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Applied Mathematics and Mechanics(English Edition) 2023年第4期44卷 623-640页

作者： h.S.LEE h.X.cao D.JUNG C.S.KIM School of Mechanical Engineering Chonnam National UniversityGwangju 61186South Korea Korea Institute of Medical Microrobotics Gwangju 61011South Korea

We present a novel motion control technique for microrobot clusters to exploit the characteristics of the ultrasonic *** method comprises two steps,i.e.,introducing an ultrasonic actuation(UA)linear model for three-dimensional(3D)locomotion and controlling the topological charge(TC)in the ultrasonic vortex for microrobot ***,the TC is a controllable parameter for the expansion and contraction of the pressure null space inside the *** present a TC control method to cluster sporadically distributed microrobots in a specific *** validate the concept,a UA system composed of 30 ultrasonic transducers with 1 Mhz frequency is fabricated,and the characteristics of the generated acoustic pressure field are analyzed through ***,the performances of the adaptive controller for precise 3D locomotion and the TC control method for clustering are ***,the UA technology,which performs both clustering and locomotion in a complex manner,is validated with a gelatin phantom in an in-vitro environment.

关键词： ultrasonic actuation(UA) topological charge(TC) adaptive control particle manipulation

Comparing hydrogen embrittlement behaviors of two press hardening steels:2 GPa vs.1.5 GPa grade

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Journal of Materials Science & Technology 2022年第29期124卷 109-115页

作者： Z.h.cao B.N.Zhang M.X.huang Department of Mechanical Engineering The University of Hong KongPokfulam RoadHong KongChina

*** The pursuit of advanced high-strength steels(AhSS)has been rising for the automobile industry to build lightweight and fuelefficient vehicles without compromising crashworthiness[1,2].The group of press hardening steels(PhS)is an excellent candidate that comprises high strength,high toughness,and good formability,which are optimal to build intrusion resistant components such as(ⅰ)A/B-pillar reinforcements,(ⅱ)bumper and door beams.

关键词： strength toughness steels

Review on hydrogen Embrittlement of Press-hardened Steels for Automotive Applications

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Acta Metallurgica Sinica(English Letters) 2023年第7期36卷 1123-1143页

作者： Z.Wang Q.Lu Z.h.cao h.Chen M.X.huang J.F.Wang General Motors China Science Lab Shanghai201206China Department of Mechanical Engineering The University of Hong KongPokfulam RoadHong Kong999077China Key Laboratory for Advanced Materials of Ministry of Education School of Materials Science and EngineeringTsinghua UniversityBeijing100084China

Press-hardened steel(PhS)with an ultimate tensile strength(UTS)of 1500 MPa has been widely used in automotive body-in-white in the last two decades,due to its ultra-high strength and excellent formability that is achieved by hot stamping ***,the application of PhS with UTS exceeding 1500 MPa in automotive industry could be deferred due to the increased risk of hydrogen *** reduce this kind of risk,recent research efforts have been focused on various ways to optimize the microstructure of *** present review intends to summarize these efforts,to highlight present solutions to address hydrogen embrittlement,and to shed light on directions for future *** influence of microstructure on the hydrogen embrittlement of PhS has been discussed in terms of both the steel substrate and the surface *** substrate part covers the influence of martensite,carbides,inclusions,and retained austenite,while the surface part covers decarburization and oxidation,pre-coating,and trimming.

关键词： hot stamping Press-hardened steels Coating-free hydrogen embrittlement Fracture Al-Si coating

EVOLUTION OF ThE ELECTROChEMICAL ChARACTERISTICS DURING PITTING CORROSION OF PURE ALUMINUM IN SODIUM ChLORIDE SOLUTION

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Acta Metallurgica Sinica(English Letters) 2005年第4期18卷 525-532页

作者： Z. Zhang C. Cai F.h. cao Z.N. Gao J.Q. Zhang C.N. cao Department of Chemistry Zhejiang University Hangzhou 310027 China Department of Chemistry Ningxia University Yinchuan 750021 China State Key Laboratory for Corrosion and Protection of Metals Institute of Metal Research The Chinese

The corrosion behavior of pure aluminum in neutral 3.0% （mass fraction） sodium chloride （Na-Cl） solution has been studied using electrochemical impedance spectroscopy （EIS） measurement in conjunction with the scanning electron microscopy （SEM） technique. EIS information on the evolution of pitting corrosion over a period of 15 days has been obtained and analyzed with equivalent circuit technique. The results shown that, during the ensemble constant immersion time, two time constants involved, the high frequency one originated from the protective layer on the corroding surface while the low frequenO, one from the diffusion process or the corrosion reaction and so on. And there existed a period for oxide film to growth and thickening prior to the of the attacking of chloride ions to the substrate. Meanwhile, good relationship between EIS and the material corrosion type/severity has been obtained, which has been interpreted according to the characteristics of corrosion process such as auto acceleration of pitting corrosion and the protection of local anodic reaction to the area around them.

关键词： pure aluminum pitting corrosion electrochemical impedance spectroscopy pit-rnorphology

Diameter-dependent in vitro performance of biodegradable pure zinc wires for suture application

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Journal of Materials Science & Technology 2019年第8期35卷 1662-1670页

作者： h. Guo R.h. cao Y.F. Zheng J. Bai F. Xue C.L. Chu State Key Laboratory for Turbulence and Complex System and Department of Materials Science and Engineering College of Engineering Peking University Beijing 100871 China School of Materials Science and Engineering Southeast University Nanjing 211189 China Key Laboratory for Advanced Metallic Materials Southeast University Nanjing 211189 China

In this study, biodegradable pure zinc wires with 3.0 mm and 0.3 mm in diameter were prepared via hot-extrusion and subsequent cold-drawing process respectively. The microstructure, mechanical performance, corrosion behavior, in vitro cytocompatibility and antibacterial effect were comparatively *** cold-drawing, the mechanical property, especially the elongation of the ф0.3 mm pure Zn wire was improved significantly compared with the ф3.0 mm pure Zn wire. The in vitro corrosion study including immersion and electrochemical test showed acceptable corrosion resistance of these two materials in hank's solution. The in vitro human Umbilical Vein Endothelial Cells(hUVECs) viability assay showed obviously different results, in which the ф0.3 mm pure Zn wire demonstrated favorable cytocompatibility, while the ф3.0 mm wire exhibited severe cytotoxic effect with 100% extract concentration. Both of them exhibited partly antibacterial effect on S. aureus. These results demonstrated the feasibility of the prepared 0.3 mm pure Zn wire as the potential suture material with good absorbability.

关键词： Pure zinc Wire Biodegradable metal Suture

ELECTROChEMICAL FEATURES DURING PITTING CORROSION OF LY12 ALUMINUM ALLOY IN DIFFERENT NEUTRAL SOLUTIONS

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Acta Metallurgica Sinica(English Letters) 2003年第4期16卷 319-326页

作者： Y.L.Cheng J.F.Li J.Q.Zhang C.N.cao F.h.cao Z.Zhanq DepartmentofChemistry YuquanCampusZhejiangUniversityHangzhou310027.China StateKeyLaboratoryforCorrosionandProtectionofMetals InstituteofMetalResearch.TheChineseAcademyofSciencesShenyang110016ChinaManuscriptreceived10July2002 inrevisedform10October2002

The electrochemical features of commercial airfrarne material, Al alloy LY12, in 0.349mol/L neutral sodium chloride (NaCl) and sodium sulfate (NazSO^) solutions were investigated by electrochemical impedance spectroscopy (EIS) and potentiody-namic polarization techniques. The microstructure of the as-tested samples was studied by scanning electron microscopy. The results show that the Nyquist plots of LY12 at different immersion time displayed different features, indicating that the Cl- ions elevate the corrosion rate and inhibit the repassivation of a metastable pit. It also shows that the corrosion product of LY12 formed in SO42- solution isn't easy to dissolve, and it will cover the surface of working electrode in the electrolyte. SEM images indicate that the corrosion apparent area and pit number of LY12 in NaCl solution are greater than that in Na2SO4 solution.

关键词： LY12 aluminum alloy pitting corrosion electrochemical impedance spectroscopy potentiodynamic polarization pit- morphology

INFLUENCE OF SO_4^(2-) AND Cl-ON ThE CORROSION BEhAVIOR OF COPPER TUBE IN AIR-CONDITIONING SYSTEM

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Acta Metallurgica Sinica(English Letters) 2004年第1期17卷 92-96页

作者： C.S.Wu Z.Zhang F.h.cao J.Q.Zhang J.M.Wang C.N.cao Department of Chemistry Yuquan CampusZhejiang University Hangzhou 310027ChinaDepartment of Chemistry Yuquan CampusZhejiang University Hangzhou 310027ChinaDepartment of Chemistry Yuquan CampusZhejiang University Hangzhou 310027ChinaDepartment of Chemistry Yuquan CampusZhejiang University Hangzhou 310027China State Key Laboratory for Corrosion and Protection of Metals Shenyang 110016 ChinaDepartment of ChemistryYuquan Campus Zhejiang University Hangzhou 310027ChinaDepartment of ChemistryYuquan Campus Zhejiang University Hangzhou 310027China State Key Laboratory for Corrosion and Protection of MetalsShenyang 110016 China

The influence of chloride or sulphur dioxide on the corrosion behavior of copper tube in the air-conditioning system was studied using scanning electron microscope (SEM), energy dispersion spectrometer (EDS) and cyclic polarization techniques. The results showed that the corrosion of copper tube are mainly caused by the SO42- and Cl- ions in the circulating water, and the former is mainly responsible for the general corrosion of the copper tube whilst the latter for the pitting corrosion. The different influences of SG42- and Cl- ions on the corrosion type of copper tube may be attributed to that the radius of SO42- ion is much larger than that of Cl- ion. Meanwhile the results also indicated that SO42- inhibits the pitting corrosion caused by Cl- and Cl- inhibits the general corrosion initiated by SO42- due to their competitive adsorption on the copper matrix.

关键词： copper corrosion behavior influence SO42- ion Cl- ion

STUDY OF ThE X70 PIPELINE STEEL CORRODING IN 3.0wt% NaCl SOLUTION USING ELECTROChEMICAL IMPEDANCE SPECTROSCOPY TEChNIQUE

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Acta Metallurgica Sinica(English Letters) 2004年第6期17卷 907-911页

作者： L.J.Zhang Z.Zhang F.h.cao J.Q.Zhang J.M.Wang C.N.cao DepartmentofChemistry ZhejiangUniversityHangzhou310027China DepartmentofChemistry ZhejiangUniversityHangzhou310027China／／ StateKeyLaboratoryforCorrosionandProtectionofMetalsInstituteofMetalResearchTheChineseAcademyofSciencesSlaenyang110016China

The corrosion process of the X70 pipeline steel in 3.0wt% NaCl solution were studied using polarization method, and the chronological characteristics during the entire polarization plot were investigated in detail using EIS technique. In the active region of X70 steel, such as 20mV potential bias applied on open circuit potential (OCP), the impedance spectra was comprised of three parts: a high-frequency capacitive loop, a middle-frequency capacitive loop and a low-frequency inductive component. When positive polarization potential increased, the capacitive loops at high and middle frequency range merged, and the inductive component at low frequency shrunk. At high positive polarization potential bias (500-800mV vs. OCP), the high-frequency capacitive loop and the low-frequency inductive loop exhibited as disheveled points due to the synergism of the inhomogeneity of the corroding material and the localized corrosion. The results were fitted utilizing the equivalent circuits to simulate the impedance spectra and to interpret the electrochemical features shown during the experiments.

关键词： X70 pipeline steel corrosion polarization EIS

ELECTROChEMICAL NOISE FEATURES OF PURE ALUMINUM DURING PITTING CORROSION IN NEUTRAL NaCl SOLUTION

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Acta Metallurgica Sinica(English Letters) 2003年第1期16卷 20-30页

作者： F.h.cao Z.Zhang Y.L.Cheng J.F.Li J.Q.Zhang J.M.Wang C.N.cao Department of Chemistry Zhejiang UniversityHangzhou 310027China State Key Laboratory for Corrosion and Protection of Metals Institute of Metal ResearchThe Chinese Academy of SciencesShenyang 110016China

Spontaneous electrochemical noise (EN) can be a rich source of information concerning the processes simultaneously occurring at a corroding interface. Potential noise fluctuations during the free corrosion of pure aluminum in different concentration of neutral sodium chloride solution are investigated, and the breakdown and restoration of passive metal's film are studied using potentiodynamic scanning (PDS) measurements and electrochemical impedance spectroscopy (EIS) technique. Two capacitance loops are observed in the Nyquist plots in two kinds of concentration, and the corrosion process is under activation control at first, then become diffusion control within the oxide film and corrosion products of (Al(Oh)p-mCl-m) accumulated on the surface of the corroding electrode. It is suggested that the pitting corrosion is much easier to occur for pure aluminum in 7.0wt% than in 2.0wt% NaCl solution, and the high concentration of chloride ion in solution inhibits the repassivation of a metastable pit. The corrosion rate deterministic step does not involve Cl-.

关键词： pure aluminum pitting corrosion electrochemical noise electrochemical impedance spectroscopy potentiodynamic scanning

STUDY ThE INFLUENCE OF h_(3)BO_(3)ON ThE ZINC ELECTROPLATING USING ELECTROChEMICAL NOISE TEChNIQUE

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Acta Metallurgica Sinica(English Letters) 2004年第5期17卷 661-666页

作者： Z.Zhang C.S.Wu Q.Y.Cai Y.L.Cheng F.h.cao J.Q.Zhang C.N.cao DepartmentofChemistry ZhejiangUniversityHangzhou310027China StateKeyLaboratoryforCorrosionandProtection InstituteofMetalResearchTheChineseAcademyofSciencesShenyang110016China

The influence of h3BO3 on the zinc electroplating was studied using electrochemical noise technique, cyclic voltammetry and steady-state polarization method. The results showed that, under the experimental conditions, the deposition of zinc followed the mechanism of two-dimensional nucleation and subsequent grain growth. The addition of h3BO3 into the electroplating solution prominently changes the nucleation and growth kinetics of zinc deposits, which is directly related to the features of electrocrystallization noise and the corresponding structure of the electrodeposits. The results also shown that the electrochemical noise (EN) technique can give more information about the electrodeposits structure and electroplating mechanism than other normal electrochemical measurements can give, such as steady-state polarization method and cyclic voltammetry technique.

关键词： zinc electroplating electrochemical noise electrocrystallization