Mobile Heat Source Research Articles

Thermal and residual stress analysis of multi-pass welded stainless steel pipes using DEFLUX and FILM subroutine

This study presents an in-depth investigation of the influence of welding parameters (welding speed and number of passes) on the residual stress distribution in AISI 304 (Z7CN18-09) austenitic stainless-steel tubes. A three-dimensional finite element modeling (FEM), developed in ABAQUS, was implemented to simulate the circumferential welding process. The DFLUX and FILM subroutines were implemented to model the double ellipsoid mobile heat source and thermal boundary conditions, respectively. Model validation was performed by comparing weld bead profiles and thermal cycles with experimental results, showing excellent correlation (deviation < 5%). The coupled thermal and mechanical analyses allowed evaluation of the spatiotemporal evolution of the temperature field for different welding speeds (80-160-240 mm/min) and the distribution of axial and circumferential residual stresses as a function of tube thickness. The numerical results demonstrate a significant influence of these parameters on the amplitude and distribution of residual stresses, with a notable reduction in maximum stresses for optimized welding speeds and better stress homogenization with multi-pass welding.

Advanced A-B fractional modeling of nonlocalized viscoelastic polymer micro-rod caused by mobile heat source including fractional strain

Current investigation is aimed to develop the concept of fractional derivatives proposed by Atangana–Baleanu that captures the memory effects of heat transfer and stress–strain relation inside a nonlocal viscoelastic polymer micro rod affected from a mobile heat input. Laplace Transform algorithm is bestowed to stimulate the closed-form solutions of temperature, displacement, thermal stress. Structured mechanism of numerical inversion of Laplace Transform is carried out for obtaining the quantitative outcomes in physical domain. Impacts of the fractional parameter, fractional order strain quantity, nonlocal parameter, and heat source velocity are analyzed. Results under fractional derivatives reveal stable characteristics of thermal waves.

Особенности инициирования подвижным источником энергии реакций в плоском слое, расположенном на подложке

In the conditions of the surface treatment of materials and coating application using mixtures of powders (metals, metals and nonmetals, metals and oxides) capable of chemical interactions, problems similar to those of solid-phase combustion theory arise. Currently available publications, which confirm the fact of the reactions, are limited to the analysis of the obtained structures, mechanical properties and the statement of the presence of certain compounds and phases. We present the reduced models for the synthesis of composites on a planar substrate allowing us to analyze qualitative effects. The first model is one-dimensional with a total reaction. The second model corresponds to the synthesis of a matrix-inclusion-type composite. The process is assumed to be driven by a moving heat source. Both models take into account the properties of the substrate. The transition to dimensionless variables reveals both the parameters characteristic of macrokinetics and the parameters typical for modern material synthesis technologies. The numerical solution shows that in the presence of a mobile heat source the reaction zone is sufficiently wide, and the temperature dynamics in general is dissimilar to that of combustion processes. It is shown that there is a parameter region in which partial transformation is observed. Two characteristics of the synthesis process have been determined - the time of the reaction initiation and the time of half-transformation (for a sample of finite size). Taking into account detailed kinetics, similar studies allow us to predict the qualitative composition of synthesis products when changing the conditions and initial composition of powder mixtures.

Detection of surface moving heat source using experimental temperature measurements on the opposite surface and inverse techniques

The identification of mobile sources is a widely researched area in multiple scientific and technical domains. Detecting mobile heat sources is an essential task in different fields, including fire safety, environmental monitoring, material science, and energy systems. In this investigation, we present an innovative solution to solve the inverse problem of detecting mobile heat sources, utilizing a three-dimensional transient inverse heat conduction problem (IHCP) formulation. The goal is to identify a moving heat source from thermographic infrared measurements of the rear face. The proposed method includes a finite volume approach with model reduction techniques to improve computational efficiency. Additionally, we use the conjugate gradient method to solve the inverse problem. We verified the proposed approach by conducting experiments on a metal plate with a moving heat source from a laser and comparing recalculated temperature of the front face with thermocouple measurements. Our results indicate that our method can detect the location and trajectory of the mobile heat source with high accuracy and efficiency. This study also highlighted the limits of source speed that can be detected by this method. This technique could be considered as an excellent option for real-time monitoring of mobile heat sources in practical applications.

An analytical model and experimental validation of annular heat source during scanning electron beam treatment

In this investigation, the maximum depth of penetration and power density coefficient are calculated by simulating the motion trajectories of electrons in surface layer of 5CrNiMo steel using Monte Carlo method, and the number of electrons is 500,000 in simulation. Then tomographic calculation is used to determine the distribution of power density coefficient on the section perpendicular to electron incidence direction, and a Gaussian columnar heat source model that matches the properties of electron beam is established. Finally, a mobile annular heat source model of scanning electron beam is then derived, combining it with the real operating mode. The temperature field during surface modification is simulated by using the mobile annular heat source model, and the simulation findings are compared to experimental data. The findings of Monte Carlo simulation demonstrate that the power density coefficient is Gaussian distributed on the section perpendicular to the depth of electron incidence and the peak power density at the center of each section changes with depth. The thickness and microstructure of re-melting layer predicted from the temperature field simulation is very close to the one from experimental findings. In our investigation, on top of deriving a model for the heat source of a single beam spot, we have also solved the problem of mathematical representation of the beam spot when it is doing high-speed rotational and linear composite motions. The aforementioned findings demonstrate that our study can provide methodological references for the construction of heat source models for different materials during electron beam treatment.

Simulation Investigation on Thermal Characteristics of Thermal Battery Activation Process Based on COMSOL

Current thermal simulation methods are not suitable for small-size fast-activation thermal batteries, so this paper provides an improved simulation method to calculate thermal cell temperature changes using the COMSOL platform. A two-dimensional axisymmetric model of thermal batteries has been established, considering the actual heat release situation and the mobile heat source of thermal batteries. Based on it, the temperature change and electrolyte melting of thermal batteries under high-temperature conditions (50 °C) have been simulated, in which the temperature change law, thermal characteristics, and electrolyte melting characteristics have been analyzed in depth. The results show that the additional heating flakes and insulation design above and below the stack can effectively reduce heat loss. Most of the melting heat of the electrolyte flows in from the negative side. In addition, the thermal battery activation time has been calculated to be 91.2 ms at the moment when all the thermal battery electrolyte sheets begin to melt, and the absolute error was within 10% compared with the experimental results, indicating that the simulation model has high accuracy and can effectively broaden the simulation area of thermal batteries.

Study on the optimal process parameters for stripping the X-ETFE insulation layer of aviation wires by a small semiconductor laser

A reasonable laser wire stripping process parameter set is a prerequisite for high-quality and high-efficiency wire stripping. For the X-ETFE insulated wire used in aviation, this study explores the method of obtaining the optimal stripping process parameters based on a 405 nm wavelength semiconductor laser. Build energy conversion model, mobile heat source model, and finite element simulation numerical model of the laser stripping insulating layer process. Based on the single-factor analysis method, simulate the effect of laser power, scanning speed, and processing time on the kerf width, heat-affected zone width, and cutting seam depth of the insulating layer. The results show that increasing the laser power to improve the stripping efficiency will also increase the width of the kerf and heat-affected zone, and increasing the scanning speed can effectively reduce the kerf width. A reasonable combination of laser power and scanning speed can improve stripping efficiency while ensuring quality. According to the single-factor simulation analysis results, select the possible value levels for each parameter to carry out the actual laser wire stripping orthogonal test. There is a good correspondence between the range analysis results of the test data of each stripping quality evaluation index and the conclusions obtained from the single-factor simulation, which verifies the reliability of getting the optimal combination of laser stripping process parameters through the orthogonal test.

Ambient-air in situ fabrication of high-surface-area, superhydrophilic, and microporous few-layer activated graphene films by ultrafast ultraviolet laser for enhanced energy storage

Microporous graphene-based (MPG) films have attracted tremendous attention in micro-energy storage devices due to their unique characteristics of high specific surface area (SSA), high flexibility and high conductivity. However, current fabrication technologies generally provide overall activation in the form of powder in the bulky tube furnace, and multi-stepped thin film forming process, hurdling their practical utilizations that require efficient, cost-effective and controllable methods for large-area MPG films. Herein, a one-step and scalable laser induction & activation technique is reported for in situ fabrication of decimeter-level few-layer MPG films by utilizing ultrafast ultraviolet laser as a mobile heat source acting on microstructured polyimide film coated with KOH in air, which enable directly regulating the activation area on a flexible substrate. The resulting laser-induced and activated graphene (LIAG) films have interconnected hierarchical porous structures containing ultra- (0.5–0.8 nm) and super-micropores (~1.2 nm), high SSA (>1300 m2 g−1), small amount of doped potassium (~0.50 wt%), and super-hydrophilicity (maximum droplet spreading velocity reaches 424.7 mm s−1). With the well-balanced properties of SSA, heteroatom doping, bulk density, and crystalline size, the LIAG micro-supercapacitors with interdigital electrodes of 35 µm width gap achieve a maximum areal capacitance of 128.4 mF cm−2, which outperforms state-of-the-art laser-processed carbon-based micro-supercapacitors. Additionally, it achieves almost the highest comprehensive evaluation considering processing precision, efficiency, cost and environmental friendliness. The facile, efficient, binder-free fabricability and roll-to-roll process compatibility would provide a rapid route for high-performance flexible energy storage devices.

Calculation of aerial contact wire volume heated by a moving electric ARC

The article is devoted to the study of the problem of electrified railways electric locomotive current collectors’ interaction violation with an aerial contact wire, accompanied by the occurrence of an electric arc. Current collection disorders, accompanied by arcing, have a destructive effect on the contacting elements, causing their thermal erosion. Places where current collection violations occur should be registered and diagnosed in a timely manner in order to prevent an emergency situation associated with burnout or breakage of the aerial contact wire. In order to further develop the system of technical diagnostics for current collection disorders accompanied by arcing, it is necessary to study the nature and parameters of the processes occurring during these violations. The main part of the article is devoted to the study of the area of heating the aerial contact wire by a moving electric arc. The characteristics describing the heated area are geometric parameters, including the area in the cross section of the wire and the volume of the area. To obtain the necessary data, the method of heat sources was applied, which is a mathematical model that describes the process of heat propagation in an aerial contact wire. The electric arc arising when the current collector breaks off is considered as a mobile heat source distributed over the aerial contact wire surface in the heating zone and having a limited radius of the heating spot. Based on the heat propagation process peculiarities inside the aerial contact wire, a method for calculating the volume of the heated area bounded by an isothermal surface of a certain temperature is presented. The heated area was visualized using the PTC MathCAD.

Temperature field characterization and optimization of temperature field distribution in pipe lining process based on electromagnetic induction heating system

It is a promising treatment strategy to use an induction heating system for pipe lining, which can void the low efficiency and difficult temperature control of the traditional flame and hot air heating. In this study, a novel finite element model of pipe scanning induction heating was established, and the reliability of the model was verified through experiments. In addition, through the Plackett-Burman design, the main factors affecting the temperature fluctuation at 5 mm of the lining layer are analyzed. Finally, based on the analysis results, the system parameters were optimized by response surface method and the parameter configuration of the induction heating system with the minimum temperature fluctuation of 5 mm lining layer was obtained. The model established in this paper greatly reduces the calculation time of the electromagnetic induction heating finite element model of the moving magnetic field. It can be applied to the temperature information prediction of the lining induction heating where high-temperature accuracy is required and provides a reference for the characterization of the lining induction heating system and its application in low-temperature heat treatment, and the modeling strategy can be extended to the characterization of the temperature field evolution of any mobile heat source.

Stability of Panels of a Thermoelastic Shell Heated at the Edge by a Mobile Point Source

The thermostability of thin-walled structures is considered by means of a thermoelasticity problem in a three-dimensional quasi-static formulation. Finite-element models of panels in the form of a circular cylinder and a plate reinforced by ribs are constructed. Numerical solutions are obtained for the stability loss of thermoelastic thin-walled reinforced structures with intense edge heating by a mobile heat source.

Heat distribution in electric hot incremental sheet forming

Electric hot incremental sheet forming (EHISF) is a technique based on the use of electric current to heat the metal sheet, it consists of a source of direct current (transformer), cables, tool, and plate constituting a closed circuit. According to Joule’s law, when the current travels from the tool to the plate, the current density generates heat. It is known that the mechanical and metallurgical proprieties of the materials are highly influenced by the temperature. Then it is important to know how the distribution of heat near the mobile heat source occurs. Recently, some researchers have suggested different techniques for calculating heat distribution as a function of a mobile source. In this paper, it discusses the temperature distributions when the source moves in relation to the conductive medium, comparing the equation proposal by Bejan the numerical simulation using an explicit finite element method, which has a suitable formulation for inserting the effects of temperature and strain rate in the material. The results show that for the conditions evaluated the model proposed by Bejan (Eq. 4) is very close to the results obtained by the numerical simulation. Moreover, as EHISF is a process with large deformations and time-consuming, it would be necessary to include the terms of the energy of plastic deformation (E) and also the loss by convection to better represent the distribution of heat in the plate.

Natural convection induced by an optically fabricated and actuated microtool with a thermoplasmonic disk.

Two-photon polymerization was employed for fabricating microtools amenable to optical trapping and manipulation. A disk feature was included as part of the microtools and further functionalized by electron-beam deposition. The nanostructured gold layer on the disk facilitates off-resonant plasmonic heating upon illumination with a laser beam. As a consequence, natural convection characterized by the typical toroidal shape resembling that of Rayleigh-Bénard flow can be observed. A velocity of several μm·s-1 is measured for 2μm microspheres dispersed in the surroundings of the microtool. To the best of our knowledge, this is the first time that thermoplasmonic-induced natural convection is experimentally demonstrated using a mobile heat source.

Temperature Field Simulation of Powder Sintering Process with ANSYS

Aiming at the “spheroidization phenomenon” in the laser sintering of metal powder and other quality problems of the forming parts due to the thermal effect, the finite element model of the three-dimensional transient metal powder was established by using the atomized iron powder as the research object. The simulation of the mobile heat source was realized by means of parametric design. The distribution of the temperature field during the sintering process under different laser power and different spot sizes was simulated by ANSYS software under the condition of fully considering the influence of heat conduction, thermal convection, thermal radiation and thermophysical parameters. The influence of these factors on the actual sintering process was also analyzed, which provides an effective way for forming quality control.

Analysis of the Thermal Characteristics of Machine Tool Feed System Based on Finite Element Method

The loading of mobile heat source and boundary conditions setting are difficult problems in the analysis of thermal characteristics of machine tools. Taking the machine tool feed system as an example, a novel method for loading of mobile heat source was proposed by establishing a function which was constructed by the heat source and time. The convective heat transfer coefficient is the key parameter of boundary conditions, and it varies with the temperature. In this paper, a model of “variable convection heat transfer coefficient” was proposed, and the setting of boundary conditions of thermal analysis was closer to the real situation. Finally, comparing results of above method and experimental data, the accuracy and validity of this method was proved, meanwhile, the simulation calculation and simulation time was reducing greatly.

The use of non-linear inverse problem and enthalpy method in GTAW process of aluminum

This work presents an alternative approach for the thermal analysis of the GTA (Gas Tungsten Arc) welding process on a 6065 T5 aluminum alloy. For this purpose, a C++ code was developed, based on a transient three-dimensional heat transfer model with phase change and mobile heat source. The thermal model took into account the dependence of thermal properties on temperature and heat losses by convection and radiation. The convection heat transfer coefficient and the emissivity were also considered variables with the temperature. To estimate the amount of heat delivered to the plate, the BFGS (Broydon–Fletcher–Goldfarb–Shanno) technique was used. Moreover, an analysis of the duration time of the electrode in positive (t+) and negative (t−) polarities was carried out. The methodology was validated by accomplishing lab controlled experiments. The aluminum samples lay on four conical head screws and submitted to a heat flux on one surface by the GTAW process torch. The torch displaces along the sample, thus simulating a real process. The numerical results presented low deviation when compared to the experimental results, which in turn, confirm the validation of the methodology for the study of the welding process presented.

THERMALLY INDUCED VIBRATION OF A FUNCTIONALLY GRADED MICRO-BEAM SUBJECTED TO A MOVING LASER BEAM

In this paper, the thermally induced vibration of a functionally graded (FG) cantilever micro-beam subjected to a moving laser beam is investigated via simulating the equivalent third-order dynamic system. The material properties of the FG micro-beam are defined by an exponential function through the thickness. The coupled thermo-elastic equations are obtained utilizing the first law of thermodynamics under the assumption of the classical Fourier heat conduction model and Euler–Bernoulli beam theory. To evaluate the dynamic response of the micro-beam, the coupled equations are first discretized by employing a Galerkin based reduced-order model and then decoupled by applying the Cramer's rule. Solving the decoupled equations analytically, effects of key parameters are illustrated by means of time histories and phase portraits. Furthermore, by investigating the case of resonant excitation, the critical velocity corresponding to mobile heat source is obtained.

Temperature regulation and tracking in a MIMO system with a mobile heat source by LQG control with a low order model

A multi-input multi-output (MIMO) thermal control problem in real-time is investigated. An aluminum slab is heated on one side by a mobile radiative heat source and cooled on the other side by a fan panel. Starting from a nominal steady state configuration of heat power, source position and ventilation level, the objective is to control temperature at 3 chosen locations on the rear side when the nominal ventilation level is subject to disturbances. The main features of this paper are: (i) the use of the heat source power and its displacements in both directions along the plate as actuators, which is the principal originality of this work, (ii) the use of a low order model identified from experimental data by the Modal Identification Method to perform state feedback control in real time (t=2s) through a Linear Quadratic Gaussian (LQG) compensator, instead of a (large-size) heat transfer model, and (iii) the study of the effect of the control time period, the LQG parameters and the order of the model. Both thermal regulation and tracking problems have been addressed. Results show promising future developments involving more actuators and controlled outputs.

Chronic Opioid Potentiates Presynaptic but Impairs Postsynaptic N-Methyl-d-aspartic Acid Receptor Activity in Spinal Cords: IMPLICATIONS FOR OPIOID HYPERALGESIA AND TOLERANCE

Chronic Opioid Potentiates Presynaptic but Impairs Postsynaptic N-Methyl-d-aspartic Acid Receptor Activity in Spinal Cords: IMPLICATIONS FOR OPIOID HYPERALGESIA AND TOLERANCE

Measurement and Simulation of Residual Stresses of Electron Beam Welding Joint of Pure Aluminum

The effects of electron beam welding on the residual stresses of welded joints of pure aluminum plate 99.60 are studied by through-hole-drilling and blind-hole-drilling method. Meanwhile, based on the thermal elastic-plastic theory, and making use of ANSYS finite element procedure, a three - dimensional finite element model using mobile heat source of temperature and stresses field of electron beam welding in pure aluminum is established. The welding process is simulated by means of the ANSYS software. The results show that the main residual stress is the longitudinal residual stress, the value of the longitudinal residual stress is much larger than the transverse residual stress. But the residual stress in the thickness is rather small. And in the weld center, the maximum value of residual stresses is lower than its yield strength. The simulation results about the welded residual stresses are almost identical with the experimental results by measuring. So the research result is important to science research and engineering application.