在固定硬涂层形状的前提下寻找最佳的涂敷位置是工程化实施硬涂层阻尼减振的迫切需求。以硬涂层薄板为例,研究实现上述硬涂层阻尼优化的方法。针对局部涂敷硬涂层的薄板结构完成了有限元建模,并利用修正模态应变能法确定了涂层复合结构...在固定硬涂层形状的前提下寻找最佳的涂敷位置是工程化实施硬涂层阻尼减振的迫切需求。以硬涂层薄板为例,研究实现上述硬涂层阻尼优化的方法。针对局部涂敷硬涂层的薄板结构完成了有限元建模,并利用修正模态应变能法确定了涂层复合结构的模态损耗因子。以获得单阶次或者多阶次最大模态损耗因子为目标,以涂层位置为设计变量描述了该硬涂层薄板阻尼优化模型。提出利用多种群遗传算法求解该优化问题的方法。以单面局部涂敷Ni Cr Al Co Y+YSZ硬涂层材料的悬臂板为例进行了实例研究,基于所创建的优化模型和优化方法,在薄板上实施了硬涂层涂敷位置的优化,并用实验验证了硬涂层板阻尼优化结果的合理性。展开更多
A rotating cantilever sandwich-plate model with a pre-twisted and pre-set angle has been developed to investigate the vibrational behavior of an aero-engine turbine blade with thermal barrier coating(TBC) layers. The ...A rotating cantilever sandwich-plate model with a pre-twisted and pre-set angle has been developed to investigate the vibrational behavior of an aero-engine turbine blade with thermal barrier coating(TBC) layers. The classic von Karman plate theory and the first-order shear deformation theory are applied to derive the energy equations of the rotating TBC blade, in which the geometric shapes, the work ambient temperature, and the TBC material properties are considered. The Chebyshev-Ritz method is used to obtain the nature frequency of the rotating TBC blade. For static frequency and modal analysis, the finite-element method(FEM)is also applied to compare and validate the results from the Chebyshev-Ritz method. A good agreement is found among these kinds of methods. For dynamic frequency, the results are analyzed in detail concerning the influence of system parameters such as the thickness of the TBC layer, the working temperature, and the pre-twisted and pre-set angle. Finally, the Campbell diagram is demonstrated to analyze the resonance property of the cantilever sandwich TBC blade model.展开更多
Composite coatings consisting of carbon and polytetrafluoroethylene(PTFE) were prepared on Ti alloy substrate by a simple two-step process of hydrothermal and impregnation. The morphology, composition, hydrophobic and...Composite coatings consisting of carbon and polytetrafluoroethylene(PTFE) were prepared on Ti alloy substrate by a simple two-step process of hydrothermal and impregnation. The morphology, composition, hydrophobic and corrosion properties of the composite coatings were characterized by scanning electron microscopy(SEM), Fourier transform infrared spectroscopy(FTIR), water contact angle method, X-ray photoelectron spectroscopy(XPS) and electrochemical technique, respectively. The effect of PTFE content on the corrosion properties of the composite coatings was studied. It is found that the composite coating film exhibits a full coverage with uniformly distributed PTFE when 0.1 mol/L of glucose is used as carbon source and 20 wt.% PTFE suspension as impregnating solution. The coating with 20 wt.% PTFE has a good bonding strength with Ti plate and exhibits excellent hydrophobic property with a water contact angle of 142.3° as well as superior corrosion resistance with corrosion current density as low as 0.0045 μA/cm^2. With regard to its excellent hydrophobicity and corrosion resistance, the carbon-PTFE composite coating may find potential application in automobiles and metal corrosion industries.展开更多
In view of the M_(n+1)AX_(n)(MAX)phase coatings benefting the adaptive passivation flm for good corrosion resistance and high electronic density of states for excellent electrical conductivity,here,we reported the Cr_...In view of the M_(n+1)AX_(n)(MAX)phase coatings benefting the adaptive passivation flm for good corrosion resistance and high electronic density of states for excellent electrical conductivity,here,we reported the Cr_(2)Al C MAX phase coatings with different preferred orientations by a homemade technique consisting of vacuum arc and magnetron sputtering.The dependence of surface and interface microstructural evolution upon the corrosion and electrochemical properties of deposited coating was focused.Results showed that all the Cr_(2)Al C coatings with different phase orientations greatly improved the performance of stainless steel(SS)316 L substrate.Specifcally,the lowest value of interface contact resistance(ICR)reached to 3.16 mΩcm^(2)and the lowest corrosion current density was 2×10^(-2)μA cm^(-2),which were much better than those of bare SS316L.The combined studies of electrochemical properties and theoretical calculations demonstrated that the Cr_(2)Al C coatings with preferred(103)orientation were easier to form oxide passivation flm on their surface to increase the corrosion resistance.展开更多
Although numerical models such as the computational fluid dynamics–discrete element method (CFD–DEM) have enabled the accurate simulation of laboratory-scale apparatuses, the application of these methods to large-sc...Although numerical models such as the computational fluid dynamics–discrete element method (CFD–DEM) have enabled the accurate simulation of laboratory-scale apparatuses, the application of these methods to large-scale apparatuses with many particles and time scales ranging from minutes to hours remains a challenge. The recently developed recurrence CFD (rCFD) method seeks to overcome these issues in pseudo-periodic processes by extrapolating globally recurring patterns in a physically meaningful way and describing the transport and interaction of passive scalars using Lagrangian tracers. Spouted beds represent an interesting target because of the associated variety of flow regimes. They can be effectively described by CFD–DEM on the time scale of tens of seconds, whereas industrially relevant processes typically take hours. In this contribution, we established the validity of applying the Lagrangian rCFD method to spouted beds by demonstrating the accurate reproduction of the particle residence time distribution in a fictitious spray zone. The deposition of spray droplets onto tracer particles was simulated for 1 h, and the particle surface coverage distribution was estimated using a statistical approach for both an unstabilized prismatic spouted bed and one stabilized by draft plates.展开更多
In the present paper, coating systems consisting of a metallic corrosion barrier and a conductive graphitic carbon layer were deposited by a DC vacuum arc process. The coatings were developed in a batch process for ap...In the present paper, coating systems consisting of a metallic corrosion barrier and a conductive graphitic carbon layer were deposited by a DC vacuum arc process. The coatings were developed in a batch process for application in the polymer electrolyte membrane fuel cell (PEMFC), and transferred to a continuous coil process to facilitate industrial mass production. The coating samples in the coil process had to achieve comparable results to the samples produced in the batch process, to meet the requirements of the environment prevailing in the fuel cell.The transfer to roll-to-roll processes is a crucial factor for commercial upscaling of PEMFC production. The experimental results showed that the electrical conductivity and corrosion resistance of the samples in the coil process were significantly improved compared to the uncoated base material and showed comparable performance to batch coated samples. X-ray photoelectron spectroscopy (XPS) was performed to determine the depth profile and the surface composition. Additional measurements were recorded for the contact resistances using the four-wire sensing method as well as corrosion resistance using potentiodynamic methods.展开更多
Incorporating elastomers such as polymers in protective structures to withstand high energetic dynamic loads,has gained significant interest.The main objective of this study is to investigate the influence of a Polyur...Incorporating elastomers such as polymers in protective structures to withstand high energetic dynamic loads,has gained significant interest.The main objective of this study is to investigate the influence of a Polyurea coating towards the blast-induced response in steel plates.As such,Polyurea coated steel plates were tested under near-field blast loads,produced by the detonation of 1 kg of spherical nitromethane charges,at a standoff distance of 150 mm.Mild steel(XLERPLATE 350)and high-strength steel(BIS80)plates with thicknesses of 10 mm were Polyurea coated with thicknesses of 6 mm and 12 mm on either the front(facing the charge)or the back face.The deformation profiles were measured using 3D scanning.Numerical simulations were performed using the non-linear finite element code LS-DYNA.The strain-dependent behaviour of the steel and Polyurea were represented by Johnson-cook and Money-Rivlin constitutive models,respectively.The numerical models were validated by comparing the plate deflection results obtained from the experiments and were then used in the subsequent parametric study to investigate the optimum thickness of the Polyurea coating.The results indicate that back face coating contributes towards an approximately 20%reduction in the residual deformation as well as the absence of melting of the Polyurea layer,while the front-face coating can be used a means of providing additional standoff distance to the steel plates.展开更多
文摘在固定硬涂层形状的前提下寻找最佳的涂敷位置是工程化实施硬涂层阻尼减振的迫切需求。以硬涂层薄板为例,研究实现上述硬涂层阻尼优化的方法。针对局部涂敷硬涂层的薄板结构完成了有限元建模,并利用修正模态应变能法确定了涂层复合结构的模态损耗因子。以获得单阶次或者多阶次最大模态损耗因子为目标,以涂层位置为设计变量描述了该硬涂层薄板阻尼优化模型。提出利用多种群遗传算法求解该优化问题的方法。以单面局部涂敷Ni Cr Al Co Y+YSZ硬涂层材料的悬臂板为例进行了实例研究,基于所创建的优化模型和优化方法,在薄板上实施了硬涂层涂敷位置的优化,并用实验验证了硬涂层板阻尼优化结果的合理性。
基金supported by the National Natural Science Foundation of China(Grant Nos.11272016&11290152)the Beijing Municipal Commission of Educationthe Ri-Xin Talents Project of Beijing University of Technology
文摘A rotating cantilever sandwich-plate model with a pre-twisted and pre-set angle has been developed to investigate the vibrational behavior of an aero-engine turbine blade with thermal barrier coating(TBC) layers. The classic von Karman plate theory and the first-order shear deformation theory are applied to derive the energy equations of the rotating TBC blade, in which the geometric shapes, the work ambient temperature, and the TBC material properties are considered. The Chebyshev-Ritz method is used to obtain the nature frequency of the rotating TBC blade. For static frequency and modal analysis, the finite-element method(FEM)is also applied to compare and validate the results from the Chebyshev-Ritz method. A good agreement is found among these kinds of methods. For dynamic frequency, the results are analyzed in detail concerning the influence of system parameters such as the thickness of the TBC layer, the working temperature, and the pre-twisted and pre-set angle. Finally, the Campbell diagram is demonstrated to analyze the resonance property of the cantilever sandwich TBC blade model.
基金Project(2018YFB1502500) supported by the National Key Research and Development Program of ChinaProject supported by State Key Laboratory of Powder Metallurgy,Central South University,China+1 种基金Projects(21506258,51774127) supported by the National Natural Science Foundation of ChinaProject(2019RS2067) supported by the Science and Technology Planning Project of Hunan Province,China
文摘Composite coatings consisting of carbon and polytetrafluoroethylene(PTFE) were prepared on Ti alloy substrate by a simple two-step process of hydrothermal and impregnation. The morphology, composition, hydrophobic and corrosion properties of the composite coatings were characterized by scanning electron microscopy(SEM), Fourier transform infrared spectroscopy(FTIR), water contact angle method, X-ray photoelectron spectroscopy(XPS) and electrochemical technique, respectively. The effect of PTFE content on the corrosion properties of the composite coatings was studied. It is found that the composite coating film exhibits a full coverage with uniformly distributed PTFE when 0.1 mol/L of glucose is used as carbon source and 20 wt.% PTFE suspension as impregnating solution. The coating with 20 wt.% PTFE has a good bonding strength with Ti plate and exhibits excellent hydrophobic property with a water contact angle of 142.3° as well as superior corrosion resistance with corrosion current density as low as 0.0045 μA/cm^2. With regard to its excellent hydrophobicity and corrosion resistance, the carbon-PTFE composite coating may find potential application in automobiles and metal corrosion industries.
基金fnancially supported by the National Science Found for Distinguished Young Scholars of China(No.52025014)the National Science and Technology Major Project(No.2017VII-0012–0108)+1 种基金the National Science Foundation of China(Nos.51901238 and 52101109)the Natural Science Foundation of Ningbo(Nos.202003N4350 and 202003N4025)。
文摘In view of the M_(n+1)AX_(n)(MAX)phase coatings benefting the adaptive passivation flm for good corrosion resistance and high electronic density of states for excellent electrical conductivity,here,we reported the Cr_(2)Al C MAX phase coatings with different preferred orientations by a homemade technique consisting of vacuum arc and magnetron sputtering.The dependence of surface and interface microstructural evolution upon the corrosion and electrochemical properties of deposited coating was focused.Results showed that all the Cr_(2)Al C coatings with different phase orientations greatly improved the performance of stainless steel(SS)316 L substrate.Specifcally,the lowest value of interface contact resistance(ICR)reached to 3.16 mΩcm^(2)and the lowest corrosion current density was 2×10^(-2)μA cm^(-2),which were much better than those of bare SS316L.The combined studies of electrochemical properties and theoretical calculations demonstrated that the Cr_(2)Al C coatings with preferred(103)orientation were easier to form oxide passivation flm on their surface to increase the corrosion resistance.
文摘Although numerical models such as the computational fluid dynamics–discrete element method (CFD–DEM) have enabled the accurate simulation of laboratory-scale apparatuses, the application of these methods to large-scale apparatuses with many particles and time scales ranging from minutes to hours remains a challenge. The recently developed recurrence CFD (rCFD) method seeks to overcome these issues in pseudo-periodic processes by extrapolating globally recurring patterns in a physically meaningful way and describing the transport and interaction of passive scalars using Lagrangian tracers. Spouted beds represent an interesting target because of the associated variety of flow regimes. They can be effectively described by CFD–DEM on the time scale of tens of seconds, whereas industrially relevant processes typically take hours. In this contribution, we established the validity of applying the Lagrangian rCFD method to spouted beds by demonstrating the accurate reproduction of the particle residence time distribution in a fictitious spray zone. The deposition of spray droplets onto tracer particles was simulated for 1 h, and the particle surface coverage distribution was estimated using a statistical approach for both an unstabilized prismatic spouted bed and one stabilized by draft plates.
文摘In the present paper, coating systems consisting of a metallic corrosion barrier and a conductive graphitic carbon layer were deposited by a DC vacuum arc process. The coatings were developed in a batch process for application in the polymer electrolyte membrane fuel cell (PEMFC), and transferred to a continuous coil process to facilitate industrial mass production. The coating samples in the coil process had to achieve comparable results to the samples produced in the batch process, to meet the requirements of the environment prevailing in the fuel cell.The transfer to roll-to-roll processes is a crucial factor for commercial upscaling of PEMFC production. The experimental results showed that the electrical conductivity and corrosion resistance of the samples in the coil process were significantly improved compared to the uncoated base material and showed comparable performance to batch coated samples. X-ray photoelectron spectroscopy (XPS) was performed to determine the depth profile and the surface composition. Additional measurements were recorded for the contact resistances using the four-wire sensing method as well as corrosion resistance using potentiodynamic methods.
文摘Incorporating elastomers such as polymers in protective structures to withstand high energetic dynamic loads,has gained significant interest.The main objective of this study is to investigate the influence of a Polyurea coating towards the blast-induced response in steel plates.As such,Polyurea coated steel plates were tested under near-field blast loads,produced by the detonation of 1 kg of spherical nitromethane charges,at a standoff distance of 150 mm.Mild steel(XLERPLATE 350)and high-strength steel(BIS80)plates with thicknesses of 10 mm were Polyurea coated with thicknesses of 6 mm and 12 mm on either the front(facing the charge)or the back face.The deformation profiles were measured using 3D scanning.Numerical simulations were performed using the non-linear finite element code LS-DYNA.The strain-dependent behaviour of the steel and Polyurea were represented by Johnson-cook and Money-Rivlin constitutive models,respectively.The numerical models were validated by comparing the plate deflection results obtained from the experiments and were then used in the subsequent parametric study to investigate the optimum thickness of the Polyurea coating.The results indicate that back face coating contributes towards an approximately 20%reduction in the residual deformation as well as the absence of melting of the Polyurea layer,while the front-face coating can be used a means of providing additional standoff distance to the steel plates.
