Influence Of Temperature Effects Research Articles

Molecular dynamics analysis of the effect of temperature on the internal structure transformation of polycrystalline 3 C-SiC nanoindentation

To investigate the structure changes of polycrystalline 3 C-SiC nanoindentation process and the influence of temperature effect on its changes, the nanoindentation experiments of polycrystalline 3 C-SiC are constructed by molecular dynamics method. The initial nanoindentation model of polycrystalline 3 C-SiC and diamond indenter is constructed based on the characteristics of Voronoi method in constructing close-packed spatial lattice. The temperature conditions of 300 K, 500 K, 800 K and 1000 K are selected to analyze the dislocation structure, number and length, internal atomic structure, grain boundary structure and deformation degree of polycrystalline 3 C-SiC during nano-indentation process. The stress and deformation of diamond indenter are analyzed. The results show that the higher the temperature, the higher the degree of dislocation stacking. Temperature has an effect on the internal variation of polycrystalline silicon carbide, particularly on the transverse size of the structure. The central force of the diamond becomes weaker and the force on either side becomes stronger. The temperature effect can change the stacking degree of dislocations, reduce the internal structure transformation rate of polycrystalline 3 C-SiC, and transform fewer discrete atoms and increase the number of cubic lattice atoms.

Analytical and experimental analysis of guided waves in an aluminum plate under bending load

Although guided waves offer great potential for monitoring various structures, interpreting signals from piezoelectric sensors remains a challenging task. One main reason is the significant influence of environmental conditions on the wave propagation. A lot of research has already been done on the influence of temperature effects and recently more attention has been shifted towards loads. While previous publications have mainly focused on uni- or bi-directional loads, this publication expands the developed models to include bending loads.After reviewing the analytical basis of acoustoelasticity, the derived equations are expanded to nonhomogeneous elastic bending loads using the partial wave method. The analysis is completed using recent results developed by C. Hakoda and C. J. Lissenden (2018) [1], that gave more physical insight in the propagation of guided waves in various frequency-bands.The focus of the experimental analysis is around the fundamental S0- and A0-Modes of Lamb waves. To validate the analytical results an aluminum plate is instrumented using piezoelectric transducers and loaded with varying bending loads. The experimental results are in good agreement with the analytical theory and demonstrate the influence of bending prestress on guided wave propagation. Based on these results an innovative measurement method for bending loads is developed, that is robust to small temperature changes.

Low and high temperature effects on friction and wear performance of Cr-plated cylinder liner

Cr-plated cylinder liners with good wear and corrosion resistance as well as high strength are suitable for application in low-carbon fuel engines. A reciprocating friction and wear tester was used to measure the friction and wear performance of the Mo-sprayed piston ring and Cr-plated cylinder liner at low and high temperatures. For the low temperature conditions from −20 °C to 20 °C, the worn surface of tribo-pair was more prone to spalling. Once the load went up to 66 MPa under low temperatures, cylinder liner scuffing occurred. As the temperature increased from 90 °C to 240 °C, the honing textures of the Cr-plated cylinder liner presented gradually shallow with more abrasive marks along the sliding direction. The tribo-chemical reaction products of zinc dialkyldithiophosphates (ZDDP) with white bright spots distribution provided better protection of the tribo-pair to avoid severe fatigue spalling. The influence of temperature effects on the ZDDP decomposition and surface spalling damage should not be underestimated for Cr-plated cylinder liners.

Numerical simulation of hydraulic fracture propagation after thermal shock in shale reservoir

The scale of propagation of hydraulic fractures in deep shale is closely related to the effect of stimulation. In general, the most common means of revealing hydraulic fracture propagation rules are laboratory hydraulic fracture physical simulation experiments and numerical simulation. However, the former is difficult to meet the real shale reservoir environment, and the latter research focuses mostly on fracturing technology and the interaction mechanism between hydraulic fractures and natural fractures, both of which do not consider the influence of temperature effect on hydraulic fracture propagation. In this paper, the hydraulic fracturing process is divided into two stages (thermal shock and hydraulic fracture propagation). Based on the cohesive zone method, a coupled simulation method for sequential fracturing of deep shale is proposed. The effects of different temperatures, thermal shock rates, and times on the scale of thermal fractures are analyzed. As well as the effects of horizontal stress difference and pumping displacement on the propagation rule of hydraulic fractures. The results show that the temperature difference and the thermal shock times determine the size and density of thermal fractures in the surrounding rock of the borehole, and the number of thermal fractures increases by 96.5% with the increase of temperature difference. Thermal fractures dominate the initiation direction and propagation path of hydraulic fractures. The main hydraulic fracture width can be increased by 150% and the length can be increased by 46.3% by increasing the displacement; the secondary fracture length can be increased by 148.7% by increasing the thermal shock times. This study can provide some inspiration for the development of deep shale by improving the complexity of hydraulic fractures.

Study on high temperature dynamic characteristics and mesoscopic simulation of HFRC under dynamic and static combined loading

The Φ50mm SHPB system was used to carry out three-dimensional dynamic and static combined loading tests on hybrid fiber reinforced concrete (HFRC) treated at different temperatures (25 °C, 200 °C, 400 °C) under different confining pressure ratios (0, 0.1, 0.2, 0.3). The temperature effect, confining pressure effect and failure characteristics of HFRC under impact load were studied. The effect of fiber was equivalently treated in mortar, and the meso-aggregate model of HFRC considering aggregate, mortar and interfacial transition zone (ITZ) was established. The simulation results were compared with the experimental results. The results showed that the higher the confining pressure ratio, the more significant the temperature effect of peak stress is. The higher the temperature is, the less obvious the enhancement effect of confining pressure on peak stress is. Compared with the influence of confining pressure on dynamic peak strain, the influence of temperature effect on dynamic peak strain is higher. The established three-dimensional meso-aggregate model and calculation method can accurately reflect the dynamic response characteristics of HFRC at different temperatures and confining pressure ratios. Prestress will affect the internal stress distribution of the specimen, thus affecting the compression failure characteristics of the specimen. The confining pressure can constrain the damage course of the specimen and has a good protective effect on the specimen.

СОВЕРШЕНСТВОВАНИЕ РАСЧЕТА ПРОСТРАНСТВЕННЫХ СТЕРЖНЕВЫХ КОНСТРУКЦИЙ ИЗ ПОЛИМЕРНЫХ МАТЕРИАЛОВ С УЧЕТОМ ТЕМПЕРАТУРНОГО ВОЗДЕЙСТВИЯ.

The influence of temperature effects on the technical condition of cross-bar spatial structures (CSRS) made of polymer building materials (PSM) is considered using the example of tubular elements made of polyvinyl chloride (PVC). From numerous scientific studies by various authors, it is known that low and high temperatures significantly affect the mechanical safety of engineering plastics: tensile-compressive strength, bending, loss of stability, torsion, which ultimately reduces the operational reliability and durability of CSRS. The current regulatory and technical construction documentation on loads and impacts provides only climatic temperature impacts. In the documentation for building structures, technological temperature effects do not take into account the time factor. The general solution to the problem of unsteady heat transfer of a cylindrical element is considered in a nonlinear formulation to calculate the two-dimensional temperature field separately for the rod cylindrical element and the node connection in the “cylinder-cylinder” system. Graphic illustrations of the calculations are provided.

Influence of Temperature Effects on CPT in Granular Soils by Discrete Element Modeling in 3D

This study employs a 3D discrete element method (DEM) to simulate cone penetration tests (CPTs) in granular soils, taking into account the effect of temperature. A coupled thermal mechanical model is developed to allow for heat transfer and storage in the granular materials. The CPT simulations are conducted on granular samples prepared at various temperatures, with the specific heat and velocity of thermal conductivity being identified as two critical factors that influence sample heating time. Additionally, the thermal expansion coefficient is a crucial parameter that is closely related to the porosity of the sample. As the sample temperature increases, the particles expand, resulting in an increase in cone resistance.

The effect of temperature on frequency and instability variations in a smooth-bore magnetron

In this paper, the frequency and instability variations under the influence of temperature effect in a cylindrical smooth-bore magnetron are investigated. To derive the eigenvalue equation, the Fourier transform of electrostatic flute perturbations together with the local approximation method along radial direction for perturbed density is applied to equations of the macroscopic fluid model and Poisson equation. The obtained eigenvalue equation is solved numerically by shooting to a fitting point method. The analysis of numerical results shows the change in frequency of second three azimuthal modes for the case when the perpendicular temperature is higher than the parallel temperature (T∥<T⊥), which is greater than the case when temperatures along azimuthal and radial directions are equal (T∥=T⊥) or T∥>T⊥. As the temperature rising, the frequency and growth rate instability increase except for Tr > Tθ that the growth rate instability is reduced until Tθ = 100 00k and then is increased. The minimum frequency variation is 0.002 GHz for the mode of l=1 at 2T∥=T⊥. The maximum change in frequency, in contrast, is 10.651 GHz for the mode of l=5 at 4T∥=T⊥. According to the obtained results, the temperature controlling could be help to frequency adjustment in magnetrons.

Temperature Dependence on State Energies and Transition Frequency of Polaron in a Quantum Well with Asymmetric Gaussian Potential: Strong Coupling Method

In the present work, the influence of temperature effect on polaron in a quantum well (QW) with asymmetric Gaussian potential (AGP). By employing strongly coupling method of Pekar variational (SCMPV), the ground state (GS), the first-excited state (FES) energies and transition frequency (TF) of the polaron are derived. The state-energies and the TF as relationship of the temperature T and the electron phonon coupling strength (EPCS) are obtained by using quantum statistics theory (QST). We have found that the state-energies and the TF increase when the temperature is increasing. The states-energies and the TF are decreased with raising the EPCS.

Influence of Temperature Effect on the Static and Dynamic Performance of Gas-Lubricated Microbearings.

Gas-lubricated microbearings are widely applied in multiple fields due to their advantages of high-speed, low friction level and other features. The operating environment of microbearings is complex, and the difference of temperature has an important influence on their comprehensive performance. In this investigation, FEM (finite element method) is employed to investigate the static, dynamic and limit characteristics of microbearings lubricated by different kinds of gas at different temperatures. The results show that the rise of temperature leads to the decline of equivalent viscosity of gas, which weakens the load capacity of microbearings, and furthermore, affects the operating stability of microbearings. The dynamic performances of microbearings at different temperatures are very different, and the two dynamic limit characteristics are more sensitive to temperature when it changes.

The Influence of Temperature Impact on the Strength of Adhesion of Polyurethane Glue-foam with Masonry Products

The use of masonry on glued polyurethane foam joints can significantly increase labor productivity in the construction of stone buildings. One of the factors restraining the introduction of polyurethane foam adhesive into the practice of construction of stone buildings is insufficient knowledge of the influence of temperature effects on the adhesion of adhesive-foam to masonry products. In order to obtain data on the adhesion strength of polyurethane joints with masonry products under temperature influences, 28 prototypes of masonry were tested, aged in laboratory conditions and also subjected to heating to 100ºC and 200ºC. Tests of masonry samples were carried out in accordance with STB EN 1052-5. Based on the experimental studies carried out and new data on the influence of temperature effects on the adhesion strength of polyurethane joints with masonry products were obtained.

Temperature Effects on Polymer Structures of Canopies for Inversion Roofs of Multi-Storey Residential Buildings

The influence of temperature effects on the technical condition of cross-rod spatial structures of canopies for inversion roofs of multi-storey residential buildings made of polymer materials is considered on the example of tubular elements made of polyvinyl chloride (PVC). For modern multi-storey residential buildings, the current regulatory and technical documentation provides for operational (inversion) roofs, which can accommodate children’s sports grounds, cafes, bars, restaurants, parking lots, tanning salons, as well as gardens and architectural and landscape objects, helicopter platforms, etc. To protect visitors against atmospheric influences, canopies made of spatial core building structures (SCBS), which are operated in the open air, taking into account various climatic influences: high and low temperatures, corresponding humidity, precipitation, etc., are recommended. The elements of the core system are of the greatest interest for taking into account the temperature impact on the technical condition of the developed structure. The general solution of the problem of non-stationary heat transfer of a structure for calculating a two-dimensional temperature field is considered in a nonlinear formulation. The problem of thermal conductivity is considered under the assumption that there is a technical possibility for supplying a coolant inside the cylinder. As a result, there is a heat flow, with which it is possible to adjust the temperature between the outer and inner areas of the cylindrical elements for more efficient installation of the stress-strain state of the entire supporting structure as a whole.

Numerical Simulation and Analysis of Thermal Stress on Restressed Assembly Steel Struts System in Foundation Excavation

When using horizontal internal bracing system in large span deep foundation pit, the influence of temperature effect on bracing system must be considered. Based on the long-term thermal stress monitoring of a project in the west of Hangzhou, this paper studied the influence of Angle brace temperature effect on the foundation pit enclosure structure after excavation to the bottom by using three-dimensional finite element model. When the strut temperature rises, the strut axial force increases. The longer the length is, the higher the axial force rises. The horizontal displacement of the surrounding wall and soil will be in the external direction of the pit, which is conducive to the stability of the surrounding system. The second layer struts are more affected by the temperature effect than the first layer struts, and the combined action of the two struts makes the surrounding wall produce greater displacement. The pouring of the bottom plate makes the strut subject to the temperature effect to generate greater axial force, the second layer struts change more violently, and at the same time reduces the displacement and deformation of the retaining structure. When the temperature drops, the strut axial force decreases and the horizontal displacement of the retaining structure to the pit increases, which is not conducive to the stability of the system. At this time, the reinforcement of the nearby soil body can be considered to reduce the deformation of the soil body and the retaining wall.

Elimination of the effect of temperature on the dynamic parameters of bridge beams

An article presents an overview on influence of environmental factors on the dynamic response of bridge beams. Examples of the determination of the technical condition by taking into account the influence of the environment on real bridges are given. The process of damage identification based on operational modal analysis with filtering effects is presented. Author considered an influence of temperature effect of the environment on eigenfrequencies of beam bridges. A numerical experiment was performed using a large road collapsible bridge as an example: bridge temperature was determined with additional heating of the girder from solar radiation and without it; the values of dynamic parameters of the girder from the change in temperature during the calendar year were calculated; the dependence of eigenfrequency of the girder on changes in temperature of the bridge is constructed. Further, an analysis of a time series formed from the eigenfrequency changes of the girder was made. Two different methods were used to describe the time series: a model based on a statistical pattern in the given data and a model of a recurrent neural network. Before applying the statistical autoregressive integrated moving average model, the time series was decomposed into additive components: trend, seasonal component, residuals and noise. After that, construction of a mathematical model describing the stationary residuals of the time series was performed. Second method – based on recurrent neural networks, can be rephrased as a question of constructing a regression model. on the basis of the training and test data sets, a network was formed containing a visible layer with 1 input signal, a hidden layer with 4 blocks and an output level that makes one prediction value.

Влияние температурных эффектов, связанных с реакцией диссоциации/рекомбинации молекул воды и джоулевым нагревом раствора на стационарный перенос ионов соли в диффузионном слое

Влияние температурных эффектов, связанных с реакцией диссоциации/рекомбинации молекул воды и джоулевым нагревом раствора на стационарный перенос ионов соли в диффузионном слое

Molecular dynamics simulation on influence of temperature effect on electro-coalescence behavior of nano-droplets

ABSTRACTIn electric dehydration of crude oil, the dewatering efficiency can be improved by raising emulsion temperature properly which reduces the viscosity of crude oil. However, it should be noticed that the emulsion temperature does not only affect the emulsion viscosity but also nano-droplets dynamics behavior which impacts the coalescence efficiency either. Therefore the influence of temperature effect on the electro-coalescence of nano-droplets is studied by a molecular dynamics method. The results show that the temperature presents an active or negative effect, depending on the competitive relation between electrostatic interaction and thermal motion. Two stages are distinguished according to the dominant mechanism. During stage I, governed by the electrostatic interaction, lower temperature promotes the polarization and leads to an acceleration of the droplets coalescence, but higher temperature restrains the coalescence process due to molecules thermal motion breaking the polarization process. During stage II, governed by the thermal motion, lower temperature improves the coalescence because of a diffusion effect, but higher temperature deteriorates electro-coalescence because of a violent molecular thermal motion. Additionally, hydrogen bond and radial distribution functions are obtained by statistics to describe droplets micromorphology, which explains the reason why the droplet forms longer chain structure at the critical electric field.

Analysis and measurement of temperature effect on electromagnetic susceptibility of embedded ADC

Analog to Digital Converter (ADC) is widely used in measurement and control systems, the electromagnetic susceptibility problem of embedded ADC has been gradually highlighted in complex environment. The ambient temperature effect on electromagnetic susceptibility is analyzed by theoretical analysis and experimental measurement. Combined with the structure and characteristic of ADC, the mechanism of radio frequency interference signal disturbing ADC is analyzed. The influence of temperature effect on drain current of metal-oxide-semiconductor(MOS) transistors under interference signal is pointed out. At different temperatures, the circuit parameters of each part are measured and analyzed under electromagnetic interference. The temperature effect on ADC electromagnetic susceptibility is measured within the frequency range from 10 MHz to 1 GHz and the temperature range from -10 ℃ to 80 ℃. Results show that the changing ambient temperature changes the response of ADC under electromagnetic interference by altering the mobility of MOS transistors, causing significant drift of electromagnetic susceptibility.

Experimental study of cooling speed for ultra-thick steel plate during the jet impinging and quenching process

The quenching temperature drop curve for Q345B steel plate with 84 mm and 170 mm thickness was tested to analyze the distributing regularities and influencing factors of cooling speed for ultra-thick steel plate during the jet impinging and quenching process. The influences for temperature drop, temperature gradient and cooling speed were analyzed under the conditions of 60~100 m3/h water amount, 0.4~1.0 MPa water pressure, transient switching of quenching mode and the distribution of heat exchanger. Threedimensional heat anti transfer model, surface heat transfer coefficient model and thermal physical parameter model were built up by finite element and optimization. The results showed that the deviation of calculated and measured values was less than 4% for temperature drop curve model. The cooling speed of vertical section for 84 mm-thick steel plate was approximately proportional to surface heat transfer coefficient. The influence of surface heat transfer to cooling speed became weak when the thickness was increased. The influences of temperature effect when switching different quenching modes and temperature gradient of vertical section to cooling speed were stronger. The minimum value of cooling speed was about 1.0~1.8°C/s, between H/6 and H/3 region. These data provide the key information for increasing the cooling speed and uniformity.

Temperature effects in the analysis of electromechanical impedance by using spectral element method

Purpose – The purpose of this paper is to develop a spectral element modeling to predict electromechanical admittance in the surface-bonded piezoelectric wafer and beam structure considering temperature effects. Design/methodology/approach – For modeling the beam, the axial and transverse vibrations of the beam have been considered, and temperature-dependent mechanical and electromechanical properties of piezoelectric wafer active sensor and aluminum have been analyzed. The influences of temperature effects on electromechanical admittance are investigated. Findings – The results show that a frequency left shift and a decrease in amplitude of admittance in any natural frequencies with increasing temperature have been observed. The mechanism of these changes is discussed. Originality/value – The numerical results may be considered helpful for structural health monitoring using electromechanical impedance technique.

LASER-INDUCED THERMAL–MECHANICAL DAMAGE CHARACTERISTICS OF CLEARTRAN MULTISPECTRAL ZINC SULFIDE WITH TEMPERATURE-DEPENDENT PROPERTIES

Laser-induced thermal–mechanical damage characteristics of window materials are the focus problems in laser weapon and anti-radiation reinforcement technology. Thermal–mechanical effects and damage characteristics are investigated for cleartran multispectral zinc sulfide ( ZnS ) thin film window materials irradiated by continuous laser using three-dimensional (3D) thermal–mechanical model. Some temperature-dependent parameters are introduced into the model. The temporal-spatial distributions of temperature and thermal stress are exhibited. The damage mechanism is analyzed. The influences of temperature effect of material parameters and laser intensity on the development of thermal stress and the damage characteristics are examined. The results show, the von Mises equivalent stress along the thickness direction is fluctuant, which originates from the transformation of principal stresses from compressive stress to tensile stress with the increase of depth from irradiated surface. The damage originates from the thermal stress but not the melting. The thermal stress is increased and the damage is accelerated by introducing the temperature effect of parameters or the increasing laser intensity.