层状岩体的Cosserat介质均匀化

将层状岩体视为由Cosserat介质组成的复合体,对其进行均匀化等效,在MATLAB平台上进行有限元编程,得到新等效本构关系。不仅能反映层状岩体的弯曲特性,而且可以对节理岩体的力学性能进行宏观和细观描述。通过对洞室算例进行显式节理模型、横观各向同性模型以及均匀化Cosserat等效模型三种方法的数值计算比较,证明理论分析与计算方法可行有效。     

涡轮叶片蠕变全过程的修正Graham模型的参数识别

针对定向凝固镍基合金制造的航空发动机涡轮叶片,从涡轮叶片典型部位取材并设计制造模拟试件,在980℃下不同应力水平下进行单轴蠕变试验。对试验数据进行了唯象学的数学描述,并对ANSYS有限元分析软件中Graham蠕变模型进行了修正,使修正后的模型能够比较精确地描述单轴蠕变的全过程。并应用修正Graham模型对试验过程进行数值模拟,研究表明ANSYS有限元模拟蠕变的结果和试验数据吻合较好。这说明了修正Graham模型模拟单轴蠕变过程的合理性,该模型在一定程度上为ANSYS在金属材料蠕变分析方面的二次开发提供了理论基础。     

A node-to-surface linear complementarity problem approach for general three-dimensional contact analysis

Meccanica - Contact between two deformable bodies is a complex nonlinear problem especially when rigid-body motion and geometric errors of components are taken into consideration. In this paper, an...     

Preparation and catalytic activity of P4VP–Cu(II) complex supported on silica gel

Micron-sized silica gel particles were chemically modified on their surfaces with the coupling agent, γ-methacryloxypropyl trimethoxysilane (MPS), double bond was introduced onto the surfaces of silica gel particles, and the modified particles MPS–SiO₂ were obtained. Then, poly(4-vinylpyridine) (P4VP) was grafted from the silica gel surfaces, and grafting particles P4VP/SiO₂ was prepared. Finally, the coordination between grafted P4VP and cupric ions Cu²⁺ was performed, and the supported complex Cu(II)–P4VP/SiO₂ was obtained. The grafting particles P4VP/SiO₂ and the supported complex Cu(II)–P4VP/SiO₂ were characterized with infrared spectra (FTIR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Cu(II)–P4VP/SiO₂ was used as a catalyst for the oxidation of ethyl benzene into acetophenone with molecular oxygen under ordinary pressure. The experimental results show that the supported complex Cu(II)–P4VP/SiO₂ can be successfully prepared via grafting polymerization of 4VP and coordination between the grafted P4VP and cupric ions Cu²⁺. In oxidation of ethyl benzene into acetophenone by molecular oxygen under ordinary pressure, the supported complex Cu(II)–P4VP/SiO₂ displayed high catalytic activity and excellent catalytic selectivity up to more than 98% for the transformation of ethyl benzene to acetophenone.     

Studies on rheological behaviour of hydrophobically associating polyacrylamide with strong positive salinity sensitivity

Hydrophobically associating polymer has been obtained by homogeneous copolymerization of acrylamide and an anionic surface-active monomers (surfmer) of acrylamide-type, sodium 2-acrylamido-tetradecane sulfonate (NaAMC₁₄S) in aqueous solution, and under different concentration conditions of NaAMC₁₄S above its critical micellar concentration (CMC) and below CMC, two structure types of copolymers P (AM–NaAMC₁₄S) were prepared in which main chains NaAMC₁₄S were distributed in microblock and in random manner, respectively. The hydrophobically associating property and rheological behaviour of the copolymers were studied with viscosimetry and then by fluorescence probe method. It was found that the apparent viscosity of the aqueous solution of the copolymers with microblock structures exhibits strong positive salinity sensitivity, whereas the positive salinity sensitivity of the apparent viscosity of the aqueous solution of the copolymers with random structure only appears generally and the apparent viscosity was diminutively increased because of salinity-promoting hydrophobic association. For those copolymers with microblock structures, the apparent viscosities of their brine solution are much higher than that of their pure water solution. In CaCl₂ solution (2 wt%), as the copolymer concentration attains 0.2 wt%, the apparent viscosity enhances dramatically with the increase in concentrations, and as the copolymer concentration was 0.3 wt%, the apparent viscosity can enhance by almost two orders of magnitude (from 32 to 1,000 mPa·s) as compared with in pure water solution. Thus, for copolymer P (AM–NaAMC₁₄S) with microblock structure, the peculiar positive salinity sensitivity, i.e. salinity thickening, is displayed distinctly. The unusual positive salinity sensitivity of copolymers P (AM–NaAMC₁₄S) with microblock structure was also revealed by fluorescence probe method, and the value I ₁/I ₃ of pyrene in the brine solution of the copolymers was smaller than that in pure water solution of the copolymers. This unique salinity sensitivity is a reflection of the unusual microstructure of the copolymers. The experiment results are interpreted in terms of the effects of the surfmer distribution manner in the copolymer main chain and bonding way of the ionic surfmer to the copolymer main chain on the forming intermolecular association.     

电感耦合等离子体原子发射光谱(ICP-AES)法测定车用尿素水溶液中的8种杂质元素含量

将1g尿素水溶液样品置于烘箱105℃下浓缩,在1 100℃马弗炉中加热灰化;取出冷却,使用盐酸(1+1)溶解灰分。采用Al 237.312nm、Ca 393.366nm、Cr 267.716nm、Cu 324.754nm、Fe 238.204nm、Mg 279.553nm、Ni 231.604nm、Zn 213.856nm作为分析线,建立了使用电感耦合等离子体原子发射光谱(ICP-AES)法测定尿素水溶液中铝、钙、铬、铜、铁、镁、镍和锌8种杂质元素的方法。结果表明,铝、钙、铬、铜、铁、镁、镍和锌的线性范围在0.02~2μg/mL时,校准曲线的线性相关系数均不小于0.999 5;方法中各元素的检出限为0.001~0.010μg/mL。将方法应用于尿素水溶液样品中8种杂质元素的测定,结果的相对标准偏差(RSD,n=7)均小于5.0%,加标回收率为91%~108%。方法可一次性完成对多种元素的测定,准确度、精密度较高,方法简便快速,适用于各级检验机构进行多批次、多项目产品的元素检测。     

丙烯酰胺型阴离子表面活性单体与丙烯酰胺共聚物水溶液的流变特性

以丙烯酰胺型阴离子表面活性单体2-丙烯酰胺基十四烷基磺酸钠(NaAMC14S)为共单体,与丙烯酰胺(AM)的水溶液均相共聚合,使NaAMC14S的浓度分别处于临界胶束浓度上下,分别制备了具有无规结构与微嵌段结构的两类共聚物;用红外光谱法对共聚物的结构进行了表征,使用乌氏粘度法测定了特性粘数,相对表示出了共聚物的分子量;采用荧光探针法与表观粘度法重点研究了两类共聚物的疏水缔合性与水溶液的流变特性.研究结果表明,具有微嵌段结构的共聚物具有很强的疏水缔合性,当其水溶液的浓度达0.2wt%后,表观粘度迅速提高;其水溶液的切力变稀行为具有明显的可逆性,表现出强的抗剪切性能.本研究中特别发现,具有微嵌段结构的共聚物其盐水溶液的表观粘度远高于纯水溶液的表观粘度,当共聚物浓度为0.3wt%、CaCl2浓度为2wt%时,溶液的表观粘度竟然提高了3个数量级,表现出独特的正性盐敏性(即遇盐变稠).