Heat Source Method Research Articles

Modeling of temperature distribution in turning of Ti-6Al-4V with liquid nitrogen cooling

A predictive thermal analytical model based on the improved Oxley’s theory and the image heat source method for orthogonal cutting was proposed to obtain the exact temperature distributions in the chip, tool, and workpiece during cryogenic machining. The influences of some important factors, including the shear deformation at primary zone, the friction at tool-chip interface, and the heat losses at both rake and flank faces of the tool caused by liquid nitrogen jetting, were all considered in the thermal model. The heat loss of rake face was divided into contact and non-contact zones to calculate the cooling effects at different positions. Heat partition ratios were utilized to modify the non-uniform distribution at tool-chip interface for all the heat sources and losses, respectively. The cutting parameters were optimized to avoid the low precision and efficiency of iterative algorithm. Cryogenic turning experiments were performed to verify the analytical model of temperature distribution. The results showed that the average errors of the predicted temperatures were lower than 3.30%.

Development of polyurethane foam incorporating phase change material for thermal energy storage

The major aim of the present study is to improve the thermal characteristics of polyurethane foams (PUFs) that have been almost exclusively used for thermal insulation purposes but can also play a role in potential thermal energy storage components as a matrix material.To overcome the low thermal conductivity of the of PUFs matrix, a synthesized phase change material (PCM) based on paraffin and calcium carbonate (CaCO3) has been developed to enhance the thermal conductivity and thus achieve a more effective charging and discharging process. The synthesized PCM (PCM@CaCO3) exhibited a good phase change performance with significant thermal storage capacity and thermal stability compared to commercial based PCM (PCM@BASF).Different PUFs formulations incorporating PCM (PCM@CaCO3 and PCM@BASF) were used to produce PUFs panels (rigid and soft PUFs panels). The thermal conductivity of the PUFs panels was measured using the transient plane heat source method (HotDisk Analyser, TPS 2500 S) and the thermal flux metre method (steady-state method). The results obtained revealed that, regardless of the method used, the thermal conductivity profile has a similar increasing trend before and after the bounds of the PCM phase change transition zone, whilst during PCM phase transition both methods showed a decreasing trend of the thermal conductivity as the temperature increased.In addition, this work presents and discusses the limitation of the HotDisk method to analyse panels composed by multilayers.

Prediction model of bone drilling temperature based on heat source method in surgical rehabilitation

Abstract In order to feedback the cutting temperature in real time during the operation with the surgical robot, this study established a temperature prediction model to analyze the temperature distribution of the cortex. In this work, a three-dimensional governing equation for heat transfer of bone tissue during drilling is proposed, and the heat transfer of cortical bone is evaluated by a reverse heat transfer method. The prediction model was validated by experimental methods and the heat affected zone (HAZ) of cortical bone was analyzed. The results show that the prediction results are in good agreement with the relevant experimental results. HAZ increases with increasing rate of penetration; the closer the bone hole is, the earlier the temperature rises; and the temperature at which the cortical bone is difficult to measure (radial distance x

Effect of climatic conditions on the thermal conductivity of earth fuller

The present work deals with the study of the effect of temperature on the thermal conductivity of Earth Fuller (Bentonite Clay) at different climatic conditions. First of all Earth Fuller brought from Barmer and Jodhpur were ground to fine-grained particles using a grinder and than micron size particles were obtained using the sieves of 186 µm, 150 µm, 125 µm, and 106 µm. The transient line heat source method based KD2 Pro Thermal Analyzer has been used to measure the thermal conductivity of the prepared samples in the temperature range from 10 to 70 °C. It was observed that at a fixed temperature, the thermal conductivity increases up to 40% (samples from Barmer) and up to 30% (samples from Jodhpur) with the increase in the particle size. Results exhibit that the thermal conductivity of the same sized particles of Earth Fuller at the same temperature is different due to varying climatic conditions. Whereas the temperature was increased from 10 to 70 °C, the thermal conductivity of the same sized particles also increases by nearly 20%.

An Experimental Study on Fiber Bragg Grating-Point Heat Source Integration System for Seepage Monitoring

Monitoring results of the linear heat source (LHS) method are generally affected by infiltration angle. In order to solve this problem, a novel point heat source (PHS) seepage integration system was designed in this study based on the spherical symmetry of PHS. Each sensing-heating element consisting of a fiber Bragg grating (FBG) temperature sensor, and a ceramic heating tube was enclosed in a copper tube. Several sensing-heating elements that were arranged in series in a monitoring tube, a regulated power supply, and a FBG demodulator constituted the PHS seepage monitoring system. Calibration tests were carried out under different magnitudes and directions of seepage velocity. The proposed PHS seepage monitoring system effectively eliminated the influences of infiltration angle. The magnitude of the seepage identification index (ξ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">v</sub> ) maintained a certain correlation with seepage velocity. Finally, a scheme for improving the sensitivity of the proposed monitoring system was discussed.

Performance investigation of convective and radiant heat removal methods in large spaces

Reducing the energy used for removing heat from solar radiation, high-temperature walls and air infiltration is becoming increasingly important in large space buildings. This paper proposes an analysis method to distinguish the performances of different heat removal methods in raising the cooling efficiency as well as reducing the heat flux. Firstly, the features of heat sources in large spaces are identified and proper parameters (heat flux or temperature) are selected to reflect their characteristics in heat transfer. Based on the goals of maximizing the cooling temperature and minimizing the heat flux, the influencing coefficients are defined to evaluate the influences or active forces of each type heat source and removal method on indoor environment and heat flux, and a simplified analysis model is established to reflect the character of different heat removal processes in large spaces with equivalent thermal resistance. On this basis, the influences of heat sources on indoor environment and the active forces of heat removal methods (e.g., jet ventilation and radiant floor cooling) are weighted quantitatively. By comparison, when the radiant floor cooling method is adopted, the operative temperature influencing coefficients that correspond to solar radiation and high-temperature envelope are lower than those in the case of jet ventilation, and the heat flux influencing coefficients are also smaller due to relatively lower degree of vertical air mixing. Therefore, radiant floor cooling method is more suitable for large spaces for its specialty in handling the heat from solar radiation and high-temperature envelope.

Characterization and modelling of density, thermal conductivity, and viscosity of TiN–W/EG nanofluids

Thermal conductivity, dynamic viscosity, and density of TiN nanofluids (NFs) with different base mediums have been characterized for the prospect of developing new thermophysical property correlations in this work. Characterizations of morphology and crystal structure of nanopowder were made using scanning electron microspore and X-ray diffractometer. Set of NFs was prepared in a base liquid mixture of water–ethylene glycol W/EG 60:40 and 40:60 by an ultrasound-assisted two-step method. Meter Group KD 2 Pro analyzer operated on transient line heat source method was used for the thermal conductivity test. The viscosity and density of NFs were measured with Anton Paar rotational rheometer MCR 302 and oscillating densimeter DMA 4500M. All experiments were implemented for volume fractions of NF between 0.25 and 1.0 vol% in the temperatures range of 293.15–333.15 K. The findings indicate that density and viscosity decrease with increasing temperature, whereas the thermal conductivity of nanofluids is enhanced depending on NP concentration. The W/EG 60:40 base mixture exhibited higher thermal conductivity enhancement and 40:60 base mixture had greater viscosity growth among all analyzed NFs. Moreover, the difference in base fluid fractions does not lead to a significant variance in the density ratios of NFs. Empirical correlations developed for examined properties with effects of particle concentration, temperature, and base liquid ratio are capable of accurately reproducing the properties data within 15% deviation.

The influence of infiltration angle on the identification effect of seepage with linear heat source method

The linear heat source (LHS) method is an effective way to realize large-range and distributed monitoring of seepage. Research on this method, however, fails to consider the influence of seepage direction. Based on the seepage mechanics and heat transfer theory, this article sets up a mathematical model to describe the heat dissipation process of LHS in porous media. On such basis, the finite element method was adopted to study the influence of seepage velocity and seepage direction on the law of heat dissipation of LHS. The results showed that the heat dissipation process of LHS meet well with Newton’s Law of Cooling. Its cooling velocity was in positive correlation with the seepage velocity and infiltration angle. Hence, when the seepage direction is unknown, adopting this method for seepage identification is uncertain, may leads to misjudgment. At the end of the paper, the authors discuss a solution to this problem.

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.

Study on thermal field in fly-cutting process of DKDP crystal

As an important nonlinear optical material, deuterated potassium dihydrogen phosphate (DKDP) crystal is used in laser beams as the core element of inertial confinement fusion. The most general method to produce smooth and crack-free DKDP surface is single point diamond fly-cutting (SPDF). However, the phase-changed temperature of DKDP is only about 120 °C which could be exceed in fly-cutting process. To analyze temperature field in cutting process, the formula based on the heat source method was introduced to calculate the temperature values on tool rake face under different cutting speed in DKDP crystal cutting process; then, thermo-mechanical FE analysis under the same process parameters was carried out to simulate the distribution of temperature field. The calculation and simulation results are basically in agreement, and the conclusion can be deduced: as the cutting speed increases, the temperature in the cutting zone increases, the highest temperature under common cutting parameter is up to 140 °C, which is validated by the dynamic infrared camera; however, the cutting temperature growth rate decreases with the same trend. The experiment results indicate that the chip morphology appears small spherical structure at high cutting speed, which illustrates the great possibility that the temperature exceed the phase transition temperature.

Minimization of Measurement Errors of the Coefficients of Heat Conductivity and Thermal Diffusivity of Thermal Insulating Materials by the Plane Pulsed Heat Source Method

Mathematical models have been developed for the calculation of measurement errors of the coefficients of the heat conductivity and thermal diffusivity of thermal insulating materials. A technique for selection of the following optimal parameters was created, based on models: duration of the heat pulse and the chief structural dimensions of the measuring device. Optimal conditions for applying the algorithm for processing the experimental data were also defined.

Limiting speeds of high-speed ball bearings considering prevention of skidding and overheating conditions

Based on quasi-dynamic and moving heat source methods, this article presents a new model to investigate skidding and overheating in ball bearings considering dynamic-thermal coupling effect. Using this model and finite element method, the critical minimum loads for prevention of skidding and the critical maximum loads for prevention of overheating are obtained by the developed software. The limiting speeds of high-speed ball bearings are defined considering prevention of skidding and overheating conditions. Results show that a smaller initial contact angle, oil lubrication, and hybrid ceramic bearing can enlarge the limiting speeds of angular contact ball bearings. Experiments prove the reliability of the method in this article.

Experiment and Analysis of Thermal Conductivity of Marine Concrete with Different Composition

The thermal conductivity and porosity of marine concrete with different composition were measured by transient plane heat source method. The effects of aggregate volume fraction, sand ratio and water-cement ratio on thermal conductivity of marine concrete were investigated. Through the analysis of these factors and the comparison with other scholars, it is found that the thermal conductivity of marine concrete increases with the increase of aggregate volume fraction, decreases with the increase of sand ratio and water-cement ratio.

Toward the temperature distribution on ball bearing inner rings during single-grit grinding

The paper studies the post-grinding temperature distribution on the inner ring of ball bearing 7008C. A grinding model was proposed to calculate the temperature distribution using the finite element method. The grinding process was simplified based on abrasive grain grinding motion. Our calculation takes account of the non-linear variation in physical properties of the bearing material as the temperature changes and the effects of convective heat transfer in the surrounding environment. A rectangular heat source and cyclic loading method were used to simulate the energy input during grinding, and the grinding temperature fields under different processing parameters were obtained. The calculated temperature fields are in good agreement with experimental results. The proposed model was then utilized to analyze the influence of different processing parameters on the temperature distribution, providing a basis for predicting the phase change and analyzing the post-grinding residual stress. Through processing parameter adjustments, the optimal parameter combinations that do not lead to material phase changes were identified. We hope this analysis will shed some light on the optimization of the bearing grinding process.

An improved analytical model of cutting temperature in orthogonal cutting of Ti6Al4V

Cutting heat has significant effects on the machined surface integrity of titanium alloys in the aerospace field. Many unwanted problems such as surface burning, work hardening, and tool wear can be induced by high cutting temperatures. Therefore, it is necessary to accurately predict the cutting temperature of titanium alloys. In this paper, an improved analytical model of the cutting temperature in orthogonal cutting of titanium alloys is proposed based on the Komanduri-Hou model and the Huang-Liang model. The temperatures at points in a cutting tool, chip, and workpiece are calculated by using the moving heat source method. The tool relief angle is introduced into the proposed model, and imaginary mirrored heat sources of the shear plane heat source and the frictional heat source are applied to calculate the temperature rise in a semi-infinite medium. The heat partition ratio along the tool-chip interface is determined by the discretization method. For validation purpose, orthogonal cutting of titanium alloy Ti6Al4V is performed on a lathe by using a sharp tool. Experimental results show to be consistent well with those of the proposed model, yielding a relative difference of predicted temperature from 0.49% to 9.00%. The model demonstrates its ability of predicting cutting temperature in orthogonal cutting of Ti6Al4V.

Применение модернизированного метода тепловых источников Фурье в случае поперечного полосового поверхностного нагрева и охлаждения трубы

Применение модернизированного метода тепловых источников Фурье в случае поперечного полосового поверхностного нагрева и охлаждения трубы

Оптимизация метода линейного импульсного источника теплоты и основного конструкционного размера устройства для измерения теплофизических свойств твердых материалов в целях улучшения деятельности в системе менеджмента лаборатории

Оптимизация метода линейного импульсного источника теплоты и основного конструкционного размера устройства для измерения теплофизических свойств твердых материалов в целях улучшения деятельности в системе менеджмента лаборатории

Predictive Model for Thermal and Stress Field in Selective Laser Melting Process—Part II

Finite Element Analysis (FEA) is used to predict the transient thermal cycle and optimize process parameters to analyze these effects on deformation and residual stresses. However, the process of predicting the thermal history in this process with the FEA method is usually time-consuming, especially for large-scale parts. In this paper, an effective predictive model of part deformation and residual stress was developed for accurately predicting deformation and residual stresses in large-scale parts. An equivalent body heat flux proposed from the single layer laser scan model was imported as the thermal load to the layer by layer model. The hatched layer is then heated up by the equivalent body heat flux and used as a basic unit element to build up the macroscale part. The thermal history and residual stress fields of two solid parts with different support structures during the SLM process were simulated. Layer heat source method has the capability for fast temperature prediction in the SLM process, while sacrificing modeling details for the computational time-saving purpose. Thus numerical modeling in this work can be a very useful tool for the parametric study of process parameters, residual stresses and deformations.

Evonik expands capacities for hydrophobic fumed silica

Ice bonded abrasive polishing (IBAP) is a novel polishing method that employs a frozen slurry of water and abrasives as a polishing tool. This process is capable of producing ultra-fine finish on metallic as well as on non-metallic (ceramic) surfaces. The enhancement of productivity and efficiency of the process depends on the characteristics of the IBAP tool. During polishing, the IBAP tool melts due to frictional heat generated at the tool and workpiece interface. The melting rate influences the tool life and is one of the crucial aspects of the IBAP tool design. The present study aims to develop an analytical model to predict the melting rate of the tool as a function of abrasive properties, applied pressure, the relative velocity between the tool, and the workpiece surface. This model considered Jaeger's moving heat source method (1942) to determine the rise in temperature of tool and workpiece interface at steady-state and Blok's postulation (1963) to determine the fraction of heat conducted into the tool. The estimated melting rate of the IBAP tool is compared with the experimental data obtained from the reduction in the height of the IBAP tool at the polishing zone.

Modelling of temperature distribution in the work material during drilling under sustainable environment

The knowledge of temperature distribution on the work material is essential to incorporate various sustainable techniques like dry and near dry machining. A new approach of the thermal model during dry drilling process has been established to predict the magnitude and distribution of machining-induced work material temperature. Here the classical heat source method was adopted. In the present work the contact point between the cutting edge of the drill tool and the work material is represented as a line heat source inclined at an angle, moving with a velocity. The temperature rise due to chip clogging, built-up edge formation and friction is neglected in the present model. The plots from the investigation revealed that the temperature increased with higher values of Peclet number which is a representation of the relative velocity of the heat source and the thermal properties of the conduction medium. Also, it is observed that the angle of inclination of heat source has little influence on the temperature rise at lower velocity. The model provides a cohesive basis to deal with the temperature rise in the workpiece during the dry drilling process. By using the model temperature distribution at any point on the work material can be obtained. To validate the analytical results experiments were carried keeping the cutting speed constant and varying the feed rate to measure the work material temperature rise using an infra red camera. The measured temperature during the experiment was found to be higher than the predicted temperature since some of the relevant factors like built-up edge formation, chip clogging and increase in friction were not considered in the model. Also further investigation is necessary to find the influence of point angle on the developed model.