稀土丁异戊橡胶改性天然橡胶的应用研究

采用稀土丁异戊橡胶代替顺丁橡胶，测试并分析了改性天然橡胶的低温性能及相关性能。结果表明，稀土丁异戊橡胶改性的天然橡胶室强力学性能和粘接性能与顺丁橡胶改性的天然橡胶相近，但低温性能有较大的改善。在-40℃下贮存2h后，顶丁橡胶改性天然橡胶硫化胶有明显的结晶现象，其剪切模量较室温下的相应值增加了6倍，而稀土丁异戊橡胶改性的天然橡胶硫化胶保持了良好的弹性，其剪切模量值与室温下的相当。     

Failure load prediction of structural adhesive joints : Part 2: Experimental study

The objective of this study was to determine how the fracture of adhesive joints depends on elastic beam parameters describing the adherends and the applied loads. The basic specimen geometry was the cracked lap shear joint constructed of aluminium alloy with various adherend and bondline thicknesses. Loads were applied in different combinations of bending, tension and shear to generate a failure envelope for each adhesive and specimen geometry. It was found that crack propagation for precracked specimens occured at a critical strain energy release rate but was also a function of the G_I/G_II ratio and the bondline thickness. The experiments also showed that the loads required to propagate a crack in a precracked specimen were always lower than the loads required to break the fillet. Hence, by treating uncracked joints as being cracked, where the fictitious crack tip is assumed to coincide with the location of the fillet, a conservative estimate of the failure load is obtained.     

Shear Strength of Pressure Sensitive Adhesives and its Correlation to Mechanical Properties

Correlations between shear resistance and the mechanical properties of pressure sensitive adhesives are studied by measuring the deformation behaviour in the static and the dynamic shear test and determining the dynamic shear modulus of the adhesive. For polymers with low or moderate viscosities, the shear strain vs. time characteristics in a static shear test and, accordingly, the static shear strength, can be evaluated from the master curves of the dynamic shear modulus or the dynamic viscosity. The dynamic shear strength also can be calculated. These exact calculations cannot be applied to highly viscous or slightly crosslinked polymers. On the basis of the model experiments, empirical correlations between shear strength and the dynamic shear modulus are established which seem to be generally valid.     

纳米蒙脱土/环氧树脂胶粘剂制备工艺优化选择

介绍了制备纳米蒙脱土/环氧树脂胶粘剂的方法,并通过正交试验的方法分析了固化时间、固化温度、搅拌时间、搅拌温度对纳米蒙脱土/环氧树脂胶粘涂层拉伸剪切强度的影响,给出了上述四个工艺参数的最佳工艺规范并通过试验验证了结论。     

用三维实体单元分析薄壁箱型结构应注意的问题

从四边固定正方形板受均布载荷的经典问题入手,结合不同类型单元的特点,探讨应用三维实体单元分析薄壁箱型结构时应注意的几个问题,纠正三维实体单元分析和应用的误区,为提高结构分析计算结果精度提供参考.     

A型地铁空调系统及客室内流场数值分析

为给目前国内A型地铁车辆的舒适度设计提供理论参考,针对地铁车辆静压风道结构特点,基于k-ε两方程湍流模型和SIMPLE算法,建立包含空调送风风道和客室的三维计算模型.对计算模型的空气流动和传热状况进行CFD数值计算.计算过程综合考虑车体壁面传热和人体散热等多种传热.分析计算结果得到客室内温度场和速度场的分布规律,并对空调通风设计方案进行量化评估.计算结果表明:客室内人体头部区域温度场分布均匀,平均温度为26.6℃,最大温差为6℃;车厢内有较理想的气流组织形式,速度分布范围为0.50~0.79 m/s,而且客室端部和中部区域人体头部周围速度较大.将计算结果与欧洲EN 14750-1标准进行对比分析,认为乘客的舒适性较好.     

保护胶体稳定的丙烯酸酯乳液流变性

分别采用常规乳化剂和羟乙基纤维素为保护胶体制备丙烯酸酯乳液。通过TEM分别观察乳胶粒的形态。利用流变仪测定剪切速率（Ds）-剪切应力（τ）关系、剪切速率（Ds）-黏度（η）关系。结果表明：采用羟乙基纤维素为保护胶体制备的乳液与常规乳液具有不同结构，该结构使其乳液体系流变性能不同。在相同剪切速率下，保护胶体制备的丙烯酸酯乳液的剪切力明显大于常规乳液的剪切力，该乳液在一定剪切速率范围内有剪切稀化现象。     

自清洁外墙涂料的研究与应用

如何提高外墙涂料的自清洁能力,并使之保持较长的装饰效果一直是涂料界关注的热点。本文综述了微粉化技术、荷叶效应、气球陶瓷理论、自分层技术以及光催化效应的原理,及其在改善外墙涂料自清洁性方面的应用。     

ESTIMATION OF EFFECTIVE SHEAR RATE FOR AERATED NON-NEWTONIAN LIQUIDS IN AIRLIFT BIOREACTOR”“

Effective shear rate is one of the indispensable parameters for the design of aerobic fermentors using a viscous non-Newtonian system. The estimation of effective shear rate in airlift loop bioreactors has been investigated with liquid circulation velocity. An empirical correlation of effective shear rate in airlift loop reactors is proposed.

γ_eπ= 3.26-3.51 ; 10²U_G + 1.48 10⁴U²_G

It is found that the effective shear rate is lower in airlift reactors than in bubble columns. This equation can be used for the cultivation of cells sensitive to shear stress.     

Short‐beam three‐point bend test study in syntactic foam. Part III: Effects of interface modification on strength and fractographic features

Syntactic foam slabs having uncoated microballoons and paraffin oil surface‐treated microballoons were fabricated and tested for short‐beam three‐point bend test. The work points to the role of paraffin oil coating first weakening the interface between the microballoons and the matrix and hence lowering the efficiency of load transfer from matrix to the fillers (i.e., microballoons). This led to an overall decrement of 71% in the experimentally measured strength value compared to the deduced value for uncoated microballoons' specimens. The large strengths for uncoated microballoons specimens can be traced to the presence of the curvilinear marks in the matrix that, incidentally, are absent in the case of paraffin oil coated specimens. These observations are revealed distinctly in the microscopy of test‐failed specimens. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 687–693, 2005