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Layout and support technology of entry for pillar face

International Journal of Mining science and technology 2016年第5期26卷 877-884页

作者： Wang Jianli xu Ying Li Wenfeng Wang Xiangyu Bai Jianbiao school of Mines China University of Mining & Technology Shanxi Huishen Coal Industry Development Co. Ltd. Department of Petroleum and Geological engineering The University of Oklahoma

In order to improve the recovery rate of coal, some mines have begun to recover the residual protective pillars in the form of short wall faces. However, it is difficult to control stability of the haulage entry and the ventilating entry under the mining influences of the pillar face and the two side faces. Thus the 4311 face, which was designed to recover the 57 m wide residual protective pillar in Guojiashan Coal Mine,was taken as engineering background. Distribution law of stress and plastic zone in the residual protective pillar was analyzed using the numerical simulation. Then the gob-side entry driving technology was proposed to layout the entries for the pillar face. Based on the analysis of stress distribution and deformation characteristics of surrounding rocks in gob-side entry driving with different width of narrow pillars, the width of the narrow pillar of the entries in the 4311 face was decided to be 4 m. In order to control stability of the gob-side entry driving, the {2. model of the main roof was established and deformation characteristic of surrounding rock was analyzed. Then the bolt support technology with high strength and high pre-tightening force was proposed for entry support. Especially, the hydraulic expansion bolts were used to support the narrow pillar rib. The engineering results show that the width of the narrow pillar is reasonable and the entry support technology is effective. The research achievement can provide some references to pillar recovery for other coal mines.

关键词： Pillar recovery Gob-side entry driving Stability Bolt support Hydraulic expansion bolt

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Effect of cold working and annealing on microstructure and properties of powder metallurgy high entropy alloy

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science china(Technological sciences) 2018年第2期61卷 197-203页

作者： LIU Bin xu LiYou LIU Yong WANG JingShi WANG JiaWen FANG QiHong State Key Lab of Powder Metallurgy Central South UniversityChangsha 410083China College of mechanical and Vehicle engineering Hunan UniversityChangsha 410082China

An equiatomic CoCrFeNiMn high entropy alloy （HEA） was produced by powder metallurgy method. Cold rolling followed by subsequent annealing was conducted to further optimize the microstructure and mechanical properties. The results show that the SPSed CoCrFeNiMn HEA has an equiaxed single fcc phase microstructrue. Cold rolling results in extensive dislocation pile-up and twinning within the grains. The 80% cold-rolled alloy shows very high yield strength of 12.2.MPa, but a limited elongation of 3%. Subsequent annealing produces recrystallization and precipitation of fine a particles with particle size of 30-100 nm. The annealed alloy has a yield strength of 540 MPa, which is about two to three times of the cast CoCrFeNiMn HEA, while still maintains a high tensile ductility of 41%. The improvement of the tensile properties is caused by the grain boundary strengthening, solid solution strengthening, and precipitation strengthening.

关键词： powder metallurgy high entropy alloy annealing cold rolling mechanical properties

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Cr元素对桥梁耐候钢相变行为的影响

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燕山大学学报 2018年第2期42卷 119-124页

作者：高新亮肖瑶韩毅徐东张兴中燕山大学国家冷轧板带装备及工艺工程技术研究中心河北秦皇岛066004 燕山大学机械工程学院河北秦皇岛066004 河北工程大学材料科学与工程学院河北邯郸056038

桥梁耐候钢可在大气环境中裸露使用,其符合资源节约与环境友好型社会发展对桥梁建设提出的新要求。本文为研究不同冷却速度下桥梁耐候钢的相变过程和组织演变情况以及Cr元素对其相变规律的影响,利用热膨胀法并结合金相建立两种不同成分... 详细信息

桥梁耐候钢可在大气环境中裸露使用,其符合资源节约与环境友好型社会发展对桥梁建设提出的新要求。本文为研究不同冷却速度下桥梁耐候钢的相变过程和组织演变情况以及Cr元素对其相变规律的影响,利用热膨胀法并结合金相建立两种不同成分桥梁耐候钢的动态CCT曲线。结果表明:Cr元素降低铁素体和贝氏体相变温度,扩大贝氏体相变区域,减小铁素体晶粒尺寸和体积分数。冷却速度由0.5℃/s增加到2.℃/s,桥梁耐候钢的显微组织由铁素体和珠光体向贝氏体转变,铁素体相变开始温度和贝氏体相变终止温度降低。

关键词：桥梁耐候钢相变微观组织热膨胀法

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mechanical properties of WC–Co coatings with different decarburization levels

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Rare Metals 2014年第3期33卷 313-317页

作者： xu Wu Zhi-Meng Guo Hai-Bin Wang Xiao-Yan Song school of Materials science and {2. University of Science and Technology Bejing College of Materials science and engineering Beijing University of Technology

In this study, two kinds of WC-Co coatings with different decarburization levels were deposited by high-velocity oxy-fuel（HVOF） spraying using the ultrafine WC-Co composite powder and commercial micronsized powder, respectively. The hardness and elastic modulus were measured on the top surface and cross sections of the prepared coatings by the nanoindentation method. The results show that the ultrafine-structured coating has much higher density and inhibited decarburization than the conventional coating, which thus results in higher hardness and elastic modulus values than the micronsized coating. The wear resistance of thermal-sprayed cermet coatings greatly depends on the cross-sectional hardness and elastic modulus which reflects the bond strength between splats to some extent. Based on the analysis, a better understanding of the microstructure and properties in cermet coating materials was obtained.

关键词： Composite powder Cermet coating Decarburization Nanoindentation Wear resistance

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Recent Advances in Hole Making of FRP/Metal Stacks:A Review

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Transactions of Nanjing university of Aeronautics and Astronautics 2019年第3期36卷 361-375页

作者： CHEN Yan YANG Haojun xu Jiuhua FU Yucan YAN Chaoren Jiangsu Key Laboratory of Precision and Micro-manufacturing technology College of Mechanical and Electrical EngineeringNanjing University of Aeronautics and Astronautics

Weight reduction is a key driving force for materials development in aerospace industry,which leads to extensive usage of lightweight structural materials such as fiber reinforced polymer(FRP),titanium alloy,aluminum alloy,*** making is indispensable to assembling these lightweight components by riveted or bolted ***,hole making of FRP / metal stacks is always the most challenging task due to differences of material properties between FRP and metals.A comprehensive literature review on hole making of FRP/metal stacks in the last decade is given with a focus on four main aspects including drilling operation,drilling damages and machining parameter optimization,tool performance and wear,and developments in hole making ***,in order to ensure the precise and efficient hole making of FRP/metal stacks,an idea of low frequency vibration assisted drilling(LFVAD)FRP/metal stacks based on material removal characteristics is put forward by fully exploiting the unique advantages of LFVAD technology.

关键词： fiber reinforced polymer (FRP)/metal stacks drilling machining quality tool wear helical milling vibration assisted drilling abrasive water jet machining

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Fabrication of commercial pure Ti by selective laser melting using hydride-dehydride titanium powders treated by ball milling

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Journal of Materials science & technology 2019年第2期35卷 322-327页

作者： Wei xu Shiqi Xiao Xin Lu Gang Chen Chengcheng Liu xuanhui Qu beijing Advanced Innovation Center for Materials Genome engineering Institute for Advanced Materials and Technology University of Science and Technology Beijing beijing Key Laboratory for Advanced Powder Metallurgy and Particulate Materials beijing Laboratory of Metallic Materials and Processing for Modern Transportation

Micro-fine sphericalpowders are recommended for selective laser melting(SLM). However, they are mostly expensive due to the complex manufacturing technique and low yield. In this paper, using lowcost treated hydride-dehydride(HDH) Ti powders, commercial pure Ti(CP-Ti) was successfully fabricated by SLM. After 4-h milling, the resulting powders become near-spherical with no obvious angularity, and have optimal flowability with the apparent density of 1.64 ± 0.02.g/cm^3, tap density of 2.10 ± 0.04 g/cm^3,angle of repose 40.11?±0.09?, and Carr's index of 77.74 ± 0.15. The microstructure was determined with full acicular martensitic β phase. The CP-Ti can achieve superior mechanical properties with the ultimate tensile strength of 876.1 ± 2..5 MPa and elongation of(14.7 ± 0.5)%, which exhibit distinctly competitive compared to the as-cast CP-Ti or Ti-6 Al-4 V. Excellent mechanical properties together with its low-cost make SLM-fabricated CP-Ti from modified HDH Ti powders show promising applications.

关键词： Selective laser melting Hydride-dehydride powders Titanium Microstructure mechanical properties

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Energy dissipation of coal and rock during damage and failure process based on EMR

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International Journal of Mining science and technology 2015年第5期25卷 787-795页

作者： Song Dazhao Wang Enyuan Li Zhonghui Liu Jie xu Wenquan school of Safety engineering China University of Mining & Technology Postdoctoral Research Station Yongcheng Coal & Electricity Holding Group Co.Ltd. State Key Laboratory of Coal Resources & Safe Mining Shaanxi Coal and Chemical technology Institute Co. Ltd.

The physical and mechanical change processes of coal and rock are closely related to energy transformation,and the destruction and failure of coal and rock is an instability phenomena driven by energy ***,the energy change of large-scale coal rock in the mine site is hardly calculated accurately,making it difficult to monitor coal-rock systematic failure and collapse from the perspective of *** the energy dissipation EMR monitoring system,we studied the damage and failure of coal and rock with bursting liability from the energy dissipation point using the geophysical method-EMR,and explored the energy dissipation characteristics during uniaxial compression and their main influencing *** results show that under displacement-control loading mode,there are 2.types of energy dissipation trends for both coal and rock with bursting *** type Ⅰ trend is a steady increase one during the whole process,therein,the energy dissipation of rock samples is accelerated at the peak *** type Ⅱ trend energy is a W-shaped fluctuating one containing 6 *** load-control loading mode,there is one energy dissipation trend of shock downward-steady *** that,rock samples also present a trend of 4 *** energy dissipation characteristics of coal and rockduring loading failure process can be used as effective criteria to assess whether they are in a stable or destructive *** factors influencing energy dissipation in the loading failure process of coal and rock mainly include strength,homogeneity,and energy input efficiency.

关键词： Energy dissipation Electromagnetic radiation Coal and rock Damage and failure Rock burst

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Grinding behavior and surface appearance of(TiC_p+ TiB_w)/Ti-6Al-4V titanium matrix composites

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Chinese Journal of Aeronautics 2014年第5期27卷 1334-1342页

作者： Ding Wenfeng Zhao Biao xu Jiuhua Yang Changyong Fu Yucan Su Honghua College of mechanical and Electrical engineering Nanjing University of Aeronautics and Astronautics Jiangsu Key Laboratory of Precision and Micro-Manufacturing technology

（TiCp＋ TiBw）/Ti-6Al-4V titanium matrix composites（PTMCs） have broad application prospects in the aviation and nuclear field. However, it is a typical difficult-to-cut material due to high hardness of the reinforcements, high strength and low thermal conductivity of Ti-6Al-4V alloy matrix. Grinding experiments with vitrified CBN wheels were conducted to analyze comparatively the grinding performance of PTMCs and Ti-6Al-4V alloy. Grinding force and force ratios, specific grinding energy, grinding temperature, surface roughness, ground surface appearance were discussed. The results show that the normal grinding force and the force ratios of PTMCs are much larger than that of Ti-6Al-4V alloy. Low depth of cut and high workpiece speed are generally beneficial to achieve the precision ground surface for PTMCs. The hard reinforcements of PTMCs are mainly removed in the ductile mode during grinding. However, the removal phenomenon of the reinforcements due to brittle fracture still exists, which contributes to the lower specific grinding energy and grinding temperature of PTMCs than Ti-6Al-4V alloy.

关键词： Grinding force Grinding temperature Particles Surface appearance Titanium matrix composites

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精心组织教学全面提高质量

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上海理工大学学报（社会科学版） 2001年第3期23卷 63-65页

作者：宁原林上海理工大学机械工程学院上海200093

机械零件是工科院校中一门综合性比较强的重要的专业基础课,学生往往感到机械零件这门课不太好学,不易得法。本文从讲好课、上好习题课、重视实践环节及加强教学研究等几个方面探讨如何提高机械零件课程的教学效果。

关键词：机械零件教学方法教学质量

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Analytical Higher-Order Model for Flexible and Stretchable Sensors

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Chinese Journal of mechanical engineering 2015年第2期28卷 379-386页

作者： ZHANG Yongfang ZHU Hongbin LIU Cheng LIU xu LIU Fuxi L Yanjun school of Printing and Packaging engineering Xi'an University of Technology State Key Laboratory for Strength and Vibration of mechanical Structures Xi'an Jiaotong University College of engineering Michigan State University school of mechanical and Precision Instrument {2. Xi'an University of Technology school of mechanical {2. Xi'an Aeronautical University

The stretchable sensor wrapped around a foldable airfoil or embedded inside of it has great potential for use in the monitoring of the structural status of the foldable *** design methodology is important to the development of the stretchable sensor for status monitoring on the foldable *** to the requirement of mechanical flexibility of the sensor,the combined use of a layered flexible structural formation and a strain isolation layer is *** analytical higher-order model is proposed to predict the stresses of the strain-isolation layer based on the shear-lag model for the safe design of the flexible and stretchable *** normal stress and shear stress equations in the constructed structure of the sensors are obtained by the proposed *** stress distribution in the structure is investigated when bending load is applied to the *** numerical results show that the proposed model can predict the variation of normal stress and shear stress along the thickness of the strain-isolation（polydimethylsiloxane）layer *** results by the proposed model are in good agreement with the finite element method,in which the normal stress is variable while the shear stress is invariable along the thickness direction of strain-isolation *** high-order model is proposed to predict the stresses of the layered structure of the flexible and stretchable sensor for monitoring the status of the foldable airfoil.

关键词： flexible and stretchable sensors higher-order shear-lag model normal stress shear stress

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