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Size Effect on Onset and Subsequent Evolution of adiabatic shear band:Theoretical and Numerical Analysis

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Acta Mechanica Solida Sinica 2020年第3期33卷 294-306页

作者： Jiejian Liu Tao Suo Fenghua Zhou Yulong Li School of Aeronautics Northwestern Polytechnical UniversityXi’an 710072China Shaanxi Key Laboratory of Impact Dynamics and Its Engineering Application Xi'an 710072China Joint International Research Laboratory of Impact Dynamics and Its Engineering Application Xi'an 710072China The Faculty of Mechanical Engineering and Engineering Mechanics Ningbo UniversityNingbo 315211China

The adiabatic shear instability of ductile materials has attracted more and more attentions of researchers and groups,who have been sparing no effort in further understanding of the underlying mechanism since the first experimental depiction of adiabatic shear instability by Zener and *** for the adiabatic shear instability,many factors account for its occurrence,including heat conduction,inertia effect,microstructure effect and so ***,lots of experimental evidence has shown that metal materials display a strong size effect when the characteristic length scale is in the order of *** size effect has also been observed in the analysis of shear band in the ductile materials because the order of the bandwidth stays within the microscale ***,a comprehensive understanding of the whole process of adiabatic shear banding(ASB),including the early onset and the subsequent evolution,is still *** this work,a gradient plasticity model based on the Taylor-based nonlocal theory feasible for the linear perturbation analysis and convenient for numerical calculation is proposed to investigate the strain gradient on the onset of ASB and the coupling effect of heat conduction,inertia effect and strain gradient at the early stage,as well as on the subsequent evolution process at later *** for the onset of ASB,the linear perturbation method is used to consider the effect on the initial formation of *** the investigation of the onset of *** characteristic line method is applied to describe the subsequent nonlinear evolution process of *** stages of ASB evolution are clearly depicted during the evolution process,and the significance of size effect on the ASB nonlinear evolution process of ASB at different stages is *** the help of linear perturbation analysis and characteristic line method,a comprehensive description of the role of strain gradient in the ASB from the early onset to the end of the evolution is provided.

关键词： adiabatic shear band Strain gradient Nonlinear evolution process Linear perturbation method Characteristic line method

Multi-scale crystal plasticity finite element simulations of the microstructural evolution and formation mechanism of adiabatic shear bands in dual-phase Ti20C alloy under complex dynamic loading

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Journal of Materials Science & Technology 2020年第24期59卷 138-148页

作者： Yu Zhou Qunbo Fan Xin Liu Duoduo Wang Xinjie Zhu Kai Chen School of Materials Science and Engineering Beijing Institute of TechnologyBeijing 100081China National Key Laboratory of Science and Technology on Materials Under Shock and Impact Beijing 100081China Beijing Institute of Technology Chongqing Innovation Center Chongqing 401135China

A dynamic compression test was performed on α+β dual-phase titanium alloy Ti20C using a split Hopkinson pressure *** formation of adiabatic shear bands generated during the compression process was studied by combining the proposed multi-scale crystal plasticity finite element method with experimental *** complex local micro region load was progressively extracted from the simulation results of a macro model and applied to an established three-dimensional multi-grain microstructure ***,the evolution histories of the grain shape,size,and orientation inside the adiabatic shear band were quantitatively *** results corresponded closely to the experimental results obtained via transmission electron microscopy and precession electron ***,by calculating the grain rotation and temperature rise inside the adiabatic shear band,the microstructural softening and thermal softening effects of typical heavily-deformed α grains were successfully *** results revealed that the microstructural softening stress was triggered and then stabilized(in general)at a relatively high *** indicated that the mechanical strength was lowered mainly by the grain orientation evolution or dynamic recrystallization occurring during early plastic ***,thermal softening increased linearly and became the main softening ***,in the final stage,the thermal softening stress accounted for 78.4% of the total softening stress due to the sharp temperature increase,which inevitably leads to the stress collapse and potential failure of the alloy.

关键词： Titanium alloy adiabatic shear band Multi-scale crystal plastic finite element method(CPFEM) Orientation evolution Softening mechanism

Microstructural softening induced adiabatic shear banding in Ti-23Nb-0.7Ta-2Zr-O gum metal

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Journal of Materials Science & Technology 2020年第19期54卷 31-39页

作者： Silu Liu Y.Z.Guo Z.L.Pan X.Z.Liao E.J.Lavernia Y.T.Zhu Q,M,Wei Yonghao Zhao Nano and Heterogeneous Materials Center School of Materials Science and EngineeringNanjing University of Science and TechnologyNanjing 210094China School of Aeronautics Northwestern Polytechnical UniversityXi’an 710072China Department of Mechanical Engineering University of North Carolina at CharlotteNC 28223-0001USA School of Aerospace Mechanical and Mechatronic EngineeringThe University of SydneyNSW 2006Australia Department of Materials Science and Engineering University of Californi1IrvineCA 92697USA Department of Materials Science and Engineering North Carolina State UniversityNC 27695USA

Ti-23Nb-0.7Ta-2Zr-O gum metal(GM)is an attractive candidate material for applications that require superior mechanical *** our earlier investigation of the GM[1],geometrical softening and the generation of adiabatic shear bands(ASBs)were proposed as primary reasons for the documented anisotropic impact *** the present study,electron backscattered diffraction(EBSD)analysis reveals two different deformed microstructures,i.e.,deformed ultrafine grains(UFGs)and dynamically recrystallized UFGs,formed in the ASBs of GM samples processed by extrusion equal channel angular pressing(ECAP),*** calculation of temperature rise during dynamic compression suggests that the above microstructure differences in the ASBs was originated from their different maximum ASB temperatures(608 K for extruded GM and 1159 K for ECAP-processed GM).Moreover,our calculation on the temperature at the onset of ASBs indicates that microstructural softening is the primary cause for the development of ASBs in both extruded GM(321 K)and ECAP-processed GM(331 K).

关键词： Gum metal Split hopkinson bar adiabatic shear band Microstructures

adiabatic shear localization evolution for steel based on the Johnson-Cook model and gradient-dependent plasticity

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Journal of University of Science and Technology Beijing 2006年第4期13卷 313-318页

作者： Xuebin Wang Department of Mechanics and Engineering Sciences Liaoning Technical University Fuxin 123000 China

Gradient-dependent plasticity is introduced into the phenomenological Johnson-Cook model to study the effects of strainhardening, strain rate sensitivity, thermal-softening, and microstructure. The microstructural effect （interactions and interplay among microstructures） due to heterogeneity of texture plays an important role in the process of development or evolution of an adiabatic shear band with a certain thickness depending on the grain diameter. The distributed plastic shear strain and deformation in the shear band are derived and depend on the critical plastic shear strain corresponding to the peak flow shear stress, the coordinate or position, the internal length parameter, and the average plastic shear strain or the flow shear stress. The critical plastic shear strain, the distributed plastic shear strain, and deformation in the shear band are numerically predicted for a kind of steel deformed at a constant shear strain rate. Beyond the peak shear stress, the local plastic shear strain in the shear band is highly nonuniform and the local plastic shear deformation in the band is highly nonlinear. shear localization is more apparent with the increase of the average plastic shear strain. The calculated distributions of the local plastic shear strain and deformation agree with the previous numerical and experimental results.

关键词： adiabatic shear band steel strain-hardening gradient-dependent plasticity Johnson-Cook model

adiabatic shear Localization for Steels Based on Johnson-Cook Model and Second-and Fourth-Order Gradient Plasticity Models

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Journal of Iron and Steel Research International 2007年第5期14卷 56-61页

作者： WANG Xue-bin Department of Mechanics and Engineering Sciences Liaoning Technical University Fuxin 123000 Liaoning China

To consider the effects of the interactions and interplay among microstructures, gradient-dependent models of second- and fourth-order are included in the widely used phenomenological Johnson-Cook model where the effects of strain-hardening, strain rate sensitivity, and thermal-softening are successfully described. The various parameters for 1006 steel, 4340 steel and S-7 tool steel are assigned. The distributions and evolutions of the local plastic shear strain and deformation in adiabatic shear band （ASB） are predicted. The calculated results of the second- and fourth- order gradient plasticity models are compared. S-7 tool steel possesses the steepest profile of local plastic shear strain in ASB, whereas 1006 steel has the least profile. The peak local plastic shear strain in ASB for S-7 tool steel is slightly higher than that for 4340 steel and is higher than that for 1006 steel. The extent of the nonlinear distribution of the local plastic shear deformation in ASB is more apparent for the S-7 tool steel, whereas it is the least apparent for 1006 steel. In fourth-order gradient plasticity model, the profile of the local plastic shear strain in the middle of ASB has a pronounced plateau whose width decreases with increasing average plastic shear strain, leading to a shrink of the portion of linear distribution of the profile of the local plastic shear deformation. When compared with the sec- ond-order gradient plasticity model, the fourth-order gradient plasticity model shows a lower peak local plastic shear strain in ASB and a higher magnitude of plastic shear deformation at the top or base of ASB, which is due to wider ASB. The present numerical results of the second- and fourth-order gradient plasticity models are consistent with the previous numerical and experimental results at least qualitatively.

关键词： adiabatic shear band steel gradient-dependent plasticity Johnson-Cook model second-order gradient fourth-order gradient

adiabatic shear sensitivity of ductile metal based on gradient-dependent JOHNSON-COOK model

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Transactions of Nonferrous Metals Society of China 2011年第6期21卷 1355-1361页

作者：王学滨辽宁工程技术大学力学与工程学院阜新123000

Based on the expression proposed by WANG for the local plastic shear deformation distribution in the adiabatic shear band（ASB） using gradient-dependent plasticity,the effects of 10 parameters on the adiabatic shear sensitivity were *** experimental data for a flow line in the ASB obtained by LIAO and DUFFY were fitted by use of the curve-fitting least squares method and the proposed *** critical plastic shear strains corresponding to the onset of the ASB for Ti-6Al-4V were assessed at different assigned ASB *** is found that the proposed expression describes well the non-linear deformation characteristics of the flow line in the *** parameters in the JOHNSON-COOK model are back-calculated using different critical plastic shear *** adiabatic shear sensitivity decreases as initial static yield stress,work to heat conversion factor and strain-rate parameter decrease,which is opposite to the effects of density,heat capacity,ambient temperature and strain-hardening *** present model can predict the ASB width evolution *** predicted ASB width decreases with straining until a stable value is *** famous model proposed by DODD and BAI only can predict a final stable value.

关键词： adiabatic shear band Ti-6Al-4V JOHNSON-COOK model width gradient-dependent plasticity theory local plastic shear deformation distribution

Effects of Strain and Strain Rates on Microstructure Evolution Within ASB of TC4

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Acta Mechanica Solida Sinica 2024年第6期37卷 958-966页

作者： Qiang Zhou Qilin Xiong Zhaoquan Zeng Department of Mechanics School of Aerospace EngineeringHuazhong University of Science and Technology1037 Luoyu RoadWuhan430074China Hubei Key Laboratory of Engineering Structural Analysis and Safety Assessment 1037 Luoyu RoadWuhan430074China

adiabatic shear band(ASB),a typical failure mechanism in a metal at high strain rates,is hardly controllable or predictable to some *** development of the microstructure plays a crucial role in its *** this paper,the effect of strain rate on the development of microstructure in ASB of titanium alloy TC4 is investigated using hat-shaped specimens with the split-Hopkinson pressure bar *** results show that the fracture strength of TC4 is significantly dependent on the shear strain *** increase in fracture strength from a strain rate of 11,300 s^(−1)to 24,930 s^(−1)is much higher than that from 24,930 s^(−1)to 35,620 s^(−1),which can be attributed to the effect of strain rate on dislocation *** in both as-received and deformed states are investigated using various characterization techniques such as electron backscatter diffraction and X-ray *** region of ASB clearly shows three different microstructural features:random distribution of coarse grains(as received),distribution of elongated grains(transition zone),and distribution of equiaxed nanocrystals(shear-localized zone).The width of ASB increases with the strain *** possible reason for this is that the higher the strain rate,the larger the region where dynamic recrystallization(DRX)occurs due to the accumulation of a large number of *** the middle of ASB,a significant decrease in low-angle grain boundaries(LAGBs)and a large increase in high-angle grain boundaries are *** texture of specimens,especially the{11–20}and{10–10}planes,changes significantly during shear deformation at high strain *** mechanism of continuous dynamic recrystallization can well explain the formation and evolution of DRX within the ASB.

关键词： High strain rates Dynamic recrystallization adiabatic shear band Microstructure evolution TC4

Microstructural Characterization of the shear bands in Fe-Cr-Ni Single Crystal by EBSD

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Journal of Materials Science & Technology 2008年第6期24卷 819-828页

作者： Huajie YANG J.H.Zhang Yongbo XU Marc Andre＇ Meyers Shenyang National Laboratoryof Materials Sciences Institute of Metal Researchl Chinese Academy of Sciences Shenyang 110016 China University of California San Diego La Jolla CA92093-0411 USA

An investigation has been made into the microstructural characterization of the shear bands generated under high-strain rate （≈10^4 s^-1） deformation in Fe-15%Cr-15%Ni single crystal by EBSD-SEM （electron backscatter diffraction-scanning electron microscopy）, TEM （transmission electron in microscopy） and HREM （high- resolution electron microscopy）. The results reveal that the propagation of the shear band exhibits an asymmetrical behavior arising from inhomogenous distribution in plasticity in the bands because of different resistance to the collapse in different crystallographic directions; The γ-ε-α′phase transformations may take place inside and outside the bands, and these martensitic phases currently nucleate at intersections either between the twins and deformation bands or between the twins and ε-sheet. Investigation by EBSD shows that recrystallization can occur in the bands with a grain size of an average of 0.2μm in diameter. These nano-grains are proposed to attribute to the results of either dynamic or static recrystallization, which can be described by the rotational recrystallization mechanism. Calculation and analysis indicate that the strain rate inside the shear band can reach 2.50×10^6 s^-1, which is higher, by two or three orders of magnitude, than that exerted dynamically on the specimen tested.

关键词： High-strain rate deformation adiabatic shear band Electron backscatter diffraction (EBSD) Recrystallization Fe-Cr-Ni single crystal

The Anti-Penetration Performance and Mechanism of Metal Materials:A Review

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Engineering 2024年第9期40卷 131-157页

作者： Jialin Chen Shutao Li Shang Ma Yeqing Chen Yin Liu Quanwei Tian Xiting Zhong Jiaxing Song State Key Laboratory of Target Vulnerability Assessment Beijing 100036China Institute of Defense Engineering Academy of Military SciencePLABeijing 100036China Xi’an Rare Metal Materials Institute Co. Ltd.Xi’an 710016China

This article reviews the anti-penetration principles and strengthening mechanisms of metal materials,ranging from macroscopic failure modes to microscopic structural characteristics,and further summarizes the micro-macro correlation in the anti-penetration ***,it outlines the constitutive models and numerical simulation studies utilized in the field of impact and *** the macro perspective,nine frequent penetration failure modes of metal materials are summarized,with a focus on the analysis of the cratering,compression shear,penetration,and plugging stages of the penetration *** reasons for the formation of adiabatic shear bands(ASBs)in metal materials with different crystal structures are elaborated,and the formation mechanism of the equiaxed grains in the ASB is *** the strength and the toughness of metal materials are related to the materials’crystal structures and *** toughness is mainly influenced by the deformation mechanism,while the strength is explained by the strengthening ***,the mechanical properties of metal materials depend on their microstructures,which are subject to the manufacturing process and material *** numerical simulation,the advantages and disadvantages of different constitutive models and simulation methods are summarized based on the application characteristics of metal materials in high-speed penetration *** summary,this article provides a systematic overview of the macroscopic and microscopic characteristics of metal materials,along with their mechanisms and correlation during the anti-penetration and impact-resistance processes,thereby making an important contribution to the scientific understanding of anti-penetration performance and its optimization in metal materials.

关键词： Metal materials Failure model adiabatic shear band Strengthening mechanisms Numerical simulation