Prediction models for the key mechanical properties of EPDM/PP blends as affected by processing parameters and their correlation with stress relaxation and phase morphologies

The optimum condition of processing parameters (mixing temperature, rotor speed, fill factor, and blend ratio) and prediction models for the best key mechanical properties of ethylene propylene diene terpolymer/polypropylene thermoplastic vulcanizates (EPDM/PP TPVs) was investigated by using the Taguchi's optimization technique and data analysis. The results reveal that all of the processing parameters affected significantly the mechanical properties of the EPDM/PP TPVs, but specifically the blend ratio contributed more than 90% in effect size on tensile strength and tension set. There were three main factors, the mixing temperature, the fill factor, and the blend ratio, influencing the elongation at break. Furthermore, the mathematic models were effective and reliable in predicting the properties of TPVs. The correlation of mechanical properties, stress relaxation, and phase morphologies of the TPVs prepared from the predicted models was also investigated. It can be summarized that the morphological structure and stress relaxation of the TPVs were strongly governed by the EPDM content in the blend ratio. That is, the higher the EPDM content, the better phase morphology having smaller size of the vulcanized EPDM particles distributed in the PP matrix and the higher rate of stress relaxation. Moreover, these two properties were then principally pushing the mechanical characteristics of the EPDM/PP TPVs. Copyright © 2015 John Wiley & Sons, Ltd.     

Shear dependence of viscosity for perfluoropolyether fluids

The shear dependence of the bulk viscosities of two structurally different types of perfluoropolyether fluids was determined by two different techniques. The first involved direct measurement in a high shear Couette viscometer, the second utilized the time-temperature superposition principle to establish master curves from viscosity determinations at low shear rates and temperature; the results are comparable. Both fluids begin to show non-Newtonian behavior at shear rates above 10,000 s^–1.     

微电子元件制造过程中的应力分析

本文分析了一个典型的微电子元件在创造过程中残余应力的分布和演化．与以往大多数类似的分析工作的不同之处在于，我们并不是对一个已成型的结构再回过头去仅仅分析其温度历史下相应的应力状态，而是追踪了该结构成型过程的各个方面，尤其是由于工艺过程中结构几何形状的变化而引起的应力重分布．采用的方法则是控制某些材料所对应的单元在某一特定的时刻以后才起作用，这种方法对于各种制造过程的分析非常有效．     

横观各向同性体应力波传播问题的特征分析

本文根据广义特征理论,对横观各向同性体轴对称弹性波传播问题进行了理论分析。提出了一个简化特征分析的方法,这种方法将成为应用特征线法求解各类各向异性应力波问题的一个突破口。     

复合材料层板边缘效应的准相似元解法

用准相似单元法研究了复合材料层板直边和孔边的自由边缘效应，得到了一些具有工程意义的结果。准相似单元法是相似单元法的推广，利用这一方法可以求解三维的应力集中问题，避免了求单刚时的重复计算。由于采用了按相似层求解的技术，应用准相似单元法求解应力集中问题时对计算机容量的要求大为降低     

Raman imaging and stress quantification in self‐assembled graphene oxide fiber ‘Latin Letters’

To probe the intrinsic stress distribution in terms of spatial Raman shift (ω) and change in the phonon linewidth (Γ), here we analyze self‐assembled graphene oxide fibers (GOF) ‘Latin letters’ by confocal Raman spectroscopy. The self‐assembly of GOF ‘Latin letters’ has been explained through surface tension, π–π stacking, van der Waals interaction at the air–water interface and by systematic time‐dependent investigation using field emission scanning electron microscopy analysis. Intrinsic residual stress due to structural joints and bending is playing a distinct role affecting the E_2g mode (G band) at and away from the physical interface of GOF segments with broadening of phonon linewidth, indicating prominent phonon softening. Linescan across an interface of the GOF ‘letters’ reveals Raman shift to lower wavenumber in all cases but more so in ‘Z’ fiber exhibiting a broader region. Furthermore, intrinsic stress homogeneity is observed for ‘G’ fiber distributed throughout its curvature with negligible shift corresponding to E_2g mode vibration. This article demonstrates the significance of morphology in stress distribution across the self‐assembled and ‘smart‐integrable’ GOF ‘Latin letters’. Copyright © 2016 John Wiley & Sons, Ltd.     

考虑横向剪切变形的扁球壳在集中力作用下的分析

采用适于夹层壳的直线假设扁壳理论，应用三角级数法，导出了扁球壳齐次方程的解析解。进而分析了在顶点作用法向集中力和在偏心集中力作用下的解。计算了在偏心集中力作用下带孔球壳的位移和应力，并将结果与经典理论的结果进行了比较分析，结果表明，在集中力作用处和孔边处两种理论结果明显不同。     

正交复合材料面层夹层板非线性理论及应用

针对复合材料面层夹层板的构造和变形特点，考虑横向剪应力在面层和芯层粘结处的连续条件，应用Ｈａｍｉｌｔｏｎ原理建立了基于五个未知函数的正交铺设复合材料面层夹层板的非线性精化理论。对静力学问题，控制方程化简为由四个基本未知函数表述。文中还分析了简支正交铺设复合材料面层夹层板的非线性弯曲，给出了载荷—挠度特征关系和板中应力的分布状况。数值计算表明，夹层板面层和芯层粘结处的层间剪应力在工程设计中是十分重要的。