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Mechanistic Understanding of the Corrosion Behaviors of AZ31 Finished by Wire Electric Discharge Machining

JOURNAL OF THE ELECTROCHEMICAL SOCIETY 2021年第7期168卷 071507-071507页

作者： Qiu, Youmin Chen, Lianxi Yang, Junjie Zeng, Dahai Liu, Hui Han, Jiaping Li, Qi Li, Jianwei Tu, Xiaohui Li, Wei Jinan Univ Inst Adv Wear & Corros Resistant & Funct Mat Guangzhou 510632 Peoples R China Foshan Univ Sch Mat Sci & Hydrogen Energy Foshan 528000 Peoples R China Jinan Univ MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China Songshan Lake Mat Lab Dongguan Guangdong Peoples R China Panzhihua Univ Dept Vanadium & Titanium Panzhihua 617000 Sichuan Peoples R China Harbin Inst Technol Sch Mechatron Engn Harbin 150001 Peoples R China Beijing Hangxing Machinery Manufacture Ltd Corp Beijing 100013 Peoples R China

Metallic contamination that occurs during machining is extremely hard to avoid, which may cause an irretrievable effect on the performance of materials. Unfortunately, this point is chronically neglected in practice. The present study focused on investigating the influence of wire electric discharge machining (WEDM), one of the most common techniques for magnesium implant manufacturing, on the morphology and corrosion behaviors of AZ31. The results show that the surface roughness increased after machining due to the presence of overlapped craters and scattered micro-cracks. Deposition of tool electrode materials was found throughout the recast layer in the form of Cu-rich particles (CuRPs), and increasing the energy input escalates this deposition process. The corrosion resistance of WEDM machined AZ31 was significantly deteriorated due to the galvanic coupling between CuRPs and Mg matrix. The corrosion mechanism of AZ31 alloy with CuRPs deposition was elucidated.

关键词： AZ31 magnesium alloy Wire electrical discharge machining (WEDM) Corrosion behaviors Cu impurity Mirco-galvanic corrosion

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A novel MOALO-based algorithm for structural damage detection 7

A novel MOALO-based algorithm for structural damage detectio...

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7th Asia-Pacific Workshop on Structural Health Monitoring, APWSHM 2018

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

ISBN: (纸本)9783000603594

Structural damage detection (SDD) is the first-type inverse problem in structural dynamics, and it is usually converted to a kind of constrained optimization problem in mathematics. Exploring a highly accurate and robust solution to the SDD problem is a challenging task in the field of structural health monitoring (SHM). In this study, a novel SDD method is proposed based on multi-objective ant lion optimizer (MOALO) algorithm, in which multi-objective functions are defined for the typical SDD inverse problem based on the model updating theory. The modal parameters, such as natural frequencies and mode shapes, are adopted into the objective functions whilst considering weighted coefficients corresponding to different modal parameters at the same time. The weighted strategy and sparse regularization are also taken into consideration for accurate SDD results with good robustness to noise. All illustrated results show that the proposed MOALO method is able to accurately locate and quantify damage of structures, which provides a potential SDD tool for real structures onsite. © APWSHM 2018. All rights reserved.

关键词： Inverse problems

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Nonlinear dynamic behavior of single-layer graphene under uniformly distributed loads

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COMPOSITES PART B-engineering 2019年 165卷 473-490页

作者： Yan, J. W. Lai, S. K. He, L. H. Jinan Univ Guangdong Higher Educ Inst Key Lab Prod Packaging & Logist Zhuhai Guangdong Peoples R China Jinan Univ MOE Key Lab Disaster Forecast & Control Engn Guangzhou Guangdong Peoples R China Hong Kong Polytech Univ Dept Civil & Environm Engn Hung Hom Kowloon Hong Kong Peoples R China Hong Kong Polytech Univ Shenzhen Res Inst Shenzhen Peoples R China Univ Sci & Technol China Dept Modern Mech CAS Key Lab Mech Behav & Design Mat Hefei Anhui Peoples R China

An atomistic-continuum multiscale approach is used to simulate the nonlinear dynamic behavior of simply supported single layer graphene sheets subject to a uniformly distributed out-of-plane load. The dynamic equation of motion is derived and solved by the Newmark-beta method. The evolution of surface morphology and the nonlinear effects in terms of geometrical and material nonlinearities can be captured by iteratively updating the system stiffness. It is found that the natural frequencies of simply-supported graphene sheets almost remain constant when the external load is in a small range. The present solutions are in good agreement with those results obtained from the linear vibration analysis by a semi-analytical method. As the applied load increases continuously, this gives rise to an elongation of graphene to increase the natural frequency. Based on the numerical approach, the surface morphology evolution of graphene can be visualized and explored.

关键词： Graphene Nonlinear dynamic behavior Atomistic-continuum multiscale approach Natural frequency Surface morphology evolution

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A Wideband Folded Reflectarray Antenna Based on Single-Layered Polarization Rotating Metasurface

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IEEE ACCESS 2020年 8卷 158579-158584页

作者： Su, Wei Luo, Wenhao Nie, Zhenhua Liu, Wen-Wen Cao, Zhen-Hua Wang, Zhi MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China China Elect Prod Reliabil & Environm Testing Reli Sci & Technol Reliabil Phys & Applicat Technol El Guangzhou 510610 Peoples R China Jinan Univ Sch Mech & Construct Engn Guangzhou 510632 Peoples R China Zhengzhou Univ Sch Mech & Safety Engn Zhengzhou 450001 Peoples R China

A wideband folded reflectarray antenna (FRA) based on single-layered polarization rotating metasurface (PRM) is proposed. The FRA is composed of a wideband polarization grid (PG), a wideband PRM and a wideband circular waveguide as the primary source. First, a wideband polarization rotating unit cell consisting of rhombus-shaped metal patch etched on dielectric substrate is designed, which can be used to rotate polarization of the reflective wave 90 degrees relative to that of the incident wave. The element and its mirror image can provide 0 degrees, 90 degrees, 180 degrees and 270 degrees phase shifts with 2-bit phase quantization and relatively higher polarization conversion rates in the Ku band. Due to the introduction of PG and PRM, the distance between the PG surface and the feed phase center can be reduced to about 1/2 of the distance between the imaginary feed and PRM reflectarray. Finally, a wideband FRA consisting of 315 elements with circular aperture is designed, fabricated and measured. The measured results indicate that the proposed antenna achieves 39.5% 3-dB gain bandwidth with 25.5 dBi peak gain at 15 GHz. Its maximum aperture efficiency is about 40%. Low-profile and wideband features of the FRA make it be a candidate in the wireless communication systems.

关键词： Feeds Reflector antennas Antenna arrays Wideband Substrates Metals Apertures Folded reflectarray polarization rotating reflection surface (PRRS) polarization grid

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Damping of Particle-Reinforced Composites Due to Interfacial Sliding

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Acta Mechanica Solida Sinica 2018年第5期31卷 623-634页

作者： Linghui He Renhuai Liu CAS Key Laboratory of Mechanical Behavior and Design of Materials University of Science and Technology of China Hefei 230026 China MOE Key Lab of Disaster and Control in Engineering Institute of Applied Mechanics Jinan University Guangzhou 510632 China

Mechanical damping of composites reinforced by randomly distributed particles due to interfacial sliding is analyzed. The matrix is elastically isotropic, and the particles are assumed rigid and of identical radii. An auxiliary problem is solved at first for the steady-state response of an infinite matrix containing a single inclusion to a harmonic external load. The result is then used to derive the explicit expression of the specific damping capability of the composite by using Mori-Tanaka＇s mean-field method. Numerical results are given and discussed in detail. It is concluded that the overall damping of the composite depends on several factors, including volume fraction of particles, Poisson＇s ratio of matrix and a dimensionless parameter that incorporates the combined effects of particle size, matrix stiffness, interracial viscosity and vibration frequency. The result is expected to be helpful in tailoring the damping performance of particle-reinforced composites.

关键词： Particle-reinforced composite Damping Interracial sliding

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Triple collision orbits in the free-fall three-body system without binary collisions

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CELESTIAL MECHANICS & DYNAMICAL ASTRONOMY 2021年第10期133卷 46-46页

作者： Li, Xiaoming Li, Xiaochen He, Linghui Liao, Shijun Jinan Univ Sch Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China South China Univ Technol Sch Civil Engn & Transportat Guangzhou 510641 Peoples R China Univ Sci & Technol China Dept Modern Mech Hefei 230026 Anhui Peoples R China Shanghai Jiao Tong Univ Ctr Adv Comp Sch Naval Architecture Ocean & Civil Engn Shanghai 200240 Peoples R China Shanghai Jiao Tong Univ Sch Phys & Astron Shanghai 200240 Peoples R China

We numerically investigate triple collision orbits of the free-fall three-body system which has no double collisions before three bodies collide. Triple collision is an important property of the three-body system. Tanikawa, Saito, Mikkola (Celest Mech Dyn Astron 131(6):24, 2019) obtained 11 triple collision orbits without double collision for the free-fall three-body problem. In this paper, we present 1658 triple collision orbits including the Lagrange's homothetic solution, 11 ones found by Tanikawa et al. (2019) and 1646 new triple collision orbits. The symbol sequences of these 1646 new triple collision orbits have digits that range between 1 and 120. With our high-precision results, numerical evidences of the asymptotic property of triple collision orbits are given.

关键词： Free-fall three-body problem Triple collision Symbol sequences

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Novel Dynamic Multiscale Model of Apparent Diffusion Permeability of Methane through Low-Permeability Coal Seams

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Energy & Fuels 2021年第9期35卷 7844-7857页

作者： Zhiqiang Li Jiansong Peng Lin Li Lingling Qi Wai Li MOE Engineering Center of Mine Disaster Prevention and Rescue Henan Polytechnic University Jiaozuo 454000 China Collaborative Innovation Center of Coal Work Safety and Clean High Efficiency Utilization Henan Polytechnic University Jiaozuo 454000 China Collaborative Innovation Center of Coalbed Methane and Shale Gas for Central Plains Economic Region (Henan Province) Henan Polytechnic University Jiaozuo 454000 China Henan Provincial Key Lab of Gas Geology and Control-Cultivation Base of Provincial and Ministry Joint State Key Henan Polytechnic University Jiaozuo 454000 China School of Engineering The University of Western Australia Crawley WA 6009 Australia

The low permeability of coal seams is a key factor restricting gas extraction. The multiscale pores in low-permeability coal make coal permeability present the multiscale characteristics. However, the conventional steady-state method cannot measure the multiscale permeability of low-permeability coal well. In this study, a unidirectional multiscale dynamic apparent diffusion model is proposed as an analytical model, and a multiscale dynamic apparent diffusion coefficient is defined. In addition, an experimental method for measuring low permeability from macroscale to microscale pores is provided. The experiments of gas desorption flow in the unidirectional, radial, and spherical directions were conducted to compare with each other. The research results show that (1) the apparent diffusion coefficient and apparent permeability decrease with time because of the multiscale pore structure in coal. (2) The multiscale dynamic apparent diffusion model can accurately describe the full-time process of the unidirectional gas desorption flow in coal. (3) The proposed model shows a broader applicability with a comparison to the current models.

关键词： Transport properties Coal Desorption Diffusion Permeability

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A sparse self-estimated sensor-network for reconstructing moving vehicle forces

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SMART MATERIALS AND STRUCTURES 2019年第8期28卷 085009-085009页

作者： Pan, Chudong Liu, Huanlin Yu, Ling Guangzhou Univ Sch Civil Engn Guangzhou Guangdong Peoples R China Jinan Univ Sch Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Guangdong Peoples R China

Reconstructing moving vehicle forces from structural responses is an important inverse problem in bridge engineering. When a sensor-network is applied to moving force identification (MFI), a necessary task is to specify the contribution of different sensors at the first beginning. This paper proposes a novel method based on the sparse self-estimated sensor-network for estimating moving vehicle forces on bridges. Firstly, an over-completed dictionary is pre-defined to ensure a sparse representation of moving vehicle forces. Images corresponding to force atoms, i.e. structural responses caused by unit force components, are used to match the structural responses. As a self-estimated sensor-network, the signal features, noise energy and signal-to-noise ratio of each sensor can be self-estimated by combining sparse regularization and Bayesian information criterion. Then an improved L-2-norm regularization model, in which the cost function is defined by the weighted residuals of sensors, is proposed and applied to solve the MFI problem. Finally, both numerical and experimental examples are conducted to assess the accuracy and the feasibility of the proposed method. Illustrated results clearly show the robustness and applicability of the proposed method. Some related issues are discussed as well.

关键词： moving force identification sparse regularization self-estimated sensor-network structural health monitoring inverse problems

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A novel narrow surface cage for full endoscopic oblique lateral lumbar interbody fusion: A finite element study

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JOURNAL OF ORTHOPAEDIC SCIENCE 2019年第6期24卷 991-998页

作者： Ling, Qinjie He, Erxing Zhang, Huanliang Lin, Hui Huang, Wenhua Southern Med Univ Sch Basic Med Sci Guangdong Prov Key Lab Med Biomech 1023 South Shatai Rd Guangzhou 510515 Guangdong Peoples R China Guangzhou Med Univ Affiliated Hosp 1 Dept Spinal Surg 151 Yanjiang West Rd Guangzhou 510120 Guangdong Peoples R China Jinan Univ Inst Appl Mech MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Guangdong Peoples R China Putian Univ Sch Mech & Elect Engn Putian Fujian Peoples R China

Objective: To evaluate the mechanical response of a narrow surface cage that we designed for full endoscopic oblique lateral lumbar interbody fusion (FE-OL-LIF). Methods: A finite element (FE) model of lumbar spine was developed and validated. To simulate the FE-OL-LIF, the functional spinal unit (FSU) L4-L5 was assembled with a narrow surface polyetheretherketone (PEEK) cage, two rods and four screws. 500N load combined with 7.5Nm moment was applied to the surgical models. Effect of the cage width on the stress was studied. Results: Range of motion (ROM) in the surgical models significantly decreased by 88% in flexion, 91% extension, 85% in right and left lateral bending, 75% in right and left axial rotation as compared to the intact model. Width of the cage slightly decreased the ROM in all loading scenarios. Flexion produced the highest stress in the cages and endplates. In all loading cases, the maximum stresses of cages and endplates were both lower than their yield stress. Conclusions: In engineering analysis, the novel narrow-surface cage had a strength to support spine activities. 9 mm width cage was recommended in FE-OL-LIF. This study provided engineering evidence and technical advice to improve the design of minimally invasive cage. Fatigue test and cadaver trial shall be improved. (c) 2019 The Japanese Orthopaedic Association. Published by Elsevier B.V. All rights reserved.

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Visualization Analysis of Markov Chain Based on CiteSpace 2019

Visualization Analysis of Markov Chain Based on CiteSpace

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Proceedings of the 2019 11th International Conference on Information Management and engineering

作者： Songping Yang Ranni Zhang Yongyi Chen Fan Yang He Wang Ru Zhang Packaging Engineering Institute Jinan University and MOE Key Laboratory of Disaster Forecast and Control in Engineering School of Mechanics and Construction Engineering Jinan University Zhuhai China School of Marxism Jinan University Zhuhai China School of Intelligent Science and Engineering Jinan University Zhuhai China Electrical Engineering Institute Jinan University Zhuhai China School of Electrical Engineering Jinan University Zhuhai China International Business School Jinan University Zhuhai China

ISBN: (纸本)9781450372343

Since markov chain is widely used in various fields, the relevant literatures of markov chain theories are analyzed base on CiteSpace in this paper, adopting 10,000 literatures in CNKI and 10,000 literatures in WOS as datas. The relationship among markov chain, monte carlo integral and bayesian theory is analyzed primarily. What's more, the hidden markov model, markov random field, markov decision process and grey-markov model derived from markov chain are investigated emphatically. Ultimately, we reviews the development history of markov chain, makes a visual analysis of the authors, sorts out the research status of markov chain, and makes a comprehensive review of the application of markov chain.

关键词： Citespace Monte Carlo Visualization

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