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Creep buckling of long-term-serving super-heating pipes in boilers subjected to high temperature loading

INTERNATIONAL JOURNAL OF PRESSURE VESSELS AND PIPING 2022年 200卷

作者： Zhao, Chen Xiong, Ying Liu, Yixuan Xue, Jianghong Xu, Peng Jinan Univ Sch Civil & Construction Engn Key Lab Disaster Forecast & Control Engn Minist Educ Guangzhou 510632 Peoples R China

This paper proposes a novel approach to scrutinize the creep buckling of the super-heating pipes in boilers subjected to external pressure in high temperature environment. It is well known that once buckling occurs, cylindrical shells will collapse instantly. As the load carrying capability of the cylindrical shell decreases sharply upon the occurrence of the buckling, the proposed analysis is based on the consideration that the creep will have a significant influence on the material properties only in the pre-buckling stage. According to the creep aging theory, the influence of the creep deformation on the mechanical response of the super-heating pipes is defined by introducing two parameters-the reduced Young's modulus and the reduced Poisson's ratio. The nonlinear constitutive relation for creep deformation of the super-heating pipes in high-temperature environment is established based on the deformation theory in mechanics of plasticity. Governing equations for creep buckling of super-heating pipes in boilers are derived by considering the extra change of curvature due to the initial curvature of the super-heating pipes. MATlab programs are developed based on the analytical expression for super-heating pipes with simply supported boundary conditions at the two ends and are tested against the available experimental results and the finite element prediction from ABAQUS software. It is found that the components of the creep strain caused by the stress at high temperature far exceeds those of the elastic strain. As a results of that, the creep buckling load of the super-heating pipes is much lower than its elastic buckling load. From this study, an explicit expression to compute the creep buckling load is provided which facilitates engineer to easily predict the residual life of the super-heating pipes at different servo temperature and servo time.

关键词： Cylindrical shell Super -heating pipes in boilers Creep buckling Creep aging theory

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Effect of grain refinement induced by wire and arc additive manufacture (WAAM) on the corrosion behaviors of AZ31 magnesium alloy in NaCl solution

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Journal of Magnesium and Alloys 2023年第1期11卷 217-229页

作者： Jianwei LI Youmin QIU Junjie YANG Yinying SHENG Yanliang YI Xun ZENG Lianxi CHEN Fengliang YIN Jiangzhou SU Tiejun ZHANG Xin TONG Bin GUO School of Materials Science and Engineering Harbin Institute of TechnologyHarbin 150001PR China Beijing Hangxing Machinery Manufacture Limited Corporation Beijing 100013PR China Institute of Advanced Wear&Corrosion Resistant and Functional Materials Jinan UniversityGuangzhou 510632PR China The Third Academy of CASIC Beijing 100074PR China MOE Key Lab of Disaster Forecast and Control in Engineering Jinan UniversityGuangzhou510632P.R.China Institute of Materials and Process Design Helmholtz-Zentrum HereonMax-Planck-Str.121502 GeesthachtGermany School of Materials Science and Hydrogen Energy Foshan UniversityFoshan 528000PR China

Additive manufacturing(AM)of Mg alloys has become a promising strategy for producing complex structures,but the corrosion performance of AM Mg components remains *** this study,wire and arc additive manufacturing(WAAM)was employed to produce single AZ31 *** results revealed that the WAAM AZ31 was characterized by significant grain refinement with non-textured crystallographic orientation,similar phase composition and stabilized corrosion performance comparing to the cast *** varied corrosion behaviors were principally ascribed to the size of grain,where cast AZ31 and WAAM AZ31 were featured by micro galvanic corrosion and intergranular corrosion,respectively.

关键词： AZ31 magnesium alloy Wire and arc additive manufacturing(WAAM) Grain refinement Microstructure Intergranular corrosion

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Damage detection in bridges under moving loads based on subspace projection residuals

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ADVANCES IN STRUCTURAL engineering 2022年第5期25卷 979-1001页

作者： Nie, Zhenhua Xie, Yongkang Li, Jun Hao, Hong Ma, Hongwei Jinan Univ Sch Mech & Construct Engn Guangzhou Guangdong Peoples R China Minist Educ China Key Lab Disaster Forecast & Control Engn Guangzhou Guangdong Peoples R China Curtin Univ Sch Civil & Mech Engn Ctr Infrastruct Monitoring & Protect Kent St Bentley WA Australia Dongguan Univ Technol Dongguan Peoples R China

This paper proposes a data-driven method using subspace projection residual of the responses to identify the damage locations in bridges subjected to moving loads. In this method, a moving window with a certain length determined by the sampling frequency and the fundamental frequency of the measured responses is used to cut out the acceleration responses of the bridge subjected to a moving vehicle. The characteristic subspaces of the windowed signals are subsequently extracted to calculate the local damage index using the subspace projection residual. When the window moves to the damage location, the orthogonality between the active subspace of the damaged state and the null subspace of the healthy state is invalid, which leads to a relatively large projection residual that can be used to localize the damage. To improve the reliability of the proposed approach, a one-side upper confidence limit is introduced. A simply supported beam bridge subjected to a moving mass is simulated to verify the effectiveness of the proposed method. Numerical results indicate that the proposed approach can accurately localize the single and multiple damages, even when the responses are smeared with a significant noise. Experimental tests conducted on a steel beam bridge model also demonstrate the performance and accuracy of the proposed approach. The results demonstrate that the proposed method can localize the damage even with a small number of sensors, indicating the method has a good and promising performance for practical engineering applications.

关键词： data-driven structural damage localization subspace projection residual moving loads limited number of sensors

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Predominant types of regional cold waves in North China and their historical changes

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Atmospheric and Oceanic Science Letters 2024年第4期17卷 46-51页

作者： Xinyi Cheng Yiyi Zhang Jiandong Li Xin Hao Center for Climate System Prediction Research/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters/Key Laboratory of Meteorological Disaster Ministry of EducationNanjing University of Information Science&TechnologyNanjingChina Nansen-Zhu International Research Centre Institute of Atmospheric PhysicsChinese Academy of SciencesBeijingChina Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control Jiangsu Collaborative Innovation Center of Atmospheric Environment and Equipment TechnologySchool of Environmental Science and EngineeringNanjing University of Information Science&TechnologyNanjingChina

寒潮事件对东亚地区的社会经济,生态系统和人体健康影响巨大.根据1980-2019年间10月至次年3月的每日寒潮记录和K-means聚类,本文识别出了中国两种不同类型的区域性寒潮(T1和T2). T1区域性寒潮主要影响东北地区,T2区域性寒潮则主要影响... 详细信息

寒潮事件对东亚地区的社会经济,生态系统和人体健康影响巨大.根据1980-2019年间10月至次年3月的每日寒潮记录和K-means聚类,本文识别出了中国两种不同类型的区域性寒潮(T1和T2). T1区域性寒潮主要影响东北地区,T2区域性寒潮则主要影响华北和东部地区.与T1区域性寒潮相比, T2区域性寒潮强度更强,持续时间更长,影响范围更广. 1980–2019年期间, T1区域性寒潮的频率显著增加,而T2区域性寒潮的频率则没有趋势变化. T1和T2区域性寒潮事件均与西伯利亚高压增强有关,然而与它们相关的对流层中层波列明显不同.在T1区域性寒潮事件发生期间,西伯利亚-蒙古上空出现负-正模态的500-hPa位势高度异常波列,削弱了东亚大槽,导致西伯利亚冷空气东移.T1区域寒潮频次增加趋势可能与全球变暖引起的500-hPa位势高度的线性趋势变化有关.与T2区域寒潮事件相关的波列则在乌拉尔山脉,蒙古和华北地区形成了脊-槽-脊环流异常,导致冷空气向东南方向入侵.本文得出结论,由于两类区域寒潮影响不同,西伯利亚高压增强和对流层中层波列模态在我国区域性寒潮事件的预报中应综合考虑.

关键词：寒潮 K-means聚类西伯利亚高压波列

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Damage evaluation of steel frame subjected to impact load at midspan

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ce/papers 2023年第3-4期6卷 1202-1206页

作者： Chen, Ying Chen, Wensu Hao, Hong Nie, Zhenhua Jinan University Guangzhou China The Key Laboratory of Disaster Forecast and Control in Engineering Guangzhou China Curtin University Curtin Australia Guangzhou University Guangzhou China

The lower floors of the multi-storey structure can be impacted by the debris from the upper floor caused by gas and bomb explosion, which may induce damage or failure of the impacted substructure and lead to progressive collapse of large-scale structure. The behavior of the frame with a steel beam and two adjacent beam-column joints was numerically analyzed when the beam was impacted at midspan by various combinations of impact mass and velocity. The failure mode of the joints, the impact load and midspan displacement were analyzed. It shows that the beam-column joint fails prior to the beam under all impact loading scenarios. The residual bearing capacity of the frame was also studied by statically pushing-down the substructure after impact loading. A damage index was proposed using the residual capacity of the frame after impact loading divided by the static capacity of the joint without impact loading, and four damage levels, i.e., the minor damage, medium damage, severe damage, and collapse, were defined by the damage index. The boundaries of different damage levels of the frame under various impact loads were fitted, and it can be used to evaluate the damage level of the frame subjected to possible impact loads. © 2023 Ernst & Sohn GmbH.

关键词： Floors

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A numerical analysis of sloshing dynamics of two-layer liquid with a free surface

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OCEAN engineering 2023年第1期268卷

作者： Cao, Weinan Li, Xiaoming Gao, Ying Li, Xiaochen Liu, Zeng South China Univ Technol Sch Civil Engn & Transportat Guangzhou 510630 Peoples R China Jinan Univ Sch Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China Imperial Coll London Dept Earth Sci & Engn London SW7 2BX England Huazhong Univ Sci & Technol Sch Naval Architecture & Ocean Engn Wuhan 430074 Peoples R China

A numerical study on the two-layer liquid sloshing with a free surface in a rectangular tank under horizontal sinusoidal excitation is investigated in this work. It is observed that the interface displacement is mainly influenced by the lower liquid depth, while the free surface displacement primarily depends on the total liquid depth. Using dimensional analysis of the numerical results, we obtained a fitting curve in the S-model expression, which relates the displacements of both liquids to the forcing amplitude, forcing frequency and liquid depth. Furthermore, distinct from the phenomena for a single-layer liquid, we find that the sum and difference frequencies play significant roles in the power spectral density curves. There are similar power spectral density curve shapes and energy concentration locations with a fixed type of excitation independent of the liquid filling depth and layer depths ratio.

关键词： Two-layer liquid sloshing Numerical analysis Dimensional analysis Power spectral density

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Stress intensity factor for a circumferential crack in a coke drum under two-dimensional transient temperature distribution

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INTERNATIONAL JOURNAL OF PRESSURE VESSELS AND PIPING 2022年 200卷

作者： Wang, Zhiwen Ning, Zhihua Liu, Renhuai Jinan Univ Sch Mech & Construction Engn Key Lab Disaster Forecast & Control Engn Minist Educ China Guangzhou 510632 Peoples R China

Coke drums are subjected to extreme temperature cycling in service, leading to circumferential cracking in the drum wall. For a deeper understanding in the cracking mechanism, stress intensity factor (SIF) for a circumferential crack in a coke drum was investigated in this paper. Based on two-dimensional heat conduction theory and classical thin shell theory, analytical solutions for the transient temperature distribution, displacement, and thermal stress in the drum wall during hot feed filling and water quench steps were determined. The weight function method (WFM) was applied to investigate the mode I SIFs based on the analytical thermal stress solutions. Numerical simulations using finite element method (FEM) were also performed to validate the analytical solutions for both the thermos-elastic field and the SIFs. The effects of shell geometry, operating parameters and material properties on the SIF during the water quench step were discussed. It is shown that the SIF increases significantly as crack depth increases. A greater shell thickness or lower diameter to thickness ratio results in lower SIFs. Lower rising rate and higher temperature of quench water can reduce the SIF. The SIF increases as the thermal conductivity and thermal expansion coefficient of the drum wall materials increase. Finally, the SIFs for Cr-Mo steel and carbon steel coke drums are also discussed.

关键词： Coke drum Stress intensity factor Transient temperature distribution Circumferential crack Weight function

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An accurate and parameter-free analysis for the converse Poynting effect in large constrained torsion of highly elastic soft tubes

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ZAMM-ZEITSCHRIFT FUR ANGEWANDTE MATHEMATIK UND MECHANIK 2024年第2期104卷

作者： Tan, Long-Xu Kang, Jia Liu, Quan-Pu Wang, Si-Yu Bruhns, Otto Xiao, Heng Jinan Univ Sch Mech & Construct Engn Guangzhou 510632 Peoples R China Jinan Univ MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China Ruhr Univ Bochum Inst Mech D-44780 Bochum Germany

New exact solutions to large constrained torsion of highly elastic soft tubes are obtained from a new hyper-elastic constitutive model. This new model is established with a new form of the multiaxial elastic potential toward simultaneously matching multiple data sets for three benchmark modes, including the uniaxial extension of a bar, the equi-biaxial extension of a thin plate and the plane-strain extension of a plate strip. With the new model, exact closed-form solutions to the stress responses for these benchmark modes are first derived and shown to be of decoupled nature, and, then, an accurate analysis for the converse Poynting effect of twisted highly elastic tubes with fixed ends is presented with a new technique in treating nonlinear coupling complexities. The main novelties are incorporated as follows. First, multiple data sets for three benchmark modes can be accurately and automatically matched with no need to identify any unknown parameters;next, the nonlinear coupled system of the governing equations for four variables in a twisted tube, including the averaged radius and the wall-thickness as well as the axial constrained stress and the shear stress, can be reduced to treating a single nonlinear equation;and, accordingly, the nonlinear coupling complexities can be worked out and exact results are obtainable.

关键词： Torsional stress

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Simplified analytical model for prediction of collapse resistance of restrained steel beam-column substructure exposed to fire

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engineering FAILURE ANALYSIS 2024年 159卷

作者： Guo, Zhan Cai, Wei Nie, Zhenhua Chen, Yu Jinan Univ Sch Mech & Construction Engn Guangzhou 510632 Peoples R China Jinan Univ MOE Key Lab Disaster Forecast & Control Engn Guangzhou Peoples R China Fuzhou Univ Coll Civil Engn Fuzhou 350116 Peoples R China

This paper provides a simplified analytical model for the restrained steel beam-column substructure under a fire-induced progressive collapse scenario, which is applied to predict the collapse resistance of substructures under fire. The simplified model is formulated for axially and rotationally restrained two-span steel beam-column substructures under column-loss scenarios and involves rigid and semi-rigid connections. The response characteristics of restrained substructures exposed to fire under column-loss scenarios in each response stage are elaborately analyzed. A "negative" catenary stage, in consideration of the unique negative axial force effects induced by the temperature thermal expansion, was first introduced in the five-stage simplified model for restrained substructures exposed to fire against progressive collapse. Subsequently, the explicit calculation formulas for determining the vertical loads and deflection of both rigid and semi-rigid joint substructures exposed to fire were derived in a quantified way, based on rigidplastic mechanisms and restraint coefficient methods. In addition, the corresponding numerical simulation analysis on a restrained two-span steel beam-column substructure with different end constraints and fire conditions was carried out to verify the applicability and reliability of established theoretical formulas. Comparisons of vertical load-deflection relationships between the calculation formulas and corresponding numerical simulation shows good accuracy. For more accurate prediction results, the error analysis was further conducted, and several theoretical formulas were modified, which were verified to be accurate and reliable after correction. With derived resistance functions, the resistance of steel beam-column substructures in fire-induced progressive collapse scenarios can be predicted.

关键词： Simplified analytical model Restrained beam-column substructure Collapse resistance Fire condition Numerical simulation Error analysis

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Multi-strategy structural damage detection based on included angle of vectors and sparse regularization

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STRUCTURAL engineering AND MECHANICS 2020年第4期75卷 415-424页

作者： Liu, Huanlin Yu, Ling Luo, Ziwei Chen, Zexiang Jinan Univ Sch Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China

Recently, many structural damage detection (SDD) methods have been proposed to monitor the safety of structures. As an important modal parameter, mode shape has been widely used in SDD, and the difference of vectors was adopted based on sensitivity analysis and mode shapes in the existing studies. However, amplitudes of mode shapes in different measured points are relative values. Therefore, the difference of mode shapes will be influenced by their amplitudes, and the SDD results may be inaccurate. Focus on this deficiency, a multi-strategy SDD method is proposed based on the included angle of vectors and sparse regularization in this study. Firstly, inspired by modal assurance criterion (MAC), a relationship between mode shapes and changes in damage coefficients is established based on the included angle of vectors. Then, frequencies are introduced for multi-strategy SDD by a weighted coefficient. Meanwhile, sparse regularization is applied to improve the ill-posedness of the SDD problem. As a result, a novel convex optimization problem is proposed for effective SDD. To evaluate the effectiveness of the proposed method, numerical simulations in a planar truss and experimental studies in a six-story aluminum alloy frame in laboratory are conducted. The identified results indicate that the proposed method can effectively reduce the influence of noises, and it has good ability in locating structural damages and quantifying damage degrees.

关键词： structural damage detection (SDD) multi-strategy method sparse regularization included angle of vectors

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