基于自适应双相场模型的纤维增强复合材料单层板断裂性能

相场法可以自动捕捉裂纹的萌生和演化,因此在模拟复合材料的复杂失效行为时具有明显优势。为区分纤维增强复合材料(Fiber-reinforced composites,FRC)中存在的不同断裂模式,采用双相场断裂模型来分别表征基体和纤维的损伤演化。同时采用相场变量作为误差指标,在各向异性的双相场模型中引入了基于四叉树分解的网格自适应细化策略。设计并开发了相应的Matlab程序,研究了单向及变刚度纤维增强复合材料单层板在拉伸位移载荷下的断裂行为。计算结果表明:采用基于自适应算法的各向异性双相场模型所得到的数值计算结果与试验结果吻合良好;自适应双相场模型能在保证较高计算精度的同时,配合序参量的演化准确地在裂纹路径上进行网格自动加密,简化网格前处理过程,减少网格数量,降低计算成本,提高计算效率。

Simulation and Analysis on the Two-Phase Flow Fields in a Rotating-Stream-Tray Absorber by Using Computational Fluid Dynamics

The flow field of gas and liquid in a φ150mm rotating-stream-tray (RST) scrubber is simulated by using computational fluid dynamic (CFD) method. The sismulation is based on the two-equation RNG κ-ε turbulence model, Eulerian multiphase model, and a real-shape 3D model with a huge number of meshes. The simulation results include detailed information about velocity, pressure, volume fraction and so on. Some features of the flow field are obtained: liquid is atomized in a thin annular zone; a high velocity air zone prevents water drops at the bottom from flying towards the wall; the pressure varies sharply at the end of blades and so on. The results will be helpful for structure optimization and engineering design.

Entanglement for a Bimodal Cavity Field Interacting with a Two-Level Atom

Negativity has been adopted to investigate the entanglement in a system composed of a two-level atom anda two-mode cavity field.Effects of Kerr-like medium and the number of photon inside the cavity on the entanglementare studied.Our results show that atomic initial state must be superposed,so that the two cavity field modes can beentangled.Moreover,we also conclude that the number of photon in the two cavity mode should be equal.The interactionbetween modes,namely,the Kerr effect,has a significant negative contribution.Note that the atom frequency and thecavity frequency have an indistinguishable effect,so a corresponding approximation has been made in this article.Theseresults may be useful for quantum information in optics systems.

Evolution of Two Non-identical Two-Level Atoms in Two-Mode Cavity Fields

In this paper, we investigate the evolution of two non-identical two-level atoms in two-mode cavity fields. We demonstrate the death and rebirth effect of entanglement for two non-identical two-level atoms under some initial conditions. It is also exemplified that entangled states of two nonidentical two-level atoms can be generated by entangled two-mode cavity fields. This research can be considered as a first step to further investigate the problem of manipulating two nonidentical two-level atoms in two-mode cavity fields.

Influence of Bipartite Qubit Coupling on Geometric Phase

The geometric phase of the bipartite Heisenberg spin-1/2 system with one spin driven by rotating magnetic field is investigated. It is found that in the one-site drive case, the intersubsystem coupling can be equivalent to a static quasi-magnetic field in the parameter space. This perspective has satisfactorily explained the irregular asymptote effect of geometric phase. We discuss the property of the two-site magnetic drive spin system and discover that a stationary state with no geometric phase shift is generated.

The Exact Solution of MJilburn Equation Without Diffusion Approximation for the Two—Model Raman Coupled Model

By making use of the dynamical algebraic approach, we study the two-mode Raman coupled model governed by the Milburn equation and find the exact solution of the Milburn equation without diffusion approximation. The exact solution is then used to discuss the influence of intrinsic decoherence on the revivals of atomic inversion, oscillation of the photon number distribution and squeezing of radiation field in the whole ranges of the decoherence parameter .

Coherence-Enhanced Entanglement Induced by a Two-Mode Thermal Field

Considering two identical two-level atoms interacting with two mode thermal field through a nondegeratetwo-photon process,we study the entanglement dynamics between two atoms when the atomic coherence exists.It showsthat the entanglement is dependent on the initial atomic states,and is greatly enhanced due to atomic coherence ascompared with the case when the atomic coherence is ignored.The results also show that the entanglement can becontrolled by changing the relative phases and the amplitudes of the polarized atoms.

Influence of Hyperon-Hyperon Interaction on Properties of Hadronic Star

The influences of hyperon-hyperon interaction on the overall properties of hadronic star are investigated in the framework of relativistic mean field （RMF） theory. For certain hyperon coupling, the weaker hyperon-hyperon interaction can lead to the heavier hadronic star, which accords with the observation of heavy neutron star in X-ray binaries. We find that the threshold densities of the hyperons with larger masses are brought to a lower values with the increase of the hyperon-hyperon interaction. The possibility of the existence of hyperon star is checked with the consideration of hyperon-hyperon interaction.

Bimodal plate structures induced by pulsed laser in duplex-phase Zr alloy

A duplex-phase Zr-2.5Nb alloy was treated by pulsed laser, followed by careful microstructural characterization using field emission gun scanning electron microscope and attached electron backscatter diffraction. Beneath the modification zones with common uniform α-plate structures(UPS), a layer of unreported bimodal α-plate structures(BPS) featured by coarse(submicron)plates forming multiple cores surrounded by dense fine(nanoscale) plates was found. Presence of such BPS is attributed to non-equilibrium thermodynamic conditions induced by the pulsed laser treatments. Limited diffusion of Nb due to the short pulse during laser heating allows β phases with distinctly different Nb contents to be presented: Nb-enriched prior β films and Nb-depleted β phases, transforming into the fine and the coarse plates during cooling, respectively. Orientation analyses show that both types of plates in the BPS are aroused essentially from a single β orientation, suggesting epitaxial growth of the Nb-depletedβ phases from the preexisting β films.

In-situ investigation on the fatigue crack propagation behavior in ferrite-pearlite and dual-phase ferrite-bainite low carbon steels

The purpose of this study was to describe the roles of microstructure types and grain boundary characteristics in fatigue crack propagation behavior in ferrite-pearlite steel and ferrite-bainite steel.The ferrite-bainite dual-phase steel was obtained by intermediate heat treatment conducted on ferrite-pearlite low carbon steel.This paper presents the results from investigation using constant stress-controlled fatigue tests with in-situ scanning electron microscopy(SEM),electron backscattering diffraction(EBSD) and fatigue fractography analysis.Microscopic images arrested by in-situ SEM showed that the second hard bainite phase distributed in the soft ferrite matrix had a significant effect on preventing the cracks opening compared with pearlite,and that the cracks in ferrite-bainite steel were "locked" in the second hard bainite phase while the crack propagation path in ferrite-pearlite steel was more tortuous.Moreover,the fatigue fracture surface analysis and the coincidence site lattice(CSL) obtained by EBSD indicated that low-CSL grain boundaries in ferrite-bainite steel distributed more uniformly,which has a more significant effect on the resistance of crack propagation.It was revealed that ferrite-bainite dual-phase microstructures could inhibit the fatigue crack propagation more effectively than ferrite-pearlite microstructures.

Deformation study of bicrystalline and nano-polycrystalline structures using phase field crystal method

Deformation behaviors of bicrystalline and nano-polycrystalline structures of various tilt angles and inclination angles in two dimensions are investigated in detail using a two-mode phase field crystal model.The interaction between grain boundary(GB)and dislocation is also examined in bicrystals and nano-polycrystals that both contain asymmetric and symmetric tilt GBs,with energy analysis being carried out to analyze these processes.During deformation simulations,we assume the volume of each simulation cell at every time step is coincident with that of the initial state just before deformation.Our simulation results show that the behaviors of symmetric and asymmetric GBs in bicrystals and nano-polycrystals differ from each other depending on tilt angle and inclination angle.A new dislocation emission mechanism of interest is observed in bicrystals which contain low angle symmetric tilt GBs.Low angle GB has a higher mobility relative to high angle GB in both bicrystalline and nano-polycrystalline structures,as does asymmetric GB to symmetric GB.The generation,motion,pileup and annihilation of dislocations,grain rotation and grain coalescence are observed,which is consistent with the simulation results obtained by molecular dynamics.These simulation results can provide strong guidelines for experimentation.