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unit-cell design for two-dimensional phase-field simulation of microstructure evolution in single-crystal Ni-based superalloys during solidification

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Progress in Natural Science:Materials International 2017年第6期27卷 678-686页

作者： Dongjia Cao Na Ta Lijun Zhang State Key Lab of Powder Metallurgy Central South University Interdisciplinary Centre for Advanced Materials Simulation (ICAMS) Ruhr-University Bochum

Phase-field simulation serves as an effective tool for quantitative characterization of microstructure evolution in single-crystal Ni-based superalloys during solidification nowadays. The classic unit cell is either limited to γdendrites along crystal orientation or too ideal to cover complex morphologies for γ dendrites. An attempt to design the unit cell for two-dimensional(2-D) phase-field simulations of microstructure evolution in single-crystal Ni-based superalloys during solidification was thus performed by using the MICRESS(MICRostructure Evolution Simulation Software) in the framework of the multi-phase-field(MPF) model,and demonstrated in a commercial TMS-113 superalloy. The coupling to CALPHAD(CALculation of PHAse Diagram) thermodynamic database was realized via the TQ interface and the experimental diffusion coefficients were utilized in the simulation. Firstly, the classic unit cell with a single γ dendrite along crystal orientation was employed for the phase-field simulation in order to reproduce the microstructure ***, such simple unit cell was extended into the cases with two other different crystal orientations, i.e., and . Thirdly, for crystal orientations, the effect of γ dendritic orientations and unit cell sizes on microstructure and microsegregation was comprehensively studied, from which a new unit cell with multiple γdendrites was proposed. The phase-field simulation with the newly proposed unit cell was further performed in the TMS-113 superalloy, and the microstructure features including the competitive growth of γ dendrites,microsegregation of different solutes and distribution of γ′ grains, can be nicely reproduced.

关键词： Ni-based superalloys Solidification Microstructure Phase-field simulation unit cell

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Meso-Scale Modeling for Effective Properties in Continuous Fiber-Reinforced Composites by State-Based Peridynamics

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Acta Mechanica Solida Sinica 2021年第5期34卷 729-742页

作者： Xiang Li Yin Yu Zhongcheng Mu Y.L.Hu Aerospace Structure Research Center School of Aeronautics and AstronauticsShanghai Jiao Tong UniversityShanghai200240China School of Aeronautics and Astronautics Shanghai Jiao Tong UniversityShanghai200240China

This study demonstrates a homogenization approach via a modified state-based peridynamic(PD)method to predict the effective elastic properties of composite materials with periodic *** procedure of modeling the PD unit cell(UC)of continuous fiber-reinforced composite is *** boundary conditions are derived and implemented through the Lagrange multiplier method.A matrix-dominated approach for modeling the interphase properties between dissimilar materials is *** periodicity and continuity assumptions are employed to determine the stress and strain fields,as well as the effective elastic *** PD-UCs of square and hexagonal packs as well as the 0/90 laminate microstructure are modeled and compared with the analytical,numerical and experimental results from the *** agreement of predicted effective properties can be *** other PD homogenization approaches,the effective material properties can be directly and individually obtained from simple loading conditions.

关键词： State-based peridynamics Composites Meso-scale unit cell Homogenization

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NUMERICAL STUDY ON CREEP DAMAGE OF COMPOSITES AT HIGH TEMPERATURE

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Acta Metallurgica Sinica(English Letters) 2004年第4期17卷 493-497页

作者： Y.P.Jiang Z.F.Yue School of Mechanics Civil Engineering and Architecture Northwestern Polytechnic University Xi'an710072 ChinaSchool of Mechanics Civil Engineering and Architecture Northwestern Polytechnic University Xi'an710072 China

A unit cell model is applied to study the creep damage behavior after fiber fractures in the fiber-reinforced composites at high temperature. The user subroutine CREEP has been programmed for ABAQUS. The fiber breakage results in a new crack. The results show that the stress concentration factor resulted from the fiber breakage increases with the creep time. The creep damage takes place near the crack, and then grows in the matrix along a certain angle, up to the total failure. The influences of the ratio of modulus of the fiber to the matrix (Ef/Em) on the creep deformation, damage and stress distributions have been studied. With the increasing Ef/Em, the damage in the matrix increases. Analysis on the different ductility of matrix shows that the creep damage of low ductile matrix composites is higher than high ductile matrix composites.

关键词： composites creep damage unit cell finite element method

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Underwater cylindrical sandwich meta-structures composed of graded semi re-entrant zero Poisson’s ratio metamaterials with pre-strained wave propagation properties

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Journal of Ocean Engineering and Science 2024年第6期9卷 541-553页

作者： Qing Li Zeping Wang Xiang Mao Deqing Yang State Key Laboratory of Ocean Engineering School of Naval ArchitectureOcean and Civil EngineeringShanghai Jiao Tong UniversityShanghai 200240China College of Shipbuilding Engineering Harbin Engineering UniversityHarbin 150001China Qingdao Innovation and Development Center of Harbin Engineering University Qingdao 266000China SJTU Yazhou Bay Institute of Deepsea SCI-TECH Sanya 572024China

Zero Poisson’s ratio(ZPR)mechanical metamaterials can yield no transverse displacements when unidi-rectionally compressed,and cylindrical sandwich meta-structures composed of semi re-entrant(SRE)ZPR metamaterials are thus explored for applications on cylindrical shells of underwater equipment or sub-mersible structures.A group of ZPR unit cells with specified pre-strained wave propagation characteristics and adequate load-bearing capabilities is optimally designed based on the periodic boundary condition(PBC)and Bloch’s *** sound transmission and pressure-resistant performance of cylindrical sandwich meta-structures comprising the homogeneous and graded SRE ZPR unit cells are then *** results show that the designed meta-structures can perfectly yield better vibroacoustic atten-uation behavior within the specified frequency regions corresponding to the pre-strained band gaps and safely bear the hydrostatic pressure equivalent to 1000 m depth with low weight-bulk *** addition,the functionally graded metamaterial core can boost vibroacoustic performance within broader frequency ranges.

关键词： Cylindrical sandwich meta-structure Zero Poisson’s ratio unit cell Pre-strained Wave propagation Pressure-resistant

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Synthesis and Characterization of Ce-Containing MCM-41

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Chemical Research in Chinese Universities 2001年第Z1期17卷 200-201页

作者： CHIEN ShuHua Institute of Chemistry 4cademia Sinica Taipei 115 ChinaDepartment of Chemistry National Taiwan University

SUMMARY. The cerium-containing MCM-41 (Ce-MCM-41) has been synthesized with size in the micrometer range by direct hydrothermal method. Transmission electron microscopy shows the regular hexagonal array of uniform channel characteristics of MCM-41. Five peaks were detected in the lov-angle XRD patterns,an interplanar spacing d100 = 40.6 A was obtained that can be indexed on a hexagonal unit cell with a0 = 46.9 A. Nitrogen adsorption isotherm at 77 K revealed a surface area of 920 m2/g, pore size of 26.2 A and wall thickness of 18.1 A. A cell contraction of 2.6 A upon calcination was observed. The spectroscopic studies indicate that the synthesized sample is with MCM-41 structure and Ce is in the framework position. A weak Lewis acidity was indicated by infrared spectra of pyridine adsorption. The synthesized Ce-MCM-41 exhibits fairly catalytic activity for the NO reduction by CO.

关键词： spectroscopic studies hydrothermal method electron microscopy adsorption isotherm catalytic activity infrared spectra cell contraction wall thickness Lewis acidity surface area NO reduction unit cell

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Microstructure Analysis of 4-Step Three-Dimensional Braided Composite

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Chinese Journal of Aeronautics 2003年第3期16卷 142-150页

作者：郑锡涛叶天麒 Aircraft Department

The yarn architecture of 3-D braided composites products by the four-step 1×1 braiding technique has been studied by means of a control volume method in conjunction with experimental investigation and a numerical method, respectively. An ellipse assumption for the cross-section of yarn was proposed in this analysis method with considering the yarn size and yarn-packing factor. Two types of local unit cell structures were identified for 4-step braided composites by considering the nature of the braiding processes and by observing the sample cross-sections. The relationship between the braiding procedure and the properties for 3-D braided structural shapes was established. This method provides the basis for analyzing stiffness and strength of 3-D braided composites.

关键词： composites 3-D braided fabrics unit cell microstructure packing factor

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INCLINED LAMINAL COMBINATION MODEL OF 3D BRAIDED COMPOSITES

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Transactions of Nanjing University of Aeronautics and Astronautics 1995年第1期12卷 8-14页

作者：周光明王鑫伟乔新南京航空航天大学飞行器系

As an advanced composite material, the 3D braided composite has received more and more attention in foreign countries. However, it has received less attention in China. The geometric unit cell which can describe the basic structure and the relationship between the braiding angle and geometric parameters of the fabric and fiber volume ratio are given in this paper based on two 3D braiding processes, namely, the four-step and the twostep ones. Several existing mechanical models to predict groperties of the 3D braided comPOsites are discussed and their shortcomings are pointed out herein. Then a new model called the inclined laminal combination model is proposed, which is based on the classical laminated plate theory and can predict the basic mechanical behavior of the two 3D braided composites with four-step or two-step braid. In the model, each yarn in the unit cell is regarded as an inclined laminate and then a 3D analysis is performed. It is found that the predicted mechanical properties of the 3D braided composites by the proposed model are compared well with the experimental data.

关键词： composites mechanical properties unit cell mechanical model 3D braided

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