Time-varying Temperature Field Research Articles

Research on the calculation method of grinding temperature field of spiral bevel gear based on generative machining

At present, the process parameter setting of spiral bevel gear grinding is mainly based on an empirical method, and the tooth surface temperature is difficult to estimate effectively during grinding, which may lead to excessive tooth surface temperature and surface burn caused by improper selection of process parameters. Aiming at the above problems, this paper presents a method for calculating the temperature field of spiral bevel gear forming based on a combination of analytical and numerical methods. The motion equation of spiral bevel gear grinding is derived based on the method of tooth surface development. The time-varying heat flow calculation method in tooth surface grinding was developed through the discrete and two-dimensional contact zone. The time-varying temperature field analysis method of spiral bevel gear forming is developed using the time-varying heat flow and finite element calculation method. The related research can realize the temperature prediction of grinding tooth surfaces and provide the basis for improving grinding technology.

Numerical and Experimental Analysis of Strength Loss of 1.2709 Maraging Steel Produced by Selective Laser Melting (SLM) under Thermo-Mechanical Fatigue Conditions.

The result of the development of additive manufacturing (AM) methods is the increasing use of the selective laser melting (SLM) method as a technique for producing tooling for injection moulds and die casting pressure moulds from maraging steel powders. The mould components are subjected to varying thermo-mechanical loads during these operations. This paper presents a numerical model that is used to predict the fatigue life of a material that is loaded with a time-varying temperature field according to the classic and modified Coffin test. Using a computational model, the temperature changes in the resistance-heated specimen and the stress and strain fields that are caused by this phenomenon were determined. Using three different multiaxial fatigue criteria, the fatigue life of SLM steel was determined. Numerical calculations were verified using experimental thermal fatigue tests on 1.2709 SLM steel that was aged at 490 °C as well as via metallographic tests. The numerical model was used to predict the durability of the same steel aged at 540 °C. The effect of specimen clamping conditions on the fatigue life of SLM steel was determined numerically. The value of the decrease in strength of SLM steel as a result of the increasing number of cycles of temperature changes was determined experimentally; a great influence of ageing temperature on fatigue life was found. Changes in the structure of steel occurring during cyclic changes in temperature are presented.

Thermal dynamics of gold nanoshell dimers under femtosecond laser pulse irradiation: A numerical approach.

We present a numerical investigation of the photothermal response of gold nanoshell (AuNS) dimers when subjected to femtosecond laser pulse irradiation. The time-varying temperature fields for core-shell AuNS dimers are quantified by implementing finite element modeling, integrating the electromagnetic and thermal dual-physics simulations. Given the ultrafast nature of laser pulses, we employ a two-temperature model to accurately portray the energy transfer from excited electrons to the lattice system, a process typically completed post pulse-termination. The temporal analysis of the temperature in the AuNS and the surrounding medium, together with the spatial temperature distribution under different separation distances, elucidates the processes that drive the AuNS dimers' transient temperature distribution and heat dissipation. We report on the critical effects of geometrical parameters on the photothermal response, demonstrating that thinner shells maximize the total deposited energy per unit volume, resulting in increased temperature fields, while decreasing separation distances result in excessive field amplification due to plasmonic modes' production. Our robust numerical approach, enabling simulations with tunable material properties and configurations, may help design nanomaterials with desired features for photothermal cancer treatment and imaging.

Deformation prediction of large-span spatial structure considering adverse weather conditions

For exposed large-span spatial structures affected by solar radiation, the temperature field of the structure is time-varying and non-uniform. Currently, the research on the transient temperature field of the structure is based on the ideal sunny day, and the impact of adverse weather is usually not considered. Such simplification leads to inaccurate prediction results of temperature deformation of steel structures, especially during the construction process of the steel structure, when the structural deformation prediction needs to be employed to control the structural spatial configuration after completion. In this paper, a new method is proposed to predict the time-varying and non-uniform temperature field of large-span spatial structures using the limited information of weather forecasts. A large-span steel truss structure with inclined leg is employed to illustrate and discuss the parameters of the daily temperature model, and the temperature field of the structure under different weather conditions is calculated using a simulation program based on MATLAB and ANSYS. Finally, the accuracy of the simulation results is verified by the monitored data. The results show that the optimized daily temperature model is well predicted for the actual temperature change under different weather conditions. The structure temperature field and effect of different weather conditions have observable differences and the weather factors cannot be ignored. When the structural member reaches the highest temperature afternoon, all the temperature difference of the member exceeds 20% under different weather conditions.

Simultaneous estimation of time-varying temperature field and boundary heat flux in participating medium by the improved Kalman filter algorithm

Simultaneous estimation of time-varying temperature field and boundary heat flux in participating medium by the improved Kalman filter algorithm

An experimental device for measuring the internal temperature and pressure of rock for rock breaking by pulsed discharge in petroleum exploitation

In order to measure the variation of temperature and pressure inside rock subjected to pulsed discharge, a device for measuring the temperature and pressure inside rock is designed in this work. The device is composed of an excitation module and a signal module. Based on the analysis of pulsed discharge process, the structure of key components of the device was designed. The experiment of rock breaking by single pulsed discharge was conducted. The peak values of temperature and pressure inside sandstone rock samples of 20 cm*20 cm*20 cm were measured when they were broken at 8 different voltage levels in the range of 2.5 kV–20 kV. It was found that with the increase of voltage level, the temperature and pressure inside the rock were also significantly increased when the rock was broken. At the maximum 20 kV voltage, the temperature peak inside the rock is 398 °C and the pressure peak is 2.4 MPa. The temperature and pressure inside the rock rose dramatically as it broke. This device can monitor temperature and pressure inside rock during the rock breaking process, and its embedded computer can construct time-varying temperature field and pressure field with transmitted temperature and pressure signals. This technically supports theoretical research on rock breaking by pulsed discharge.

Evaluation of temperature distribution for bone drilling considering aging factor

Bone drilling is a routine operation in surgeries, such as neurosurgery and orthopedics. However, the excessive drilling temperature may cause severe thermal damage to the bone tissue. Therefore, the drilling temperature determination of bone tissue can reduce the harm caused by thermal damage. A time-varying temperature field simulation model of bone drilling was set up by ABAQUS software in this paper, based on the Johnson-Cook model. Then it was validated with experiments by drilling cortical bone of fresh bovine shaft of the femur. The relative error between the experimental values and the theoretical values within 7.67% showed a good consistency. Furthermore, the aging factor is also considered to evaluate the temperature field of bone drilling. The results showed that the drilling temperature near the bone-drill area increased significantly. The drilling temperature of cortical bone decreases sharply with the radial distance and exhibits a hysteresis lag in the axial distribution. The aging factor mainly affects the peak of drilling temperature. The peak of drilling temperature tends to increase with age. The peak drilling temperature in the elderly (70y) was up to 6.8% higher than that in the young (20y), indicating that the elderly is more prone to excessive drilling temperature. Therefore, special attention should be paid to the temperature control of elderly bone tissue.

Heat transfer analysis of infrastructures subjected to environmental actions: A finite element solver PAT

• Thermal behavior of infrastructures exposed to environmental actions is studied. • An open source FEA code considering environmental boundary conditions is developed. • Face tilt angle and azimuth are automatically computed. • A solar radiation model is implemented. • The numerical predictions show a good approximation to the monitoring results. The non-uniform and time-varying temperature field caused by annual and daily temperature cycles and the differences in the solar radiation exposition of the surfaces have a significant effect on the infrastructure response (displacements, strains and stresses). Therefore, before performing the mechanical analysis for the critical assessment of the structural condition, it is mandatory to proceed with the determination of the temperature distribution. Contrary to other thermal load, environmental actions vary in daily and annual cycles. Moreover, solar radiation also depends on the orientation of the surface with respect to the Sun rays. Therefore, a conventional thermal finite element code should be modified in order to deal with these two particular issues. The aim of this paper is to describe the solution strategies that allow the application of the environmental boundary conditions in a finite element analysis and to provide an open source code to the community that deals with the safety of critical infrastructures. Two different examples illustrate the good performance of the developed code.

Singularly Perturbed Solution of Non-Fourier Temperature Field with Mixed Boundary Value Dual-Phase Delay with Thermal Conductivity Jumps

Based on the properties of laminates, a class of nonlinear singularly perturbed mixture equations with discontinuous coefficients over bounded domains is constructed by using a dual-phase delayed heat conduction model. First, the singular perturbation expansion method is used, combined with the corresponding boundary conditions, the partial differential equation method and the Laplace transform method are used to obtain the external solution, the boundary layer, and the corner layer. Secondly, the time-varying temperature field at the discontinuity is obtained, which leads to the asymptotic expansion of the solution. Finally, the consistent validity of the asymptotic solution is obtained through residual estimation.

Study on the Time-Varying Characteristics of In-Situ State Temperature Field of Drilled Work Piece Based on Unsteady Heat Conduction

In-Situ state heat conduction in drilling workpiece results in time-varying temperature field, which affects the final machining accuracy. From the joint action of many factors, such as geometry, material, and thermal convection characteristics, it is difficult to accurately model and describe the time-varying characteristics of the temperature field. Therefore, the time-varying model of the In-Situ state temperature field is analyzed in this paper, which lays a foundation for establishing a high-precision multi-physical field model. First, following the geometric characteristics of the drilling hole and the three-dimensional heat transfer mechanism, the heat transfer model of the drilled part is established, and the relationship between the temperature field and the physical parameters of the workpiece is characterized. Then, combining radial and axial unsteady heat conduction mechanisms, the dimensionless temperature calculation method is adopted to realize the construction of a temperature time-varying model. After that, the model parameters are revised according to the In-Situ state evolution process of the checkpoints. Finally, the experiments are carried out to calculate the credibility of the model. The results show that the prediction model is consistent with the experimental data, and the credibility of non-room temperature dynamic interval is 99.23%, which can effectively reflect the real temperature field conduction process.

A deep learning method for estimating thermal boundary condition parameters in transient inverse heat transfer problem

Estimating thermal boundary condition parameters in the transient inverse heat transfer problem (IHTP) is characterized by instability and non-uniqueness of the solution. This study formulated a simple method based on deep learning, which can realize multi-dimensional real-time prediction of thermal boundary condition parameters. The proposed model combining convolutional neural network (CNN) and long short-term memory networks (LSTM) allowed estimating multiple time-varying parameters based on the time-varying temperature field image of the target. The data-driven model used the computational fluid dynamics (CFD) method to obtain the numerical data, and the influence weight of the parameters was introduced in the training process to improve the generalization ability of the model. An experiment on the cubic cavity was made to verify the reliability of the proposed model to estimate time-varying parameters. The studies we have performed showed that the proposed hybrid models outperformed the standalone models (CNN, LSTM) in estimating multiple time-varying parameters. In the experimental results, the relative errors of air temperature and humidity were only 2.33% and 4.33%, respectively. These attempts of introducing the deep learning method to the IHTP in the present study were successful and it was significant for the study of the transient inverse heat transfer problem.

Thermoviscoelastic dynamics of composite thin-walled booms on spacecrafts subjected to solar radiation

Viscoelastic behavior of polymer-matrix composites depends very strongly on temperature. This paper presents a thermoviscoelastic dynamics modelling for fiber-reinforced polymeric composite structures with time-varying and nonuniform temperature field. It is used to investigate the thermally induced vibrations of spacecraft booms, for which a new anisotropic thin-walled beam model based on the generalized beam theory is also proposed. Furthermore, efficient evaluation of the thermoviscoelastic constitutive equations in hereditary integral form is performed by means of the derived recursion formula. A harmonic balance procedure in the circumferential direction of tubular booms is devised for both thermal and structural analyses. By comparing the results of viscoelastic and elastic models, the influence of thermoviscoelastic effects on dynamical responses of composite booms under thermal shock is illustrated. The results show that viscoelasticity may play a significant role in vibration suppression of on-orbit flexible structures, especially at high temperature. The work not only provides a novel model for thermal-structural dynamic analysis, but also develops thermoviscoelasticity theory oriented toward engineering and numerical applications.

Ray tracing and finite element modeling of sound propagation in a compartment fire

A compartment fire (a fire in a room or building) creates temperature gradients and inhomogeneous time-varying temperature, density, and flow fields. This work compared experimental measurements of the room acoustic impulse/frequency response in a room with a fire to numerically modeled responses. The fire is modeled using a Fire Dynamics Simulator (FDS). Acoustic modeling was performed using the temperature field computed by FDS. Room acoustics were modeled using two-dimensional ray and finite element modeling. A three-dimensional model was used to simulate an open flame. COMSOLTM Multiphysics was used for finite element acoustic modeling and BELLHOPTM for ray trace acoustics modeling. The results show that the fire causes wave-fronts to arrive earlier (due to the higher sound speed) and with more variation in the delay times (due to the sound speed perturbations). The resonance frequencies of low-frequency modes were shifted upwards. Model results are compared with data and show good agreement in observed trends.

Study of the Hydration Temperature Field in the Hinge Seal Layer for a Large-Volume UHPC Arch Base

For large arch bridges, the sealing hinge layer at the arch footing is critical to the long-term performance and durability of the structure. This study investigated the temperature distribution of the sealing hinge layer inside a large UHPC arch seat during the hydration process in a natural environment, based on a design of a 600-m-span reinforced concrete rigid skeleton arch bridge. A certain suggestion for the design of a large-volume UHPC layer was proposed through the consideration of temperature and age effects of the thermal field solid finite element analysis of early-age UHPC hydration heat. The results show that UHPC has a hydration induction period of 10 h and reaches the peak temperature of 69°C in 20 h. Then, the hydration heat is gradually released in 70 h after pouring. The maximum temperature difference between the core and surface reaches 40°C. The results also show that the early temperature field and heat release rate of UHPC are affected by initial temperature. The actual heat release of some materials of UHPC components at 75 h is equivalent to that at 300 h, and the minimum effective age was found close to 100 h, where the heat release reaches 0.25 of the total heat release. A simplified algorithm for the spatially time-varying non-linear temperature field of the UHPC sealing hinge layer under the influence of temperature and age is proposed, which provides a simple calculation method for the temperature control of the UHPC arch seat during the hydration process in real projects.

Internal resonance of hyperelastic thin-walled cylindrical shells under harmonic axial excitation and time-varying temperature field

In this paper, the internal resonance characteristics of hyperelastic cylindrical shells under the time-varying temperature field are investigated for the first time, and the evolution of the isolated bubble is carried out. Through the analysis of the influences of temperature on material parameters, the hyperelastic strain energy density function in the unsteady temperature field is presented. The governing equations describing the axisymmetric nonlinear vibration are derived from the nonlinear thin shell theory and the variational principle. With the harmonic balance method and the arc length method, the steady state solutions of shells are obtained, and their stabilities are determined. The influences of the discrete mode number, structural and temperature parameters on the nonlinear shell behaviors are examined. The role of the parameter variation in evolution behaviors of isolated bubble shaped responses is revealed under the condition of 3:1 internal resonance. The results manifest that both structural and temperature parameters can affect the resonance range of the response curve, and the perturbed temperature has a more significant effect on the stable region of the solution.

Head-related transfer function measurements in a compartment fire.

The Personal Alert Safety System (PASS) is an alarm signal device carried by firefighters to help rescuers locate and extricate downed firefighters. A fire creates temperature gradients and inhomogeneous time-varying temperature, density, and flow fields that modify the acoustic properties of a room. To understand the effect of the fire on an alarm signal, experimental measurements of head-related transfer functions (HRTF) in a room with fire are presented in time and frequency domains. The results show that low-frequency (<1000 Hz) modes in the HRTF increase in frequency and higher-frequency modal structure weakens and becomes unstable in time. In the time domain, the time difference of arrival between the ears changes and becomes unstable over time. Both of these effects could impact alarm signal detection and localization. The receive level of narrowband tones is presented that shows that the fire makes the receive level of a source vary by > 10 dB. All of these effects could impact the detection and localization of the PASS alarm and have life safety consequences.

Efficient numerical solution of the volume integro-differential equation for time-varying temperature fields in heterogeneous media

An efficient numerical method for calculation of time-varying temperature fields in an infinite homogeneous medium containing heterogeneous inclusions is presented. The medium is subjected to distributed or localized heat sources. The problem is reduced to the integro-differential equation for the temperature fields in the regions occupied by the inclusions only. For numerical solution, this equation is discretized using Gaussian radial functions for approximation of spatial-dependence and piece-wise constant functions for approximation of time-dependence of the temperature fields. For Gaussian approximating functions, the elements of the matrix of the discretized problem are calculated in explicit analytical forms. The iterative minimal residual method and fast Fourier transform technique are used for solution of the discretized problems at a sequence of time moments. The numerical algorithms for solution of the discretized equations are presented for 1D, 2D, and 3D heterogeneous media. Numerical solutions are compared with exact and approximate solutions in the cases of spherical layered inclusions subjected to distributed and localized heat sources.

The Evolving Temperature Field in a 1 m Methanol Pool Fire.

Thin filament pyrometry is used to measure the time-varying temperature field in a 1 m methanol pool fire. A digital camera with optical filters and zoom lens recorded the emission intensity of an array of 12 μm Silicon-Carbide filaments oriented horizontally at various heights across the steadily burning pool fire. A 50 μm diameter thermocouple measured the temperature at locations corresponding to the filament positions. A correlation was developed between the local probability density functions of the thermocouple time series measurements corrected for radiation and thermal inertia effects and the camera grayscale pixel intensity of the filaments. A regression analysis yields the local mean temperature and its variance. The time series of the temperature field is transformed into average values during consecutive phases of the fire's puffing cycle, providing quantitative insight into the complex and dynamic structure of a turbulent fire.

Numerical analysis on the time-varying temperature field distribution patterns of ballastless track steel-concrete composite box girders at ambient temperature based on field measurements

To analyze the time-varying temperature field distribution pattern of ballastless track steel-concrete composite box girders for a high-speed railway at ambient temperature, a numerical model for analyzing the time-varying temperature field of steel-concrete composite box girders was established based on the long-term monitoring data for the internal and external environments of the main girder of the Ganjiang Bridge on the Nanchang-Ganzhou high-speed railway. The influence of factors such as the deck pavement and the ambient wind speed on the time-varying temperature field of the steel-concrete composite box girders were considered. The results showed that there was a significant difference in the vertical temperature gradient patterns on sections at the side web and at the middle web at the same moment in time due to the hindering effect of the track board on the heat exchange between the ambient temperature and the main girder. Increasing the wind speed accelerated the rate of heat exchange between the main girder surface and the environment. In particular, when the internal temperature of the girder was higher than the ambient temperature, the higher the wind speed was, the larger the temperature gradient was. This study lays a foundation for accurate analysis of the structural response of ballastless track steel-concrete composite girder bridges at ambient temperature.

Effective thermal conductivity of particulate composites for time-varying temperature fields

A homogeneous conductive medium containing random sets of identical spherical inclusions is considered. The self-consistent effective medium method is used for solution of the homogenization problem and calculation of the effective thermal conductivity parameters of the composite. For time-varying fields, the effective conductivity parameters are non-local operators with respect to time. The effective medium method allows reducing the homogenization problem to solution of a system of non-linear equations for the Laplace transforms of the kernels of these operators. An efficient numerical algorithm of solution of this system is proposed. Examples of construction of these operators for the composites with copper and glass phases are considered. The Green functions of the corresponding effective media are compared with the Green function of the media with static effective parameters of thermal conductivity.