PVC-U塑料异型材的原辅材料分析

塑料异型材的物理化学性能,不但对型材的外观如表面光亮度等有影响,而且对型材的焊接强度和低温冲击强度等有重要的影响。文章从型材原辅材料的结构及特点等方面来研究原辅材料的选用对PVC型材的性能和外观的影响,重点对PVC、微粒子填充和抗冲击改性剂进行研究,提出合理的原辅材料要求,且设计高效的型材配方。     

The effect of low‐filler volume fraction on the elastic modulus and thermal expansion coefficient of particulate composites simulated by a multiphase model

The aim of this investigation is to determine the effect of low‐filler volume fraction on the elastic modulus and the thermal expansion coefficient of particulate composites. In the theoretical part, theoretical model valid for low‐filler volume fractions is used to evaluate these two magnitudes. In the experimental part, low‐percentage filler contents of 3, 5, 7, and 10% are used. The density for these epoxy resin‐iron particle composites is also determined. At the same time, an attempt to explain some of the disagreements observed between theoretical values and experimental data on a qualitative basis is also made. This attempt is in part assisted by scanning electron microscopy (SEM) observations concerning structural inhomogeneities and fractographical data. The comparison of the theoretical values derived from the present model with experimental results and with theoretical values derived from other workers appears satisfactory in many cases, but in some others the discrepancies among them are considerable. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Development of a new high‐efficiency simple structure cyclone

A novel uniflow cyclone design was evaluated using three prototype cyclones. For the first two, the efficiency and Euler number were determined using airborne solid particles with a number mean diameter of 12.5 µm. Then a larger scale prototype based on the optimized geometry was compared with an existing conventional high efficiency cyclone and a vane‐induced uniflow cyclone, using mineral oil droplets with a number mean diameter of 8.9 µm. Both sets of experiments showed that the newly designed cyclone had a higher efficiency at a higher pressure requirement, in addition to the feature of a small footprint.     

焦炭颗粒增强铜-石墨复合材料的制备与性能研究

以改性酚醛树脂为粘结剂,以焦炭粉为颗粒增强相,采用传统模压成型工艺制备了一系列铜-石墨复合材料,并研究了焦炭粉的添加对复合材料的力学性能、导电性能及磨损性能的影响.结果表明:当焦炭粉质量分数为35%时,复合材料具有较好的综合性能.随着焦炭粉的加入,复合材料的弯曲强度有了显著提高,在焦炭粉质量分数为35%时弯曲强度达到最大值68.8MPa,比未添加焦炭粉时提高了近36%;同时,当焦炭粉质量分数为35%时,复合材料的电阻率已经达到了现用浸金属滑板的导电水平;焦炭粉质量分数35%的复合材料具有最低的磨损率,且在磨损过程中能在磨损表面形成较为完整的自润滑膜.     

Stavax ESR钢洗衣机面板模具开裂原因分析

针对Stavax ESR钢洗衣机面板模具开裂问题,对模具失效件进行断口扫描电镜及微区能谱分析,以及采用金相显微镜对材料基体组织进行检测,综合检测结果,最终确定造成模具早期开裂的内在原因,是由于组织中沿晶界残留未溶颗粒状及薄片状碳化物,材料强度急剧降低,脆性显著增大。模具在热加工过程中碳化物沿晶界析出形成网状碳化物,在热处理加热保温过程中,网状碳化物经过固溶和聚集,形成未溶颗粒状及薄片状碳化物。热处理加热过程的热应力以及淬火过程的组织应力,导致未溶颗粒状及薄片状碳化物周围产生内裂纹。模具冷却水孔的机加工过程,使沿晶开裂特征的内裂纹显露出来。模具服役承载时产生的工作应力,促使裂纹的进一步萌生和扩展。     

S590粉末高速钢的热处理工艺和应用

试验研究了S590粉末冶金高速钢的热处理工艺,测定了热处理后钢的硬度和晶粒度。结果表明,粉末冶金高速钢的热处理规律和淬硬性与普通高速钢基本相同,但粉末冶金高速钢的碳化物更为细小均匀,红硬性、抗压强度、耐磨性和热处理畸变等特性均优于普通高速钢。此外,还介绍了S590粉末冶金高速钢滚刀的应用。     

碲粉涂料防止铸件渗漏作用的探讨

介绍用碲涂料解决铸件渗漏的方法,对碲粉涂料防渗漏的作用形式、机理进行了探讨,并指出一些使用中的注意事项.     

SiCp/2024铝基复合材料的超塑性变形行为研究

对经过热处理和冷轧后的体积分数为17％，尺寸为3．5μm的SiC颗粒增强2024铝合金薄板在753－853K范围内进行了超塑性实验研究. 结果在813K时以10^-1/S的变形速率下获得了259％的最大延伸率，最大应力敏感系数为0．25复合材料的变形激活能值在753－793K范围内为144kJ/mol，在813－853K内为202kJ/mol，接近纯铝的晶格扩散激活能值142kJ/mol。复合材料的变形机制主要为基体晶粒滑动机制。     

Diffusion of ellipsoidal granular particles in shear flow

The diffusion of nonspherical particles has not been well understood due to the complexity of their contact mechanics and self-organization of their orientations. We perform discrete element method simulations of monodisperse ellipsoids in a shear flow with Lees-Edwards boundary conditions to quantify the relation between the diffusion coefficient and the flow parameters. The results indicate that the particle aspect ratio strongly affects the diffusion coefficient by influencing the particle orientation and alignment. We develop a scaling law for the diffusion coefficient perpendicular to the flow direction, D_yy, which combines the influences of the shear rate , the solids fraction f, the effective particle diameter d_eff and the particle aspect ratio Z. We show that , where k_d is a dimensionless pre-factor, and a fit is obtained for the functional form of χ(f, Z). This scaling law will be useful in developing continuum transport models for applications.     

Modeling drop breakage using the full energy spectrum and a specific realization of turbulence anisotropy

The assumption of homogeneous isotropic turbulence when modeling drop breakage in industrially relevant geometries is questionable. We describe the development of an anisotropic breakage model, where the anisotropy is introduced via the inclusion of a perturbed turbulence spectrum. The selection of the perturbed spectrum is itself motivated by our previous large-eddy simulations of high-pressure homogenizers. The model redistributes energy from small to large scales, and assumes that the anisotropic part of the Reynolds stresses is confined to the energy-containing range. The second-order structure function arising from the perturbed spectrum is used in the standard framework of Coulaloglou and Tavlarides to calculate breakage frequency. While the base model exhibits non-monotonic behavior (by predicting a maximum value for a certain drop size), the effect of anisotropy is shown to increase breakage frequency in length scales larger than this peak, thereby reducing non-monotonicity. This effect is more pronounced for small turbulence Reynolds numbers.