Variation Of Temperature Field Research Articles

Research on lightweight design method of diesel engine steel piston based on heat transfer characteristics

Steel pistons are gradually replacing traditional aluminum–silicon alloy pistons as the preferred choice for high-power density engines. However, there is still a lack of systematic research on the heat transfer characteristics of steel pistons in the field of small bore diesel engines. For this reason, this paper was based on the storage temperature testing system to study the variation of temperature field and thermal stress in steel pistons of the small-bore diesel engine under the maximum torque conditions. The results show that there are significant temperature variations in the circumferential path of the steel piston head, indicating that the temperature distribution of the steel piston is highly uneven. The highest temperatures and maximum thermal stresses were found in the rim. To further achieve the lightweighting of the steel piston, a lightweight design method based on heat transfer characteristics was proposed. A multi-objective optimization algorithm was used to optimize the top land height and the position and shape of the cooling gallery. The structural design solutions with volume and thermal stress control were finally obtained. The optimized design solution can reduce the mass by a maximum of 10.01 %, the maximum temperature by a maximum of 35.04 °C and the maximum thermal stress by a maximum of 18.38 % compared to the original design.

Magnetoresistance and magnetic field-induced phase transition in two-dimensional antiferromagnet Fe1/3NbS2

We perform systematic studies on the magnetic and magnetotransport properties of Fe1/3NbS2 single crystal. Results show that Fe1/3NbS2 is an antiferromagnet with strong perpendicular magnetocrystalline anisotropy even in the paramagnetic state. The Fe1/3NbS2 nanoplate exhibits exotic magnetotransport characteristics with variation of temperature and magnetic field in the vicinity of Néel temperature. The temperature dependence of resistivity indicates that the magnetic field has a substantial effect on the Néel order of Fe1/3NbS2, and an intermediate phase occurs before the sample enters into the antiferromagnetic state. It is the field- or temperature-induced antiferromagnetic–intermediate phase and intermediate phase–paramagnetic phase transitions that lead to the novel magnetotransport characteristics in the vicinity of Néel temperature. The findings in this work will promote future studies based on two-dimensional antiferromagnetic spintronics.

Studies on selective laser quenching by high repetition frequency lasers with scanning galvanometer

This study introduces a novel material processing methodology termed High Repetition Frequency Selective Laser Quenching (HRF-SLQ). This technique utilizes high-power lasers with a maximum power of 5 kW in conjunction with a scanning galvanometer, operating at elevated repetition rates up to 200 Hz, to specifically treat surfaces of high and medium carbon steels. The application of this method leads to the creation of allotropic metal matrix composite materials (A-MMCs). In general, the scanning speed of a galvanometer can range from hundreds to thousands of times per second. Based on the high acceleration and rapid jumping characteristics of the scanning galvanometer, this technology transforms the high-power laser heating of metal plates from continuous heating mode to parallel pulse heating mode, which repeats heating 30 to 200 times per second. This transformation ensures the quenched layer avoids melting even under prolonged irradiation times by high-power lasers. Consequently, it can significantly enhance processing efficiency by selective laser quenching (SLQ), ensuring that the depth of the hardened layer reaches 0.88–0.94 mm and keeping the surface smooth without melting. This paper systematically investigates the influence of various processing parameters, such as laser power (P), single heating time (t1), and the number of processing units (N), on the depth of the SLQ and the quenching efficiency. It also examines the impact of HRF-SLQ technology on the properties of A-MMCs and analyzes temperature field variations from room temperature to melting point through simulation methods combined with laser quenching experiments.

Simulation and experimental study on laser cleaning of paint-rust mixed layer on a Q235 surface

In this paper, the theoretical model of laser cleaning of paint-rust mixed layer on the surface of a Q235 steel plate is established from the perspective of the laser ablation effect and the thermal vibration effect. The study simulates the temperature and stress field variations of the mixed layer under different laser power densities. The experiment recorded ablative fumes and vibrational spattering generated during the cleaning process and measured the micro-morphology and surface roughness of the cleaned specimens. The results show that the cleaning mechanism of the paint-rust mixed layer is dominated by the ablation effect at low laser power densities, while the combined effects of ablation and thermal vibration dominate at high laser power densities. However, excessive laser energy can damage the substrate. At a laser power density of 12.37×106W/cm2, the substrate surface is free from contamination residues and exhibits a bright, white, metallic gloss, which can be determined as the cleaning threshold for laser cleaning of paint-rust mixed layers. This study provides a valuable reference for the laser cleaning of mixed pollutants of paint and rust on metal surfaces.

Testing and identification method for the interfacial heat transfer coefficient between CFRTP and tools under fast hot-stamping conditions

Carbon fiber reinforced thermoplastic composites (CFRTP) are increasingly applied in automobile structures. Hot-stamping is a fast forming process for complex components of CFRTP. During hot-stamping process, the variations of temperature field occur in entire forming process, which ultimately have an impact on the forming quality and dimensional precision of the part. The interfacial heat transfer behaviour between CFRTP and tools directly determines the temperature distribution in the part. However, the existing heat transfer testing and identification methods are designed for sheet metal, which may not be applicable for CFRTP due to the differences in material properties and forming processes. Therefore, in this work, a new test device was developed to reproduce the interfacial heat transfer behaviour of CFRTP under various hot-stamping conditions, and an inverse identification method of the interfacial heat transfer coefficient (IHTC) between CFRTP and tools was proposed. The influences of contact conditions on the IHTC were investigated, including the interfacial contact pressure, interfacial clearance, heating temperature of tools and sheets. The results showed that the IHTC demonstrated a positive correlation with the contact pressure. However, the IHTC would significantly decrease with the existence of a clearance at the interface. Within the entire heat transfer process, it was also found that an increase in tool temperature resulted in a decrease in the IHTC, while initial sheet temperature didn't exert a significant influence. Furthermore, the reliability of proposed testing and identification methods had been verified by the hot-stamping for U-shaped CFRTP parts. The temperature error between the simulation and experiment was less than 5 %.

On‐Chip Multimode WGM Microresonator with Cross‐Correlation Algorithm for Enhanced Sensing

AbstractOptical whispering‐gallery‐mode (WGM) microresonators emerge as a frontrunner for precision measurement due to their high sensitivity and compact footprint. They have demonstrated superior capabilities in detecting a wide range of objects, spanning from variations in temperature, humidity, and magnetic field, to local perturbations caused by viruses or nanoparticles. Traditional methods often rely on monitoring spectral changes in a single WGM resonance to extract the relevant information of sensing targets. However, in scenarios involving multiple sensing targets of interest (e.g., molecule detection in a temperature‐fluctuating environment), analyzing only one resonant mode may be insufficient, leading to inaccuracies or misinterpretations in deriving target information. To address this issue, a multimode‐based cross‐correlation algorithm is proposed to distinguish local perturbations from global environmental fluctuations. For validation, on‐chip silicon microresonators and pulley bus waveguides are integrated for robust multimode excitation. A proof‐of‐concept experiment demonstrates the effectiveness of this method in detecting nanoparticles in an environment with temperature changes. This approach showcases versatility and applicability in various optical sensors, introducing new prospects for achieving high‐sensitivity sensing through scalable integrated photonic platforms.

Entropy and energy transfer analysis of a Maxwell thin‐film fluid over an inclined surface with viscous dissipation effect

AbstractNon‐Newtonian fluid plays a vital role in the field of manufacturing and engineering sector, because of its immense heat transfer rate. The two‐dimensional incompressible unsteady Maxwell nanofluid thin‐film flow with MHD and viscous dissipation over an inclined surface is investigated. One of the mechanisms in the second law of thermodynamics, that is irreversibility which also analyzed. The Maxwell nanofluid thin film energy and motion equations in the additional information have been turned into a coupled differential system of the third order. The transformed ODE equations are further evaluated by using the Homotopy Analysis Method (HAM). The variations of entropy rate, velocity, Bejan number and temperature field with the various emerging parameters are analyzed. This could potentially lead to the development of solar energy systems that are both affordable and highly efficient, so enabling the more efficient use of renewable energy sources and reducing our dependence on fossil fuels.

Study on transient thermal state of steel piston in diesel engine under cold start condition

The thermal load issue of pistons remains a topic of active research, especially the transient thermal state of steel pistons in diesel engines under cold start conditions has not been studied in depth. In this paper, a new steel piston power assembly was designed and developed on the basis of a small-bore diesel engine. A real-time temperature test system for the steel piston temperature field was developed to address the problem of the inability to obtain real-time temperature data. The test system was applied to the steel piston to investigate the transient variations in temperature field, thermal stress, and thermal deformation at different starting temperatures. The results show that the temperature field of steel pistons exhibits exponential growth in the early stage of cold start and then tends to stabilize after about 44 s. The lower the cold start temperature and the closer the monitoring points are to the high-temperature combustion gas, the faster the rate of temperature rise. The thermal stress of the steel piston initially increases rapidly, then decreases, and subsequently increases again until reaching a stable level. The lower the starting temperature, the longer the thermal stress inflection point of the monitoring point will be. The variation of thermal deformation of the steel piston follows the same trend as that of the temperature field.

Role of extrinsic factors on magnetoelastic resonance biosensors sensitivity

Magnetoelastic (ME) resonance devices are attractive for application as biosensors in health-related areas as they allow contactless detection of pathogenic agents with high sensitivity. After functionalization, they offer valuable diagnostic options that promote efficient capture of mass on the sensor surface through biological interactions. ME sensors are also sensitive to external factors such as temperature, magnetic fields, and variations in mass that can arise from processes unrelated to biological interactions, including corrosion and salt crystallization. This article evaluates extrinsic factors that affect the response of ME resonance sensors for diagnostic applications. In particular, the influence of heat treatments, operation temperature, applied DC magnetic field bias, and corrosive environment were studied. The control of all these factors is crucial for the design, fabrication, and functionalization of ME resonance biosensors and for the development of measuring instrumentation and effective measurement protocols. This work established maximum operating temperature and bias field variations to keep the sensor sensitivity. Heat treatment of the sensors before and after coating improved the signal-to-noise ratio and corrosion resistance. Further improvement in corrosion resistance was provided by cathodic protection, which has been proven beneficial for applications of ME resonance sensors in aqueous fluids.

Modeling of heat transfer in target material during the electron beam evaporation process

Numerical simulation provides a new method to study the heat and mass transfer behavior during the electron beam evaporation (EBE) process, which can obtain some physical quantities that cannot be accurately measured in experiments. In this study, a mathematical model is established to investigate the evaporation behavior, the variation of temperature field and flow field of target material during the EBE process, and verified through experiments. The results show that the evaporation rate of target material is extremely non-uniform on the molten pool surface, which the calculation error of the evaporation rate was 2.78 %. The solid-liquid interface obtained by numerical simulation is basically consistent with the experiment, which the calculation error of the molten pool depth was 3.57 % and the calculation error of the molten pool width was 1.18 %. In addition, the surface temperature and flow rate of the molten pool increased with the increase of the electron beam power, the depth and the width of the molten pool increased linearly with the increase of the electron beam power and then level off. The model can accurately describe the variations of temperature field and flow field during the EBE process, and then make reliable predictions based on the simulation results.

Temperature Field Characterization of Iron Tailings Based on Microwave Maintenance Technology.

Microwave maintenance technology, as a new development trend, can realize the environmentally noninvasive and rapid repair of asphalt pavement and gradually replace traditional maintenance methods. Iron tailings were used as a self-healing material in this study to investigate the temperature response matching of microwave maintenance technology. Firstly, the physical properties and the mechanism of iron tailings were elaborated through macroscopic physical index testing and microscopic X-ray diffraction (XRD) analysis. Secondly, the applicability of aggregates to microwave heating was demonstrated by analyzing the temperature rise characteristics of the granules using infrared imaging. Then, the temperature field variation rules of the iron tailing asphalt mixture were summarized by microwave heating Marshall specimens. Finally, the road performance was assessed by conducting high-temperature dynamic stability, low-temperature tensile, water immersion Marshall, and freeze-thaw splitting tests. The experimental results showed that the iron tailings can be used as an aggregate for high-grade asphalt pavement and as the preferred aggregate for microwave maintenance technology. The iron tailings temperature field was radial from the inside out to provide different temperature response states for different pavement diseases, so the asphalt was dissolved and precipitated in a short time. The particle size of iron tailings was inversely proportional to the wave-absorbing heating rate, and the heating efficiency of the small particle size (0-4.75 mm) was the highest. The specimens doped with 4.75-13.2 mm iron tailings showed the best heating performance and road performance, with the average surface temperature of the specimens reaching 126.0 °C within 2 min. In summary, according to different disease types and construction needs, iron tailings can be used as an aggregate for asphalt pavement, providing an appropriate temperature field and improving the efficiency of the microwave maintenance of asphalt pavements.

Micro-channel topology optimization based on enhanced heat transfer mechanism

Topology optimization modifies the material distribution in the design domain to produce micro-channel structure with improved thermal performance. In this work, five heat dissipation micro-channel structures with various design domain aspect ratios are optimally designed based on the bi-objective topology optimization method. The optimal design variable fields, temperature fields, and pressure fields are subsequently obtained for each operating condition, and the flow heat transfer effect and the enhanced heat transfer mechanism are investigated under various working conditions. On this basis, the flow heat transfer impact of micro-channels under various operating situations is optimized and studied by combining the field synergy concept and entransy dissipation theory. The findings show that when the Reynolds number rises in the laminar flow region, the complexity of the topological flow channels also rises. The average temperature, Tave,decreases, Nusselt number rises, the inlet and outlet pressure drop, ?P, gradually increases, the integrated enhanced heat transfer factor PEC gradually decreases, the field synergy number, Fc, increases, the pressure drop synergy angle, ?, gradually increases, the entransy dissipation, Evh, increases, and the flow heat transfer performance of each heat dissipation channel is also enhanced due to the complex channels and high Reynolds number in the domain. The investigation of micro-channels with various topologies revealed that the micro-channels with the same boundary conditions and a design domain aspect ratio of 25/64 had the best synergy effects of velocity-pressure gradient and velocity-temperature gradient, the best heat transfer effect, and the best flow characteristics.

Magnetic-field-induced spin reorientation in TmFeO<sub>3</sub> single crystals

TmFeO<sub>3</sub> exhibits rich physical properties such as magneto-optical effect, multiferroicity, and spin reorientation, making it possess significant research value in condensed matter physics and materials science. In this study, we utilize a time-domain terahertz magneto-optical spectroscopy system to investigate the changes in spin resonance frequency of TmFeO<sub>3</sub> single crystal at <i>T</i> = 1.6 K under external magnetic fields in a range of 0–7 T. The TmFeO<sub>3</sub> sample is grown in an optical floating zone furnace and its crystallographic orientation is determined by using back-reflection Laue X-ray photography with a tungsten target. The measurement setup is a self-built time-domain terahertz magneto-optical spectroscopy system, with magnetic fields in a range of 0–7 T, temperatures in a range of 1.6–300 K, and a spectral range of 0.2–2.0 THz. A pair of 1 mm-thick ZnTe nonlinear crystals is used to generate and detect terahertz signals through optical rectification and electro-optic sampling technique. The system variable temperature and magnetic field are controlled by a superconducting magnet. In experiments, a linearly polarized terahertz wave is vertically incident on the sample surface, and its magnetic component <i>H</i><sub>THz</sub> is parallel to the sample surface. By rotating the sample, the angle (<i>θ</i>) between macroscopic magnetic moment <i> <b>M</b> </i> and <i>H</i><sub>THz</sub> can be tuned, achieving selective excitations of the two modes, that is, <i>θ</i> = 0 for q-AFM mode and 90° for q-FM mode. Terahertz absorption spectrum results indicate that as the magnetic field increases, the quasi-ferromagnetic resonance (q-FM) of TmFeO<sub>3</sub> single crystal shifts towards high frequencies, and quasi-antiferromagnetic resonance (q-AFM) transits to q-FM under low critical magnetic fields (2.2–3.6 T). Through magnetic structure analysis and theoretical fitting, it is confirmed that the magnetic moment of the single crystal undergoes magnetic field induced spin reorientation. This study is helpful in better understanding of the regulation mechanism of the internal magnetic structure of rare earth ferrite under the combined action of external magnetic field and temperature field, and also in developing related spin electronic devices.

Effect of component geometry on the dynamic thermal field generated in the laser forming of AA6061-T6 sheet

Laser forming (LF) technology is an advanced, highly customizable non-contact method for shaping metal sheets, characterized by its heightened precision and flexibility. This experimental and numerical study investigates the influence of component geometry on the dynamic temperature field arising from LF of AA6061-T6 sheet metal. Finite element models were constructed to analyse the dynamic temperature field variations in plates with different dimensions. The findings demonstrate the significant effect of sheet dimensions on the induced thermal field, that consequentially affect the deformation. In contrast to a stable heating and cooling profile observed in a 50mm-wide or greater sample, a 20mm-wide or smaller sample exhibits a temperature resurgence or reflection along the laser pathway. The deformation of the aluminium plate therefore decreases with the reduction in geometry size. The analysis of this thermal behaviour helps to explain this and further advances the understanding of the LF mechanism specific to high thermal-conductivity materials.

Study on temperature field distribution state of carbon fiber reinforced polymer wound circular tube via electromagnetic induction heating

The variation of temperature fields during the winding process of CFRP (Carbon Fiber Reinforced Polymer) due to fiber winding is a key factor influencing its curing and shaping. Traditional heating methods result in energy wastage and environmental pollution during the heating process. Electromagnetic induction technology, as a non-contact, pollution-free, and efficient heating method, is playing an increasingly significant role in the process of heating and curing CFRP. This study focuses on two heating methods, internal and external, for CFRP wound circular tubes. It establishes finite element analysis models for induction heating with different coil structures. The heating mechanisms of different coil-induced CFRP wound circular tube models are explained, and the effects of external arc-shaped coils and external/internal annular coils on the temperature field distribution of CFRP wound circular tubes are investigated. By comparing simulations with experiments, the correctness of the numerical analysis model in this study is demonstrated. It offers viable heating methods for different conditions in industrial production, providing theoretical support and empirical data for the induction heating of CFRP wound circular tubes.

МАТЕМАТИЧНЕ МОДЕЛЮВАННЯ ВНУТРІШНЬОСТРУКТУРНИХ ТЕРМОНАПРУЖЕНЬ, ЩО ВИКЛИКАЮТЬСЯ ПОЛЯМИ ЗМІННОЇ ТЕМПЕРАТУРИ В КОМПОЗИТАХ ЗІ СТРИЖНЕВОЮ АРМАТУРОЮ

Introduction. Thermomechanical effects arising in heterogeneous composite materials under the influence of temperature significantly affect the strength and durability of structures made of them. These effects have a special influence on the thermal deformation of bridge and road structures under conditions of seasonal and daily changes in ambient temperature. They are caused by non-uniformity of the thermomechanical parameters of its fractions and fittings. Until now, the phenomenon of thermomechanical deformation of reinforced structures has not been sufficiently studied, therefore the tasks of their research are urgent. Problem Statement. The problem of the performed research is to establish the laws of thermomechanical deformation of composite materials (including cement concrete and asphalt concrete), which are reinforced with reinforcing rods, in the fields of variable temperatures. Purpose. The purpose of the work is to derive mathematical ratios that determine intrastructural thermal stresses in composites caused by variable temperature fields and heterogeneity of materials.

Theoretical Analysis on Thermo-Mechanical Bending Behavior of Timber–Concrete Composite Beams

In this study, an analytical approach is introduced for predicting the bending behavior of a timber–concrete composite (TCC) beam subjected to a mechanical load and a non-uniform temperature field, in which the orthotropy of timber as well as interfacial slip are taken into consideration. The analytical model addresses the non-uniform temperature field using Fourier series expansion based on the heat transport theory. The stresses and displacements of the TCC beam under the thermo-mechanical condition are governed by the thermo-elasticity theory, and the corresponding solution is derived analytically by solving a group of non-homogeneous partial differential equations. The proposed solution is in good agreement with the finite element solution and exhibits higher accuracy compared to the Euler–Bernoulli beam solution that relies on the assumption of transverse shear deformation and isotropy. An extensive investigation is carried out to analyze how the bending behavior of TCC beams is influenced by variations in interfacial shear stiffness and temperature field.

Quantitative test of delamination defects in CFRP with surface interference by laser thermography

Remote onsite inspection and quantitative evaluation of internal delamination defects in carbon fiber reinforced polymer (CFRP) structures is of great significance in practical engineering applications. In this paper, a new method for quantitative test and 3D imaging of internal delamination defects in CFRP with surface interference by long pulse laser thermography is developed. The variation of surface temperature field in a CFRP plate with both defect and surface interference irradiated by a uniform laser source was analyzed by simulation and experiment. Image processing of the collected laser thermography image sequence was carried out to obtain the size and shape of the possible defects. Meanwhile, a method with using the peak time of the temperature difference curve was developed to precisely evaluate the defect depth and eliminate the surface interference. The information was then combined to achieve 3D visualization imaging of the actual defects.

Monitoring experiment and simulation on solidification of DNAN based melt‐cast explosive with FBG sensors

AbstractIn order to obtain the change rule of the temperature field and the mechanism of defect formation during the solidification process of melt‐cast explosive, the temperature field change data were tested during the solidification process of DNAN based melt‐cast explosive by using an arrayed spatially distributed Fiber Bragg Grating (FBG) temperature sensor device. The temperature field variation during the solidification experiment was obtained under the condition that the cooling rate of the boundary water‐bath temperature was 0.2 °C/min. On the basis of the solidification experiments, the macroscopic solidification process of small‐caliber grenade at different boundary cooling rates was simulated using ProCAST software. The simulation results show that when the boundary cooling rate is 0.2 °C/min, the temperature fields during the solidification process of DNAN based melt‐cast explosive are in good agreement with that of the experimental monitoring points; the size of the melt‐cast charge defects decreases as the boundary cooling rate becomes smaller; and the location of the charge defects is closer to the tail of the grenade as the cooling rate decreases. In addition, a mesoscopic model of DNAN based melt‐cast explosive was established in the paper. At the mesoscopic level, the generation, formation, and evolution of charge defects in DNAN based melt‐cast explosive during solidification were investigated. The study results provide theoretical guidance for the formulation design and process optimization of DNAN based melt‐cast explosives, as well as for improving the charge quality of ammunition.

Flexural–torsional buckling of steel circular arches with I-section under central concentrated load in elevated-temperature environment

This article reports the fire resistance experiments conducted on I-section circular steel arches, as well as the observed out-of-plane flexural–torsional buckling (FTB) behavior and in-depth finite element numerical simulation results. The test was carried out using a large fire test furnace to provide a real fire environment with a nonuniform temperature field. A specially designed loading device allowed for unconstrained out-of-plane deformation of the specimens inside the furnace, thereby achieving effective load conditions and noncoupled response of the components. Numerical analyses were performed using a combination of the general codes Fluent and Abaqus, with the former used for heat transfer analyses, and a structural FE model including the loading device and complex geometric imperfections was established based on the measured data. Thus, accurate simulation of the out-of-plane behavior of the steel arches at elevated temperature was achieved. On this basis, an in-depth parametric study was carried out to investigate the effects of temperature field variations, load ratio (LR), and geometric imperfection. The analysis results show that FTB occurs at nonuniform temperatures for the arches under concentrated load, and the difference in temperature distribution in fire has a minimal effect on the FTB behavior. LR is negatively correlated with critical temperature; the smaller the LR, the more significant the weakening of critical loads by fire. The effect of initial geometrical imperfections on FTB at elevated temperatures is similar to that at ambient temperatures, and the effect on the critical temperature of FTB can almost be ignored when the imperfection amplitude is less than S/400.