scholarly journals Study of phase transformations in complex phase steel using a mesoscale cellular automaton model Part II: Experiments and Validation

2020 ◽  
Vol 72 (3) ◽  
pp. 32-44
Author(s):  
Jaroslaw Opara ◽  
Roman Kuziak
Keyword(s):  
Phase Transformations ◽  
Mesoscale Model ◽  
Goal Function ◽  
Study Phase ◽  
Complex Phase ◽  
Microhardness Distribution ◽  
Validation Parameters ◽  
Wide Range ◽  
Microstructure Morphology ◽  
Predicted Values

A two-dimensional mesoscale model based on the concept of hybrid cellular automata was used to study phase transformations in a complex phase steel during continuous cooling. This model enables simulation of the decomposition of austenite into ferrite, bainite, and martensite, accompanied by calculations of volume and grain boundary diffusion of carbon. In effect, as a result, one can observe the morphology of simulated microstructures, corresponding carbon segregation as well as microhardness distribution. These results with the kinetics of austenite to ferrite phase transformation and predicted values of the complex phase steel hardness are the subject of model validation. A series of dilatometric experiments were carried out with constant cooling rates in order to construct a CCT diagram and validate the presented model. The convergence of simulated results with empirical outcomes was confirmed quantitatively using a dedicated goal function and data summaries in the table and graphs. However, some qualitative and quantitative discrepancies in terms of microstructure morphology are indicated which was possible thanks to applying a wide range of different validation parameters of the model. It is emphasized how crucial is the use of appropriate validation methodology.

scholarly journals Study of phase transformations in complex phase steel using a mesoscale cellular automaton model Part I: Modeling Fundamentals

2020 ◽  
Vol 72 (3) ◽  
pp. 17-31
Author(s):  
Jarosław Opara ◽  
Roman Kuziak
Keyword(s):  
Phase Transformations ◽  
Mesoscale Model ◽  
Concentration Field ◽  
Carbon Diffusion ◽  
Study Phase ◽  
Homogeneous Microstructure ◽  
Complex Phase ◽  
Hybrid Cellular Automata ◽  
Microhardness Distribution ◽  
Digital Material

A two-dimensional mesoscale model based on the concept of hybrid cellular automata is developed to study phase transformations in a complex phase steel during continuous cooling. The model is capable of simulating microstructure evolution with carbon diffusion in the volume and along grain boundaries, γ/α interfaces migration into austenite, as well as formation of bainite and martensite islands during intensive cooling in lower temperatures. In contrast to the classic statistical approaches which are based on the assumption of modeling one point in the material with homogeneous microstructure, the proposed phase transformations’ model in the mesoscale accounts for material heterogeneity. The simulation results in the form of a digital material representation with microstructures and maps showing the carbon concentration field as well as microhardness distribution are presented. One of the main advantages of the model is that has only seven adjustment coefficients that are used in the fitting process.

scholarly journals Holographic Interferometer for the Study of Phase Media, Which Has Four Output Channels of Different Sensitivity

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Yusupzhan Kh. Ismanov ◽  
Nasipbek K. Dzhamankyzov
Keyword(s):  
Computer Simulation ◽  
Simulation Method ◽  
Talbot Effect ◽  
Complex Phase ◽  
Computer Simulation Method ◽  
Holographic Interferometer ◽  
Wide Range ◽  
Talbot Interferometer ◽  
Spatial Filtration

Computer simulation of the interferometer combining properties of low-sensitive Talbot interferometer and high-sensitive holographic interferometer is considered. The interferometer has four output channels having different sensitivity. Channel sensibility can be varied by means of spatial filtration. The base of the interferometer is the holographic Talbot effect. The efficiency of this interferometer was verified by computer simulation method. Some results of the computer simulation are presented in the article. These results were compared with results obtained in optical experiments under the same conditions. A wide range of sensitivity of the interferometer makes it possible to use the interferometer to study complex phase objects, primarily dynamic media.

scholarly journals Effects of Austenitization Temperature and Pre-Deformation on CCT Diagrams of 23MnNiCrMo5-3 Steel

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5116
Author(s):  
Ivo Schindler ◽  
Rostislav Kawulok ◽  
Petr Opěla ◽  
Petr Kawulok ◽  
Stanislav Rusz ◽  
...  
Keyword(s):  
Phase Transformations ◽  
Deformation Temperature ◽  
True Strain ◽  
Austenitization Temperature ◽  
Diffusion Controlled ◽  
Significant Acceleration ◽  
Wide Range ◽  
Mean Grain Size ◽  
Cct Diagrams ◽  
Kinetics Of

The combined effect of deformation temperature and strain value on the continuous cooling transformation (CCT) diagram of low-alloy steel with 0.23% C, 1.17% Mn, 0.79% Ni, 0.44% Cr, and 0.22% Mo was studied. The deformation temperature (identical to the austenitization temperature) was in the range suitable for the wire rolling mill. The applied compressive deformation corresponded to the true strain values in an unusually wide range. Based on the dilatometric tests and metallographic analyses, a total of five different CCT diagrams were constructed. Pre-deformation corresponding to the true strain of 0.35 or even 1.0 had no clear effect on the austenite decomposition kinetics at the austenitization temperature of 880 °C. During the long-lasting cooling, recrystallization and probably coarsening of the new austenitic grains occurred, which almost eliminated the influence of pre-deformation on the temperatures of the diffusion-controlled phase transformations. Decreasing the deformation temperature to 830 °C led to the significant acceleration of the austenite → ferrite and austenite → pearlite transformations due to the applied strain of 1.0 only in the region of the cooling rate between 3 and 35 °C·s−1. The kinetics of the bainitic or martensitic transformation remained practically unaffected by the pre-deformation. The acceleration of the diffusion-controlled phase transformations resulted from the formation of an austenitic microstructure with a mean grain size of about 4 µm. As the analysis of the stress–strain curves showed, the grain refinement was carried out by dynamic and metadynamic recrystallization. At low cooling rates, the effect of plastic deformation on the kinetics of phase transformations was indistinct.

Analysis of the Dynamic Response of a Controlled Detonation Chamber

2010 ◽  
Author(s):  
B. Simoens ◽  
M. H. Lefebvre ◽  
J. K. Asahina ◽  
F. Minami ◽  
R. E. Nickell
Keyword(s):  
Vibration Frequency ◽  
Explosive Charge ◽  
Cylindrical Vessel ◽  
Point Of View ◽  
Scale Model ◽  
Cylindrical Charge ◽  
Strain Gages ◽  
Spherical Charge ◽  
Wide Range ◽  
Predicted Values

Detonation chambers (either mobile or fixed) are used worldwide for a wide range of applications. At present, a 1/7 scale model of a 1 ton detonation chamber is available for extended testing in Belgium. The chamber is a single wall cylindrical vessel with semi-elliptical ends. Each time an explosive charge is fired in the vessel, that vessel is submitted to a number of deformation cycles. A series of strain gages measure the deformation of the vessel walls. Experimental peak strains and vibration frequency can be compared to predicted values based on simple formulas. Measured values are reasonably close to the estimated values. The influence of the shape of the charge is studied. The shape has an important influence on the chamber response. For a fixed charge mass, a spherical charge causes less deformation than a cylindrical charge and is therefore advantageous from a fatigue point of view.

scholarly journals High pressure studies of L-Serine-L-Ascorbic acid co-crystal

2014 ◽  
Vol 70 (a1) ◽  
pp. C988-C988
Author(s):  
Sergey Arkhipov ◽  
Boris Zakharov ◽  
Elena Boldyreva
Keyword(s):  
High Pressure ◽  
Ascorbic Acid ◽  
Hydrogen Bonds ◽  
Single Crystal ◽  
Crystal Engineering ◽  
Mixed Crystals ◽  
Study Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Wide Range

"Experiments for studying crystalline materials under extreme conditions are a powerful tool for investigating ""structure-property"" relationships. They also give information on the behavior of hydrogen bonds and are important both for materials science and crystal engineering. In addition, many processes in the living organisms are also related to mechanical stress. One of the most interesting tasks is to identify factors which influence the stability of a structure, or a part of the structure, at high pressure. Experiments on the systematic study of compounds in a wide range of pressures allow us to accumulate data that can be used to solve this problem. For a more complete picture, the mixed crystals of the selected compound are studied. Investigation of mixed crystals and cocrystals of interest can be compared with the crystals of individual compounds. We have chosen the structure of L-serine - L-ascorbic acid to be compared with those of L-serine and L-ascorbic acids for such a study. Phase transitions were previously reported to be induced by increasing pressure in both L-serine [1] and L-ascorbic acid [2]; moreover, the structure of L-serine was followed at multiple pressures by single-crystal and powder X-ray diffraction[3]. L-serine – L-ascorbic acid co-crystal was studied in the pressure range 0-5.4 GPa (at multiple points at every 0.5-0.7 GPa) by single-crystal X-ray diffraction and Raman spectroscopy. A phase transition has been detected and some rearrangement in the network of hydrogen bonds was observed. The high pressure data were compared with those for the individual structures of the L-serine and L-ascorbic acid. This work was supported by RFBR (grants 12–03-31541, 14-03-31866, 13-03-92704, 14-03-00902 ), Ministry of Science and Education of Russia and Russian Academy of Sciences."

PHASE TRANSFORMATIONS DURING HEATING OF AMORPHOUS/NANOCRYSTALLINE Ni–Ti POWDERS

2010 ◽  
Vol 24 (09) ◽  
pp. 1137-1140 ◽  
Author(s):  
M. M. VERDIAN ◽  
M. SALEHI ◽  
K. RAEISSI
Keyword(s):  
Differential Scanning Calorimetry ◽  
Solid State ◽  
Phase Transformations ◽  
Low Energy ◽  
Heating Process ◽  
Study Phase ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Niti Phase

Amorphous/nanocrystalline 50 Ni –50 Ti powders were synthesized from elemental Ti and Ni powders by solid state synthesis utilizing low energy mechanical alloying with times up to 100 h. The produced powders were investigated by X-ray diffraction and differential scanning calorimetry to study phase transformations that occurred during heating in the calorimeter. It was found that at the first stage of the heating process, a disordered NiTi phase was formed at temperature of about 400°C. Further investigations indicated that this phase transformed into the Ni 3 Ti and Ti 2 Ni intermetallic compounds after heating at a temperature of about 800°C.

Simulation of Freeway Weaving Areas

2002 ◽  
Vol 1802 (1) ◽  
pp. 115-124 ◽  
Author(s):  
Alexander Skabardonis
Keyword(s):  
Operating Conditions ◽  
Model Parameters ◽  
Sensitivity Factor ◽  
Microscopic Simulation ◽  
Lane Changing ◽  
Wide Range ◽  
Design Characteristics ◽  
Predicted Values ◽  
Demand Patterns ◽  
Parameter Values

The operation of freeway weaving sections is characterized by intense lane-changing maneuvers and complex vehicle interactions that often create bottlenecks along freeway facilities. The CORSIM microscopic simulation model was applied to simulate the operation of eight realworld weaving sites in California under a wide range of operating conditions. The results indicate that CORSIM with default parameter values underpredicts the speeds in the weaving section by about 19% on average. Numerous simulation runs were made with different values of the model parameters. The following parameters were found to significantly affect the CORSIM results: ( a) car-following sensitivity factor, ( b) lane-changing aggressiveness factor, and ( c) percentage of freeway through vehicles that yield to merging traffic. The calibrated CORSIM model reasonably replicated observed traffic operations at all test sites. The predicted average speeds were within ±5 mph for most test sites. Good agreement between measured and predicted values was obtained for all the combinations of design characteristics and demand patterns.

Improved Form of the k-ε Model for Wall Turbulent Shear Flows

1987 ◽  
Vol 109 (2) ◽  
pp. 156-160 ◽  
Author(s):  
Y. Nagano ◽  
M. Hishida
Keyword(s):  
Reynolds Number ◽  
Turbulent Flows ◽  
Plate Boundary ◽  
Wall Turbulence ◽  
Turbulent Shear ◽  
Committee Report ◽  
Low Reynolds Number Flows ◽  
Diffuser Flow ◽  
Wide Range ◽  
Predicted Values

An improved k-ε turbulence model for predicting wall turbulence is presented. The model was developed in conjunction with an accurate calculation of near-wall and low-Reynolds-number flows to meet the requirements of the Evaluation Committee report of the 1980–1981 Stanford Conference on Complex Turbulent Flows. The proposed model was tested by application to turbulent pipe and channel flows, a flat plate boundary layer, a relaminarizing flow, and a diffuser flow. In all cases, the predicted values of turbulent quantities agreed almost completely with measurements, which many previously proposed models failed to predict correctly, over a wide range of the Reynolds number.

scholarly journals Measures of spatial structure in samples of genotypes for multiallelic loci

1999 ◽  
Vol 73 (3) ◽  
pp. 251-261 ◽  
Author(s):  
B. K. EPPERSON ◽  
Z. HUANG ◽  
T.-Q. LI
Keyword(s):  
Allele Frequencies ◽  
Multiple Alleles ◽  
Sampling Schemes ◽  
Animal Populations ◽  
Wide Range ◽  
Theoretical Population ◽  
Theoretical Population Genetics ◽  
Predicted Values ◽  
Join Count Statistics ◽  
First Time

Various spatial autocorrelation statistics have been widely used both in theoretical population genetics and to study the spatial distribution of diploid genotypes in many plant and animal populations. However, previous simulation studies have considered only diallelic loci. In this paper, we use a large number of space–time simulations to characterize for the first time the parametric and statistical values of Moran's I-statistics for converted individual genotypes as well as for join- count statistics. A wide range of levels of dispersal and numbers of alleles and allele frequencies are modelled and the results reveal the different general effects of each of these factors on these statistics. We also examine the range of appropriate sampling designs and sizes for which predicted values can be interpolated for specific sampling schemes for any given population genetic field survey. Numbers of alleles and allele frequencies each affect some statistics but not others. The results indicate generally low standard deviations. The results also develop precise and efficient methods of estimating gene dispersal, based on the various autocorrelation measures of standing spatial patterns of genetic variation within populations. The results also extend these methods to loci with multiple alleles, typical of those studied through modern molecular methods.

Detection of Synthetic Drugs as Adulterants in Natural and Herbal Slimming Products by LC-ESI-MS/MS with Polarity Switching

2016 ◽  
Vol 99 (4) ◽  
pp. 929-940 ◽  
Author(s):  
Phyllis Wilson ◽  
Claude Masse
Keyword(s):  
Weight Loss ◽  
Simultaneous Detection ◽  
Gradient Elution ◽  
Ammonium Formate ◽  
Synthetic Drugs ◽  
Polarity Switching ◽  
Validation Parameters ◽  
Wide Range ◽  
Aqueous Component ◽  
Positive Mode

Abstract The purpose of this study was to develop an LC-tandem MS method for the simultaneous detection of common synthetic drugs as adulterants in natural and herbal slimming products. Sixteen drugs belonging to a wide range of pharmaceutical classes were studied. Included in the list of drugs were anorexics, anxiolytics, antidepressants, diuretics, laxatives, and stimulants. The method used a C18 column (4.6 × 50 mm and 1.8 μm particle size). Separation of the drugs was achieved by gradient elution using 4 mM ammonium formate in water + 0.1% formic acid as the aqueous component and 4 mM ammonium formate in methanol + 0.1% formic as the organic component of the mobile phase. As not all of the analytes ionized in the positive mode, the mass spectrometer was operated in the electrospray ionization mode with polarity switching. The samples were extracted with methanol and the use of 50% acetonitrile in water and 50% methanol in water were investigated as diluents for injection into the LC-MS system. Utilizing both diluents, the validation parameters including accuracy, precision, LOD, and LOQ were assessed. The validation results and utilization of the method to analyze a variety of weight-loss supplements indicate that the two diluents give similar results and can be used interchangeably. This knowledge provides the user with the option of selecting either diluent for sample preparation depending on the sample matrix without having to revalidate the method. The method was applied to the analysis of weight-loss supplements available in local pharmacies, herbal pharmacies, and over the Internet.

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