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Unified simulation of hardening and softening effects for metals up to failure

Applied Mathematics and Mechanics(English Edition) 2021年第12期42卷 1685-1702页

作者： Siyu WANG Lin ZHAN Huifeng XI O.T.BRUHNS Heng XIAO School of Mechanics and Construction Engineering MOE Key Lab of Disaster Forecast and Control in EngineeringJinan UniversityGuangzhou 510632China Institute of Mechanics Ruhr-University BochumBochum D-44780Germany

Toward accurately simulating both hardening and softening effects for metals up to failure,a new finite strain elastoplastic J2-flow model is proposed with the yield strength therein as a function of the plastic work in the explicit *** no need to identify any adjustable parameters,the uniaxial stress-strain response predicted from this new model is shown to automatically and accurately match any given data from monotonic uniaxial extension tests of *** such,the objectives in three respects are achieved for the first time,i.e.,(i)both the hardening and softening effects up to failure can be simulated in the sense of matching test data with no errors,(ii)the usual tedious implicit procedures toward identifying numerous unknown parameters need not be involved and can be totally bypassed,and(iii)the model applicability can be ensured in a broad sense for various metallic materials with markedly different transition effects from hardening to *** the new model,the complete response features of stretched bars and twisted tubes up to failure are studied,including the failure effects of bars under monotonic extension and tubes under monotonic torsion and,furthermore,the fatigue failure effects of bars under cyclic *** results show accurate agreement with the uniaxial data,and the results for both the shear stress and the normal stress at the finite torsion display realistic hardening-to-softening transition effects for the first time.

关键词： metal hardening softening failure necking yield strength accurate approach

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2D Green's function of orthotropic two-coating-substrate under a normal line force

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APPLIED MATHEMATICAL MODELLING 2023年第1期122卷 665-692页

作者： Wan, Guang-Quan Zhang, Wen-Hua Jinan Univ MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China Jinan Univ Sch Mech & Construct Engn Guangzhou 510632 Peoples R China Hunan Univ Coll Mech & Vehicle Engn Changsha 410082 Peoples R China

The study of multi-layer coating structure is an important problem in the fields of machinery and materials. In this paper, a two-dimensional theoretical solution of the orthotropic double-coated substrate structure under the normal line force of the free surface is derived. The method in this paper is mainly aimed at orthotropic materials and falls within the scope of linear elasticity. Based on the general solution of two-dimensional orthotropic materials, the harmonic functions with undetermined constants corresponding to each region are constructed. With the equilibrium conditions, surface boundary conditions and interface continuity conditions, the full-field analytical solution (Green's function) expressed in elementary functions is determined with the method of mirror images, which is valuable to solve the full field analytical expression of layered structures for the linear elasticity problem. Compared with the existing theories, the effectiveness and accuracy of the method are verified. In the future, Green's function of the paper is the basis for the numerical integration of distributed loads, which can be used as the code basis for the development of special software to study ultra-precision coatings.& COPY;2023 Elsevier Inc. All rights reserved.

关键词： Orthotropic Coating -substrate Green's function Theoretical solution Normal line force

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Integrating L1 and weighted L2 regularization for moving force identification from combined response measurements

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MEASUREMENT 2024年 228卷

作者： Hou, Zhilong Yu, Ling Liang, Yi Xu, Bohao Lei, Yuandong Jinan Univ Sch Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China

Existing regularization methods have been proven effective in the ill-posed problem of moving force identification (MFI). However, both the constant and time-varying components of moving forces cannot be accurately identified at the same time, especially under higher measurement noises. To address this issue, a new MFI method is proposed by integrating the L1 and weighted L2 regularization methods in this study, where the presented weighted L2 regularization strategy achieves a more nuanced balance of moving force components through the incorporation of weight coefficients. Furthermore, the inherent solving characteristics of L1 and weighted L2 regularization methods are fully utilized to solve different components in moving forces separately. Numerical simulations and experimental verifications are carried out to assess the effectiveness of the proposed method. The results show that the proposed method can accurately identify moving forces even under 25% higher noise levels and it can effectively evaluate the axle loads and gross vehicle weight of the experimental vehicle. Besides, comparative studies further show that the proposed method outperforms the existing L1 and L2 regularization methods in the identification of both constant and time-varying forces, which provides a potential MFI tool for a higher accuracy and noise robustness to fix the MFI problem in practice.

关键词： Moving force identification (MFI) Structural health monitoring (SHM) Response separation Sparse regularization Tikhonov regularization

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A parametric analysis of the "digitally-derived geometric design" of the facade of the Macau Holy house of Mercy

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JOURNAL OF ASIAN ARCHITECTURE AND BUILDING engineering 2022年第4期21卷 1230-1243页

作者： Tang, Jian Jinan Univ Key Lab Disaster Forecast & Control Engn MOE China Guangzhou Peoples R China Guangdong Engn Technol Res Ctr Green Bldg Mat & Fabricated Architecture Maoming Peoples R China

The Macau Holy House of Mercy was built in 1569 and rebuilt in the 18th century. Located in the historic center of Macao, the Macau Holy House of Mercy is included on the World Heritage List of *** the Macau Holy House of Mercy, especially the facade of its neo-classical arcade added in 1905, as the research subject, this study applied the methods of historical document research, field measurement and digital analysis, especially parametric analyses with the assistance of the modeling software of Rhinoceros 6.0 and the software plug-in of Grasshopper. And the following results were obtained: 1) its designers applied three-section partition in the horizontal and vertical directions and equal division in stratification in the overall dimension of the facade;2) its designers also applied modularization (modular) design and combination in the columns and details of doorways;3) this study found that the (successive) partition of the facade is closer to the "Golden Section" than "Root Rectangle Partition";further analyses discovered the Golden Rectangle and Golden Spiral (successive division) in the facade. The underlying aesthetics-mathematics pattern of "digitally-derived geometric design" is of significant historical value.

关键词： The Macau Holy house of Mercy facade parametric analysis golden ration modularization

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Forced Vibration of Time-Varying Elevator Traction System

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STROJNISKI VESTNIK-JOURNAL OF MECHANICAL engineering 2024年第3-4期70卷 170-180页

作者： Sun, Jie Xu, Peng Chen, Mingli Xue, Jianghong Jinan Univ Sch Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou Peoples R China Qingdao Xinghua Intelligent Equipment Co Qingdao Peoples R China South China Univ Technol Sch Civil Engn & Transportat Guangzhou Peoples R China Jinan Univ Guangzhou Guangdong Peoples R China

This paper proposes a theoretical model for the forced vibration of time-varying elevator traction systems caused by eccentric excitation of the traction machine. Based on the Hamilton principle and a variational principle with variable boundaries, the equations of motion and the complex boundary condition of a time-varying elevator traction system are established. A quantitative formula between the angular velocity of the traction machine, the diameter of the traction wheel, the elevator running distance and the running time is put forward. It is found that when the maximum values of acceleration and deceleration exceed 1.5 m/s2, the elevator traction system may undergo resonance.

关键词： elevator traction system vibration time -varying dynamics numerical analysis

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A new and direct approach toward modeling gradual strength degradation of metal beams under cyclic bending up to fatigue failure

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MULTIDISCIPLINE MODELING IN MATERIALS AND STRUCTURES 2022年第3期18卷 502-517页

作者： Xiao, Heng Li, Zi-Tao Zhan, Lin Wang, Si-Yu Jinan Univ Sch Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou Peoples R China Zhejiang Univ State Key Lab Fluid Power & Mechatron Syst Key Lab Soft Machines & Smart Devices Zhejiang Pr Dept Engn Mech Hangzhou Peoples R China

Purpose The purpose of this study is to show how gradual strength degradation of metal beams under cyclic bending up to fatigue failure is simulated based on a new elastoplasticity model free of any yield criterion. Design/methodology/approach A new approach is proposed toward accurately and explicitly prescribing evolution of non-uniform stress distribution on beam cross-section under cyclic bending and, as such, gradual degradation of the bending strength can be directly determined. Findings Explicit results for the bending response in a whole cyclic process up to fatigue failure are obtained and the fatigue characteristic curve is for the first time simulated directly between the curvature amplitude and the cycle number to failure. Originality/value First, explicit and accurate determination of the non-uniform stress distribution on beam cross-section is achieved with asymptotic softening effects. Second, degradation of the bending strength can be directly deduced cycle by cycle. Finally, the relationship between the bending moment and the curvature is calculated using new and efficient numerical algorithms, thus bypassing usual time-consuming calculations with finite element procedures. Numerical results are presented and in good agreement with experimental data.

关键词： Pure bending Cyclic response Bending strength Gradual degradation Fatigue failure

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Tomographic inversion of OBS converted shear waves:case study of profile EW6 in the Dongsha area

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Acta Oceanologica Sinica 2024年第8期43卷 13-25页

作者： Genggeng Wen Kuiyuan Wan Shaohong Xia Xiuwei Ye Huilong Xu Chaoyan Fan Jinghe Cao Shunshan Xu CEA Key Laboratory of Earthquake Monitoring and Disaster Mitigation Technology Guangdong Earthquake AgencyGuangzhou 510070China Guangdong Science and Technology Collaborative Innovation Center for Earthquake Prevention and Disaster Mitigation Guangzhou 510070China MOE Key Laboratory of Disaster Forecast and Control in Engineering-Urban Earthquake Safety Laboratory Guangzhou 510070China CAS Key Laboratory of Ocean and Marginal Sea Geology South China Sea Institute of OceanologyChinese Academy of SciencesGuangzhou 510301China Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou) Guangzhou 511458China 6 Centro de Geociencias Universidad Nacional Autónoma de MéxicoQuerétaroC.P.76230Mexico

Studies of converted S-wave data recorded on the ocean bottom seismometer(OBS)allow for the estimation of crustal S-wave velocity,from which is further derived the Vp/Vs ratio to constrain the crustal lithology and geophysical *** a precise S-wave velocity model is important for deep structural research,and inversion of converted S-waves provides a potential ***,the inversion of the converted S-wave remains a weakness because of the complexity of the seismic ray path and the inconsistent conversion *** this study,we introduced two travel time correction methods for the S-wave velocity inversion and imaged different S-wave velocity structures in accordance with the corresponding corrected S-wave phases using seismic data of profile EW6 in the northeastern South China Sea(SCS).The two inversion models show a similar trend in velocities,and the velocity difference is<0.15 km/s(mostly in the range of 0–0.1 km/s),indicating the accuracy of the two travel time correction methods and the reliability of the inversion *** to simulations of seismic ray tracing based on different models,the velocity of sediments is the primary influencing factor in ray tracing for S-wave *** the sedimentary layer has high velocities,the near offset crustal S-wave refractions cannot be *** contrast,the ray tracing of Moho S-wave reflections was not significantly impacted by the velocity of the *** two travel time correction methods have their own advantages,and the application of different approaches is based on additional *** works provide an important reference for future improvements in converted S-wave research.

关键词： converted S-wave S-wave velocity structure inversion ocean bottom seismometer northeastern South China Sea

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Comparative studies on Structural Damage Detection using different kinds of Objective Functions based on Modal Data

Comparative studies on Structural Damage Detection using dif...

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2022 International Conference on Intelligent Transportation, Big Data and Smart City, ICITBS 2022

作者： Chen, Zepeng Zhao, Di Foshan University School of Transportation and Civil Engineering & Architecture Foshan528225 China Jinan University Moe Key Lab of Disaster Forecast and Control in Engineering Guangzhou510632 China

ISBN: (纸本)9781665497213

In order to investigate the ability of different objective functions based on modal data for SDD problems, six objective functions are defined and a comparison study is presented in this paper. To make a fair comparison, a quantified index name damage vector consistency is defined to describe the consistency between the identified damage vector factor and the assume one. Simply-supported beam with 10 finite elements is simulated which provides modal data generation and damage cases simulation. The percentage of DVC equaling to 100% in the all 100 times is also calculated which shows the objective function based on MTMAC is the best one for SDD. © 2022 IEEE.

关键词： Modal analysis

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A general electrochemical peridynamic model for corrosion and electrodeposition

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JOURNAL OF ELECTROANALYTICAL CHEMISTRY 2024年 968卷

作者： Tian, Chenwen Du, Juan Fan, Shuaiqi Chen, Ziguang Huazhong Univ Sci & Technol Dept Engn Mech Wuhan 430074 Peoples R China Nucl Power Inst China Sci & Technol Reactor Syst Design Technol Lab Chengdu 610213 Peoples R China Hubei Key Lab Engn Struct Anal & Safety Assessment 1037 Luoyu Rd Wuhan 430074 Peoples R China Jinan Univ Sch Mech & Construction Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China

In this paper, we introduce a general electrochemical peridynamic formulation to model both corrosion and electroplating processes. Unlike the previous bi-material diffusion-based peridynamic model that combines the chemical reaction and the ion transfer terms into an effective bi-material diffusion term, the new model distinctly separates the reaction term from the effective diffusion term. This treatment allows for convenient calibration of the electrochemical reaction term, and facilitates the accurate reproduction of intricate and comprehensive electrochemical reaction processes, such as pitting corrosion with repassivation and electrodeposition, within a unified framework. The new electrochemical model is validated against the experimental results for uniform corrosion and complex pitting corrosion, and the new model achieves higher accuracy than the bi-material diffusion-based model. Besides the examples shown in this paper, the model can also be applied to other electrochemical processes, such as galvanic corrosion, crevice corrosion, charging and discharging in lithium batteries, etc.

关键词： Corrosion Electrodeposition Peridynamic modeling Repassivation Reaction-diffusion

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Interfacial properties of CFRP sheets and concrete subjected to variable amplitude fatigue loading

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STRUCTURAL CONCRETE 2021年第4期22卷 1927-1945页

作者： Yuan, Hong Luo, Guangyun Liu, Chang Zeng, Lan Jinan Univ Sch Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China

In order to better understand the interfacial fatigue behavior of concrete and fiber-reinforced polymer (FRP), bending fatigue tests were conducted on plain concrete beams strengthened with carbon FRP (CFRP) sheets under variable amplitude cyclic loading which deteriorates structural performance in actual projects more dramatically than constant amplitude loading. The test parameters were four types of loading modes including static loading, constant amplitude cyclic loading, alternating amplitude cyclic loading and incremental amplitude cyclic loading. Miner damage rule, modified Miner damage rule and Corten-Dolan cumulative damage rule were used to predict the fatigue life of specimens. The relationship between loads and deflections, the relationship between strains and cycle times and the crack propagation were analyzed. The results have shown that the fatigue life of specimens under variable amplitude cyclic loading, especially alternating one, is shorter than that of specimens under constant one, and the modified Miner damage rule is more suitable to predict fatigue life. The crack lengths on the lateral faces of beams recorded by digital image correlation (DIC) method developed more slowly than those at the bottom sides recorded by strain gauges. A proposed damage model describing the relationship between the crack lengths and fatigue life for specimens under alternating amplitude fatigue loading is consistent with the experimental results well.

关键词： carbon fiber reinforced polymer (CFRP) concrete reinforcement crack length interfacial properties variable amplitude fatigue loading

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