Preamble

Real-Time Temperature Control and Performance Optimization of an Induction Heating System for In-Situ Neutron Experiments Yaojun Guan, 1, 2, Bin Li, 2, 3, 4, Haoran Chen, 5, 2, 4, Linjin Deng, 2, 6, 4 Wenbin Zhong, 2, 4, 3 Fan Ye, 2, 4, 3 Mengjia Dou, 2, 4, 3 Bo Bai, 2, 4, 3 Xiaohu Li, 2, 4, 3 Yi Zhang, Xiaoyue Zhang, Xinzhi Liu, Mengyu He, Hui Cheng, 2, 4, 3, Haitao Hu, 2, 4, 3, and Xin Tong 2, 4, 3, 1 Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices, School of Physics, Sun Yat-sen University, Guangzhou 510275, China Spallation Neutron Source Science Center, Dongguan, 523803, China Institute of High Energy Physics, Chinese Academy of Sciences (CAS), Beijing, 100049, China Guangdong Provincial Key Laboratory of Extreme Conditions, Dongguan, 523803, China Northeastern University, No3-11 Wenhua Road, Heping District, Shenyang, Liaoning, 110819, China Dongguan University of Technology, Dongguan, 523808, China University of California, Merced 5200 North Lake Rd, Merced, CA 95343, United States Induction heating is an indispensable non-contact heat source for advanced thermal manufacturing and in-situ high-temperature characterization, yet conventional low-/mid-frequency systems suffer from large skin depth and diffuse energy deposition, resulting in sluggish heating that fails to meet the demands of rapid and highly localized thermal processing. To overcome this limitation, we propose a “high-frequency–high-current” syn- ergistic intensification strategy: the inverter frequency is elevated to the hundred-kHz range and paired with a large-current ZCS-IGBT series-resonant converter, compressing electromagnetic energy into a sub-millimetre surface layer and enabling a quadratic escalation of heat-flux density and an extreme heating rate. A full-digital phase-locked loop together with dual-redundant protection guarantees stable high-current output at elevated frequencies. Theoretical analysis, multi-physics simulations and comparative experiments consistently demon- strate that the strategy can rapidly and uniformly heat the work-piece surface to the target temperature, offering an efficient, controllable and mobile heat source for low-carbon and precision thermal treatments.

Keywords

High frequency induction heating; Rapid heating; Precision temperature control; Force thermal in-situ loading

INTRODUCTION

In key engineering fields such as aerospace, automotive manufacturing, and oil drilling, with the in-depth integration

of materials science and mechanical engineering, the research 4

on the mechanical behavior and microstructure evolution of 5

materials under extreme high-temperature conditions has be- come a core scientific challenge for improving the perfor- mance of engineering equipment [ ]. Neutron scattering technology [ ] not only plays an important role in fields such as physics [ ], biology [ ], archaeology [ ], and chem- istry [ ], but also serves as a crucial detection and analysis tool in the field of materials science research [ ].As a key instrument based on this technology, neutron diffractome- ter is not only suitable for studying the microstructure and

mechanical behavior of materials under conventional condi- 15

tions [ 11 , 12 ], but also exhibit unique advantages in char- 16

This work was supported by the National Key R&D Program of China (No. 2022YFA1604104), the Youth Innovation Promotion Association of the Chinese Academy of Sciences, the National Natural Science Foun- dation of China (12427803, 12425512, and 12575323), the Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices (No. 2022B1212010008), the Research Center for Magnetoelectric Physics of Guangdong Province (2024B0303390001), and the Guangdong Provincial Key Laboratory of Extreme Conditions (2023B1212010002).

The authors contribute equally. acterizing the microstructure evolution of materials in high- temperature environments [ ]. With the increasing focus on transient non-equilibrium processes, rapid heating, as a cru- cial method for simulating extreme thermal loads, has been widely applied in the research on high-temperature material

behavior. To achieve real-time dynamic monitoring of ma- 22

terials under extreme high-temperature conditions, especially

the accurate capture of mechanical responses and microstruc- 24

ture evolution during the rapid heating process [ ], the cou-

pling of neutron spectrometers with thermomechanical load- 26

ing systems—particularly heating devices with rapid temper- ature rise capabilities—has become a key supporting means Traditional heating devices mainly include infrared heating and resistance heating [ ]. Among these, resistance heat- ing primarily raises the sample temperature by leveraging the inherent electrical resistance of the material [ ], while infrared heating mainly relies on the principle of thermal ra- diation to indirectly heat materials [ ].The former ex- hibits low heating and cooling rates, which leads to prolonged experimental cycles [ ]. Moreover, different types of re- sistance wires have distinct operating temperature ranges, and they are prone to oxidation at high temperatures—this results in short service lives of heating elements and restricts the tem- perature range for high-temperature experiments [ ].The latter, however, suffers from issues such as uneven tempera- ture field distribution and poor temperature control accuracy.

Additionally, due to the diversity of test materials, it shows poor heating efficiency when dealing with materials that have low infrared absorption rates [

As a non-contact, efficient, and controllable heating tech- nology, induction heating has gradually replaced traditional heating methods in recent years and become one of the pri- mary heating means in high-temperature material research ]. Its notable advantages lie in its ability to act di-

rectly on the heating target, which significantly minimizes 52

heat loss—thus ensuring efficient heating while drastically

shortening the heating duration [ 31 , 32 ].Furthermore, through 54

the precise adjustment of the induction coil and associated control systems, induction heating can accurately regulate the heating area and temperature gradient according to experi- mental requirements. This enables it to meet the stringent requirements for heating precision and dynamic response in high-temperature material research [ Recently, a variety of high-temperature heating technolo- gies have been applied in neutron diffractometer experiments to achieve high-precision high-temperature material testing.

The ENGIN-X instrument at the ISIS Laboratory employs an infrared-heated high-temperature furnace, equipped with four 2 kW infrared heaters, and its maximum heating temper- ature can reach up to 1373 K [ ].By contrast, the VUL-

CAN instrument at the SNS Laboratory in the United States 68

integrates three heating devices, including a standalone high- temperature furnace, a resistance-heated gas-tight load frame furnace, and an auxiliary induction heating coil. Their max- imum temperature can reach 1600 °C; among these devices, the resistance-heated gas-tight load frame furnace features a relatively high heating rate, capable of achieving a tempera- ture rise of 600 °C/s [ ].At the J-PARC Laboratory in Japan, the PLANET instrument employs a heater powered by em- bedded high-voltage batteries, with a maximum achievable temperature of 2000 K; in contrast, the TAKUMI instrument uses an infrared heating device, which can only reach a max- imum heating temperature of 1273 K [ The China Spallation Neutron Source (CSNS) currently has such high-temperature sample environment devices as one pulsed laser heating furnace and one ultra-high- temperature induction heating device.

Among these, the pulsed laser heating furnace has a rated output power range of 100 W to 2000 W, a maximum controllable heating tem- perature of 1800 °C, and a heating rate ranging from 80 °C/s to 150 °C/s [ ].The induction heating device, on the other hand, has a maximum heating temperature of 2700 K and a heating power of 60 kW, ranking among the induction heating furnaces with the highest temperatures in the field currently ]. However, this induction heating device is mainly used for research on high-temperature microstructures and macro- scopic properties, and cannot meet the requirements of ex- periments such as strain measurement [ ] and residual stress distribution measurement [ Addressing the insufficiency of existing heating devices in rapid temperature rise capability, this study focuses on key

technical issues such as the optimization of high-frequency 99

induction technology, enhancement of thermal field unifor- 100

mity, and intelligentization of temperature control systems, and proposes an innovative rapid temperature rise induction

heating scheme. This scheme aims to significantly improve 103

heating rate, temperature control accuracy, and thermal field stability, thereby meeting the requirements of diffractometer experiments—including those for material dynamic response, strain measurement, and residual stress analysis—under high- temperature conditions. To verify the feasibility and perfor- mance advantages of this scheme, this paper combines the- oretical modeling and experimental testing to conduct a sys- tematic evaluation of the system from multiple dimensions, including electromagnetic coupling, heat transfer behavior, and temperature control feedback response.

The implementation of this research not only helps to im- prove the the overall experimental efficiency and testing ac- curacy of neutron diffractometers, but also provides strong

technical support for the accurate investigation of the service 117

behavior of materials in complex thermo-mechanical environ- 118

ments, thus holding significant theoretical significance and 119

engineering application value. INTRODUCTION TO THE OVERALL DESIGN AND MECHANISM OF THE INSTRUMENT grates an advanced engineering large-sample loading device with induction heating equipment, providing a versatile ex- perimental platform for materials science research. This plat- form is capable of simultaneously applying stress and induc- tion heating to materials, effectively simulating the complex environmental conditions encountered in practical applica- tions. To address the limitations of existing heating devices in terms of rapid temperature increase capabilities, we will delve into the principles of induction heating technology, fo- cusing on the optimization of high-frequency induction tech-

niques, enhancement of thermal field uniformity, and the in- 134

telligent control of temperature systems, with the aim of sig-

nificantly improving heating efficiency and precision, thereby 136

better serving research and development in the field of mate- rials science.

Induction heating technology is based on the principle of electromagnetic induction.

When an alternating current flows through the induction coil, it generates an alternating magnetic field within the coil. A workpiece placed within this alternating magnetic field experiences an induced elec- tromotive force e, which in turn gives rise to eddy currents within the workpiece. Due to the eddy current effect and the inherent equivalent resistance R of the metal material, ther- mal energy is generated internally, thereby achieving the goal of heating the workpiece.

During the heating process, induction heating transfers electrical energy from the induction coil to the metallic work- piece, which is then converted into thermal energy within the workpiece itself. This energy transfer is accomplished via electromagnetic induction, without direct physical contact be- tween the coil and the workpiece. As such, induction heating is classified as a non-contact heating method. The working process diagram of induction heating is shown in Fig.

When the sinusoidal current i in the induction coil varies at a specific frequency, the resulting alternating magnetic field generated within the coil will exhibit the same frequency as

the input current. This time-varying magnetic field induces a magnetic flux through the workpiece, which can be ex- pressed by the following formula [

Φ = Φ m sin( ωt ) (1) 163

Where is the magnetic flux in the induction coil; the amplitude of the alternating flux; and is the current an- gular frequency. The alternating magnetic flux generated by the induction coil induces an electromotive force (EMF) the workpiece via the principle of electromagnetic induction.

This induced EMF can be described by Faraday’s law as fol- lows,

e = − N d dt (2) 171

Where is the induced electromotive force; is the equiv- alent number of turns of the workpiece. Substituting Eq. ( into Eq. ( ) gives the induced electromotive force as follows,

e = − N m ω cos( ωt ) (3) 175

The Root Mean Square value of the induced electromotive force as follow,

2 = 2 πfN m √

E = N m ω √

2 = 4 . 44 Nf m (4) 178

Where is the effective value of the induced electromotive force; is the frequency of the energizing current of the in- duction coil. Induction electromotive force in the metal work- piece produced by the induction current so that the workpiece achieves the purpose of heating, the Joule heat generated dur- ing the heating process is given by,

Q = 0 . 24 Pt = 0 . 24 I 2 Rt

= 0 . 24 E 2

= 4 . 73 f 2 N 2 2 m Rt Z 2

Where is the generated Joule heat, is the output power of the induction heating device, is the energization time of the induction coil when the metal workpiece is heated, the rms value of the induction current, is the equivalent resistance of the metal workpiece, and is the equivalent impedance modulus of the metal workpiece.

According to the above equations, when the properties and geometry of the metal workpiece remain unchanged, the amount of heat generated within the workpiece depends pri- marily on the frequency f of the current supplied to the in- duction coil, as well as the magnetic flux. The magnetic flux

itself is determined by multiple factors, including the magni- 197

tude of the current flowing through the coil, the number of turns in the heating coil, and its spatial orientation relative to the workpiece.

Therefore, for a given metal workpiece, the heating power delivered by the induction heating system can be effectively adjusted by altering the excitation frequency, the coil current, the number of coil turns, or the position of the coil with re- spect to the workpiece. These parameters collectively govern the efficiency and intensity of electromagnetic induction and thus play a crucial role in controlling the thermal behavior of the system.

Based on this, the paper proposes and verifies an “HF- Large Current” collaborative enhancement instrument design scheme: The inverter switching frequency is extended from the commonly used 10-30 kHz to 110 kHz.

This uses a 110 kHz large current ZCS-IGBT series resonance with 33 ns DSP all-digital phase-locking, achieving an efficiency of

≥ 95% and a power factor of ≥ 0 . 87 . The dual-channel 215

redundancy and 5 s hardware protection ensure a 99.9% availability. It also includes a built-in 4–20 mA temperature closed-loop and segmented programming, with a temperature control accuracy of 1%FS, providing a high-efficiency and highly reliable integrated heat source for high-power mobile output scenarios.

The prototype induction heating device designed using the “high-frequency - large current” collaborative enhancement

concept is shown in Fig. . The system is built with a PID closed-loop control for accurate temperature management.

The temperature reading is done using a platinum-rhodium thermocouple fixed to the test workpiece, with the option of replacing it with an infrared thermometer if needed. This design ensures precision and flexibility, adapting to various heating processes with reliable, real-time feedback and con- trol.

By significantly increasing the frequency from 30 kHz to 234

110 kHz, the system achieves a heating rate of up to 200°C/s, reducing the high-temperature dwell time from several tens of seconds to just a few seconds.

This rapid thermal re- sponse provides reproducible and instantaneous temperature profiles for in-situ loading experiments. The combination of fast heating and precise temperature control enables mate-

rial behavior studies under dynamic thermo-mechanical cou- 241

pling conditions, offering enhanced temporal resolution and data reliability. Additionally, the reduction in heating time and convection-radiation losses leads to a decrease in overall

energy consumption. Significant synergistic optimization is 245

achieved in process precision and characterization data qual- ity, realizing the transition from traditional prolonged heat- ing to an instantaneous, precise, and energy-efficient heating mode.

INDUCTION HEATING SIMULATION

To investigate the coupling mechanism between the elec- 251

tromagnetic field and the temperature field within a metal workpiece during the induction heating process, a three- dimensional model was established using the COMSOL Mul- tiphysics simulation platform, as shown in Fig. . This model systematically simulates the electromagnetic-thermal interac- tions between the induction coil and the cylindrical metal workpiece.

The geometry includes the induction coil, the workpiece, and the surrounding air domain. An insulation gap is defined between the coil and the workpiece to repli- The simulation employs the “Magnetic Fields” and “Heat Transfer in Solids” physics interfaces, with a fully coupled solution approach to ensure real-time feedback between the electromagnetic excitation and thermal response. The induc- tion coil is excited by a sinusoidal alternating current with a frequency of 110 kHz and a current amplitude of 700 A.

The coil is made of a highly conductive metal. To prevent excessive temperature rise in the coil during continuous oper- ation, an internal water-cooling channel is incorporated into

the model. This is implemented by defining a fluid domain 272

within the coil and applying either a constant temperature boundary condition or a forced convection condition to sim- ulate the flow of cooling water. The cooling system ensures thermal stability of the coil during operation and enhances the overall heating efficiency and reliability of the simulation. coil geometry parameters number of turns of coil (turns) coil spacing (mm) distance between two coils (mm) large coil radius (mm) coil small radius (mm) The inlet temperature of the cooling water is set to

strategy plays a critical role in maintaining coil performance 280

and ensuring accurate prediction of the thermal field distribu- The simulated metal material is tantalum. In terms of ma- terial properties, the workpiece was assigned temperature- dependent parameters, including electrical conductivity, ther- mal conductivity, specific heat capacity, and density. These properties were implemented in COMSOL via interpolation functions to ensure accurate modeling of the material re- sponse under high-temperature conditions.

To better reflect realistic thermal boundary conditions, nat- ural convection was applied to the outer surface of the work-

piece, with a heat transfer coefficient set at K. In ad- dition, a surface-to-ambient radiation model was activated un- der high-temperature conditions to account for radiative heat losses from the workpiece to the environment.

The initial temperature of the entire model was set to 296

298 K. A time-dependent heat transfer solver was used to perform transient thermal simulations, with a total simulation time of 20 minutes. The time step was adaptively controlled to balance computational efficiency and solution accuracy.

To ensure the accuracy of the electromagnetic and temper- ature field calculations, especially in regions where eddy cur- rents and heat are concentrated (such as the surface of the metal workpiece and areas near the induction coil), a reason- able mesh strategy was employed in the model. In this study, the physics-controlled mesh generation method provided by COMSOL was used, combined with adaptive refinement in critical regions, to create a multi-scale mesh across the entire computational domain.

At the surface of the tantalum workpiece, due to the sig-

nificant skin effect induced by the high-frequency current ex- 311

citation, eddy currents primarily concentrate in a thin surface layer, typically on the order of millimeters or smaller. There- fore, a high-density mesh was generated in this region to cap- ture the rapid variations in both current and temperature. In contrast, coarser mesh elements were used in regions farther from the excitation source and in non-critical areas of the structure, in order to reduce the overall computational load and improve simulation efficiency.

To ensure the accuracy of the numerical simulation, a mesh independence verification was conducted using three different mesh densities, consisting of approximately 67991, 131691, and 296302 elements, respectively. Fig. illustrates the tem- perature evolution of the heated rod over time under each mesh configuration. As shown in the figure, the simulation re- sults obtained using 131691 and 296302 elements are nearly identical, indicating that further mesh refinement has a neg- ligible effect on the outcome. Therefore, considering both computational cost and result accuracy, the mesh with 131691 elements was selected for subsequent simulation studies.

In practical applications, heating efficiency and tempera- ture control precision directly affect the stability of the pro- cess and the final performance. As a core energy coupling component in the induction heating system, the structural pa-

rameters of the coil have a significant impact on the distri- 335

bution of the electromagnetic field and the path of eddy cur-

rents, which in turn significantly affect the generation of Joule 337

heating and the distribution of the temperature field. There- fore, systematically studying the impact of structural factors, such as the number of coil turns and the distance between the coil and the workpiece, on heating capacity is essential for optimizing the design of induction heating systems and im-

proving heating efficiency and temperature uniformity. This 343

is of great engineering application value and theoretical sig-

nificance. 345

To this end, in this study, four different coil structure pa- rameters were simulated and compared under the same ex- citation current (700 A) and frequency (30 kHz) conditions, with the results shown in Fig. . The results clearly demon-

strate that the coil structure has a significant impact on both 350

the heating rate and the final temperature. Particularly, when the coil has 3 turns and the distance between the coil and the workpiece is 20 mm, the temperature rises the fastest, with the final stable temperature reaching approximately showing the strongest heating capacity.

In contrast, when the coil has 2 turns and the distance between the coil and the workpiece is 30 mm, the temperature rises more slowly, with the final steady-state temperature being only around The heating rates for the four different coil structures are 118 K/min, K/min, K/min, and K/min, respectively.

The analysis indicates that, under the same conditions, in- creasing the number of coil turns effectively enhances the in- tensity of the alternating magnetic field, thereby increasing

the induced electromotive force within a unit volume, which 364

further intensifies the generation of eddy currents and releases

more Joule heat. At the same time, reducing the distance be- tween the coil and the workpiece helps improve the coupling efficiency of the magnetic field with the workpiece, allowing the electromagnetic energy to be more efficiently transferred to the metal. Increasing the number of turns or decreasing the distance between the coil and the workpiece not only accel-

erates the temperature rise rate but also significantly shortens 372

the time required to reach steady-state temperature, indicating a high sensitivity of the induction heating system to structural design optimization.

Therefore, in practical engineering design, the coil config- uration with more turns and a smaller distance between the coil and the workpiece should be prioritized, based on spe- cific requirements, to achieve higher heating efficiency and shorter heating times. The results of this study provide strong theoretical support for the structural optimization of induc- tion heating systems and serve as an important reference for achieving precise target temperature control, localized heat- ing, and multi-stage power adjustment.

In the experiment investigating the influence of heating frequency on the performance of an induction heating sys- tem, we have selected a coil structure with 2 turns and a 20- millimeter gap between the coil and the workpiece. This se- lection is based on a comprehensive consideration of multiple factors. From the perspective of coil turns, a 2-turn coil can generate a moderate magnetic field strength while meeting the basic requirements for induction heating. This not only ensures that sufficient eddy currents are induced in the work- piece to achieve heating but also avoids the issues of increased system inductance and reduced power factor that may arise from an excessive number of turns. Moreover, the simplic- ity of this coil structure facilitates experimental operation and control, reduces experimental costs, and makes heat dissipa- tion easier, thereby contributing to the stable operation of the experimental system. Regarding the gap, the 20-millimeter spacing is carefully designed. This spacing ensures effective magnetic field coupling to the workpiece, preventing local overheating of the workpiece surface due to excessively small gaps and magnetic field energy loss due to excessively large gaps. Additionally, the 20-millimeter spacing accommodates

workpieces of various sizes and shapes, enhancing the univer- 406

sality of the experimental results. It also prevents collisions between the workpiece and the coil during the heating process due to thermal expansion, ensuring the safety of the experi- ment and the stability of the system.

In summary, considering the above factors, we have chosen a coil structure with 2 turns and a 20-millimeter gap between the coil and the workpiece to further investigate the impact of heating frequency on the performance of the induction heat- frequency induction heating device we designed in terms of rapid heating, a comparative analysis was conducted between it and a conventional 30 kHz heating system under the same operating conditions. The study primarily focused on exam-

ining the effects of frequency variation on energy coupling 420

efficiency, the distribution of eddy currents within the work- piece, and the rate of temperature rise, in order to reveal the potential benefits of high-frequency induction heating in im- proving heating response time and thermal efficiency.

As depicted in Fig. , the 110 kHz induction heating achieves a temperature rise of 200 K every 5 min, doubling further re- veals that the current density peaks at and is confined to the surface layer at 110 Hz, whereas the 30 Hz profile exhibits a lower, more gradual radial decay. There- fore, increasing the frequency can not only effectively accel-

erate the heating process but also significantly enhance the 434

skin effect. Under the configuration of 110 kHz, the induc- tion heating efficiency is greatly improved, providing a more efficient and energy-saving solution for relevant applications.

To fully and deeply analyze the heating behavior under the 110 kHz configuration, we have conducted multidimensional

investigation work. We have not only monitored the dynamic 440

variation trend of the heating power but also measured the steady-state radial temperature distribution along the central

diameter direction. In addition, we have carried out a detailed analysis of the corresponding distribution between the overall temperature and the magnetic flux density.

The panel sequence provides the three-dimensional temperature field, three-dimensional magnetic-flux-density field, two-dimensional temperature contour, two-dimensional magnetic-flux-density contour, instantaneous heating-power curve, and the steady-state temperature distribution along the diameter at the geometric centre. In electromagnetic induc-

tion heating systems, numerical simulation techniques enable 454

us to analyze the distribution of magnetic flux density and temperature.

The transient response of the heating power

curve at system startup, although initially exhibiting an over- 457

shoot phenomenon, rapidly decays within a certain time- frame, demonstrating the system’s ability to quickly achieve electromagnetic-thermal equilibrium. The radial temperature distribution features a typical saddle shape, which is the re- sult of the combined effects of surface convection cooling and axial heat conduction, with the surface forming a shal-

low temperature minimum due to convective heat dissipation. 464

This temperature distribution characteristic is crucial for un- derstanding and predicting the thermodynamic behavior dur- ing the heating process and also confirms the rapid establish- ment of electromagnetic-thermal equilibrium, which is of sig-

nificant importance for improving heating efficiency and en- 469

suring heating quality. To further validate the rapid-heating capability of the developed induction system, an experimen- tal campaign was conducted under identical operating condi- tions.

INDUCTION HEATING EXPERIMENTAL TEST To evaluate the rapid heating performance of the designed induction heating system, an experimental platform was es- tablished in this study, as illustrated in Fig. . This plat- form was specifically developed to systematically verify the heating efficiency of the high-frequency induction system and

to enable the synchronized control of heating and mechani- 480

cal loading processes. The platform integrates the high- fre-

quency induction heating module, mechanical loading unit, 482

precision temperature monitoring system, closed-loop water 483

cooling system, and a supervisory control platform, provid- ing a stable and high-responsive testing environment for high-

temperature thermomechanical coupling experiments. 486

Before the experiment begins, a comprehensive inspection and preheating of the equipment are conducted to ensure the proper operation of all modules. Special attention is given to the induction heating system’s power supply, coil, water cooling system pipes, and temperature control system, all of which undergo rigorous checks to prevent issues such as over- heating or energy overload during the experiment. Simultane-

ously, the mechanical loading system is calibrated to confirm 494

that its loading accuracy and range meet the experimental re- quirements. During this process, the surface of the specimen is cleaned and polished to remove oxides and oil, ensuring the accuracy and consistency of both temperature measure-

ment and mechanical loading. 499

Once the experiment begins, the induction heating system is activated, and the output frequency and power of the power supply are set. The specimen is then subjected to induction heating via a dual-turn copper coil. At a frequency of 110 kHz, the system rapidly heats the specimen surface to the de- sired temperature (typically between 1000 K and 1400 K),

with temperature accuracy monitored in real time. To avoid 506

interference during temperature measurement, the system is equipped with an infrared non-contact temperature sensor and a K-type thermocouple, and the real-time data is fed back to the control platform for calibration and validation. Tem- perature data is recorded every second to ensure continuous

monitoring of dynamic temperature changes, with the system 512

capable of automatically adjusting the heating parameters as required. Additionally, power, frequency, and other electri- cal parameters of the induction heating process are recorded synchronously for subsequent data analysis and verification.

While the induction heating system operates stably, the me-

chanical loading system is activated. The loading force starts 518

from 0 N and gradually increases. The loading process is pre-

cisely controlled by an electronic servo universal testing ma- 520

chine, which applies axial tension or compression at a set rate , with different loading modes switched according to the ex- perimental design. All force and displacement data during the loading process are continuously collected by sensors, ensur- ing the accuracy and consistency of the parameters through- out the loading phase.

The core of the experiment is the thermomechanical cou- 527

pling process, during which the high temperature induced by

the heating and the mechanical loading simultaneously act on 529

the specimen, simulating real-world working conditions. The high-frequency current generates a strong skin effect, caus- ing the specimen’s surface temperature to rise rapidly. Con-

currently, due to the applied mechanical loading, the speci- 533

men undergoes deformation, and the material’s microstruc-

ture, strength, and deformation behavior change significantly 535

with varying temperature and stress. Once the experiment reaches the predetermined duration, the loading process ends, and the induction heating system is turned off, completing the

thermomechanical coupling experiment. 539

To systematically verify the rapid heating performance, a frequency comparison group was established in this exper- iment, using identical coil structures and loading parameters to conduct comparative tests at frequencies of 110 kHz and 30 kHz. The experimental results, as shown in Fig. , indicate that at 110 kHz, the induction heating system is able to heat the specimen to the target temperature in a shorter time, with a higher heating rate. Under high-frequency excitation, the skin effect is enhanced, resulting in a higher density of circu-

lating currents on the specimen’s surface. This effect signif- 549

icantly increases the power density of Joule heating, thereby effectively improving the efficiency of heat energy input. This characteristic not only accelerates the heating process of the

specimen but also provides a uniform high-temperature en- 553

vironment for the subsequent loading process, ensuring the stability and consistency of the heating procedure.

Subsequently, to ascertain the viability of force-thermal

loading, we conducted an experiment on 310S stainless steel under force-thermal conditions, as depicted in Fig. , which illustrates the stress-strain curve obtained from tensile testing of 310S stainless steel at C. This curve meticulously de- lineates the entire deformation process of the material, transi-

tioning from the elastic to the plastic phase and culminating 562

in fracture. At the onset, the curve exhibits a steep slope, indicative of the material’s elastic behavior. As strain pro-

gresses, the slope diminishes gradually, signifying the on- 565

set of plastic deformation where the rate of stress increment

Dimensions of Bar-Shaped Specimens. slows down. The curve reveals a yield strength of

fying the initiation of necking prior to fracture. Additionally, 569

the curve denotes a fracture elongation of , reflecting

for the material, beyond which a decline is observed, signi- 568

CSNS. the ductility of the material before rupture. These experi-

mental findings are instrumental in evaluating the mechanical 572

properties of 310S stainless steel under high-temperature con- ditions, particularly in research scenarios necessitating pre- cise temperature control and rapid thermal response, such as dynamic high-temperature loading, stress measurement, and

in-situ monitoring of material behavior. 577

In neutron scattering experiments, it is crucial to ensure

that the induction heating device does not significantly af- 579

fect the scattering results of the sample. To this end, we de- signed an experiment to assess whether the introduction of the induction heating device would introduce additional diffrac- tion peaks in the scattering pattern,The experimental setup is shown in Fig. . In the experiment, we used vanadium-

nickel alloy samples and recorded the neutron scattering data 585

of the vanadium-nickel alloy samples under the combined ac- 586

tion of the materials testing system (MTS system) and the in- duction heating device, as well as under the action of the MTS system alone, as shown in Fig. . By subtracting the control group data from the experimental group data, we were able to effectively eliminate the scattering signals from other devices, thereby revealing the scattering contribution of the induction heating device. After performing a difference analysis on the two sets of data and normalizing the differences, we obtained a straight line close to 1 as shown in Fig. , which clearly indicates that the introduction of the induction heating device did not introduce additional diffraction peaks in the scatter-

ing pattern and had no significant impact on the scattering re- 598

sults of the samples. Through experimental verification, the

induction heating device we designed had no significant im- 600

pact on the scattering results of vanadium-nickel alloy sam- 601

ples in neutron scattering experiments, especially not intro- ducing any extra diffraction peaks. This conclusion not only proves the reliability of the induction heating device but also provides an important reference for future high-temperature

mechanical property tests. 606

SUMMARY

This study presents a high-frequency induction heating scheme. After rigorous validation through theoretical anal- ysis, simulation studies, and experimental verification, the

scheme has demonstrated significant improvements in heat- 611

ing rate and temperature control accuracy, effectively over- coming the limitations of conventional heating systems. By increasing the frequency to 110 kHz and employing a high- current zero-voltage switching (ZCS) IGBT series resonant converter, this study has successfully achieved efficient com- pression of electromagnetic energy into the submillimeter

surface layer. This not only significantly enhances the ther- 618

mal flux density but also greatly increases the heating rate.

Both simulation and experimental results consistently show that, under the same power conditions, the high-frequency heating technology can rapidly heat samples to higher tem- peratures. When reaching the same target temperature, the technology exhibits a faster heating rate and higher stability.

This characteristic is crucial for in situ characterization ex- periments, as it provides repeatable and precise temperature

profiles, significantly improving the temporal resolution and 627

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