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Parsing the effect of slip-twin interactions on the strain rate and thermal sensitivities of Magnesium (Mg) alloys has been a challenging endeavor for scientists preoccupied with the mechanical behavior of hexagonal close-packed alloys, especially those with great latent economic potential such as Mg. One of the main barriers is the travail entailed in fitting the various stress–strain behaviors at different temperatures, strain rates, loading directions applied to different starting textures. Taking on this task for two different Mg alloys presenting different textures and as such various levels of slip-twin interactions were modeled using visco-plastic self-consistent (VPSC) code. A recently developed routine that captures dislocation transmutation by twinning interfaces on strain hardening within the twin lamellae was employed. While the strong texture was exemplified by traditional rolled AZ31 Mg alloys, the weak texture was represented by ZEK100 Mg alloy sheets. The transmutation model incorporated within a dislocation density based hardening model showed enhanced flexibility in predicting the complex strain rate and thermal sensitive behavior of Mg textures' response to various mechanical loading schemes. [ABSTRACT FROM AUTHOR]

An experimental and numerical study of femtosecond laser-induced surface damage of the potassium dihydrogen phosphate (KDP) crystals doped with Zn2+ is presented. Based on COMSOL® Multiphysics 6.1, electron-lattice nonequilibrium interactions were simulated to obtain the temporal evolution of electron concentration, electron temperature, and lattice temperature. The surface damage profile of the samples was analyzed by optical microscopy, and the single-pulse damage threshold was determined. Raman spectra shows that the chemistry of the crystals appeared to remain constant before and after the damage. Single-particle fluorescence spectroscopy indicates that the fluorescence intensity first decreased and then increased with increasing doping concentration. However, the laser-induced damage threshold (LIDT) was negatively correlated with the defect concentration, which may be a result of the synergistic effect of nonlinear adsorption and defect concentration. The above work attempts to give a rational explanation for the process of femtosecond laser damage to the surface of KDP crystals. [Display omitted] • Femtosecond laser surface damage characteristics of KDP crystal are investigated. • No changes in the chemistry structure occur after femtosecond laser damage. • The damage threshold is negatively correlated with the defect concentration. • Electron-lattice interactions are simulated by a self-consistent model. • Nonlinear absorption and defects are studied to explain damage mechanisms. [ABSTRACT FROM AUTHOR]

• Finite strain algorithmic self-consistent model is proposed for elasto-viscoplastic deformed polycrystal. • The Mori–Tanaka model is extended for multi-phase polycrystal at finite strain. • Performance of the algorithmic self-consistent model is compared to the model adopting extended Taylor hypothesis. • Grain level and polycrystalline level behaviors are both compared to the full-filed model. • The effects of void and elastic particles are investigated by the extended Mori–Tanaka model. A finite strain micromechanical-based constitutive model is developed for multi-phase polycrystal to characterize the interplay among strain hardening, texture evolution, and stress-strain relation. The phases are regarded as ellipsoidal inhomogeneities within the polycrystalline matrix, which can be considered as an aggregation of different orientated grains. At the grain level, the crystal plasticity model is applied to physically describe the inelastic deformation results from crystallographic slipping. At the polycrystalline level, an algorithmic finite strain self-consistent model is proposed to associate the strain and rotation rate at the grain level with the corresponding terms of the polycrystalline matrix rigorously. At the representative volume element level, the phases with different properties are investigated by extending the Mori–Tanaka model at finite strain. The algorithmic self-consistent model is validated by comparing the calculated normalized stress-strain curves and textures with those obtained by the model adopting extended Taylor hypothesis and the experimental data of stainless steel. Moreover, the grain and polycrystalline level behaviors calculated by the algorithmic self-consistent model are compared to those derived from the full-field model. The effects of void and elastic particles on overall mechanical behavior are analyzed by the extended Mori–Tanaka model, which is then verified by predicting the mechanical behavior of sintered nano-silver stub columns under stress-controlled compression loads. [Display omitted] [ABSTRACT FROM AUTHOR]

Parsing the effect of slip-twin interactions on the strain rate and thermal sensitivities of Magnesium (Mg) alloys has been a challenging endeavor for scientists preoccupied with the mechanical behavior of hexagonal close-packed alloys, especially those with great latent economic potential such as Mg. One of the main barriers is the travail entailed in fitting the various stress–strain behaviors at different temperatures, strain rates, loading directions applied to different starting textures. Taking on this task for two different Mg alloys presenting different textures and as such various levels of slip-twin interactions were modeled using visco-plastic self-consistent (VPSC) code. A recently developed routine that captures dislocation transmutation by twinning interfaces on strain hardening within the twin lamellae was employed. While the strong texture was exemplified by traditional rolled AZ31 Mg alloys, the weak texture was represented by ZEK100 Mg alloy sheets. The transmutation model incorporated within a dislocation density based hardening model showed enhanced flexibility in predicting the complex strain rate and thermal sensitive behavior of Mg textures’ response to various mechanical loading schemes.

The mechanical analysis of complex rock mass is a difficult problem, which often occurs in scientific research and practical engineering. Many achievements have been made in the study of rock mass composite problems by composite material micromechanics method, but it has not been well summarized so far. This paper summarizes in detail the research status of complex rock mass problems by composite material micromechanics method at home and abroad, including the application of the Eshelby equivalent inclusion theory and self-consistent model in rock mass composite problems, and the application of the homogenization method in jointed rock mass and other rock mass composite problems such as anchored rock mass, layered rock mass, and salt rock mass with impurities. It is proposed that the structural similarity and mechanical analysis similarity should be satisfied when the composite material micromechanics method is used to study the complex rock mass. Finally, the problems that need to be further studied are put forward. The research results provide a valuable reference for the study of complex rock mass by the composite material micromechanics method.

Abstract The viscosity structure of Earth's mantle, even the 1‐D radial viscosity profile, remains not well constrained. The dynamics of the subducting slabs is strongly affected by, and can be used to constrain, the viscosity structure of the mantle. Here, we perform fully dynamic, self‐consistent mantle convection models to study the dynamics of subducted slabs in the deep mantle. We use a statistical analysis approach to quantify how the depth distribution of flat‐lying slabs is affected by the depth‐dependence of mantle viscosity. We find that, for cases in which the viscosity increases at 660 km depth, whether sharply or gradually, flat‐lying slabs preferentially occur above this depth, and importantly, up to ∼30% of the subducted slabs previously flatted at this depth later sink to the deep lower mantle and maintain a flat‐lying morphology. The frequency of (or the probability to have) flat‐lying slabs at ∼1,000 km depth in these cases is similar to cases in which the viscosity jump occurs at 1,000 km depth. Therefore, to explain the presence of flat‐lying slabs at ∼1,000 km depth for the Earth does not require a viscosity jump at this depth. In contrast, a viscosity jump merely occurring at ∼1,000 km depth causes a lack of flat‐lying slabs in the uppermost lower mantle at ∼700–900 km depth and is inconsistent with seismic observations. The presence of flat‐lying slab materials in the Earth's uppermost lower mantle requires a viscosity increase at 660 km depth.

The viscosity structure of Earth's mantle, even the 1‐D radial viscosity profile, remains not well constrained. The dynamics of the subducting slabs is strongly affected by, and can be used to constrain, the viscosity structure of the mantle. Here, we perform fully dynamic, self‐consistent mantle convection models to study the dynamics of subducted slabs in the deep mantle. We use a statistical analysis approach to quantify how the depth distribution of flat‐lying slabs is affected by the depth‐dependence of mantle viscosity. We find that, for cases in which the viscosity increases at 660 km depth, whether sharply or gradually, flat‐lying slabs preferentially occur above this depth, and importantly, up to ∼30% of the subducted slabs previously flatted at this depth later sink to the deep lower mantle and maintain a flat‐lying morphology. The frequency of (or the probability to have) flat‐lying slabs at ∼1,000 km depth in these cases is similar to cases in which the viscosity jump occurs at 1,000 km depth. Therefore, to explain the presence of flat‐lying slabs at ∼1,000 km depth for the Earth does not require a viscosity jump at this depth. In contrast, a viscosity jump merely occurring at ∼1,000 km depth causes a lack of flat‐lying slabs in the uppermost lower mantle at ∼700–900 km depth and is inconsistent with seismic observations. The presence of flat‐lying slab materials in the Earth's uppermost lower mantle requires a viscosity increase at 660 km depth. Plain Language Summary: Conventionally, a stepwise mantle viscosity jump is often modeled at 660 km depth where the endothermic phase transition occurs. However, some recent studies argued that the viscosity may increase at deeper depths of ∼1,000 km. Here, dynamically self‐consistent mantle convection models are performed to investigate the effect of the depth‐dependent mantle viscosity structure on slab morphologies. We quantify the statistics for the depth distribution of flat‐lying slabs with subducted slabs freely generated as a form of thermal boundary layer instabilities in mantle convection models. The models show that a stepwise viscosity increase at ∼1,000 km depth results in the absence of flat‐lying slabs at intermediate depths of 700–900 km below the transition zone. This is inconsistent with seismic tomography observations which indicate significant flat‐lying slab materials at ∼700–900 km depths. The viscosity increase at 660 km depth is therefore essential to cause flat‐lying slabs in the uppermost lower mantle. Key Points: A statistical analysis is introduced to study the probability of slab stagnation events in fully dynamic, self‐consistent convection modelsA viscosity jump at either 660 or 1,000 km depth causes similar frequency of flat‐lying slabs at ∼1,000 km depthA viscosity jump at 1,000 km depth alone causes a lack of flat‐lying slabs in the uppermost lower mantle that is inconsistent with observations [ABSTRACT FROM AUTHOR]

Abstract Micromechanics based models are used for predicting the effective mechanical properties of reinforced polymer matrix composites. This paper reviews micromechanics based models for fiber reinforced polymer composites starting with the bounds established by Voigt and Reuss models, Hashin-Shtrikman model and then on to well-known micromechanics based models like Mori-Tanaka model, Self-consistent model and Differential scheme based models. The main objective is to critically review the areas in which these micromechanics based models hold good and analyse the limitations of these models. One of the limitations of the above mentioned models is the assumption of dilute dispersion and this is overcome in this paper by revising the Mori-Tanaka model by combining the differential scheme with Eshelby's model to take into account the non-dilute dispersion effect. Numerical results are verified by finite element based simulation of the representative volume element (RVE). Experiments were carried out to estimate the effective elastic constants for different fiber volume fractions. Theoretical results are reviewed with reference to experimental measurements. [ABSTRACT FROM AUTHOR]

For polycrystalline materials, the experimental determination of residual stresses neglects the so-called 2nd order fluctuations arising from e.g. plastic or thermal incompatibilities from grain to grain. This constitutes a serious limitation of the classical measurements methods, since these 2nd residual stresses are known to have a major influence on the mechanical behavior of metallic alloys, especially if these are strongly textured. In the present paper, a new methodology for the treatment of the measured data is described and compared to classical ones. In order to do so, the simulation of a tensile test is performed using a self-consistent elasto-plastic model, in order to constitute a virtual experimental data set. The 1st and 2nd order stresses are extracted from the simulation for various macroscopic stress levels. Two approaches (the classical sin2ψ method and a method based on the simultaneous analysis of several X-ray diffraction peaks) are then used to quantify the 1st order stresses from these “experimental” data. It is clearly shown that the method based on multi-peak analysis allows to minimize the error made by neglecting the so-called 2nd order stresses and leads to a better quantitative estimation of the 1st order stresses. [ABSTRACT FROM AUTHOR]

Quasi-isotropic strands made of second generation (2G) high temperature superconducting (HTS) wires are attractive to applications of high-field magnets at low temperatures and power transmission cables at liquid nitrogen temperature in virtue of their high current carrying capability and well mechanical property. In this contribution, a 10 m length quasi-isotropic strand is manufactured and successfully tested in liquid nitrogen to verify the feasibility of an industrial scale production of the strand by the existing cabling technologies. The strand with copper sheath consists of 72 symmetrically assembled 2G wires. The uniformity of critical properties of long quasi-isotropic strands, including critical current and n -value, is very important for their using. Critical currents as well as n -values of the strand are measured every 1 m respectively and compared with the simulation results. Critical current and n -value of the strand are calculated basing on the self-consistent model solved by the finite element method (FEM). Effects of self-field on the critical current and n -value distributions in wires of the strand are analyzed in detail. The simulation results show good agreement with the experimental data and the 10 m quasi-isotropic strand has good critical properties uniformity. [ABSTRACT FROM AUTHOR]

A single quantum well semiconductor laser based on wurtzite-nitride is designed and analyzed for short distance communication wavelength (at around 1300 nm). The laser structure has 12 Å well layer of InN, 15 Å barrier layer of In0.25Ga0.75N, and 54 Å separate confinement heterostructure layer of GaN. To calculate the electronic characteristics of the structure, a self-consistent method is used where Hamiltonian with effective mass approximation is solved for conduction band while six-bands Hamiltonian matrix with k · p formalism including the polarization effect, valence-band mixing effect, and strain effect is solved for valence band. The interband optical transition elements, optical gain, differential gain, radiative current density, spontaneous emission rate, and threshold characteristics have been calculated. The wave function overlap integral is found to be 45.93% for TE-polarized structure. Also, the spontaneous emission rate is found to be 6.57 × 1027 s-1 cm-3 eV-1 at 1288.21 nm with the carrier density of 5 × 1019 cm-3. Furthermore, the radiative current density and the radiative recombination rate are found to be 121.92 Acm-2 and 6.35 × 1027 s-1 cm-3, respectively, while the TE-polarized optical gain of the structure is 3872.1 cm-1 at 1301.7 nm. [ABSTRACT FROM AUTHOR]

The mechanical behaviour of each phase in two-phase titanium Ti-18 was studied at room temperature under a low strain rate tensile test until fracture. Due to its selectivity, the X-ray diffraction method was applied for in-situ tensile test to analyse the behaviour of each phase in the direction perpendicular to the loading force. In addition, the biaxial stress states of the initial sample, as well as those of the sample during the tensile test, were determined using multi-reflection grazing incidence X-ray diffraction (MGIXD). The experimental data were compared with the prediction of an elasto-plastic self-consistent model in order to study slips on crystallographic planes and mechanical effects occurring during plastic deformation. [ABSTRACT FROM AUTHOR]

The coefficient of thermal expansion (CTE) of concrete depends on temperature, the internal structure of concrete, and the moisture content in concrete. An analytical model was developed to characterize the CTE of concrete under low temperatures. Three pore configurations are defined as pores with water and pores with ice. The effective strain of concrete is a combination of three processes during the cooling process, each containing a different configuration of pores. A general multiphase model for the effective expansion (and contraction) of concrete with a certain amount of ice was developed. The model can predict effective strain at different temperatures, which can reflect the influences of concrete pore size distribution and volume fractions of different phases. The predictions by the present model were compared with some available experimental data, and they agreed very well. [ABSTRACT FROM AUTHOR]

A combined thermodynamic/kinetic approach is adopted to derive the climb-controlled recovery of dislocation junctions on individual slip planes in a material during creep when dislocation core diffusion is the rate controlling kinetic process. The model is used in an integrated multi-scale crystal plasticity/creep self-consistent framework to evaluate the effect of creep pre-strain on the Bauschinger effect in a polycrystalline austenitic stainless steel. The model predictions are in good agreement with experimental findings of the effect of tensile creep on the subsequent low temperature response in tension and compression and on the development of residual stresses determined from neutron diffraction studies. [ABSTRACT FROM AUTHOR]

The goal of this work was the determination of lattice strains distribution in two phases of duplex steel during plastic necking. Subsequently, the stress heterogeneity in the neck was studied in order to determine the reason for the damage initiation and to verify the hypothesis that the damage begins in the ferritic phase. To do this, X-ray synchrotron radiation was used to scan the ‘in situ’ variation of the interplanar spacings along the necking zone for samples subjected to tensile loading. A self-consistent model and FEM simulation were applied for the experimental data interpretation. It was found that for advanced necking the phase lattice strains, especially those measured at some distance from the neck centre, show a large inversion of the loads localised in both phases compared to the undamaged state (the lattice strains in the ferrite become smaller than in the austenite). This effect indicates stress relaxation in the ferrite which is connected with the damage phenomenon. Correlation of the experimental results with the modelling shows that the value of von Mises stress is responsible for the initiation of the ferritic phase softening. [ABSTRACT FROM AUTHOR]

The self-consistent concept recently published in this journal (108, 27–30, 2015) is extended from a binary to a multicomponent system. This is possible by exploiting the trapping concept as basis for including the interaction of atoms in terms of pairs (e.g. A–A, B–B, C–C…) and couples (e.g. A–B, B–C, …) in a multicomponent system with A as solvent and B, C, … as dilute solutes. The model results in a formulation of Gibbs-energy, which can be minimized. Examples show that the couple and pair formation may influence the equilibrium Gibbs energy markedly. [ABSTRACT FROM AUTHOR]

In this work, a physically based self-consistent model is developed and employed to examine the microscopic lattice response of pre-strained Type 316H polycrystalline austenitic stainless steel subjected to uniaxial tensile and compressive loading. The model is also used to explain the Bauschinger effect observed at the macroscopic length-scale. Formulated in a crystal based plasticity framework, the model incorporates detailed strengthening effects associated with different microstructural elements such as forest dislocation junctions, solute atoms and precipitates on individual crystallographic slip planes of each individual grain within the polycrystal. The elastoplastic response of the bulk polycrystal is obtained by homogenizing the response of all the constituent grains using a self-consistent approach. Micro-plasticity mechanisms and how these influence the Bauschinger effect are illustrated in terms of the role of residual stresses at different length-scales. Overall, predictions are in good agreement with experimental data of the Bauschinger effect and the corresponding meso-scale lattice response of the material, with the latter measured by neutron diffraction. The results demonstrate that transient softening of the material is related to residual stresses at different length scales. In addition, the (Type III) residual stress at the micro-scale slip system level extends the strain range over which the tensile and compressive reloading curves of the pre-strained material merge. [ABSTRACT FROM AUTHOR]

The aim of this paper is to investigate the impact of the microscopic yield surface (i.e., at the single crystal scale) on the forming limit diagrams (FLDs) of face centred cubic (FCC) materials. To predict these FLDs, the bifurcation approach is used within the framework of rate-independent crystal plasticity theory. For this purpose, two micromechanical models are developed and implemented. The first one uses the classical Schmid law, which results in the formation of vertices (or corners) at the yield surface, while the second is based on regularization of the Schmid law, which induces rounded corners at the yield surface. In both cases, the overall macroscopic behavior is derived from the behavior of the microscopic constituents (the single crystals) by using two different scale-transition schemes: the selfconsistent approach and the Taylor model. The simulation results show that the use of the classical Schmid law allows predicting localized necking at realistic strain levels for the whole range of strain paths that span the FLD. However, the application of a regularized Schmid law results in much higher limit strains in the range of negative strain paths. Moreover, rounding the yield surface vertices through regularization of the Schmid law leads to unrealistically high limit strains in the range of positive strain paths. [ABSTRACT FROM AUTHOR]

In situ neutron diffraction experiments have been performed under uniaxial tensile testing in a commercially pure titanium in order to determine strain pole figures. The evolution of intergranular strains was observed in the bulk material along multiple orientations for 4 reflections: {10.0}, {10.1}, {11.0} and {00.2}. The experimental data was used to test an elasto-plastic self-consistent model. A particular focus has been devoted to the relationship between the internal strains and the deformation systems activity. The model was in agreement with the experiments, and the simulations reproduced the main features observed on the in situ measured strain pole figures. [ABSTRACT FROM AUTHOR]

Differently oriented grains within a polycrystalline material exhibit different micro-mechanical lattice responses for a given macroscopic stress due to the local elastic and plastic anisotropy. A physical understanding of the lattice deformation mechanism during plastic flow is still lacking. In this study, a three-dimensional multi-scale self-consistent model is developed to examine the micro-mechanical deformation behaviour of F.C.C. polycrystalline austenitic stainless steels under uniaxial tensile loading at ambient temperature. The model is formulated in a crystal based plasticity framework and takes into account the detailed kinematics of dislocation slip and its influence on the evolution of the dislocation distribution on different crystallographic planes of individual grains within a polycrystalline material. The effect of athermal solute strengthening is also incorporated. Predictions of the microscopic lattice response developed within individual grains are compared with various available experimental results obtained using neutron diffraction (ND). There are significant differences in the way in which the lattice strain evolves with macroscopic strain obtained by different groups. This is explained in terms of the variation in initial residual stress state in the samples tested by these different groups. [ABSTRACT FROM AUTHOR]

A self-consistent model for the electronic component of a thin current sheet (TCS) of the Earth's magnetosphere based on the concept of the tension of lines of force is proposed and studied analytically and numerically. It has been shown that the model has a certain range of applicability, beyond which the results may be incorrect; within the range of correctness the model allows for a quite significant increase in the rate of convergence of the iterative algorithm for solving the total self-consistent model of the TCS, which also includes the Boltzmann equations for the ionic component. [ABSTRACT FROM AUTHOR]

The newly developed self-consistent model exploits the trapping concept and calculates the numbers of A–A, A–B and B–B bonds in A–B alloys in dependence of the bond-energy parameter. Consequently the self-consistent model improves the classical regular solution model utilizing the assumption of random distribution of solute atoms. Remarkable differences between both models are demonstrated. The self-consistent model may significantly reduce the number of fitting parameters in the CALPHAD approach as well as experimental efforts. [ABSTRACT FROM AUTHOR]

Multireflection grazing-incidence X-ray diffraction (MGIXD) was used to determine the stress- and strain-free lattice parameter in the surface layer of mechanically treated (polished and ground) tungsten and austenitic steel. It was shown that reliable diffraction stress analysis is possible only when an appropriate grain interaction model is applied to an anisotropic sample. Therefore, verification of the X-ray stress factors (XSFs) was accomplished by measuring relative lattice strains during an in situ tensile test. The results obtained using the MGIXD and standard methods (χ and ω geometries) show that the Reuss and free-surface grain interaction models agree with the experimental data. Moreover, a new interpretation of the MGIXD results was proposed and applied for the first time to measure the probability of stacking faults as a function of penetration depth for a polished and ground austenitic sample. The XSF models verified in the tensile test were used in the analysis of residual stress components. [ABSTRACT FROM AUTHOR]

The mechanical properties of Hot Mix Asphalt (HMA) mixes are often characterized by its viscoelastic behavior. Viscoelasticity coupled with the thermo-mechanical nature of asphalt offers time-temperature dependence to the mechanical properties of HMA mixes. Also, the wide range of distribution of particles, and several orders of magnitude of differences in the mechanical properties between constituents cause a wide range of stress and strain distribution within the microstructure. In this paper, micromechanical modeling has been performed to study the relationship between individual material properties, their interaction within the microstructure, and the macroscopic properties of HMA mix. The analytical model based on N phase self-consistent scheme allows calculating the complex modulus and phase angle of HMA mixes from the mechanical properties of its constituents and designed mix data. In the mix microstructure, aggregates and sand are classified using simple sieve analysis test. Asphalt and sand mastic film thicknesses around the aggregates are calculated for each class and introduced into the model. [ABSTRACT FROM AUTHOR]

In the context of recent advancements in 3-phase phase-locked loop (PLL) structures to tackle grid imperfections, this paper attempts to shift focus towards dynamic response optimization for fast tracking of disturbed grids, as opposed to Wiener optimization, a trade-off between filtering characteristic and dynamic response. In this respect, an ingenious self-consistent model (SCM)-based approach is proposed which explores filter design in the presence of frequency shifts and phase jumps, and facilitates the analytical computation of unique loop filter parameters. Trial and error in filter parameter selection is inconvenient, but more importantly, even rigorous trials would be insufficient in qualifying the non-existence of a better design. Having eliminated trial and error, this novel technique limits transients to user specifications while fixing on an optimum damping ratio, to yield the best fit. The design methodology is applied to three existing 3-phase PLL structures modelled in MATLAB/Simulink, and the proposed method is further evaluated through extensive simulations and performance comparisons with the traditional Wiener approach. To enhance the understanding of model behaviour and the feasibility of practical implementation, comprehensive three-dimensional (3-D) lookup tables are presented. They enable the study of optimized filter parameter variations for a range of grid disturbances, and broaden the application to filter optimization in real-time. In the interest of the reader, this paper is structurally split into two parts. Part 1 covers the premise and theory that explicates the proposed SCM methodology. The detailed analysis and verification of the SCM are covered in Part 2. [ABSTRACT FROM AUTHOR]

Highlights: [•] A model for the electromechanical behaviour of ferroelectric polycrystals is proposed. [•] The approach is anhysteretic. [•] Hysteresis can be added afterwards to obtain typical butterfly loops. [•] Effects of crystallographic texture on the macroscopic response are investigated. [•] Internal stresses under electromechanical loadings are estimated. [Copyright &y& Elsevier]

Highlights: [•] The effect of the interlamellar spacing on pearlitic steel strength is studied. [•] Phase stresses are investigated using X-ray űin situƇ tensile tests. [•] Ferrite plasticity parameters are identified by the self consistent model. [•] The effect of the interlamellar spacing on residual stress is studied. [ABSTRACT FROM AUTHOR]

Abstract: Free-burning arcs where the work piece acts as an anode were numerically analyzed using a computational domain including the arc itself and its anode region based on the local thermodynamic equilibrium model. Because the major arc parameters such as temperature, axial velocity, electric potential difference and pressure-rise from ambient atmospheric pressure are much dependent on the working current, our investigation was concerned with developing a capability to model free-burning argon arcs and considering the energy flux going into the anode at various values of the electrical current (I =50, 100 and 200A) by computational fluid dynamics analysis. Predicted temperatures along the z-axis between the electrodes were in fair agreement with existing experimental results. Particularly, reasonable relationships between the maximum velocity or temperature and the applied current were predicted, which matched well with other theoretical results. In addition, some discrepancies with other predictions were shown in the results about electric potential and pressure-rise. It should be related to the omission of the space-charge effect near the electrodes for a simplified unified model and the application of a turbulence model for the steep temperature gradient at the arc edges. [Copyright &y& Elsevier]

Highlights: [•] We investigated the microstructure and mechanical properties of cold-drawn aluminium tubes. [•] We determined the contribution of the dislocation density to strength of deformed tubes. [•] We modeled the effects of grain size and strengthening contribution on the mechanical behavior of drawn tubes. [•] We identified the parameters of micromechanical model. [ABSTRACT FROM AUTHOR]

SUMMARY This paper presents a numerical strategy that allows to lower the costs associated to the prediction of the value of homogenized tensors in elliptic problems. This is performed by solving a coupled problem, in which the complex microstructure is confined to a small region and surrounded by a tentative homogenized medium. The characteristics of this homogenized medium are updated using a self-consistent approach and are shown to converge to the actual solution. The main feature of the coupling strategy is that it really couples the random microstructure with the deterministic homogenized model, and not one (deterministic) realization of the random medium with a homogenized model. The advantages of doing so are twofold: (a) the influence of the boundary conditions is significantly mitigated, and (b) the ergodicity of the random medium can be used in full through appropriate definition of the coupling operator. Both of these advantages imply that the resulting coupled problem is less expensive to solve, for a given bias, than the computation of homogenized tensor using classical approaches. Examples of 1-D and 2-D problems with continuous properties, as well as a 2-D matrix-inclusion problem, illustrate the effectiveness and potential of the method. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Interpenetrating phase composites can be defined as multiphase materials in which each phase is three-dimensionally interconnected throughout the structure. The unique geometry of the reinforcement offers improved combination of mechanical and physical properties. Over the years, a lot of efforts have been put to study these composites experimentally. However, due to the complexity in microstructure and randomness in behaviour of interpenetrating phase composite, the modelling of these composites has not been sufficiently studied so far. Therefore, in this study, two models, namely, unit cell and self-consistent models have been presented to find the elastic properties of interpenetrating phase composites. All influencing parameters such as volume fraction and random geometry are duly incorporated in these models. These models are analysed by a mesh-free method known as element-free Galerkin method. The effective properties of these composites are calculated by an effective medium approximation approach. The real microstructure of interpenetrating phase composites is partially interpenetrating and partially particulate in nature; hence, a control parameter has been included in the model to simulate this behaviour. The main feature of the proposed unit cell model is that it is easy to implement and less time consuming as compared to three-dimensional existing model and characterises all the governing features of interpenetrating phase composite microstructure. [ABSTRACT FROM AUTHOR]

A simplified nonincremental interaction law is used describing the nonlinear elastic-inelastic behavior of FCC polycrystals proposed recently (Abdul-Latif and Radi, 2010, "Modeling of the Grain Shape Effect on the Elastic-Inelastic Behavior of Polycrystals with Self-Consistent Scheme," ASME J. Eng. Mater. Technol., 132(1), p. 011008). In this scheme, the elastic strain defined at the granular level based on the Eshelby's tensor is assumed to be isotropic, uniform and compressible. Hence, the approach considers that the inclusion (grain) has an ellipsoidal shape of half axes defining by a, b and c such as a ≠ b = c. The granular heterogeneous inelastic strain is locally determined using the slip theory. Both elastic and inelastic granular strains depend on the granular aspect ratio (α = a/b). An aggregate of grains of ellipsoidal shape is supposed to be randomly distributed with a distribution of aspect ratios having a log-normal statistical function. The effect of this distribution on the mechanical behavior is investigated. A host of cyclic inelastic behavior of polycrystalline metals is predicted under uniaxial and multiaxial loading paths. Using the aluminum alloy 2024, an original complex cyclic loading path type is proposed and carried out experimentally. After the model parameters calibration, the elastic-inelastic cyclic behavior of this alloy is quantitatively described by the model. As a conclusion, the model can successfully describe the elasto-inelastic at the overall and local levels. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we describe a multiscale strategy that allows to couple stochastic and deterministic models. The transition condition enforced between the two models is weak, in the sense that it is based on volume coupling in space (rather than more classical boundary coupling) and on a volume/sample average in the random dimension. The paper then concentrates on the application of this weak coupling technique for the development of a new iterative method for the homogenization of random media. The technique is based on the coupling of the stochastic microstructure to a tentative homogenized medium, the parameters of which are initially chosen at will. Based on the results of the coupled simulation, for which Dirichlet or Neumann boundary conditions are posed at the boundary of the tentative homogenized medium, the parameters of the homogenized medium are then iteratively updated. An example shows the efficiency of the proposed approach compared to the classical KUBC and SUBC approaches in stochastic homogenization. [Copyright &y& Elsevier]

Abstract: The main goal of this work is to describe the evolution (expansion, translation, distortion and rotation) of the yield surface using a recent developed self-consistent model with small strains assumption. In fact, the ellipsoidal inclusion case in the simplified non-incremental interaction scheme has been developed by Abdul-Latif and Radi (2010) showing the dependency of the elasto-inelastic behavior of polycrystals on the grain shape. The concept of yield surface is very important for evaluating the material work-hardening behavior beyond the yield point. Hence, a particular attention is made on the description of initial and subsequent yield surfaces. To show the predictive abilities of this model, these surfaces are simulated and then evaluated as a model response for different values of key model parameters (such as the grain aspect ratio α = a/b where a and b are the half-axes of the grain and the viscous parameter γ) subjected to radial proportional loading. Then, the effect of the two parameters on these surfaces will be discussed. Subsequent yield surfaces showed different proportions of translation, expansion, distortion and rotation. Moreover, the influence of the pre-loading nature on the subsequent yield surface evolution and its rotation will be then examined under three different loading conditions of tension, torsion, and combined tension–torsion proportional loading path. Some granular responses for pre-selected grains are also illustrated and discussed. [Copyright &y& Elsevier]

In this paper, by creating a 3-D model of power-line equipment and lightning leader progression models, an alternate procedure for calculating the shielding failure rate (SFR) of transmission lines is presented. The stepping nature of lightning downward leader is modeled according to field observations with the use of discrete line charges approaching the earth. A simplified self-consistent model for an upward connecting leader is also adopted to find the position of lightning incidence to the transmission line. The required electric field in an environment is computed by using the charge simulation method. A comparison has been made between the SFR calculated by proposed method and the values calculated by conventional electrogeometrical model. In addition, different previously proposed incidence criteria are implemented and compared. Some comparisons are also made between the calculated SFR and available field data for selected overhead lines. [ABSTRACT FROM AUTHOR]

Abstract: Work-hardening behavior of single-phase steel and dual-phase steel which is made of hard martensite surrounded by soft ferrite is analyzed by using an elastoplastic crystal plasticity model in conjunction with the incremental self-consistent model. Two-stage loading paths consisting of uniaxial tension, unloading and subsequent uniaxial tension/compression for various directions are applied. Bauschinger effect and transitional re-yielding behavior, which depends on the direction of the second loading path, are predicted and analyzed with respect to the distribution of the residual resolved shear stresses within the material. These features, which are caused by the inhomogeneity of the residual stress field, are especially pronounced in the case of the dual-phase steel because of the strong mechanical contrast between ferrite and martensite phases. [Copyright &y& Elsevier]

Abstract: In this paper, we discuss results from the new viscoplastic non-linear intermediate ϕ-model for crystal plasticity. We used this viscoplastic ϕ-model in order to compute several properties and indicators directly connected to the formability of FCC polycrystalline metals. For instance, the yield locus, the Lankford coefficients and the typical FCC rolling texture component and their evolution during plastic deformation are computed. We also compare our results to those predicted by the tangent viscoplastic self-consistent model as well as those obtained by the upper and lower bounds (Taylor and Static). Results concerning FCC metals subjected to plane strain compression (commonly used for the approximation of the rolling process) are presented. As in the self-consistent scheme, the viscoplastic ϕ-model takes into account the strength of grains interactions. The influence of the grain interaction on predicted results is discussed. This analysis of the change in predicted results for different values of the parameter controlling the grain interaction strength (from a stiff to a more compliant interaction) shows that the results depend strongly on ϕ. [ABSTRACT FROM AUTHOR]

A self-consistent approach is used to estimate the internal stresses induced by moisture absorption in composite materials with a viscoelastic matrix and linear elastic fibers. A strong influence of the behavior of the viscoelastic matrix and humidity on the internal stresses in the structures at macroscopic and local scales is found to exist. [ABSTRACT FROM AUTHOR]