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24th Australasian Conference on the Mechanics of Structures and Materials, ACMSM 2016

作者： Pan, Chudong Yu, Ling Department of Mechanics and Civil Engineering Jinan University Guangzhou China MOE Key Laboratory of Disaster Forecast and Control in Engineering Jinan University Guangzhou China

ISBN: (纸本)9781138029934

Moving Force Identification (MFI) and Structural Damage Detection (SDD) are two important issues in the field of bridge Structural Health Monitoring (SHM). Based on sparse regularization L1/2 optimization techniques, a novel MFI-SDD method is proposed for identifying both moving forces and structural damages by using structural responses only. First of all, some measurement sensors in a structure can be divided into two sets. The relationship between them can be expressed by transmissibility concept. With a given damage vector, structural responses can be rebuilt by using transmissibility matrix. The SDD process is to find possible damages which make the difference between measured and rebuilt responses minimum. The L1/2 regularization is added to acquire a sparse damage vector. Secondly, the moving forces can be identified by Tikhonov regularization method with the SDD results. In order to assess accuracy and feasibility of the proposed method, a damaged simply-supported beam bridge subjected to moving forces is taken as an example for numerical simulations. The illustrated results show that the proposed method can simultaneously identify both moving forces and structural damages with a good accuracy and better robustness to noise. Some related issues are discussed as well. © 2017 Taylor & Francis Group, London.

关键词： Structural health monitoring

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Research on pipeline chaos detection based on ultrasonic guided wave 24th

Research on pipeline chaos detection based on ultrasonic gui...

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24th Australasian Conference on the Mechanics of Structures and Materials, ACMSM 2016

作者： Wen, Yuli Ma, Hongwei College of Science and Engineer Jinan University Guangzhou China Key Lab of Disaster Forecast and Control in Engineering Ministry of Education Guangzhou China School of Civil Engineering Qinghai University Xining China

ISBN: (纸本)9781138029934

This article presents a study on weak ultrasonic guided waves signal processing. In long range detection or small defect detection, the defect echo often shows the characteristic of weak signal because of attenuation, which becomes the main obstacles of ultrasonic guided waves detection. Due to the sensitive dependence on initial condition and strong noise immunity of chaotic system, Duffing chaotic oscillator weak signal detection method based on ultrasonic guided wave has been proposed. When the critical chaotic system detect the weak signal, the system state will be change. The parameters of chaotic system was determined according to the ultrasonic guided wave detection. The maximum Lyapunov exponent is chosen to detect the system state change. The chaotic oscillator is proved to have good immunity to noise by using chaotic system to process different amplitudes of Gaussian white noise. Four kinds of section reduction ratio defects are analyzed respectively. The method has been verified to be useful to expand range and improve the sensitivity in pipes defect detection by the results of numerical simulations and experiments on 6 meters pipeline. © 2017 Taylor & Francis Group, London.

关键词： Chaotic systems

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Direct modeling of multi-axial fatigue failure for metals

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INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES 2017年 125卷 216-231页

作者： Wang, Zhao-Ling Xiao, Heng Jinan Univ Sch Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Guangdong Peoples R China Weifang Univ Sch Math & Informat Sci Weifang 261601 Shandong Peoples R China

Innovative elastoplastic J(2) flow models with nonlinear combined hardening are proposed for the purpose of simulating multi-axial thermo-coupled fatigue failure for metals and alloys, in a direct sense without involving any usual damage-like variables and any ad hoc failure criteria. As contrasted with usual models, the yield condition and the loading-unloading conditions need not be imposed as extrinsic coercive conditions but may be automatically incorporated into a free, smooth flow rule in a more realistic sense. Novel results in three respects are available directly from model predictions, namely, (i) complex features of thermo-coupled fatigue failure may be automatically represented by simple asymptotic properties of the hardening functions introduced, (ii) critical failure states may be derived with a criterion in unified form, and, in particular, (iii) direct procedures may be established for determining fatigue lives under either stress cycles or thermal cycles. Simulation results in the simplest cases of the proposed model are in good agreement with experimental data. (C) 2017 Elsevier Ltd. All rights reserved.

关键词： Metals Finite deformation Thermo-coupled effects New elastoplastic equations Fatigue failure Direct simulation

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Structural damage detection from a new damage index formed from displacement response 24th

Structural damage detection from a new damage index formed f...

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24th Australasian Conference on the Mechanics of Structures and Materials, ACMSM 2016

作者： Li, X.Y. Huang, Kai Department of Mechanics and Civil Engineering Key Laboratory of Disaster Forecast and Control in Engineering Jinan University Guangzhou China Department of Mechanics and Civil Engineering Jinan University Guangzhou China

ISBN: (纸本)9781138029934

An engineering approach to handle practical problems with condition evaluation/damage detection of structure with long-term monitored data is proposed basing on the distinct features of a new damage index, the Covariance of Displacement response function (CoD). The analytical formula of CoD is derived in this paper. The new CoD index is a function of the structural modal parameters. It is sensitive to local structural parameter change and is robust to noise, while it is less affected by the excitation location when implemented in the damage identification algorithm. A seven-storey frame structure is numerically studied to illustrate the features of the CoD index. The results show that the CoD parameter can identify damage occurrence and damage location. © 2017 Taylor & Francis Group, London.

关键词： Damage detection

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Publisher Correction: Abrupt emissions reductions during COVID-19 contributed to record summer rainfall in China

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Nature communications 2022年第1期13卷 1403页

作者： Yang Yang Lili Ren Mingxuan Wu Hailong Wang Fengfei Song L Ruby Leung Xin Hao Jiandong Li Lei Chen Huimin Li Liangying Zeng Yang Zhou Pinya Wang Hong Liao Jing Wang Zhen-Qiang Zhou Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control Jiangsu Collaborative Innovation Center of Atmospheric Environment and Equipment Technology School of Environmental Science and Engineering Nanjing University of Information Science and Technology Nanjing Jiangsu China. yang.yang@***. Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control Jiangsu Collaborative Innovation Center of Atmospheric Environment and Equipment Technology School of Environmental Science and Engineering Nanjing University of Information Science and Technology Nanjing Jiangsu China. Atmospheric Sciences and Global Change Division Pacific Northwest National Laboratory Richland WA USA. Atmospheric Sciences and Global Change Division Pacific Northwest National Laboratory Richland WA USA. hailong.wang@pnnl.gov. Frontier Science Centre for Deep Ocean Multispheres and Earth System and Physical Oceanography Laboratory Ocean University of China Qingdao China. Qingdao National Laboratory for Marine Science and Technology (QNLM) Qingdao China. Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters/Key Laboratory of Meteorological Disaster Ministry of Education Nanjing University for Information Science and Technology Nanjing Jiangsu China. Tianjin Key Laboratory for Oceanic Meteorology Tianjin Institute of Meteorological Science Tianjin China. Department of Atmospheric and Oceanic Sciences and Institute of Atmospheric Sciences Fudan University Shanghai China.

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Extended Finite Layer Method for Semi-space Ground Analysis

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GEOTECHNICAL AND GEOLOGICAL engineering 2017年第2期35卷 781-797页

作者： Tian, Guanfeng Tang, Liansheng Jinan Univ Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Guangdong Peoples R China Sun Yat Sen Univ Sch Earth Sci & Geol Engn Guangzhou 510275 Guangdong Peoples R China

The layered nature of natural soil must be considered in ground engineering. To this end, a ground finite layer method (FLM) based on extended patterns is proposed on the basis of the principles of traditional FLM. First, the displacement mode of the layer element uses the multiplication form of a quintic fully polynomial and double series. By superposing the calculated solutions of four symmetric loading patterns, the extended FLM can be used to analyze the mechanical state of ground under various types of loads. Second, the selection principles and methods for some important parameters of the extended FLM are established by analyzing and discussing the stress and displacement characteristics of ground loaded with vertical unit force. Finally, after a comparison with the solutions of classical analytical methods, such as the Boussinesq, Mindlin, and Cerruti formulae, the extended FLM is verified to be rational and accurate outside of the loading influence range. Thus, the proposed method will be easier to use in practice due to its adaptability to layered ground;however, its scope of influence and its mechanism near the loading position require further research.

关键词： Extended finite layer method Displacement mode Loading pattern Parameter selection principle Classical analytical method Loading influence range

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Numerical analysis and validation of spray distributions disturbed by quad- rotor drone wake at different flight speeds

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COMPUTERS AND ELECTRONICS IN AGRICULTURE 2019年 166卷 105036-000页

作者： Wen, Sheng Han, Jie Ning, Zhihua Lan, Yubin Yin, Xuanchun Zhang, Jiantao Ge, Yufeng South China Agr Univ Engn Fundamental Teaching & Training Ctr Guangzhou 510642 Guangdong Peoples R China Natl Joint Res Ctr Precis Agr Aviat Applicat Tech Guangzhou 510642 Guangdong Peoples R China South China Agr Univ Coll Engn Guangzhou 510642 Guangdong Peoples R China Jinan Univ Sch Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Guangdong Peoples R China Univ Nebraska Biol Syst Engn Lincoln NE USA

The computational fluid dynamics method based on the lattice Boltzmann method (LBM), was used to simulate the downwash flow field of a quad-rotor drone. The downwash flow fields of a quad-rotor drone at flight speeds of 1-7 m/s and flight altitudes of 1-2 m were simulated. The horseshoe-shaped vortices were successfully captured at a speed exceeding 5 m/s. In order to capture the deposition and drift distribution of droplets with different sizes in the downwash flow field of a quad-rotor drone more accurately, the Lagrangian discrete phase particle tracking method was used to simulate the trajectories of droplets with different particle sizes. By changing the flight speed, flight altitude, vertical height of the boom from the rotor, and lateral distance between the nozzles, the effects of these conditions on the droplet deposition and drift behind the fuselage were studied. The accuracy of the numerical simulation was verified by a wind tunnel test. The results of the numerical simulation were in good agreement with the data from the wind tunnel test. It is shown that the computational fluid dynamics model developed in the paper can be successfully applied to the simulations of droplet drift and deposition of a quad-rotor plant protection drone.

关键词： Quad-rotor plant protection drone Lattice Boltzmann method Large eddy simulation Droplet drift

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Dynamic response based damage detection for beam-like structures using deep learning 24th

Dynamic response based damage detection for beam-like struct...

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24th Australasian Conference on the Mechanics of Structures and Materials, ACMSM 2016

作者： Lin, Y.Z. Ma, H.W. Department of Mechanics and Civil Engineering Jinan University Key Laboratory of Disaster Forecast and Control in Engineering Ministry of Education Guangzhou China Department of Civil Engineering Qinghai University Xining China

ISBN: (纸本)9781138029934

Artificial Neural Network (ANN) method has attracted increasing attention in the structural damage detection field. However, its bottlenecks limit the applications in this area. In recent years, great advances in ANN called deep learning have changed the situation. This paper reports a novel application of deep learning for damage detection tasks of beam-like structure based on dynamic response. Numerical models of simple beam structure were analyzed to generate dynamic response. It was found that using a deeper neural network helped the recognition accuracy on the testing dataset contrasting a shallow network. In addition, dropout and ReLU technology play a vital role in preventing overfitting and GPU acceleration technology can provide the large computational demand of deep network. These results suggest that gaining benefits from more depth of a neural network is possible in structural damage detection problem. © 2017 Taylor & Francis Group, London.

关键词： Damage detection

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A direct approach toward simulating cyclic and non-cyclic fatigue failure of metals

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ACTA MECHANICA 2017年第12期228卷 4325-4339页

作者： Wang, Si-Yu Zhan, Lin Wang, Zhao-Ling Yin, Zheng-Nan Xiao, Heng Shanghai Univ Shanghai Inst Appl Math & Mech Yanchang Rd 149 Shanghai 200072 Peoples R China Jinan Univ Sch Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Guangdong Peoples R China

A new finite flow rate-dependent elastoplastic model is proposed toward directly simulating cyclic and non-cyclic fatigue failure behavior of metals. Novel results in four respects are presented: (1) the concept of yielding is rendered irrelevant with smooth transitions to both the plastic state and the rate-independent case;(2) asymptotic loss of the strength is incorporated as inherent constitutive feature;(3) the failure behavior may accordingly be derived as a direct consequence of the proposed model, without involving any additional failure criteria and any additional variables;and (4) direct and explicit procedures are established for identifying each rate-dependent parameter based on suitable test data. Numerical examples are provided for various uniaxial loading cases up to failure, including monotone and cyclic strain cases from low to high strain rates and cyclic loading cases as well as non-cyclic loading cases with either variable stress amplitudes or variable strain rates. Model predictions compare well with test data.

关键词： Strain rate

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Micro-modeling of thermal properties in carbon fibers reinforced polymer composites with fiber breaks or delamination

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COMPOSITES PART B-engineering 2017年 114卷 247-255页

作者： Ning, Zhihua Liu, Renhuai Elhajjar, Rani F. Wang, Fan Jinan Univ Sch Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Guangdong Peoples R China Univ Wisconsin Coll Engn & Appl Sci Dept Civil & Environm Engn 3200 North Cramer St Milwaukee WI 53211 USA

The thermal properties can be correlated to fiber breaks and delamination in unidirectional carbon fibers reinforced polymer (CFRP) composites by an analytical model developed in the present study. According to classical thermal laws, the thermal characteristics of the composite will change when the defects induce gaps or discontinuities in the composite. The thermal resistance with fiber breaks was obtained by cutting the contribution of a broken fiber on total resistance with the assumption of heat flow into the CFRP sample along the fiber longitudinal direction. Similarly, a delamination was treated as an air-filled defect which produces extra resistance to the original composite with the assumption of heat flow into the sample in the thickness direction. Analytical solutions were derived to predict the thermal resistance as a function of number of fiber breakage or delamination lateral size. The results show that the thermal resistance increases linearly with increasing the number of fiber breaks or delamination area. Thus thermal resistance can be a precise indicator of fiber breaks and delamination in CFRP composites. Fiber breaks degrade considerably the heat transfer ability of CFRP on longitudinal direction, while much less on the thickness direction. The effects of fiber volume fraction and ratio of fiber/matrix conductivity on thermal properties of the composite were discussed. The analytical solutions are in good agreement with the results from finite element analysis. The solution was also applied on the method of pulse thermography, and it was found that, the defect region, whether fiber breakage or delamination, will lead to changes in the temperature distribution on the rear surface of the composite. The thermal contrast is sensitivity to carbon fiber volume fraction. The present study proposed a simple way to correlate the thermal response to mechanical damages at the micro-scale in CFRP composites. (C) 2017 Elsevier Ltd. All rights reserved.

关键词： Micro-modeling Thermography Thermal properties Fiber breaks Delamination

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