Temperature Field Distribution Research Articles

Numerical simulation of physical field during different ultrasonic power assisted casting of 7085 aluminum alloy

High‐energy ultrasound has the effect of purifying the aluminum (Al) melt and improving the uniformity of temperature and flow field distribution. In this paper, a finite element numerical model of ultrasonic‐assisted casting of 7085 Al alloy melt was established, and the changes of acoustic pressure field, temperature field and flow field in the solidification process of alloy melt with different ultrasonic power were investigated. The numerical simulation results show that the thickness of the 7085 Al melt mushy zone decreases by 89 mm, 97 mm, 108 mm, 114 mm and 99 mm, respectively, compared without ultrasonic (WNU) when the ultrasonic power was 150 W, 350 W, 550 W, 750 W and 950 W. The area of the alloy mushy zone increases by 38.1%, 43.5%, 61.0%, 206.5% and 45.6%, respectively. According to numerical simulation results, when the ultrasonic power was 750W, it had the best effect on improving the macroscopic physical field, increasing the mass and heat transfer rate in the center of the Al melt. Meanwhile, the experimental results of industrial melting and casting of 7085 large‐scale Al alloy ingots were basically consistent with the numerical simulation, which provided technical support for ultrasonic‐assisted fabrication of large‐scale 7085 Al alloy ingots.This article is protected by copyright. All rights reserved.

Cylindrical gear transmission errors influenced by temperature based on thermal network

Gear transmission errors are influenced by temperature especially in the aerospace field. A model is proposed to investigate the influence of temperature on cylindrical gear transmission errors based on the thermal network (TETN). The gear temperature field distribution model is established based on the thermal network method, and gear thermal deformation can be calculated along the gear meshing line. Regarding the gear single-flank rolling process, the variation of gear transmission errors under temperature is determined. In numerical calculations in MATLAB, the variation of gear transmission errors at 100°C compared to 20°C is –4.20 μm, which decreases almost linearly while the thermal expansion coefficient of the gear material increases. The simulation of the gear transmission errors variation of temperatures using the finite element method (FEM) were carried out in Workbench software under Ansys and the average difference of the TETN model results between calculations and FEM for different temperatures was 0.24 μm. Experiments were carried out on the gear tester in temperatures ranging from 0°C to 100°C, the TETN model results in calculations were compared with the results of the tester, and the average difference was –1.15 μm. The results show that the proposed TETN can be used as an algorithm to determine the variation of gear transmission errors under the influence of temperature.

An analysis of temperature control for electromagnetic induction heating of CFRP based on sparrow search algorithm

Accurate temperature control during the induction heating process of carbon fiber reinforced polymer (CFRP) is crucial for the curing effect of the material. This paper first builds a finite element model of induction heating, which combines the actual fiber structure and resin matrix, and systematically analyzes the heating mechanism and temperature field distribution of CFRP during the heating process. Based on the temperature distribution and variation observed in the material heating process, a PID control method optimized by sparrow search algorithm is proposed, which effectively reduces the temperature overshoot and improves the response speed. The experiment verifies the effectiveness of the algorithm in controlling the temperature of CFRP plate during the induction heating process. This study provides an effective control strategy and research method to improve the accuracy of temperature control in the induction heating process of CFRP, which helps to improve the results in this field.

Temperature field reconstruction based on femtosecond laser prepared of multiwavelength fibre bragg grating array

Temperature field measurements are of great significance in industrial production, scientific research, and other fields. Contact temperature measurements usually achieve high spatial resolution by increasing the layout density of the sensors. However, in practical applications, achieving high-density sensor placement is often difficult. Therefore, when the number of sensors is limited, it is necessary to perform function fitting or interpolation of the temperature of the sampling points to reconstruct the temperature field distribution. This study proposed a temperature field reconstruction method based on femtosecond laser prepared multiwavelength fibre Bragg grating (FBG) array. A multiwavelength FBG array was prepared using the femtosecond laser phase mask method combined with stress stretching, and applied for measuring the temperature field distribution in a tubular high-temperature furnace. Cubic spline interpolation and backpropagation (BP) neural networks were used to construct two-dimensional temperature field models for the temperature field distribution data measured by the FBGs, and the prediction accuracies of the two models were compared. The test results show that the root mean square error of the temperature field distribution constructed using the BP neural network is 0.7333 °C, which is approximately 23.18% of the predicted results of the cubic spline interpolation model, indicating that it is a high-precision temperature field reconstruction method.

Representation of Thermomechanical Damage in Fiber-Reinforced Ceramic Composites at High Thermal Gradients

Ceramic matrix composites (CMCs) are the core strategic materials for the thermal structure of new-generation hypersonic aircraft. The unclear understanding of the cross-scale thermomechanical behavior and failure mechanism of materials and structures in high-temperature transient environments is a key scientific issue that restricts the reliable design and safe operation of hypersonic aircraft. In this study, a high-temperature test module in a supersonic wind tunnel with integrated various test systems was independently designed to systematically investigate the thermal mechanical damage evolution of CMCs used in astronautics applications under high-temperature transient conditions. Furthermore, a numerical method for fluid-heat-solid coupling based on an iterative solution strategy was developed and compared with an algorithm based on a wall modification strategy in terms of computational efficiency and accuracy. Besides, a comparative analysis was conducted with the temperature field distribution of the sample obtained in the hypersonic wind tunnel integration test to verify the correctness of the developed thermal-fluid-solid coupling calculation method. Finally, through thermoelastic coupling computational models, the high-thermal-gradient-induced thermomechanical damage mechanism of the CMCs was revealed, providing support for further optimizing the material system and thermal structure design of the CMCs.

Theoretical prediction of soft-forming micro-hemispherical shells from fused silica substrates in reclining mold

Abstract A reclining mold can support the soft forming of fused silica substrates into micro-hemispherical shells with the same height, which makes the processing of micro-hemispherical shells attractive. Currently, it is difficult to determine the optimal process parameters for machining micro-hemispherical shells, and several iterations of experiments are required. This process wastes large amounts of substrate material, experimental consumables, and machining time, and increases the cost of the experiments. In this paper, we report a reflow process for soft-forming micro-hemispherical shells from fused silica substrates supported by a reclining mold. The shapes of the shells formed from the fused silica substrates in reclining and non-reclining molds were analysed by building a two-dimensional model. Moreover, we predicted the effects of varying the process parameters on the shell-forming time and geometrical parameters, as well as the stresses and deformations of the shells after cooling. The effect of the eccentricity of the central support column of the mold on the symmetry of micro-hemispherical shells was also investigated, and the influence of the mold and substrate heating inhomogeneity on micro-hemispherical shell formation was analysed. Additionally, the heat uniformity of the substrate in the rotating state was examined. Finally, we investigated the temperature field and thickness distribution during the shell-forming process through 3D modelling to verify the 2D modelling results. Analysing and predicting the parameters helps to reduce the number of trial-and-error processes in experiments, and we expect this work to provide a theoretical parametric basis for micro-hemispherical shell machining.

Study of hydrothermal characteristics of large‐scale water conveyance trunk canals in seasonally frozen ground regions under the influence of different initial water contents

AbstractIn seasonal frozen soil, freezing and thawing can change the physical and mechanical properties and affect slope stability. There are complex moisture conditions in the main water transfer canal. A study of the hydrothermal evolution of canals with different initial water contents under the action of freezing and thawing is of great importance for the prevention and control of canal slope slides. Hydrothermal coupling models are the key to revealing the canal's hydrothermal evolution. As some of the modeling parameters in the current hydrothermal coupling model are based on empirical values, particularly those in the van Genuchten equation, which are not necessarily related to soil properties, they are not suitable for analyzing the hydrothermal evolution of canals. This paper determines the soil‐water characteristic curve from the cumulative curve of particle gradation in the subsoil, and then determines the hydraulic parameters of the subsoil using the VG model, which then corrects the hydrothermal coupling model. The method of modifying the hydrothermal coupling model is original, which makes the model more realistically reflect drainage soil characteristics. During freezing and thawing of channel slopes with different initial water contents (21%, 25%, 29%, 33%, 37%, and 41%), temperature field, water field, and ice content distributions were investigated. Using the V‐G model, the optimal parameters for canal subsoil were a = 0.06, n = 1.2, and m = 0.17, and temperature distribution trends between canals with different water contents were basically similar. Water will accumulate at the bottom as the liquid water content increases at the canal boundary.

Experimental study on upward fire spread of polyurethane foam under double fire source conditions with different restricted facade Structures

This paper examines the impact of insulation material (PU) fire spread characteristics under dual fire source conditions considering various restricted facade Structures. It is found that the merging tendency is affected by the flame inclination angle θ1 and mapping length L. Additionally, the flame merging behavior is determined by the combined effects of the chimney effect, inter-flame air entrainment, and heat transfer changes caused by the restricted angle. The Inter-flame air entrainment λ was introduced to confirm that there is a positive correlation between flame height and Inter-flame air entrainment in the large-angle restricted facade Structures (θ=120°,150°，180°). By introducing the hydraulic diameter Deff* to compare the experimental data with the previous flame pulsation frequency model, the proposed f=0.5g/Deff* model can further improve the accuracy of the prediction results. During the flame merging stage, the axial temperature field distribution on the PU board surface was compared. The study found that the restricted facade Structures resulting in a cooling effect due to fresh air entrainment at the bottom with the chimney effect. As a result, the small-angle restricted facade Structures (θ=30°，60°，90°) led to an upper-high and lower-low distribution of axial temperature.

Investigation of temperature effects on wide steel box girder of suspension bridge based on long-term monitoring data

The time-varying temperature distributions on bridge structures may remarkably change structural performance, which may result in differential strain/stress responses on structural members compared with the design conditions. Therefore, it is crucial to have a comprehensive understanding of temperature distributions and its effects on bridges. In this study, taking advantage of structural health monitoring technology, 1-year field monitoring data collected from a long-span suspension bridge were used to investigate the temperature distributions and their effects on the steel box girder. Specifically, the distributions and probability statistics of temperatures on the top and bottom plates were firstly analyzed. Based on which, the transverse and vertical temperature differences on the box girder were further examined, moreover, the representative values of temperature differences for various return periods were calculated by exceedance probability method. At end, a temperature prediction method was proposed to simulated the temperature field distributions during bridge life cycle, to provide substantial temperature data for estimating future operation condition. The results of this study were beneficial to structural evaluation of in-service bridges to ensure their serviceability and integrity in the life cycle.

Investigation of collagen reconstruction mechanism in skin wound through dual-beam laser welding: Insights from multi-spectroscopy, molecular dynamics simulation, and finite element multiphysics simulation

Since the mechanism underlying real-time acquisition of mechanical strength during laser-induced skin wound fusion remains unclear, and collagen is the primary constituent of skin tissue, this study investigates the structural and mechanical alterations in collagen at temperatures ranging from 40 °C to 60 °C using various spectroscopic techniques and molecular dynamics calculations. The COMSOL Multiphysics coupling is employed to simulate the three-dimensional temperature field, stress-strain relationship, and light intensity distribution in the laser thermal affected zone of skin wounds during dual-beam laser welding process. Raman spectroscopy, synchronous fluorescence spectroscopy and circular dichroism measurement results confirm that laser energy activates biological activity in residues, leading to a transformation in the originally fractured structure of collagen protein for enhanced mechanical strength. Molecular dynamics simulations reveal that stable hydrogen bonds form at amino acid residues within the central region of collagen protein when the overall temperature peak around the wound reaches 60 °C, thereby providing stability to previously fractured skin incisions and imparting instantaneous strength. However, under a 55 °C system, Type I collagen ensures macrostructural stability while activating biological properties at amino acid bases to promote wound healing function; this finding aligns with experimental analysis results. The COMSOL simulation outcomes also correspond well with macroscopic morphology after laser welding samples, confirming that by maintaining temperatures between 55 °C–60 °C during laser welding of skin incisions not only can certain instantaneous mechanical strength be achieved but irreversible thermal damage can also be effectively controlled. It is anticipated that these findings will provide valuable insights into understanding the healing mechanism for laser-welded skin wounds.

An Electrochemical-Thermal Coupling Model Based on Two-Factor Parameter Modification for Lithium-Ion Battery

Abstract The accurate establishment of battery model can improve the design reliability and reduce the design risk, which provides an important basis for the research of battery. First, the key parameters of the Li-ion battery model are identified by the least square method based on the full-battery equivalent circuit model of the single-particle impedance spectrum, and the diffusion coefficient and exchange current density under different temperatures and SOC conditions are calculated. At the same time, the one-dimensional thermal rate model is used as the heat source of the three-dimensional model, and the mean temperature T of the three-dimensional model is calculated by using Fourier's law, and T is fed back to the one-dimensional model as the key parameter to modify the conductivity, diffusion coefficient, and exchange current density, and a semi-empirical electrochemical-thermal coupling model with two-factor parameter modification is established. Finally, the model is verified by the temperature field distribution and discharge voltage curve at different discharge rates. The maximum temperature difference is less than 3.1 °C, and the maximum voltage difference error is less than 0.131 V. The results show that the improved model can accurately reflect the influence of temperature on the model parameters, and has high accuracy in the estimation of battery terminal voltage and SOC.

High‐Temperature Thermal Conductivity of Fiber Hybrid Ceramic Matrix Composites with Different Modes

Thermal conductivity (TC) is one of the important thermal property evaluation parameters for high‐temperature‐resistant fiber‐reinforced composites. Herein, based on the flexible‐oriented three‐dimensional (3D) woven technology, fiber hybrid ceramic matrix composites (FH‐CMCs) with different hybrid modes are designed and fabricated by using carbon fiber and silicon carbide fiber. The representative volume element (RVE) models of fiber bundle and matrix with mesoscopic characteristics and the macroscopic RVE models with hybrid structure characteristics are established. The heat flux distribution and effective TCs of FH‐CMCs in the thickness and in‐plane directions at different temperatures are obtained by finite element analysis (FEA) and experimental tests. The results show that the FEA and experimental results of the TCs of different FH‐CMCs are in good agreement. In the range of 25–1000 °C, the effective TCs of FH‐CMC gradually decrease with the increase in temperature. The TCs in the thickness direction of different FH‐CMCs are directly proportional to the hybrid ratio, and the TCs in the in‐plane direction are inversely proportional to the hybrid ratio. The heat flux and temperature field distributions of the FH‐CMCs are mainly affected by the TCs of the components, fiber hybrid ratio, and orientation, and the distribution along different directions are obviously different. The research results are helpful to provide theoretical and experimental reference for the structural design and performance improvement of hybrid composites.

Compressible FSI of elastic spikes for drag reduction under hypersonic flow

In this study, a new fluid structure interaction (FSI) algorithm is developed for the aerodynamic-elasticity problem, aiming to address the coupling problem between compressible fluids and deformable solid structures. To verify the feasibility of the proposed model, a two-dimensional cantilever panel case under shock waves was conducted. Our numerical results present good consistency with the data from literatures. Furthermore, the validated FSI algorithm is applied on an elastic spike under compressible hypersonic flow. The complicated interaction between the fluid and solid structure under various spike geometry sizes and materials were revealed in respect of the spike deformation, pressure, temperature, and flow fields distribution. The main findings show that the spike deformation largely affects pressure and temperature on the blunt, the aerodynamic drag and lift force, indicating the necessity of FSI. For the spike diameters and lengths, it is found that larger spike diameters and shorter spikes benefits for deformation reduction, thereby minimizing fluctuations in aerodynamic drag force. For spike materials, spikes with larger elastic moduli and lower densities are preferred for the drag reduction. Thus, the proposed FSI model can accurately predict flow fields around and deformations for elastic spikes and offer guidance for drag reduction design in aerospace engineering.

Simulation and experimental study of the thermal characteristics of a high-speed motorized spindle

Based on the finite element simulation software ANSYS Workbench, this study reports the thermal characteristics of a high-speed motorized spindle. The temperature field distribution and axial thermal deformation of the motorized spindle are then detected on an experimental platform. A comparison between the experimental and simulation results revealed the temperature rise of the motorized spindle during the working process. Under steady-state conditions of the working mo-torized spindle, the temperatures of the front bearing, rear bearing and stator were determined as 20°C, approximately 30°C and 25°C, respectively. The axial thermal elongation of the motorized spindle is approximately 10 μm.

Numerical simulation on heat transfer characteristics during waste heat utilization after the underground in-situ pyrolysis of tar-rich coal

A large amount of pyrolysis residue is left in the coal seam after the in-situ pyrolysis of tar-rich coal, which contains rich heat energy. However, there are few numerical simulations on waste heat utilization from in-situ pyrolysis of tar-rich coal at present. This paper mainly focused on the temperature field distribution and heat transfer characteristics of the coal seam in the process of waste heat utilization of tar-rich coal in large spatial scale and over a long period. The effects of cooling medium type, cooling fluid velocity, cooling fluid temperature, fracture distribution and well pattern on temperature field distribution and heat transfer performance of tar-rich coal seam were analyzed by Fluent numerical simulation. The present study can offer theoretical guidance and technical support for large-scale utilization of residual heat from pyrolysis residue of tar-rich coal.

Coupling analysis of cylinder block for two-stroke aviation piston engine

The aluminum alloy block is a component of aircraft piston engine, and it is prone to fatigue cracks when working in a thermal mechanical coupling state for a long time. Establish a GT-POWER simulation model for a certain type of engine, verify the accuracy of the model, obtain boundary parameters such as temperature and pressure of the engine block under harsh operating conditions through the model, and divide the cylinder wall into gradients based on the engine operating conditions to obtain the surface heat transfer coefficient of the block, and then obtain the temperature field distribution of the engine body. The coupling analysis of the cylinder burst pressure and temperature field of the engine block under harsh working conditions showed that the maximum stress of the engine block was 292.55 MPa and the maximum deformation was 0.39 mm, with thermal load being the main factor causing deformation. Conduct a complete engine bench test, and under the 1000 h bench durability test, there are no cracks on the engine block, indicating that the design and analysis meet the requirements.

Study on fire temperature fields of air-supported membrane structures considering thermal–fluid–solid coupling and boundary correction

The study analyzed and compared the effects of thermal–fluid–solid coupling dynamic boundary conditions and traditional fixed-boundary conditions on the distribution of the temperature field under fires. The feasibility of simulating the temperature field distribution was confirmed by using thermal–fluid–solid coupling dynamic boundary conditions. Then, the traditional temperature field analysis methods were corrected by including a flow-based heat exchange coefficient, and the feasibility of this approach was also confirmed. The fire temperature field in a rectangular air-supported membrane structure was analyzed through parameterization. The fire temperature field model of the air-supported membrane structure was established using temperature field data fitting. Furthermore, the study explored the high-temperature material properties of P-type membranes and analyzed and compared the temperature field of the air-supported membrane structure with time-varying mechanical properties of the membrane material to that without time-varying properties.

Laser-induced damages to charge coupled devices with combined nanosecond/picosecond short-pulse lasers

The research on laser induced breakdown mechanism of charge coupled devices (CCDs) brings new insights into photoelectric countermeasures. So far combined laser irradiation has been proved to be a more effective measure to destroy CCD. Due to the limitation of short-pulse laser combination method, the mechanism of CCD damage caused by combined short-pulse laser remains unexplored. Here, the distribution of temperature and stress field during the interaction between a combined short-pulse laser and a CCD is analyzed. A nanosecond/picosecond combined short-pulse laser system based on Stimulated Brillouin Scattering (SBS) pulse compression technique is designed. The damage threshold (DT) and properties of CCD by combined laser irradiation are characterized. The results show that the complete DT of combined laser induced CCD breakdown is only 103 mJ/cm2, which is only 44% of that of picosecond laser. The main cause of combined short-pulse laser induced CCD breakdown is short circuit (SC) between silicon substrate and silicon electrode.

A Fast Method of High-Frequency Induction Cladding Copper Alloy on Inner-Wall of Cylinder Based on Simulation and Experimental Study

To quickly repair the inner-surface damage to the hydraulic support cylinder caused by frequent scratches, corrosion, and wear in the process of fully mechanized coal mining, this paper proposes a method of high-frequency induction cladding (HIC) copper alloy on inner-wall of cylinder (IWC) to improve the corrosion, sealing and pressure retention performance of hydraulic cylinders combined with numerical simulation and experimental study. Firstly, a numerical temperature field model for HIC of copper alloy on the IWC is established to investigate various distribution patterns and influencing factors including frequency of induction heating, gap between coil and cladding, power supply rating, cladding thickness and side length of square section of induction coil, etc. Subsequently, an HIC test experiment is conducted to rigorously validate the numerical temperature field model and the experiment employs a meticulously collected dataset of temperature measurements, confirming the model’s accuracy and consistent alignment with anticipated changing trends. In addition, the experiment results were verified through microstructure observation, microhardness testing, friction-wear testing, and electrochemical corrosion parameters, which shows that the factors of induction heating frequency and others have obvious effects on the temperature field distribution of HIC copper alloy on the IWC. Under these working conditions (cladding thickness 1.5 mm, power supply rating 120 kW, heating frequency 120 kHz, gap between the cylindrical workpiece and the induction coil 3 mm, induction coil cross-sectional side length of 10 mm), the thermal impact on the cylinder barrel matrix is minimal, the metallurgical bonding between the cladding layer and the matrix is good, and there are no over burning and porosity defects.

Graph convolution network-based surrogate model for natural convection in annuli

This work develops a model for natural convection in annuli with internal heat sources based on Graph Convolution Network (GCN), achieving rapid prediction by directly establishing the mapping relationship between the geometric features and the temperature field. The GCN learns node features and connections between nodes in data structures. Compared with traditional machine learning networks, GCN exhibits greater advantages in handling complex geometric shapes and unstructured nodes. In this study, numerous data samples were constructed with various geometric features, e.g., varying sizes, positions, and quantities of internal heat sources. The results indicate that a fully trained GCN was capable to adaptively predict temperature field distributions with arbitrary heat source sizes, positions, and quantities. The mean prediction errors of GCN for the temperature field are around 0.17 %, 0.32 %, and 0.85 %, for the single, double, and triple heat sources cases, respectively. Furthermore, the GCN prediction performance was also compared with surrogate models by the convolutional, and fully connected neural networks (CNN and FNN), which shows an improvement of 88.1 % and 84.8 %, respectively. Therefore, compared with numerical results and other surrogate models, the proposed model presents superior geometric adaptability, high prediction accuracy and a remarkable enhancement in computational efficiency (three orders of magnitude).