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Isolation performances and optimization of triple quasi-zero stiffness isolators

Science China(Physics,Mechanics & Astronomy) 2024年第7期67卷 124-141页

作者： yuntian Zhang Guangnan zhu Qingjie Cao School of Astronautics Harbin Institute of TechnologyHarbin 150001China

In this paper,triple quasi-zero stiffness(QZS)passive vibration isolators whose restoring force curve has a three-stage softening effect are proposed.Multi-coupled SD oscillators with three independent geometrical parameters are used as negative stiffness mechanisms to achieve QZS characteristics at the origin and symmetrical positions on both sides of the origin.Isolation performances of different triple QZS isolators are analyzed to show influences of the selection of QZS regions away from the origin on the range of isolation regions.Pareto optimizations of system parameters are carried out to get a larger range of small restoring force regions and small stiffness regions.Isolation performances of two triple QZS isolators are discussed to show the influence of different Pareto optimization solutions through the comparisons with single and double QZS isolators.Results showed that triple QZS isolators have both the advantages of single and double QZS isolators which results in better isolation performances under both small and large excitation amplitudes.An improvement in isolation performances for triple QZS isolators is found with the decrease in average stiffness due to the appearance of two symmetrical QZS regions away from the origin.Larger displacements of QZS regions away from the origin result in better isolation performances when excitation amplitude is large,and triple QZS characteristics are similar to double QZS isolators at this time.Smaller restoring forces of QZS regions away from the origin lead to better isolation performances when excitation amplitude is small,and triple QZS characteristics are similar to single QZS isolators at this moment.Compared with the decrease in average stiffness,the improvement of isolation performances shows a hysteresis phenomenon due to the difference between static and dynamic characteristics.

关键词： triple quasi-zero stiffness vibration isolation Pareto optimization force transmissibility geometrical nonlinear

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Transient synthesis of carbon-supported high-entropy alloy sulfide nanoparticles via flash Joule heating for efficient electrocatalytic hydrogen evolution

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Nano Research 2024年第4期17卷 3379-3389页

作者： yuntian Liao Rongtao zhu Wenjun Zhang Haiyang zhu Yang Sun Jiale Chen Zhenhua Dong Ronghuan Lv School of Chemical Engineering and Technology China University of Mining and TechnologyXuzhou 221116China

High entropy alloys(HEA)are frequently employed as catalysts in electrocatalytic hydrogen evolution.However,the traditional high entropy alloy synthesis methods are time-consuming,energy-intensive,and environmentally polluting,which limits their application in the hydrogen evolution reaction(HER).This study leveraged the capabilities of flash Joule heating(FJH)to synthesize carbon-supported high-entropy alloy sulfide nanoparticles(CC-S-HEA)on carbon cloth(CC)with good self-standing properties within 300 ms.The carbon thermal shock generated by the Joule heating could pyrolyze the sulfur source into gas,resulting in numerous pore structures and defects on CC,forming an S-doped carbon substrate(CC-S).Then the S atoms were used to stably anchor the metal atoms on CC-S to form high-density uniformly dispersed HEA particles.The electrochemical test results demonstrated that CC-S-HEA prepared at 60 V flash voltage had HER performance comparable to Pt/C.The density functional theory(DFT)calculation indicated that the S atoms on CC-S accelerated the electron transfer between the carbon substrate and HEA particles.Moreover,the unique electronic structure of CC-S-HEA was beneficial to H*adsorption and promoted catalytic kinetics.The simplicity and versatility of FJH synthesis are of great significance for optimizing the synthesis of HEA and improving the quality of HEA products,which provides a broad application prospect for the synthesis of nanocatalysts with efficient HER performance.

关键词： high entropy alloy flash Joule heating carbon thermal shock hydrogen evolution reaction density functional theory

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Hierarchical strain band formation and mechanical behavior of a heterostructured dual-phase material

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Journal of Materials Science & Technology 2023年第31期162卷 25-37页

作者： Zhongkai Li Yujie Liu Yanfei Wang Jun Hu Lei Xu Jianjun Wang Chunming Liu yuntian zhu Key Laboratory for Anisotropy and Texture of Materials of Ministry of Education Northeastern UniversityShenyang 110819China Department of Mechanics and Engineering Science College of EngineeringPeking UniversityBeijing 100871China The State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang 110819China Shi-Changxu Innovation Center for Advanced Materials Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China Department of Materials Science and Engineering City University of Hong KongHong KongChina

Dispersive strain bands have been reported as a characteristic deformation feature of heterostructured materials,which helps to improve ductility.However,their formation mechanism is still not well understood.Here we report the formation of dispersed strain bands through dual-level hierarchical strain banding and its effect on the mechanical behavior of a heterostructured Fe-40Cu model material.Specifically,deformation started by the formation and propagation of dispersed microscale strain bands in the heterostructured Fe-40Cu material.High strain gradient was generated within the microscale strain bands during their propagation and was accommodated by the accumulation of geometrically necessary disloca-tions(GNDs).The dispersed microscale strain bands were not uniformly distributed,but instead grouped together to form macroscale strain bands that were uniformly distributed over the entire gage section to accommodate the majority of the applied strain.The formation of this dual-level hierarchical strain bands prevented the formation of large strain localization to fail the sample prematurely.It was also found that increasing the strain hardening capacity of soft copper zones provides more room for the accumulation of GNDs,resulting in higher constraint to microscale strain band propagation and consequently higher ductility.These observations suggest the possibility of tailoring microscale strain bands to optimize tensile performance of heterostructured materials.

关键词： Heterostructured materials Strain bands Strain gradient Hetero-deformation induced hardening

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Unexpected high-temperature brittleness of a Mg-Gd-Y-Ag alloy

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Journal of Magnesium and Alloys 2022年第9期10卷 2510-2515页

作者： Lirong Xiao Xuefei Chen Huiyan Ning Ping Jiang Yi Liu Bin Chen Dongdi Yin Hao Zhou yuntian zhu Nano and Heterogeneous Materials Center School of Materials Science and EngineeringNanjing University of Science and TechnologyNanjing 210094China State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Mechanical and Electrical Engineering Heilongjiang Institute of TechnologyHarbin 150050China ThermoFisher Scientific Shanghai 201210China Key Laboratory of Advanced Technologies of Materials Ministry of EducationSchool of Materials Science and EngineeringSouthwest Jiaotong UniversityChengduSichuan 610031China Department of Materials Science and Engineering City University of Hong KongHong Kong 999077China

Rare earth(RE)can produce excellent precipitation hardening in Mg alloys.However,when forming a solid solution,it also deteriorates formability,a problem that can usually be overcome by raising deformation temperature.Here we report an unexpected observation of high temperature brittleness in a Mg-Gd-Y-Ag alloy.As the temperature reached 500℃,the formability decreased drastically,leading to severe intergranular fracture under only 0.5% strain.This was caused by failure of grain boundaries,which are weakened by segregated interfacial compounds.

关键词： Interfacial compounds Formability High temperature brittleness Grain boundary sliding

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Effect of texture on deformation behavior of heterogeneous Mg-13Gd alloy with strength-ductility synergy

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Journal of Materials Science & Technology 2022年第18期113卷 271-286页

作者： Shuaishuai Liu Han Liu Xiang Chen Guangsheng Huang Qin Zou Aitao Tang Bin Jiang yuntian zhu Fusheng Pan State Key Laboratory of Mechanical Transmission College of Materials Science and EngineeringChongqing UniversityChongqing 400044China National Engineering Research Center for Magnesium Alloys Chongqing UniversityChongqing400044China Department of Materials Science and Engineering City University of Hong KongHong Kong999077China Nano and Heterogeneous Material Center Nanjing University of Science and TechnologyNanjing210094China

Heterostructure metals as a new class of materials can effectively break the traditional strength–ductility trade-off dilemma. In this study, the extruded sheet with the small extrusion ratio(ER) of 3.9(ER3.9)presented a heterogeneous lamella structure(HLS) and texture, where the fine dynamical recrystallized(DRXed) grains formed a random texture and coarse un-DRXed grains exhibited a strong basal texture.The ER3.9 sample presented an excellent combination of strength and ductility. The texture strengthening in coarse grains and hetero-deformation induced(HDI) strengthening contributed to the enhanced strength of the ER3.9 sample besides grain refinement. The improving ductility mainly stems from the weakened texture in fine grains. Interestingly, in coarse grains, the strong basal texture, the occurrence of cross slip, low stacking fault energy(SFE), and dislocation pinned by precipitates weaken the HDI hardening effect. While the traditional dislocation hardening mainly generated by fine grains dominates overall strain hardening. Meanwhile, the activation of non-basal slips, especially pyramidal slip,and the generation of cross slips in fine grains benefit for coordinating plastic deformation. The ability for coordinate plastic deformation in fine grains is higher than that of coarse grains, which was confirmed by the digital image correlation technology. This work will promote the development of the heterogeneous theory in textured Mg alloys.

关键词： Mg-Gd alloy Recrystallization Heterogeneous texture Mechanical properties HDI hardening

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Effect of interstitial carbon and nitrogen on corrosion of FeCoCrNi multi-principal element alloys made by selective laser melting

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Journal of Materials Science & Technology 2023年第17期148卷 52-63页

作者： Wenyu Chen Rui Zhou Wanpeng Li Yen-Hsiang Chen Tzu-Hsiu Chou Xu Wang Yong Liu yuntian zhu J.C.Huang Department of Materials Science and Engineering Hong Kong Institute for Advanced StudyCity University of Hong KongKowloonHong KongChina Mechanical Behavior Division of Shenyang National Laboratory for Materials Science City University of Hong KongKowloonHong KongChina School of Mechanical Engineering Liaoning Shihua UniversityFushun 113001China State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083China Department of Materials and Optoelectronic Science National Sun Yat-Sen UniversityKaohsiung 804TaiwanChina

The corrosion behaviors of selective laser melted(SLMed)FeCoCrNi multi-principal element alloys(MPEAs)with carbon or nitrogen addition in 0.5 M H_(2)SO_(4) solution were investigated.Both C and N ad-dition refined the grains and introduced a heterogeneous structure in SLMed FeCoCrNi MPEA,but they had opposite effects on the corrosion behavior.The doped carbon participated as nano-sized carbides in SLMed MPEA,and localized galvanic corrosion occurred,degrading the corrosion resistance.The doped nitrogen was gathered with chromium and formed CrN chemical clusters in SLMed MPEA,and a protec-tive passive film with a higher Cr_(2)O_(3)/Cr(OH)_(3) ratio formed,which improved corrosion resistance.

关键词： Selective laser melting Interstitial element Multi-principal element alloys Acid corrosion

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Catch twin nucleation in action at atomic scale

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Science China Materials 2018年第7期61卷 1019-1020页

作者： yuntian zhu School of Materials Science and Engineering North Carolina State University

Understanding the deformation mechanisms of nano-crystalline （nc） metals at the atomic-scale is crucial fordetermining how far the strengths of metals can be ulti-mately reached. Although several breakthroughs haveb... 详细信息

关键词：材料科学研究

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Hardening after annealing in nanostructured 316L stainless steel

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Nano Materials Science 2020年第1期2卷 80-82页

作者： Zhongchen Zhou Shuaizhuo Wang Jiansheng Li Yusheng Li Xiaolei Wu yuntian zhu Nano and Heterogeneous Materials Center School of Materials Science and EngineeringNanjing University of Science and TechnologyNanjing210094China State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of SciencesBeijing100190China Department of Materials Science and Engineering North Carolina State UniversityRaleighNC27695USA

In this work,coarse-grained 316 L stainless steels were cold rolled with a thickness reduction of^83%(CR 83%).After annealing,the behaviors of the nanostructured stainless steel samples were systematically investigated in the temperatures range of 200C–650C.It was found that with increasing annealing temperature the volume fraction of theα0-martensite first increased to reach a maximum value at 400C,then the volume fraction decreased with further increases of the annealing temperature.The yield strength was increased from 1400 MPa to 1720 MPa after annealing;this strong hardening effect in cold rolled 316 L stainless steel was mainly attributed to the increase of the volume fraction ofα0-martensite.

关键词： Metals and alloys Nanostructure Heterostructure 316L stainless steel Annealing hardening Martensitic transformation

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福宁湾及附近海域悬沙粒度与影响因素

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海洋地质与第四纪地质 2024年第1期44卷 15-29页

作者：毕云天胡日军陈娟娟李毅伊兆晗陈晓磁朱龙海尹砚军刘波中国海洋大学海洋地球科学学院青岛266100 中国海洋大学海底科学与探测技术教育部重点实验室青岛266100 华能霞浦核电有限公司宁德352100

基于闽北福宁湾及附近海域冬、夏两季水文泥沙实测数据,分析了不同时间尺度下悬沙的粒度特征,探讨了影响悬沙粒度季节差异的主要因素以及悬沙粒度与浓度的关系。结果表明:正常天气下,研究区悬沙中值粒径普遍大于6.5Φ。悬沙粒度具有“... 详细信息

基于闽北福宁湾及附近海域冬、夏两季水文泥沙实测数据,分析了不同时间尺度下悬沙的粒度特征,探讨了影响悬沙粒度季节差异的主要因素以及悬沙粒度与浓度的关系。结果表明:正常天气下,研究区悬沙中值粒径普遍大于6.5Φ。悬沙粒度具有“冬细夏粗”的季节分布特征;受潮动力影响,悬沙粒度大小潮变化明显;潮周期内悬沙粒径变化规律不明显。悬沙粒级-标准偏差曲线显示两种主要的敏感粒级分布范围为2.8~3.4μm和21.1~25.1μm。悬沙粒度“冬细夏粗”的季节差异主要受底质再悬浮和泥沙来源的影响。冬季悬沙粒径与浓度的相关性不明显,夏季两者存在显著的线性关系,悬沙粒径随悬沙浓度的增加而减小,这种季节差异可能与悬沙来源和混合作用有关。夏季悬沙粒径的粗化可能与细颗粒发生絮凝沉降有关。

关键词：悬沙粒度时空变化季节差异影响因素福宁湾

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妊娠期糖尿病剖宫产产妇采用术前禁饮禁食时间合理缩减模式的效果

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实用妇科内分泌电子杂志 2024年第6期11卷 70-72页

作者：朱雨竹李莉姜巍郭凤英赵云田长春市妇产医院麻醉科吉林长春130000 长春市妇产医院医务科吉林长春130000

目的探究妊娠期糖尿病剖宫产产妇采用术前禁饮禁食时间合理缩短模式的效果。方法选择行剖宫产术的妊娠期糖尿病产妇104例为研究对象,根据入院先后顺序分为对照组(52例)及研究组(52例)。对照组采用常规术前禁饮禁食,研究组采用术前禁饮... 详细信息

目的探究妊娠期糖尿病剖宫产产妇采用术前禁饮禁食时间合理缩短模式的效果。方法选择行剖宫产术的妊娠期糖尿病产妇104例为研究对象,根据入院先后顺序分为对照组(52例)及研究组(52例)。对照组采用常规术前禁饮禁食,研究组采用术前禁饮禁食时间合理缩减模式。对比两组产妇的临床指标、术前低血糖及新生儿低血糖发生情况。结果研究组术中出血量、术后排气时间均少于对照组,差异有统计学意义(P<0.05)。研究组产妇术前低血糖发生率、新生儿低血糖发生率分别为1.92%、1.92%,均低于对照组的15.38%、13.46%,差异有统计学意义(P<0.05)。结论将术前禁饮禁食时间合理缩短模式应用于妊娠期糖尿病剖宫产产妇中,可有效减少其术中出血量,促进术后尽早排气,并降低产妇术前低血糖及新生儿低血糖的发生风险,值得推广。

关键词：妊娠期糖尿病禁饮禁食应用效果

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