scholarly journals Analytical models of austenite transformation in steel with allowance for internal stresses

2018 ◽  
pp. 371-383
Author(s):  
S.V. Bobyr
Keyword(s):  
Experimental Data ◽  
Heat Treatment ◽  
Experimental Study ◽  
Hot Deformation ◽  
Structural Transformations ◽  
Analytical Models ◽  
Theoretical Expression ◽  
Internal Stresses ◽  
Kinetics Of ◽  
Comprehensive Study

The aim of the work is to review the analytical models of austenite decay, taking into account the internal stresses obtained by various authors. It is shown that a common drawback of the known works is the neglect of the effect of the stress-strain state arising during the heat treatment of parts on the kinetics of structural transformations, while the available experimental data indicate a significant effect of stresses and strains on structural transformations. It has been established that the experimental data accumulated to date do not allow reliably describing the effect of the stress state on structural transitions during the heat treatment of steels for the hot deformation tool. A simple theoretical expression is proposed for calculating the amount of martensite formed as a function of the voltage in the γ phase. It is theoretically shown that taking into account the voltage acting in the γ phase leads to an increase in the temperature of the end of the formation of martensite. Experimental study of this effect is especially convenient to carry out in isothermal conditions under uniaxial tension. It is shown that in order to reliably predict the structural state of the hot deformation tool during heat treatment, it is necessary to conduct a comprehensive study related to the experimental study of the effect of stresses on all types of transformations and the creation of an adequate mathematical model of austenite decomposition based on the obtained experimental data.

Kinetics of hypso anhydrites dissolution in water. Experimental studies

2019 ◽  
pp. 93-96
Author(s):  
A. L. Lebedev ◽  
I. V. Avilina
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Riccati Equation ◽  
Balance Equation ◽  
Experimental Studies ◽  
Common Ion ◽  
The Common ◽  
Common Ion Effect ◽  
Kinetics Of Dissolution ◽  
Kinetics Of

Experimental study of kinetics of dissolution of hypso anhydrites at 25 ᵒC made it possible to formulate model of the process in the form of a balance equation for the kinetics of dissolution of gypsum, anhydrite (first and second orders, respectively) and kinetics of precipitation of gypsum (second order). The processing of the experimental data were carried out on the basis of the solution of the Riccati equation. When taking into account the common-ion effect on the solubility of gypsum and anhydrite, the calculated values turned out to be more comparable with the experimental ones.

An expression for droplet evaporation incorporating thermal effects

2011 ◽  
Vol 667 ◽  
pp. 260-271 ◽  
Author(s):  
K. SEFIANE ◽  
R. BENNACER
Keyword(s):  
Experimental Data ◽  
Thermal Effects ◽  
Droplet Evaporation ◽  
Theoretical Expression ◽  
Dimensionless Number ◽  
Wide Range ◽  
Isothermal Diffusion ◽  
Rate Of Evaporation ◽  
First Time ◽  
Kinetics Of

We propose a general theoretical expression for sessile droplets' evaporation, incorporating thermal effects related to the thermal resistance of the substrate and liquid properties. We develop an expression which accounts for thermal effects associated with evaporative cooling; the latter leads to a reduction in the rate of evaporation, which is not accounted for in the current theories, i.e. ‘isothermal diffusion theories’. The threshold for transition to a regime in which thermal effects start to be significant is identified through a dimensionless number which includes substrate and liquid properties as well as the kinetics of evaporation. The proposed theory is validated against experimental data in a very wide range of conditions and for a variety of systems. The developed expression extends the domain of use of diffusion-based models for droplet evaporation and accurately describes some aspects of the phenomenon which, to the best of our knowledge, are highlighted for the first time.

scholarly journals The Influence of Woven Fabric Structure on Kinetics of Water Sorption

2014 ◽  
Vol 9 (1) ◽  
pp. 155892501400900
Author(s):  
Mohamed Hamdaoui ◽  
Nesma Sawssen Achour ◽  
Sassi Ben Nasrallah
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Water Sorption ◽  
Cotton Fabrics ◽  
Woven Fabric ◽  
Model Parameters ◽  
Kinetic Rate ◽  
Weave Structure ◽  
Fabric Structure ◽  
Kinetics Of

In this paper, the results of an experimental study designed to determine the kinetics of water sorption on cotton fabrics are presented. The dynamic water sorption of cotton fabrics was gravimetrically investigated at 20°C by using an experimental device, which assured the vertical suspension of the cloth surface and permitted the measurement of the mass of liquid rising in the fabric. A good fit of the experimental data with the parallel exponential kinetics model was found. The results show that the weave structure and the number of yarns per centimeter had a significant influence on the model parameters and the kinetic rate of sorption.

scholarly journals Influence of Flow Speed on the Compression Surfaces of Inlet on Efficiency of the Boundary Layer Bleed

2019 ◽  
Vol 14 (3) ◽  
pp. 15-25
Author(s):  
M. A. Goldfeld
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
Experimental Study ◽  
Flow Velocity ◽  
Hypersonic Flow ◽  
Flow Speed ◽  
Analytical Models ◽  
Flow Conditions ◽  
Air Mass ◽  
Mach Numbers

The paper presents the results of analytical and experimental study of the bleed coefficient at high flight Mach numbers from 3 to 7. For the calculation, an analytical model was used model with a fixed exit in the supercritical bleed mode, which allows varying the bleed air mass depending on flow conditions and parameter bleed system. The measurement of the bleed flow coefficients were performed for three bleed configurations in a wind tunnel at local Mach numbers in front of the bleed area from 2.5 to 5.96. The model had a long forebody, so that before the bleed area there was a thick boundary layer. As a result, new experimental data on bleed coefficient and its general dependence on the Mach numbers up to 6 and the bleed angles of 90 and 45° were obtained. It is revealed that at increase in the local Mach number, the tendency is observed towards a decrease in the bleed coefficient, and this tendency intensifies with decrease in the bleed channel inclination. These data were used to evaluate known analytical models to determine the characteristics of bleed systems at hypersonic flow velocity analytical models to determine the characteristics of bleed systems at hypersonic flow velocity.

A fuzzy neural network approach for modeling the growth kinetics of FeB and Fe2B layers during the boronizing process

2018 ◽  
Vol 106 (6) ◽  
pp. 603 ◽  
Author(s):  
Bendaoud Mebarek ◽  
Mourad Keddam
Keyword(s):  
Neural Network ◽  
Experimental Data ◽  
Fuzzy Neural Network ◽  
Treatment Time ◽  
Calculation Model ◽  
Average Error ◽  
Network Approach ◽  
Neural Network Approach ◽  
Fuzzy Neural ◽  
Kinetics Of

In this paper, we develop a boronizing process simulation model based on fuzzy neural network (FNN) approach for estimating the thickness of the FeB and Fe2B layers. The model represents a synthesis of two artificial intelligence techniques; the fuzzy logic and the neural network. Characteristics of the fuzzy neural network approach for the modelling of boronizing process are presented in this study. In order to validate the results of our calculation model, we have used the learning base of experimental data of the powder-pack boronizing of Fe-15Cr alloy in the temperature range from 800 to 1050 °C and for a treatment time ranging from 0.5 to 12 h. The obtained results show that it is possible to estimate the influence of different process parameters. Comparing the results obtained by the artificial neural network to experimental data, the average error generated from the fuzzy neural network was 3% for the FeB layer and 3.5% for the Fe2B layer. The results obtained from the fuzzy neural network approach are in agreement with the experimental data. Finally, the utilization of fuzzy neural network approach is well adapted for the boronizing kinetics of Fe-15Cr alloy.

EXPERIMENTAL STUDY OF THE KINEMATIC PARAMETERS OF MOVEMENT OF CARS FORCED IDLE MOTION

2018 ◽  
pp. 52-57
Author(s):  
Ivelin Kostov
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Experimental Research ◽  
Kinematic Parameters ◽  
Research Results ◽  
Software Product

In the work brought some experimental data of kinematic parameters of movement of cars forced idle, as the software product was used to diagnose 900 ATS, which recorded kinematic parameters of vehicle. On the basis of the conducted experimental research results are shown tabulated and analysed.

Features of the kinetics of cyclic elastoplastic deformation diagrams at dwells in cycles and superimposition of variable stresses on them

2020 ◽  
Vol 86 (12) ◽  
pp. 46-53
Author(s):  
M. M. Gadenin
Keyword(s):  
Experimental Data ◽  
Elastoplastic Deformation ◽  
Low Cycle Fatigue ◽  
Cycle Fatigue ◽  
Loading Cycle ◽  
Additional Variable ◽  
Dynamic Creep ◽  
Variable Stresses ◽  
Kinetics Of ◽  
Deformation Diagrams

The goal of the study is determination of the regularities of changes in cyclic strains and related deformation diagrams attributed to the existence of time dwells in the loading modes and imposition of additional variable stresses on them. Analysis of the obtained experimental data on the kinetics of cyclic elastoplastic deformation diagrams and their parameters revealed that in contrast to regular cyclic loading (equal in stresses), additional deformations of static and dynamic creep are developed. The results of the studys are especially relevant for assessing the cyclic strength of unique extremely loaded objects of technology, including nuclear power equipment, units of aviation and space systems, etc. The experiments were carried out on the samples of austenitic stainless steel under low-cycle loading and high temperatures of testing. Static and dynamic creep deformations arising under those loading conditions promote an increase in the range of cyclic plastic strain in each loading cycle and also stimulate an increase in the range of elastoplastic strain due to active cyclic deformation. At the same time the existence of dwells on extrema of stresses in cycles without imposition of additional variable stresses on them most strongly affects the growth of plastic strain ranges in cycles. Imposition of additional variable stresses on dwells also results in the development of creep strains, but their growth turns out to be somewhat less than in the presence of dwells without stresses imposed. The diagrams of cyclic deformation obtained in the experiments are approximated by power dependences, their kinetics being described in terms of the number of loading cycles using corresponding temperature-time functions. At the same time, it is shown that increase in the cyclic plastic deformation for cycles with dwells and imposition of additional variable stresses on them decreases low cycle fatigue life compared to regular loading without dwells at the same stress amplitudes, moreover, the higher the values of static and dynamic creep, the greater decrease in low-cycle fatigue life. This conclusion results from experimental data and analysis of conditions of damage accumulation for the considered forms of the loading cycle using the deformation criterion of reaching the limit state leading to fracture.

Effect of ionizing radiation on the kinetics of hydrogenation on the Ni-MgO mixed catalyst

1982 ◽  
Vol 47 (7) ◽  
pp. 1780-1786 ◽  
Author(s):  
Rostislav Kudláček ◽  
Jan Lokoč
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Liquid Phase ◽  
Ionizing Radiation ◽  
Oxide Catalyst ◽  
Absorbed Dose ◽  
Hydrogenation Rate ◽  
Solution Composition ◽  
Mixed Catalyst ◽  
Kinetics Of

The effect of gamma pre-irradiation of the mixed nickel-magnesium oxide catalyst on the kinetics of hydrogenation of maleic acid in the liquid phase has been studied. The changes of the hydrogenation rate are compared with the changes of the adsorbed amount of the acid and with the changes of the solution composition, activation energy, and absorbed dose of the ionizing radiation. From this comparison and from the interpretation of the experimental data it can be deduced that two types of centers can be distinguished on the surface of the catalyst under study, namely the sorption centres for the acid and hydrogen and the reaction centres.

Kinetics of the Crystallization of Potassium Sulfate

1993 ◽  
Vol 58 (8) ◽  
pp. 1848-1854 ◽  
Author(s):  
Miroslav Karel ◽  
Jaroslav Nývlt
Keyword(s):  
Experimental Data ◽  
Crystal Growth ◽  
Growth Rates ◽  
Potassium Sulfate ◽  
Kinetics Of

The kinetics of the crystallization of potassium sulfate has been determined using the MSMPR technique. Values of the nucleation and crystal growth rates evaluated from the experimental data are compared with the corresponding literature data.

Diffusion model for deposition of epitaxial GaAs layers prepared by the MOCVD method

1991 ◽  
Vol 56 (10) ◽  
pp. 2020-2029
Author(s):  
Jindřich Leitner ◽  
Petr Voňka ◽  
Josef Stejskal ◽  
Přemysl Klíma ◽  
Rudolf Hladina
Keyword(s):  
Experimental Data ◽  
Growth Rate ◽  
Kinetic Model ◽  
Gas Phase ◽  
Substrate Surface ◽  
Deposition Process ◽  
Hydrogen Atmosphere ◽  
Epitaxial Gaas ◽  
Kinetics Of ◽  
Good Agreement

The authors proposed and treated quantitatively a kinetic model for deposition of epitaxial GaAs layers prepared by reaction of trimethylgallium with arsine in hydrogen atmosphere. The transport of gallium to the surface of the substrate is considered as the controlling process. The influence of the rate of chemical reactions in the gas phase and on the substrate surface on the kinetics of the deposition process is neglected. The calculated dependence of the growth rate of the layers on the conditions of the deposition is in a good agreement with experimental data in the temperature range from 600 to 800°C.

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