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New constitutive equation utilizing grain size for modeling of hot deformation behavior of AA1070 aluminum

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Transactions of Nonferrous Metals Society of China 2021年第2期31卷 345-357页

作者： h.r.rezaei ashtiani A.A.ShAYANPOOr School of Mechanical Engineering Arak University of TechnologyArak38135-1177Iran

A new phenomenological and empirically-based constitutive model was proposed to modify the term in the original Johnson−Cook constitutive *** new model can be used to describe and predict the flow stress of AA1070 aluminum with different initial grain sizes in the hot working *** developed model considers thermal softening,strain-rate hardening,strain hardening,initial grain size,and interactions with each other and can correctly model the behavior of AA1070 at elevated temperature with different strains,strain rates,and initial grain *** hot flow behavior of AA1070 was investigated through compression tests over wide ranges of temperature from 623 to 773 K,strain rate from 0.005 to 0.5 s−1 and initial grain size from 50 to 450μ*** show that the initial grain size has a significant effect on the flow behavior of ***,correlation coefficient(r),average absolute relative error(AArE),and relative error were examined for comparative predictability of the *** show that flow stresses for different initial grain sizes calculated by the new proposed model perfectly correlate with experimental ones,with a mean relative error of 1.19%,which confirms that the new modified Johnson−Cook relation can give a precise estimation of the hot flow stress of AA1070 aluminum by considering the initial grain size.

关键词： constitutive equation modified Johnson−Cook model initial grain size flow stress hot deformation AA1070 aluminum

Constitutive modeling of flow behavior of precipitation-hardened AA7022-T6 aluminum alloy at elevated temperature

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Transactions of Nonferrous Metals Society of China 2020年第11期30卷 2927-2940页

作者： h.r.rezaei ashtiani P.ShAhSAVArI School of Mechanical Engineering Arak University of TechnologyArakIran

The thermomechanical behavior of precipitation-hardened aluminum alloy AA7022-T6 was studied using isothermal compression at temperatures of 623−773 K and strain rates of 0.01−1 s^−*** experimental results indicated that dynamic recrystallization(DrX)is a predominant hot deformation mechanism,especially at elevated temperatures and low strain *** modified Johnson−Cook(J−C)and the strain compensated Arrhenius-type models were developed to predict the hot flow behavior under different deformation *** correlation coefficients of modified J−C model and the strain compensated Arrhenius-type models were 0.9914 and 0.9972,respectively,their average relative errors(ArE)were 6.074%and 4.465%,respectively,and their root mean square errors(rMSE)were 10.611 and 1.665 MPa,respectively,indicating that the strain compensated Arrhenius-type model can predict the hot flow stress of AA7022-T6 aluminum alloy with an appropriate accuracy.

关键词： flow behavior constitutive models Arrhenius model dynamic recrystallization AA7022-T6 aluminum alloy

In Situ Mineralization of Biomass-Derived hydrogels Boosts Capacitive Electrochemical Energy Storage in Free-Standing 3D Carbon Aerogels

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Energy & Environmental Materials 2024年第2期7卷 359-371页

作者： Anjali Achazhiyath Edathil Babak rezaei Kristoffer Almdal Stephan Sylνest Keller National Centre for Nano Fabrication and Characterization DTU NanolabTechnical University of Denmark2800LyngbyDenmark DTU Chemistry Technical University of Denmark2800LyngbyDenmark

here,a novel fabrication method for making free-standing 3D hierarchical porous carbon aerogels from molecularly engineered biomass-derived hydrogels is *** situ formed flower-like CaCO_(3)molecularly embedded within the hydrogel network regulated the pore structure during in situ mineralization assisted one-step activation graphitization(iMAG),while the intrinsic structural integrity of the carbon aerogels was *** homogenously distributed minerals simultaneously acted as a hard template,activating agent,and graphitization *** decomposition of the homogenously distributed CaCO_(3)during iMAG followed by the etching of residual CaO through a mild acid washing endowed a robust carbon aerogel with high porosity and excellent electrochemical *** 0.5 mA cm^(-2),the gravimetric capacitance increased from 0.01 F g^(-1)without mineralization to 322 F g^(-1)with iMAG,which exceeds values reported for any other free-standing or powder-based biomass-derived carbon *** outstanding cycling stability of~104%after 1000 cycles in 1 M hClO4 was *** assembled symmetric supercapacitor device delivered a high specific capacitance of 376 F g^(-1)and a high energy density of 26 W h kg^(-1)at a power density of 4000 W kg^(-1),with excellent cycling performance(98.5%retention after 2000 cycles).In combination with the proposed 3D printed mold-assisted solution casting(3DMASC),iMAG allows for the generation of free-standing carbon aerogel architectures with arbitrary ***,the novel method introduces flexibility in constructing free-standing carbon aerogels from any ionically cross-linkable biopolymer while maintaining the ability to tailor the design,dimensions,and pore size distribution for specific energy storage applications.

关键词： biomass carbon aerogel sustainable energy materials free-standing supercapacitors

Effect of ECAP consolidation temperature on the microstructure and mechanical properties of Al-Cu-Ti metallic glass reinforced aluminum matrix composite

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Journal of Materials Science & Technology 2017年第9期33卷 1031-1038页

作者： M.r.rezaei S.G.Shabestari S.h.razavi School of Metallurgy and Materials Engineering Iran University of Science and Technology (IUST) Center of Excellence for high Strength Alloys Technology (CEhSAT) School of Metallurgy and Materials EngineeringIran University of Science and Technology (IUST)

Al;Cu;Ti;metallic glass（AMG） reinforced Al matrix composites were consolidated by equal channel angular pressing（ECAP） process. The effects of ECAP consolidation temperature ranging from room temperature to just below the first crystallization temperature of metallic glass on the consolidation of composites were investigated in terms of the relative densities, structural evolutions and mechanical properties of composites. Some intermetallic compounds included Al;CuTi;, Al;Ti and Al;Cu;precipitated from metallic glass particles at consolidation temperature of 300?C. Consolidation temperature did not affect the matrix grains size of the composite. Quantitative analysis revealed that the distribution of reinforcing particles was considerably dependent on consolidation temperature. Density of the composite was increased by increasing the consolidation temperature to 250?C. The composite consolidated at250?C through ECAP process, exhibited the best combination of yield strength and ductility of 184 MPa and 48%, respectively.

关键词： Al matrix composite(AMC) Equal channel angular pressing(ECAP) Consolidation temperature Glass particles

On the Supercyclicity and hypercyclicity of the Operator Algebra

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Acta Mathematica Sinica,English Series 2008年第7期24卷 1221-1232页

作者： B.YOUSEFI h.rezaei Department of Mathematics College of SciencesShiraz UniversityShiraz 71454Iran and Department of MathematicsPayame-Noor UniversityIran

Let B（X） be the operator algebra for a separable infinite dimensional hilbert space h, endowed with the strong operator topology or ＊-strong topology. We give sufficient conditions for a continuous linear mapping L ： B（X） →B（X） to be supercyclic or ,-supercyclic. In particular our condition implies the existence of an infinite dimensional subspace of supercyclic vectors for a mapping T on h. hypercyclicity of the operator algebra with strong operator topology was studied＇ by Chan and here we obtain an analogous result in the case of ＊-strong operator topology.

关键词： operator algebra,*-strong topology strong operator topology hypercyclicity criterion supercyclicity criterion

Lossless multi-scale constitutive elastic relations with artificial intelligence

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npj Computational Materials 2022年第1期8卷 638-649页

作者： Jaber rezaei Mianroodi Shahed rezaei Nima h.Siboni Bai-Xiang Xu Dierk raabe Microstructure Physics and Alloy Design Max-Planck-Institut für EisenforschungDüsseldorfGermany Ergodic Labs Lohmühlenstraße 6512435BerlinGermany Mechanics of Functional Materials Division Institute of Materials ScienceTechnische Universität DarmstadtDarmstadtGermany

A seamless and lossless transition of the constitutive description of the elastic response of materials between atomic and continuum scales has been so far *** we show how this problem can be overcome by using artificial intelligence(AI).A convolutional neural network(CNN)model is trained,by taking the structure image of a nanoporous material as input and the corresponding elasticity tensor,calculated from molecular statics(MS),as *** with the atomistic data,the CNN model captures the size-and pore-dependency of the material’s elastic properties which,on the physics side,derive from its intrinsic stiffness as well as from surface relaxation and non-local *** demonstrate the accuracy and the efficiency of the trained CNN model,a finite element method(FEM)-based result of an elastically deformed nanoporous beam equipped with the CNN as constitutive law is compared with that obtained by a full atomistic *** trained CNN model predicts the elasticity tensor in the test dataset with a root-mean-square error of 2.4 GPa(3.0%of the bulk modulus)when compared to atomistic *** the other hand,the CNN model is about 230 times faster than the MS calculation and does not require changing simulation methods between different *** efficiency of the CNN evaluation together with the preservation of important atomistic effects makes the trained model an effective atomistically informed constitutive model for macroscopic simulations of nanoporous materials,optimization of nanostructures,and the solution of inverse problems.

关键词： constitutive artificial elasticity

Analysis of the Longitudinal Structure Function F_L from the Non-linear regge Gluon Density Behavior at Low-x

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Chinese Physics Letters 2015年第11期32卷 18-21页

作者： BOrOUN G.r. rezaei B. Physics Department Razi University

The longitudinal structure function with shadowing correction according to the nonlinear effects of the gluon density behavior at low x is considered. The solution of the GLr-MQ evolution equation for the gluon density shows that the FL^g（x, Q2） behavior can be tamed by the singularity at low x values. Comparing our results with h1 data at r=4 GeV-1 shows that at very low x this behavior is completely tamed by taking shadowing correction into account.

关键词： Analysis of the Longitudinal Structure Function F_L from the Non-linear regge Gluon Density Behavior at Low-x

Teaching solid mechanics to artificial intelligence—a fast solver for heterogeneous materials

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npj Computational Materials 2021年第1期7卷 899-908页

作者： Jaber rezaei Mianroodi Nima h.Siboni Dierk raabe Microstructure Physics and Alloy Design Max-Planck-Institut für EisenforschungDüsseldorfGermany DeepMetis BerlinGermany

We propose a deep neural network(DNN)as a fast surrogate model for local stress calculations in inhomogeneous non-linear *** show that the DNN predicts the local stresses with 3.8%mean absolute percentage error(MAPE)for the case of heterogeneous elastic media and a mechanical contrast of up to factor of 1.5 among neighboring domains,while performing 103 times faster than spectral *** DNN model proves suited for reproducing the stress distribution in geometries different from those used for *** the case of elasto-plastic materials with up to 4 times mechanical contrast in yield stress among adjacent regions,the trained model simulates the micromechanics with a MAPE of 6.4%in one single forward evaluation of the network,without any *** results reveal an efficient approach to solve non-linear mechanical problems,with an acceleration up to a factor of 8300 for elastic-plastic materials compared to typical solvers.

关键词： artificial network faster

Investigations on landmine detection by BF_3 detector

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Nuclear Science and Techniques 2007年第4期18卷 237-241页

作者： D.rezaei OChBELAGh h.Miri hAKIMABAD r.Izadi NAJAFABADI Department of Physics University of Mohaghegh ArdabilyP.O. Box 179ArdebilIran Physics Department Faculty of SciencesFerdowsi University of MashhadMashhadIran

Experiments were carried out to investigate the possible use of neutron backscattering for the detection of polyethylene (PE) sample buried in the soil. In detection of landmine by neutrons, the neutron detector and its shield play an important role. In this paper, the effects of graphite, heavy water, polyethylene and boric acid moderators on the flux of back scattered neutrons were investigated. We have also experimentally verified the effect of BF3 detector shield and obtained good agreement with theory.

关键词：地雷中子源中子反散射 BF3装置重水