Transient Thermal Distribution Research Articles

Temperature and stress distributions during laser cutting with different materials

Laser cutting is an extremely precise and versatile industrial technique that utilizes a focused laser beam to accomplish precise and accurate material cutting or engraving. Because of its efficiency and adaptability, laser cutting has become an essential component of modern production and design. The transient thermal and stress distribution of laser cutting of a sheet is introduced numerically in this study. Temperature, equivalent elastic strain, and equivalent stresses at different workpiece materials (structural steel, titanium alloy, and aluminum alloy) are investigated. Three different laser beams (500 W, 1000 W, and 1500 W) were used in this study. The modeling applies a heat source based on a Gaussian distribution to predict heat flow with an accurate temperature distribution field. The numerical model is validated with experimental data, and the error percentage is consistent and reasonable. The results showed that titanium could attain higher temperatures for the material of the workpiece under the same working conditions as both stainless steel and aluminum alloy. In comparison to stainless steel, the temperature increase ratios for titanium and aluminum are 121 % and 113.5 %, respectively. Aluminum expands rapidly, structural steel endures stresses, and titanium withstands high temperatures effectively. In comparison to 500 W, the temperature rise ratios for laser beams of 1000 W and 1500 W are 174 % and 237 %, respectively. These results highlight how critical it is to select the ideal laser power dependent on the properties of the material, adding to a more sophisticated knowledge for increased accuracy and effectiveness in laser cutting procedures.

Numerical simulation on melt pool and solidification in the direct energy deposition process of GH3536 powder superalloy

Rapid melting, solidification, and a highly powerful laser all contribute to complex heat transfer and flow phenomena during the directed energy deposition (DED) process. To investigate the impact of process parameters on the melt pool and solidification quality during the DED process, a three-dimensional finite element model (FEM) was established. The heat transfer, fluid flow, and solidification during the DED process were investigated. The correct input parameters for GH3536 superalloy were discovered by examining the effects of laser power, scanning speed, and feed rate on the shape of molten pool and interlayer fusion. To forecast the quality of the solidified structure at the cut-off point, temperature gradient and solidification rate discovered in transient thermal distribution were employed. The results shows that the melt pool will grow as a result of high laser power and low scanning speed or feed rate. Concentrating on the expansion of the melt pool is not the best solution because well-solidified microstructure frequently develops in the middle of the parameter set. The correlation between feed rate and laser power is insensitive. At a specific feed rate, the minimum threshold for scanning speed was discovered. When the scanning rate falls below the threshold, uneven solidification structures and anomalous melt pool morphology will take place. The undesirable and potentially fluctuating parameters were indicated, and the laser power and scanning speed range suited for the GH3536 superalloy were summarized. For the feed rate, the center of the parameter set is advised.

Induced magnetic transportation of Soret and dissipative effects on Casson fluid flow towards a vertical plate with thermal and species flux conditions

This research offers an analysis of the mixed convective transient boundary film Casson fluid stream and thermal distribution through a vertical sheet. Viscous dissipation and the Soret effect are introduced to support the flow in stimulating heat capacity. Unlike typical investigations, the present flow-formulated model is done to capture an induced magnetic field. The Boussinesq approximation is used to describe the nonlinear formulated partial derivatives governing the heat transfer fluid that is non-dimensionalized using suitable dimensionless quantities. The transformed partial derivative model is numerically solved via the spectral Chebyshev technique and the results of shear stress, current density, Nusselt number, and mass gradient are tabulated. The role of numerous terms on dimensionless flow rate, induced velocity, and heat transfer with species distribution is discussed in a very effective way. Velocity and temperature of liquid decline as boosting the material parameter. Enhancing values [Formula: see text] favor the flow momentum and oppose the temperature profile.

Efficient transient thermal analysis of chiplet heterogeneous integration

Thermal issue has significant effect on the reliability and performance of integrated circuits with the increase of integrated density, especially for 2.5-D and 3-D heterogeneous integration packaging systems. In this paper, a new highly efficient 3-D transient thermal distribution model has been constructed to capture the heat conduction behavior of multiple heat sources for chiplet heterogeneous integration (CHI) by improving the alternating direction implicit finite difference method (ADI-FDM). Firstly, a new floating optimization algorithm (FOA) of coefficient matrix assignment of heat conduction equation and a new boundary treatment utilizing virtual points are proposed to modify the ADI-FDM and improve the model efficiency of thermal analysis. Furthermore, a universal equivalent thermal conductivity model is also built up to describe the design features of through silicon via (TSV), bump and redistribution layer structures, which can enhance the flexibility of FDM-based thermal simulator. Compared with previous finite element analysis results, the present FOA-accelerated thermal model can not only obtain an accurate simulation result of temperature profile, but also give a simulation efficiency of 3.74 times faster than Douglas-Gunn approach for the coefficient matrix assignment. Finally, the effect of power consumption variation and the floorplaning effects of chiplets, TSVs and bumps on the temperature distribution are investigated in detail by utilizing the present FOA-based thermal solver. The simulated results of the present work demonstrate the viability and computational efficiency for temperature field optimization and indicate that the new proposed simulator is helpful in thermal analysis of packaging structures and can be adopted to assist in physical design optimization of 2.5-D CHI or 3-D heterogeneous stacked chips.

Artificial Neural Network Modeling for Predicting the Transient Thermal Distribution in a Stretching/Shrinking Longitudinal Fin

AbstractThis study emphasizes the aspects of heat transfer and transient thermal distribution through a rectangular fin profile when a stretching or shrinking mechanism is mounted on the surface of the fin. Furthermore, the effects of radiation, internal heat generation, and convection are all considered when developing the corresponding fin problem. The simulated time-dependent heat transfer equation is a partial differential equation that can be represented by dimensionless arrangement using appropriate nondimensional terms. The nonlinear dimensionless problem concerning the stretching/shrinking of a fin is numerically solved using the finite difference method (FDM), and the Levenberg–Marquardt method of backpropagation artificial neural network (LMM-BANN) has been used in this investigation. By varying the stretching/shrinking parameter, a set of data for the presented artificial neural network (ANN) is produced to discuss stretching and shrinking scenarios. The testing, training, and validation procedure of LMM-BANN, as well as correlation for verification of the validity of the proposed approach, establish the approximate solution to stretching/shrinking scenarios. The suggested model LMM-BANN is then validated using regression interpretation, mean square error, and histogram explorations. The ANN results and the procured numerical values agree well with the current numerical results.

Assessment of transient thermal distribution in a moving porous plate with temperature-dependent internal heat generation using Levenberg–Marquardt backpropagation neural network

ABSTRACT In the present paper, the transient temperature distribution within a moving porous plate is scrutinized by considering the internal heat generation, convection and radiation condition. Furthermore, an effective artificial intelligence technique is proposed for discussing the transient thermal behavior in a moving plate by employing the Levenberg-Marquardt backpropagation network. Using suitable non-dimensional terms, the governing partial differential equation (PDE) is transformed into its non-dimensional form. The transformed equation is then solved using the finite difference method (FDM) and the obtained thermal values (datasets) are used as target values in the process of neural network mapping. This network uses the training, testing, and validation processes to determine the solution of several scenarios established at various process times. The behavior of dimensionless transient temperature profile has been inspected for diverse values of non-dimensional parameters such as heat generation number, radiative parameter, porosity parameter, and conductive parameter with the assistance of graphs. The significant outcomes elucidate that, the transient temperature profile of the porous plate increases with the change in time. Further, it enriches for rise in the magnitude of Peclet number and heat generation number while it drops for enhanced values of porosity parameter.

Significance of non-Fourier heat conduction in the thermal analysis of a wet semi-spherical fin with internal heat generation

The transient temperature distribution of a wet semi-spherical porous fin with convection, internal heat generation, and radiation is researched using a non-Fourier heat conduction (NFHC) model. A mathematical model for transient heat transfer in a dehumidifying environment is developed from the non-Fourier law and the corresponding governing equation is formulated. This equation is subjected to nondimensionalization using suitable dimensionless terms and is further solved by employing the finite difference method (FDM). A substantial deviation in thermal response by considering non-Fourier law under unsteady heat transmission has been analyzed graphically with the influence of various nondimensional parameters on the dry and wetted fins surface. The examination reveals the notable difference in temperature variation between the dry and wetted fins surfaces. Some important key results of the research analysis include that the transient thermal distribution through the fin decrease as the magnitude of the convective, wet porous and radiation-conduction parameters develop. For higher generating numbers, thermal distribution will be higher. The temperature in the hyperbolic model increases after some time in the existence of relaxation time and the temperature in a non-Fourier model flow in the form of a thermal wave.

Experimental and numerical study on the transient heat transfer process for fluoride salt-to-air cooler

In order to better characterize the transient thermal behavior of Fluoride salt-to-Air Cooler (FAC) and then to forecast the risk of freezing under variable load, the numerical and experimental studies of the cooling of fluoride salts have been performed. Results show that the simulated thermal parameter is in agreements with the experiment data with a maximum deviation below 20%, which validate the reliability of the CFD model. Then, a detailed 3D CFD transient thermal process related flow distributions are conducted. Results show that the air-outlet velocity has a sudden rise at the immediate blower operating condition, but the transient thermal process will be worked well. Finally, the air-temperature response and fluoride-salt minimum temperature are evaluated considering the transient progression. Results show that gentle changes to the blower flowrate can effectively mitigate potential to overcool the salt and avoid solidification. Which offer helpful guidance for FAC transient regulation and operation.

A physical depiction of a semi-spherical fin unsteady heat transfer and thermal analysis of a fully wetted convective-radiative semi-spherical fin

The current investigation scrutinizes non-Fourier heat conduction law to describe transient temperature variation through a convective-radiative wetted semi-spherical fin with internal heating. The fin is fully wetted with a hybrid nanofluid containing MnZnFe2O4−NiZnFe2O4 nanoparticles and water or methanol (methyl alcohol (MA)) as base liquids. Dimensionless terms are used to nondimensionalize the energy equation, and the finite difference method (FDM) is used to solve the nonlinear partial differential equation (PDE). In addition, graphs are drawn to explore the impact of several non-dimensional attributes on the temperature gradient, such as radiation-conduction, convection-conduction, and internal heat production parameters for hybrid nanofluid containing MnZnFe2O4 and NiZnFe2O4 nanoparticles with different base liquids. The major findings of the study show that as the magnitude of the wet parameter, and radiation-conduction parameters increases, the transient thermal distribution through the fin drops. Thermal distribution, on the other hand, improves for the parameter of heat generation.

LES study on the turbulent thermal stratification and thermo-mechanical fatigue analysis for NPP surge line

Thermal stratification caused the significant temperature differentials from top to bottom inside the pipe that imposed fluctuating high stresses on the wall of the pipe and eventually could lead to severe structural integrity concerns and degrade fatigue strength. This study aimed to evaluate the transient thermal distribution and fatigue damage caused by thermal stratification in the pressurizer surge line (SL) of Nuclear Power Plants (NPP). In this paper, the effects of nonuniform temperature distributions caused by thermal stratification were investigated by performing a detailed Computational Fluid Dynamic (CFD) study using the Large Eddy Simulation (LES) approach. The fluid flow was simulated using a full buoyancy model and conjugate heat transfer at the pipe inner wall and the fluid interface. Numerical results of the investigation in the SL pipe were validated with similar experimental setup data obtained from a prototype experimental facility of a pressurized water reactor. Fatigue damage due to induced thermal stresses in the SL model was investigated and fatigue hotspots were also identified. This work provides a comprehensive case study of thermal stratification for estimating pressurizer surge pipeline structural integrity.

Exploration of transient heat transfer through a moving plate with exponentially temperature-dependent thermal properties

The present research examines the transient temperature distribution through a moving plate with exponentially temperature-dependent thermal conductivity and heat transfer coefficient. Further, the internal heat generation, as well as convective boundary condition, is considered. The governing energy equation describing the transient heat transfer is formulated and is transformed into a non-dimensional partial differential equation (PDE) using appropriate non-dimensional terms. The resultant PDE is solved numerically with the assistance of the finite difference method (FDM). The consequence of embedding parameters on the transient thermal profile of a moving plate is explicated through a graphical description. The results reveal that the transient thermal distribution decreases remarkably with an upsurge of convection–conduction parameter and the same trend is perceived for radiation–conduction parameter. The result also manifests that as the plate moves faster, the transient thermal distribution through a moving plate enhances gradually. The higher variation in the thermal distribution is perceived for elevated values of the exponential index of thermal conductivity. Moreover, the nature of transient temperature distribution is compared for linear and exponentially temperature-dependent thermal conductivity.

Analysis of Transient Thermal Distribution in a Convective–Radiative Moving Rod Using Two-Dimensional Differential Transform Method with Multivariate Pade Approximant

The transient temperature distribution through a convective-radiative moving rod with temperature-dependent internal heat generation and non-linearly varying temperature-dependent thermal conductivity is elaborated in this investigation. Symmetries are intrinsic and fundamental features of the differential equations of mathematical physics. The governing energy equation subjected to corresponding initial and boundary conditions is non-dimensionalized into a non-linear partial differential equation (PDE) with the assistance of relevant non-dimensional terms. Then the resultant non-dimensionalized PDE is solved analytically using the two-dimensional differential transform method (2D DTM) and multivariate Pade approximant. The consequential impact of non-dimensional parameters such as heat generation, radiative, temperature ratio, and conductive parameters on dimensionless transient temperature profiles has been scrutinized through graphical elucidation. Furthermore, these graphs indicate the deviations in transient thermal profile for both finite difference method (FDM) and 2D DTM-multivariate Pade approximant by considering the forced convective and nucleate boiling heat transfer mode. The results reveal that the transient temperature profile of the moving rod upsurges with the change in time, and it improves for heat generation parameter. It enriches for the rise in the magnitude of Peclet number but drops significantly for greater values of the convective-radiative and convective-conductive parameters.

Methodical procedure of virtual manufacturing for analysing WAAM distortion along with experimental verification

This paper deals with a principal development of virtual manufacturing (VM) procedure to predict substrate distortion induced by Wire Arc Additive Manufacturing (WAAM) process. In this procedure, a hollow shape is designed in a thin-walled form made of stainless steel. The procedure starts with geometrical modelling of WAAM component consisting of twenty-five deposited layers with austenitic stainless-steel wire SS316L as feedstock and SS304 as substrate material. The hollow shape is modelled based on simplified rectangular mesh geometry with identical specimen dimensions during the experiment. Material model to be defined can be retrieved directly from a database or by conducting a basic experiment to obtain the evolution of material composition, characterized using Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray (EDX) analysis, and generated using advanced modelling software JMATPRO for creating new properties including the flow curves. Further, a coupled thermomechanical solution is adopted, including phase-change phenomena defined in latent heat, whereby temperature history due to successive layer deposition is simulated by coupling the heat transfer and mechanical analysis. Transient thermal distribution is calibrated from an experiment obtained from thermocouple analysis at two reference measurement locations. New heat transfer coefficients are to be adjusted to reflect actual temperature change. As the following procedure prior to simulation execution, a sensitivity analysis was conducted to find the optimal number of elements or mesh size towards temperature distribution. The last procedure executes the thermomechanical numerical simulation and analysis the post-processing results. Based on all aspects in VM procedures and boundary conditions, WAAM distortion is verified using a robotic welding system equipped with a pulsed power source. The experimental substrate distortion is measured at various points before and after the process. It can be concluded based on the adjusted model and experimental verification that using nonlinear numerical computation, the prediction of substrate distortion with evolved material property of component yields far better result which has the relative error less than 11% in a comparison to database material which has 22%, almost doubled the inaccuracy.

Numerical investigation of novel process planning in the polymeric powder bed fusion

Multiple-laser and matrix-heat source exposures are emerging systems for powder bed fusion (PBF) to improve productivity. However, the newly available process planning such as scanning patterns may induce different transient thermal distribution and distortion in selective laser sintering or melting process. This work proposes novel scanning strategies for digital process planning in polymer PBF, including contour lines and novel inner scanning patterns. It provides detailed predictions of temperature gradient and distortion upon processing and the shrinkage/warping of printed components. Novel scanning strategies of subarea-sequential, subarea-parallel, and matrix-randomized scanning strategies are addressed here. The thermal-recrystallization-mechanical model for laser sintering is employed to reveal the underlying mechanism upon different process planning strategies. Thereafter, the matrix-randomized scanning mode can obviously reduce the building time of each layer into millisecond level. The advanced subarea-sequential scanning pattern is able to minimize shrinkage and warping. The systemic framework of digital process planning is provided through numerical investigation of scanning strategies and multi-physics modeling, which are an important aspect in the advanced digital twin of additive manufacturing.

Research on water jet-guided laser micro-hole machining of 6061 aluminum alloy

With the rapid development of the information age, electronic components are developing toward miniaturization, which makes the manufacturing of chips more and more difficult. Water jet-guided laser processing technology (WJGL) is a composite processing technology that combines pulsed laser and water jet, which can ensure the accuracy and efficiency of processing while small size parts machining. This paper is based on the “element birth and death” technique in the finite element method and the three-dimensional transient temperature field and subsequent material removal model of 6061 aluminum alloy are established. The effects of laser average power, pulse repetition frequency, and pulse action time on the transient thermal distribution, aperture, taper, and other forming qualities with the two technologies of fixed-point drilling and spiral drilling, respectively, are studied. Combining the experimental process, the general rule of morphology change of the micro-hole is obtained. The results show that WJGL of micro-hole is based on the combined effect of thermal ablation and real-time cooling. Spiral drilling can maintain a better hole shape but fixed-point drilling can achieve a smaller hole taper. With the increase of laser power, the hole taper increases, reaching saturation at 8 W. The repetition frequency is between 50 and 70 kHz to obtain better hole morphology while maintaining better processing efficiency, and the minimum hole taper is 8.21°.

PROWAVES: Proactive Runtime Wavelength Selection for Energy-Efficient Photonic NoCs

2.5-D manycore systems running parallel applications are severely bottlenecked by network-on-chip (NoC) latencies and bandwidth. Traditionally, NoCs are composed of electrical links that exhibit constrained bandwidth, increased energy consumption at high-speed communication, and long latencies. Photonic NoCs (PNoCs) have been shown to provide high bandwidth at low latencies and negligible data-dependent power. However, the power overheads of lasers, thermal tuning, and electrical-optical conversion present major challenges against wide-scale adoption of PNoCs. A primary factor that impacts PNoC power is the number of activated laser wavelengths in the system. Applications’ dynamic bandwidth needs provide the opportunity to selectively deactivate laser wavelengths when there is a lower bandwidth demand to alleviate high PNoC power concerns. This article analyzes dynamic PNoC activity of applications at runtime so as to select laser wavelengths depending on an application’s bandwidth requirements. The article then proposes <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">PROWAVES</i> , a proactive runtime wavelength selection policy that forecasts the bandwidth needs and activates the minimum laser wavelengths for each application phase. We develop a cross-layer simulation framework to model the system performance, PNoC power and transient thermal distribution in a manycore system with PNoCs. We compare <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">PROWAVES</i> with prior system-level policies and our simulation results on a 2.5-D system demonstrate that <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">PROWAVES</i> provides 18% and 33% power savings with only 1% and 5% loss in performance, respectively, compared to activating all laser wavelengths in the system.

Monitoring the Joule heating profile of GaN/SiC high electron mobility transistors via cross-sectional thermal imaging

The development of high-quality gallium nitride (GaN) high electron mobility transistors (HEMTs) has provided opportunities for the next generation of high-performance radio frequency and power electronics. Operating devices with smaller length scales at higher voltages result in excessively high channel temperatures, which reduce performance and can have detrimental effects on the device's reliability. The thermal characterization of GaN HEMTs has traditionally been captured from either the top or bottom side of the device. Under this configuration, it has been possible to map the lateral temperature distribution across the device with optical methods such as infrared and Raman thermometry. Due to the presence of the gate metal, however, and often also the addition of a metal air bridge and/or field plate, the temperature of the GaN channel under the gate is typically inferred by numerical simulations. Furthermore, measuring the vertical temperature gradient across multiple epitaxial layers has shown to be challenging. This study proposes a new cross-sectional imaging technique to map the vertical temperature distribution in GaN HEMTs. Combining advanced cross-sectioning processing with the recently developed near bandgap transient thermoreflectance imaging technique, the full transient thermal distribution across a GaN HEMT is achieved. The cross-sectional thermal imaging of the GaN channel is used to study the effects of biasing on the Joule heating profile. Overall, the direct measurement of the GaN channel, capturing both the vertical and lateral gradient, will provide deeper insight into the device's degradation physics and supply further experimental data to validate previously developed electrothermal models.

Transurethral high-intensity ultrasound for treatment of stress urinary incontinence (SUI): simulation studies with patient-specific models

Background: Stress urinary incontinence (SUI) is prevalent in adult women, attributed to weakened endopelvic supporting tissues, and typically treated using drugs and invasive surgical procedures. The objective of this in silico study is to explore transurethral high-intensity ultrasound for delivery of precise thermal therapy to the endopelvic tissues adjacent to the mid-urethra, to induce thermal remodeling as a potential minimally invasive treatment alternative.Methods: 3D acoustic (Rayleigh–Sommerfeld) and biothermal (Pennes bioheat) models of the ultrasound applicator and surrounding tissues were devised. Parametric studies over transducer configuration [frequency, radius-of-curvature (ROC)] and treatment settings (power, duration) were performed, and select cases on patient-specific models were used for further evaluation. Transient temperature and thermal dose distributions were calculated, and temperature and dose metrics reported.Results: Configurations using a 5-MHz curvilinear transducer (3.5 × 10 mm, 28 mm ROC) with single 90 s sonication can create heated zones with 11 mm penetration (>50 °C) while sparing the inner 1.8 mm (<45 °C) radial depth of the urethral mucosa. Sequential and discrete applicator rotations can sweep out bilateral coagulation volumes (1.4 W power, 15° rotations, 600 s total time), produce large volumetric (1124 mm³ above 60 EM43 °C) and wide angular (∼50.5° per lateral sweep) coverage, with up to 15.6 mm thermal penetration and at least 1.6 mm radial urethral protection (<5 EM43 °C).Conclusion: Transurethral applicators with curvilinear ultrasound transducers can deliver spatially selective temperature elevations to lateral mid-urethral targets as a possible means to tighten the endopelvic fascia and adjacent tissues.

Modeling of electric and heat processes in spot resistance welding of cross-wire steel bars

AbstractThe aim of this work is the modeling of coupled electric and heat processes in a system for spot resistance welding of cross-wire reinforced steel bars. The real system geometry, dependences of material properties on the temperature, and changes of contact resistance and released power during the welding process have been taken into account in the study.The 3D analysis of the coupled AC electric and transient thermal field distributions is carried out using the finite element method. The novel feature is that the processes are modeled for several successive time stages, corresponding to the change of contact area, related contact resistance, and reduction of the released power, occurring simultaneously with the creation of contact between the workpieces. The values of contact resistance and power changes have been determined on the basis of preliminary experimental and theoretical investigations.The obtained results present the electric and temperature field distributions in the system. Special attention has been paid to the temperature evolution at specified observation points and lines in the contact area. The obtained information could be useful for clarification of the complicated nature of interrelated electric, thermal, mechanical, and physicochemical welding processes. Adequate modeling is also an opportunity for proper control and improvement of the system.

Adaptive real-time model on thermal error of ball screw feed drive systems of CNC machine tools

The positioning error of ball screw feed drive systems is mostly caused by thermal deformation of the ball screw shaft in machine tool feed systems. This paper presents an adaptive real-time model (ARTM) for predicting the temperature transient distribution and thermal error distribution of the ball screw shaft. FEM integrated with the Monte Carlo method is applied to determining the heat generation rates of two bearings, moving nut and two guides in the ball screw feed system. Then based on the data of the FEM calculations, an exponential function of the feed velocity and time is used to describe variation of the temperature difference between the measured surface point and the center of the kinematical pair with time. Finally, a numerical forecasting algorithm is developed to predict the thermal characteristics of the screw shaft and its effectiveness is verified by the experiments.