Thermal Finite Element Simulation Research Articles

A real-time temperature field prediction method for steel rolling heating furnaces based on graph neural networks

In the billet reheating process during steel rolling, the real-time and accurate prediction of the temperature field is a prerequisite for the dynamic regulation of the heating process, which is crucial for ensuring the quality of billet reheating and reducing the energy consumption of the reheating furnace. The most commonly used finite element thermal field simulation and analysis methods are unable to meet the demand for real-time prediction under dynamic working conditions. Furthermore, traditional machine learning methods struggle to handle irregular data that includes spatial location information, resulting in inaccurate temperature field predictions, which in turn affect the furnace control efficiency and the quality of the product. In light of these limitations, this study proposes a Graph Neural Network (GNN)-based temperature field prediction method for steel rolling reheating furnaces. This method considers the interactions between the nodes within the reheating furnace and constructs a temperature field topology graph to effectively capture these interactions, including heat conduction and convection. Additionally, in the feature fusion and state updating mechanism of the model, we introduce process parameters, such as the air-fuel ratio, as additional inputs to enhance the ability of the GNN to handle complex variables. This enables real-time accurate simulation of the internal temperature distribution of the reheating furnace. The experimental results demonstrate that the model prediction error is controlled within 2.9 % and the response time is maintained within 20 ms, thereby validating the reliability and efficacy of the method in practical applications.

Quantifying laser irradiation-induced temperature field of particle reinforced metal matrix composites

While particle-reinforced metal matrix composites (PMMCs) are composed of particles and matrix with distinctly different thermomechanical properties, the thermal differences and coupled interactions between individual phases greatly determine the thermal characteristics of PMMCs under laser irradiation. In this work, we quantify the temperature evolution characteristics within SiCp/Al under laser irradiation by microstructural thermal finite element simulations and experimental investigation. Specifically, a 2D thermophysical FE model of laser-SiCp/Al interaction for the two-phase PMMCs material under laser irradiation is developed, which incorporates the temperature-dependent thermophysical properties of particles, matrix and interfaces, along with the considerations of the shape and distribution characteristics of particles, as well as the comprehensive thermal conditions. Furthermore, a 3D equivalent thermal FE model for experimental validation of predicted laser-induced temperature of SiCp/Al is developed, based on the derived equivalent properties. Meanwhile, an in-situ temperature measurement system is constructed for exploring temperature evolution characteristics during the on-going laser irradiation process, which validates a derivation of 1.7 % of predicted temperature by the equivalent thermal FE model. Finally, the impact of laser processing parameters on the temperature field of SiCp/Al is addressed. These findings provide valuable insights for understanding the thermal mechanisms of PMMCs under laser irradiation, and also the parameter optimization for laser processing of PMMCs.

Analysis of the temperature rise process of carbon ceramic axle-mounted brake disc

Abstract At present, high-speed train braking modules gradually adopt carbon ceramic brake discs. Based on the calculation results, the temperature simulation calculation of carbon ceramic brake disc for high-speed trains is of important engineering reference value for design and application. This paper established a finite element thermal simulation model based on the material properties of carbon-ceramic composite materials and the size and structural characteristics of the brake disc, and conducted a simulation analysis of the 400km/h emergency braking condition. After calculation, the carbon ceramic disc surface temperature reaches about 1250°C during the braking process, which does not exceed the material limit of 1350°C, and can adapt to the braking requirements of high-speed trains. The evolution rules of the temperature field and temperature value changes of the carbon ceramic shaft-mounted brake disc were further studied, and the general rules of disc temperature changes during emergency braking at 400km/h were summarized. The relevant content can provide a reference for the thermal analysis research of carbon ceramic axle-mounted brake disc.

Experimental study of Double-Elliptic-Ring-based thermomechanical metamaterials’ behaviour

In recent years there has been increased interest in 3D thermomechanical metamaterials. The current work reports the design, fabrication and testing of a novel anisotropic anepectic metamaterial obtained by grafting inserts of a second material into a known auxetic structure, the Double Elliptic Ring (DER). While auxetics have a Negative Poisson's Ratio (NPR), anepectics combine this with a negative coefficient of thermal expansion (NTE). To avoid unnecessary time and material expenditure during the additive manufacturing (AM) stage, mechanical and thermal finite element simulations (FEA) were used as a tool to screen the multitude of possible design variants under consideration, thus aiding in rapidly determining the more promising geometries. To further increase the efficiency during AM, the selected structures were then assembled from planar elements, joined together with an adhesive. In the end, through the combination of two conventional materials – PVA and Nylon – of positive Poisson's ratio (PR) and coefficient of thermal expansion (CTE) organized in the DER architecture, it was possible to achieve the desired NPR and CTE behaviour along some directions, coupled with positive values in other directions. Experimental results revealed a correlation between PR values and the number of cells in the structure and showed that, while NPR values are essentially determined by the metamaterial's geometry, the induction of NTE results from a subtle interaction of geometry and the properties mismatch between the constitutive materials.

High-temperature thermal fatigue of Ni3Al-based single crystal alloy affected by wall thickness and peak temperature

Complex thin-walled structures are commonly employed in turbine components to improve cooling efficiency. However, thin-walled blades are prone to thermal fatigue failure due to the high thermal stress induced by frequent and abrupt temperature fluctuations during duty cycles. The thermal fatigue behavior of Ni3Al-based single crystal alloy with thin-walled structure during 25 °C ↔ 1000 °C/1100 °C was investigated by combining thermal fatigue tests and finite element simulation. The thermal fatigue demonstrated a significant thickness debit effect, with thermal fatigue property dropping as peak temperature and wall thickness increased. Wall thickness had a more pronounced effect than peak temperature. Visible slip traces were found on the wall thickness surface, and their density was positively correlated with wall thickness. Further investigation revealed that thermal fatigue is primarily driven by the octahedral slip system ({111}<110>), with significant contributions from (111)[101‾] and (1‾1‾1)[101]. Simulations of thermal stress distribution and J-integral at the crack tip during crack initiation and propagation stages indicated that wall thickness influences thermal fatigue properties by affecting thermal stress concentration at the notch and crack tip. Higher peak temperatures increased thermal stress and reduced yield strength, thus diminishing thermal fatigue performance. A thermal fatigue crack propagation prediction model was constructed incorporating Paris' law and the J-integral. The model revealed an unfavorable correlation between material Cj/ nj and both peak temperature/wall thickness, indicating that both factors adversely affect thermal fatigue resistance.

Temperature-dependent creep damage mechanism and prediction model of fiber-reinforced phenolic resin composites

Carbon fiber-reinforced phenolic resin (CF/PF) and glass fiber-reinforced phenolic resin (GF/PF) composites are crucial for thermal insulation and load-bearing capabilities in the aerospace industry. Understanding their creep behavior at various temperatures is essential. This study investigates the impact of temperature on the bending creep properties of CF/PF and GF/PF composites, focusing on deformation response, damage mechanisms, and prediction models. Results reveal that the decrease in creep properties at elevated temperatures is mainly attributed to the increased viscoplastic strain. At room temperature, CF/PF composite demonstrates exceptional creep properties. CF/PF composite exhibits heightened sensitivity to elevated temperatures, undergoing creep rupture at 210 °C and 240 °C with failure strains of 0.48 % and 0.49 %, respectively. High-temperature damage mechanisms have been analyzed in depth using a combination of thermal stress finite element simulation and microscopic characterization. Thermal stress is directly related to the difference in thermal expansion between the fibers and the resin. The influence of fiber distribution and geometry results in the interface being subjected to both normal and shear stresses. The accumulation of interfacial damage increases the plastic deformation and degrades creep performance. Additionally, an advanced temperature-dependent Burgers model has been developed and effectively predicted the creep curves under different temperatures and loads. This model demonstrated great potential as a general predictive model.

Thermal finite element modeling and simulation of a squirrel-cage induction machine

Finite element models of electrical machines allow insights in electrothermal stresses which endanger the insulation system of the machine. This paper presents a thermal finite element model of a 3.7 kW squirrel-cage induction machine. The model resolves the conductors and the surrounding insulation materials in the stator slots. A set of transient thermal scenarios is defined and measured in the machine laboratory. These data are used to assess the finite element model.

Nonlinear dynamic separation characteristics of friction pair and experimental analysis

This paper aims to reduce friction pair erosion of the clutch in the case of continuous shift; the dynamic separation process of the friction pair is investigated. The temperature of the friction pair, friction torque, and separation speed in the separation process are taken as the research objects, and the dynamics simulation model and finite element thermal coupling simulation model of the clutch separation process are established. The nonlinear dynamic separation characteristics of the friction pair are investigated by comparing and analyzing the effects of control parameters such as rotational speed difference, damping ratio, and lubricant viscosity on the friction torque, friction pair separation speed, separation gap, and contact stress during the separation process. The gap recovery coefficient is proposed as a response indicator for observing the separation process in response to the inability to observe the nonlinear dynamic motion of the friction pair during the separation process and to measure the end time of the separation. Finally, the clutch was subjected to a separation test. The results show that the proposed gap recovery coefficient accurately describes the separation process. The simulation model can simulate the clutch's separation and predict the trend of separation parameters.

Simulation-based process parameter optimization for wire arc additive manufacturing

AbstractDuring manufacturing of components using wire arc additive manufacturing, specific cooling times are required to prevent overheating of the structure and geometrical distortions. Currently, these cooling times are inserted based on experience at certain interlayer temperatures — which reduces the reproducibility, leads to unwanted component properties, and increases the process time. In this contribution, instationary thermal finite element simulations are applied to compute the temperature evolution of additively manufactured components using the inactive element method. This allows to optimize the process parameters, which are — in our considerations here — the welding velocity and the cooling time of each layer, to reduce the total process time while achieving sufficient component properties. The optimization is carried out with the gradient-free Nelder–Mead simplex algorithm, where certain constraints of the process parameters are considered via penalty functions. To obtain reasonable simulation results, the temperature-dependent heat transfer of the experimental setup is modeled and calibrated with experimental data beforehand. It becomes apparent that thermal finite element simulations combined with a gradient-free optimization procedure are a suitable numerical tool to perform the optimization of process parameters for wire arc additive manufacturing. The optimized process parameters fulfill certain requirements regarding the cooling of the manufactured component. Moreover, the optimized parameters can significantly reduce the process time compared to manually chosen parameters. In our example, this is around 48 %.

Construction of AlN oriented skeletons using in-situ reaction strategy and their enhancement effect on the thermal conductivity of epoxy composites

The development of electronic devices towards miniaturization and integration has put forward higher requirements for polymer-based composites with high thermal conductivity (TC). Aluminum nitride (AlN) is one of the most promising fillers thanks to its high TC (∼320 W m−1 K−1) and outstanding physicochemical properties. However, the traditional composites filled with randomly dispersed AlN particles generally require extremely high filling fraction to enhance the TC, leading to increased production cost and degraded mechanical performance. To address this issue, an innovative strategy combining freezing casting and in-situ reaction process was proposed to directly construct vertically aligned AlN skeletons, which was further used as reinforcements to enhance the TC of epoxy (EP) composites. The close arrangement of AlN particles along the vertical direction was not only beneficial for enhancing the TC, but also improving the mechanical strength. The AlN/EP composites achieved an extremely high TC of ∼8.25 W m−1 K−1 at the AlN filling fraction of 56.2 vol%, which was 45.83 times higher than that of pure EP. The actual thermal management applications and finite element simulations also demonstrated the oriented AlN skeletons exhibited a more significant TC enhancement than that of randomly arranged AlN. Furthermore, the as-prepared AlN/EP composites also exhibited superior thermal stability and dielectric properties, presenting a broad application prospect as thermal management materials for the next-generation electronic devices.

Design and Analysis of an H-Type Pickup for Multi-Segment Wireless Power Transfer Systems

To tackle the complex wireless power supply requirements in the Automated Material Handling System (AMHS) of semiconductor wafer factories, this paper presents a design method for a magnetic coupling mechanism based on a Multi-Segment Wireless Power Transfer (MSWPT) system for dynamic wireless power supply in segmented track configurations. Firstly, the track is approached using Inductive Power Transfer (IPT) technology combined with an LCC-S resonant structure transmitter (Tx). Following this, the feasibility of the H-type pickup is assessed through magnetic and electrical circuit analyses, which leads to the preliminary determination of the pickup dimensions by means of finite element magnetic and thermal simulations. Furthermore, an analysis of the mutual inductance drop is conducted under various track structure parameters during track crossing and curve negotiation operation conditions. Secondly, a dual-coil winding method is proposed to reduce the insulation stress on the PCB board. Additionally, a method for calculating the wire length and a design process for the overall parameters of the pickup are derived. Finally, two Txs and a 1.5 kW power receiver (Rx) were designed to verify the mutual inductance fall under the aforementioned conditions. During low-speed full-load operations, a constant-voltage output was achieved through the proposed dual-loop PI control strategy, thereby meeting the requirements for a constant-voltage output in industrial applications.

A two-stage insulation method for suppressing thermal crosstalk in microarray sensitive units

Thermal crosstalk between array structures is a key factor in limiting the sensitivity of micro-nano array sensors. We propose a two-stage thermally isolated structure with thermal holes and heat dissipation layer and pulsed voltage heating to reduce thermal crosstalk. Through finite element thermal simulation analysis as well as thermal interference test, the results show that the thermal crosstalk of the two-stage structure is reduced by 12.89% and 39.67%, respectively, in the steady state compared to the structure with no thermal isolation, and pulsed voltage heating leads to the thermal crosstalk of the two-stage structure to be <10%.

Plasticity-Induced Heating: Revisiting the Energy-Based Variational Model.

Temperature evolution during plastic deformation is of great importance for the design of manufacturing processes, as well as for the analysis and prediction of tool wear. However, the results from experimental- and numerical-type research are still often contradictory. In this paper, we analyze methods for estimating plasticity-induced heating directly from displacement fields that can be recorded during experiments or extracted from simulation results. In terms of computational methodology, the thermodynamically motivated energy-based variational formulation of the coupled thermo-mechanical boundary-value problem is adapted to the problem at hand. Since an analysis of this variational formulation exhibits challenges and distinct inconsistencies with respect to the problem at hand, an alternative approach is proposed. This alternative approach is essentially a purely thermal finite element simulation, and it is conducted using a heat source term that is empirically based on the fraction of irreversible deformation work converted to heat. Our approach estimates plasticity-induced heating based on the strain and strain rate data derived from displacement fields. We therefore incorporate thermo-visco-plastic constitutive behavior (Johnson-Cook) with a thermodynamically motivated model that specifies the fraction of plastic work converted to heat (the Taylor-Quinney coefficient).

Overheating detection in the powder bed fusion of metals using a laser beam through local thermal resistance analysis

The powder bed fusion of metals using a laser beam is a production technique to additively manufacture parts by melting metallic powder layers with a laser. The geometry of a part affects how the heat is dissipated from the process zone. Geometry-induced heat accumulation results in undesirable processing conditions and part properties. Current approaches to identify locations of overheating are mostly based on thermal finite element simulations. This study presents an analytical approach to detect these locations based on a voxel-wise calculation of the local thermal resistance. With a thermal simulation, it was verified that the presented approach efficiently detects areas of overheating. This allows the automated evaluation of the manufacturability of existing geometries.

Thermal Model and Thermal Analysis of the Dual Drive Sliding Feed System

The dual drive sliding feed system can obtain a uniform and stable resolution at extremely low speeds and significantly reduce the system’s nonlinear friction. However, the numerous thermal sources within the system and the multipoint sliding contact during transmission result in a significant temperature rise, leading to considerable thermal deformation and errors. Moreover, the responsive mechanism of the thermal characteristics needs to be clarified. Therefore, firstly, a frictional torque model of the engagement of the screw and nut is established, and the heat generation, heat transfer, and thermal contact resistance (TCR) are solved. Then, based on the solution, a finite element thermal simulation model of the dual drive sliding feed system is established, and experiments are performed for validation. The results show that the error in temperature at the measuring point is less than 2.1 °C, and the axial thermal elongation of the screw is less than 6.2 µm. Finally, the thermal characteristics of the feeding system under various operating conditions are analyzed. The results show that the established thermal simulated model can effectively describe the dynamic thermal characteristics of the dual drive sliding feed system during operation. The effects of the rotational speed and ambient temperature on the dynamic thermal characteristics of the dual drive sliding feed system are investigated separately. The temperature increase in each part of the screw during the operation is characterized.

Simulation and Experimental Study of Hot Deformation Behavior in Near β Phase Region for TC21 Alloy with a Forged Structure

Quasi-beta processing was considered to be a promising processing method to obtain a component with excellent mechanical properties. To achieve an optimized quasi-beta processing parameter for TC21 alloys, the hot deformation behavior in the near β phase region for the alloy with a forged structure was investigated by the thermal compression test and finite element (FEM) simulation. The obtained results indicated that the flow behavior of the samples was significantly influenced by the hot deformation parameters, and it exhibited a flow hardening behavior at the start stage of deformation. Based on the experimental data, the constitutive equation and processing maps were obtained. The optimum hot processing parameter was 986 °C/10−3 s−1. Based on the FEM simulation results, the evolution of the temperature field, strain field, and stress field in the deformed samples at different strains exhibited a similar trend in the unstable region, which was distributed symmetrically along the center line of the samples, with the center area of the samples being the highest and the center area of the section being the lowest.

Electro-Absorption Modulator Thermo-Optical Self-Heating Analysis

In this work a novel methodology is presented for coupled thermo-optical modelling of an electro-absorption modulator (EAM). First, an optical FDTD simulation results in the light absorption map in the EAM waveguide. This absorption is used as a heat source boundary condition in a thermal finite element (FE) simulation in order to calculate the waveguide temperature. The FE model is validated with experimental data. The temperature is averaged over the device length and used as input in a compact, fully coupled thermo-optical model. The model reveals a thermal instability of the device characteristic, which limits the maximum amount of optical power the device can handle. Finally, using the thermal FE model, a self-heating mitigation strategy is proposed. Using process compatible design changes, self-heating can be reduced by up to 40%, greatly increasing the EAM optical power handling capabilities.

In-situ Selective Laser Heat Treatment for microstructural control of additively manufactured Ti-6Al-4V

As-built Laser Powder Bed Fusion (LPBF) Ti-6Al-4V typically exhibits a fully acicular α′-martensite microstructure, and requires post-process heat treatment in order to decompose the martensite and achieve sufficient ductility. In the present study, we demonstrate a simple concept based on in-situ Selective Laser Heat Treatment (SLHT) that can effectively alter the microstructure and activate the decomposition of the α′-martensite into a lamellar α+β microstructure within a short time scale (~30s). SLHT consists of multiple rescanning of the printed part, with low energy density, triggering solid-state phase transformations. Operando X-ray diffraction has been performed on cuboid and thin wall geometries, and was augmented by thermal finite element simulations. Upon SLHT, a gradual formation of the β phase as well as an α/α′peak narrowing trend have been evidenced through X-ray diffraction, as an indication of the diffusional nature of α′-martensite decomposition. Moreover, through fine tuning of the process parameters at the final stage of SLHT, a controlled temperature evolution during cooling was achieved, leading to preservation of the β phase, a product of the decomposition, down to room temperature. Complementary microstructural characterizations via EBSD, SEM, and TEM confirm the presence of a lamellar α+β microstructure after SLHT. Our results evidence, for the first time, the fast kinetics of α′-martensite decomposition under in-situ SLHT. The approach is meant to be implemented at selected locations during the LPBF process, avoiding time-consuming post processing steps, and leading to composite-like, architected microstructures.

A new heat resistant load bearing system incorporating honeycomb structured cementitious composite investigated via experiments and modelling

The load-bearing cementitious materials such as concrete rely on passive insulation to resist heat in fire and other high-temperature events. This study introduces a novel load-bearing system, incorporating a honeycomb-structured cementitious composite (HSCC) to enable adjustable active heat dissipation. Compared with passive thermal insulation, active heat dissipation brings substantial improvement on heat resistance performance under compressive load. The study investigated the heat transfer process of the HSCC material fabricated by 3D-printed micro scaffolds by combining the microscopic thermal imaging method and finite element simulation. The proposed material has a conductivity of up to 0.24 W/mK, which shows a 30% improvement in heat resistance compared to lightweight concretes. The total compressive strength reduction is ten times less than ordinary concrete under elevated temperatures at 1300 °C. The microscopic thermal imaging provided experimental data to enable the development of multi-phase simulation models, which allowed further predictions of the material performance under elevated temperatures. The novel load-bearing system enabled ventilation through the HSCC in combination with the low thermal conductivity of the HSCC, which allowed this novel system to demonstrate a capacity loss at 1300 °C that was ten times less than that of ordinary concrete walls. Furthermore, the effect of ventilation and heterogeneity in the HSCC on the heat dissipation and temperature distribution in the materials is also characterized by this study.

Advancing efficiency and reliability in thermal analysis of laser powder-bed fusion

In laser based powder-bed fusion of metals (PBF-LB/M), parts are fabricated by melting layers of powder using a high-intensity laser beam. During this process, the material is exposed to rapid cooling rates and intense thermal gradients, which are the underlying causes of residual stress formation and development of a unique microstructure in these components. Therefore, understanding the heat transfer phenomenon and reliably representing exposed temperature profiles in simulation frameworks are prerequisites for studying the microstructure and residual stress development during the PBF-LB/M process. This work employs a combination of experimental measurements and model development to study this phenomenon. Thermal properties of Hastelloy X were measured in the as-deposited state and used to setup finite element (FE) thermal simulations of the PBF-LB/M process. In addition, in-situ temperature evolutions near the laser tracks were measured by instrumenting thin-wall structures with K-type thermocouples in a two-stage fabrication process. The gathered data was used to calibrate uncertain modelling parameters, and ultimately, the simulation framework could closely represent the measured temperature histories. To address the high computational cost of FE thermal simulations, an adaptive-local/global multiscale modelling approach was proposed, which substantially reduced computation times without compromising the accuracy of the results. The modelling files and scripts are available in github.