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Size Effect on Onset and Subsequent Evolution of Adiabatic Shear Band:Theoretical and Numerical Analysis

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

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Effect of impact deformation on shape recovery behavior in Fe-Mn-Si shape memory alloy under shape memory training process with cyclic thermo-mechanical loading

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Science China(Technological Sciences) 2021年第7期64卷 1389-1400页

作者： SUN Qian CAO Bo IWAMOTO Takeshi suo tao Graduate School of Engineering Hiroshima UniversityHigashi-Hiroshima739-8527Japan Cluster of Excellence livMatS@FIT-Freiburg Center for Interactive Materials and Bioinspired Technologies University of FreiburgFreiburgD-79110Germany Academy of Science and Technology Hiroshima UniversityHigashi-Hiroshima739-8527Japan School of Aeronautics Northwestern Polytechnical UniversityXi’an710072China

In the past studies, it has been discovered that the shape memory effect(SME) in the Fe-Mn-Si shape memory alloy(Fe-SMA)can gradually be enhanced by a pre-process called as shape memory training process under cyclic thermo-mechanical *** the other hand, it has been shown that the SME of Fe-SMA can also be affected by changing the strain rate. Therefore, it is possible to improve the SME by combining the strain rate sensitivity and shape memory training process. However, the improvement of SME caused by the training process under impact condition is still unclear. For the training process under impact condition, it is difficult to interrupt the test at the desired strain level due to many reflections of stress waves, which reload the specimen from the free ends. In this paper, to obtain reliable experimental results of SME after the training process under impact condition, the stress waves after first loading are eliminated by the double momentum-trap structure introduced into the impact tensile testing apparatus based on the split Hopkinson pressure bar method. In order to achieve an optimum design of the structure used in experiments, the finite element simulation of the structure is performed. Then, tensile tests in the training process of Fe-28Mn-6Si-5Cr alloy at different strain rates including the impact level are conducted and temperature change of the specimen is measured during training and heating process. As a result, the improvement of SME in the alloy after the training process under quasi-static and impact loading is compared with that under quasi-static loading through verification processes.

关键词： Fe-Mn-Si shape memory alloy training cyclic thermo-mechanical process split Hopkinson pressure bar momentumtrap impact deformation

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Detonation driving rules for cylindrical casings under asymmetrical multipoint initiations

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Defence Technology（防务技术） 2023年第5期23卷 35-49页

作者： Yuan Li Xiaogang Li Yuquan Wen tao suo Institute of Extreme Mechanics and School of Aeronautics Northwestern Polytechnical UniversityXi'an710072China State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing100081China

The detonation wave-aiming warhead can effectively enhance the lethality efficiency. In the past, rules for casing rupture and velocity distribution under asymmetrical initiations were not adequately investigated. In this study, X-ray photography and numerical modelling are used to examine the casing expansions under centre point, asymmetrical one-point, and asymmetrical two-point(with central angles of 45° and 90°) initiations. The results indicate that early casing ruptures are caused by local high pressures, induced by the initiation, detonation wave interaction, and Mach wave onset. The fragment shapes are controlled by the impact angle of the detonation wave. The fragment velocity distributions differ under different initiation types, and the end rarefaction waves can affect the velocity *** study can serve as a reference for the design and optimization of high-efficiency warheads.

关键词： Multipoint initiation Fragment shape Velocity distribution X-ray photography

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DYNAMIC MECHANICAL BEHAVIOR OF 6061 AL ALLOY AT ELEVATED TEMPERATURES AND DIFFERENT STRAIN RATES

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Acta Mechanica Solida Sinica 2013年第2期26卷 111-120页

作者： Xueling Fan tao suo Qin Sun Tiejun Wang State Key Laboratory for Strength and Vibration of Mechanical Structures School of Aerospace EngineeringXi'an Jiaotong University School of Aeronautics Northwestern Polytechnical University

The compressive stress-strain relationships of 6061A1 alloy over wide temperatures and strain rates are investigated. The dynamic impact experiments are performed using an im- proved high temperature split Hopkinson pressure bar apparatus. The experimental results are compared with those obtained by the modified Johnson-Cook constitutive model. It is found that the dynamic mechanical behavior depends sensitively on temperature under relatively low strain rates or on strain rate at relatively high temperatures. The good agreement indicates that it is valid to adopt the parameter identification method and the constitutive model to describe and predict the mechanical response of materials.

关键词： dynamics plastic high temperature alloy impact testing

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High-velocity impact responses of 2618 aluminum plates for engine containment systems under combined actions of projectile form and oblique angle

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Chinese Journal of Aeronautics 2019年第6期32卷 1428-1441页

作者： Cunxian WANG tao suo Yulong LI Pu XUE Zhongbin TANG School of Aeronautics Northwestern Polytechnical UniversityXi’an 710072China Shaanxi Key Laboratory of Impact Dynamics and Engineering Application(IDEA) Northwestern Polytechnical UniversityXi’an 710072China Fundamental Science on Aircraft Structural Mechanics and Strength Laboratory Northwestern Polytechnical UniversityXi’an 710072China

Ballistic impact tests were carried out with examined projectiles of the Ti-6Al-4V titanium alloy to investigate the impact response of the 2618 aluminum plates at a nominal velocity of 210 m/s. The influence of projectile forms and oblique angles on damage formation was particularly discussed by applying different loading conditions such as multiple projectile forms and oblique angles. Additionally, the numerical simulation method was employed to provide further insight into the characteristics of damage and target responses. The Johnson-Cook(J-C)constitutive model with revised failure parameters was used to support the simulations to assess target responses and characteristics of the damage created from different impact conditions. Results show that there is a significant transition in the deformation mode as changes of the projectile form are applied. Moreover, the cracks on the back of the 2618 aluminum alloy plates impacted by the solid plate projectile and the hollow blade projectile tend to locate at different positions, which are supposed to be influenced by local bending and stretching. The work in this paper may provide guidance for the design of fan blade containment systems.

关键词： 2618 aluminum plate Damage characteristic High-velocity impact Johnson-Cook(J-C) Projectile forms

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TEMPERATURE SENSITIVITY AND PREDICTION OF THE MECHANICAL BEHAVIORS OF ULTRAFINE GRAINED ALUMINUM UNDER UNIAXIAL COMPRESSION

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Acta Mechanica Solida Sinica 2014年第4期27卷 373-382页

作者： Quanwei Zhan tao suo Cunxian Wang Kui Xie Zhongbin Tang Institute of UAV research Northwestern Polytechnical University School of Aeronautics Northwestern Polytechnical University Department of Mechanical Engineering The Johns Hopkins University 3400 N. Charles StreetBaltimore MD 21218 USA China Electronics Technology Group Corporation No.38 Research Institute

In the present work, we explore the strain hardening behaviors as well as the effect of temperature on the plastic deformation of ultrafine grained aluminum. The temperature sensitivity is determined and compared with that of coarse grained material. The results indicate that the flow stress of ultrafine grained aluminum displays enhanced sensitivity to temperature. The reduction in activation volume is suggested to be the major reason for the enhanced temperature sensitivity as grain size is refined into the sub-micrometer regime. Finally, a phenomenological constitutive model is proposed to describe the post-yield response of ultrafine grained aluminum.

关键词： ultrafine grained aluminum compressive behavior temperature sensitivity strain hardening behavior constitutive relation

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A novel subset assignment and matching method for DIC measurement of complex deformation in aircraft braking process

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Chinese Journal of Aeronautics 2024年第8期37卷 373-387页

作者： Xin SHI Xiang GUO tao suo Yingtao YUAN Hongli HE Zhiyong REN School of Aeronautics Northwestern Polytechnical UniversityXi’an 710072China International Research Laboratory of Impact Dynamics and its Engineering Application Xi’an 710072China Institute of Extreme Mechanics Northwestern Polytechnical UniversityXi’an 710072China Chinese Flight Test Establishment Xi’an 710089China

This paper proposes a measurement method related to the braking deformation of a complex *** the braking process,the deformation of the wheel includes large amounts of movement,vibration,warping,and distortion.A novel subset assignment and correlation method is proposed to measure the complex *** proposed method can greatly improve the accuracy and stability of the calculation of complex deformations by simplifying the complex deformation into translational deformations in logarithmic coordinate *** to the simulation and actual experiments,the proposed method can be utilized to measure the deformations of up to 100%tensile strain under complex *** to the accuracy verification experiment,the error of the proposed method is less than 50 *** results show that the proposed method can effectively carry out structural deformation measurement in the complex motion and deformation *** proposed method has great significance for structural performance analysis and optimization design considering complex motion and deformation.

关键词： Complex deformation Measurement Digital image correlation Aircraft braking Deformation field

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Temperature Effect on the Mechanical Behavior of Acrylic Polymers under Quasi-static and Dynamic Loading

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上海交通大学学报 2004年第z2期38卷 89-95页

作者： tao suo Yulong Li Hong Yu Fei Xu Zhongbin Tang Lei Li School of Aeronautics Northwestern Polytechnical University Xi''an710072 China School of Aeronautics Northwestern Polytechnical University Xi''an710072 China School of Aeronautics Northwestern Polytechnical University Xi''an710072 China School of Aeronautics Northwestern Polytechnical University Xi''an710072 China School of Aeronautics Northwestern Polytechnical University Xi''an710072 China Beijing Institute of Aeronautical Materials Beijing100095China

In this paper, the mechanical behavior of acrylic polymers at elevated temperature was investigated. Four acrylic polymers were tested at high strain rate by using compression Hopkinson bar and at quasi-static strain rate by using an Instron servo hydraulic axial testing machine with the testing temperature from 218K to 393K. The results show that the mechanical property of acrylic polymers depends heavily on the testing temperature. The yield stress and Young's modulus were found to decrease with increasing temperature at low strain rate. At very low temperature, the materials display typical brittle fracture; however their plasticity improves remarkably at high temperatures. The predictions of the mechanical behavior including the effect of temperature and strain rate using a proposed theoretical model have a good agreement with experimental results.

关键词： acrylic polymer compression Hopkinson bar quasi-static dynamic fracture

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Dynamic flexural strength of Aluminosilicate glass with a perspective of impulsive and quasi-impulsive responses: An experimental-numerical coupled evaluation

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Chinese Journal of Aeronautics 2024年第12期37卷 388-403页

作者： Muhammad Aamir RAZA tao suo Uzair Ahmed DAR Muhammad ATIF Muhammad Zakir SHEIKH School of Aeronautics and Institute of Extreme Mechanics Northwestern Polytechnical UniversityXi’an 710072China Joint International Research Center of Impact Dynamics and Its Engineering Application Northwestern Polytechnical UniversityXi’an 710072China Shaanxi Key Laboratory of Impact Dynamics and Engineering Application Northwestern Polytechnical UniversityXi’an 710072China National Key Laboratory of Strength and Structural Integrity Northwestern Polytechnical UniversityXi’an 710072China

The flexural strength of glass is a critical design parameter for applications encountering impact ***,the micro defects,specimen geometry,loading rate,and load transformation from a quasi-dynamic to quasi-impulsive state may influence the measurement *** to the stochastic and amorphous nature of the material,an accurate determination of the flexural strength remains a *** this two-fold study,a coupled experimental-numerical strategy was devised to evaluate the dynamic flexural *** the first phase,three-point bending experiments were conducted on a novel“Electromagnetic Split Hopkinson Pressure Bar(ESHPB)”.The incident stress signal and fracture time were recorded from experimental data,while the flexural strength was indirectly computed from a numerical algorithm.A quantitative comparison of the flexural strength with those in existing literature established the accuracy of the proposed *** of the study indicate that the specimen response became independent of the support conditions under impulsive *** being said,the specimen behaved like it had an infinite span length,and the measured flexural strength remained the same whether the specimen was supported or ***,the specimen also maintained contact at the interfaces of the incident bar and fixture supports for the entire loading *** the second part of this study,the computed flexural strength was used to calibrate the existing JH-2 *** prediction of the damage propagation corroborated with that obtained from reprography images,though *** work presents a precise and robust methodology to determine the dynamic flexural strength of brittle ceramics like Aluminosilicate glass over traditional experimental procedures to facilitate its adoption.

关键词： Dynamic flexural strength Damage mechanism Flexural fracture Numerical simulation Aluminosilicate glass

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Gradient structure induced simultaneous enhancement of strength and ductility in AZ31 Mg alloy with twin-twin interactions

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Journal of Magnesium and Alloys 2023年第8期11卷 2872-2882页

作者： Qinghui Zhang Jianguo Li Kun Jiang Pu Li Yusheng Li Yong Zhang tao suo 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 School of Materials Science and Engineering Nanjing University of Science and TechnologyNanjing 210094China School of Materials Science and Engineering Herbert Gleiter Institute of NanoscienceNanjing University of Science and TechnologyNanjing 210094China

Gradient nanostructure was introduced to enhance the strength and ductility via deformation incompatibility accommodated by geometrical necessary dislocations for most metallic materials ***,few intensive researches were carried out to investigate the effect of gradient structure on the deformation twin evolution and resulting performance *** the present paper,we produced gradient-structured AZ31 Mg alloy with fine-grain layers,parallel twin laminates and a coarse-grain core from two upmost surfaces to the center of ***,this architected Mg alloy exhibited simultaneous enhancement of strength and *** microstructural observations demonstrated that abundant twin-twin interactions resulting from higher strength and multi-axial stress state could make great contributions to the increase of work-hardening *** was further proved by the measurement of full-field strain evolution during the plastic *** a design strategy may provide a new path for producing advanced structure materials in which the deformation twinning works as one of the dominant plasticity mechanisms.

关键词： Mg alloy Gradient structure Strength-ductility synergy Multi-orientational twins Twin-twin interactions

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