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Microstructure and mechanical properties stability of pre-hardening treatment in Al-Cu alloys for pre-hardening forming process

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International Journal of Minerals,Metallurgy and Materials 2024年第3期31卷 539-551页

作者： Liping Tang Pengfei Wei zhili hu Qiu Pang hubei Longzhong laboratory Xiangyang 441000China hubei Key Laboratory of Advanced Technology for Automotive Components School of Automotive EngineeringWuhan University of TechnologyWuhan 430070China hubei Engineering Research Center for Green&Precision Material Forming Wuhan University of TechnologyWuhan 430070China Key Laboratory of Metallurgical Equipment and Control Technology of Ministry of Education School of Machinery and AutomationWuhan University of Science and TechnologyWuhan 430081China

The stability of the microstructure and mechanical properties of the pre-hardened sheets during the pre-hardening forming(PHF)process directly determines the quality of the formed *** microstructure stability of the pre-hardened sheets was in-vestigated by differential scanning calorimetry(DSC),transmission electron microscopy(TEM),and small angle X-ray scattering(SAXS),while the mechanical properties and formability were analyzed through uniaxial tensile tests and formability *** results in-dicate that the mechanical properties of the pre-hardened alloys exhibited negligible changes after experiencing 1-month natural aging(NA).The deviations of ultimate tensile strength(UTS),yield strength(YS),and sheet formability(Erichsen value)are all less than 2%.Also,after different NA time(from 48 h to 1 month)is applied to alloys before pre-hardening treatment,the pre-hardened alloys possess stable microstructure and mechanical properties as ***,with the extension of NA time before pre-hardening treatment from 48 h to 1 month,the contribution of NA to the pre-hardening treatment is *** a yield strength increment of 20 MPa is achieved,with no loss in *** limited enhancement is mainly attributed to the fact that only a limited number of clusters are transformed into Guinier-Preston(GP)zones at the early stage of pre-hardening treatment,and the formation ofθ''phase inhibits the nucleation and growth of GP zones as the precipitated phase evolves.

关键词： Al-Cu alloy pre-hardened alloy natural aging mechanical properties microstructure

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Graphene binding on black phosphorus enables high on/off ratios and mobility

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National Science Review 2024年第2期11卷 188-195页

作者： Fanrong Lin Zhonghan Cao Feiping Xiao Jiawei Liu Jiabin Qiao Minmin Xue zhili hu Ying Liu huan Lu Zhuhua Zhang Jens Martin Qingjun Tong Wanlin Guo Yanpeng Liu Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education State Key Laboratory of Mechanics and Control of Mechanical Structures and Institute for Frontier Science Nanjing University of Aeronautics and Astronautics Centre for Advanced 2D Materials National University of Singapore School of Physics and Electronics Hunan University Centre for Quantum Physics Key Laboratory of Advanced Optoelectronic Quantum Architecture and MeasurementSchool of PhysicsBeijing Institute of Technology Leibniz Institute für Kristallzüchtung

Graphene is one of the most promising candidates for integrated circuits due to its robustness against short-channel effects, inherent high carrier mobility and desired gapless nature for Ohmic contact, but it is difficult to achieve satisfactory on/off ratios even at the expense of its carrier mobility, limiting its device applications. Here, we present a strategy to realize high back-gate switching ratios in a graphene monolayer with well-maintained high mobility by forming a vertical heterostructure with a black phosphorus multi-layer. By local current annealing, strain is introduced within an established area of the graphene, which forms a reflective interface with the rest of the strain-free area and thus generates a robust off-state via local current depletion. Applying a positive back-gate voltage to the heterostructure can keep the black phosphorus insulating, while a negative back-gate voltage changes the black phosphorus to be conductive because of hole accumulation. Then, a parallel channel is activated within the strain-free graphene area by edge-contacted electrodes, thereby largely inheriting the intrinsic carrier mobility of graphene in the on-state. As a result, the device can provide an on/off voltage ratio of >10～3 as well as a mobility of ～8000 cm2V-1s-1at room temperature, meeting the low-power criterion suggested by the International Roadmap for Devices and Systems.

关键词： graphene on/off ratio mobility black phosphorus reflective interface

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基于自抗扰扭矩分配算法的伺服凸轮式压力机双电机同步控制

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锻压技术 2024年第3期49卷 161-170页

作者：牛志存汪锐胡志力湖北隆中实验室湖北襄阳441022 武汉理工大学现代汽车零部件技术湖北省重点实验室湖北武汉430070 武汉理工大学材料绿色成形技术与装备湖北省工程中心湖北武汉430070

为解决伺服凸轮式压力机由于传动偏载或扭矩分配不均产生的传动系统严重的非线性振动问题,提出在凸轮轴两端各采用一个伺服电机实现双电机同步驱动来提高凸轮-滚子传动系统的可靠性,并提出基于自抗扰扭矩分配算法的交叉耦合同步控制策略... 详细信息

为解决伺服凸轮式压力机由于传动偏载或扭矩分配不均产生的传动系统严重的非线性振动问题,提出在凸轮轴两端各采用一个伺服电机实现双电机同步驱动来提高凸轮-滚子传动系统的可靠性,并提出基于自抗扰扭矩分配算法的交叉耦合同步控制策略,该策略将双电机的速度同步误差输入至同步控制器,通过权值变化规律调整权值,直至达到性能指标要求。仿真结果表明:与传统交叉耦合控制系统相比,基于自抗扰扭矩分配算法的同步控制策略的抗干扰能力强、跟踪响应速度快、同步控制精度更高、达到速度同步的时间更短,位置同步误差小于0.02 mm。仿真结果不仅验证了伺服凸轮式压力机双电机同步驱动策略的有效性,还为解决伺服凸轮式压力机的控制问题提供了可行方案。

关键词：伺服凸轮式压力机双电机同步控制交叉耦合自抗扰控制扭矩分配

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Curvature-Driven Forces Based on Natural Exponential Pair Potential at Micro/Nanoscales

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Acta Mechanica Solida Sinica 2019年第2期32卷 133-147页

作者： Dan Wang Yajun Yin Zheng Zhong zhili hu State Key Laboratory of Mechanics and Control of Mechanical Structures College of Aerospace Engineering Nanjing University of Aeronautics and Astronautics Nanjing 211100 China Department of Engineering Mechanics School of Aerospace Tsinghua University Beijing 100084 China School of Aerospace Engineering and Applied Mechanics Tongji University Shanghai 200092 China

The natural exponential potential (Ce^R/λ0) widely exists at micro/nanoscales;this paper studies the interaction potential between a curved-surface body and an outside particle base on the natural exponential potential. Mat hematical derivation proves t hat the int er act ion potential can be expressed as a function of curvatures. Then, idealized numerical experiments are designed to verify the accuracy of the curvature-based potential. The driving forces exerted on the particle are discussed and confirmed to be a function of curvatures and the gradient of curvatures, which may explain some abnormal movements at micro/nanoscales.

关键词： Micro/nanoscales Curvature-driven forces Natural exponential pair potential Curvature-based potential

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An analog of Friedel oscillations in nanoconfined water

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National Science Review 2022年第9期9卷 204-211页

作者： Minmin Xue zhili hu hu Qiu Chun Shen Wanlin Guo Zhuhua Zhang Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education State Key Laboratory of Mechanics and Control of Mechanical Structures and Institute for Frontier Science Nanjing University of Aeronautics and Astronautics

Water confined in nanometer-scale crevices and cavities underpins a wide range of fundamental processes,such as capillary flow,ion transport and protein ***,how water responds within these confined spaces,with prevalent inhomogeneity built in or caused by impurities,is not well ***,we show theoretically that water confined in one-dimensional nano channels with localized perturbation exhibits pronounced density *** oscillations occur vividly like the Friedel oscillations in electron density resulting from defects in metals.A model analysis reveals that the density oscillations result from the perturbation-induced molecular scattering that is augmented by the confinement-enhanced correlation of water *** renders the oscillations a general behavior independent of the channel geometries and specific forms of the *** confinements comparable to biological ion channels,such oscillations can strikingly extend over 10 nm,resulting in non-trivial effects at large distances that,for example,repel all ions from the channels with their long-range *** results deepen the understanding of biological functions and inspire new applications in a variety of domains,such as ionic sensing and seawater desalination.

关键词： ion sieving Friedel oscillations confined water water transport

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Failure Mechanisms and Structural Optimization of Shredder Hammer for Metal Scraps

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Chinese Journal of Mechanical Engineering 2016年第4期29卷 792-801页

作者： ZHOU Xianyan hu zhili TAO Yijun QIN Xunpeng huA Lin hubei Key Laboratory of Advanced Technology for Automotive Components Wuhan University of Technology Wuhan 430070 China hubei Lidi Machine Tool Company Limited Yichang 443000 China

Recycling retired cars can relieve the environmental pollution and resource waste ***,a few publications can be found on the failure mechanisms and optimization method of recycling equipment,***,the failure mechanisms and structural optimization of shredder hammers for retired cars are studied aiming improving shredding efficiency and reducing *** types of shredder hammer are studied theoretically,and it is found that wear failure and fatigue failure are the two main failure types of shredder *** shredding process of metal scraps is analyzed by finite element method,and it can be divided into four stages based on the stress states：initial stage,collision stage,grinding stage and separation *** is proved that the shredding efficiency can be improved by increasing cutouts on the hammer ***,it is determined that the hammer with two cutouts is the optimal structure for metal scraps,which can improve the shredding efficiency by 20% and lengthen the hammer life by 15%.This study provides scientific basis for the industry application and theoretical foundation for further research.

关键词： Metal scraps recycling impacts grinding structural optimization

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Surface evolution caused by curvature driven forces based on natural exponential pair potential

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Acta Mechanica Sinica 2019年第2期35卷 445-456页

作者： Dan Wang Yajun Yin Zheng Zhong Zhu Su zhili hu State key laboratory of mechanics and control of mechanical structures College of Aerospace Engineering Nanjing University of Aeronautics and Astronautics Nanjing 211100 China Department of Engineering Mechanics School of Aerospace Tsinghua University Beijing 100084 China School of Aerospace Engineering and Applied Mechanics Tongji University Shanghai 200092 China

Based on the natural exponential pair potential, the interaction potential between curved surface body and on surface particle is studied. Firstly, the interaction potential is written as a function of curvatures through the differential geometry. Secondly, idealized numerical experiments are designed to test the accuracy of curvature-based potential. Then, the driving forces induced by curvatures are analyzed, which confirms that micro/nano curved surface body can induce driving forces, curvatures and the gradient of curvatures are the essential elements forming the driving forces. Finally, by combing with the curvature based potential and driving forces, the movements of on surface particles and the evolution of surface morphology of curved surface body are predicted.

关键词： Curvature-based potential Curvatures and the gradient of curvatures Driving forces Surface morphology evolution

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Aligned Ni nanowires towards highly stretchable electrode

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Science China(Technological Sciences) 2020年第10期63卷 2131-2136页

作者： LI JiDong NIU JiYuan LI XueMei ZHOU JianXin hu zhili GUO WanLin State Key Laboratory of Mechanics and Control of Mechanical Structures The Key Laboratory of Intelligent Nano Materials and Devices of DoEInstitute of Nano Science of Nanjing University of Aeronautics and AstronauticsNanjing 210016China

Easy fabrication of super-stretchable electrodes can pave the way for smart and wearable *** drop casting unidirectional nickel nanowires with polyurethane matrix,we fabricated a super-stretchable film with high electric *** as-fabricated film can withstand a 300%tensile strain in the direction perpendicular to nanowires,owing to the transformation of percolating nanowire network from 2D to *** contrast to the decreased film conductivities under large tension in most stretchable electrodes,which usually associate with fractures and irreversible deformations,our film conductivity can increase with the applied *** probably benefits from the enhanced electrical contacts between twisted nanowires under *** developed super-stretchable film with unprecedented behavior in this work sheds light on the facile fabrication of super-stretchable electrodes with durable performance.

关键词： nickel nanowire stretchable electrode polyurethane matrix three-dimensional network alignment

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Interface-induced warping in hybrid two-dimensional materials

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Nano Research 2015年第6期8卷 2015-2023页

作者： John M. Aired Zhuhua Zhang zhili hu Boris I. Yakobson Department of Material Science and Nanoengineering Rice University Houston Texas 77005 USA

Two-dimensional hybrid materials consisting of heterogeneous domains have been of great interest. Using empirical molecular dynamical simulation, we show that the morphology of such hybrid 2D materials can extend into the third dimension via strong warping intrinsic to the interfaces between the domains. The interface warping stems from the compressive stress in the domain with a larger lattice constant and even penetrates into the stretched domain. Based on classic plate theory, we analytically quantify the amplitude, wave length and penetration depth of the interface warping as functions of the lattice mismatch, achieving good agreement with the simulations. Moreover, we propose that periodically placing pentagon-heptagon dislocations along the interface can eliminate the warping in the 2D material and such defective interface can be more favorable than the warped one over a critical domain size, which is consistent with recent experimental observations. Our results suggest that the interface warping in 2D hybrid materials should be considered in further exploring their promising properties.

关键词： graphene interface rippling mechanical property hybrid 2D materials

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Joining Performance and Microstructure of the 2024/7075 Aluminium Alloys Welded Joints by Vaporizing Foil Actuator Welding

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Journal of Wuhan University of Technology(Materials Science) 2019年第2期34卷 368-372页

作者：孟正华 WANG Xu GUO Wei hu zhili Anupam Vivek huA Lin Glenn S DAEHN hubei Key Laboratory of Advanced Technology for Automotive Components Wuhan University of Technology State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body Hunan University Department of Materials Science and Engineering The Ohio State University

Vaporizing foil actuator welding(VFAW) was used for joining 2024-T3 and 7075-T6 aluminum alloy sheets, and the resulting joint microstructure was analyzed. 2024/7075 aluminum alloy pairs with suitable processing parameters can be prepared by using VFAW. Dynamic preform addresses the poor formability problem of target material and advantage of VFAW on dissimilar materials in some conditions. But with standoff sheet inserting in the flyer and target, 2024/7075 welded pairs gets the better weld strength, compared with flyer preformed method. The microstructure of the circular weld area of the welded joint showed a wave interface, in which a thin melt layer formed at the center and edge parts. The crystal grains near the bonding interface were remarkably elongated and refined. Therefore, the joining of the 2024/7075 pairs was facilitated through plastic forming and melting.

关键词： impact welding dissimilar materials vaporizing foil actuator joining interface

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