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Tensile deformation behavior of nickel-free high-manganese austenitic cryogenic-temperature steel

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Journal of Iron and Steel Research International 2022年第5期29卷 793-801页

作者： Xin-tian Wang Hui-bin Wu Yang Gu Li-xiong Xu Peng-cheng Zhang Qi-bo Tang National Center for Materials service Safety University of Science and Technology BeijingBeijing100083China Collaborative innovation Center of Steel technology University of Science and Technology BeijingBeijing100083China

Nickel-free high-manganese austenitic Fe–24.4Mn–4.04Al–0.057C steel was produced by smelting,and the homogenized forged billet was *** plastic deformation mechanism was investigated through tensile testing of the hot-rolled *** characterization techniques such as scanning electron microscopy,transmission electron microscopy,electron backscattered diffraction,and X-ray diffraction were used to analyze the microstructural evolution of steel under different strain *** steel had a single austenite phase,which was stable during *** hot rolling,annealing twins were observed in the microstructure of the *** steel showed an excellent combination of mechanical properties,like a tensile strength of 527 MPa,impact energy of 203 J at−196℃,and an elongation of 67%till *** the initial deformation stage,the dislocations were generated within the austenite grains,entangled and accumulated at the grain boundaries and annealing twin *** twins participated in plastic deformation and hindered the dislocation *** the deformation progressed,the dislocation slip was hindered and produced stress concentration,and the stacking faults evolved into mechanical twins,which released the stress concentration and delayed the necking.

关键词： High-manganese steel Austenite grain Tensile deformation Mechanical twin Annealing twin

Discrete Numerical Study on Type II Fracture of Partially Detached Concrete Panels in Cold Region

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Structural Durability & Health Monitoring 2025年第1期19卷 167-191页

作者： Huayi Zhang Maobin Song Lei Shen Nizar Faisal Alkayem Maosen Cao College of Water Conservancy and Hydropower Engineering Hohai UniversityNanjing210024China Haihe River Huaihe River and Xiaoqinghe River Basin Water Conservancy Management and Service Center of Shandong ProvinceJinan250100China College of Mechanics and Engineering science Hohai UniversityNanjing211100China

When the upper chord beam of the beam-string structure(BSS)is made of concrete-ﬁlled steel tube(CFST),its overall stiffness will change greatly with the construction of concrete placement,which will have an impact on the design of the tensioning plans and selection of control measures for the *** order to accurately obtain the bending stiffness of CFST beam and clarify its impact on the mechanical properties of composite BSS during con-struction,the inﬂuence of some factors such as height-width ratio,wall thickness of steel tube,elasticity modulus of concrete,and friction coefﬁcient on the bending stiffness are analyzed parametrically by the numerical simula-tion technology based on an actual *** calculation formula of the equivalent bending stiffness of CFST is also established through mathematical statistical ***,the equivalent bending stiffness is introduced into the construction and use stages of the composite BSS,respectively,and the mechanical properties such as prestress-tensioning control value,structural deformation,and internal force of key members are comparatively analyzed when adopting two different construction ***,the optimal construction plan of concrete placementﬁrst and then prestress-tensioning is proposed.

关键词： Beam-string structure(BSS) concrete-ﬁlled steel tube(CFST) bending stiffness timing of concrete placement prestress-tensioning

An Analysis of the Static and Dynamic Behavior of the Hydraulic Compensation System of a Multichannel Valve

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Fluid Dynamics & Materials Processing 2023年第7期19卷 1817-1836页

作者： Jikang Xu Ruichuan Li Yi Cheng Yanchao Li Junru Yang Chenyu Feng Xinkai Ding Huazhong Zhang College of Transportation Shandong University of Science and TechnologyQingdao266590China School of Mechanical and Automotive Engineering Qilu University of TechnologyJinan250353China College of Mechanical and Electronic Engineering Shandong University of Science and TechnologyQingdao266590China rizhao Haizhuo Hydraulic Co. Ltd.Rizhao276800China rizhao Polytechnic Rizhao276800China

Electro-hydraulic proportional valve is the core control valve in many hydraulic systems used in agricultural and engineering *** address the problem related to the large throttling losses and poor stability typically associated with these valves,here,the beneficial effects of a triangular groove structure on the related hydraulic response are studied.A mathematical model of the pressure compensation system based on the power-bond graph method is introduced,and the AMESim software is used to simulate its *** results show that the triangular groove structure increases the jet angle and effectively compensates for the hydrodynamic *** steady-state differential pressure at the valve port of the new pressure compensation structure was 0.65 ***,experimental results show that the pressure difference at the main valve port is 0.73 MPa,and that the response time is less than 0.2 *** is concluded that the new compensation structure has good pressure compensation response characteristics.

关键词： Electrohydraulic proportional valve spool shape pressure compensation valve port differential pressure response time

Stabilization Controller of An Extended Chained Nonholonomic System With Disturbance:An FAS Approach

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IEEE/CAA Journal of Automatica Sinica 2024年第5期11卷 1262-1273页

作者： Zhongcai Zhang Guangren Duan School of Engineering Qufu Normal UniversityRizhao 276826China Center for Control science and technology Southern University of Science and TechnologyShenzhen 518055 Center for Control Theory and Guidance technology Harbin Institute of TechnologyHarbin 150001China

This study examines the stabilization issue of extended chained nonholonomic systems(ECNSs)with external *** the existing approaches,we transform the considered system into a fully actuated system(FAS)model,simplifying the stabilizing controller *** implement a separate controller design and propose exponential stabilization controller and finite-time stabilization controller under finite-time disturbance observer(FTDO)for the two system *** addition,we discuss the specifics of global stabilization control *** approach demonstrates that two system states exponentially or asymptotically converge to zero under the provided switching stabilization control strategy,while all other system states converge to zero within a finite time.

关键词： design stabilization system

How Does Tropical Cyclone Size Affect the Onset Timing of Secondary Eyewall Formation？

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Journal of Meteorological Research 2018年第1期32卷 124-134页

作者： Liang GUAN Xuyang GE Collaborative innovation Center on Forecast and Evaluation of Meteorological Disasters/Key Laboratory of Meteorological Disaster Nanjing University of Information Science & Technology Nanjing 210044 Shanghai Meteorological science and technology service Center Shanghai 200030

By using idealized numerical simulations, the impact of tropical cyclone size on secondary eyewall formation（SEF） is examined. Both unbalanced boundary layer and balanced processes are examined to reveal the underlying mechanism. The results show that a tropical cyclone（TC） with a larger initial size favors a quicker SEF and a larger outer eyewall. For a TC with a larger initial size, it will lead to a stronger surface entropy flux, and thus more active outer convection. Meanwhile, a greater inertial stability helps the conversion from diabatic heating to kinetic ***, the progressively broadening of the tangential wind field will induce significant boundary layer imbalances. This unbalanced boundary layer process results in a supergradient wind zone that acts as an important mechanism for triggering and maintaining deep convection. In short, different behaviors of balanced and unbalanced processes associated with the initial wind profile lead to different development rates of the secondary eyewall.

关键词： secondary eyewall formation tropical cyclone size surface entropy flux

A modified θ projection model for constant load creep curves-Ⅱ.Application of creep life prediction

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Journal of Materials science & technology 2019年第4期35卷 687-694页

作者： Chao Fu Yadong Chen Xiaofei Yuan Sammy Tin Stoichko Antonov Koichi Yagi Qiang Feng Beijing Advanced innovation Center for Materials Genome Engineering State Key Laboratory for Advanced Metals and MaterialsUniversity of Science and Technology Beijing Department of Mechanical Materials& Aerospace EngineeringIllinois Institute of Technology National Center for Materials service Safety University of Science and Technology Beijing

To minimize the deviation of the predicted creep curves obtained under constant load conditions by the original θ projection model, a new modified version that can be expressed by ε = θ_1(1-e^(-θ2t)) +θ3 (e^(θ_4e^θ5^εt)-1), was derived and experimentally validated in our last study. In the present study, the predictive capability of the modified θ projection model was investigated by comparing the simulated and experimentally determined creep curves of K465 and DZ125 superalloys over a range of temperatures and stresses. Furthermore, the linear relationship between creep temperature and initial stress was extended to the 5-parameter model. The results indicated that the modified model could be used as a creep life prediction method, as it described the creep curve shape and resulted in predictions that fall within a specified error interval. Meanwhile, this modified model provides a more accurate way of describing creep curves under constant load conditions. The limitations and future direction of the modified model were also discussed. In addition, this modified θ projection model shows great potential for the evaluation and assessment of the service safety of structural materials used in components governed by creep deformation.

关键词： Superalloy Constant load creep Modified θ projection model Uniform deformation stage Prediction performance

A modified θ projection model for constant load creep *** of the model

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Journal of Materials science & technology 2019年第1期35卷 223-230页

作者： Chao Fu Yadong Chen Xiaofei Yuan Sammy Tin Stoichko Antonov Koichi Yagi Qiang Feng Beijing Advanced innovation Center for Material Genome Engineering State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Department of Mechanical Materials & Aerospace Engineering Illinois Institute of Technology National Center for Materials service Safety University of Science and Technology Beijing

Estimating long-term creep deformation and life of materials is an effective way to ensure the service safety and to reduce the cost of long-term integrity evaluation of high temperature structural *** the 1980 s, the θ projection model has been widely used for predicting creep lives due to its ability to capture the characteristic transitions observed in creep curves obtained under constant true stress conditions. However, the creep rupture behavior under constant load or engineering stress conditions cannot be simulated accurately using this model because of the different stress states. In this paper, creep curves obtained under constant load conditions were analyzed using a modified θ projection model by considering the increase in true stress with creep deformation during the creep tests. This model is expressed as ε = θ_1(1-e^(-θ_2t)) + θ3 e^(θ_4e^θ5^εt)-1, and was validated using the creep curves of K465 and DZ125 superalloys tested at a range of temperatures and engineering stresses. Moreover, it was shown that the predictive capability of the modified θ projection model was significantly improved over the original one, as it reduces the prediction uncertainty from a range of 10% to 20% to below 5%. Meanwhile,it was shown that the model can be reasonably used for predicting constant stress creep conditions, when appropriate parameters are used. The prediction performance of the modified model will be discussed in another paper. The results of this study show great potential for the evaluation and assessment of the service safety of structural materials used in applications where designs are limited by creep deformation.

关键词： Superalloy Creep Life prediction Modified θ projection model Constant load creep

Untangling the contributions of meteorological conditions and human mobility to tropospheric NO2 in Chinese mainland during the COVID-19 pandemic in early 2020

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National science Review 2021年第11期8卷 121-132页

作者： Yuxiang Zhang Haixu Bo Zhe Jiang Yu Wang Yunfei Fu Bingwei Cao Xuewen Wang Jiaqi Chen Rui Li School of Earth and Space sciences University of Science and Technology of China Comparative Planetary Excellence innovation Center Frontiers Science Center for Planetary Exploration and Emerging Technologies Chinese Academy of Sciences State Key Laboratory of Fire science University of Science and Technology of China Jiangxi Ecological Environment Monitoring Center Green Earth science and Education service

In early 2020,unprecedented lockdowns and travel bans were implemented in Chinese mainland to fight COVID-19,which led to a large reduction in anthropogenic *** provided a unique opportunity to isolate the effects from emission and meteorology on tropospheric nitrogen dioxide（NO;2;）.Comparing the atmospheric NO;2;in 2020 with that in 2017,we found the changes of emission have led to a49.3±23.5% reduction,which was～12% more than satellite-observed reduction of 37.8±16.3%.The discrepancy was mainly a result of changes of meteorology,which have contributed to an 8.1±14.2%increase of NO;2;.We also revealed that the emission-induced reduction of NO;2;has significantly negative correlations to human mobility,particularly that inside the *** intra-city migration index derived from Baidu Location-Based-service can explain 40.4%±17.7% variance of the emission-induced reduction of NO;2;in 29 megacities,each of which has a population of over 8 million in Chinese mainland.

关键词： atmospheric nitrogen dioxide anthropogenic emissions meteorology conditions human mobility COVID-19 quarantine

A Truncated SVD-Based ARIMA Model for Multiple QoS Prediction in Mobile Edge Computing

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Tsinghua science and technology 2022年第2期27卷 315-324页

作者： Chao Yan Yankun Zhang Weiyi Zhong Can Zhang Baogui Xin the College of Economic and Management Shandong University of Science and TechnologyQingdao 266590China Weifang Key Laboratory of Blockchain on Agricultural Vegetables Weifang University of Science and TechnologyWeifang 262700China the School of Computer science Qufu Normal UniversityRizhao 276826China

In the mobile edge computing environments,Quality of service(QoS)prediction plays a crucial role in web service *** of distinct features of mobile edge computing,i.e.,the mobility of users and incomplete historical QoS data,traditional QoS prediction approaches may obtain less accurate results in the mobile edge computing *** this paper,we treat the historical QoS values at different time slots as a temporal sequence of QoS *** incorporating the compressed matrices extracted from QoS matrices through truncated Singular Value Decomposition(SVD)with the classical ARIMA model,we extend the ARIMA model to predict multiple QoS values simultaneously and *** results show that our proposed approach outperforms the other state-of-the-art approaches in accuracy and efficiency.

关键词： edge computing QoS prediction Auto Regressive Integrated Moving Average(ARIMA) truncated Singular Value Decomposition(SVD)