Transformation Textures in Unstable Austenitic Steel

2002 ◽  
Vol 125 (1) ◽  
pp. 12-17 ◽  
Author(s):  
R. Kubler ◽  
M. Berveiller ◽  
M. Cherkaoui ◽  
K. Inal
Keyword(s):  
Martensitic Transformation ◽  
Volume Fraction ◽  
Micromechanical Model ◽  
Slip Rate ◽  
Transformation Strain ◽  
Dislocation Motion ◽  
Lattice Spin ◽  
Two Phases ◽  
The One ◽  
Elastic Plastic Materials

During the martensitic transformation in elastic-plastic materials, the local transformation strain as well as the plastic flow inside austenite are strongly related with the crystallographic orientation of the austenitic lattice. Two mechanisms involved in these materials, i.e., plasticity by dislocation motion and martensitic phase formation are coupled through kinematical constraints so that the lattice spin of the austenitic grains is different from the one due to classical slip. In this work, the lattice spin ω˙eA of the austenitic grains is related with the slip rate on the slip systems of the two phases, γ˙A and γ˙M, the evolution of the martensite volume fraction f˙ and the overall rotation rate Ω˙ of the grains. This new relation is integrated in a micromechanical model developed for unstable austenite in order to predict the evolution of the austenite texture during TRansformation Induced Plasticity (TRIP). Results for the evolution of the lattice orientation during martensitic transformation are compared with experimental data obtained by X-ray diffraction on a 304 AISI steel.

Coefficients of thermal expansion of carbon nanotube-reinforced polyimide nanocomposites: A micromechanical analysis

2016 ◽  
Vol 233 (2) ◽  
pp. 169-179 ◽  
Author(s):  
R Ansari ◽  
MK Hassanzadeh-Aghdam ◽  
A Darvizeh
Keyword(s):  
Thermal Expansion ◽  
Carbon Nanotube ◽  
Present Model ◽  
Volume Fraction ◽  
Critical Role ◽  
Micromechanical Model ◽  
Temperature Deviation ◽  
Two Phases ◽  
Polyimide Matrix ◽  
Good Agreement

In this work, a unit cell-based micromechanical model with a proper representative volume element is proposed to evaluate the coefficients of thermal expansion of carbon nanotube-reinforced polyimide nanocomposites. The model takes an interphase between carbon nanotube and polyimide matrix into account which characterizes the non-bonded van der Waals interaction between two phases. The effects of some important parameters on the coefficients of thermal expansion such as thickness and adhesion exponent of interphase, temperature deviation as well as volume fraction, diameter and waviness of carbon nanotubes are investigated in detail. It is found that the interphase plays a critical role in determining the coefficients of thermal expansion and should be incorporated into the modeling of nanocomposite. According to the obtained results, there exists a specific value for carbon nanotube diameter beyond which further increasing in carbon nanotube diameter does not affect the coefficients of thermal expansion of nanocomposite. Also, the results reveal that the carbon nanotube waviness has a significant influence on the coefficients of thermal expansion of the nanocomposite. The results of the present model are compared with those of finite element method and a very good agreement is pointed out.

scholarly journals A Crystal Plasticity Simulation on Strain-Induced Martensitic Transformation in Crystalline TRIP Steel by Coupling with Cellular Automata

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1316
Author(s):  
Truong Duc Trinh ◽  
Takeshi Iwamoto
Keyword(s):  
Martensitic Transformation ◽  
Cellular Automata ◽  
Shear Band ◽  
Crystal Plasticity ◽  
Trip Steel ◽  
Volume Fraction ◽  
Transformation Strain ◽  
Martensitic Phase ◽  
Shear Band Formation ◽  
Band Formation

In transformation-induced plasticity (TRIP) steel, the strain-induced martensitic transformation (SIMT) has a close relationship with the shear band formation. At a small length scale such as that of a crystal, the explicit analysis of the shear band structure with the formed microstructure is quite important for an adequate understanding of the SIMT. Here, a study on the microstructures formed by SIMT, related to shear band formation in both single and polycrystal TRIP steels, is presented. The constitutive equation for single crystal TRIP steel considering the transformation strain on each variant system is derived based on a rate-dependent crystal plasticity theory. To express the martensitic transformation, the cellular automata approach, including a transformation criterion acting as a local rule, is introduced. Numerical simulation is conducted with patterning processes of the martensitic phase at an infinite medium under the plane strain tension. It is found that the similar distributions of the plastic strain and the martensitic phase are dependent on the initial crystal orientation and appear as the shear band structures. In addition, the sizes of embryo and cell strongly influence the shear band formation and the martensitic volume fraction of crystal TRIP steel.

Preparation of Electron Transparent Metal-Matrix Composites

1968 ◽  
Vol 26 ◽  
pp. 334-335 ◽  
Author(s):  
M. R. Pinnel ◽  
A. Lawley
Keyword(s):  
Stainless Steel ◽  
Load Transfer ◽  
Volume Fraction ◽  
Steel Wire ◽  
Initial Step ◽  
Interfacial Region ◽  
Matrix Composites ◽  
Specific Test ◽  
The Matrix ◽  
The One

Numerous phenomenological descriptions of the mechanical behavior of composite materials have been developed. There is now an urgent need to study and interpret deformation behavior, load transfer, and strain distribution, in terms of micromechanisms at the atomic level. One approach is to characterize dislocation substructure resulting from specific test conditions by the various techniques of transmission electron microscopy. The present paper describes a technique for the preparation of electron transparent composites of aluminum-stainless steel, such that examination of the matrix-fiber (wire), or interfacial region is possible. Dislocation substructures are currently under examination following tensile, compressive, and creep loading. The technique complements and extends the one other study in this area by Hancock.The composite examined was hot-pressed (argon atmosphere) 99.99% aluminum reinforced with 15% volume fraction stainless steel wire (0.006″ dia.).Foils were prepared so that the stainless steel wires run longitudinally in the plane of the specimen i.e. the electron beam is perpendicular to the axes of the wires. The initial step involves cutting slices ∼0.040″ in thickness on a diamond slitting wheel.

The stabilization of B.C.C. Cu in Cu/Nb nanolayered composites

1996 ◽  
Vol 54 ◽  
pp. 228-229
Author(s):  
H. Kung ◽  
A.J. Griffin ◽  
Y.C. Lu ◽  
K.E. Sickafus ◽  
T.E. Mitchell ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Layer Thickness ◽  
Volume Fraction ◽  
Ion Beam ◽  
High Strength ◽  
Cross Sectional ◽  
Metastable Structure ◽  
High Resolution Tem ◽  
Potential Improvement ◽  
Two Phases

Materials with compositionally modulated structures have gained much attention recently due to potential improvement in electrical, magnetic and mechanical properties. Specifically, Cu-Nb laminate systems have been extensively studied mainly due to the combination of high strength, and superior thermal and electrical conductivity that can be obtained and optimized for the different applications. The effect of layer thickness on the hardness, residual stress and electrical resistivity has been investigated. In general, increases in hardness and electrical resistivity have been observed with decreasing layer thickness. In addition, reduction in structural scale has caused the formation of a metastable structure which exhibits uniquely different properties. In this study, we report the formation of b.c.c. Cu in highly textured Cu/Nb nanolayers. A series of Cu/Nb nanolayered films, with alternating Cu and Nb layers, were prepared by dc magnetron sputtering onto Si {100} wafers. The nominal total thickness of each layered film was 1 μm. The layer thickness was varied between 1 nm and 500 nm with the volume fraction of the two phases kept constant at 50%. The deposition rates and film densities were determined through a combination of profilometry and ion beam analysis techniques. Cross-sectional transmission electron microscopy (XTEM) was used to examine the structure, phase and grain size distribution of the as-sputtered films. A JEOL 3000F high resolution TEM was used to characterize the microstructure.

Direct imaging of order-disorder and antiphase domain structures in Ti3Al intermetallic compound

1990 ◽  
Vol 48 (4) ◽  
pp. 480-481
Author(s):  
H. Q. Ye ◽  
T.S. Xie ◽  
D. Li
Keyword(s):  
Intermetallic Compound ◽  
Volume Fraction ◽  
Fundamental Problem ◽  
Antiphase Domain ◽  
Atomic Scale ◽  
Orientation Relationships ◽  
Domain Structures ◽  
Α Phase ◽  
Diffraction Patterns ◽  
Two Phases

The Ti3Al intermetallic compound has long been recognized as potentially useful structural materials. It offers attractive strength to weight and elastic modulus to weight ratios. Recent work has established that the addition of Nb to Ti3Al ductilized this compound. In this work the fundamental problem of this alloy, i.e. order-disorder and antiphase domain structures was investigated at the atomic scale.The Ti3Al+10at%Nb alloys used in this study were treated at 1060°C and then aged at 700°C for 2 hours. The specimens suitable for TEM were prepared by standard jet electrolytic-polishing technique. A JEM-200CX electron microscope with an interpretable resolution of about 0.25 nm was used for HREM.The [100] and [001] projections of the α2 phase were shown in Fig.l.The alloy obtained consist of at least two phases-α2(Ti3Al) and β0 structures. Moreover, a disorder α phase with small volume fraction was also observed. Fig.2 gives [100] and [001] diffraction patterns of the α2 phase. Since lattice parameters of the ordered α2 (a=0.579, c=0.466 nm) and disorder α phase (a0=0.294≈a/2, c0=0.468 nm) are almost the same, their diffraction patterns are difficult to be distinguished when they are overlapped with epitaxial orientation relationships.

Political Islam in an Ethnic Jewish State: Historical Evolution, Contemporary Challenges and Future Prospects

2004 ◽  
Vol 3 (1) ◽  
pp. 69-92 ◽  
Author(s):  
Nohad ‘Ali
Keyword(s):  
Historical Evolution ◽  
Jewish State ◽  
Islamic Revival ◽  
Islamic Movement ◽  
Revival Movements ◽  
Phases Of Development ◽  
Two Phases ◽  
The One ◽  
Five Phases ◽  
Islamic Revivalism

This paper argues that, although the shared and universal ideology of the Islamic revival movements was adopted by the Islamic movement in Israel, the movement has been trying to embody it in diverse and distinctive ways. In principle there is a conflict between commitment to the principle of Islamic revivalism on the one hand, and being so committed in the specific context of the ethnic Jewish state, on the other. The Jewish context of the State of Israel continues to bedevil the development of the Islamic movement in Israel. Since the 1930s, Islamic revivalism in Palestine has undergone five phases of development: the Egyptian, Israeli, Palestinian, and the two phases of ‘adaptation’ and ‘post-adaptation’. These phases reflect ideological developments, rather than simply a historical evolution. They are also the outcome of three sets of constraints: structural, ideological and domestic.

scholarly journals The stratified disc wind of MCG-03-58-007

2020 ◽  
Vol 500 (1) ◽  
pp. 291-300
Author(s):  
V Braito ◽  
J N Reeves ◽  
P Severgnini ◽  
R Della Ceca ◽  
L Ballo ◽  
...  
Keyword(s):  
Absorption Line ◽  
Velocity Component ◽  
Column Density ◽  
Accretion Disc ◽  
Line Profiles ◽  
Lower Velocity ◽  
Multiple Observations ◽  
Two Phases ◽  
The One ◽  
High Column

ABSTRACT Past Suzaku, XMM–Newton, and NuSTAR observations of the nearby (z = 0.03233) bright Seyfert 2 galaxy MCG-03-58-007 revealed the presence of two deep and blue-shifted iron K-shell absorption line profiles. These could be explained with the presence of two phases of a highly ionized, high column density accretion disc wind outflowing with vout1 ∼ −0.1c and vout2 ∼ −0.2c. Here we present two new observations of MCG-03-58-007: one was carried out in 2016 with Chandra and one in 2018 with Swift. Both caught MCG-03-58-007 in a brighter state ($F_{{\mathrm{2}-10\, keV}} \sim 4 \times 10^{-12}$ erg cm−2 s−1) confirming the presence of the fast disc wind. The multi-epoch observations of MCG-03-58-007 covering the period from 2010 to 2018 were then analysed. These data show that the lower velocity component outflowing with vout1 ∼ −0.072 ± 0.002c is persistent and detected in all the observations, although it is variable in column density in the range NH ∼ 3–8 × 1023 cm−2. In the 2016 Swift observation we detected again the second faster component outflowing with vout2 ∼ −0.2c, with a column density ($N_{\mbox{H}}=7.0^{+5.6}_{-4.1}\times 10^{23}$ cm−2), similar to that seen during the Suzaku observation. However during the Chandra observation 2 yr earlier, this zone was not present (NH < 1.5 × 1023 cm−2), suggesting that this faster zone is intermittent. Overall the multi-epochs observations show that the disc wind in MCG-03-58-007 is not only powerful, but also extremely variable, hence placing MCG-03-58-007 among unique disc winds such as the one seen in the famous QSO PDS456. One of the main results of this investigation is the consideration that these winds could be extremely variable, sometime appearing and sometime disappearing; thus to reach solid and firm conclusions about their energetics multiple observations are mandatory.

scholarly journals An Intrinsic Material Tailoring Approach for Functionally Graded Axisymmetric Hollow Bodies Under Plane Elasticity

2021 ◽  
Author(s):  
Hassan Mohamed Abdelalim Abdalla ◽  
Daniele Casagrande
Keyword(s):  
Optimization Problem ◽  
Volume Fraction ◽  
Minimum Principle ◽  
Equivalent Stress ◽  
Micromechanical Model ◽  
Plane Elasticity ◽  
Functionally Graded ◽  
Pontryagin Minimum Principle ◽  
Volume Fractions ◽  
Material Tailoring

AbstractOne of the main requirements in the design of structures made of functionally graded materials is their best response when used in an actual environment. This optimum behaviour may be achieved by searching for the optimal variation of the mechanical and physical properties along which the material compositionally grades. In the works available in the literature, the solution of such an optimization problem usually is obtained by searching for the values of the so called heterogeneity factors (characterizing the expression of the property variations) such that an objective function is minimized. Results, however, do not necessarily guarantee realistic structures and may give rise to unfeasible volume fractions if mapped into a micromechanical model. This paper is motivated by the confidence that a more intrinsic optimization problem should a priori consist in the search for the constituents’ volume fractions rather than tuning parameters for prefixed classes of property variations. Obtaining a solution for such a class of problem requires tools borrowed from dynamic optimization theory. More precisely, herein the so-called Pontryagin Minimum Principle is used, which leads to unexpected results in terms of the derivative of constituents’ volume fractions, regardless of the involved micromechanical model. In particular, along this line of investigation, the optimization problem for axisymmetric bodies subject to internal pressure and for which plane elasticity holds is formulated and analytically solved. The material is assumed to be functionally graded in the radial direction and the goal is to find the gradation that minimizes the maximum equivalent stress. A numerical example on internally pressurized functionally graded cylinders is also performed. The corresponding solution is found to perform better than volume fraction profiles commonly employed in the literature.

Characterization of the vibration, stability and static responses of graphene-reinforced sandwich plates under mechanical and thermal loadings using the refined shear deformation plate theory

2021 ◽  
pp. 109963622199386
Author(s):  
Hessameddin Yaghoobi ◽  
Farid Taheri
Keyword(s):  
Shear Deformation ◽  
Volume Fraction ◽  
Plate Theory ◽  
Micromechanical Model ◽  
Sheet Thickness ◽  
Analytical Investigation ◽  
Sandwich Plates ◽  
Simply Supported ◽  
Vibration Stability ◽  
Shear Deformation Plate Theory

An analytical investigation was carried out to assess the free vibration, buckling and deformation responses of simply-supported sandwich plates. The plates constructed with graphene-reinforced polymer composite (GRPC) face sheets and are subjected to mechanical and thermal loadings while being simply-supported or resting on different types of elastic foundation. The temperature-dependent material properties of the face sheets are estimated by employing the modified Halpin-Tsai micromechanical model. The governing differential equations of the system are established based on the refined shear deformation plate theory and solved analytically using the Navier method. The validation of the formulation is carried out through comparisons of the calculated natural frequencies, thermal buckling capacities and maximum deflections of the sandwich plates with those evaluated by the available solutions in the literature. Numerical case studies are considered to examine the influences of the core to face sheet thickness ratio, temperature variation, Winkler- and Pasternak-types foundation, as well as the volume fraction of graphene on the response of the plates. It will be explicitly demonstrated that the vibration, stability and deflection responses of the sandwich plates become significantly affected by the aforementioned parameters.

Finite Element Model to Predict the Bioconversion Rate of Glucose to Fructose using Escherichia coli K12 for Sugar Production from Date

2015 ◽  
Vol 11 (1) ◽  
pp. 105-113 ◽  
Author(s):  
Maher Trigui ◽  
Karim Gabsi ◽  
Walid Zneti ◽  
Suzelle Barrington ◽  
Ahmed Noureddine Helal
Keyword(s):  
Escherichia Coli ◽  
Induction Time ◽  
Volume Fraction ◽  
Element Model ◽  
Initial Concentration ◽  
Computational Fluids Dynamics ◽  
Date Syrup ◽  
Computational Fluids ◽  
Two Phases ◽  
Inoculum Volume

Abstract In this study, Bioconversion process of glucose to fructose from date syrup using Escherichia coli K12 is modeled using a commercial computational fluids dynamics (CFD) code fluent FLUENT 6.3.23 [8] which we implemented a user-defined functions (UDF) to simulate the interrelationships at play between various phases. A two phases CFD model was developed using an Eulerian – Eulerian approach to calculate the fructose volume fraction produced during time. The bioconversion process was studied as function of three initial concentration of glucose (0.14, 0.242 and 0.463gL–1), three induction time (60, 120 and 180 mn) and three inoculum volume (100, 120 and 150mL). The numerical results are compared with experimental data for bioconversion rate and show good agreement (R2= 0.894). The optimal condition of diffusion was obtained by applying an initial concentration of glucose less than 0.2gL–1 and induction time great than 100 minutes.

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