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critical state-induced emergence of superior magnetic performances in an iron-based amorphous soft magnetic composite

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Materials Futures 2024年第2期3卷 149-160页

作者： Liliang Shao Rongsheng Bai Yanxue Wu Jing Zhou Xing Tong Hailong Peng Tao Liang Zongzhen Li Qiaoshi Zeng Bo Zhang Haibo Ke Weihua Wang Songshan Lake Materials Laboratory Dongguan 523808People’s Republic of China Institute of Physics Chinese Academy of SciencesBeijing 100190People’s Republic of China School of Energy Power and Mechanical EngineeringNorth China Electric Power UniversityBeijing 100096People’s Republic of China School of Materials Science and Engineering Central South UniversityChangsha 410083People’s Republic of China Center for High Pressure Science and Technology Advanced Research Shanghai 201203People’s Republic of China Jiangsu JITRI Advanced Energy Materials Research Institute Co. LtdChangzhou 213000People’s Republic of China

Soft magnetic composites(SMCs)play a pivotal role in the development of high-frequency,miniaturization and complex forming of modern ***,they usually suffer from a trade-off between high magnetization and good magnetic softness(high permeability and low core loss).In this work,utilizing the order modulation strategy,a critical state in a FeSiBCCr amorphous soft magnetic composite(ASMC),consisting of massive crystal-like orders(CLOs,∼1 nm in size)with the feature ofα-Fe,is *** critical-state structure endows the amorphous powder with the enhanced ferromagnetic exchange interactions and the optimized magnetic domains with uniform orientation and fewer micro-vortex *** comprehensive soft magnetic properties at high frequency emerge in the ASMC,such as a high saturation magnetization(Ms)of 170 emu g^(-1)and effective permeability(µ_(e))of 65 combined with a core loss(Pcv)as low as 70 mW cm^(-3)(0.01 T,1 MHz).This study provides a new strategy for the development of high-frequency ASMCs,possessing suitable comprehensive soft magnetic performance to match the requirements of the modern magnetic devices used in the third-generation semiconductors and new energy fields.

关键词： amorphous soft magnetic composites critical state soft magnetic property rotating magnetic field annealing magnetic domain

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DEM investigation of strength and critical state behaviours of granular materials under true triaxial loadings

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Particuology 2024年第2期85卷 198-212页

作者： Minyi Zhu Guobin Gong Jun Xia Stephen Wilkinson Department of Civil Engineering Xi'an Jiaotong-Liverpool UniversityChina Department of Civil Engineering and Industrial Design University of LiverpoolLiverpoolUK Faculty of Engineering and Information Sciences University of Wollongong in DubaiUnited Arab Emirates

This paper investigates the strength and critical state(CS)behaviours of granular materials via DEM simulations of true triaxial drained tests under three different loading modes including constant b(in-termediate stress ratio)tests with constantσ'1(major principal stress),constant p(mean pressure)and constantσ'3(minor principal stress)*** this end,a series of samples are generated with the same particle size distribution,and with the confining stresses ranging from 100 kPa to 900 *** CS is achieved for all *** the macroscopic behaviours and the microscopic behaviours are examined and compared considering different loading modes,confining stresses and intermediate stress ratios(b).The critical state lines(CSLs)are found to be unique and independent of the loading modes,but dependent on the b *** CSLs with b=0 and b=1 form the two boundaries of CSLs respectively beyond which CSLs under all other b tests cannot go *** different strength criteria are examined and compared in terms of both peak and CS *** Mohr-Coulomb strength criterion is found to be only suitable for axisymmetric loading *** Lade-Duncan criterion is only suitable for describing peak strengths,which is dependent on the loading modes and confining *** Satake criterion and Matsuoka-Nakai criterion are the more appropriate strength criteria for describing CS failures,indicating that the CS values of both the Satake parameter and the Matsuoka-Nakai parameter describe an inherent property that characterizes the CS failure for a given type of *** CS mechanical coordination number is fitted by a curved line for a given b value,which is unique regardless of the loading *** peak and CS values of both major and minor principal fabric tensors decrease with increasing b values,while they increase with increasing b values for the intermediate principal fabric tensor.

关键词： Discrete element method Intermediate stress ratio Dilation critical state Failure criterion

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critical state shear behavior of the soil-structure interface determined by discrete element modeling

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Particuology 2017年第6期15卷 68-77页

作者： Xiaoqiang Gu Yuanwen Chen Maosong Huang Department of Ceotechnical Engineering Tongii University Shanghai 200092 China Key Laboratory of Ceotechnical and Underground Engineering of the Ministry of Education Shanghai 200092 China

The interface between soil and structure can be referred to as a soil-structure system, and its behavior plays an important role in many geotechnical engineering practices, In this study, results are presented from a series of monotonic direct shear tests performed on a sand-structure interface under constant normal stiffness using the discrete element method （DEM）. Strain localization and dilatancy behavior of the interface is carefully examined at both macroscopic and microscopic scales. The effects of soil initial relative density and normal stress on the interface shear behavior are also investigated, The results show that a shear band progressively develops along the structural surface as shear displacement increases. At large shear displacement a unique relationship between stress ratio and void ratio is reached in the shear band for a certain normal stress, indicating that a critical state exists in the shear band. It is also found that the thickness and void ratio of the shear band at the critical state decreases with increasing normal stress. Comparison of the DEM simulation results with experimental results provides insight into the shear behavior of a sand-structure interface and offers a means for quantitative modeling of such interfaces based on the critical state soil mechanics.

关键词： Discrete element method Interface Direct shear test Shear band Dilatancy critical state

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DEM simulations of critical state behaviour of granular materials under various drained triaxial stress path tests

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Particuology 2023年第10期81卷 98-108页

作者： Shiva Prashanth Kumar Kodicherla Guobin Gong Stephen Wilkinson Department of Civil Mining and Process EngineeringNamibia University of Science and TechnologyWindhoekNamibia Department of Civil Engineering Xi’an Jiaotong-Liverpool UniversitySuzhouChina Faculty of Engineering and Information Sciences University of WollongongDubai CampusDubaiUnited Arab Emirates

The present study investigates the critical state behaviour of granular assemblies composed of clumped particles under four different drained axisymmetric triaxial stress paths,using the discrete element method(DEM).A series of numerical samples were prepared at initial states with different density indexes(1D)and different initial confining pressures(ρ′0).These samples were sheared to large strains,at which constant stresses and volumes were maintained to reach the critical *** evolution of stress ratio under the same loading mode(for the same intermediate principal stress ratio,b)is shown to yield an almost identical behaviour independent of stress paths,whereas the stress-strain response depends on the stress *** different axisymmetric stress paths all share the same unique friction angle at critical state,indicating the Mohr-Coulomb failure criterion is the appropriate critical state strength criterion,which is at least true for the axisymmetric stress conditions.A unique coordination number(CN)is achieved at the critical state for a given po,which is independent of the stress *** critical state CN is found to increase with the increase in po,which could be attributed to the decrease in the critical state void ratio(ec)as mean effective stress(ρ′0)***,a unique linear functional relationship is found between the critical state values of cN and ec,and a unique polynomial functional relationship is found between the critical state values of CN andρ′.These functional relationships indicate no dependency on the stress paths or loading modes,thus characterizing unique features at critical states at both macroscopic and microscopic levels for a given type of granular material.

关键词： Discrete element method critical state Drained behaviour Triaxial stress paths

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Discrete element modelling of strength and critical state characteristics of granular materials under axial compression and axial extension stress path tests

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Particuology 2021年第3期19卷 152-162页

作者： Shiva Prashanth Kumar Kodicherla Guobin Gong Lei Fan Stephen Wilkinson Charles K.S.Moy Department of Civil Engineering Xi’an Jiaotong-Liverpool University(XJTLU)China Department of Civil Engineering University of WollongongDubai

The critical state soil mechanics(CSSM)framework has been widely used across a range of problems in geomechanics involving complex loading ***,the uniqueness of the critical state has been disputed for many years and it remains a controversial *** by previous investigations,a series of discrete element method(DEM)simulations were performed under both axial compression(AC)and axial extension(AE)stress *** samples were isotropically compressed at varying mean normal effective stresses(confining pressures)and sheared to a large axial strain of approximately 60%.It is found that there exist unique values of critical void ratios and stress ratios under critical state,which are independent of the samples’initial packings but dependent on stress *** the critical strength(stress ratio)for the AC stress path tests is higher than that for the AE stress *** critical state lines(CSLs)are found to path-dependent but unique for each stress path.A unique linear relationship between the critical coordination numbers and critical void ratios is identified under the AC and AE stress paths respectively,but such a relationship depends on the stress *** is also found that there exist unique values of microscopic parameters in terms of deviator fabric under critical state,which are independent of the samples’initial packings but dependent on stress *** these simulation results lead to the conclusion of non-uniqueness of CSLs from both macroscopic and microscopic viewpoints.

关键词： DEMClumped particles critical state Densification index state parameter

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An approximate nonlinear modified Mohr-Coulomb shear strength criterion with critical state for intact rocks

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Journal of Rock Mechanics and Geotechnical Engineering 2018年第4期10卷 645-652页

作者： Baotang Shen Jingyu Shi Nick Barton state Key Laboratory of Mining Disaster Prevention and Control Shandong University of Science and TechnologyQingdaoChina CSIRO Energy QCAT1 Technology CourtPullenvaleQLD4069Australia Nick Barton&Associates OsloNorway

In this paper, the Mohr-Coulomb shear strength criterion is modified by mobilising the cohesion and internal friction angle with normal stress, in order to capture the nonlinearity and critical state concept for intact rocks reported in the literature. The mathematical expression for the strength is the same as the classical form, but the terms of cohesion and internal friction angle depend on the normal stress now,leading to a nonlinear relationship between the strength and normal stress. It covers both the tension and compression regions with different expressions for cohesion and internal friction angle. The strengths from the two regions join continuously at the transition of zero normal stress. The part in the compression region approximately satisfies the conditions of critical state, where the maximum shear strength is reached. Due to the nonlinearity, the classical simple relationship between the parameters of cohesion, internal friction angle and uniaxial compressive strength from the linear Mohr-Coulomb criterion does not hold anymore. The equation for determining one of the three parameters in terms of the other two is supplied. This equation is nonlinear and thus a nonlinear equation solver is needed. For simplicity, the classical linear relationship is used as a local approximation. The approximate modified Mohr-Coulomb criterion has been implemented in a fracture mechanics based numerical code FRACOD,and an example case of deep tunnel failure is presented to demonstrate the difference between the original and modified Mohr-Coulomb criteria. It is shown that the nonlinear modified Mohr-Coulomb criterion predicts somewhat deeper and more intensive fracturing regions in the surrounding rock mass than the original linear Mohr-Coulomb criterion. A more comprehensive piecewise nonlinear shear strength criterion is also included in Appendix B for those readers who are interested. It covers the tensile, compressive, brittle-ductile behaviour transition and the

关键词： Shear strength Modified Mohr-Coulomb criterion critical state Intact rock

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Effect of fiber-reinforcement on the mechanical behavior of sand approaching the critical state

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Journal of Rock Mechanics and Geotechnical Engineering 2022年第4期14卷 1241-1252页

作者： Jakhongirbek Ganiev Shotaro Yamada Masaki Nakano Takayuki Sakai Department of Civil Engineering Nagoya UniversityNagoya464-8603Japan Department of Civil Engineering Tohoku UniversitySendai980-8579Japan

Several types of ground improvement methods that employ fiber-reinforcement have been developed in recent years.A series of consolidated drained triaxial compression tests has been conducted here to examine the effect of short fibers on the mechanical properties of Toyoura *** with 0%,0.2%,0.4%,and 1%fiber contents,prepared to yield random distribution,was sheared under several confining pressures and controlled via their initial relative *** test results showed that the maximum and residual deviatoric stresses increased,whereas the volumetric expansion decreased with an increase in fiber *** the stress ratio h(=q/p′)and specific volume changed depending on the fiber content and confining pressure with shear progression,they each reached the same values for a definite fiber content at the end of shearing,independent of initial relative *** other words,the unique critical state line can be found for a definite fiber ***,the greater the fiber content,the larger the slope of the critical state line at the end of ***,as the length of fibers shortened with the same percentage of fiber inclusions in sand,the deviatoric stress and the stress ratio decreased,approaching the shear-strain-volumetric response of unreinforced sand.

关键词： Fiber-reinforced sand Triaxial compression Stress ratio critical state Relative density

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Cyclic liquefaction screening of sand with non-plastic fines:critical state approach

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Geoscience Frontiers 2020年第2期11卷 429-438页

作者： Md.Mizanur Rahman TGSitharam Natural and Built Environments Research Centre(NBERC) School of Natural and Built EnvironmentsUniversity of South AustraliaMawson LakesSA 5095Australia Department of Civil Engineering Indian Institute of Science(IISc)BangaloreIndia

There have been significant advances in the application of critical state,CS,in liquefaction potential *** was done by comparing state parameter,j with estimated characteristic cyclic stress ratio,CSR due to an earthquake.A cyclic resistance ratio,CRR curve,which can be determined from cyclic liquefaction tests,separates historical liquefied and non-liquefied data points(j,CSR).On the other hand,the concepts of equivalent granular state parameter,j*,which was developed for sands with fines,can be used in lieu j to provide a unifying framework for characterizing the undrained response of sands with non/low plasticity fines,irrespective of fines content(fc).The present work combines these two propositions,and by merely substituting j*for j into the aforementioned CS approach to capture the influence of fc.A series of static and cyclic triaxial tests were conducted,separately and independently of the concept of j*,for sand with up to fc of 30%.The clean sand was collected from Sabarmati river belt at Ahmedabad city in India which was severely affected during the Bhuj earthquake,*** experimental data gave a single relation for CRR and j*which was then used to assess liquefaction potential for a SPT based case study,where fc varies along the *** prediction matched with the field observation.

关键词： critical state state parameter Liquefaction Sands Fines Constitutive model

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Numerical analysis of slope collapse using SPH and the SIMSAND critical state model

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Journal of Rock Mechanics and Geotechnical Engineering 2022年第1期14卷 169-179页

作者： Zhao Lu Zhuang Jin Panagiotis Kotronis Civil and Environmental Engineering University of MacaoMacaoChina Research and Development Center Shenzhen Foundation Engineering Co.Ltd.Shenzhen518000China Department of Civil and Environmental Engineering The Hong Kong Polytechnic UniversityHong KongChina Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou) Guangzhou510000China Department of Ocean Science and Engineering Southern University of Science and TechnologyShenzhen518000China Institut de Recherche en Génie Civil et Mécanique(GeM) École Centrale de NantesUniversitéde NantesRue de la NoëNantes44321France

Geological disasters such as slope failure and landslides can cause loss of life and ***,reproducing their evolution process is of great importance for risk assessment and *** recently developed SIMSAND critical state sand model combined with the smoothed particle hydrodynamics(SPH)method is adopted in this work to study slope failure under large *** illustrate the efficiency and accuracy of the SIMSAND-SPH approach,a series of slope collapse studies using the discrete element method(DEM)considering various particle shapes(***,tetrahedral and elongated)is adopted as *** parameters of the SIMSAND model are calibrated using DEM triaxial *** comparison to the DEM simulations,the runout distance and final slope height are well characterized with the SIMSAND-SPH approach with less computational *** comparisons show that the SIMSAND-SPH approach is highly efficient and accurate,which can be an alternative numerical tool to simulate real scale granular flow.

关键词： Granular material Smoothed particle hydrodynamics(SPH) Large deformations Landslide critical state Slope failure Sand

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Thermo-mechanical constitutive modeling of unsaturated clays based on the critical state concepts

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Journal of Rock Mechanics and Geotechnical Engineering 2015年第2期7卷 193-198页

作者： Saeed Tourchi Amir Hamidi School of Engineering Kharazmi University

A thermo-mechanical constitutive model for unsaturated clays is constructed based on the existingmodel for saturated clays originally proposed by the authors. The saturated clays model was formulatedin the framework of critical state soil mechanics and modified Cam-clay model. The existing model hasbeen generalized to simulate the experimentally observed behavior of unsaturated clays by introducingBishop＇s stress and suction as independent stress parameters and modifying the hardening rule and yieldcriterion to take into account the role of suction. Also, according to previous studies, an increase intemperature causes a reduction in specific volume. A reduction in suction （wetting） for a given confiningstress may induce an irreversible volumetric compression （collapse）. Thus an increase in suction （drying）raises a specific volume i.e. the movement of normal consolidation line （NCL） to higher values of voidratio. However, some experimental data confirm the assumption that this reduction is dependent on thestress level of soil element. A generalized approach considering the effect of stress level on themagnitude of clays thermal dependency in compression plane is proposed in this study. The number ofmodeling parameters is kept to a minimum, and they all have clear physical interpretations, to facilitatethe usefulness of model for practical applications. A step-by-step procedure used for parameter calibrationis also described. The model is finally evaluated using a comprehensive set of experimental datafor the thermo-mechanical behavior of unsaturated soils.2015 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.

关键词： Constitutive model Unsaturated clays Plasticity Cam-clay critical state

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