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Fatigue crack propagation across grain boundary of Al-Cu-Mg bicrystal based on crystal plasticity XFEM and cohesive zone model

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Journal of Materials Science & Technology 2022年第31期126卷 275-287页

作者： Qi Zhao Magd Abdel Wahab Yong Ling zhiyi liu School of Materials Science and Engineering Hubei University of Automotive TechnologyShiyan 442002China Faculty of Mechanical-Electrical and Computer Engineering School of Engineering and TechnologyVan Lang UniversityHo Chi Minh CityVietnam Soete Laboratory Faculty of Engineering and ArchitectureGhent UniversityTechnologiepark Zwijnaarde 903B-9052 ZwijnaardeBelgium School of Materials Science and Engineering Central South UniversityChangsha 410083China

In this paper,a methodology integrating crystal plasticity(CP),the eXtended finite element method(XFEM)and the cohesive zone model(CZM)is developed for an Al-Cu-Mg alloy to predict fatigue crack propagation(FCP)across grain boundary(GB)of Al-Cu-Mg alloy during stageІІ.One GB model is incor-porated into FCP constitutive law to describe grain interaction at GB.A bicrystal containing GB is built up to simulate FCP behavior through L participated *** features including GB characteristic,cumulative plastic strain(CPS)distribution and crystal slipping evidence can be *** numer-ical results are compared with published experimental data to check the accuracy of *** work demonstrates that the combination of CP containing GB constitutive laws,XFEM and CZM is a promising methodology in predicting twist angle-controlled crack deflection through GBs.

关键词： Grain boundary Twist angle Crystal plasticity Extended finite element method Fatigue crack propagation Cumulative plastic strain

Wall slip behavior of cemented paste backfill slurry during pipeline based on noncontact experimental detection

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International Journal of Minerals,Metallurgy and Materials 2023年第8期30卷 1515-1523页

作者： Zhenlin Xue Haikuan Sun Deqing Gan Zepeng Yan zhiyi liu School of Mining Engineering North China University of Science and TechnologyTangshan 063200China Mining Development and Safety Technology Key Lab of Hebei Province Tangshan 063009China School of Civil and Resources Engineering University of Science and Technology BeijingBeijing 100083China

Wall slip is a microscopic phenomenon of cemented paste backfill(CPB)slurry near the pipe wall,which has an important influence on the form of slurry pipe transport flow and velocity *** probing the wall slip characteristics using conventional experimental methods is ***,this paper established a noncontact experimental platform for monitoring the microscopic slip layer of CPB pipeline transport independently based on particle image velocimetry(PIV)and analyzed the effects of slurry temperature,pipe diameter,solid concentration,and slurry flow on the wall slip velocity of the CPB slurry,which refined the theory of the effect of wall slip characteristics on pipeline *** results showed that the CPB slurry had an extensive slip layer at the pipe wall with significant wall *** slurry temperature improved the degree of particle Brownian motion within the slurry and enhanced the wall slip *** the pipe diameter was not conducive to the formation of the slurry slip layer and led to a transition in the CPB slurry flow *** increase in the solid concentration raised the interlayer shear effect of CPB slurry flow and the slip *** slip velocity value increased from 0.025 to 0.056 m·s^(-1)when the solid content improved from 55wt%to 65wt%.When slurry flow increased,the CPB slurry flocculation structure changed,which affected the slip velocity,and the best effect of slip layer resistance reduction was achieved when the transported flow rate was 1.01 m^(3)·h^(-1).The results had important theoretical significance for improving the stability and economy of the CPB slurry in the pipeline.

关键词： particle image velocimetry cemented paste backfill noncontact experimental platform wall slip behavior pipeline transportation

Influence of temperature on the transformation and self-control of energy during sandstone damage:Experimental and theoretical research

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International Journal of Mining Science and Technology 2022年第4期32卷 761-777页

作者： Lan Qiao Jiawang Hao zhiyi liu Qingwen Li Naifu Deng Beijing Key Laboratory of Urban Underground Space Engineering University of Science and Technology BeijingBeijing 100083China School of Mining Engineering North China University of Science and TechnologyTangshan 063210China

The surrounding rock in tunnelling engineering and coal mining will sometimes be exposed to high temperature. Rock failure is the result of energy dissipation, and the study of the evolution and transformation behavior of energy is of great significance for the in-depth understanding of the deformation and failure of rock after high temperature. This study analyzed the intrinsic connection between mechanical properties and acoustic emission(AE) energy under temperature effect. Based on the energy dissipation and release theory, the distribution and transformation of energy was analyzed, and the energy selfincentive and self-inhibition(EII) model was further established. The main findings are that temperature effect affects the confidence interval trend and the value of AE energy rate, which is related to the change in mechanical properties. The ability of sandstone to store elastic strain energy after exposure to high temperature is independent of the mechanical properties. In this study, the ratio of dissipated energy to elastic energy is used to characterize the stable state of the sandstone system, which can be used as the energy indicator of rock failure precursor. During the absorption, storage, and release of energy before the peak stress, there exists self-incentive and self-inhibition of energy(control behavior).

关键词： Exposure to high temperature Rock failure Energy behavior Energy indicator Self-control of energy

Fatigue Behavior of a Dissimilar Aluminum Alloy Welding Joint With and Without Natural Defect

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Journal of Wuhan University of Technology(Materials Science) 2022年第5期37卷 1000-1008页

作者： SHI Liang WANG Chiquan liu zhiyi WANG Juntao WANG Wukun China Aero-Polytechnology Establishment Beijing100028China Kunming Precision Machinery Research Institute Kunming650118China

In order to investigate the influence of natural defect on the fatigue behavior of 5A06/7A05 dissimilar aluminum alloys welding joint,fatigue tests of two types of specimens with and without defects were carried out systematically under stress amplitude control conditions (stress ratio R=0.1) at normal temperature in laboratory air ***,a new parameter,i e,fatigue defect effect factor (FDEF) was introduced to assess the effect of defect on fatigue *** fatigue failure analysis was conducted as well to compare the fatigue and fracture behavior of the two types of *** results show that:(1) natural defects have a strong effect on the fatigue lives of welding joint,and the differences between the specimens with and without defects can reach 80 times under a same theoretical net sectional stress;(2) the FDEF parameter introduced is effective to deal with the defect effect,and the FDEF decreases along with the increase of fatigue *** mean relative error between the experimental data and predicted fatigue strength based on the FDEF is 10.2%;(3) the macro fracture of both types of specimens have three typical zones,i e,fatigue source zone,crack propagation zone and final fracture zone,while there are more than one fatigue sources for specimens with natural *** overall pattern of crack propagation zone and fracture zone are quite similar,but the morphologies are different in details.

关键词： aluminum alloys welding joint natural defect fatigue life scanning electron microscope(SEM)

Foreign gene transfer into Chinese shrimps (Penaeus chinensis) with gene gun

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Chinese Science Bulletin 2001年第9期46卷 766-770,794页

作者： liu zhiyi XIANG Jianhai ZHOU Guoying GONG Zuxun Experimental Marine Biology Laboratory Institute of OceanologyChinese Academy of SciencesQingdao 266071China Shanghai Institute of Biochemistry Chinese Academy of SciencesShanghai 200031China

Plasmids pG DNA-RZ1 with a GFP (green fluorescent protein) reporter gene and a ribozyme gene incising penaeid white spot baculovirus (WSBV) were first introduced into the fertilized eggs of Chinese shrimps by gene gun. The treated and control samples of different development stages were observed with a fluorescent microscope. The transient expression of GFP gene was high in nauplius and zoea larvae. Results from RT-PCR and PCR for adults showed that the foreign genes had been transferred into the shrimps and had expressed the corresponding proteins. This work has established a transgenic method for penaeid shrimps, which will set base for the application of genetic engineering breeding into industry.

关键词： gene gun GFP transgenic shrimps.

EFFECTS　OF　THREE　DIMENSIONAL　DIRECTION　OF　SECOND　DENDRITE　ON　COMPETITIVE　GRAIN　GROWTH　IN　DD8　SUPERALLOY

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中国有色金属学会会刊：英文版 1996年第2期6卷 111-116页

作者： liu zhiyi Wei Pengyi Fu Hengzhi(State Key Lab of Solidification Processing,Northwestern Polytechnical University , Xi′an 710072) State Key Lab. of Solidification Processing Northwestern Polytechnical University Xi'an 710072 China

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关键词： second dendrite nickel base superalloy three dimensional direction competitive grain growth

Existing form and effect of zirconium in pure Mg,Mg-Yb,and Mg-Zn-Yb alloys

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Rare Metals 2009年第3期28卷 289-296页

作者： YU Wenbin HE Hong LI Chunmei LI Qing liu zhiyi QIN Bing School of Materials Science and Engineering Southwest University Chongqing 400715 China School of Materials Science and Engineering Central South University Changsha 410083 China

The existing form and grain refining effects of small zirconium addition in pure Mg, Mg-Yb and Mg-Zn binary alloys, and Mg-Zn-Yb ternary alloy （ZK60-Yb） were investigated. The results show that Zr element exists mainly in single and cluster particles of pure α-Zr or Zn-Zr compounds inside grains and at grain boundaries. Only the particles located in the interior of grains can act as the nucleus for α-Mg growth and effectively promote the formation of fine equiaxed grains. The broken and dispersed Zr-rich particles produced during the hot extrusion process can form nebulous banded structure in which these fine particles may act as obstacles to dislocation motion in wrought magnesium alloys.

关键词： magnesium alloys zirconium grain refinement microstructure ytterbium

Constrained polynomial fit-based k-domain interpolation in swept-source optical coherence tomography

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Journal of Innovative Optical Health Sciences 2021年第1期4卷 83-90页

作者： Tao Han Jianrong Qiu Di Wang Jia Meng zhiyi liu Zhihua Ding State Key Lab of Modern Optical Instrumentation College of Optical Science and Engineering Zhejiang University Hangzhou 310027P.R.China

We propose a k-domain spline interpolation method with constrained polynomial fit based on spectral phase in swept-source optical coherence tomography(SS-OCT).A Mach-Zehnder interferometer(MZI)unit is connected *** swept-source of the SS-OCT system to generate calibration signal in sync with the fetching of interference *** spectral phase of the calibration signal is extracted by Hilbert *** fitted phase-time relationship is obtained by polynomial fitting with the constraint of passing through the central spectral *** fitting curve is then adopted for k-domain uniform interpolation based on evenly spaced *** comparison with conventional k-domain spline interpolation,the proposed method leads to improved axial resolution and peak response of the axial point spread function(PSF)of the SS-OCT *** performance resulting from the proposed method is further verified by OCT imaging of a home-constructed microspheres-agar sample and a fresh *** SS-OCT,the proposed method is believed to be applicable to spectral domain OCT as well.

关键词： Optical coherence tomography interpolation constrained polynomial fit

One-step scalable preparation of N-doped nanoporous carbon as a high-performance electrocatalyst for the oxygen reduction reaction

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Nano Research 2013年第4期6卷 293-301页

作者： Zhenyu liu Guoxin Zhang zhiyi Lu Xiuyan Jin Zheng Chang Xiaoming Sun State Key Laboratory of Chemical Resource Engineering P. O. Box 98 Beijing University of Chemical Technology Beijing 100029 China

N-doped porous carbon materials have been prepared by a simple one-step pyrolysis of ethylenediaminetetraacetic acid （EDTA） and melamine in the presence of KOH and Co（NO3）2·6H20. The combination of the high specific area （1,485 m2.g-l）, high nitrogen content （10.8%） and suitable graphitic degree results in catalysts exhibiting high activity （with onset and half-wave potentials of 0.88 and 0.79 V vs the reversible hydrogen electrode （RHE）, respectively） and four-electron selectivity for the oxygen reduction reaction （ORR） in alkaline medium---comparable to a commercial Pt/C catalyst, but far exceeding Pt/C in stability and durability. Owing to their superb ORR performance, low cost and facile preparation, the catalysts have great potential applications in fuel cells, metal-air batteries, and ORR-related electrochemical industries.

关键词： oxygen reductionreaction nitrogen-doping porous carbon