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This paper aims to present a methodology of finding temperature dependencies of selected physical parameters of metals. The method is based on the combination of measurement of the surface temperature of material during the process of heating and subsequent solution of the inverse problem using multi-parametric optimization.

The methodology is based on measurements and numerical solution of the forward and inverse problem, taking into account all involved nonlinearities (saturation curve of the processed steel material and temperature dependences of its physical parameters). The inverse problem is solved by a genetic algorithm.

The suggested methodology was successfully verified on several metal materials whose temperature-dependent parameters are known. The calculated and measured results exhibit a very good accordance (the differences do not exceed about 10 per cent for room and higher temperatures).

At this moment, the methodology successfully works when the temperature dependence of just one material parameter is to be found (which means that the temperature dependencies of other parameters are known). The accuracy of results also depends on the correctness of other input data.

This paper provides a relatively easy possibility of finding the temperature dependencies of thermal conductivity or heat capacity of various alloys.

The paper proposes a methodology of finding the temperature dependence of a given material parameter that is not known in advance (which is of great importance in case of alloys).

One of the problems encountered by developers of inertial systems, such as gyroscopes and accelerometers, is the critical dependence of the eigenfrequencies of elastic suspensions (ES) on temperature when using substrates for sensors made of dielectric materials, such as borosilicate glass. The internal stresses arising in the ES caused by the difference in the temperature coefficients of linear expansion (TCLE) lead to deformation of the sensor and complication of the electronic part of the sensor. The purpose of this paper is to approach for in-plane and out-of-plane ES are considered that allow for minimization of the influence of internal stresses on eigenfrequencies.

Analytical, finite element and experimental results are considered. The temperature coefficient of thermal expansion, the Young’s modulus and the Poisson ratio are given as a function of temperature. The shape of the spring elements (SEs) and the construction of the elastic suspension are the main topics of focus in this study. The authors’ out-of-plane ES based on a meander-like spring element implemented via finite element modeling show good agreement with the experimental results.

Meander-like SEs have been developed that have lower temperature errors in comparison with traditional types of SEs. The main contribution to the change in the eigenfrequency from temperature is made by internal stresses that arose from the deformation of the bonded materials with different TCLE. The change of eigenfrequency from the temperatures that were calculated by finite element method did not exceed 0.15%, however, in practice, the scatter of the obtained characteristics for different samples showed a change of up to 0.3%.

This study shows a way to design and optimize the structure and theoretical background for the development of the microelectromechanical systems (MEMS) inertial module combining the functions of gyroscope and accelerometer. The obtained results will improve and expand the manufacturing technology of MEMS gyroscopes and accelerometers.

This numerical study explores the influence of the time dependence of material fluid parameters on the transient temperature evolution during the growth of fluid shells. The shell is spherical, the fluid is Newtonian, and the flow is induced by a constant driving pressure. The coupled heat and flow equations are solved numerically using the cobody (Lagrangian) transformation and a central difference discretization in space. The range of material values is adjusted from existing experiments. It is generally found that the variation in viscosity, surface tension and specific heat can have a significant influence on both the growth rate and temperature evolution. Thermal conductivity is found to be of little influence.

The purpose of this study is to model the dependences of the output voltage, temperature, current and electrical power dissipation of a voltage limiter based on a two-layer varistor–posistor structure on time and analysis the influence of operating modes and design parameters of such a limiter on these characteristics.

The behavior of the limiting voltage, temperature and other parameters of the voltage limiter when an input constant overvoltage is applied is studied by the simulation method. The voltage limiter was a two-layer construction. One layer was a zinc oxide ceramic varistor. The second layer was a posistor polymer composite with a nanocarbon filler of PolySwitch technology.

The output voltage across the varistor layer decreases and reaches some fixed value related to its breakdown voltage after applying a constant overvoltage to the structure over time. The temperature of the structure increases to some steady state value, while the current decreases significantly. The amplitude of the transient current pulse increases, its duration and energy of the transient process decrease with increasing overvoltage. An increase in the internal resistance of the overvoltage source can cause a decrease in the amplitude and an increase in the duration of transient currents.

The ranges of values for the activation energy of conduction of the varistor layer in weak electric fields, the intensity of heat exchange between the structure under study and the environment are determined to ensure the stable operation of this structure as a voltage limiter. The results obtained make it possible to select the necessary parameters of the indicated structures to ensure the required operating modes of the voltage limiter for various applications.

The purpose of this paper is to present a new method of measuring thermal resistance of power light-emitting diodes (LEDs). Properties of power LEDs strongly depend on their internal temperature. The value of this temperature depends on the cooling conditions characterized by thermal resistance.

The new method of measuring the value of this parameter belongs to the group of electric methods. In this method, the problem of estimating the value of electrical power converted into light is solved. By comparing the values of the case temperature obtained for the LED operating in the forward mode and the reverse-breakdown mode, the thermal power is estimated. On the basis of the measured value of the thermally sensitive parameter (the LED forward voltage) and the estimated value of the thermal power, thermal resistance is calculated.

The elaborated method was used to measure thermal resistance of the selected types of power LEDs operating at different cooling conditions. The correctness of the elaborated measurement method was proved by comparing the results of measurements obtained with the use of the new method and the infrared method.

On the basis of the obtained results of measurements and the catalog data of the tested diodes, the dependence of the measurement error of thermal resistance of the LED on its luminous efficiency is discussed.

The new measurement method is easy to use and more accurate than the classical method of thermal resistance measurement of the diode.

A methodology for producing an elevated-temperature tension stiffening model is presented.

The energy-based stress–strain model of plain concrete developed by Bažant and Oh (1983) was extended to the elevated-temperature domain by developing an analytical formulation for the temperature-dependence of the fracture energy G_f. Then, an elevated-temperature tension stiffening model was developed based on the modification of the proposed elevated-temperature tension softening model.

The proposed tension stiffening model can be used to predict the response of composite floor slabs exposed to fire with great accuracy, provided that the global parameters TS and K_res are adequately calibrated against global structural response data.

In a finite element analysis of reinforced concrete, a tension stiffening model is required as input for concrete to account for actions such as bond slip and tension stiffening. However, an elevated-temperature tension stiffening model does not exist in the research literature. An approach for developing an elevated-temperature tension stiffening model is presented.

The purpose of this paper is to present modelling of power losses dependences on temperature in soft magnetic materials exposed to non-sinusoidal flux waveforms and DC bias condition.

Scaling theory allows the power loss density to be derived in the form of a general homogeneous function, which depends on the peak-to-peak of the magnetic inductance ΔB, frequency f, DC bias HDC and temperature T. The form of this function has been generated through the Maclaurin expansion with respect to scaled frequency, which suit very much for the Bertotti decomposition. The parameters of the model consist of expansion coefficients, scaling exponents, parameters of DC bias mapping, parameters of temperature factor and tuning exponents. Values of these model parameters were estimated on the basis of measured data of total power density losses.

The main finding of the paper is a unified methodology for the derivation of a mathematical model which satisfactorily describes the total power density losses versus ΔB, f, H_DC, and T in soft magnetic devices.

Still the derived method does not describe dependences of the power density loss on shape and size of considered sample.

The most important achievement is of the practical use. The paper is useful for device designers.

This paper presents the algorithm which enables us to calculate core losses while the temperature is changing. Moreover, this method is effective regardless of soft magnetic material type and the flux waveforms as well as the DC bias condition. The application of scaling theory in the description of energy losses in soft magnetic materials justifies that soft magnetic materials are scaling invariant systems.

LONG before man learnt to make fire by the friction of wood, he experienced the burden of friction in dragging home his kill. Perhaps it is not too fanciful to suppose that the torn sides of his beast gave the first solid lubricant. Blood and mutton fat were seriously recommended as lubricants for church bell trunnions as recently as the 17th century. Indoed we still reckon fatty acids the best of all boundary lubricants. The range of man's activities has increased enormously in the present century, and particularly in the last few decades. Men have circled the earth in space; a space ship is on its way to examine another planet; terrestrial man is boring to the bottom of the earth's crust; others have descended to the depths of the ocean, and oven established a home on the floor of the Mediterranean, Speeds have increased by factors of thousands, temperatures range from near absolute zero to thousands of degrees; and a new environment of high‐intensity nuclear radiation has been created. Still, objects must move over and along each other in these exotic conditions; and to a large extent solid lubricants can provide the answer to the frictional problems.

The purpose of this paper is to examine the macroscopic and microscopic fields of fiber suspensions in the non‐isothermal situations, also to examine the effect of fiber on this non‐isothermal system.

Control equations are coupled and simultaneously solved by collocated finite volume method on fully triangular meshes.

Temperature dependence and wall temperature have significant effect on both macroscopic and microscopic fields of fiber suspensions. Moreover, the influence of fiber on the non‐isothermal system is similar to that of the isothermal system.

This is the first time that the microstructures of both molecules and fibers are presented in the non‐isothermal condition and it is hoped that the results will provide more insight into the microscopics of complex flows.

This paper presents a new discretization technique of the hydrodynamic energy balance model based on a finite‐element formulation. The concept of heat source lumping is introduced, and the thermal conductivity model includes the effect of varying both carrier concentrations and temperatures. The energy balance equation is formulated to account for kinetic energy as a convective flow. The new discretization method has the advantage that it allows for assembling the functions out of elementary variables available over elements instead of along element links. Therefore, theoretically, calculation of the Jacobian should be three times faster than by the classic method. Results are given for three examples. The method suffers from mathematical instabilities, but provides a good basis for future work to solve these problems.