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Numerical study on the fracturing mechanism of shock wave interactions between two adjacent blast holes in deep rock blasting

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Earthquake engineering and engineering Vibration 2019年第4期18卷 735-746页

作者： Yuan Wei Liu Shangge Wang Wei Su Xuebin Li Zonghong Li Jiaxin Wen Lei Chang Jiangfang Sun Xiaoyun School of Civil engineering Shijiazhuang Tiedao University Shijiazhuang 050043 China Hebei Technology and Innovation Center on Safe and Effi cient Mining of Metal Mines Shijiazhuang 050043 China cccc Seco.d Highway co.sultants co. Ltd. Wuhan 430056 China China National Uranium co. Ltd. Beijing 100013 China

With the application of electronic detonators, milliseco.d blasting is regarded as a signifi cant promising approach to improve the rock fragmentation in deep rock blasting. Thus, it is necessary to investigate the fracturing mechanisms of short-delay blasting. In this work, a rectangle model with two circle boreholes is modeled as a particles assembly based on the discrete element method to simulate the shock wave interactions induced by milliseco.d blasting. The rectangle model has a size of 12 × 6 m (L × W) and two blast holes have the same diameter of 12 cm. The shock waves are simplifi ed as time-varying forces applied at the particles of walls of the two boreholes. Among a series of numerical tests in this study, the spacing between two adjacent boreholes and delay time of milliseco.d blasting are co.sidered as two primary variables, and the deco.pling charge with a co.ffi cient of 1.5 is taken into acco.nt in each case. The results show that stress superposition is not a key factor for improving rock fragmentation (tensile stress interactions rather than co.pressive stress superposition co.ld aff ect the generation of cracks), whereas co.lision actions from isolated particles or particles with weakened co.straints play a crucial role in creating the fracture network. The delay time has an infl uence on causing cracks in rock blasting, however, whether it works heavily depends on the distance between the two holes.

关键词： rock fragmentation milliseco.d blasting shock wave deco.pling charge discrete element method

Effect of Al co.tent on modification behavior of non-metallic inclusions in high-strength steel treated with rare earth

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Journal of Iron and Steel Research International 2024年第8期31卷 1886-1899页

作者： Zhan-peng Tie Xue-yuan Jiang Hai-yan Tang ·Gen Li Yu-hang Wang Jia-quan Zhang School of Metallurgical and Eco.ogical engineering University of Science and Technology BeijingBeijing 100083China co.tinuous Casting Business Section CISDI Engineering Co.Ltd.Chongqing 401122China special Steel Institute Central Iron and Steel Research Institute Co.Ltd.Beijing 100081China

The influence of Al co.tent(0.0053,0.0171,and 0.0578 wt.%)on the modification behavior of non-metallic inclusions in 20CrMoVTiB steel treated with rare earth elements was studied through high-temperature experiments and thermodynamic *** results showed that the modification products varied with the Al co.tent in steel under 0.01 wt.%of Ce *** formation sequence of typical rare earth inclusions in steel with the increase in Al co.tent was Ce_(2)O_(3)→CeAlO_(3)→CeAl_(11)O_(18),and the final stable products were highly Al co.tent *** the Al co.tent was 0.0053 wt.%,the stable phase in steel was Ce2O3;while the[Al]reached 0.0171 wt.%,the stable phase became CeA1O_(3).As the A1 co.tent reached 0.0578 wt.%,CeAl_(11)O_(18) became the stable *** a result,increasing the Al co.tent co.ld inhibit the precipitation of Ce_(2)O_(3) inclusions in steel while promote the formation of CeAIO3 and CeAl_(11)O_(18) *** addition,both Ca treatment and Ce treatment co.ld effectively refine the size of inclusions in steel by changing their ***,the feeding amount of Ca wire into molten steel should be appropriately reduced under the co.dition of adding Ce simultaneously,which is expected to be beneficial for an improved Ce treatment effect.

关键词： Rare earth Al co.tent Steel Inclusion Thermodynamics Ca treatment

A review on adhesion behavior of chip seal pavement and aggregate

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Journal of Traffic and Transportation engineering(English Edition) 2024年第3期11卷 441-466页

作者： Yuming Zhou Zhuyi Peng Jinyu Wang Jianguo Wei Hao Liu Di Wang Jinming Li Key Laboratory of road Structure and Material of Ministry of Transport(Changsha) Changsha University of Science and TechnologyChangsha 410114China School of Traffic and Transportation engineering Changsha University of Science and TechnologyChangsha 410114China Wuhan Huike Testing co. Ltd.Wuhan 430000China Department of Civil engineering University of OttawaON KIN 6N5Canada cccc Infrastructure Maintenance Group co. Ltd.Beijing 100102China

Chip seal is widely used for preventive maintenance to mitigate pavement deterioration,but it is prone to aggregate loss during pavement *** further promote the development and application of chip seals in road engineering in China,the research progress of the adhesion behavior of aggregate and binder in chip seals was reviewed in this paper,focusing on the adhesion mechanism of emulsified asphalt and alkaline *** Influencing factors and evaluation methodology of chip seals'aggregate adhesion behavior were also *** results demonstrate that the adhesion process between emulsified asphalt and alkaline aggregate is divided into three processes including infiltration,demulsification,and cluster,which is more co.plicated when co.pared to hot *** designing a chip seal,not only the characteristics of single material should be paid attention to,but also the co.bination of binder and aggregate matters a *** form good adhesion between aggregate and asphalt binder,various influencing factors such as material selection,design method,and co.struction technical index should be co.sidered co.prehensively in the whole design,co.struction,and operation *** methods for evaluating adhesion behavior are summarized,including macrosco.ic adhesion performance tests,image analysis technology,and model *** is not objective to evaluate the aggregate adhesion behavior of chip seal only by a single evaluation method.A co.prehensive evaluation based on the micro-macro multi-scale method should be co.sidered in the future.

关键词： Chip seal Adhesion behavior Asphalt binder Aggregate

State of the Art Treatment of Non-Ferrous Castings 3-in-l Heat Treatment Systems co.bine Foundry Processes

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材料热处理学报 2004年第5期25卷 552-554页

作者： Volker R. Knobloch CEC - co.solidated engineering co. Inc.

The interior of a high-pressure die-casting is of an unsatisfactory quality. Engine blocks made with this die casting process show lower specific engine performance. Pressure die-casting can hardly be heat treated for obvious reasons. PSM (Precision Sand Molds) process uses sand and organic binder to generate a mold and even allows the manufacturing of co.plex diesel engine blocks in aluminum alloys. co.bined technologies are available for semi-permanent mold castings with co.es and castings made in Precision Sand Molds with organic binders. Castings are placed into the special heat treatment furnace immediately after pouring without the operations in stand alone machinery. This patented Sand Lion 3- in-1 technology processes hot castings and carries out three (3) foundry processes simultaneously in one (1) automated machine: 1) De-co.ing and sand removal; 2) Thermal sand reclamation; 3) Solution heat treatment of castings. The co.bination of several main casting processes is reflected in significant reductions of energy co.sumption, of production co.ts, and improving the quality of the castings. Audits in foundries using the 3-in-l process showed an average reduction in production co.ts of more than 30%.

关键词：沙模固溶热处理集成铸造流化床

Effects of sulfur addition methods and Ca-Si treatment on the microstructure and properties of 30MnVS

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International Journal of Minerals,Metallurgy and Materials 2009年第6期16卷 650-653页

作者： Guo-zhong Li Fu-ming Wang Rong Hui Wen-kui Cao School of Metallurgical and Eco.ogical engineering University of Science and Technology Beijing Beijing 100083 China Jiangyin Xingcheng special Steel co. Ltd. Jiangyin 214400 China

The effects of sulfur addition methods and Ca-Si treatment on the microstructure and properties of free-cutting non-quenched and tempered steel 30MnVS were investigated by using optical microsco.y, SEM and tensile test methods. The results show that sulfur addition methods influence the morphology of sulfides and the properties of 30MnVS slightly. Ca-Si treatment is beneficial for the formation of co.plex sulfides which normally have oxide co.es, therefore, improving the distribution of sulfides in the tested steel and enhancing its toughness. The two methods, pyrite addition during LF process and S wire feeding during VD process, slightly influence the morphology and distribution of sulfides and the properties of 30MnVS; Ca addition not only promotes the nucleation of sulfides on the co.es of calcium aluminate inclusions, but also creates modification effect on MnS, reducing the relative plasticity and hot deformability of sulfides during hot rolling process, thereby reducing the length/width value of sulfides and improving their distribution, and significantly enhancing its mechanical properties, in particular, the impact toughness increased by 30%.

关键词： free-cutting steel sulfur addition modification sulfide mechanical properties microstructure

Risk Assessment on the co.struction of Vacuum-Aided co.crete Filled Steel Tube Pouring

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Risk Assessment on the Construction of Vacuum-Aided Concrete...

Nonlinear Optimization of Orthotropic Steel Deck System Based on Response Surface Methodology

作者： Jianjun Wang Jianqiao He Yu Han Lijian Deng Wei Li Guangxi road and bridge engineering Group co. Ltd

The co.struction of co.crete-filled steel tube（CFST） pouring is a key process in the building of CFST arch bridges,directly affecting engineering quality and structure ***,the co.struction of CFST pouring has co.plex procedures and multiple risk sources,and major engineering problems often arise from inco.rect risk *** order to reasonably analyze the hazards of various risk sources to engineering,avoid major engineering problems,and improve engineering quality,risk assessment is co.ducted on the co.struction of CFST pouring in this ***,As Low As Reasonably Practicable（ALARP） and risk assessment matrix are introduced,and statistics are made of the occurrence probability and risk loss rating of three major risks in the co.struction of CFST pouring,resulting in one I-level risk,two II-level risks,five III-level risks,and two IV-level ***,seven unacceptable events requiring special attention from decision-makers are obtained through *** results of risk assessment can be used as a basis for the co.struction management of practical projects,and major risks are strictly co.trolled through strengthening management and other methods,which will effectively reduce risk levels,providing a powerful guarantee for increasing the span of CFST arch bridges.

关键词： Risk assessment,co.crete-filled steel tube (CFST) arch bridge probability,co.crete-filled steel tube(CFST) pouring

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Research 2020年第1期2020卷 28-49页

作者： Wei Huang Minshan Pei Xiaodong Liu Chuang Yan Ya Wei Intelligent Transportation System Research Center Southeast UniversityNanjing 210096China cccc Highway co.sultants co. Ltd.Beijing 100084China Department of Civil engineering Tsinghua UniversityBeijing 100084China

The steel bridge deck system,directly subjected to the vehicle load,is an important co.ponent to be co.sidered in the optimization design of the *** to its co.plex structure,the design parameters are co.pled with each other,and many fatigue details in the system result in time-co.suming calculation during structure *** view of this,a nonlinear optimization method based on the response surface methodology(RSM)is proposed in this study to simplify the design process and to reduce the amount of calculations during *** optimization design of the steel bridge deck system with two-layer pavement on the top of the steel deck plate is taken as an example,the influence of eight structural parameters is *** Box-Behnken design is used to co.struct a sample space in which the eight structural parameters can be distributed evenly to reduce the calculation *** finite element method is used to model the mechanical responses of the steel bridge deck *** the regression analysis by the RSM,the explicit relationships between the fatigue details and the design parameters can be obtained,based on which the nonlinear optimization design of the bridge deck system is *** influence of co.straint functions,objective functions,and optimization algorithms is also *** method proposed in this study is capable of co.sidering the influence of different structural parameters and different optimization objectives acco.ding to the actual needs,which will effectively simplify the optimization design of the steel bridge deck system.

关键词： steel fatigue system

Numerical Analysis of co.d-Formed Thin-Walled Steel Short co.umns with Pitting co.rosion during bridge co.struction

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Structural Durability & Health Monitoring 2024年第2期18卷 181-196页

作者： Hongzhang Wang Jing Guo Shanjun Yang Chaoheng Cheng Jing Chen Zhihao Chen cccc Seco.d Harbor engineering Third engineering co. Ltd.Zhenjiang212000China Suqian Highway Development Center Suqian223800China School of Mechanics and Civil engineering China University of Mining and TechnologyXuzhou221116China

Pitting co.rosion is harmful during bridge co.struction,which will lead to uneven roughness of steel surfaces and reduce the thickness of ***,the effect of pitting co.rosion on the mechanical properties of co.d-formed thin-walled steel stub co.umns is studied,and the empirical formulas are established through regression fitting to predict the ultimate load of web and flange under pitting *** detail,the failure modes and load-displacement curves of specimens with different locations,area ratios,and depths are obtained through a large number of non-linear finite element *** for the specimens with pitting co.rosion on the web,all the specimens are subject to local buckling failure,and the failure mode will not change with pitting co.rosion,but the failure location will change with pitting co.rosion location;the size,location,and area ratio of pitting co.rosion have little influence on the ultimate load of co.d-formed thin-walled steel short co.umns,but the loss rate of pitting co.rosion section area has a greater impact on the ultimate bearing *** for the specimen with flange pitting co.rosion,the location and area ratio of pitting co.rosion have less influence on the ultimate load of co.d-formed thin-walled steel short co.umns,and the section area loss rate has greater influence on the ultimate bearing capacity;the impact of web pitting co.rosion on the ultimate load is greater than that of flange pitting co.rosion under the same co.dition of pitting co.rosion section *** prediction formulas of limit load which are suitable for pitting co.rosion of web and flange are established,which can provide a reference for performance evaluation of co.roded co.d-formed thin-walled steel.

关键词： Pitting co.rosion co.d-formed thin-walled steel ultimate load prediction formula short co.umns

Solidification Structure of co.tinuous Casting Large Round Billets under Mold Electromagnetic Stirring

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Journal of Iron and Steel Research International 2016年第4期23卷 329-337页

作者： Tao SUN Feng YUE Hua-jie WU Chun GUO Ying LI Zhong-cun MA Metallurgical engineering Research Institute University of Science and Technology Beijing co.laborative Innovation Center of Steel Technology University of Science and Technology Beijing Beiman special Steel co. Ltd.

The solidification structure of a co.tinuous casting large round billet was analyzed by a cellular-automaton-finite-element co.pling model using the ProCAST software. The actual and simulated solidification structures were co.pared under mold electromagnetic stirring （MEMS） co.ditions （current of 300 A and frequency of 3 Hz）. Thereafter, the solidification structures of the large round billet were investigated under different superheats, casting speeds, and seco.dary co.ling intensities. Finally, the effect of the MEMS current on the solidification structures was obtained under fixed superheat, casting speed, seco.dary co.ling intensity, and MEMS frequency. The model accurately simulated the actual solidification structures of any steel, regardless of its size and the parameters used in the co.tinuous casting process. The ratio of the central equiaxed grain zone was found to increase with decreasing superheat, increasing casting speed, decreasing seco.dary co.ling intensity, and increasing MEMS current. The grain size obviously decreased with decreasing superheat and increasing MEMS current but was less sensitive to the casting speed and seco.dary co.ling intensity.

关键词： co.tinuous casting large round billet solidification structure cellular-automaton-finite-element method mold electromagnetic stirring central equiaxed grain zone grain size