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Chinese Journal of Polymer Science 2023年第1期41卷 153-165页

作者： Xin-Peng Fan Yi-Hu Song Qiang Zheng Wan-Jie Wang MOE Key Laboratory of Macromolecular Synthesis and Functionalization Department of Polymer Science and EngineeringZhejiang UniversityHangzhou310027China Shanxi-Zheda Institute of New Materials and Chemical Engineering Taiyuan030000China College of Materials Science and Engineering Henan Key Laboratory of Advanced Nylon Materials and ApplicationZhengzhou UniversityZhengzhou450001China

To illustrate mechanisms of Payne effect in rubbers and their nanocomposites experiencing large amplitude oscillatory shear(LAOS),comparison studies were performed in styrene-isoprene-styrene(SIS)copolymers and their selectively crosslinked materials at temperatures below and above glass transition temperature of the polystyrene(PS)phase.It was found that under periodic dynamic shear,the strain softening is reversible when the polyisoprene(PI)phase,either crosslinked or not,is restricted by hard PS domains but it shows hysteresis once the PS domains disassociate.The strain softening can happen at the time scale of intrinsic Rouse relaxation of elastically active network strands.Critical stress of strain softening scales with number density of elastically active network strands,a simple relation being verified not only in the selectively crosslinked SIS copolymers but also in PI gum vulcanizates and carbon black filled PI compounds.Payne effect is traditionally used to term strain softening of highly filled rubber vulcanizates under LAOS deformation while evidenced herein is that the Payne effect of highly filled rubber vulcanizates shares the mechanism being common to the strain softening of SIS copolymers.

关键词： Large amplitude oscillatory shear SIS Rubber nanocomposites strain softening

ELASTO-PLASTIC CONSTITUTIVE MODEL OF SOIL-STRUCTURE INTERFACE IN CONSIDERATION OF strain softening AND DILATION

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Acta Mechanica Solida Sinica 2009年第2期22卷 171-179页

作者： Aizhao Zhou Tinghao Lu Key Laboratory for Geomechanics and Embankment Engineering of Ministry of Education Nanjing 210098 China Geotechnical Research Institute Hohai University Nanjing 210098 China

The behavior of soil-structure interface plays a major role in the definition of soil-structure interaction. In this paper a bi-potential surface elasto-plastic model for soil-structure interface is proposed in order to describe the interface deformation behavior,including strain softening and normal dilatancy. The model is formulated in the framework of generalized potential theory,in which the soil-structure interface problem is regard as a two-dimensional mathematical problem in stress field,and plastic state equations are used to replace the traditional field surface. The relation curves of shear stress and tangential strain are fitted by a piecewise function composed by hyperbolic functions and hyperbolic secant functions,while the relation curves of normal strain and tangential strain are fitted by another piecewise function composed by quadratic functions and hyperbolic secant functions. The approach proposed has the advantage of deriving an elastoplastic constitutive matrix without postulating the plastic potential functions and yield surface. Moreover,the mathematical principle is clear,and the entire model parameters can be identified by experimental tests. Finally,the predictions of the model have been compared with experimental results obtained from simple shear tests under normal stresses,and results show the model is reasonable and practical.

关键词： generalized potential theory strain softening shear dilatancy interface constitutive model

THE ASYMPTOTIC SOLUTION TO THE ANTIPLANE SHEAR DYNAMICCRACK-TIP FIELD IN AN ELASTIC strain-softening VISCOPLASTIC MATERIAL

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Applied Mathematics and Mechanics(English Edition) 1997年第2期18卷 173-179页

作者：李范春齐辉 Harbin Engineering University Harbin P. R. China

The elastic strain softening-viscoplastic model is given in this paper. Using this model, the asymptotic stress and strain equations surrounding the tip of a propagating crock are given and numerical results ale obtained under antiplane shear. The analysis and calculation show that at the crack tip the strain possesses logarithmic singularity (ln(R/r))(1/(n+1)) while the stress is like (ln(R/r))(-n/(n+1)), therefore the asymptotic behaviour of the elastic strain-softening viscoplastic field is revealed under the antiplane shear.

关键词： crack-tip field dynamic propagating strain softening

MICROMECHANICAL MODELLING OF strain softening IN MICROCRACK-WEAKENED QUASI-BRITTLE MATERIALS

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Acta Mechanica Solida Sinica 1995年第2期8卷 121-132页

作者： Feng Xiqiao Yu Shouwen(Dept.of Engineering Mechanics,Tsinghua University,Beijing 100084,P.R.China) Dept. of Engineering Mechanics Tsinghua University Beijing 100084 China

By using the concept of domain of microcrack growth(DMG),the micromechanisms of damage in quasi-brittle materials subjected to triaxial either tensile or compressive loading are investigated and the complete strew-strain relation including four stages is obtained from micromechanical analysis.The regime of pre-peak nonlinear hardening corresponds to the distributed damage,i.***.the stable propagation of microcracks.After the attainment of the ultimate strength of load-bearing capacity, some microcracks experience the second unstable growth and the distributed damage is transmitted to the localization of damage.These analyses improve our understanding of the hardening and softening behaviors of quasi-brittle materials.

关键词： microcracks strain softening constitutive relation micromechanical damage mechanics brittle material

Cyclic Bearing Mechanism of Suction Caissons Supporting Offshore Wind Turbines in Clay

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China Ocean Engineering 2021年第1期35卷 135-144页

作者： WANG Teng YU Shi-wen LIU Wen-long BAO Xing-xian LIU Jun-wei School of Petroleum Engineering China University of Petroleum(East China)Qingdao 266580China Department of Infrastructure Engineering The University of MelbourneParkville VIC3010Australia School of Civil Engineering Qingdao University of TechnologyQingdao 266520China

The bearing behavior of suction caissons supporting offshore wind turbines under two-way cyclic lateral loading and dead load in clay was investigated with consideration of soil strength degradation and adhesive interface friction between caisson walls and heterogeneous clay using the finite-element package ABAQUS.An ABAQUS built-in user subroutine was programmed to calculate the adhesive interface friction between clay and caisson walls.The results of parametric studies showed that the degradation of bearing capacity could be aggravated by the decrease of the aspect ratio.The offset between the rotation point of the soil inside the caisson and the central axis of the caisson increased with the increasing vertical load and number of cycles.The linearly increasing strength profile and adhesive interface led to the formation of an inverted spoon failure zone inside the caisson.The settlement-rotation curves in each cycle moved downwards with increasing number of cycles due to the soil strength degradation.

关键词： suction caisson adhesive contact cyclic loading strain softening clay

Application and Validation of a Multi-block Constitutive Model at Landslides of the Wenchuan Earthquake

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工程科学与技术 2018年第3期50卷 33-45页

作者： STAMATOPOULOS Constantine XIONG Ke DI Baofeng Stamatopoulos and Associates Limited Liability Company 5 Isavron Street Athens 114-71 Greece &Hellenic Open University Parodos Aristotelous 18 Patra 26335 Greece Institute for Disaster Management and Reconstruction Sichuan University Chengd

A multi-block model and a corresponding computer program have been developed which predict the kinematics of landslides.Furthermore,a unique event for studying different models simulating the triggering and movement of landslides is the 2008Wenchuan earthquake in the mountainous region in Sichuan Province of China,which caused a large number of rapid landslides.The purpose of the paper is two-fold:(a)to propose and incorporate into the multi-block model constitutive relations predicting soil response along slip surfaces,and(b)to apply the multi-block model with the constitutive relations at landslides triggered by the Wenchuan earthquake.The proposed constitutive equations predict the shape of the shear stress-displacement response measured in ring shear tests.In the application,four landslides caused by the Wenchuan earthquake were considered.Only in one of these landslides the shear resistance-displacement response along the slip surface has been measured in laboratory tests.At this landslide,the triggering and movement of the landslide was predicted.In the other landslides,back analyses were performed and it was observed that the multi-block model predicted reasonably well the final configuration of all slides.In addition,as the measured and back-estimated total friction angle of all landslides was less than 180,and the materials along the slip surface were sandy,it is inferred that some,or all of the slip surface during these slides was sheared in an undrained manner and excess pore pressures generated during sliding played a key role in the triggering and movement of these landslides.Concluding,the paper(A)proposed and validated a multi-block constitutive model which can be applied to predict the triggering and movement of earthquake-induced slides and(B)by analyzing four landslides of the 2008 Wenchuan earthquake,it concludes that some,or all of the slip surface during these slides,was sheared in an undrained manner and excess pore pressures generated during sliding played a key role in the triggering and m

关键词： Wenchuan earthquake multi-block model seismic displacement landslides back analysis strain softening

Constitutive model for Ya'an mudstone based on mesoscopic breakage mechanism

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Journal of Mountain Science 2023年第4期20卷 1159-1169页

作者： HE Yun-yong CHEN Cong WANG Fu-ming GUO Cheng-chao XIANG Bo YU Di LIU En-long DING Chun School of Civil Engineering Southwest Jiaotong UniversityChengdu610031China Sichuan Highway Planning SurveyDesign and Research Institute LtdChengdu610041China State Key Laboratory of Hydraulics and Mountain River Engineering College of Water Resources and HydropowerSichuan UniversityChengdu610065China School of Civil Engineering Sun Yat-sen UniversityGuangzhou510275China Ya’an Transportation Construction Group Co. Ltd.Ya’an625000China

The slope stability of Ya’an expressway in Sichuan dominated by mudstone strata,is influenced greatly by both the mechanical properties and stressstrain relationship of mudstone.In this paper,the mechanical properties of the Ya’an mudstone samples under triaxial compression conditions were studied,based on an established constitutive model under the framework of breakage mechanics to simulate the mechanical properties of mudstone.Firstly,triaxial compression tests and SEM tests at the confining pressures of 0.5 MPa,1.0 MPa,and 2.0 MPa were carried out on the mudstone samples,and it was found that the mudstone sample undergoes strain softening and dilatancy followed by the volumetric compaction.Then,based on analysis on the breakage mechanism of the above test results,we idealized the mudstone sample as a binary medium material consisting of the bonded elements and frictional elements,of which the bonded elements are composed of solid matrix and pores,and the frictional elements are composed of broken aggregates.During the loading process,the cementation between clay minerals and non-clay minerals in the mudstone sample is first destroyed,leading to the formation of micro-cracks within the particle aggregate,that is,the bonded elements are gradually damaged during the loading process and gradually turned into the frictional elements,and the two jointly bear the external load.The bonded elements are composed of mudstone matrix and pores,which have the cementitious characteristics of mudstone,and the frictional elements are composed of the broken aggregate with the frictional characteristics of the broken particles.Based on the homogenization theory,the constitutive model for the mudstone is established,and the determining method for model parameters is also given.Finally,the results of the triaxial compression tests of the mudstone samples are predicted by the constitutive model proposed here,which can reflect the main mechanical properties of the mudstone samples.

关键词： Mudstone Breakage mechanism Constitutive model strain softening Binary medium model

Numerical modelling of post-failure behaviors of coal specimens

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第2期16卷 514-531页

作者： Ajeet Yadav Bhaskara Behera Gauri Shankar Prasad Singh Sanjay Kumar Sharma Department of Mining Engineering Indian Institute of Technology(Banaras Hindu University)VaranasiUttar Pradesh221005India

A modelling approach consisting of best-fit relations to estimate the post-yield strength parameters is presented for simulating post-peak behavior beyond the point of residual strength of coal pillars having different w/h ratios.The model was developed based on back-analysis of the complete stress-strain behavior of specimens belonging to six different Indian coal seams with different w/h ratios of 0.5 e13.5.It was found that the simultaneous degradation of the cohesion and friction angle of the Mohr-Coulomb rock material characterizes the post-peak strength behavior of the rock.The resulting expressions are simplistic as they require parameters that can be easily determined using uniaxial and triaxial compression results.Eventually,the developed model was validated by simulating the triaxial tests of coal specimens with different sizes under varying confining stresses and comparing its findings with the published test results.The study showed that its implementation in the numerical model could reproduce laboratory-observed mechanical response,deformation behavior,and failure mechanism very closely.

关键词： strain softening Dilatancy Interface Shape effect Residual strength

Numerical Analysis and Centrifuge Modeling of Shallow Foundations

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China Ocean Engineering 2014年第2期28卷 163-180页

作者：罗强栾茂田杨蕴明王忠涛赵守正 Institute of Geotechnical Engineering School of Civil EngineeringDalian University of Technology Academy of Civil Engineering and Architecture Nanyang Normal University State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of Sciences

The influence of non-coaxial constitutive model on predictions of dense sand behavior is investigated in this paper. The non-coaxial model with strain softening plasticity is applied into finite-element program ABAQUS, which is first used to predict the stress-strain behavior and the non-coaxial characteristic between the orientations of the principal stress and principal plastic strain rate in simple shear tests. The model is also used to predict load settlement responses and bearing capacity factors of shallow foundations. A series of centrifuge tests for shallow foundations on saturated dense sand are performed under drained conditions and the test results are compared with the corresponding numerical results. Various footing dimensions, depths of embedment, and footing shapes are considered in these tests. In view of the load settlement relationships, the stiffness of the load-displacement curves is significantly affected by the non-coaxial model compared with those predicted by the coaxial model, and a lower value of non-coaxial modulus gives a softer response. Considering the soil behavior at failure, the coaxial model predictions of bearing capacity factors are more advanced than those of centrifuge test results and the non-coaxial model results;besides, the non-coaxial model gives better predictions. The non-coaxial model predictions are closer to those of the centrifuge results when a proper non-coaxial plastic modulus is chosen.

关键词： non-coaxial model strain softening FEM analysis centrifuge test shallow foundation

Cyclic behavior of soils and numerical analyses in cold regions and seismic zones

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Research in Cold and Arid Regions 2015年第5期7卷 492-502页

作者： Tadatsugu Tanaka The Japan Association of Rural Resource Recycling Solutions

The solutions of boundary value problems involving strain-softening material property contain serious difficulties from both modeling of strain-localization and a viewpoint of numerical procedure. Mesh size-dependent hardening modulus is considered to alleviate the mesh size-dependency of the solution. The elasto-plastic soil model with kinematic hardening model considering the cumulative deformation by cyclic loading is developed. In finite element analyses, the dynamic relaxation method combined with the generalized return-mapping algorithm is applied to the static drained and un-drained tri-axial tests and plane strain tests. The cyclic behavior of retaining wall problems by freeze and thaw in cold regions is also analyzed. Finally the dynamic progressive failure analysis of rockfill dam is carried out.

关键词： strain softening shear band kinematic hardening endochronic theory