Micromechanical characterisation of fibre/matrix interfaces

Theoretical analyses for the single fibre pull-out and push-out models under monotonic loading are given which are based on a shear-lag analysis in a fracture mechanics approach considering non-constant friction at the debonded interface as a result of fibre Poisson contraction (or expansion). The solutions allow the determination of typical fibre/matrix interfacial properties such as the interfacial fracture toughness, G_ic, the coefficient of friction, μ, and the residual clamping stress, q₀. Under cyclic loading the interfacial properties are expected to degrade as a result of repetitive abrasion, and a power law function is assumed between μ and the number of elapsed cycles, N. However, G_ic is assumed to be unaffected and a fracture mechanics based debond criterion is derived for the relationship between the external applied stress, the debond length and the reduced friction coefficient for both fibre pull-out and fibre push-out. In addition, the relative displacements between the free fibre end and the matrix top are obtained for cyclic fatigue when the fibre is loaded and unloaded. A relationship obtained for the protrusion (or intrusion) length in fibre pull-out (or push-out) experiments allows the severity of the interface frictional degradation to be evaluated and characterised. Similarities and differences in the frictional degradation behaviour between fibre pull-out and push-out are also identified.     

廉价石油磺酸盐表面活性剂KPS-2的合成及性能

在室内合成出了驱油用廉价石油磺酸盐表面活性剂KPS-2,确定了KPS-2的生产工艺参数,并对产品性能进行了评价.实验表明:KPS-2/Na₂CO₃复合体系与新疆克拉玛依原油的界面张力达到了三元复合驱低界面张力的要求,且新产品KPS-2具有适应范围广,产品收率高,产品性能稳定,生产工艺简单,无酸渣,环境污染小,成本低等特点.     

汉白玉废料制备球形纳米碳酸钙的研究

将汉白玉废料通过高温煅烧分解得到氧化钙,再用氯化铵循环液溶解氧化钙制得碱性氯化钙溶液,除去其中的Mg、Fe等杂质得到氯化钙精制溶液,利用化学方法合成得到碳酸钙粉体.用X射线衍射(XRD)、扫描电镜(SEM)及激光粒度分析仪、白度仪对碳酸钙产品的晶相组成、形貌、粒度分布、白度及化学组成进行了分析,所得产品为纯度达98.5%以上、白度达97%以上、平均粒度为80nm左右的球形纳米级碳酸钙.并对碳化反应速率及合成球形纳米碳酸钙的影响因素进行了分析.实验中循环使用NH4Cl,氨的排放量小,减少了环境污染.     

Preparation and characterization of polyurethane microcapsules containing n‐octadecane with styrene‐maleic anhydride as a surfactant by interfacial polycondensation

A series of polyurethane microcapsules containing a phase change material (PCM) of n‐octadecane was successfully synthesized by an interfacial polymerization in aqueous styrene‐maleic anhydride (SMA) dispersion with diethylene triamine (DETA) as a chain extender reacting with toluene‐2,4‐diisocyanate (TDI). The average diameter of microPCMs is in the range of 5–10 μm under the stirring speed of 3000–4000 rpm. Optical and SEM morphologies of microPCMs had ensured that the shell was regularly fabricated with the influence of SMA. FTIR results confirmed that the shell material was polyurethane and the SMA chains associated on core material reacted with TDI forming a part of shell material. The shell thickness was decreasing in the range of 0.31–0.55 μm with the molar ratio of DETA/TDI from 0.84 to 1.35 and the weight of core material increasing from 40 to 80% (wt %). By controlling the weight ratio of PCM as 40, 50, 60, 70, and 80% in microPCMs, it was found using DSC that the T_m and T_c of microPCMs were in the range of 29.8–31.0^oC and 21.1–22.0°C and an obvious phase change had been achieved nearly the same temperature range of that of PCM. The results from release curves of microPCM samples prepared by 1.4, 1.7, and 2.0 g of SMA indicated the release properties were affected by the amount of the dispersant, which attributed to the emulsion effect and shell polymerization structure. The above results suggest that the shell structure of microPCMs can be controlled and the properties of microPCMs determined by shell will perform proper practical usage. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4996–5006, 2006     

Analytical solution for the axisymmetric plane strain electroelastic dynamics of a special non-homogeneous piezoelectric hollow cylinder

By virtue of the introduction of a dependent variable and the separation of variables technique, the axisymmetric plane strain electroelastic dynamic problem of a special non-homogeneous piezoelectric hollow cylinder is transformed to a Volterra integral equation of the second kind about a function with respect to time, which can be solved successfully by means of the interpolation method. Then the solutions of displacements, stresses, electric displacements and electric potential are obtained. The present method is suitable for a piezoelectric hollow cylinder with an arbitrary thickness subjected to arbitrary mechanical and electrical loads. Numerical results are finally presented.     

Stress Concentration Factors for a Circular Hole in Curved Beams Under Bending Loads

Abstract: As a contribution to the field of stress concentration studies, the case of circular hole in curved bar elements under bending is hereby studied. Trend values of stress concentration factors (SCF) are presented based on selected variables of the problem for two critical hole locations. The results will help to identify an SCF law for practical use by applying the statistical method of regression analysis. Two approximations obtained by means of computational methods are compared with those obtained by photoelastic experimental method.     

超声珩磨在发动机缸套光整加工中的应用研究

本文介绍了发动机缸套的新型加工工艺-功率超声珩磨的原理。特点，装置组成。关键技术，工艺效果以及其应用前景。     

外推技术结合矩量法应用于二维介质柱RCS计算

基于Richardson外推(Extrapolation)提出了一种提高精度和快速计算任意二维介质柱体的雷达散射截面(RCS)外推技术和矩量法(MOM)相结合的方法(RE—MOM)。首先用二层粗细有序网格对介质柱体截面剖分。接着采用矩量法对相应二维介质柱体的电场积分方程求解，得到介质体在某一平面入射波照射下各自的电场向量，通过外推技术获得介质柱体在这一人射波照射下细网格上高精度的电场向量，进而计算出RCS。文中计算了几个例子，并与其他数值计算方法进行了比较，结果表明RE—MOM方法是正确和有效的。     

Short fibre elastomer composites: effect of fibre length,orientation, loading and bonding agent

A series of short fibre reinforced styrene butadiene rubber (SBR) composites were prepared by incorporating sisal fibres of different lengths and different concentrations. The vulcanization behaviour and the properties of the vulcanizates were measured by the relevant ASTM procedures. The processing characteristics such as green strength and mill shrinkage were improved by the addition of fibres. The properties like tensile strength, tear strength, moduli at 10% and 20% elongations were found to be maximum for composites containing longitudinally oriented fibres of length 6 mm. Mixes containing 35 phr loading of fibres and bonding agent showed better mechanical performance than others. The failure behaviour of tensile and tear specimens have been analysed by scanning electron microscopy techniques. Paper presented at the poster session of MRSI AGM VI, Kharagpur, 1995     

日本“绿色”包装的系统化理念及其启示

本文通过对日本包装系统的考察和与中国包装现状的对比,阐述了“绿色”包装系统的基本理念和构建要素,总结出必须通过科技、法制等使包装产业形成一个系统化的“生态链”,使包装业真正造福于人类。