Measurable solutions for elliptic inclusions and quasistatic problems

This work establishes the existence of variational solutions and their measurability to a very broad class of elliptic variational inequalities or set-inclusions under very general assumptions on the operators and the forcing functions and on their measurability. These results extend the current existence results for such problems and so the existence results are new, and so are the results when randomness is added. Moreover, it presents new measurability theorems when the operators and forcing functions are random processes. As an important application of the general existence result, it presents existence results for quasistatic problems in which the main operator is elliptic and time enters as a parameter or through dependence on auxiliary variables.     

Modelling inclusion evolution in Al–Ti-killed steels during ladle mixing process

A reaction model was developed to better understand the evolution of inclusions in Al–Ti-killed steels during the ladle mixing process. The fluctuation of steel chemistry gave rise to the transient evolution of inclusions during the mixing process. The formed Al₂O₃ in the steel can be hardly influenced by the addition of FeTi, while adding Al can effectively modify the TiO_x-containing oxides to solid Al₂O₃. The formation of Al₂O₃–TiO_x inclusions can be suppressed by increasing Al and lowering Ti in the steel. The alloying sequence of adding Ti after the Al addition is beneficial to improve the recovery of Ti. The one-point strong air absorption may cause the formation of the unwanted Al₂O₃–TiO_x inclusions in Al–Ti-killed steels. The critical oxygen contents in the molten steel with varying Al and Ti concentrations were predicted to avoid the formation of Al₂O₃–TiO_x inclusions and Ti loss.     

芙蓉石内纤维状包裹体的研究现状

国内将粉色的水晶统称为芙蓉石,国外学者提出粉色的水晶可分为两类:粉石英和蔷薇石英,以晶形、颜色稳定性、包裹体等因素区分,其中无晶形、内部大量纤维状包裹体的蔷薇石英较为常见,可认为市面上见到的成品芙蓉石均为蔷薇石英.本文阐述了近年来国内外学者对芙蓉石的研究,客观地总结了对其内部包裹体的研究现状.金红石常作为包裹体出现在水晶中,芙蓉石内的针状、纤维状包裹体也被认为是金红石,但近年来的研究显示,包裹体的谱线匹配为蓝线石或类似物,并非金红石;不同的观察手段显示包裹体不同的分布特征和对称程度,指向不同的形成原因——先成或出溶,与六射星光的位置关系有待确定;另有学者通过实验证明,粉色纤维状包裹体对芙蓉石的颜色有明显贡献,且未发现经常被归为致色成因的色心及Ti/Mn元素.因而可认为,芙蓉石内部的纤维状包裹体为粉色蓝线石,遍布整体的包裹体造成了星光及粉色,但包裹体与星光的位置关系及成因有待后续研究.     

U-Nb合金中夹杂物的纳米压痕表征

采用纳米压痕技术对铸态U-5.5Nb合金中Nb_2C、U(C,N)以及基体力学性能进行了表征,根据获得的硬度值计算了屈服强度和塑性指数。实验结果表明Nb_2C夹杂物的弹性模量和硬度最大,而U(C,N)夹杂物的弹性模量和硬度远小于Nb_2C但明显高于基体;计算结果显示Nb_2C夹杂物屈服强度最高而塑性指数值最小,倾向于发生弹性变形,U(C,N)夹杂物强度低但塑性指数值最大,更容易发生塑性变形并发生破裂。基体多步循环加载获得的弹性模量和硬度值与单次加载基本一致,并且弹性模量值和文献中报道的单向拉伸实验测得的值相符。     

江西永平铜矿成矿物质来源及矿床成因分析

永平铜矿产于断裂坳陷带中,明显受地层控制。从包裹体特征,硫、氢氧、铅同位素、稀土组成、黄铁矿中Fe、S的组成,围岩含矿性对比等结果可以看出,其成矿物质的主要来源是火山喷流作用带来的深部物质。综合其它的成矿特征,得出永平铜矿的成矿模式：海底火山喷流沉积一混合岩化、动力改造一岩浆热液叠加改造型。     

锻件内部脆性夹杂物边界无裂纹形成的应力条件

大型锻件内部脆性夹杂物边界裂纹是影响大型锻件疲劳寿命与冲击性能的主要缺陷。热锻变形下,脆性夹杂物周围区域的应力场是影响边界裂纹形成的主要因素之一。为研究应力场的影响,给出了平均球应力度的定义,借助平均球应力度研究了应力场对脆性夹杂物边界裂纹的影响规律。在Gleeble．3180热模拟试验机上,利用专门的试件和型砧进行了热压缩变形试验,在扫描电镜上观察试件内部脆性夹杂物边界裂纹的形成规律。试验表明,在1220℃进行压缩变形的条件下,当脆性夹杂物周围区域的平均球应力度的代数值小于-1．74时,脆性夹杂物边界无裂纹形成。     

电磁搅拌对液态夹杂物聚并及去除行为的影响规律

高拉速连铸具有高效、低成本的特点,是未来连铸的发展方向。以常规板坯结晶器为研究对象,基于大涡模拟理论及欧拉-拉格朗日方法,对CSP结晶器内的多相流动及夹杂物碰撞聚并及去除行为展开深入分析。结果表明,电磁搅拌加剧了钢液在结晶器中的湍流强度,并促使更多夹杂物聚并上浮至渣金界面。并且,由于水平方向流速较大,钢液射流被限制在了电磁搅拌区域,显著降低了钢液射流深度,有利于夹杂物上浮。此外,由于电磁力的存在加剧了渣金界面波动,容易造成卷渣,因此,电磁搅拌对夹杂物的去除影响是双向的,既会提升内生夹杂物去除率,也会增加外来夹杂物的卷入风险。本模型对控制CSP结晶器连铸过程具有一定指导意义。