铸钢件凝固模拟中的熔池划分技术

研制了铸钢件凝固过程数值模拟中进行识别多个熔池的技术 ,利用此技术可将铸钢件凝固过程中所形成的多个相互孤立的熔池一一区分开 ;在此基础上 ,能够更加准确地预测由各个孤立的熔池所形成的缩孔 ,依此提高了铸钢件凝固过程数值模拟中对缩孔位置和形状预测的准确度     

铸件凝固过程孤立域动态划分及缩孔缩松数值模拟

在铸钢件实际生产中，一般凝固过程同时存在着多个熔池孤立域，而各熔池孤立域的补缩行为只限于各自孤立的熔池中．利用“虚拟传热技术”，开发了一种铸件凝固过程数值模拟动态判定孤立熔池域的方法，快速而方便地实现了凝固过程存在多个可补缩域的判别．由此根据凝固过程收缩发生的区域，准确地进行缩孔缩松的预测．可有效地解决凝固过程中同时存在任意多个孤立补缩域的缩孔缩松预测，解决了凝固过程数值模拟中常出现的位置较低的侧暗冒口或铸件中可能出现的缩孔不能被正确预测的技术难题．     

铸件凝固模拟液态孤立多熔池动态判定及缩孔预测

预测缩孔缺陷产生是铸件凝固模拟的主要目的。研究铸件凝固模拟液态孤立多熔池动态判定方法及缩孔预测模型，实验证明该方法可以提高铸件模拟缩孔预测精度。     

一种新的基于FDM/FEM挤压铸造收缩缺陷计算模型

根据挤压铸造的凝固特点,采用高阶导热偏微分方程有限差分计算模型(FDM格式)进行温度场数值模拟,使用动态孤立多熔池判定法确定熔池位置,采用FEM进行熔池中心位置压力计算。若熔池中心位置的压力已经降至0,封闭在硬壳内的液态金属将在没有压力作用的情况下凝固,并按照重力补缩方式进行补缩。采用孤立熔池等效液面下降法来预测收缩缺陷的形成,模拟结果与实验结果基本吻合。     

链轮铸造工艺设计及改进

利用ViewCast软件对链轮铸钢件的凝固过程进行了数值模拟,预测了缩孔、缩松缺陷产生的位置.分析了原因.在此基础上设计了链轮的初步铸造工艺,进行模拟,通过添加冒口、冷铁,进行工艺优化,最后获得合适的工艺方案.     

旋回破碎机上机架厚大部位缩孔与缩松的模拟

针对大型铸钢件旋回破碎机上机架铸造生产过程中存在的缺陷问题,利用Pro CAST模拟软件中临界固相率对厚大部位的凝固过程进行模拟分析,从而判断出缩孔产生的热节区位置;同时基于Niyama判据预测了冒口补缩区域缩松缺陷的产生。在此基础上,修改原工艺设计方案,即将原设计的一个暗冒口改为两个对称分布的暗边冒口。模拟结果表明,改进后的工艺满足顺序凝固条件,消除了孤立的热节区域,Niyama判据满足不形成缩松的临界值要求,避免了缩孔缺陷的产生。模拟实验与实际生产吻合较好。     

TiAl合金精密铸件缩孔的定量预测

研究了TiAl合金叶片铸件液态熔池孤立区形成的判定方法及缩孔的预测模型，对缩孔形成过程进行了模拟显示。研究表明，利用这种方法模拟缩孔缺陷可以提高铸件模拟缩孔预测精度。     

凝固模拟技术在铸钢件上的应用

通过在东方电机厂铸钢件上应用铸造充型凝固过程数值模拟商品化软件ＦＴ－ＳＴＡＲ,一方面帮助工厂预测大型铸钢件的缩孔缩松缺陷,给工厂提供技术支持为优化铸钢件铸造工艺提供科学依据,使工厂节约开支并取得经济效益;另一方面在应用中又发现软件的一些不足之外,进行分析改进,促进了铸造充型凝固技术的持续发展。     

铸钢件缩孔形成的三维定量模拟

本文提出了一种新的三维定量模拟铸钢件缩孔形成的方法。用有限差分法进行传热计算，用温度回升法和等价比热法处理由于相变放出的潜热。在传热计算的基础上采用等效液面下降法预测缩孔的形成．在微机上对实际铸件进行了模拟并与现场实际解剖的铸件进行对比，结果表明，运用本方法可以准确地预测铸钢件中缩孔的位置、体积和形状。     

汽轮机阀体铸造凝固过程数值模拟及缩孔、缩松的预测

在分析了铸件凝固过程结晶潜热释放和缩孔、缩松形成条件后,应用数值模拟软件模拟了砂芯铸造汽轮机阀体的凝固过程,得到阀体铸件凝固的温度梯度分布,并预测了铸件出现缩松、缩孔缺陷的部位。在此基础上,对铸件凝固过程进行了阐述。数值模拟结果可供阀体铸造工艺设计参考。     

胫骨生物陶瓷复合材料的微结构增韧机理

扫描电镜观察显示胫骨是一种由羟基磷灰石和胶原蛋白组成的自然生物陶瓷复合材料.羟基磷灰石具有层状的微结构并且平行于骨的表面排列.观察也显示这些羟基磷灰石层又是由许多羟基磷灰石片所组成,这些羟基磷灰石片具有长而薄的形状,也以平行的方式整齐排列.基于在胫骨中观察到的羟基磷灰石片的微结构特征,通过微结构模型分析及实验,研究了羟基磷灰石片平行排列微结构的最大拔出能.结果表明,羟基磷灰石片长而薄的形状以及平行排列方式增加了其最大拔出能,进而提高了骨的断裂韧性.     

Prospects of the Use of Synergetic Approach to Solution of Problems of the Science of Nanomaterials

A synergetic approach to solution of problems of self-controlled synthesis of nanostructures and creation of self-organizing nanotechnologies is considered in connection with the superproblem of creation of materials with functional properties resembling those of biosystems. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 7, pp. 55 – 61, July, 2005.     

Kinetics of the oxidation of metals — Influence of self-diffusion of metal

The importance of the self-diffusion of a metal during its oxidation by a gas is treated for the cases of nonstoichiometric oxides having either interstitial cation or cation vacancies. We have established a general relationship for the reaction rate when a mixed diffusion process occurs. From this relationship, we have shown that the pressure dependence can be different, according to whether the rate-determining process is the self-diffusion through the metal or through the product.     

Features of formation of the structure in production of blanks of disks of heat-resistant nickel alloys

Conclusions To provide a high level of mechanical properties in wrought blanks of cast ÉP741NP and ÉP962 alloys it is necessary to form controlled structures. A necklace-type structure formed in homogenizing isostatic treatment, subsequent thermomechanical working including alternation of the operations of deformation in the (+)-area and recrystallization anneals, and final heat treatment is preferable. The temperature conditions of all stages of thermomechanical working are strictly controlled, especially the final operation of deformation and heating for hardening. To eliminate hardening cracks and distortions it is necessary to use molten salts at t=600°C as quenchants. The use of multiple production operations makes it possible to significantly reduce the structural inhomogeneity related to inhertance of the original dendritic structure. However, the structure of the final semifinished product is nevertheless characterized by a difference in occurrence of the processes of polygonization and recrystallization between the former dendritic cells and the interdendritic spaces in deformation and heat treatment.To obtain structurally homogeneous blanks for gas turbine engine parts it is necessary to use basically new methods of remelting such as vacuum double electrode remelting and electron beam remelting with an intermediate vessel.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 12, pp. 25–29, December, 1991.     

Ab-initio calculation of enthalpies of formation of intermetallic compounds and enthalpies of mixing of solid solutions

A large number of ab-initio calculations of energies of formation of intermetallic compounds have been performed in the last 15 years. The currently used methods are listed. The paper presents a review of the aluminium based compounds which have been studied. Comparisons of calculated and experimental enthalpies of formation are provided for aluminim-3d and-4d transition metal alloys at equiatomic composition. The modelling of the enthalpies of mixing of solid solutions based on a given lattice is described.     

试论洋务派教师聘任的思想

洋务派在洋务学堂的办学活动中,为了解决西学专业学科的教学困难,采用了聘请外籍教师的应急措施.他们以真才实学,合同制管理作为主导思想,并认为这种解决师资的途径只是权宜之计,并非久远.从客观上看,洋务派的教师聘任思想有深刻的历史影响.