Purpose–This paper aims to obtain the evolution law of dynamic performance of CR400BF electric multiple unit(EMU).Design/methodology/approach–Using the dynamic simulation based on field test,stiffness of rotary arm ...Purpose–This paper aims to obtain the evolution law of dynamic performance of CR400BF electric multiple unit(EMU).Design/methodology/approach–Using the dynamic simulation based on field test,stiffness of rotary arm nodes and damping coefficient of anti-hunting dampers were tested.Stiffness,damping coefficient,friction coefficient,track gauge were taken as random variables,the stochastic dynamics simulation method was constructed and applied to research the evolution law with running mileage of dynamic index of CR400BF EMU.Findings–The results showed that stiffness and damping coefficient subjected to normal distribution,the mean and variance were computed and the evolution law of stiffness and damping coefficient with running mileage was obtained.Originality/value–Firstly,based on the field test we found that stiffness of rotary arm nodes and damping coefficient of anti-hunting dampers subjected to normal distribution,and the evolution law of stiffness and damping coefficient with running mileage was proposed.Secondly stiffness,damping coefficient,friction coefficient,track gauge were taken as random variables,the stochastic dynamics simulation method was constructed and applied to the research to the evolution law with running mileage of dynamic index of CR400BF EMU.展开更多
Magnesium(Mg)alloys,the lightest metal construction material used in industry,play a vital role in future development.However,the poor corrosion resistance of Mg alloys in corrosion environments largely limits their p...Magnesium(Mg)alloys,the lightest metal construction material used in industry,play a vital role in future development.However,the poor corrosion resistance of Mg alloys in corrosion environments largely limits their potential wide applications.Therefore,a micro-arc oxidation/graphene oxide/stearic acid(MAO/GO/SA)superhydrophobic composite coating with superior corrosion resistance was fabricated on a Mg alloy AZ91D through micro-arc oxidation(MAO)technology,electrodeposition technique,and self-assembly technology.The composition and microstructure of the coating were characterized by scanning electron microscopy,X-ray diffraction,energy dispersive spectroscopy,and Raman spectroscopy.The effective protection of the MAO/GO/SA composite coating applied to a substrate was evaluated using potentiodynamic polarization,electrochemical impedance spectroscopy tests,and salt spray tests.The results showed that the MAO/GO/SA composite coating with a petal spherical structure had the best superhydrophobicity,and it attained a contact angle of 159.53°±2°.The MAO/GO/SA composite coating exhibited high resistance to corrosion,according to electrochemical and salt spray tests.展开更多
Mg alloys are considered the most promising engineering materials because of their unique properties.However,the uncontrolled corrosion rate of these alloys limits their applications.Therefore,in this study,a micro-ar...Mg alloys are considered the most promising engineering materials because of their unique properties.However,the uncontrolled corrosion rate of these alloys limits their applications.Therefore,in this study,a micro-arc oxidation layer was used as a transition layer to“directly”grow a zinc-based metal-organic framework(MOF)composite coating on the surface of a Mg alloy(AZ91D).Herein,the two zeolitic imidazolate framework(ZIF-8)coatings with different morphologies were separately prepared by homologous metal oxide induction and a one-step in-situ growth method.The superhydrophobic composite coating showed strong hydrophobicity and self-cleaning properties,which could prevent the penetration of water and corrosive ions(Cl^(−))into the surface of AZ91D.Electrochemical tests demonstrated that the super-hydrophobic composite coatings greatly enhanced the corrosion resistance of AZ91D,and the corrosion current density decreased from 10^(−5)to 10^(−9)A/cm^(2).These results indicate that the ZIF-8 coatings are beneficial for improving the hydrophobicity and enhancing the corrosion resistance of Mg alloys.Therefore,MOF composite coatings provide a new strategy that can be used to prepare multifunctional anticorrosion coatings on metal substrates.展开更多
A longstanding quest in material science has been the development of superhydrophobic coating based on a single material, without the requirement of fluorination or silane treatment. In this work, the micro-arc oxidat...A longstanding quest in material science has been the development of superhydrophobic coating based on a single material, without the requirement of fluorination or silane treatment. In this work, the micro-arc oxidation(MAO) coating as transition layer can effectively enhance the bonding force of the superhydrophobic coating. The semiconductor@metal organic frameworks(MOFs) core-shell structure was synthesized by a simple self-templating method, and obtained ZnO@2-methylimidazole zinc salt(ZIF-8) nanorods array on magnesium(Mg)alloy. ZnO nanorods not only act as the template but also provide Zn^(2+) for ZIF-8. In addition, we proved that the ligand concentration,synthesis time and temperature are the keys to the preparation of ZnO@ZIF-8 nanorods. As we expect, the ZnO@ZIF-8 nanorods array can trap air in the gaps to form an air layer, and the coating exhibits superhydrophobic properties(154.81°). Excitingly, ZnO@ZIF-8 nanorods array shown a superhydrophobic property, without the requirement of fluorination or silane treatment. The results shown that the coating has good chemical stability and self-cleaning performance. Meanwhile, the corrosion resistance has been significantly improved, R_(ct) was increased from 1.044×10^(3) to 1.414×10^(6) Ω/cm^(2) and I_(corr) was reduced from 4.275×10^(-5) to 5.611×10^(-9)A/cm^2. Therefore, the semiconductor@MOFs core-shell structure has broad application prospects in anti-corrosion.展开更多
Plasma electrochemical oxidation (PEO) is a surface modification technology to form ceramic coatings on magnesium alloys However,its application is limited due to its defects.This work reports a novel preparation of i...Plasma electrochemical oxidation (PEO) is a surface modification technology to form ceramic coatings on magnesium alloys However,its application is limited due to its defects.This work reports a novel preparation of in-situ sealing of PEO coatings by four-layer voltage and sol addition.The morphology and structure were characterized by scanning electron microscopy (SEM),energy dispersive X-ray spectroscopy (EDS),and X-ray diffractometer (XRD).Image-Pro Plus 6.0 was used to determine the porosity of the coating,which was decreased from 8.53%to 0.51%.Simultaneously,the coating thickness was increased by a factor of four.The anti-corrosion performance of each sample was evaluated using electrochemical tests,and the findings revealed that the corrosion current density of coatings (i_(corr)) of the samples were lowered from 9.152×10^(-2) to 6.152×10^(-4) mA·cm^(-2),and the total resistance (R_(T)) of the samples were enhanced from 2.19×10^(4) to 2.33×10^(5)Ω·cm^(2).The salt spray test used to simulate the actual environment showed that corrosion points appeared on the surface of the coating only at the 336 h.In addition,the mechanism of PEO self-sealing behavior was described in this article.展开更多
基金Science and Technology Development Project Agreement/Contract,China National Railway Group Co.,Ltd.(N2023J012)support by China Academy of Railway Sciences Corporation Limited(2021YJ208).
文摘Purpose–This paper aims to obtain the evolution law of dynamic performance of CR400BF electric multiple unit(EMU).Design/methodology/approach–Using the dynamic simulation based on field test,stiffness of rotary arm nodes and damping coefficient of anti-hunting dampers were tested.Stiffness,damping coefficient,friction coefficient,track gauge were taken as random variables,the stochastic dynamics simulation method was constructed and applied to research the evolution law with running mileage of dynamic index of CR400BF EMU.Findings–The results showed that stiffness and damping coefficient subjected to normal distribution,the mean and variance were computed and the evolution law of stiffness and damping coefficient with running mileage was obtained.Originality/value–Firstly,based on the field test we found that stiffness of rotary arm nodes and damping coefficient of anti-hunting dampers subjected to normal distribution,and the evolution law of stiffness and damping coefficient with running mileage was proposed.Secondly stiffness,damping coefficient,friction coefficient,track gauge were taken as random variables,the stochastic dynamics simulation method was constructed and applied to the research to the evolution law with running mileage of dynamic index of CR400BF EMU.
基金financially supported by the Guangxi Natural Science Foundation,China(No.2020GXNSFAA 159011)the National Natural Science Foundation of China(No.51664011).
文摘Magnesium(Mg)alloys,the lightest metal construction material used in industry,play a vital role in future development.However,the poor corrosion resistance of Mg alloys in corrosion environments largely limits their potential wide applications.Therefore,a micro-arc oxidation/graphene oxide/stearic acid(MAO/GO/SA)superhydrophobic composite coating with superior corrosion resistance was fabricated on a Mg alloy AZ91D through micro-arc oxidation(MAO)technology,electrodeposition technique,and self-assembly technology.The composition and microstructure of the coating were characterized by scanning electron microscopy,X-ray diffraction,energy dispersive spectroscopy,and Raman spectroscopy.The effective protection of the MAO/GO/SA composite coating applied to a substrate was evaluated using potentiodynamic polarization,electrochemical impedance spectroscopy tests,and salt spray tests.The results showed that the MAO/GO/SA composite coating with a petal spherical structure had the best superhydrophobicity,and it attained a contact angle of 159.53°±2°.The MAO/GO/SA composite coating exhibited high resistance to corrosion,according to electrochemical and salt spray tests.
基金supported by Guangxi Natural Science Foundation of China(No.2020GXNSFAA159011)National Natural Science Foundation of China(No.51664011)Guangxi Key Laboratory Foundation of China(No.EMFM20211120).
文摘Mg alloys are considered the most promising engineering materials because of their unique properties.However,the uncontrolled corrosion rate of these alloys limits their applications.Therefore,in this study,a micro-arc oxidation layer was used as a transition layer to“directly”grow a zinc-based metal-organic framework(MOF)composite coating on the surface of a Mg alloy(AZ91D).Herein,the two zeolitic imidazolate framework(ZIF-8)coatings with different morphologies were separately prepared by homologous metal oxide induction and a one-step in-situ growth method.The superhydrophobic composite coating showed strong hydrophobicity and self-cleaning properties,which could prevent the penetration of water and corrosive ions(Cl^(−))into the surface of AZ91D.Electrochemical tests demonstrated that the super-hydrophobic composite coatings greatly enhanced the corrosion resistance of AZ91D,and the corrosion current density decreased from 10^(−5)to 10^(−9)A/cm^(2).These results indicate that the ZIF-8 coatings are beneficial for improving the hydrophobicity and enhancing the corrosion resistance of Mg alloys.Therefore,MOF composite coatings provide a new strategy that can be used to prepare multifunctional anticorrosion coatings on metal substrates.
基金financially supported by Guangxi Natural Science Foundation of China (No.2020GXNSFAA159011)National Natural Science Foundation of China (No.51664011)。
文摘A longstanding quest in material science has been the development of superhydrophobic coating based on a single material, without the requirement of fluorination or silane treatment. In this work, the micro-arc oxidation(MAO) coating as transition layer can effectively enhance the bonding force of the superhydrophobic coating. The semiconductor@metal organic frameworks(MOFs) core-shell structure was synthesized by a simple self-templating method, and obtained ZnO@2-methylimidazole zinc salt(ZIF-8) nanorods array on magnesium(Mg)alloy. ZnO nanorods not only act as the template but also provide Zn^(2+) for ZIF-8. In addition, we proved that the ligand concentration,synthesis time and temperature are the keys to the preparation of ZnO@ZIF-8 nanorods. As we expect, the ZnO@ZIF-8 nanorods array can trap air in the gaps to form an air layer, and the coating exhibits superhydrophobic properties(154.81°). Excitingly, ZnO@ZIF-8 nanorods array shown a superhydrophobic property, without the requirement of fluorination or silane treatment. The results shown that the coating has good chemical stability and self-cleaning performance. Meanwhile, the corrosion resistance has been significantly improved, R_(ct) was increased from 1.044×10^(3) to 1.414×10^(6) Ω/cm^(2) and I_(corr) was reduced from 4.275×10^(-5) to 5.611×10^(-9)A/cm^2. Therefore, the semiconductor@MOFs core-shell structure has broad application prospects in anti-corrosion.
基金financially supported by the Guangxi Natural Science Foundation(No.2020GXNSFAA159011)the National Natural Science Foundation of China(No.51664011)。
文摘Plasma electrochemical oxidation (PEO) is a surface modification technology to form ceramic coatings on magnesium alloys However,its application is limited due to its defects.This work reports a novel preparation of in-situ sealing of PEO coatings by four-layer voltage and sol addition.The morphology and structure were characterized by scanning electron microscopy (SEM),energy dispersive X-ray spectroscopy (EDS),and X-ray diffractometer (XRD).Image-Pro Plus 6.0 was used to determine the porosity of the coating,which was decreased from 8.53%to 0.51%.Simultaneously,the coating thickness was increased by a factor of four.The anti-corrosion performance of each sample was evaluated using electrochemical tests,and the findings revealed that the corrosion current density of coatings (i_(corr)) of the samples were lowered from 9.152×10^(-2) to 6.152×10^(-4) mA·cm^(-2),and the total resistance (R_(T)) of the samples were enhanced from 2.19×10^(4) to 2.33×10^(5)Ω·cm^(2).The salt spray test used to simulate the actual environment showed that corrosion points appeared on the surface of the coating only at the 336 h.In addition,the mechanism of PEO self-sealing behavior was described in this article.
