检索结果-南通市图书馆

journal of Magnesium and Alloys 2021年第4期9卷 1311-1335页

作者： A.r.Eivani h.Vafaeenezhad h.r.jafarian j.Zhou School of metallurgy and materials engineering iran university of science and technology^nartnaktehraniran department of biomechanical engineering delft university of technologymekehveg 22628 cd delftthe netherlands

The faults in welding design and process every so often yield defective parts during friction stir welding(FSW).The development of numerical approaches including the finite element method(FEM)provides a way to draw a process paradigm before any physical *** is not practical to simulate all possible designs to identify the optimal FSW practice due to the inefficiency associated with concurrent modeling of material flow and heat dissipation throughout the *** study intends to develop a computational workflow based on the mesh-free FEM framework named smoothed particle hydrodynamics(SPh)which was integrated with adaptive neuro-fiizzy inference system(ANFIS)to evaluate the residual stress in the FSW *** integrated SPh and ANFIS methodology was established and the well-trained ANIS was then used to predict how the FSW process depends on its *** verify the SPh calculation,an itemized FSW case was performed on AZ91 Mg alloy and the induced residual stress was measured by ultrasonic *** suggested methodology can efficiently predict the residual stress distribution throughout friction stir welding of AZ91 alloy.

关键词： Friction stir welding(FSW) Smoothed particle hydrodynamics(SPh) Adaptive neuro-fuzzy inference system(ANFIS) Ultrasonic residual stress

MODIFICATION OF SODIUM SALT OF PArTIALLY CArBOXYMEThYLATED TAMArIND KErNEL POWDEr ThrOUGh GrAFTING WITh ACrYLONITrILE: SYNThESIS, ChArACTErIZATION AND SWELLING BEhAVIOr

在线全文

学校读者我要写书评

暂无评论

Chinese journal of Polymer Science 2013年第12期31卷 1670-1684页

作者： j.h.Trivedi j.r.jivani K.h.Patel h.C.Trivedi P.G.Dept.of Chemistry Sardar Patel UniversityVallabh Vidyanagar Amneal Phamaceuticals

A graft copolymer of polyacrylonitrile （PAN） with sodium salt of partially carboxymethylated tamarind kernel powder （Na-PCMTKP, DS ^-= 0.15） was synthesized by using ceric ammonium nitrate （CAN） as a redox initiator in an aqueous medium. The optimum reaction conditions for affording maximum percentage of grafting were established by successively varying reaction conditions such as concentrations of nitric acid, CAN, monomer （AN） as well as reaction time, temperature and amount of substrate. The influence of these reaction conditions on the grafting yields was discussed. The kinetic scheme of free radical graft copolymerization was proposed and the experimental results were found to agree very well with the proposed kinetic scheme. The graft copolymer （Na-PCMTKP-g-PAN, percentage of grafting G = 413.76% and percentage of grafting efficiency GE = 96.48%） sample synthesized under the established optimized reaction conditions was hydrolyzed by 0.7 mol-L l NaOh solution at 90-95 ℃ to yield the superabsorbent hydrogel, h-Na-PCMTKP-g-PAN. The swelling behavior of the hydrogel was studied by carrying out its absorbency measurements in low conductivity water, 0.15 mol·L^-1 salt （NaCl, CaCl2 and AlCl3） solutions and simulated urine （SU） solution at different timings. FTIr, TGA and SEM techniques were used to characterize the products.

关键词： Sodium salt of partially carboxymethylated tamarind kernel powder Acrylonitrile Graft copolymerization Superabsorbent hydrogels Swelling behavior.

Spatial Estimation of Saturated hydraulic Conductivity from Terrain Attributes Using regression,Kriging,and Artificial Neural Networks

在线全文

学校读者我要写书评

暂无评论

Pedosphere 2011年第2期21卷 170-177页

作者： h.r.MOTAGhIAN j.MOhAMMADI Department of Soil Science Agriculture CollegeShahrekord UniversityShahrekord (Iran)

Several methods,including stepwise regression,ordinary kriging,cokriging,kriging with external drift,kriging with varying local means,regression-kriging,ordinary artificial neural networks,and kriging combined with artificial neural networks,were compared to predict spatial variation of saturated hydraulic conductivity from environmental *** methods except ordinary kriging allow for inclusion of secondary *** secondary spatial information used was terrain attributes including elevation,slope gradient,slope aspect,profile curvature and contour curvature.A multiple jackknifing procedure was used as a validation *** mean square error (rMSE) and mean absolute error (MAE) were used as the validation indices,with the mean rMSE and mean MAE used to judge the prediction *** performance by ordinary kriging was poor,indicating that prediction of saturated hydraulic conductivity can be improved by incorporating ancillary data such as terrain *** combined with artificial neural networks performed *** prediction models made better use of ancillary information in predicting saturated hydraulic conductivity compared with the competing *** combination of geostatistical predictors with neural computing techniques offers more capability for incorporating ancillary information in predictive soil *** is great potential for further research and development of hybrid methods for digital soil mapping.

关键词： digital elevation model geostatistics soil hydraulic properties spatial mapping

Generalizing plant–water relations to landscapes

在线全文

学校读者我要写书评

暂无评论

journal of Plant Ecology 2011年第1期4卷 101-113页

作者： r.h.Waring j.j.Landsberg College of Forestry Oregon State UniversityCorvallisOR 97331USA Withycombe Church LaneMt WilsonNSW 2786Australia

Aims Changing climate and land use patterns make it increasingly important that the hydrology of catchments and ecosystems can be reliably *** aim of this paper is to identify the biophysical factors that determine the rates of water vapor loss from different types of vegetation,and to seek,from an array of currently available satelliteborne sensors,those that might be used to initialize and drive landscape-level hydrologic *** Findings Spatial variation in the mean heights,crowd widths,and leaf area indices(LAI)of plant communities are important structural variables that affect the hydrology of *** stomatal conductance(G)imposes physiological limitation on transpiration by *** maximum value of G(Gmax)is closely linked to canopy photosynthetic capacity,which can be estimated via remote sensing of foliar chlorophyll or nitrogen *** be modeled as a nonlinear multipliable function of:(i)leaf–air vapor pressure deficit,(ii)water potential gradient between soil and leaves,(iii)photosynthetically active radiation absorbed by the canopy,(iv)plant nutrition,(v)temperature and(vi)the CO_(2) concentration of the *** surveys with Light Detection and ranging(LiDAr)and interferometric rADAr,along with high-resolution spectral coverage in the visible,near-infrared,and thermal infrared bands,provide,along with meteorological data gathered from weather satellites,the kind of information required to model seasonal and interannual variation in transpiration and evaporation from landscapes with diverse and dynamic vegetation.

关键词： canopy stomatal conductance plant water relations process-based models remote sensing

Microstructures in a carburized steel after isothermal pearlitic treatment

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

journal of Materials Science & Technology 2023年第29期160卷 66-75页

作者： j.Abraham Mathews h.Farahani j.Sietsma r.h.Petrov M.G.Mecozzi M.j.Santofimia Department of Materials Science and Engineering Delft University of TechnologyMekelweg 22628 CDDelftThe Netherlands Tata Steel research&Development IJmuidenThe Netherlands Department of Electromechanical Systems and Metal EngineeringGhent UniversityTech Lane Ghent Science park-Campus A ZwijnaardeTechnologiepark 46Belgium

The influence of carbon concentration variations on pearlite formation(20 h at 600℃)in a case-carburized steel is *** resultant microstructure shows three distinct regions:carburized case,a transition region,and the original *** microstructural transition from the case to the core regions is observed to be relatively *** investigated region of the carburized case(0.9 wt.%C)con-tains two types of pearlite:ferrite+cementite and ferrite+M_(23)C_(6),where the pearlitic aggregate with M_(23)C_(6)shows faster formation *** kinetics of pearlite formation in the transition region(0.3 wt.%C)is very slow and is observed with only M_(23)C_(6)*** around 40%austenite decomposes into pearlite in the transition region,which,in comparison to the carburized case region of 0.9 wt.%C is a fraction that is lower by a factor of *** is absent in the investigated core region(0.16 wt.%C).The microstructure in this region is predominantly martensite and pro-eutectoid ferrite,with a fraction of ferrite well below the equilibrium *** formation in this region is limited by the redistribution of mainly Ni,Mn,and Cr,and their resulting solute drag effect on the austenite/ferrite interface.A ther-modynamic and kinetic argumentation of these observations is provided with the help of thermodynamic data,precipitation simulations,and a general mixed-mode Gibbs energy balance model.

关键词： Pearlite formation Carburized steel M 2_(3)C_(6)carbide Kinetics Solute drag

3D Micromechanical Modeling of Failure and Damage Evolution in Dual Phase Steel Based on a real 2D Microstructure

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Acta Mechanica Solida Sinica 2016年第1期29卷 95-110页

作者： M.r.Ayatollahi A.Ch.Darabi h.r.Chamani j.Kadkhodapour Fatigue and Fracture Lab. Center of Excellence in Experimental Solid Mechanics and DynamicsSchool of Mechanical EngineeringIran University of Science and Technology

A plate of dual phase steel was produced from low carbon steel with intercritical annealing treatment. Its optically determined surface microstructure was utilized to construct three different microstructural models. To describe the ductile damage in the ferritic matrix, the Gurson-Tvergaard-Needleman model was used with the failure in the martensite phase being ignored. The numerical results obtained for the mechanism of void initiation and coalescence were compared with the experimental observations. The numerical results obtained from the randomly extruded 3D model showed a significantly better agreement with the experimental ones than those obtained from the 2D model or the uniformly extruded 3D model.

关键词： dual phase steel 3D model microstructure micromechanical modeling GTN dam-age model

Cyclic behavior of reinforced sand under principal stress rotation

在线全文

学校读者我要写书评

暂无评论

journal of rock Mechanics and Geotechnical Engineering 2017年第4期9卷 585-598页

作者： Alaa h.j. Al-rkaby A. Chegenizadeh h.r. Nikraz Department of Civil Engineering School of Civil and Mechanical Engineering Curtin University Perth Australia

Although the cyclic rotation of the principal stress direction is important,its effect on the deformation behavior and dynamic properties of the reinforced soil has not been reported to *** carried out on large-scale hollow cylinder samples reveal that the cyclic rotation of the principal stress direction results in significant variations of strain components(ε,ε,εand γ) with periodic characteristics despite the deviatoric stress being constant during *** oscillation can be related to the corresponding variations in the stress components and the anisotropic fabric that rotate continuously along the principal stress *** under rotation appears to develop a plastic *** trends are observed for reinforced sand,but the shear interaction,the interlocking between particles and reinforcement layer,and the confinement result in significant reductions in the induced strains and associated irrecoverable plastic *** of the strains occur in the first cycle,and as the number of cycles increases,the presence of strains becomes very small,which is almost *** indicates that the soil has reached anisotropic critical state(ACS),where a stable structure is formed after continuous orientation,realignment and rearrangement of the particles accompanied with increasing cyclic *** in the range of 60°-135° produces more induced strains even in the presence of the reinforcement,when compared with other *** relates to the extension mode of the test in this range in which σ>σand to the relative approach between the mobilized plane and the weakest horizontal *** results in an increase in shear modulus while it appears to have no effect on the damping *** cycles of rotation result in an increase in shear modulus and lower damping ratio due to the densification that causes a decrease in shear strain and less dissipation of energy.

关键词： Cyclic rotation Principal stress direction reinforced sand Strain components Damping ratio Shear modulus

CONVErGENCE OF ADAPTIVE EDGE ELEMENT METhODS FOr ThE 3D EDDY CUrrENTS EQUATIONS

在线全文

学校读者我要写书评

暂无评论

journal of Computational Mathematics 2009年第5期27卷 657-676页

作者： r.h.W.hoppe j.Schberl Institut fur Mathematik Universitat AugsburgD-86159AugsburgGermanyand Department of MathematicsUniversity of HoustonHoustonTX 77204-3008USA Dept.for Mathematics CCES(Center for Computational Engineering Science) RWTH AachenD-52074 AachenGermany

We consider an Adaptive Edge Finite Element Method （AEFEM） for the 3D eddy currents equations with variable coefficients using a residual-type a posteriori error estimator. Both the components of the estimator and certain oscillation terms, due to the occurrence of the variable coefficients, have to be controlled properly within the adaptive loop which is taken care of by appropriate bulk criteria. Convergence of the AEFEM in terms of reductions of the energy norm of the discretization error and of the oscillations is shown. Numerical results are given to illustrate the performance of the AEFEM.

关键词： Adaptive edge elements 3D eddy currents equations Convergence analysis,Error and oscillation reduction residual type a posteriori error estimates.

FLOW STrESS MODEL FOr hArD MAChINING OF AISI h13 WOrK TOOL STEEL

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2005年第6期18卷 741-748页

作者： h. Yan j. hua r. Shivpuri School of Mechanical-Electrical Engineering Nanchang University Nanchang 330029China The Ohio State University Columbus OH 43210 USA

An approach is presented to characterize the stress response of workpiece in hard machining, accounted for the effect of the initial workpiece hardness, temperature, strain and strain rate on flow stress. AISI h13 work tool steel was chosen to verify this methodology. The proposed flow stress model demonstrates a good agreement with data collected from published experiments. Therefore, the proposed model can be used to predict the corresponding flow stress-strain response of AISI h13 work tool steel with variation of the initial workpiece hardness in hard machining.

关键词： flow stress model hard machining AISI h13 work tool steel

Nonlinear elastic constitutive relations of residually stressed composites with stiff curved fibres

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics and Mechanics(English Edition) 2022年第10期43卷 1515-1530页

作者： M.h.B.M.Shariff j.Merodio r.Bustamante Department of Mathematics Khalifa University of Science and TechnologyAbu Dhabi127788United Arab Emirates Departamento de Matemática Aplicada a las TIC ETS de Ingeniería de Sistemas InformaticosUniversidad Politecnica de MadridMadrid28031Spain Departamento de Ingeniería Mecánica Universidad de ChileBeauchef 851Santiago CentroSantiago8370448Chile

Mechanical models of residually stressed fibre-reinforced solids,which do not resist bending,have been developed in the ***,in some residually stressed fibre-reinforced elastic solids,resistance to fibre bending is significant,and the mechanical behavior of such solids should be ***,in this paper,we model the mechanical aspect of residually stressed elastic solids with bending stiffness due to fibre curvature,which up to the authors’knowledge has not been mechanically modeled in the *** proposed constitutive equation involves a nonsymmetric stress and a couple-stress *** invariants are used in the constitutive equation,where each spectral invariant has an intelligible physical meaning,and hence they are useful in experiment and analysis.A prototype strain energy function is ***,we use this prototype to give results for some cylindrical boundary value problems.

关键词： fibre-reinforced solid residual stress bending stiffness spectral invariant second gradient finite elasticity