矿用扩径式吸能构件吸能防冲特性研究

为增强液压立柱的防冲性能,有效防治煤矿冲击地压,或在一定程度上减小冲击地压事故造成的损失,提出了一种与液压立柱结合使用的扩径式吸能构件。采用理论分析和试验研究方法,对构件吸能防冲特性进行研究,结果表明：轴向压缩下扩径式吸能构件具有非常好的稳定性和可重复性的变形破坏模式,且构件变形后向四周膨胀值仅为薄壁圆管厚度,几乎不占用其它空间。扩径式吸能构件压缩过程中具有较为理想的力-位移曲线。扩径式吸能构件冲程效率不受几何尺寸影响,扩径式防冲构件具有较小的载荷波动系数。理论推导得出了构件吸能防冲评价指标,并与试验结果具有较好吻合,为构件选取提供了理论依据。扩径式防冲构件是较为理想的吸能防冲构件。     

Electromagnetic shielding effectiveness and mechanical property of polymer–matrix composites containing metallized conductive porous flake-shaped diatomite

The porous flake-shaped diatomite particles with different micropores diameter were used as forming templates for the fabrication of the conductive core–shell functional fillers by electroless silver plating. The surface morphologies and phase structures of the surface coatings onto diatomite particles with different micropores diameter were evaluated. The effects of micropores diameter on electrical resistivity, electromagnetic shielding effectiveness and mechanical property of polymer–matrix composites containing silver-coated diatomite particles were also investigated in detail. The results show that the micropores onto initial diatomite particles after plating are completely covered with the coating, while the micropores onto diatomite particles with expanding pores are still visible. The expanding micropores onto diatomite particles in certain size range have less impact on the phase structures, electrical resistivity and electromagnetic shielding effectiveness. However, the mechanical properties of composites are improved significantly after expanding micropores by HF acid corrosion.     

不同扩径率对Fe-Mn-Si-Cr形状记忆合金管接头形状记忆效应的影响

本文通过回复实验和回复抱管实验测试了不同扩径率条件下,Fe-Mn-Si-Cr形状记忆合金管接头形状记忆效应的特征参数.结果表明:5%左右扩径率的管接头具有较好的显微组织,是可回复应变量和回抱力的最佳组合,因此增强了管接头连接的可靠性.     

桐柏安棚碱矿扩边的理论与方法

介绍桐柏安棚碱矿扩边勘探过程,提出碱矿探边的一些基本原则,及探边使用的理论、技术、方法。经检验,这套理论、技术、方法是实用的,扩边结果与开发实践基本吻合,为碱矿生产、继续发展提供了依据,减少了不必要的浪费与开支。     

Comparison of Methods for Evaluation of Flow Properties of Powders and Granulates

Powder mixtures and granulates with bulk densities ranging from 0.35-0.89 g.ml^-1 were tested regarding flow properties using the following methods: the Hausner ratio (packed bulk density/loose bulk density), rate of packing on tamping, flow rate through a 30 mm orifice, orifice diameter allowing free flow, and “drained” angle of repose.

The Hausner ratio and the angle of repose could be measured with a relative standard deviation of about 2 %. The orifice diameter could also be determined accurately and these three methods correlated well with each other.

The flow rate could only be measured on free flowing materials and the packing rate correlated poorly with the other methods.     

以煤矸石为原料的水处理滤料的研制

研究了一种以煤矸石为主要原料,通过添加适量成型剂、膨胀剂,经高温烧结生产球型多孔轻质污水处理滤料的制造方法,并以滤料的比表面积、孔隙率为主要因子,考察原料配比、升温方式、成球时水加入量、终温及终温煅烧时间等参数对滤料理化性能的影响.结合扫描电镜分析了滤料微观结构,并对煤矸石烧结膨胀成孔机理进行了分析.通过正交试验确定了最佳工艺参数.主要配方为:煤矸石50-99%,粉煤灰0-25%,膨胀剂0.5-1.0%.所得成品滤料主要性能参数为:比表面积6.0-8.6m2/g,孔隙率40-50/%,堆密度0.9-1.1g/cm3,磨损率<2.0%,平均孔径85-190/μm.以煤矸石为原料生产球型多孔轻质污水处理滤料具有原料来源广泛、生产工艺简单、无污染、成本低、产品附加值高等特点,其生产可以利用现有水泥厂的生产设备与工艺转产.     

Comparison of Methods for Evaluation of Flow Properties of Powders and Granulates

Abstract

Powder mixtures and granulates with bulk densities ranging from 0.35-0.89 g.ml^?1 were tested regarding flow properties using the following methods: the Hausner ratio (packed bulk density/loose bulk density), rate of packing on tamping, flow rate through a 30 mm orifice, orifice diameter allowing free flow, and “drained” angle of repose.

The Hausner ratio and the angle of repose could be measured with a relative standard deviation of about 2 %. The orifice diameter could also be determined accurately and these three methods correlated well with each other.

The flow rate could only be measured on free flowing materials and the packing rate correlated poorly with the other methods.     

金属管环扩张率的修正

金属管环扩张试验是钢管型式检验的一个重要项目,但ISO 8495:2004中对于如何测量扩口试验后管环试样的尺寸却没有规定。在大量钢管环扩口试验的基础上,针对有的钢管扩口试验后断口无法并拢的情况,提出了计算断后管环尺寸的修正公式,并对钢管环的扩张率进行了修正。结果表明:对于扩口试验后断口无法并拢的试样,直接采用DIN 50137:1977中的扩张率公式计算得到的扩张率偏大,通过对断后管环尺寸和扩张率公式进行修正后,计算得到的管环扩张率结果更加合理。     

Nanocomposite microfiber spinning using a UV-curable polymer in an aqueous environment

We report a hydrodynamic assisted nanocomposite microfiber spinning method using a UV-curable polymer. In contrast to a large number of previously reported fiber spinning methods, all the fabrication processes in the present method are performed in an aqueous environment, based on a photopolymerization process. The diameter of the spun fiber can be easily controlled at the scale of hundred microns by varying the draw ratio (the ratio of the take-up speed to the extrusion speed). To characterize the hydrodynamic phenomenon of polymer drawing, an analytic model and relevant physical parameters are employed. We also demonstrate QD (quantum dot)-based RGB color-emitting nanocomposite fibers and hetero-structural nanocomposite fibers with an RGB color column showing a rotational symmetry of 120° in one-step fabrication. Our approach is straightforward to implement using a variety of UV-curable polymers and can be applied to fabricate nanocomposite fibers with various physical properties and geometries. The processing features enable diverse possibilities for preparing novel nanocomposite materials and expanding the potential application of spun fibers.     

DX桩技术的设备与工法概述

文章叙述了DX桩技术理论研究、设备工法及工程实践的发展过程,从DX桩挤扩设备的发明,到研制出钻扩清一体化机,直至今天又创新出HDX旋挖挤扩钻机,使DX桩技术取得了长足的进步和发展。     

椭圆孔扩孔性能的实验研究

通过对椭圆孔的扩孔实验，认为椭圆孔的扩孔性能与其长短轴的比例有关．在长短轴比ａ／ｂ不大于１．２时．对扩孔性能的影响不大．但当ａ／ｂ大于１．２时．对扩孔性能影响较为显著。     

测量不确定度及其应用

测量不确定度的定量表示是计量学领域中一个较新的概念。文中论述了标准不确定度、合成标准不确定度及扩展不确定度的评定方法。     

Electronic‐Type‐ and Diameter‐Dependent Reduction of Single‐Walled Carbon Nanotubes Induced by Adsorption of Electron‐Donor Molecules

The adsorption of the organic donor molecules tetrakis(dimethylamino)ethylene (TDAE) and cobaltocene (CoCp₂) on high‐pressure CO decomposition (HiPco) single‐walled carbon nanotubes (SWNTs) is investigated using density functional theory (DFT), optical absorption, and Raman spectra methods. The selective reduction of SWNTs according to the electronic type and diameter of SWNTs is revealed. The reduction rate decreases in the order: metallic SWNTs ≥ large‐diameter semiconducting SWNTs > small‐diameter semiconducting SWNTs.     

大口径、空心零件成形工艺

目的降低原材料的消耗,节约毛坯生产成本。方法改变成形方法,由原先的棒料锻造改为管料冲压成形,通过合理分配工序变形量,在小端收口的同时进行大端扩孔,经两次收口+一次扩口后冲压成形。结果不仅减少了原材料的消耗,而且减少了切屑工时。结论成功开创了大口径管材大扩孔量的先河,为今后成形更大直径的相似零件提供了强有力的技术支撑;同时采用了环形退料装置,优化了传统退料装置,消除了安全隐患,实现了半自动化卸料,可以同时满足大、中、小口径产品的退料要求,具有很好的推广和借鉴价值。     

膨胀管塑性膨胀过程摩擦问题研究

关于膨胀管膨胀过程中的摩擦问题,目前还没有文献考虑各因素对摩擦因素的影响,而摩擦因素对膨胀管的膨胀过程有直接的影响.根据膨胀管膨胀过程塑性成形特点,分析了膨胀管膨胀过程摩擦力的构成,讨论了管材材料、膨胀速度、膨胀锥表面状态、膨胀率等因素对摩擦因素的影响.在此基础上建立了膨胀过程摩擦力学模型,并用有限元建立了一个N80实体膨胀管模型验证膨胀管膨胀过程中摩擦因素对套管膨胀过程的影响,给出了摩擦因数分别为0.1,0.15,0.2,0.25,0.3时的等效应力云图.通过对等效应力云图分析发现,摩擦因数大于0.25时膨胀管内出现了明显的犁沟,而摩擦因数小于0.25时膨胀管内不会出现犁沟.有限元计算结果与膨胀管实际膨胀过程特点相吻合,在摩擦因素较大时很容易出现犁沟而使摩擦力增加.因此,在设计膨胀工艺时,应综合考虑各种情况,降低摩擦因素,以满足实际的工程需求.     

Transition of combustion into detonation within a channel with the diameter less than the critical diameter of the existence of stationary detonation

An experimental investigation was carried out for transition of combustion into detonation of oxygen-hydrogen and hydrogen-air stoichiometric mixtures within a cylindrical channel with a diameter of 3 mm, which is less than the critical diameter of the existence of stationary detonation in the hydrogen-air mixture. To realize the transition of combustion into detonation in the channel, the combustible mixture was ignited within a precombustion chamber with a diameter of 14.5 mm which was arranged in line with the channel on one of its faces. The expanding products of mixture combustion within the precombustion chamber accelerate the flame front at the input of the channel, thus increasing the energy amount released during mixture combustion within the narrow channel per unit time. As a result, the ratio of the burning energy to dissipative losses in channel walls increases, which makes transition into detonation realizable. The use of the precombustion chamber allowed us to obtain the transition of combustion into the detonation wave with the Chapman-Jouguet parameters at initial mixture pressures of 1 and 2 atm. The effect of the size of the turbulizing precombustion chamber on the length of the transition of combustion into detonation is analyzed, and the average velocities of flame front propagation along the channel are determined.     

Numerical Investigation of a Periodic Heating Thermal-Bubble Actuated Diffuser–Nozzle Valveless Pump

A valveless micropump actuated by thermal bubbles which generated by an electrode heater mounted with a pair of diffuser nozzles has been numerically studied by commercial CFD software FLUENT. The relationship between the net flow rate and the superheating and heat supplying frequency has been investigated. The depth of the diffuser–nozzle micropump used in current numerical simulation model is 200 μm, and the diameter of micropump chamber is 1 mm. The pair of diffuser–nozzles are with gaps expanding from 30 to 274 μm and open angles of 7°. The working fluid is methanol in present study. The results show that the pump has different optimal driving frequency with different superheating. The cycle composed of bubble growth and shrinking costs more time at higher superheating. The maximum volume flow rate and the maximum pump pressure will increase with increasing superheating, simultaneously; and the optimal pulse duty, the maximum volume flow rate and pump pressure decrease with increasing superheating. The maximum volume flow rate and the maximum pump pressure are 29.6 μL/min and 680 Pa at ΔT = 15°C, respectively.     

Effect of Electrode Size on the Performances of Micro-EDM

Understanding the effect of processing parameters on the tool electrode wear during micro-electrical discharge machining (micro-EDM) is helpful to predict and compensate the electrode wear, so as to improve the machining precision. In this paper, experiments are carried out and the influences of tool electrode diameter on the micro-EDM process are discussed based on the skin effect and area effect. It is demonstrated that the machining speed, tool wear, and taper rate are different with the increase of tool electrode diameter. Due to the skin effect and area effect, larger electrode diameter results in higher material removal rate along with higher tool wear rate. The electrode material removal increment is more than the workpiece material removal increment with the increase of tool electrode diameter, which leads to the increase of relative tool wear ratio. Discharge energy is concentrated on the tool surface which enhances the possibility of discharge on the side face and the corner of the tool electrode during the micro-EDM, especially when drilling with a larger tool electrode. As a result, a tool electrode with larger diameter results in a higher taper rate.     

某稠油井用高温蒸汽注汽管爆裂失效分析

通过对某油田稠油井发生爆裂的高温蒸汽注汽管进行宏观分析、化学成分分析、金相检验、力学性能测试以及扫描电镜断口分析,找出了该管爆裂失效的原因.结果表明:该高温蒸汽注汽管线的爆裂性质为脆性开裂,开裂起源于管表面的两处机械损伤;导致其爆裂失效的主要原因是该管在服役过程中由于水击作用发生了胀径,使注汽管壁厚不均匀;同时管表面存...     

Computational comparisons of homogeneous and statistical descriptions of AerMet100 steel subjected to high strain rate loading

In order to simulate the effect of material microstructure a statistically compensated Johnson-Cook (JC) fracture model has been implemented into the Eulerian shock physics code, CTH. This model uses a Weibull function to produce a distribution of initial failure strains within the JC fracture model. A parametric analysis where the Weibull modulus was systematically varied was conducted on two sets of experimental fragmentation data. The first experiment consisted of an explosively loaded cylinder of AerMet100. The second was an expanding tube experiment which used a plastic cylinder to load the AerMet100 and provided a problem at a lower strain rate. In both sets of experiments, the fragments were soft captured for later examination. While CTH does not explicitly track fragments, a post processor written at the Naval Surface Warfare Center Dahlgren Division was used to calculate the mass of each of the fragments in the expanding debris cloud. The results were analyzed and compared back to baseline homogeneous calculations. The use of a statistically compensated JC fracture model substantially improved the fragment mass distribution for the explosively loaded cylinder. However, the lower strain rate expanding tube showed only minimal improvement. A probable reason for this limitation and future analysis are discussed.