峨眉黄山石灰石矿区爆破参数优化

针对峨眉黄山石灰石矿山爆破过程中存在爆后大块率高、根底多且产生爆破裂隙等问题,在现场调研的基础上分析其产生原因,确定影响爆破效果的主要因素是爆岩的性质、炸药性能及炸药与岩石的匹配关系以及爆破参数。结合矿山实际情况,对岩石进行可爆性分级,确定了该岩石属坚固岩石,选择了与其匹配性好的乳化炸药。采用经验公式与现场爆破实验相结合的方法,设计起爆顺序、孔网参数、炮孔超深等方案并对其进行优化,从而确定合理的爆破参数。优化结果表明:当爆破参数中孔径138mm、孔距6m、孔深17m、超深2m、填塞长度5m、抵抗线4m、单孔药量216kg、延时间隔时间65ms(N3实验)时比较合理,可以达到降低大块率、减少根底和避免爆破裂隙的目的。     

峨眉黄山石灰石矿区爆破参数优化

针对峨眉黄山石灰石矿山爆破过程中存在爆后大块率高、根底多且产生爆破裂隙等问题,在现场调研的基础上分析其产生原因,确定影响爆破效果的主要因素是爆岩的性质、炸药性能及炸药与岩石的匹配关系以及爆破参数。结合矿山实际情况,对岩石进行可爆性分级,确定了该岩石属坚固岩石,选择了与其匹配性好的乳化炸药。采用经验公式与现场爆破实验相结合的方法,设计起爆顺序、孔网参数、炮孔超深等方案并对其进行优化,从而确定合理的爆破参数。优化结果表明:当爆破参数中孔径138mm、孔距6m、孔深17m、超深2m、填塞长度5m、抵抗线4m、单孔药量216kg、延时间隔时间65ms(N3实验)时比较合理,可以达到降低大块率、减少根底和避免爆破裂隙的目的。     

台阶深孔爆破岩体位移的高速摄影研究

采用变直径深孔爆破工艺可较好地解决露天矿高台阶开采的爆破根底问题,笔者对等直径和变直径2种深孔形式爆破后岩体位移情况采用高速摄影手段进行了分析和研究,得出了一些有意义的结论,为在高台阶开采的矿山推广变直径深孔爆破提供一些有益的探索.     

起爆方式对台阶爆破根底影响的数值模拟分析

在台阶爆破中,根底率是评价爆破效果的一项重要指标。根据爆前、爆后岩体声波降低率,计算爆后保留岩体的损伤大小,确定临界破碎状态对应的损伤阈值。基于LS-DYNA的二次开发爆破损伤模拟技术,采用拉压损伤模型,对台阶爆破不同起爆点位置的爆破损伤效应进行数值模拟,并重点比较正向起爆和反向起爆条件下,相邻炮孔之间爆破根底的分布情况。模拟结果表明:起爆点位置能够影响能量和应力的分布状态,导致不同的爆破效果,正向起爆对孔底岩体有较好的破碎效果,能够有效地消除爆破根底,提高爆后台阶面的平整度。     

变直径与等直径深孔爆破效果数值模拟优化

对等直径和变直径2种深孔形式爆破后岩体的位移进行了数值模拟,得出了采用变直径深孔爆破工艺可较好地解决露天矿高台阶开采的爆破根底问题等有意义的结论,为在高台阶开采的矿山推广变直径深孔爆破提供了一些定量指导依据.     

镇沅金矿中深孔爆破参数数值模拟研究

镇沅金矿一直采用无底柱分段崩落法进行回采,但爆破中存在大块率高、缩口比较严重等问题。为了确定合理的爆破参数,运用ANSYS/LS-DYNA数值模拟软件对扇形炮孔爆破过程进行数值模拟,再现扇形炮孔爆破应力场变化过程,分析了爆炸仿真过程中的Von Mises有效应力峰值,确定了中深孔爆破最优的最小抵抗线和最大孔底距,为中深孔爆破提供理论依据。并对此参数进行了现场试验,现场中深孔爆破后,爆破效果良好,进一步证明了所确定的最小抵抗线为1.5 m,最大孔底距为2.0 m为最优爆破参数。     

金鼎钨钼矿露天台阶深孔爆破参数优化

为解决金鼎钨钼矿生产中存在的大块率过高、根底残留等问题,通过力学实验研究、数值模拟和现场试验,对该露天台阶深孔爆破参数进行优化。通过常规三轴试验研究,得到了该矿岩力学参数和矿岩性质,确定其矿岩炸药单耗0.68 kg/m~3;运用ANSYS/LS-DYNA软件对爆破参数进行优化,以炮孔密集系数m为变量,通过比较坡底、坡顶有效应力与岩石的动抗拉强度,判断相应炮孔密集系数下矿岩的爆破效果。结果表明:当炮孔密集系数m=1.5时,坡底和坡顶岩石均被破坏,大块明显减少,振动危害也小,达到预期爆破效果。将优化后的爆破参数(孔径d=20 cm,炸药单耗q=0.68 kg/m~3,炮孔密集系数m=1.5,孔排距为600 cm×400 cm)应用于生产现场,爆破效果大为改善,大块率低于5%。可以为类似极硬岩矿山提供参考经验。     

台阶深孔爆破岩体移动速度的高速摄影研究

采用变直径深孔爆破工艺可较好地解决露天矿高台阶开采的爆破根底问题,对等直径和变直径2种深孔形式爆破后岩体移动速度情况采用高速摄影手段进行了分析和研究,为在高台阶开采的矿山推广变直径深孔爆破提供一些有益的参考依据.     

松花江旧铁路大桥桥墩的水下爆破拆除

旧松花江铁路大桥的上部结构拆除后 ,采用深孔和浅孔爆破相结合的方法将位于主航道内的桥墩拆除。利用钻孔探明了桥墩的结构和配筋情况。文中论述了爆破方案的确定和水下深孔爆破炸药单耗的选取 ;介绍了炮孔布置参数、装药结构和参数、起爆方法 ;同时对爆破安全性进行了预估。     

孤石深孔爆破对临近竖井的振动影响研究

采用现场测试和数值分析相结合的方法,研究了孤石深孔爆破对临近竖井结构振动影响.结果表明:减振孔可以有效减缓孤石爆破对竖井基坑围护桩的破坏;隔离孔可以保证相临爆区孤石的完整性;增加孤石爆破分区,减小炮孔间距,减少一次爆破量,可以有效控制竖井爆破振速.以孤石分区5区为例,将炮孔间距调整为0.5 m×0.4 m,炸药直径调整...     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...