单轴压缩条件下破裂岩样声发射及能耗特性试验研究

为揭示岩石变形破裂的内在机理及正确评价工程破裂岩体的特性,本文对破裂岩石再破裂过程声发射、能耗特性进行了综合研究。借助MTS伺服试验机及AE21C声发射检测仪,对破裂岩样进行了单轴压缩条件下再破裂过程中的声发射及能耗特性实验研究。研究结果表明:破裂岩样声发射事件-时间曲线主要属于峰前阶段加速增长型,其声发射事件-时间曲线大致可分为声发射初始发展、剧烈、降低三个阶段;在整个压缩破裂过程中,声发射活跃程度总体上大于相对完整岩样;峰值点是声发射特征、能耗特征的转折点;岩样变形破裂过程中,声发射与能耗指标之间存在内在的、必然联系;随着破裂程度的提高,破裂岩样峰值点吸收能量与峰前段耗散能量均逐步降低;破裂岩样表面破裂面分布分形维数同峰值点吸收能量与峰前段耗散能量之间总体上均遵循非线性的二次多项式函数关系。     

加载角度和线型缺口对锂离子电池隔膜拉伸性能的影响

锂离子电池隔膜作为防止正负极接触的物理屏障,其结构完整性对于电池安全至关重要。进行了4种商业隔膜单轴拉伸实验,分析加载角度和线型缺口对隔膜材料拉伸强度、弹性模量、断裂模式的影响。结果表明:无缺口试样在0°方向上的拉伸强度最大,90°方向上拉伸强度最小;当两个无缺口试样的加载角度互为补角时,它们的拉伸强度接近。对于缺口试样而言,缺口方向沿着90°的试样有最大破坏载荷;线型缺口试样有更高的弹性模量,但是塑性变形大幅减少。无缺口试样和缺口试样在拉伸过程中的断裂模式相同,即除0°试样沿横向断裂外,其他加载角度的试样均沿着纵向断裂。     

Dehnviskosität von Kautschukmischungen

It is shown that the extensional viscosity measured by uniaxial stretch may give useful information as to the processability of rubber compounds. A simple apparatus was constructed to measure this rheological property at constant rate of strain. The influence of rubber type, filler, aging, mastication and degree of crosslinking on the reduced stress is represented by diagrams. No steady-state extensional viscosity was obtained for highly filled rubber compounds. It was found that the flow behaviour of rubber compounds can be better characterized with an extensional rheometer than with a high-pressure capillary rheometer.

     

单轴晶体Ⅰ类相位匹配时的转换效率分析

在考虑了二次谐波的吸收对转换效率影响的情况下,由光在介质中的波动方程,推导出负单轴晶体Ⅰ类相位匹配时平面二次谐波的耦合波方程和二次谐波转换效率的理论公式。在此基础上,再考虑走离效应的影响,给出了二次谐波转换效率的理论公式。根据这些公式,以负单轴晶体K2Al2B2O7（KABO）为例,对二次谐波的转换效率进行了数值计算。结果表明：考虑二次谐波的吸收时,存在倍频晶体长度的最佳值,当倍频晶体取该值时,二次谐波的转换效率最高;走离效应的存在使二次谐波的转换效率降低。     

“Foil spintrusion” of high-performance polymer films

This article describes the development of high-performance polymer foils by direct orientation in the liquid-crystalline phase of a thermotropic copolyester, based on p-hydroxybenzoic acid (HBA) and 2-hydroxy-6-naphthoic acid (HNA), better known under the trade name Vectra®. Application of a simple air-gap-filament-fusion-extrusion process (“foil spintrusion”) with the use of a newly developed die, results in highly oriented free-standing foils, as thin as 3 μm. These foils have a mechanical performance that is comparable with those of commercially produced fibers of the same material. These uniaxially oriented foils could be laminated upon hot-compacting without, or with as little as 5 wt % of an adhesive, yielding planar foils as thin as 18 μm, which feature excellent isotropic, in-plane mechanical properties, that is, a Young's modulus E = 20 GPa and a tensile strength σ = 0.5 GPa. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Validation of Equations Suggested for the Elastic Behaviour of Powders

A new equation for the relationship between elastic stress and strain for powders, based on Hooke's law has been described in a recent article [1]. The equation will here be validated by least mean square curve fitting on experimental measurements obtained by cyclic consolidation of powders in a uniaxial tester. The validation shows that the derived equation fits quite well to the unloading of the tested powders, whereas the reloading has a more linear relationship.     

Optical order of the polymer phase within polymer/fullerene blend films

This study reports on how the degree of polymer order within a polymer/fullerene blend can be investigated by spectroscopic methods. Non‐annealed blend compositions with 0–80 wt % fullerene content were analyzed using temperature dependent photoluminescence (PL) and room temperature spectroscopic ellipsometry (SE) measurements. To evaluate the SE data with respect to the optical order, an optical model was developed, including a lower and higher ordered polymer phase within a fullerene matrix. This was done using an effective medium approach describing the polymer by combining lower and higher ordered polymer properties (polymer‐EMA). The polymer/fullerene blend was then evaluated using another EMA consisting of the polymer‐EMA and the dielectric function of the disordered fullerene. The degree of optical order obtained by SE, was confirmed using another independent measurement, photoluminescence spectroscopy, according to the method of Francis C. Spano (2005). The volume fraction of the ordered polymer within the polymer‐EMA was found to be between 70 and 60 vol % for fullerene contents lower than 20 wt % in the polymer/fullerene blend. Above 20 wt % fullerene, the optical order of the polymer strongly decreases all the way down to 0 vol %. In contrast to the complementary performed X‐ray diffraction measurements, which address only the long‐range structural order of the blends, we give quantitative information on the optical order, including information on the composition, that is, volume fractions of the higher and lower ordered polymer. The gained information on the tilt of the polymer molecules with respect to the substrate is discussed comparing XRD results from the literature with those obtained by our SE model. Finally, the developed model is used to describe the influence of the P3HT molecular weight on the optical order. Results obtained with our model were compared to the structural data and mobility data in the literature. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

X‐ray diffraction from the uniaxial and biaxial nematic phases of bent‐core mesogens

X‐ray diffraction patterns for the uniaxial and biaxial nematic phases exhibited by rigid bent‐core mesogens were calculated using a simple model for the molecular form factor and a modified Lorentzian structure factor. The X‐ray diffraction patterns depend strongly on the extent of the alignment of the molecular axes as well as the orientation of molecular planes. The X‐ray diffraction can be unequivocally used to identify the biaxial nematic phase, study the uniaxial–biaxial phase transition, and estimate the order parameters of the nematic phase.