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Mechanism and control of spalling for friable sandstone pillars in a room and pillar mine

Journal of engineering Science and Technology Review 2018年第6期11卷 197-205页

作者： Ziwei, Ding Jindui, Jia Amirhossein, Bagherieh Ji, Li Yue, Song School of Energy Xi'an University of Science and Technology Xi'an710054 China Anhui Province Key Lab. of Mining Response and Disaster Prevention Control in Deep Coal Mine Anhui University of Science and Technology Huainan232001 China Department of Mineral engineering New Mexico Institute of Mining and Technology SocorroNM87801 United States

The ability to efficiently control sandstone pillar spalling is extremely important in ensuring the safety and highefficiency production of sandstone mines. The increase in size is usually suggested as a remedy for pillar spalling, but none of the suggested remedies reflect the influences of geotechnical properties of rock mass on stability control. Some sandstone mining practices have proven that increasing the size of pillars cannot effectively control pillar spalling. The relationship between the strength of St. Peter sandstone pillar and pillar loads was theoretically analyzed in the current study, in order to examine the influences of geotechnical parameters of sandstone on the stability of pillars and control pillar spalling. The key geotechnical parameters that influence the stability of sandstone pillars were also examined. Subsequently, the pillar instability mechanism and influences of geotechnical parameters on pillar stability were investigated by Finite Difference Method. Finally, a ground control method using shotcrete on pillar was proposed for increasing the stability of pillars. Results demonstrate that compressive stress on the St. Peter sandstone pillar is considerably larger than the compressive strength after mining, resulting in the evident deformation of most regions. The relation curves of displacement at the pillar top with internal friction angle and cohesion are in the power functional distributions, but the change of cohesion is more significant in the pillar strength. The displacement at the pillar top gradually decreases with the increase in internal friction angle, whereas the plastic failure regions of pillars gradually decrease from the bottom to the upper parts with the increase in cohesion. A field industrial test proves that shotcrete on pillars can increase pillar strength, which effectively controls the pillar spalling. Research results provide theoretical and practical guidelines to enhance the stability of pillars under the sa

关键词： Rock mechanics

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Thermal-Structural Coupling Analysis of PCBA System 3

Thermal-Structural Coupling Analysis of PCBA System

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2018 3rd International Conference on Insulating Materials, Material Application and Electrical engineering, IMMAEE 2018

作者： Su, Wei Zhu, Junhua Liu, Renhuai He, Zhiyuan Scienceand Technol. on Reliability Phys. and Applic. Technology of Electronic Component Laboratory China Electronic Product Reliability and Environmental Testing Research Institute Guangzhou China Department of Mechanics and Civil Engineering Jinan University Guangzhou China MOE Key Lab of Disaster Forecast and Control in Engineering Jinan University Guangzhou China

In this paper, the thermal and structural analysis of the PCBA system is provided by using the 3-D ANSYS package. The results of thermal and structural analysis for complex and simple model are compared. The paper also describes the deformation analysis of the PCBA system components, and the weak components sensitive to thermal stress are determined though thermal-structual analysis. The results of thermal analysis are helpful to the optimizing overall arrangement design of PCBA system. © Published under licence by IOP Publishing Ltd.

关键词： Thermoanalysis

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Explicit and accurate characterization of hardening- softening behavior of metals up to failure

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IOP Conference Series: Materials Science and engineering 2020年第1期770卷

作者： Z H Xu S Y Wang L Zhan H F Xi H Xiao School of Mechanics & Construction Engineering and MOE Lab for Disaster Forecast & Control in Engineering Jinan University West Huangpu Avenue 601 510632 Guangzhou PR China State Key Laboratory for Strength and Vibration of Mechanical Structures Xi'an Jiaotong University 710049 Xi'an PR China

Full and accurate characterization of metal hardening-softening effects till failure is carried out with a new explicit approach. To this purpose, a new expression for the plastic work is presented explicitly in terms of the uniaxial stress-strain function of any given form. Accordingly, the yield strength as function of the plastic work can be determined jointly from the above functions with the axial logarithmic strain as parametric variable. Using the proposed approach, any test data obtained within the entire stress-strain range with hardening and softening portions up to failure can be fitted by directly treating a suitable form of the uniaxial stress-strain function. This allows one to bypass usual tedious trial-and-error numerical procedures in dealing with nonlinear elastoplastic rate equations for identifying numerous unknown parameters. Accurate simulation results are shown with numerical examples.

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Ultimate Strength Analysis of Three-Way Pipe Considering Plastic Reinforcement Effect

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Journal of Physics: Conference Series 2020年第2期1650卷

作者： Wei Su Wenhao Luo Xianshan Dong Renhuai Liu MOE Key lab of Disaster Forecast and Control in Engineering Guangzhou 510632 China. Science and Technology on Reliability Physics and Application Technology of Electronic Component Laboratory China Electronic Product Reliability and Environmental Testing Research Institute Guangzhou 510610 China. School of Mechanics and Construction Engineering Jinan University Guangzhou 510632 China

Considering the plastic reinforcement effect in materials, the plastic limit load of the three-way structure is analyzed. ANSYS commercial finite element software is used for numerical simulation. According to the results, the paper discusses the influence of the plastic reinforcement effect on the pipe's plastic ultimate load and failure mode. And the structure is further analyzed to verify the theory and design ideas in actual engineering. For improving the design and safety assessment of the three-way structure, the results provide a theoretical basis and a numerical reference, and the finite element method is economical than the experimental method. At last, it satisfies the accuracy requirements of engineering.

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Ultimate Strength Analysis of Local Thinning Tee Pipe Considering Plastic Strengthening Effect

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Journal of Physics: Conference Series 2020年第2期1650卷

In this paper, the locally thinned three-way structure under internal pressure is analyzed based on the theory of plastic strengthening effect and limit analysis. A finite element model is presented through ANSYS commercial software to simulate the mechanical properties of orthogonal and oblique three-way structures. This paper systematically analyses how the shape and size of the thinning effect the plastic limit load of the pipe and what is the typical failure mode of plastic failure. Some valuable conclusions are drawn, which provide a useful reference for the design and production of the tee pipe.

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Wave Soldering Structure Optimization Simulation of Multi-layer Ceramic Capacitors

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Journal of Physics: Conference Series 2020年第3期1650卷

作者： Wei Su Wenhao Luo Junkui Li Renhuai Liu MOE Key lab of Disaster Forecast and Control in Engineering Guangzhou 510632 China. Science and Technology on Reliability Physics and Application Technology of Electronic Component Laboratory China Electronic Product Reliability and Environmental Testing Research Institute Guangzhou 510610 China. School of Mechanics and Construction Engineering Jinan University Guangzhou 510632 China

In this paper, the thermal analysis and structural analysis of MLCC are carried out by using the commercial finite element software ANSYS. By comparing the thermal-mechanical analysis results of the structural optimization models of different schemes, the optimal optimization scheme is found. The model calculated the time required for MLCC to reach temperature stability considering thermal convection and heat conduction, and obtained the thermal deformation and thermal stress distribution of MLCC element. Based on the analysis results of MLCC original model, the thermal analysis under different wave soldering temperatures was carried out. Based on the simulated transient results, the structure and materials of MLCC key components were optimized. The results provide a basis for the optimal design of MLCC.

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An improved nelder-mead algorithm for optimization problem on structural damage detection 24th

An improved nelder-mead algorithm for optimization problem o...

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

作者： Chen, Zepeng Yu, Ling Department of Mechanics and Civil Engineering Jinan University Guangzhou China MOE Key Lab of Disaster Forecast and Control in Engineering Jinan University Guangzhou China

ISBN: (纸本)9781138029934

Structural Damage Detection (SDD) is one of fundamental objectives in the field of structural health monitoring. Usually, the SDD problem can be transformed into an optimal problem by introducing objective functions mathematically. Many methodologies have been developed and achieved great success in the last few decades. However, their calculation efficiency and accuracy are still required to be improved. In this study, an Improved Nelder-Mead (INM) simplex algorithm is proposed for the SDD optimal problem by embedding the Nelder-Mead process into Particle Swarm Optimization (PSO) algorithm. The hybrid algorithm is named PSO-INM. In order to get better results, two filter strategies are proposed based on fitness values and index stability factor. Numerical simulations of a thin-walled hollow simply-supported beam are conducted to assess effectiveness of both PSO-INM and two proposed strategies. The results show that the PSO-INM algorithm and strategies proposed herein are able to locate structural damages as well as to quantify extents of damages with a good noise immunity. Some related issues are discussed as well. © 2017 Taylor & Francis Group, London.

关键词： Structural health monitoring

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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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