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strain localization analyses of idealized sands in biaxial tests by distinct element method

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Frontiers of Structural and Civil Engineering 2010年第2期4卷 208-222页

作者： Mingjing JIANG Hehua ZHU Xiumei LI Department of Geotechnical Engineering and Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education Tongji UniversityShanghai 200092China

This paper presents a numerical investigation on the strain localization of an idealized sand in biaxial compression tests using the distinct element method(DEM).In addition to the dilatancy and material frictional angle,the principal stress field,and distributions of void ratio,particle velocity,and the averaged pure rotation rate(APR)in the DEM specimen are examined to illustrate the link between microscopic and macroscopic variables in the case of strain localization.The study shows that strain localization of the granular material in the tests proceeds with localizations of void ratio,strain and APR,and distortions of stress field and force chains.In addition,both thickness and inclination of the shear band change with the increasing of axial swain,with the former valued around 10-14 times of mean grain diameter and the later overall described by the Mohr-Coulomb theory.

关键词： idealized sand strain localization numerical analyses distinct element method(DEM)

Tensile and cyclic deformation response of friction-stir-welded dissimilar aluminum alloy joints:strain localization effect

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Journal of Materials Science & Technology 2021年第14期73卷 91-100页

作者： P.L.Niu W.Y.Li D.L.Chen State Key Laboratory of Solidification Processing Shaanxi Key Laboratory of Friction Welding TechnologiesNorthwestern Polytechnical UniversityXi'an710072.China Department of Mechanical and Industrial Engineering Ryerson University350 Victoria StreetTorontoOntarioM5B2K3Canada

Cyclic deformation behavior of friction-stir-welded dissimilar AA2024-T351 to AA7075-T65 aluminum alloy joints was evaluated via stepwise tests at different strain rates,along with transmission electron microscopy examinations to characterize the precipitates required to assess internal stresses.Electron backscatter diffraction was employed to observe the inhomogeneous microstructures of the FSWed joints.strain localization appeared in the heat affected zone(HAZ)of AA2024 side.After cyclic deformation of 500 cycles at a total strain amplitude of 0.5%,the strength of the dissimilar joints resumed basically to that of AA2024 base material.And the AA2024 HAZ was obviously hardened,which should be attributed to the introduced dislocations during cyclic deformation process.Cyclic hardening capacity of the joints increased with decreasing strain rate.

关键词： Friction stir welding Dissimilar aluminum alloys strain localization Cyclic hardening Slip irreversibility

Numerical simulation of strain localization and damage evolution in large plastic deformation using mixed finite element method

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Journal of University of Science and Technology Beijing 2004年第3期11卷 273-277页

作者： Zhanghua Chen Jiajian Jin Jiumei Xiao Applied Science School, University of Science and Technology Beijing, Beijing 100083, China Appl. Sci. Sch. Univ. of Sci. and Technol. Beijing Beijing 100083 China

An investigation of computer simulation is presented to analyze the effectsof strain localization and damage evolution in large plastic deformation. The simulation is carriedout by using an elastic-plastic-damage coupling finite element program that is developed based onthe concept of mixed interpolation of displacement/pressure. This program has been incorporated intoa damage mechanics model as well as the corresponding damage criterion. To illustrate theperformance of the proposed approach, a typical strain localization problem has been simulated. Theresults show that the proposed approach is of good capability to capture strain localization andpredict the damage evolution.

关键词： strain localization mixed element truesdell stress rate material damage

Basic theories for strain localization analysis of porous media with rate dependent model

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Science Bulletin 2005年第24期50卷 2793-2799页

作者： ZHANG Hongwu & QIN Jianmin State Key Laboratory of Structural Analysis and Industrial Equipment Dalian University of Technology, Dalian 116024, China State Key Laboratory of Structural Analysis and Industrial Equipment Dalian University of Technology Dalian China

This paper analyzes the interaction between two kinds of internal length scales when the rate dependen plasticity is introduced to a multiphase material model to study the dynamic strain localization phenomenon of satu rated and partially saturated porous media. The stability analysis demonstrates that the enhanced porous media mode preserves the well-posedness of the initial value problem for both axial and shear waves because an internal length scale parameter is introduced in the visco-plasticity model. On the other hand, the interaction between the length scale intro duced by the rate dependent model and that naturally con tained in the governing equations of fully and partially satu rated model will take place. A basic method is presented to investigate the internal length scale of the multiphase porou media under the interaction of these two kinds of length scale parameters. Material stability analysis is carried out for a certain permeability from which the results of wave number domain with real wave speed are distinguished. A one dimen sional example is given to illustrate the theoretical findings.

关键词： strain localization porous material rate dependent plas ticity internal length scale.

STUDY OF TEXTURE EFFECT ON strain localization OF BCC STEEL SHEETS

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Acta Mechanica Solida Sinica 2000年第2期13卷 95-104页

作者： Eiji Nakamachi Osaka Institute of Technology Osaka 535-8585Japan

Using elastic crystalline viscoplastic finite element (FE) annlysis, the formability of BCC steel sheets was assessed. An orientation probability assignment method in the FE modeling procedure, which can be categorized as an inhomogenized material modeling, was newly proposed. In the study, the crystal orientations of three materials, mild steel, dual phase steel and the high strength steel, were obtained by Xray diffraction and orientation distribution function (ODF) analyses. The measured ODF results have revealed clearly different textures in the sheets, featured by orientation fibers, skeleton lines and selected orientations in Euler angle space, which are closely related to the plastic anisotropy. Then, the crystal orientations were assigned to FE integration points by using this ODF data, individually. The FE analyses of the standard limiting dome height (LDH) test show how the fiber textures affect the extent of strain localization in the forming processes. It was confirmed by comparison with experimental results that this FE code could predict the extreme strain localization and assess the sheet formability.

关键词： crystalline plasticity texture orientation distribution function strain localization finite element analysis

Effect of work hardening discrepancy on strengthening of laminated Cu/CuZn alloys

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Journal of Materials Science & Technology 2022年第8期103卷 67-72页

作者： Zheng Cao Zhao Cheng Wei Xu Lei Lu Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China The State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang 110819China

To clarify the work hardening discrepancy effect on the strengthening of laminated metals,we designed two laminated Cu/Cu4Zn and Cu/Cu32Zn samples with different layer thicknesses.Cu/Cu4Zn has larger work hardening discrepancy between two constituent layers relative to Cu/Cu32Zn,but the yield strengths of two Cu Zn constituents are comparable.Uniaxial tensile results suggest Cu/Cu4Zn with larger work hardening discrepancy exhibits a significant strengthening at early deformation stage while Cu/Cu32Zn possesses a better ductility.The underlying mechanisms for the strengthening effect are attributed to more geometrically necessary dislocations accumulated at interfaces and severer strain localization due to the larger work hardening discrepancy.

关键词： Laminated Cu/Cu alloys Work hardening Strengthening Interfacial affected zone strain localization

strain Localized Deformation Variation of a Small-Scale Ductile Shear Zone

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Journal of Earth Science 2023年第2期34卷 409-430页

作者： Lefan Zhan Shuyun Cao Yanlong Dong Wenyuan Li State Key Laboratory of Geological Processes and Mineral Resources China University of GeosciencesWuhan 430074China

A continental-scale strike-slip shear zone frequently presents a long-lasting deformation and physical expression of strain localization in a middle to lower crustal level.However,the deformation evolution of strain localization at a small-scale remains unclear.This study investigatedstrain zone of mylonite.The microstructure and EBSD results revealed that the small-scale shear zone experienced ductile deformation under medium-high temperature conditions.Quartz aggregates suggested a consistent temperature with an irregular feature,exhibiting a dominated high-temperature prism slip system.Additionally,coarse-grained aggregates in the mylonite of the shear zone were deformed predominantly by dislocation creep,while ultra-plastic flow by viscous grain boundary sliding was an essential deformation process in the extremely fine-grained(~50μm)mixed-phases in the ultramylonite.Microstructural-derived strain rates calculated from quartz paleopiezometry were on the order of 10^(-15) to 10^(-13) s^(-1)from low-strain mylonite to high strained ultramylonite.The localization and strain ratelimited process was fluid-assisted precipitation presenting transitions of compositions as hydrous retrogression of hornblende to mica during increasing deformation and exhumation.Furthermore,the potential occurrence of the small-scale shear zone was initiated at a middle-deep crust seated crustal condition dominated by the temperature-controlled formation and rheological weakening.

关键词： strain localization ductile deformation ultramylonite microstructure EBSD texture Gaoligong shear zone

Non-Local Analysis of Forming Limits of Ductile Material Considering Void Growth

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Journal of Materials Science & Technology 2003年第4期19卷 294-299页

作者： Youngsuk Kim School of Mechanical Engineering Kyungpook National University702-701DaeguSouth Korea

The current study performed a finite element analysis of the strain localization behavior of a voided ductile material using a non-local plasticity formulation in which the yield strength depends on both an equivalent plastic strain measurement (hardening parameter) and Laplacian equivalent. The introduction of gradient terms to the yield function was found to play an important role in simulating the strain localization behavior of the voided ductile material. The effect of the mesh size and characteristic length on the strain localization were also investigated. An FEM simulation based on the proposed non-local plasticity revealed that the load-strain curves of the voided ductile material subjected to plane strain tension converged to one curve, regardless of the mesh size. In addition, the results using non-local plasticity also exhibited that the dependence of the deformation behavior of the material on the mesh size was much less sensitive than that with classical local plasticity and could be succe

关键词： Non-local Characteristic length Vbid Damage growth Gradient-dependent plasticity Forming limit strain localization

Effect of 1Al addition on deformation behavior of Mg

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Journal of Magnesium and Alloys 2021年第2期9卷 489-498页

作者： Ji Hyun Hwang A.Zargaran Gyeongbae Park O.Lee B.-J.Lee Nack J.Kim Center for Advanced Aerospace Materials Pohang University of Science and Technology(POSTECH)PohangSouth Korea

Deformation behavior of 1 Al containing Mg alloy has been investigated in the present study.After annealing,the Mg-1 Al alloy shows a typical basal texture.When compared to the pure Mg having a similar texture and grain size,the Mg-1 Al alloy shows much higher strength and larger elongation.Slip trace analyses of the tensile strained specimens show that non-basal slips such as pyramidal I and II slips can be easily activated at an early stage of deformation in the Mg-1 Al alloy and the grains in the Mg-1 Al alloy are seen to accommodate a larger degree of deformation than those in the pure Mg at a given strain.With increasing tensile strain,however,there is a strain localization along the initially formed slip lines of non-basal slips,forming surface steps without activating multiple slip lines.

关键词： Deformation behavior Slip trace analysis Non-basal slip strain localization Ductility