scholarly journals The nonstationary thermoelectric elasticity problem for a long piezoceramic cylinder

2021 ◽  
pp. 181-190
Author(s):  
D. A Shlyakhin ◽  
M. A Kalmova
Keyword(s):  
Thermal Conductivity ◽  
Temperature Field ◽  
Heat Conductivity ◽  
The Body ◽  
Body Volume ◽  
Outer Face ◽  
External Temperature ◽  
Measuring Device ◽  
Wall Boundary Conditions ◽  
Temperature Load

А new closed-loop solution for the coupled nonstationary problem of thermoelectric elasticity is designed for a long piezoceramic radially polarized cylinder. The case of the nonstationary load acting on its inner cylindrical surface is considered as a function of temperature change at a given law of the convection heat exchange on the outer face wall (boundary conditions of heat conductivity of the 1st and 3rd types). Electrodynamic cylinder surfaces are connected to a measuring device with a high input resistance (electric idling). We investigate the problem where the rate of the temperature load changes does not affect the inertial characteristics of the elastic system. It makes it possible to expand the initial linear computational relations with the equilibrium, electrostatics and heat conductivity equations with respect to the radial component of the displacement vector, electric potential as well as the function of temperature field changes. Hyperbolic LS-theory of the thermal conductivity is used in the computations. The problem is solved with a generalized method of biorthogonal finite integral transformation based on a multicomponent ratio of eigen functions of two homogeneous boundary value problems. The structural algorithm of this approach allows identifying a conjugated operator, without which it is impossible to solve non-self-conjugated linear problems in mathematical physics. The resulted computational relations make it possible to determine the stress-strain state, temperature and electric fields induced in the piezoceramic element under an arbitrary external temperature effect. By connecting the electroelastic system to the measuring tool, we can find voltage. Firstly, the analysis of the numerical results allows identifying the rate of the temperature load changes, at which it is necessary to use the hyperbolic theory of thermal conductivity. Secondly, it allows determining the physical characteristics of the piezoceramic material for the case when the rate of changing the body volume leads to a redistribution of the temperature field. The developed computational algorithm can be used to design non-resonant piezoelectric temperature sensors.

Increasing the Work of the Diamond Grinding Circuits for the Account of Directed Changes in the Heat Conductivity of a Polymer Matrix

2018 ◽  
Vol 935 ◽  
pp. 84-88
Author(s):  
Zalim N. Deunezhev
Keyword(s):  
Thermal Conductivity ◽  
Numerical Simulation ◽  
Temperature Field ◽  
Polymer Matrix ◽  
Heat Conductivity ◽  
Thermal Load ◽  
Polymer Binder ◽  
Diamond Grinding ◽  
The Matrix ◽  
Grinding Circuits

Numerical simulation has been used to study the temperature field in a diamond-containing composite on a polymer matrix. It is shown that an increase in the thermal conductivity of the matrix due to fillers provides a reduction in the thermal load on the polymer binder.

scholarly journals MATHEMATIC MODEL OF AND METHOD FOR SOLVING THE DIRICHLET HEAT-EXCHANGE PROBLEM FOR ONE-SHEET ROTARY HYPERBOLOID

2020 ◽  
Vol 1 (126) ◽  
pp. 23-36
Author(s):  
Mykhailo Berdnyk
Keyword(s):  
Temperature Field ◽  
Heat Conduction ◽  
Boundary Problem ◽  
Heat Conductivity ◽  
Integral Transformation ◽  
Mathematic Model ◽  
The Body ◽  
Initial Moment ◽  
Thin Wall ◽  
Conductivity Equation

It is the first generalized 3D mathematical model developed for calculating temperature fields in the thin-wall one-sheet rotary hyperboloid, which rotates with constant angular velocity around the axis OZ, ; the model was created with the help of known equations of generating lines in cylindrical coordinate system with taking into account finite velocity of heat conductivity and in the form of the Dirichlet boundary problem for the hyperbolic equation of heat conduction under condition that heat-conduction properties of the body were constant, and no internal sources of the heat were available. At initial moment of time, the body temperature was constant; values of temperature on outside surfaces of the body were known and presented continuous function of coordinate.The hyperbolic heat-conductivity equation was derived from the generalized energy transfer equation for the moving element of continuous medium with taking into account finiteness of the heat conductivity velocity.In order to solve the boundary problem, the desired temperature field was represented as a complex Fourier series. The obtained boundary problems for the Fourier coefficients were found with the help of Laplace integral transformations and the new integral transformation for two-dimensional finite space. Intrinsic values and intrinsic functions for the integral transformation kernel were found by method of finite element and the Galerkin methods. Besides, the domain was divided into simplex element.As a result, the temperature field in the thin-wall one-sheet rotary hyperboloid was found in the form of convergent series in Fourier functions.

Stochastic Analysis of Temperature Distribution in a Solid With Random Heat Conductivity

1988 ◽  
Vol 110 (1) ◽  
pp. 23-29 ◽  
Author(s):  
Da Yu Tzou
Keyword(s):  
Thermal Conductivity ◽  
Temperature Distribution ◽  
Heat Conductivity ◽  
Stochastic Analysis ◽  
Solid Medium ◽  
Mean Value ◽  
Random Response ◽  
Thermal Failure ◽  
Numerical Examples ◽  
The Mean

Stochastic temperature distribution in a solid medium with random heat conductivity is investigated by the method of perturbation. The intrinsic randomness of the thermal conductivity k(x) is considered to be a distribution function with random amplitude in the solid, and several typical stochastic processes are considered in the numerical examples. The formulation used in the present analysis describes a situation that the statistical orders of the random response of the system are the same as those of the intrinsic random excitations, which is characteristic for the problem with extrinsic randomness. The maximum standard deviation of the temperature distribution from the mean value in the solid medium reveals the amount of unexpected energy experienced by the solid continuum, which should be carefully inspected in the thermal-failure design of structures with intrinsic randomness.

Measuring the Thermo-Technical Parameters of Autoclaved Aerated Concrete

2016 ◽  
Vol 824 ◽  
pp. 100-107 ◽  
Author(s):  
Alena Struhárová
Keyword(s):  
Thermal Conductivity ◽  
Moisture Content ◽  
Physical Properties ◽  
Bulk Density ◽  
Capillary Absorption ◽  
Measuring Device ◽  
Technical Parameters ◽  
Autoclaved Aerated Concrete ◽  
Aerated Concrete ◽  
Technical Properties

Bulk density and moisture content are factors that significantly affect the physical properties of autoclaved aerated concrete (AAC) including thermal conductivity and other thermo-technical characteristics. This article shows the results of measurements of compressive strength, capillary absorption, water absorption and porosity of AAC (ash on fluidized fly ash) at different bulk density and also the results of thermal conductivity of AAC at different bulk density and variable moisture content of the material. The thermo-technical properties were measured using the Isomet 2104, a portable measuring device. Acquired results demonstrate dependence of physical properties including thermal conductivity of AAC on bulk density and moisture content. The reliability and accuracy of the method of measuring was also shown.

Method of Lines to Solve 2-D Steady Temperature Field of FGM

2007 ◽  
Vol 353-358 ◽  
pp. 2003-2006 ◽  
Author(s):  
Wei Tan ◽  
Chang Qing Sun ◽  
Chun Fang Xue ◽  
Yao Dai
Keyword(s):  
Thermal Conductivity ◽  
Temperature Field ◽  
Transfer Problem ◽  
Method Of Lines ◽  
Main Idea ◽  
Functionally Graded ◽  
Temperature Fields ◽  
Steady Temperature ◽  
Thermal Transfer ◽  
Steady Temperature Field

Method of Lines (MOLs) is introduced to solve 2-Dimension steady temperature field of functionally graded materials (FGMs). The main idea of the method is to semi–discretized the governing equation of thermal transfer problem into a system of ordinary differential equations (ODEs) defined on discrete lines by means of the finite difference method. The temperature field of FGM can be obtained by solving the ODEs with functions of thermal properties. As numerical examples, six kinds of material thermal conductivity functions, i.e. three kinds of polynomial functions, an exponent function, a logarithmic function, and a sine function are selected to simulate spatial thermal conductivity profile in FGMs respectively. The steady-state temperature fields of 2-D thermal transfer problem are analyzed by the MOLs. Numerical results show that different material thermal conductivity function has obvious different effect on the temperature field.

scholarly journals Thermal conductivity of silicon doped by phosphorus: ab initio study

2018 ◽  
Vol 35 (4) ◽  
pp. 717-724
Author(s):  
B. Andriyevsky ◽  
W. Janke ◽  
V.Yo. Stadnyk ◽  
M.O. Romanyuk
Keyword(s):  
Thermal Conductivity ◽  
Heat Conductivity ◽  
Phonon Scattering ◽  
Theoretical Calculations ◽  
Doped Semiconductors ◽  
Silicon Crystals ◽  
Coefficient Of Thermal Conductivity ◽  
Silicon Doped ◽  
Scattering Time ◽  
Phosphorus Doped

Abstract An original approach to the theoretical calculations of the heat conductivity of crystals based on the first principles molecular dynamics has been proposed. The proposed approach exploits the kinetic theory of phonon heat conductivity and permits calculating several material properties at certain temperature: specific heat, elastic constant, acoustic velocity, mean phonon scattering time and coefficient of thermal conductivity. The method has been applied to silicon and phosphorus doped silicon crystals and the obtained results have been found to be in satisfactory agreement with corresponding experimental data. The proposed computation technique may be applied to the calculations of heat conductivity of pure and doped semiconductors and isolators.

scholarly journals Development of Upper-Limb Assist Suit for Reduction Physical Load in Leaf Photosynthesis Measurement

2020 ◽  
pp. 185-190
Author(s):  
Toshitake Araie ◽  
◽  
Ikeda Tomozumi ◽  
Akira Kakimoto ◽  
Shunsuke Adachi ◽  
...  
Keyword(s):  
High Risk ◽  
Upper Limb ◽  
Photosynthetic Capacity ◽  
Evaluation Methods ◽  
The Body ◽  
Physical Load ◽  
Leaf Photosynthesis ◽  
Measuring Device ◽  
Risk Of Injury ◽  
Work Posture

Agricultural tasks result in significant strain on the arms, thereby necessitating posture support. One such task is measuring the photosynthetic capacity of individual leaves. This task requires the operator to hold a measuring device for long periods, which is physically demanding. This study aims to develop an assist suit to reduce the physical load involved in photosynthesis measurement work. We used work posture evaluation methods to quantify the workload of this task and identified the parts of the body at high-risk of injury. Then, we designed an assist suit based on the required specifications and verified its effectiveness.

scholarly journals Gait Assistive Exoskeleton Device For Semi Paralyzed Stroke Survivors

2019 ◽  
Vol 8 (5C) ◽  
pp. 1562-1566
Keyword(s):  
Time Management ◽  
The Body ◽  
Human Gait ◽  
Stroke Survivors ◽  
Walking Ability ◽  
Software System ◽  
Measuring Device ◽  
True Time ◽  
Exoskeleton Device

dominant human gait could be a dynamic and time crucial activity and so it needs a true time management surroundings. the most objective is to regain the walking ability for semi-paralyzed stroke affected patients and to assist them walk severally with none support. MEMS measuring device device senses the walking movements of the patient’s healthy leg. By victimisation these values as reference, microcontroller is programmed and interfaced to the motor fastened within the body covering device. Microcontroller is employed to manage the motor in line with the input given by the measuring device. Microcontroller is programmed victimisation PIC CCS Compiler software system. Associate in Nursing body covering device for semi paralytic patients is developed to exercise their muscles and to revive the sensation of walking in their legs at a way lower value than that is offered on the market nowadays

scholarly journals Теплопроводность цепочки ротаторов с двухбарьерным потенциалом взаимодействия

2021 ◽  
Vol 63 (7) ◽  
pp. 975
Author(s):  
А.П. Клинов ◽  
М.А. Мазо ◽  
В.В. Смирнов
Keyword(s):  
Thermal Conductivity ◽  
Heat Conductivity ◽  
Normal Modes ◽  
Double Barrier ◽  
One Dimensional ◽  
Internal Barrier ◽  
Local Fluctuations ◽  
Small Height ◽  
Coefficient Of Thermal Conductivity ◽  
Height Dependence

The thermal conductivity of a one-dimensional chain of rotators with a double-barrier interaction potential of nearest neighbors has been studied numerically. We show that the height of the "internal" barrier, which separates topologically nonequivalent degenerate states, significantly affects the temperature dependence of the heat conductivity of the system. The small height of this barrier leads to the dominant contribution of the non-linear normal modes at low temperatures. In such a case the coefficient of thermal conductivity turns out to be the risen function of the temperature. The growth of the coefficient is limited by local fluctuations corresponding to jumps over the barriers. At higher values of the internal barrier height, dependence of the heat conductivity on temperature is similar to that of classical rotators.

Darcy-Forchheimer flow with variable thermal conductivity and Cattaneo-Christov heat flux

2016 ◽  
Vol 26 (8) ◽  
pp. 2355-2369 ◽  
Author(s):  
T. Hayat ◽  
Taseer Muhammad ◽  
Saleh Al-Mezal ◽  
S.J. Liao
Keyword(s):  
Thermal Conductivity ◽  
Temperature Field ◽  
Velocity Field ◽  
Thermal Relaxation ◽  
Heat Transfer Process ◽  
Relaxation Parameter ◽  
Content Type ◽  
Opposite Behavior ◽  
Non Linear System ◽  
Forchheimer Flow

Purpose The objectives of present communication are threefolds. First is to model and analyze the two-dimensional Darcy-Forchheimer flow of Maxwell fluid induced by a stretching surface. Temperature-dependent thermal conductivity is taken into account. Second is to examine the heat transfer process through non-classical flux by Cattaneo-Christov theory. Third is to derive convergent homotopic solutions for velocity and temperature distributions. The paper aims to discuss these issues. Design/methodology/approach The resulting non-linear system is solved through the homotopy analysis method. Findings An increment in Deborah number β causes a reduction in velocity field f′(η) while opposite behavior is observed for temperature field θ(η). Velocity field f′(η) and thickness of momentum boundary layer are decreased when the authors enhance the values of porosity parameter λ while opposite behavior is noticed for temperature profile θ(η). Temperature field θ(η) is inversely proportional to the thermal relaxation parameter γ. The numerical values of temperature gradient at the sheet − θ′(0) are higher for larger values of thermal relaxation parameter γ. Originality/value To the best of author’s knowledge, no such consideration has been given in the literature yet.

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