无心外圆精磨机床进给成形辊子的解析计算

针对超精加工机床辊子装置的计算都具有近似性,很难估算计算误差,讨论了无心超精加工机床加工外凸滚子成形时,机床辊子的解析解,拟订了超精加工机床进给辊子成形的算法,弥补了设计无心超精加工机床进给装置一般方法不能进行准确计算的缺陷,采用此方法可以使机床多波度辊子各段具有更为理想的廓形,大大提高了制造外凸度滚子的精度。     

二氧化碳/二甲醚混合工质热泵系统循环性能分析

在相同的工况条件下,对二氧化碳(R744)/二甲醚(RE170)混合工质与四种常见的热泵工质R22、R134a、R410A和R407C的亚临界循环性能进行了分析计算。结果发现,在R744/RE170质量配比为30/70下,系统的制热循环性能系数最大,其值为4.922,分别比R22、R134a、R410A和R407C系统提高了17.53%、30.52%、19.09%和16.52%;此时,系统的冷凝压力为2.276MPa仅高于R134a系统,压缩机压比为3.708,压缩机出口工质排气温度为92.6℃。     

Effect of thermal stresses on the microstructure of the continuous cooling TiAl alloys

A series of continuous cooling tests were performed on TiAl alloys using a Gleeble3500 machine to investigate the effect of thermal stresses on the microstructure. The results show that macroscopic thermal stresses promote correlated nucleation of γ lamellae. The trend of the dominance of one twin-group γ variants in local regions is weakened, and the γ/γ interfaces tend to be true twin and pseudotwin boundaries rather than 120° rotational faults under macroscopic thermal stresses. Meanwhile, thermal-induced deformation generated under the effect of both microscopic and macroscopic thermal stresses results in numerous low angle grain boundaries (LAGBs) and dislocations. The LAGBs and dislocations distribute heterogeneously among lamellar colonies and phases. No mechanical twins are observed due to the low strain and low strain rate characteristics of the thermal-induced deformation. These findings could shed light on understanding and preventing the cracking of TiAl components during cooling process.     

Systematical study on the roles of transition alloying substitutions on anti-disproportionation reaction of ZrCo during charging and releasing hydrogen

Intermetallic alloy ZrCo is believed to be a good substitution for uranium to store tritium. Nevertheless, disproportionation reaction often happens during the hydriding and dehydriding processes, and hydrogen storage property of ZrCo is therefore degraded. Alloying elements are often used to substitute Zr or Co in ZrCo to restrain disproportionation reaction. However, many experimental results do not agree with each other, and it lacks overall tendency for all transition metal elements. In this work, systematical ab initio calculations are performed to study more than 20 transition alloying elements to substitute Co and Zr in ZrCoH₃ to study the anti-disproportionation effects. It is found that substitution of Co by transition metal elements on anti-disproportionation reaction is unconspicuous, and only Ni can enlarge Zr–H bond length and decrease the volume of 8e site, presenting anti-disproportionation effect, which qualitatively agrees with the previous experiments. In contrast, all transition alloying elements considered except Fe, Co, Ni, Ru, Rh, Pd, Os and Ir replacing Zr can both enlarge the length of Zr–H bond and decrease the volume of 8e site, and thus restrain the disproportionation effects. At last, two-dimensional charge density and density of states are calculated to analyze the underlying mico-mechanisms affecting the effects of transition alloying elements on anti-disproportionation reaction.     

基于渗流特征的低渗透致密砂岩气藏气井生产规律

低渗透致密气藏的气井存在井底或井口压力、产量随开采生产时间延长而快速下降的特征,掌握其随开采生产时间变化的规律,可在开发早期准确预测气井稳产年限和递减规律,测算经济可采储量,指导气井工作制度的合理调整和气田合理开发。以渗流理论为指导,以气井长期生产过程中取得的大量生产动态数据为基础,以不同生产阶段进行的压力恢复试井成果为检验手段,借鉴不稳定试井资料解释方法,研究了此类气井压力、产量与开采生产时间等参数间的关系,并在气井生产历史拟合、生产动态预测等方面进行了实际应用。通过研究,认为具有人工裂缝的气井压力响应特征多符合地层线性渗流模型,且地层线性流动期持续时间较长,这对同类气藏的开发具有指导意义。     

纳米智能调温毛织物的开发

采用微胶囊纳米技术开发智能调温毛织物.选取石蜡作为芯材,双酚A作为壁材,制备具有持久性的相变材料微胶囊,采用浸渍法用该相变材料微胶囊整理毛织物以使其具有智能调温性能.分析了相变材料微胶囊处理后的毛织物的智能调温作用机理,建立了智能调温毛织物的理想吸热模型.对影响毛织物整理效果的相变材料微胶囊制备工艺进行了分析,给出了毛织物根据调温作用大小所需相变材料微胶囊用量的计算公式.     

PCBN整体烧结刀片在切削加工中的应用

耐磨耐蚀领域中零件的硬度普遍较高,使得加工非常困难,普通的刀具不能胜任,即使勉强使用,生产效率却很低。选用超硬材料刀具是破解这一加工难题的有效手段。其中PCBN刀具是硬切削的优选对象,尤其适合自动化加工和高精度加工。介绍了我们研制的一种PCBN整体烧结刀片,这种刀片能够满足大切深、高速度的切削要求。将其应用于车削、断续切削、螺纹切削及铣削等硬态切削加工领域的结果表明,使用该刀具,不仅使高铬铸铁、硼铸铁、冷硬铸铁等高硬度材料的加工效率大幅度地提高,而且能够保证加工表面质量。     

振子驱动型牵引传动研究

在常规牵引传动和往复牵引传动的基础提出了一种依赖反复微小振动进行动力传动的振子型牵引传动。先通过振子振动形成油膜实验得出在接触区施以微小振动更易形成油膜的结论,又通过圆周运动型牵引传动实验得出了其相对于摩擦传动磨损小的优点。利用微小振动形成润滑油膜的方法引起的磨损小,可广泛应用于光学聚焦等精密运动领域。     

模块化多电平变频驱动系统的转矩脉动最小化控制

应用基于两电平变频器的传统感应电机驱动系统存在输出转矩脉动较大的问题。针对这个问题,设计了一种模块化多电平变频器驱动的多极感应电机转矩脉动最小化控制方案。基于多极感应电机设计了其多电平驱动变频器拓扑,并采用了一种单极性的载波移相空间矢量脉宽调制技术进行控制。通过脉冲序列生成分析和计算,系统的低次输出谐波都达到了开关频率的四倍频以上,进而有效降低了转矩脉动。基于模块化多电平变频器的多级感应电机驱动试验平台进行了对比试验研究,试验结果验证了在新型控制策略下的有效性,电机转矩脉动得到了明显改善。     

罗布麻/牛奶蛋白纤维与棉混纺精梳纱工艺

介绍了罗布麻纤维和牛奶蛋白质纤维的特点。通过工艺试验和测试．分析了纤维性能、纺纱工艺等因素对罗布麻／牛奶蛋白质纤维混纺纱质量的影响，探讨了提高罗布麻/牛奶蛋白质纤维混纺纱质量的技术措施。