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14th International Conference on Fracture, ICF 2017

作者： Yuan, H. Han, J. MOE Key Laboratory of Disaster Forecast and Control in Engineering Institute of Applied Mechanics Jinan University Guangzhou510632 China

Pipe structure is a very important structural form for modern industry. The limitations of the overall system performance usually come from the capacity of pipe joints. Therefore, a cohesive interface modeling approach to debonding analysis of adhesively bonded pipe joints is presented in this paper. An analytical solution for the full-range behavior of an adhesively bonded pipe joint under combined thermal and mechanical loadings is obtained, assuming that the bond interface follows a bi-linear bond-slip model. The analytical solutions compared with finite element results can be used to explain the load-displacement relationship, stress transfer mechanism and the interface crack propagation. © 2017 Chinese Society of Theoretical and Applied Mechanics. All Rights Reserved.

关键词： Adhesives

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Identification of moving vehicle forces on bridge structures via moving average Tikhonov regularization

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SMART MATERIALS AND STRUCTURES 2017年第8期26卷

作者： Pan, Chu-Dong Yu, Ling Liu, Huan-Lin Jinan Univ Sch Mech & Construct Engn Guangzhou 510632 Guangdong Peoples R China Jinan Univ MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Guangdong Peoples R China

Traffic-induced moving force identification (MFI) is a typical inverse problem in the field of bridge structural health monitoring. Lots of regularization-based methods have been proposed for MFI. However, the MFI accuracy obtained from the existing methods is low when the moving forces enter into and exit a bridge deck due to low sensitivity of structural responses to the forces at these zones. To overcome this shortcoming, a novel moving average Tikhonov regularization method is proposed for MFI by combining with the moving average concepts. Firstly, the bridge-vehicle interaction moving force is assumed as a discrete finite signal with stable average value (DFS-SAV). Secondly, the reasonable signal feature of DFS-SAV is quantified and introduced for improving the penalty function (||x||(2)(2)) defined in the classical Tikhonov regularization. Then, a feasible two-step strategy is proposed for selecting regularization parameter and balance coefficient defined in the improved penalty function. Finally, both numerical simulations on a simply-supported beam and laboratory experiments on a hollow tube beam are performed for assessing the accuracy and the feasibility of the proposed method. The illustrated results show that the moving forces can be accurately identified with a strong robustness. Some related issues, such as selection of moving window length, effect of different penalty functions, and effect of different car speeds, are discussed as well.

关键词： moving force identification (MFI) regularization method moving average structural health monitoring (SHM)

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Application of sparsity in structural damage detection 8

Application of sparsity in structural damage detection

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8th International Conference on Structural Health Monitoring of Intelligent Infrastructure, SHMII 2017

作者： Chen, Z.P. Yu, L. School of Mechanics and Construction Engineering Jinan University Guangzhou510632 China MOE Key Lab of Disaster Forecast and Control in Engineering Jinan University Guangzhou510632 China

ISBN: (纸本)9781925553055

Structural damage detection (SDD) is one of the major subjects in the field of structural health monitoring (SHM) and various methodologies have been proposed and achieved great accuracy in such field. Inspired by the concept of sparsity, applications of sparsity in SDD are explored in this paper. First of all, an adaptive dictionary is proposed based on intrinsic mode function (IMF), which is utilized to reconstruct compressed acceleration excited by random load. The compressed accelerations are acquired under the application of compressive sensing (CS) technique. Then, as structural damages generally appear locally, SDD problem is characterized by sparsity. Sparse regularization technique is employed to solve SDD by defining two objective functions, to which different sparsity penalty items are introduced. Two iteration procedures inspired by Newton-Gauss algorithm are also presented to solve the problem. Simply-supported beam with different damage degrees are taken as numerical simulations example. The illustrated results show that the proposed method can give an accurate SDD and is robustness to noise. Some related issues are discussed as well. © 2017 International Society for Structural Health Monitoring of Intelligent Infrastrucure. All rights reserved.

关键词： Structural health monitoring

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Output-only structural damage detection based on hard-threshold method: Theoretical study 8

Output-only structural damage detection based on hard-thresh...

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8th International Conference on Structural Health Monitoring of Intelligent Infrastructure, SHMII 2017

作者： Pan, C.D. Yu, L. School of Mechanics and Construction Engineering Jinan University Guangzhou510632 China MOE Key Lab of Disaster Forecast and Control in Engineering Jinan University Guangzhou510632 China

ISBN: (纸本)9781925553055

Structural damage detection (SDD) with a vehicle-bridge system has been widely studied, since traffic excitations contribute to live load components in bridge design code. As an attempt work, this paper aims to propose an output-only SDD method based on hard-threshold strategy with unknown moving forces. Firstly, a transfer matrix is formulated between any two sensors for a healthy bridge structure. Singular value decomposition (SVD) technology is performed for the transfer matrix, and the corresponding singular vectors are used for decomposing two measured responses based on hard-threshold method. Then the decomposed results are used for estimating some singular values. Finally, a damage indicator (DI), which is defined for classifying status of structures, is calculated by comparing the differences between the estimated and true singular values. In order to assess the accuracy and feasibility of the proposed method, a simply-supported bridge subjected to one moving force is taken as an example for numerical simulations. The illustrated results show that the proposed method has a potential ability for solving the SDD problem. Some drawbacks of the proposed method are also discussed as well. © 2017 International Society for Structural Health Monitoring of Intelligent Infrastrucure. All rights reserved.

关键词： Singular value decomposition

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RIP-based subspace projection method for structural damage detection 8

RIP-based subspace projection method for structural damage d...

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8th International Conference on Structural Health Monitoring of Intelligent Infrastructure, SHMII 2017

作者： Luo, Z.W. Yu, L. School of Mechanics and Construction Engineering Jinan University Guangzhou510632 China MOE Key Lab of Disaster Forecast and Control in Engineering Jinan University Guangzhou510632 China

ISBN: (纸本)9781925553055

Structural damage detection (SDD) of large span structures needs to deal with a large number of data produced by thousands of sensors. SDD costs vast amounts of calculating time in a structural health monitoring (SHM) system. To overcome this problem, a new method of SDD is proposed in this paper. A measurement matrix satisfying restricted isometry property (RIP) is used to reduce the numbers of sensitivity equation. It projects the sensitivity matrix into the subspace. In the meantime, it also projects the differences of modal parameters between damaged and undamaged structure into this subspace and reduces the dimensions of differences of modal parameters. Then, the information in lower dimensions can be used for SDD. Finally, due to the sparsity of damage coefficients, sparse regularization method can be used to solve the sensitivity equation in subspace and improve the ill-posedness of SDD. In order to assess capabilities of the proposed method, a plane truss is taken as an example for numerical simulations. Different damage scenarios and the effects of measurement noises on the proposed method are considered. The illustrated results show that the proposed method can effectively detect damage location(s) and quantify damage degrees. © 2017 International Society for Structural Health Monitoring of Intelligent Infrastrucure. All rights reserved.

关键词： Matrix algebra

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A Model-Based Unloaded Test Method for Analysis of Braking Capacity of Elevator Brake

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ADVANCES IN MATERIALS SCIENCE AND engineering 2018年第1期2018卷 1-10页

作者： Peng, Qifeng Li, Zhongxing Yuan, Hong Huang, Guojian Li, Shanqing Sun, Xueli Jinan Univ Sch Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Guangdong Peoples R China Guangzhou Acad Special Equipment Inspect & Testin Guangzhou 510180 Guangdong Peoples R China

In order to improve the inspection efficiency and accuracy of the braking capacity of the elevator brake being used, a novel method for analyzing the full-loaded braking performance by using the unloaded braking performance is proposed, and a set of methods for measuring the braking torque is designed. Based on the analysis of the key factors that affect the mechanical performance of the elevator brake, the calculation model of the braking torque in the process of the emergency braking with the traction ratio of 2 : 1 is established, and the relationship between the braking torque and acceleration under different working conditions is analyzed. It is shown that, for the model assumed, the emergency braking torque is 1.56 times that of the static braking torque under 1.25 times the rated load. The braking torque increases linearly with the increase of braking acceleration. An elevator model being used is tested and calculated. The experimental results show that the braking acceleration measured by the experiment is 11.95% less than the theoretical value. And the analysis shows that, comparing with the traditional test method, the braking torque test method designed in this paper is more accurate and safe.

关键词： BRAKES ELEVATORS ACCURACY TRACTION (engineering) ACCELERATION (Mechanics)

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Simultaneous identification of moving forces and structural damages by L1/2 regularization method 24th

Simultaneous identification of moving forces and structural ...

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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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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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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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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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