锁扣半固态压铸模具及压铸工艺研究

研究了半固态流变压铸成形技术,设计并制造出不同内浇道尺寸的锁扣半固态压铸模,利用模拟软件对半固态流变压铸充型及凝固过程进行了数值模拟,并进行了试验验证。结果表明,模具温度对半固态压铸影响较大,应保持在250～300℃。压铸模内浇道尺寸也有重要影响,较大内浇道面积(17mm2)的铸件硬度优于较小内浇道面积(11mm2)的铸件硬度。试验得到的最优半固态压铸工艺参数,压射速度为1m/s,模具预热温度为240℃,浆料温度为590℃。     

Identification of structural entities in NdF3-LiF melts with cryoscopic method

Nd-F species in NdF3-LiF melts were studied using cryoscopic method.Liquidus temperatures of melts of various compositions were determined by differential thermal analysis(DTA).Based on the different model calculations,NdF4- was identified as the most likely Nd-F entity in the melts in which the mole fraction of NdF3 was lower than 20%,considering only one single Nd species in the melt,and which was formed in accordance with Temkin model or Flood model.Then,activities of different components in the melts were researched.The results show that activity of LiF decreases,and that of NdF3 increases with increasing the mole fraction of NdF3.The value of activity coefficient of NdF3 is higher than 1,and that of LiF is lower than 1.     

Numerical investigation of optimal geometry parameters for ejectors of premixed burner简

An ejector of low NO~ burner was designed for a gas instantaneous water heater in this work. The flowing and mixing process of the ejector was investigated by computational fluid dynamics （CFD） approach. A comprehensive study was conducted to understand the effects of the geometrical parameters on the static pressure of air and methane, and mole fraction uniformity of methane at the outlet of ejector. The distribution chamber was applied to balance the pressure and improve the mixing process of methane and air in front of the fire hole. A distribution orifice plate with seven distribution orifices was introduced at the outlet of the ejector to improve the flow organization. It is found that the nozzle exit position of 5 mm and nozzle diameter d 〉1.3 mm should be used to improve the flow organization and realize the well premixed combustion for this designed ejector.     

连通式油气悬挂车辆三种行驶状况下数学模型的建立

介绍了连通式油气悬挂车辆在正常行驶、两侧车轮载荷不同及车辆转弯时三种不同状态下数学模型的建立。同独立式油气悬架相比较,能够大大增强整车的侧倾角刚度,减小车辆转弯时车架的侧倾角。通过不同的连接方式,还可以起到抗点头作用,从而提高了车辆行驶的稳定性。     

取暖器反射壳的Pro／E参数化设计及宏程序编程

取暖器采用Pro／E参数化系统进行设计，可以修改某一单独特征的参数值，使其他与之存在依存关系的特征随之变更，以保持整体的设计意图。同时采用倒装式复合模具对取暖器反射壳进行加工，在压力机一次行程内完成落料、冲孔、拉深等数道工序，而冲压毛坯无需进给，由于不受送料误差的影响，因而内外形相对位置及零件尺寸的一致性非常好，制件精度高、表面品质好，适宜薄壁件的冲制。该设计的程序编制部分采用了用户宏程序进行解决，使高效自动化机床更好地发挥效益，提高了数控性能。     

集中式智能电表的电磁兼容设计

集中式智能电表电磁兼容性的强弱是衡量其性能优劣的重要指标,是整个系统设计的重要环节。     

重视熵权的供应商选择DEA/TOPSIS联合方法

通过分析和总结供应链环境下战略供应商评价选择的准则、指标和方法,以供应链核心企业选择战略性供应商为目标,提出了战略性供应商评价的指标体系.研究了一种新的DEA模型,首先利用熵权法为各指标确定一个权重,然后利用线性加权方法将其与C2R模型的自由权重合成生成综合权重,并使用DEA/TOPSIS联合方法解决供应商选择问题,克服了DEA法与TOPSIS法单独应用时各自存在的不足.实证分析证明了该模型及方法的有效性,并为重视熵权的DEA/TOPSIS联合法在多目标规划中的运用提供了依据与参考.     

SiCp／7090Al复合材料的湿摩擦磨损性能

对元素粉末热压法制备的体积分数为12％5μmSiCp／7090Al复合材料销与40Cr盘摩擦副和铝青铜销与40Cr盘摩擦副试样,在驻退液浸渍条件下的湿摩擦磨损性能进行了试验研究。结果表明,在本试验的条件下,复合材料的磨损减重小于铝青铜,其与40Cr盘之间的摩擦系数较铝青铜要小,而且复合材料销与40Cr摩擦面的粗糙度也好于铝青铜-40Cr。     

SiCp／7090A1复合材料的两步复合及半固态压铸成型

提出了固态复合的概念,并采用两步复合法试验研究了SiC颗粒与纯Al的预复合工艺、预复合块与贫铝7090A1合金液的二次复合工艺以及复合浆料的压铸工艺,成功制备出含SiC体积分数为10％的SiCp7090A1复合材料半固态压铸件。显微组织观察表明,SiC颗粒在所制备的复合材料基体中分布均匀,且与基体合金结合良好。     

燃煤锅炉改用天然气锅炉供热技术探讨

从燃烧器和锅炉本体的选择、热网改造、建筑节能技术的应用等方面出发,对燃煤锅炉改用天然气锅炉供热的技术进行了探讨,阐述了供热负荷的调节方法,总结了天然气锅炉运行过程中需注意的问题,以促进改造工程的顺利实施。