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Study on in situ stress testing method based on Kaiser effect of acoustic emission and comsol simulation

Frontiers of Earth Science 2023年第3期17卷 818-831页

作者： Chenyu WANG Dongming ZHANG Shujian LI Yu CHEN Chongyang WANG Kangde REN State Key Laboratory of Coal Mine Disaster Dynamics and Control Chongqing UniversityChongqing 400044China School of Resources and Safety Engineering Chongqing UniversityChongqing 400044China Yunnan Phosphate Chemical Group Co. Ltd.Kunming 650600China National Engineering and Technology Research Center for Development and Utilization of Phosphate Resources Kunming 650600China

In situ stress testing can improve the safety and efficiency of coal mining.Identifying the Kaiser effect point is vital for in situ stress calculations;however,the in situ stress calculation is limited by the rock sampling angle.Here,the Kaiser effect point identification theory is established and applied to the Xuyong Coal Mine.Uniaxial compression and acoustic emission experiments were carried out on sandstone with 6 sampling directions.Furthermore,comsol simulation is applied to study the in situ stress distribution in the coal mine to verify the calculation accuracy.The results are as follows.1)The failure mode of non-bedded and vertical-bedded rocks is primarily tensile shear failure with obvious brittleness in mechanical and acoustic emission characteristics.Shear slip along the bedding plane is the primary failure mode of inclined-bedded rock.Additional take-off points exist in the AE count curve.2)The Kaiser point identification method based on the variation of AE count curve parametersΔti andτi can effectively calculate the in situ stress.According to the numerical value of Kaiser point and sampling direction,the in situ stress of the conveyor roadway in the Xuyong Coal Mine was calculated asσ1=22.81 MPa,σ2=10.87 MPa andσ3=6.14 MPa.3)By the comsol simulation study,it was found that a stress concentration zone of 16.13 MPa exists near the two sides roadway.Compared with the Kaiser effect method,the deviation rates of the three-direction principal stress calculated by comsol were all less than 5%.This verifies that the in situ stress calculation by Kaiser effect in this study can be applied to the Xuyong Coal Mine.

关键词： Coal Mine uniaxial compression acoustic emission comsol simulation

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Heat transfer and temperature evolution in underground mininginduced overburden fracture and ground fissures: Optimal time window of UAV infrared monitoring

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International Journal of Mining Science and Technology 2024年第1期34卷 31-50页

作者： Yixin Zhao Kangning Zhang Bo Sun Chunwei Ling Jihong Guo Beijing Key Laboratory for Precise Mining of Intergrown Energy and Resources China University of Mining and Technology-BeijingBeijing 100083China School of Energy&Mining Engineering China University of Mining and Technology-BeijingBeijing 100083China State Key Laboratory of Coal Resources and Safe Mining China University of Mining and Technology-BeijingBeijing 100083China

Heat transfer and temperature evolution in overburden fracture and ground fissures are one of the essential topics for the identification of ground fissures via unmanned aerial vehicle(UAV) infrared imager. In this study, discrete element software UDEC was employed to investigate the overburden fracture field under different mining conditions. Multiphysics software comsol were employed to investigate heat transfer and temperature evolution of overburden fracture and ground fissures under the influence of mining condition, fissure depth, fissure width, and month alternation. The UAV infrared field measurements also provided a calibration for numerical simulation. The results showed that for ground fissures connected to underground goaf(Fissure Ⅰ), the temperature difference increased with larger mining height and shallow buried depth. In addition, Fissure Ⅰ located in the boundary of the goaf have a greater temperature difference and is easier to be identified than fissures located above the mining goaf. For ground fissures having no connection to underground goaf(Fissure Ⅱ), the heat transfer is affected by the internal resistance of the overlying strata fracture when the depth of Fissure Ⅱ is greater than10 m, the temperature of Fissure Ⅱ gradually equals to the ground temperature as the fissures’ depth increases, and the fissures are difficult to be identified. The identification effect is most obvious for fissures larger than 16 cm under the same depth. In spring and summer, UAV infrared identification of mining fissures should be carried out during nighttime. This study provides the basis for the optimal time and season for the UAV infrared identification of different types of mining ground fissures.

关键词： Heat transfer Overburden fracture Ground fissures Infrared thermal imaging Unmanned aerial vehicle(UAV) comsol simulation

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A new approach for accurate determination of particle sizes in microfluidic impedance cytometry

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Nanotechnology and Precision Engineering 2022年第4期5卷 8-17页

作者： N.Priyadarshi Usama Ahmed Abbasi V.Kumaran P.Chowdhury Department of Chemical Engineering Indian Institute of ScienceBangalore 560012India Pratimesh Laboratory Indian Institute of ScienceBangalore 560012India Nanomaterials Research Laboratory Surface Engineering DivisionCSIR–National Aerospace LaboratoriesBangalore 560017India

In microfluidic impedance cytometry,the change in impedance is recorded as an individual cell passes through a channel between electrodes deposited on its walls,and the particle size is inferred from the amplitude of the impedance signal using calibration.However,because the current density is nonuniform between electrodes of finite width,there could be an error in the particle size measurement because of uncertainty about the location of the particle in the channel cross section.Here,a correlation is developed relating the particle size to the signal amplitude and the velocity of the particle through the channel.The latter is inferred from the time interval between the two extrema in the impedance curve as the particle passes through a channel with cross-sectional dimensions of 50μm(width)×30μm(height)with two pairs of parallel facing electrodes.The change in impedance is predicted using 3D comsol finite-element simulations,and a theoretical correlation that is independent of particle size is formulated to correct the particle diameter for variations in the cross-sectional location.With this correlation,the standard deviation in the experimental data is reduced by a factor of two to close to the standard deviation reported in the manufacturer specifications.

关键词： Impedance cytometry Lab on chip comsol simulation

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Corrosion Behavior of Pipeline Steel in Oilfield Produced Water under Dynamic Corrosion System

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Journal of Wuhan University of Technology(Materials Science) 2022年第4期37卷 677-691页

作者：赵杰 LIU Yida 杨晓宇 HE Xin WANG Lei XIONG Dan GU Yanhong School of Mechanical Engineering Beijing Institute of Petrochemical TechnologyBeijing 102617China School of Safety Engineering Beijing Institute of Petrochemical TechnologyBeijing 102617China

In order to predict the corrosion trendency of X100 pipeline steel in flowing oilfield produced water,the effect of flow rate on the corrosion behavior of X100 pipeline steel was studied under general dynamic condition and simulated real working condition at the flow rate of 0.2,0.4,and 0.6 m·s^(-1).Potentiodynamic polarization curves and electrochemical impedance spectroscopy were used to study the corrosion behavior of X100 steel.Energy dispersive spectroscopy,X-ray diffraction and scanning electron microscopy were used to analyze corrosion product composition and micromorphology.The experimental results show that the corrosion is more serious under simulated real working conditions than that under the general dynamic conditions.In any case the corrosion current density increases with the increase of the flow rate,and the total impedance value decreases.The corrosion products include Fe_(3)O_(4),Fe_(2)O_(3),and FeOOH.The mass transfer and electrochemistry were simulated by flow coupled in comsol software.The multiphysical field coupling simulation results are closer to the engineering practice than the single flow field simulation,and similar results from the experiments were obtained.Both experimental and simulation results reveal that the higher flow rate is,the more serious corrosion appear and the more corrosion products accumulate.By combining experimental and comsol simulation data,the corrosion process model of X100 steel was proposed.

关键词： X100 steel flow rate oilfield produced water corrosion behavior comsol simulation

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An investigation on improving the homogeneity of plasma generated by linear microwave plasma source with a length of 1550 mm

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Plasma Science and Technology 2021年第2期23卷 7-16页

作者：周继承徐伟陈特超 School of Energy Science and Engineering Central South UniversityChangsha 410083People's Republic of China Hunan Red Solar Photoelectricity Science and Technology Co. LtdChangsha 410083People's Republic of China

To develop a larger in-line plasma enhanced chemical vapor deposition(PECVD)device,the length of the linear microwave plasma source needs to be increased to 1550 mm.This paper proposes a solution to the problem of plasma inhomogeneity caused by increasing device length.Based on the comsol Multiphysics,a multi-physics field coupling model for in-line PECVD device is developed and validated.The effects of microwave power,chamber pressure,and magnetic flux density on the plasma distribution are investigated,respectively,and their corresponding optimized values are obtained.This paper also presents a new strategy to optimize the wafer position to achieve the balance between deposition rate and film quality.Numerical results have indicated that increasing microwave power and magnetic flux density or decreasing chamber pressure all play positive roles in improving plasma homogeneity,and among them,the microwave power is the most decisive influencing factor.It is found that the plasma homogeneity is optimal under the condition of microwave power at 2000 W,chamber pressure at 15 Pa,and magnetic field strength at 45 mT.The relative deviation is within−3.7%to 3.9%,which fully satisfies the process requirements of the equipment.The best position for the wafer is 88 mm from the copper antenna.The results are very valuable for improving the quality of the in-line PECVD device.

关键词： in-line PECVD linear microwave plasma source multi-physics field comsol simulation homogeneity

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Finite element analysis on factors influencing the clamping force in an electrostatic chuck

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Journal of Semiconductors 2014年第9期35卷 87-91页

作者：王兴阔程嘉王珂晟杨义勇孙钰淳曹明路季林红 School of Engineering and Technology China University of Geosciences (Beijing) Department of Mechanical Engineering Tsinghua University Department of Mechanical Engineering Academy of Armored Force Engineering of PLA

As one of the core components of IC manufacturing equipment, the electrostatic chuck （ESC） has been widely applied in semiconductor processing such as etching, PVD and CVD. The clamping force of the ESC is one of the most important technical indicators. A multi-physics simulation software comsol is used to analyze the factors influencing the clamping force. The curves between the clamping force and the main parameters such as DC voltage, electrode thickness, electrode radius, dielectric thickness and helium gap are obtained. Moreover, the effects of these factors on the clamping force are investigated by means oforthogonal experiments. The results show that the factors can be ranked in order of voltage, electrode radius, helium gap and dielectric thickness according to their importance, which may offer certain reference for the design of ESCs.

关键词： electrostatic chuck clamping force comsol simulation orthogonal experiment

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