sectional temperature as well as the direction of heat transfer, where a higher thermal conductivity correlating to thicker nanowires, and a more significant drop (or discontinuity) in the average interface temperature in the positive (or negative) direction were detected. Noticeably, interfacial thermal resistance followed the order of Type (II) (48 K/μW, maximal) ˃ Type (III) ˃ Type (I) (5 K/μW, minimal). In the second stage, a series of polytelescopic nanostructures of GeNWs were born with consecutive cross-sectional interfaces. Surprisingly, larger interfacial cross-sectional areas equivalent to smaller diameter changes along the GeNWs were responsible for higher temperature rectification. This led to a very limited thermal conductivity loss or a very high unidirectional heat transfer along the polytelescopic structures - the key for manufacturing next generation high-performance thermal diodes.

A Multi-scale Contact Temperature Model for Dry Sliding Rough Surfaces

A multi-scale flash temperature model has been developed and validated against existing work. The core strength of the proposed model is that it can be adapted to predict flash contact temperatures occurring in various types of sliding systems. In this paper, it is used to investigate how different surface roughness parameters affect the flash temperatures. The results show that for decreasing Hurst exponents as well as increasing values of the high-frequency cut-off, the maximum flash temperature increases. It was also shown that the effect of surface roughness does not influence the average interface temperature. The model predictions were validated against data from an experiment conducted in a pin-on-disc machine. This also showed the importance of including a wear model when simulating flash temperature development in a sliding system.

Thermal modelling of cutting tool temperatures and heat partition in orthogonal machining of high-strength alloy steel

Cutting temperatures and heat partition into the cutting tool are critical factors that significantly affect tool life and part accuracy during metal removal operations, especially in dry machining. Among many thermal modelling studies, uniform heat partition ratio, and/or uniform heat intensity along the tool-chip interface are frequently assumed. This assumption is not valid in actual machining and can lead to erroneous estimated results in the presence of sticking and sliding friction zones. Therefore, it is necessary to accurately predict the cutting tool temperature and heat partition during machining. This paper presents an analytical thermal modelling approach which considers the combined effect of the primary and the secondary heat sources and determines the temperature rise and non-uniform heat partition ratio along the tool-chip interface. Cutting tests were conducted on AISI/SAE 4140 high-strength alloy steel using carbide cutting tools over a wide range of cutting speeds. Cutting temperatures were measured experimentally using an infrared thermal imaging camera. Experimentally established sticking and sliding friction regions were used to evaluate non-uniform frictional heat intensity along the tool-chip interface. The temperature matching condition along the tool-chip interface leads to the solution of distributed non-uniform heat partition ratio by solving a set of linear equations through programming in MATLAB®. Experimental results show to be consistent well with those obtained from the thermal model, yielding a relative difference of predicted average tool-chip interface temperature from −0.8% to 6.3%. It is found that average heat partition into the cutting tool ( RT) varies from 35% down to 15% for the entire range of cutting speeds. These results suggest that, to address the thermal problem in metal cutting, the research and development of tooling should also focus on reducing friction on the tool rake face in addition to the contribution of the combined effect of primary and secondary heat sources on temperature rise at the tool-chip interface.

Evaulation of a equivalent homogeneous material model while machining aluminum based metal matrix composite

Abstract Metal Matrix Composites (MMCs) have demonstrated remarkable performance in many industrial applications due to their exceptional rigidity and resistance properties. However, they have not yet been utilized to their fullest because of impediments and challenges in their machining. Certainly, it highlights the significance and acquisition of relevant information concerning their machinability. Finite element (FE) simulation is one of the most universally acknowledged and sustainable tools for investigating the mechanism of machining. Therefore, this work presents two and three dimensional (2D and 3D) FE models to simulate the orthogonal cutting of silicon carbide (SiC) reinforced aluminum (Al)-based MMC. A 2D micromechanics based model (MM model) has been implemented to estimate the behavior of MMC machining based on particle size and volume fraction. In addition a 3D equivalent homogenous material model (EHM model) has also been developed based on a modified flow stress model which depends volume fraction of the MMC. The model outcomes in terms of cutting forces and temperature distributions have been discussed. It has been found that both models show comparable results with the experiments. The MM model is found to be efficient in predicting the local variables such as stress and temperature contours around the workpiece and cutting tool. However the global variables such as cutting forces and average tool-chip interface temperature can be predicted more easily with the EHM model as they are found to be computationally less expensive than the MM model.

Molecular Dynamics Simulation of Heat Transfer at Contact Interface of Hot Forming Die

During metal hot forming process, the billet and the die interact by contact under high temperature, high pressure and severe sliding. In this paper, an atomistic approach is utilized to study the behaviour of heat transfer at the contact interface of hot forming die and the material. Based on non-equilibrium molecular dynamics and phonon scattering theory, the phonon heat transfer process at the billet/die rough interface at nano-scale is analysed. The effects of interfacial lattice defect concentration and average interfacial temperature on the phonon heat transfer coefficient are examined. It is found that when the lattice defect concentration increases the phonon mismatch at the interface deteriorates and the interfacial thermal resistance increases, which leads to a sharp decrease in phonon heat transfer coefficient. A higher temperature of the contact body and a higher average interface temperature lead to a higher probability of inelastic scattering of phonons at the interface. Moreover, the high frequency phonons at high temperature might be decomposed into two or more low frequency phonons during the energy transmission, which increases the propagation of phonon at the interface; thus the phonon heat transfer coefficient increases accordingly.

Numerical investigation of evaporation and radiation absorption of a non-spherical water droplet under asymmetrically radiative heating

A numerical model for evaporation along with internal radiation absorption of a non-spherical droplet is presented. In this model, the VOF method is utilized to trace the interface and the radiative transfer is taken into account by using the Monte Carlo method combined with a contour based interface reconstruction algorithm. Meanwhile, the dynamic mesh technique is applied to increase the computational efficiency. The validated model is used to investigate the radiation absorption inside prolate and oblate water droplets under infrared laser irradiation, and a parametric study for the effects of droplet’s shape and size is presented. The results reveal that the shape of droplet dominates the spectral absorptance when the droplet’s optical thickness is small, but for optically thick droplets, the radiation absorption turns to be dominated by the spectral reflectivity of the irradiated surface. For a deformable droplet under asymmetrically radiative heating, the incident radiation can significantly enhance the heat transfer and evaporation processes. In addition, the assumption of uniform radiation absorption is found to be valid to optical thin droplets, whereas this assumption will underestimate the average interface temperature and evaporation rate of droplets with large optical thickness.

Thermal and acoustic performance of an integrated automotive thermoelectric generation system

In recent years, the use of thermoelectric generators (TEGs) to recover secondary energy from exhaust heat has increased speedily with applications ranging from microwatts to kilowatts. In terms of automotive exhaust system, there are compatibility problems among automotive TEG, catalytic converter and muffler. An integrated automotive thermoelectric generator (IATEG) which contains automotive TEG, catalytic converter and muffler that converts engine exhaust waste heat into electricity is constructed and simulated. Through comparison of steel, aluminum and copper heat exchangers, it is found that both the average interface temperature and the maximum output power increase are highly dependent on the thermal conductivity of the heat exchanger material. An engine bench test and an acoustic bench test are developed to analyze the performance of the IATEG system characteristics, which are undertaken to assess the feasibility of automotive applications. The numerical simulations and experiment results indicate that the IATEG has better sound reduction performance in high frequency noise and higher temperature distribution which can generate a high power while the power output of the TEG can reach 515 W. Through these experiments, thermal, electrical and acoustic performance of the system is characterized. The results establish the fundamental development of IATEG system that enhances the TEG efficiency for vehicles.

FEM based evaluation of Ti6Al4V cutting with plain and textured WC/Co tools under cryogenic cooling environment

The present work investigates the effect of cryogenic coolant on machining of Ti6Al4V alloy with plain and laser textured carbide cutting tools. The textured tools were used for machining under dry and cryogenic cutting conditions, and the machining results were compared with plain tools. Cutting forces, average tool temperature, interface temperature, and tool wear were predicted with the help of FE simulations. Results show a reduction in average cutting temperature for textured tools under cryogenic conditions. FEM simulations predicted the microscopic wear inside and around the textures and nearly 50% reduction in microscopic wear has been obtained for textured tools under cryogenic cooling.

Investigation of Chip-Tool Interface Temperature: Effect of Machining Parameters and Tool Material on Ferrous and Non-Ferrous Metal

In the present context of sustainable manufacturing and eco-friendly scenario, investigation of cutting temperature generated during machining of various ferrous and non-ferrous metals is an act of concern to understand the metal cutting issues such as dimensional accuracy, surface finish, tool wear, material removal rate and tool life. In this investigation, average chip-tool interface temperature has been determined taking into account the effect of machining parameters and the tool material, namely, tungsten carbide and poly crystalline diamond (PCD) during turning of IS 733 Gr 63400 aluminium and IS 2062 steel. Mathematical model was developed based on experimental observations to predict the average chip-tool interface temperature. Experimental results concluded that the temperature showed a rise on increasing the machining parameters. It was also concluded that the temperature during machining of ferrous metals significantly depend on tool material while for non-ferrous metals (ductile) the tool material is less significant. Among the machining parameters cutting speed highly influence the average chip-tool interface temperature.

Effect of Cux substituted for Gax on the thermodynamic and fracture behavior in magnetic shape memory Ni50Mn30Ga20 − xCux with high transformation temperature

The effect of Cux substituted for Gax on the thermodynamic characteristic, evolution of phases and fracture behavior in Ni50Mn30Ga20 − xCux alloys have been investigated. The results show that the martensitic transformation, reverse transformation temperatures and average interface temperature of Ni50Mn30Ga20 − xCux sample increase remarkably with increased content of Cu. The hysteresis temperature of the austenite to martensite transition firstly showed a steep rising trend, then almost reduced to a lower rate with the increased content of Cu up to 4 at.% (the maximum level of copper addition studied). The (202) diffraction peak position was observed to shifted towards high angles, when the Cu content was lower than 1 at.%. Further, the, M202 diffraction peak was found to split into two diffraction peaks when the Cu content was more than 1 at.%. In addition, the compressive strength and fracture strain of alloys is clearly enhanced with increased content of Cu. Furthermore, the fracture type of Ni50Mn30Ga20 − xCux alloys was found to changes from intergranular fracture for the Ni–Mn–Ga alloys, to transgranular cleavage fracture with increase in Cu content.

Estimation of real contact area during sliding friction from interface temperature

Frictional heat is one of the most important topics in tribological research. The real contact area of the frictional pair plays a significant role in accurately estimating the interface temperature, which is closely related to the frictional heat. However, conventional methods for measuring the contact area, such as constriction resistance measurements, are not suitable for dynamic frictional motion because of the electrical and thermal interferences at the contact region. In this study, a novel method is presented for estimating the real contact area during sliding friction. First, the average interface temperature was experimentally measured by the dynamic thermocouple method. Then assuming that the total frictional heat power is constant, the measured temperature was used as a constraint to determine the contact area in a finite element model, giving an estimation for the real contact area. The calculation results show that the real contact area increases with increasing normal load as predicted by contact theories, and decreases with increasing sliding speed, which could be attributable to the contact dynamics of asperities at the interface. Additionally, the limits of the proposed method is discussed.

Response surface and neural network based predictive models of cutting temperature in hard turning

The present study aimed to develop the predictive models of average tool-workpiece interface temperature in hard turning of AISI 1060 steels by coated carbide insert. The Response Surface Methodology (RSM) and Artificial Neural Network (ANN) were employed to predict the temperature in respect of cutting speed, feed rate and material hardness. The number and orientation of the experimental trials, conducted in both dry and high pressure coolant (HPC) environments, were planned using full factorial design. The temperature was measured by using the tool-work thermocouple. In RSM model, two quadratic equations of temperature were derived from experimental data. The analysis of variance (ANOVA) and mean absolute percentage error (MAPE) were performed to suffice the adequacy of the models. In ANN model, 80% data were used to train and 20% data were employed for testing. Like RSM, herein, the error analysis was also conducted. The accuracy of the RSM and ANN model was found to be ⩾99%. The ANN models exhibit an error of ∼5% MAE for testing data. The regression coefficient was found to be greater than 99.9% for both dry and HPC. Both these models are acceptable, although the ANN model demonstrated a higher accuracy. These models, if employed, are expected to provide a better control of cutting temperature in turning of hardened steel.

Cutting force modeling considering tool wear effect during turning of hardened AISI 4340 alloy steel using multi-layer TiCN/Al2O3/TiN-coated carbide tools

This study attempts to develop a cutting force model under oblique cutting conditions considering tool wear effect during turning of hardened steel with coated carbide tools to address metal cutting issues such as tool life, dimensional accuracy, and surface finish. Forces in worn out tool have been modeled by summing up forces in sharp tool and the forces due to flank wear alone. Waldorf’s orthogonal force modeling approach is extended to 3-D cutting force analysis to model cutting forces due to flank wear alone. Forces in sharp tool and average interface temperature generated during machining are modeled using regression analysis. Shear flow stress, shear angle, and other model prerequisites are determined using equivalent cutting edge geometry in place of the actual cutting edge of tools having nose radius. Worn tool cutting force model is validated in turning of hardened AISI 4340 steel at different levels of hardness 35 and 45 HRC, respectively, using multi-layer TiCN/Al2O3/TiN-coated carbide tools. The quantitative agreement between experimental result and that of a developed model of worn tool cutting forces is favorably good with an average error of less than ±5 % with a maximum error of 11 %, which showed that the developed model is reliable and could be used effectively for predicting the forces in worn out tool within the domain of the cutting parameters.

Evaporation of sessile drops: a three-dimensional approach

The evaporation of non-axisymmetric sessile drops is studied by means of experiments and three-dimensional direct numerical simulations (DNS). The emergence of azimuthal currents and pairs of counter-rotating vortices in the liquid bulk flow is reported in drops with non-circular contact area. These phenomena, especially the latter, which is also observed experimentally, are found to play a critical role in the transient flow dynamics and associated heat transfer. Non-circular drops exhibit variable wettability along the pinned contact line sensitive to the choice of system parameters, and inversely dependent on the local contact-line curvature, providing a simple criterion for estimating the approximate contact-angle distribution. The evaporation rate is found to vary in the same order of magnitude as the liquid–gas interfacial area. Furthermore, the more complex case of drops evaporating with a moving contact line (MCL) in the constant contact-angle mode is addressed. Interestingly, the numerical results demonstrate that the average interface temperature remains essentially constant as the drop evaporates in the constant-angle (CA) mode, while this increases in the constant-radius (CR) mode as the drops become thinner. It is therefore concluded that, for increasing substrate heating, the evaporation rate increases more rapidly in the CR mode than in the CA mode. In other words, the higher the temperature the larger the difference between the lifetimes of an evaporating drop in the CA mode with respect to that evaporating in the CR mode.

Evaluation of Chip-tool Interface Temperature: Effect of Tool Coating and Cutting Parameters during Turning Hardened AISI 4340 Steel

In the present context of sustainable manufacturing, investigation of cutting temperature during machining is extremely valuable to address metal cutting issues such as dimensional accuracy, surface finish and tool life. In this study, average chip-tool interface temperature was investigated considering the effect of cutting parameters and the type of coating (coated tools), namely, PVD- applied single-layer TiAlN and CVD-applied multi-layer TiCN/Al2O3/TiN during turning of hardened steel. Mathematical model which can predict the average chip-tool interface temperature was developed based on experimental observations which were obtained in the wide range of cutting conditions. A calibration set-up based on tool-work thermocouple principle was developed to correlate the emf (electro motive force) and the interface temperature. R-squared value for the developed model found 0.9693, indicate that the developed model is reliable and could be used effectively for predicting the interface temperature within the domain of the cutting parameters for the given tool and work material pair. Experimental observations indicate that the interface temperature is higher for CVD-coated multi-layer coated tool in comparison to single-layer TiAlN, which get affected mostly by cutting speed followed by feed. However, depth of cut has negligible influence on interface temperature when using both the coated carbide tools.

Machinability Assessment through Experimental Investigation during Hard and Soft Turning of Hardened Steel

In this study, experimental investigations were carried out to assess the machinability of hardened AISI 4340 steel during hard (55 HRC) and soft turning (35 and 45 HRC) using TiC mixed alumina ceramic tools. Mathematical models, which can predict the machining performances, namely, chip-tool interface temperature, cutting forces and surface roughness were developed based on experimental observations. Effect of workpiece hardness and cutting parameters, namely, cutting speed, depth of cut and feed on different responses were analyzed by performing ANOVA technique. Experimental observations indicate higher cutting forces, higher chip-tool interface temperature and lower values of surface roughness for harder workpiece. Feed value has been observed to have more prominent effect on surface roughness. However, the average chip-tool interface temperature has been observed to get more influenced with cutting speed and depth of cut. On the other hand, cutting forces, especially radial component of force which was largest in magnitude amongst the tangential and feed cutting forces, has been observed to get more affected with depth of cut followed by feed value.

Effects of tool–workpiece interface temperature on weld quality and quality improvements through temperature control in friction stir welding

A real-time wireless temperature measurement system has been developed and successfully implemented for closed-loop control of tool shoulder–workpiece interface temperature. The system employs two thermocouples in through holes and measures the shoulder and pin interface temperatures with an angular resolution as small as 10°. Both temperatures correlate with weld quality (mechanical testing and weld cross sections), e.g., all welds in 4.76-mm-thick 6061-T6 with an average shoulder interface temperature below 520 °C and an average pin interface temperature below 460 °C fail in the weld zone instead of the heat-affected zone, have unacceptable tensile strengths and in some cases voids. Similarly, welds with shoulder temperatures above the solidus temperature result in a degradation of the weld quality. It was found that a shoulder interface temperature of 533 °C results in the highest weld quality; hence, this temperature should be used as the setpoint temperature in the control system with a constant travel speed of 400 mm/min. The temperature measurement strategy was shown to be able to indicate welds with insufficient shoulder–workpiece contact, thus potentially identifying and preventing welds with detrimental weld quality due to lack of penetration. It was shown that backing plates of different thermal diffusivity change the heat flow out of the weld zone, hence weld temperature, and caused a measurable impact on the weld strength. By changing other process parameters, e.g., through a temperature control system, weld quality can be maintained in the presence of such changing thermal boundary conditions.

Investigation on Surface Roughness and Cutting Temperature in Turning AISI 316 Austenitic Stainless Steel Using TiAlSiN Coated Carbide Insert

This study presents experimental result of surface roughness and chip-tool interface temperature developed during turning of AISI 316 austenitic stainless steels using TiAlSiN coated cemented carbide insert. TiAlSiN coating is deposited by Cathodic Arc Evaporation (PVD) technique. The work-tool thermocouple calibration set-up was developed. The air heater was used as a heating element at the work-tool junction. The experiments were conducted at cutting speeds in the range of 140 to 320 m/min, feed in the range of 0.08 to 0.26 mm/rev keeping depth of cut constant at 1 mm. The influence of cutting parameters and tool coating were investigated on the average chip-tool interface temperature and surface roughness. Experimentally interface temperature 979°C was observed at 260 m/min cutting speed and 0.14 mm/rev feed. The interface temperature in turning is strongly dependent on the cutting speed followed by feed and exactly reverse case was observed in case of surface roughness. TiAlSiN coating shows better performance and can be considered as a prominent candidate for the machining of AISI 316 work material.

Analytical and Experimental Investigation on Cutting Temperature in Turning AISI 304 Austenitic Stainless Steel Using AlTiCrN Coated Carbide Insert

This study presents analytical and experimental results of cutting force and chip-tool interface temperature developed during turning of AISI 304 austenitic stainless steels using nano-crystalline AlTiCrN coated cemented carbide insert. The work-tool thermocouple calibration set-up based on the novel concept was developed. Inconel air heater of 1 KW capacity was used as a heating element at the work-tool junction for heating the junction steadily up to 1000 °C. The turning tests were conducted at cutting speeds in the range of 140 to 320 m/min, feed in the range of 0.08 to 0.26 mm/rev keeping depth of cut constant at 1 mm. The influence of cutting parameters and tool coating were investigated on the average chip-tool interface temperature and cutting force. A regression model for chip-tool interface temperature was developed considering the effect of cutting parameters. In addition, the experimental results were validated using the 'Boothroyd temperature model'. Experimentally an interface temperature of 979°C was observed whereas the model predicted 988°C temperature at 260 m/min cutting speed and 0.14 mm/rev feed. The interface temperature in turning is strongly dependent on the cutting speed followed by feed. The AlTiCrN coated shows excellent thermal stability due to the formation of stable Cr2O3 or and dense α(Al,Cr)2O3 mixed oxide scales. The developed interface model shows excellent fit and could be used effectively for predicting the interface temperature for the given tool and work material and cutting conditions.