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Butt-welding Residual Stress of Heat Treatable Aluminum Alloys

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Journal of materials Science & Technology 2007年第2期23卷 217-222页

作者： c.m. cheng Department of Industrial Education National Taiwan Normal University Taipei Taiwan China　

This study, taking three types of aluminum alloys 2024-T351, 6061-T6 and 7075-T6 as experimental materials, conducted single V-groove GTAW （gas tungsten arc welding） butt-welding to analyze and c.m.are the magnitude and differences of residual stress in the three aluminum alloys at different single V-groove angles and in restrained or unrestrained conditions. The results show that the larger the grooving angle of butt joint, the higher the residual tensile stress. Too small grooving angle will lead to dramatic differences due to the amount of welding bead filler metal and pre-set joint geometry. Therefore, only an appropriate grooving angle can reduce residual stress. While welding, weldment in restrained condition will lead to a larger residual stress. Also, a residual stress will arise from the restraint position. The ultimate residual stress of weldment is determined by material yield strength at equilibrium temperature. The higher the yield strength at equilibrium temperature, the higher the material residual stress. Because of its larger thermal conductivity, aluminum alloy test spec.m.ns have small temperature differential. Therefore, the residual tensile stress of all materials is lower than their yield strength.

关键词： Residual stress Hole-drilling strain-gage method Aluminum alloy Single-V groove

SURFAcE FINITE ELEmENTS FOR PARABOlic EQUATIONS

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Journal of c.m.utational mathematics 2007年第4期25卷 385-407页

作者： G. Dziuk c.m. Elliott Abteilung für Angewandte mathematik University of Freiburg Hermann-Herder-Straβe 10 D-79104Freiburg i. BrGermany Department of mathematics University of Sussex Falmer Brighton BN1 9RF United Kingdom

In this article we define a surface finite element method （SFEm） for the numerical solution of parabolic partial differential equations on hypersurfaces F in R^n＋1. The key idea is based on the approximation of F by a polyhedral surface Гh consisting of a union of simplices （triangles for n = 2, intervals for n = 1） with vertices on Г. A finite element space of functions is then defined by taking the continuous functions on Гh which are linear affine on each simplex of the polygonal surface. We use surface gradients to define weak forms of elliptic operators and naturally generate weak formulations of elliptic and parabolic equations on Г. Our finite element method is applied to weak forms of the equations. The c.m.utation of the mass and element stiffness matrices are simple and straightforward. We give an example of error bounds in the case of semi-discretization in space for a fourth order linear problem. Numerical experiments are described for several linear and nonlinear partial differential equations. In particular the power of the method is demorrstrated by employing it to solve highly nonlinear second and fourth order problems such as surface Allen-cahn and cahn-Hilliard equations and surface level set equations for geodesic.m.an curvature flow.

关键词： Surface partial differential equations Surface finite element method Geodesic curvature Triangulated surface.

correlation between the rock mass properties and maximum horizontal stress:A case study of overcoring stress measurements

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International Journal of minerals,metallurgy and materials 2025年第1期32卷 39-48页

作者： Peng li meifeng cai Shengjun miao Yuan li Yu Wang Key Laboratory of ministry of Education for Efficient mining and Safety of metal mines University of Science and Technology BeijingBeijing 100083China State Key Laboratory of coal Resources and Safe mining China University of Mining and TechnologyXuzhou 221116China

Understanding the mechanical properties of the lithologies is crucial to accurately determine the horizontal stress *** investigate the correlation between the rock mass properties and maximum horizontal stress,the three-dimensional(3D)stress tensors at 89 measuring points determined using an improved overcoring technique in nine mines in china were adopted,a newly defined characteristic parameter c_(ERP)was proposed as an indicator for evaluating the structural properties of rock masses,and a fuzzy relation matrix was established using the information distribution *** results indicate that both the vertical stress and horizontal stress exhibit a good linear growth relationship with *** is no remarkable correlation between the elastic.m.dulus,Poisson's ratio and depth,and the distribution of data points is scattered and ***,there is no obvious relationship between the rock quality designation(RQD)and *** maximum horizontal stress σ_(H) is a function of rock properties,showing a certain linear relationship with the c_(ERP)at the same *** addition,the overall change trend of σ_(H) determined by the established fuzzy identification method is to increase with the increase of c_(ERP).The fuzzy identification method also demonstrates a relatively detailed local relationship betweenσ_H and c_(ERP),and the predicted curve rises in a fluctuating way,which is in accord well with the measured stress data.

关键词： overcoring stress measurements elastic.m.dulus Poisson's ratio rock quality designation maximum horizontal stress fuzzy identification

Integration of molecular genetic technology with quantitative genetic technology for maximizing the speed of genetic improvement

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华南农业大学学报 2005年第S1期26卷 104-117页

作者： Jack c.m. DEKKERS Department of Animal Science and center for Integrated Animal Genomics 239D Kildee Hall Iowa State University Ames IA 50011 USA

Interfacial Zn2+-solvation regulator towards reversible and stable Zn anode

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Journal of Energy chemistry 2025年第1期100卷 684-692页

作者： miao Zhou Xiongbin Luo Hang li Shan Guo Zhuang Tong Xiaotao Zhou Xu li Zhaohui Hou Shuquan liang Guozhao Fang college of mechanical Engineering Key Laboratory of Hunan Province for Advanced Carbon-based Functional Materials Hunan Institute of Science and Technology School of materials Science and Engineering Key Laboratory of Electronic Packaging and Advanced Functional Materials of Hunan Province Central South University college of materials and metallurgy Guizhou University National Energy metal Resources and New materials Key Laboratory Central South University

Aqueous zinc-ion batteries （AZIBs） are fundamentally challenged by the instability of the electrode/electrolyte interface,predominantly due to irreversible zinc （Zn） deposition and hydrogen ***,the intricate mechanisms behind the electrochemical discrepancies induced by interfacial Zn2+-solvation and deposition behavior demand c.m.rehensive *** molecules endowed with special functional groups （such as hydroxyl,carboxyl,etc.） have the potential to significantly optimize the solvation structure of Zn2+and regulate the interfacial electric double layer （EDL）.By increasing nucleation overpotential and decreasing interfacial free energy,these functional groups facilitate a lower critical nucleation radius,thereby forming an asymptotic nucleation model to promote uniform Zn ***,this study presents a pioneering approach by introducing trace amounts of n-butanol as solvation regulators to engineer the homogenized Zn （H-Zn） anode with a uniform and dense *** interfacial reaction and structure evolution are explored by in/ex-situ experimental techniques,indicating that the H-Zn anode exhibits dendrite-free growth,no by-products,and weak hydrogen evolution,in sharp contrast to the bare ***,the H-Zn anode achieves a remarkable Zn utilization rate of approximately 20% and simultaneously sustains a prolonged cycle life exceeding 500 ***,the H-Zn//NH4V4O10（NVO） full battery showcases exceptional cycle stability,retaining 95.04%capacity retention after 400 cycles at a large current density of 5 A *** study enlightens solvation-regulated additives to develop Zn anode with superior utilization efficiency and extended operational lifespan.

关键词： Aqueous zinc-ion batteries Interfacial reaction Asymptotic nucleation model Reversible and stable Zn anode

multiphase reaction spinning of high-temperature resistant weavable SiO_(2)-Kevlar hybrid aerogel fibers

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Nano Research 2025年第1期18卷 424-433页

作者： Yunna chen Wenlu Zhang Qingyang li Wenbin li chong He School of Textile Science and Engineering Wuhan Textile UniversityWuhan 430200China State Key Laboratory of New Textile materials and Advanced Processing Technologies Wuhan Textile UniversityWuhan 430200China

Advanced aerogel fibers possess numerousadvantages amalgamating the attributes of aerogels and fibermaterials, rendering them invaluable in the realm of thermalmanagement and regulation. However, the achievement ofrobust mechanical properties and increased temperaturestability is still a major challenge for the majority of aerogelfibers. Herein, SiO_(2)-Kevlar hybrid aerogel fibers with bioniccore-shell structure were prepared by reaction spinning andweaved into fabric. Kevlar nanowires dispersion is pumpedinto a bath c.m.rising a self-synthesized silica sol, whichfacilitates the hybridization of biphasic aerogels through thegel reaction. Precise control over the diameter (200-800 μm)and structure of the wet gel fibers was achieved throughmeticulous adjustment of the spinning solution c.m.osition and spinning parameters. Subsequent freeze-drying processfacilitates the formation of a core-shell hybrid structure, in which the SiO_(2) aerogel layer effectively encapsulate the Kevlaraerogel core fiber. Taking full advantage of the mechanical properties of the Kevlar core fiber, the resulting SiO_(2)-Kevlaraerogel fibers exhibit c.m.endable weaving characteristics (51.8 mPa). Furthermore, SiO_(2)-Kevlar aerogel fabrics exhibitenhanced thermal insulation characteristics with a thermal conductivity of 0.037 W/(m·K). As a result of the presence ofexternal SiO_(2) aerogel layer, the overall temperature resistance performance of the SiO_(2)-Kevlar fabric reach up to 700 ℃.

关键词： aerogel fibers SiO_(2)aerogel Kevlar aerogel reaction spinning thermal protective performance

litter production, dec.m.osition and nutrient mineralization dynamics of Ochlandra setigera: A rare bamboo species of Nilgiri Biosphere Reserve, India

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Journal of Forestry Research 2014年第3期25卷 579-584页

作者： Kuruvilla Thomas c.m. Jijeesh K.K. Seethalakshmi SFm Division Kerala Forest Research Institute Dept of Silviculture & Agroforestry College of Forestry

litter production, dec.m.osition and nutrient release dynam-ics of Ochlandra setigera, a rare endemic bamboo species of Nilgiri biosphere were studied during 2011-2012 using the standard litter bag technique. Annual litter production was 1.981 t？ha-1 and was continuous throughout the year with monthly variations. litterfall followed a tri-phasic pattern with two major peaks in November, 2011 and January, 2012 and a minor peak in July, 2011. The rate of dec.m.osition in O. setigera was a good fit to the exponential decay model of Olson （1963）. litter quality and climatic conditions of the study site （maximum tem-perature, monthly rainfall and relative humidity） influenced the rate of dec.m.osition. Nutrient release from the dec.m.osing litter mass was in rank order N=mg＆gt;K=ca＆gt;P. Nutrient release from litter was con-tinuous and it was in synchrony with growth of new culms. Study of litter dynamics is needed before introduction of a bamboo species into degraded or marginal lands or Agroforestry systems.

关键词： Ochlandra setigera litter fall litter dec.m.osition nutrientrelease dec.m.osition rate

Hot cracking in AZ31 and AZ61 magnesium Alloy

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Journal of materials Science & Technology 2011年第7期27卷 633-640页

作者： c.J. Huang c.m. cheng c.P. chou F.H. chen Department of mechanical Engineering National Chiao Tung University Hsinchu 300 Taiwan China Department of Industrial Education National Taiwan Normal University Taipei 106 Taiwan China

This paper examined the impact of the number of thermal cycles and augmented strain on hot cracking in AZ31 and AZ61 magnesium alloy. Statistical analyses were performed. Following observation using a scanning electron microscope （SEm）, an energy dispersive spectrometer （EDS） was used for c.m.onent analysis. Results showed that Al content in magnesium alloy has an effect on hot cracking susceptibility. In addition, the nonequilibrium solidification process produced segregation in Al content, causing higher liquid mg-alloy rich Al content at grain boundaries, and resulting into liquefied grain boundaries of partially melted zone （PmZ）. In summary, under multiple thermal cycles AZ61 produced serious liquation cracking. AZ61 has higher （6 wt%） Al content and produced much liquefied mg17Al12 at grain boundaries under multiple thermal cycles. The liquefied mg17Al12 were pulled apart and hot cracks formed at weld metal HAZ due to the augmented strain. Since AZ31 had half the Al content of AZ61, its hot-cracking susceptibility was lower than AZ61. In addition, AZ61 showed longer total crack length （TcL） in one thermal cycle c.m.ared to that in three thermal cycles. This phenomenon was possibly due to high-temperature gasification of Al during the welding process, which resulted in lower overall Al content. consequently, shorter hot cracks exhibited in three thermal cycles. It was found the Al content of AZ31 and AZ61 can be used to assess the hot-cracking susceptibility.

关键词： Varestraint test Thermal cycles Hot-cracking susceptibility Gas tungsten arc welding (GTAW) AZ31 AZ61

microstructural evolution during the progressive transformation-induced plasticity effect in a Fe-0.1c-5mnmedium manganese steel

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International Journal of minerals,metallurgy and materials 2025年第2期32卷 369-379页

作者： mei Zhang Wenhao li Yangfei chen Yang Jiang Xiaofei Guo Han Dong School of materials Science and Engineering Shanghai UniversityShanghai 200444China State Key Laboratory of Advanced Special Steel Shanghai UniversityShanghai 200444China

The microstructural evolution of a cold-rolled and intercritical annealed medium-mn steel(Fe-0.10c-5mn)was investigated during uniaxial tensile ***-situ observations under scanning electron microscopy,transmission electron microscopy,and X-ray diffraction analysis were conducted to characterize the progressive transformation-induced plasticity process and associated fracture initiation *** findings were discussed with the local strain measurements via digital image *** results indicated that Lüders band formation in the steel was limited to 1.5%strain,which was mainly due to the early-stage martensitic phase transformation of a very small amount of the less stable large-sized retained austenite(RA),which led to localized stress concentrations and strain hardening and further retardation of *** small-sized RA exhibited high stability and progressively transformed into martensite and contributed to a stably extended Portevin-Le chatelier *** volume fraction of RA gradually decreased from 26.8%to 8.2%prior to *** the late deformation stage,fracture initiation primarily occurred at the austenite/martensite and ferrite/martensite interfaces and the ferrite phase.

关键词： medium-mn steel retained austenite progressive transformation-induced plasticity effect local strain fracture initiation