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Research on Cracking Mechanism of Aero-Engine Thermocouple Bearing Ring Under High-Temperature Creep Test

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SSRN 2024年

作者： Wang, Songjun He, Jianjun Gong, Zhihui Cai, Yuhui Yao, Biqing Xiao, Tingyi School of Energy and Power Engineering Changsha University of Science and Technology Changsha410114 China State Key Laboratory of Advanced Design and Manufacture for Vehicle Body Hunan University Changsha40082 China

The thermocouple bearing ring in aero-engine have prematurely cracked during service, posing a significant safety hazard. This paper analyzes the microstructure and fracture behavior of K4169 high-temperature superalloy specimens under thermomechanical loading considering this phenomenon. The results revealed that a small amount of needle-like δ-phases and an increased number of Laves phases accumulated around the grain boundaries after direct aging treatment. After solution treatment followed by aging, more twinning features were observed at the grain boundaries, and the Laves phase was diffusely distributed. No needle-like δ-phases were found at 710°C, indicating that the heat treatment was optimal. At 650°C, the alloy demonstrated excellent creep resistance, characterized by distinct stages of constant velocity and accelerated creep. On the specimen's surface, twins and a few dislocations appeared, while the Laves phase precipitated and partially aggregated at the grain boundaries, accompanied by the formation of small voids. As the temperature increases, the Laves phase content increases along with the formation of voids. These Laves phases were accompanied by needle-like δ phases, forming 'bands' that facilitated crack initiation, primarily along the grain boundaries. At 650°C, secondary cracks appeared at the fracture, indicative of predominantly ductile fracture behavior. With an increase in temperature to 710°C, precipitation of the second phase increased significantly, leading to pronounced stress concentration. Consequently, the fracture mode transitioned from ductile fracture to a ductile-brittle mixed fracture. © 2024, The Authors. All rights reserved.

关键词： Grain boundaries

Effects of F- Ions on the Electrochemical and Interface Behavior of Cathodes in Zinc Electrowinning

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SSRN 2023年

作者： Shen, Guocan Jiang, Chunxiang Shao, Yanlin Chang, Linhui Chen, Buming State Key Laboratory of Advanced Special Steel Shanghai Key Laboratory of Advanced Ferrometallurgy School of Materials Science and Engineering Shanghai University Shanghai200444 China Faculty of Metallurgical and Energy Engineering Kunming University of Science and Technology Kunming650093 China Yunnan Metallurgical Electrode Materials Engineering Technology Research Center Kunming650106 China

Zn metal is increasingly used in energy and industrial fields, which puts forward higher requirements for the research of zinc electrowinning process. In this work, the effects of fluoride ions (F-) in zinc electrolyte on the cathodic kinetics and zinc product quality during zinc electrodeposition was systematically investigated via a series analysis. The results revealed that the addition of F- in the electrolyte showed a polarization effect, the apparent cathodic exchange current density increased by 104 orders of magnitude, and the zinc deposition overpotential decreased by 46mV when the concentration of F- in the electrolyte was 400mg/L. However, F- also reduces the hydrogen evolution overvoltage, when the electrolyte contains 400mg/L F-, the hydrogen evolution overvoltage on aluminum cathode and zinc cathode decreases by 121 mV and 97 mV, respectively. The promoted hydrogen evolution kinetics increases energy consumption and surface porosity. Moreover, F- ions corrode the Al2O3 oxide film on the cathode surface and accelerate the corrosion of the aluminum cathode plate. The cross-section micrograph shows that zinc deposition on the damaged aluminum substrate increases the adhesion and makes it difficult to peel off. © 2023, The Authors. All rights reserved.

关键词： Electrolytes

Pyrolysis of ZIF-Co assisted by a small amount of KNO3: Tuning of Co-CoOx@N, O co-doped carbon hybrid nanostructures for accelerating water splitting

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SSRN 2024年

作者： Li, Anqi Qian, Xiaoyu Han, Mengyan Li, Zhichun He, Xiaobo Wang, Guofeng Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology School of Petrochemical Engineering Changzhou University Changzhou213164 China State Key Laboratory for Oxo Synthesis and Selective Oxidation Lanzhou Institute of Chemical Physics Chinese Academy of Sciences Lanzhou730000 China

Electrochemical catalytic water splitting is considered as a green and promising technique for hydrogen production, and highly active catalysts toward cathodic hydrogen evolution reaction (HER) and anodic oxygen evolution reaction (OER) are required, especially for bifunctional ones. In this work, the bifunctional catalysts with Co-CoOx@N, O co-doped carbon (NOC) hybrid nanostructures have been prepared via pyrolysis of ZIF-Co with assistance of a small amount of KNO3. KNO3 plays important roles in tuning the inner and outer structures of Co-CoOx@NOC hybrid nanostructures. The proposed SOv, which is defined as the content of oxygen vacancy (Ov) per unit surface area of the inner Co-CoOx nanoparticle, and charge transfer resistance (Rct) are used as the descriptors of inner structures, while hydrophilicity (or contact angle) is applied as the main feature of outer structures. SOv, Rct and hydrophilicity are well tuned by the fed mass of KNO3, and a moderate fed mass is the key to balancing SOv, Rct and hydrophilicity and further is beneficial to accelerating specific activity for both HER and OER. Thus, both HER and OER specific activity is peaked by Co-CoOx@NOC-0.025KNO3 with a moderate fed mass of KNO3 of 0.025 g. This optimal catalyst also has high apparent activity with high HER and OER current densities (≥500 mA cm-2) under low overpotentials, and promotes overall water splitting with high current densities (500 mA cm-2) at a cell voltage of ~1.63 V. © 2024, The Authors. All rights reserved.

关键词： Electrocatalysis

Crystal structure graph neural networks for high-performance superconducting critical temperature prediction

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Science China Materials 2024年第10期67卷 3253-3261页

作者： Jingzi Zhang Chengquan Zhong Xiaoting Lu Jiakai Liu Kailong Hu Xi Lin School of Materials Science and Engineering Harbin Institute of TechnologyShenzhen 518055China Blockchain Development and Research Institute Harbin Institute of TechnologyShenzhen 518055China School of Computer Science and Technology Harbin Institute of TechnologyShenzhen 518055China State Key Laboratory of Advanced Welding and Joining Harbin Institute of TechnologyHarbin 150001China Laboratory of Environmental Sciences and Technology Xinjiang Technical Institute of Physics&ChemistryChinese Academy of SciencesUrumqi 830011China Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of SciencesBeijing 100049China Sunrise(Xiamen)Photovoltaic Industry Co. Ltd.Xiamen 361006China

The utilization of machine learning methods to predict the superconducting critical temperature(T_(c))traditionally necessitates manually constructing elemental features,which challenges both the provision of meaningful chemical insights and the accuracy of *** this work,we introduced crystal structure graph neural networks to extract structure-based features for T_(c)*** results indicated that these structure-based models outperformed all previously reported models,achieving an impressive coefficient of determination(R^(2))of 0.962 and a root mean square error(RMSE)of 6.192 *** the existing Inorganic Crystal Structure Database(ICSD),our model successfully identified 76 potential high-temperature superconducting compounds with T_(c)≥77 *** these,Tl_(5)Ba_(6)Ca_(6)Cu_(9)O_(29)and TlYBa_(2)Cu_(2)O_(7)exhibit remarkably high T_(c)values of 108.4 and 101.8 K,*** work provides a perspective on the structure-property relationship for reliable T_(c)prediction.

关键词： superconductors superconducting critical temperature crystal graph network crystal structural features

Mode-Folded Phase Shifter Based Reconfigurable Optical Switch with $\mathbf{0.6}\mathbf{V}\cdot \mathbf{cm} \mathbf{V}\boldsymbol{\pi}\cdot \mathbf{L}$ on Thin-Film Lithium Niobate for Channel Scalable Optical Interconnects

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Mode-Folded Phase Shifter Based Reconfigurable Optical Switc...

Conference on Lasers and Electro-Optics (CLEO)

作者： Xinyi Wang Jiangbing Du Jiacheng Liu Ke Xu Zuyuan He State Key Laboratory of Advanced Optical Communication Systems and Networks Shanghai Jiao Tong University Shanghai China Department of Electronic and Information Engineering Harbin Institute of Technology (Shenzhen) Shenzhen China

A reconfigurable optical switch based on mode-folded phase shifter over LNOI is experimentally demonstrated with high switching efficiency of $0.6\mathrm{V}\cdot \text{cm} \mathrm{V}\pi\cdot \mathrm{L}$ . The switchi... 详细信息

ISBN: (纸本)9798350369311

关键词： Optical interconnections Optical switches Scalability Lithium niobate Phase shifters Lasers and electrooptics Laser modes Electro-optical waveguides

On Fatigue Damage Tolerance of Cfrp/Al Adhesive Joints with Thermal Effects

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SSRN 2024年

作者： He, Zongkai Zheng, Gang Luo, Quantian Li, Qing Sun, Guangyong State Key Laboratory of Advanced Design and Manufacturing Technology for Vehicle Hunan University Changsha410082 China School of Aerospace Mechanical and Mechatronic Engineering The University of Sydney SydneyNSW2006 Australia

In order to promote adhesive connection in primary load-bearing structures for engineering applications, fatigue damage tolerance signifies a critical parameter in line with the guidance of FAA AC 20-107B. This study aims to investigate this issue from four aspects, namely, fatigue crack statistics, residual performance, critical point for fatigue damage tolerance, and adhesive property degradation. Joints subjected to pre-fatigue loading were first tested, in which the specimens with different degrees of fatigue damage were selected through the real-time stiffness monitoring. Their residual strengths under different temperatures were then studied. The degradation mechanisms of joint strength were further evaluated quantitatively in terms of degradation factors by using pre-fatigue crack and cohesive zone model (CZM). It is shown that for million cycle condition, the adhesive property will degrade to around 50% of its initial value, which generally counts for 60% of reduction in the fatigue strength. A short-term high-temperature environment can cause comparable degradation effect to a long-term fatigue cyclic load. For sake of service safety, it is recommended to take the normalized stiffness of 92% as the critical point. This study revealed that a reliable management for residual fatigue performance can be achieved. It is anticipated to provide an effective guide for damage-tolerant design, reliable safety monitoring and repair of adhesive *** order to promote adhesive connection in primary load-bearing structures for engineering applications, fatigue damage tolerance signifies a critical parameter in line with the guidance of FAA AC 20-107B. This study aims to investigate this issue from four aspects, namely, fatigue crack statistics, residual performance, critical point for fatigue damage tolerance, and adhesive property degradation. Joints subjected to pre-fatigue loading were first tested, in which the specimens with different degrees of fatigue damag

关键词： Fatigue damage

A Novel Current-Based Identification Method for Dynamic Performance of High-Speed On/Off Valve

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SSRN 2024年

作者： Xu, Enguang Zhong, Qi He, Xianjian Mao, Yongxin Huang, Yi Yang, Huayong College of Mechanical Engineering Zhejiang University of Technology Hangzhou310023 China State Key Laboratory of Fluid Power and Mechatronic Systems Zhejiang University Hangzhou310027 China Key Laboratory of Special Purpose Equipment and Advanced Processing Technology Ministry of Education Zhejiang University of Technology Zhejiang Province Hangzhou310023 China

Digital hydraulic system's response speed and control accuracy depend on the dynamic performance of High-speed on/off valve (HSV), which serves as the core control component of the system. However, the compact structure and embedded installation configuration of the HSV make it difficult to accurately measure its dynamic performance. To address the problem, a novel current-based identification method (CBIM) is proposed in this study. The innovative conclusions are found that the first-order and second-order derivative behaviors can identify the critical switching states and fully switched states, respectively. The results show that the proposed CBIM can accurately measure the moving characteristic of valve spool in the opening and closing stages under different temperature rise conditions, with a maximum identification error of only 3.96 %. Finally, in the hydraulic system at different supply pressures, the obvious feature points of the coil derivative curves further validate the effectiveness of the proposed method. © 2024, The Authors. All rights reserved.

关键词： Hydraulic equipment

Structural Design and Performance Study of a Biobased UV/Moisture Dual-Curing Coating for UV Inadequate Curing Conditions

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SSRN 2024年

作者： Ding, Ao Zhang, Pengfei Zhou, Bing Liu, Guang Xu, Pingfan Luo, Yaofa Zhuang, Yihua Zhang, Peikun Chen, Aizheng Liu, Yuan Luo, Zhongzhen School of Advanced Manufacturing Fuzhou University Jinjiang362200 China Institute of Biomaterials and Tissue Engineering Fujian Provincial Key Laboratory of Biochemical Technology Huaqiao University Xiamen361021 China State Key Laboratory of Polymer Materials Engineering Polymer Research Institute of Sichuan University Chengdu610065 China Joint Laboratory on Advanced Materials Technologies College of Materials Science and Engineering Fuzhou University Fuzhou350108 China

As a new type of coating in recent years, UV curable coating has been widely used because of its environment friendliness, high curing efficiency and optimized energy consumption. However, UV curing technology also has some problems such as colored coating and shadow parts are difficult to cure, the establishment of UV/ moisture curing system can effectively solve these problems. In addition, the selection of raw materials in coating preparation is also gradually inclined to choose environmentally friendly bio-based materials. In this context, a UV/moisture bi-curable polyurethane prepolymer was synthesized from castor oil (CO), polytetramethylene ether glycol (PTMEG), isophorone diisocyanate (IPDI), hydroxyethyl methacrylate (HEMA) and tetrahydrofuran acrylate (THFA). The prepared prepolymer can be cured quickly after the addition of photoinitiator and monomer. The volume shrinkage of the cured coating is 3.05 vol% and the gel content is 92.73 wt%. The coating has excellent heat resistance and mechanical strength, and the tensile strength can reach 8.4MPa. The water contact Angle of the coating can reach 91°, which has good anti-fouling performance. Compared with traditional photocurable coatings, the coatings show excellent comprehensive properties and have wider application prospects. © 2024, The Authors. All rights reserved.

关键词： Heat resistance

Manipulating light transmission and absorption via an achromatic reflectionless metasurface

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PhotoniX 2023年第1期4卷 637-651页

作者： Xiaoying Zheng Jing Lin Zhuo Wang Haoyang Zhou Qiong He Lei Zhou State Key Laboratory of Surface Physics Key Laboratory of Micro and Nano Photonic Structures(Ministry of Education)and Department of PhysicsFudan University200433 ShanghaiPeople’s Republic of China Academy for Engineering and Technology Fudan University200433 ShanghaiPeople’s Republic of China Collaborative Innovation Center of Advanced Microstructures 210093 NanjingPeople’s Republic of China

Freely switching light transmission and absorption via an achromatic reflectionless screen is highly desired for many photonic applications(e.g.,energy-harvesting,cloaking,etc.),but available meta-devices often exhibit reflections out of their narrow working ***,we rigorously demonstrate that an optical metasurface formed by two resonator arrays coupled vertically can be perfectly reflectionless at all frequencies below the first diffraction mode,when the near-field(NF)and far-field(FF)couplings between two constitutional resonators satisfy certain *** intrinsic loss of the system can further modulate the ratio between light transmission and absorption,yet keeping reflection diminished ***/fabricating a series of metasurfaces with different inter-resonator configurations,we experimentally illustrate how varying inter-resonator NF and FF couplings can drive the system to transit between different phase regions in a generic phase *** particular,we experimentally demonstrate that a realistic metasurface satisfying the discovered criteria exhibits the desired achromatic reflectionless property within 160-220 THz(0-225 THz in simulation),yet behaving as a perfect absorber at~203 *** findings pave the road to realize meta-devices exhibiting designable transmission/absorption spectra immune from reflections,which may find many applications in practice.

关键词： Metasurfaces Couplings Coupled-mode theory Kerker condition Perfect absorber