Velocities of acceleration of plates made of different materials by detonation products

Velocities of acceleration of plates made of different materials by explosion products from the end face of a small-thickness charge are measured. Velocities of acceleration of non-porous metal plates with an identical mass, made of aluminum, steel, copper, and tantalum differ by less than 5%. The difference in velocities of acceleration of porous plates made of the same materials and plates with an identical mass but made of several layers of different materials reaches 20%. Layered plates with aluminum layers of different porosities can be accelerated to higher velocities than solid plates. No decrease in velocity is observed in the case with a talcum layer placed under a steel plate of the same thickness, i.e., with an increased total mass. The effects observed can be explained by the wave approach to considering the process of plate acceleration. __________ Translated from Fizika Goreniya i Vzryva, Vol. 45, No. 3, pp. 118-123, May–June, 2009.     

前叉下管铸件的铸造工艺设计

介绍了前叉下管铸件的结构及技术要求,详细阐述了其铸造工艺设计:采取垂直分型,膨润土湿型砂造型;采用底注式浇注系统,圆锥形直浇道的截面面积为972 mm2,横浇道与直浇道、内浇道相连接,横浇道为截面积1 200 mm2的标准梯形浇道,内浇道的截面面积为420mm2,选用六角形浇口杯,浇注速度为8.12kg/s,浇注时间为5s,浇注温度为1580℃;采用12个尺寸为30mm×60mm×75mm的冷铁,选用腰形暗冒口,尺寸为a=50 mm,b=100 mm,h=100 mm;选择扁形出气孔。模拟结果显示,整个铸件未发现有缩孔、缩松等铸造缺陷,而且工艺出品率也达到了76.53%。     

挤压筒损坏原因分析及其预防措施

分析了建筑铝合金型材挤压筒内衬破裂和挤压筒前端面与模套密封处磨损的原因，提出了相应的预防措施。     

前围内板横梁的工艺分析及模具设计

对前围内板横梁的冲压工艺性进行了分析,详细介绍了前围内板横梁修边冲孔模的结构.通过对模具设计过程的介绍,阐述了汽车覆盖件模具的设计要点.该模具虽然结构复杂,但设计合理,在生产中使用效果良好,满足了产品设计要求,提高了生产效率.     

Corrosion pathways in aluminium alloys

The corrosion pathways in AA2024-T3, AA5083-O and AA6082-T6 alloys have been investigated. The objective of the investigation is to further the understanding of the complex localised corrosion mechanism in aluminium alloys. The investigation was carried out by examining the corroded surfaces of the alloys after potentiodynamic polarization tests in a 3.5% NaCl solution with the aid of a scanning electron microscope, and by analysing the flow of anolyte solution using the scanning vibrating electrode technique. The results revealed that the overall corrosion pathways in the alloys are distinctively different and are influenced by the flow of anolyte solution. Also revealed, was the fact that corrosion propagates in two ways (particularly in the AA5083-O and AA6082-T6 alloys): an overall pathway in the corrosion front (filiform-like pathway in the AA5083 alloy and organized linear pathways in AA6082 alloy); and the crystallographic channelling along the 〈100〉 directions. These are dependent on the grain distinct features of the AA5083-O and AA6082-T6 alloys and are not influenced by the presence of coarse second phase particles in these alloys, compared with the AA2024-T3 alloy, where the corrosion pathways are more dependent on the presence of second phase particles and grain boundary character.     

基于折合应力正面角焊缝T形焊接接头的尺寸设计

角焊缝接头在工程中应用广泛,由于焊缝接头应力分布不均匀,它成为结构的薄弱环节.焊缝折合应力是国际焊接学会推荐用于计算焊缝静载强度的,该应力公式反应折合应力与焊缝内部切应力与正应力的关系.文中以正面角焊缝T形焊接接头为分析对象,假设角焊缝断裂发生在折合应力最大值所在的截面,分析得出Q345正面角焊缝T形焊接接头最大折合应力与承载力和焊缝尺寸的关系.基于承载能力和等强度准则设计焊缝尺寸,并通过有限元软件对T形焊接接头进行数值模拟,其数值模拟结果与理论计算结果基本一致,说明基于折合应力设计正面角焊缝T形焊接接头焊缝尺寸是可行的.     

Experimental analysis of the ignition front propagation of several biomass fuels in a fixed-bed combustor

Fixed-bed combustion in a tube reactor is a useful procedure to exploit a large variety of biomasses obtaining accurate in-bed data. In this paper, the ignition front propagation velocity is experimentally studied in a counter-current process for eight different biomass fuels with a wide range of origins, compositions and packing properties. Air mass flow rate is the main operative parameter and clearly distinguishes three stages of combustion (oxygen-limited, fuel limited and cooling by convection). The impact of the excess air ratio is also analyzed. This parameter confirmed that the maximum front velocity is achieved under sub-stoichiometric conditions, where the cooling effects of excessive air are minimized. Other variables with a major influence on the ignition front velocity are moisture and ash content. Finally, an uncertainty analysis is included to determine the accuracy of the entire measurement process.     

排风扇前盖注射模设计

分析了排风扇前盖塑件的工艺特点,介绍了排风扇前盖注射成型模结构及模具的工作过程。     

Effect of particle size and grain composition on two-dimensional infiltration process of weathered crust elution-deposited rare earth ores

The two-dimensional infiltration experiment was carried out by means of digital image technology. The evolution process of the wetting body was described. The wetted front distance and the time show a very significant power function relationship. The horizontal wetted distance is larger than the vertical wetted distance in the initial stage. Then, the vertical distance of the wetted body gradually approaches to the horizontal distance. The infiltration distance decreases as the content of fine particles increases. The wetted front migration rate curve shows a three-stage change law, and it increases with the increase of coarse particle content. The directional velocity ratio is defined. The initial value of horizontal infiltration rate is larger than that of vertical one, and then the vertical infiltration rate is gradually close to the horizontal value. The empirical relationship between the characteristic particle size and the stable infiltration rate is established, which provides a theoretical basis for the prediction of the stable infiltration rate in in-situ leaching.     

基于EFDC的九龙江口-厦门湾三维潮流及盐度数值模拟研究

环境流体动力学模型(EFDC)集水动力模块、泥沙输运模块、污染物运移模块和水质预测模块于一体,可以用于河流、湖泊、水库、湿地和近岸海域一维、二维和三维物理和化学过程的模拟。为了研究岛屿多、岸线地形及流态复杂的九龙江口-厦门湾水动力过程,该文将EFDC模型运用于该水域三维潮流及盐度场的数值模拟,对比实测资料校核了模型参数,利用实测潮位、流速和盐度数据对模拟结果进行了充分的验证,吻合度高。该水域属于规则半日潮类型,平均涨、落潮历时约6 h;潮流以往复流运动为主,表层流速最大可达2 m/s;低平潮前后出现面积合计约74 km2的多处露滩;发现河口区分层及不同类型的盐度锋现象均在低潮后1 h时最显著。结果表明,该模式成功复演了九龙江口-厦门湾潮汐潮流和盐度场的时空变化过程,适用于模拟和分析河口及近海海域的水动力场。