New polymeric blends from hydrogenated styrene–butadiene rubber and polyethylene

New thermoplastic elastomeric blends based on hydrogenated styrene–butadiene rubber (HSBR) and low-density polyethylene (LDPE) were prepared by the melt blending technique. The rheology, structural and mechanical properties were measured as a function of blend composition. The HSBR/LDPE blend had a higher tensile strength, modulus, and work-to-break with low elongation at break compared with those of pure HSBR. X-ray diffraction studies demonstrated co-crystallisation and a remarkable increase in the degree of crystallinity. The improvement in the mechanical properties and the uniform morphology were correlated with the interfacial adhesion and compatibilisation of the HSBR/LDPE blend through ethylene segments. The experimental results for the HSBR/LDPE blends were compared with those for HSBR/high-density polyethylene (HDPE) and SBR/LDPE blends. The mechanical properties of the HSBR/LDPE blend were found to be superior. The results were explained on the basis of morphology and interaction.     

塑料注射成型保压过程数学描述

在对塑料注射成型中保压过程进行深入分析的基础上,提出了合理的假设并进行了必要的简化,利用连续介质力学的基本方程导出了可压缩、非牛顿粘性流体在模具型腔中非等温流动的控制方程,选用了恰当的材料性质模型,建立了可对保压过程进行数值模拟的数学模型。     

凝固模型在高碳钢方坯连铸中的应用

依据湘钢现场条件,建立了连铸方坯凝固传热数学模型,分析了过热度、拉坯速度、二冷水量对高碳钢方坯凝固过程的影响,确立了二次冷却与高碳钢二次枝晶间距的关系式,提出了改善高碳钢方坯连铸中心缩孔的途径．     

Use of a theoretical model to investigate RF and DC reactive sputtering of titanium and chromium oxide coatings

An analysis of RF and DC reactive sputtering techniques is presented. The transition between a metal sputtering mode and a compound sputtering mode is usually noticed with a metallic target and an argon+oxygen gas mixture. The so-called hysteresis effect often observed for small amounts of reactive gas is explained in recent models. By considering gas kinetics parameters, it is possible to evaluate quite simple relationships between the main processing parameters. These theoretical calculations enable the prediction and aid the understanding of instability phenomena observed in reactive sputtering. In this paper, the effects of some parameters on the position and size of instability regions are discussed, and the difference between DC and RF reactive deposition is investigated. Simulations and experimental results are compared for the case of titanium and chromium oxide thin films prepared by DC and RF reactive sputtering. The influence of sputtering power on the position of the hysteresis loop is analysed theoretically and experimentally, and the changes observed between the reactive sputtering of titanium and chromium oxide materials are also discussed.     

Analysis of machining of FRPs using FEM

An initial attempt has been made to develop a mathematical model for machining of FRPs. The anisotropic theory of plasticity has been utilized. The analysis is carried out for four different FRP materials and for four different fibre orientation angles. A total Lagrangian formulation-based transient elasto-plastic finite element analysis has been adopted.     

Ordering, deformation and microstructure in L10 type FePt

The long-range order (LRO) parameters for L1₀ FePt have been determined by the X-ray diffraction method from powder specimens as functions of time and temperature from 773 K to near 1573 K. By and large, the ordering takes place rapidly below T_c and reaches as high as 0.85 even at 773 K in the first 30 min. The LRO value is about 0.81 near T_c (1573 K) before it drops abruptly to zero at 1573 K. As a result, the order–disorder transformation in FePt is concluded to be a first-order phase transformation. Deformation behavior in an L1₀ type FePt alloy was investigated through both compressive and tensile deformation from room temperature (RT) to 1073 K. The negative temperature dependence of yield stress in this alloy contrasts with the positive dependence in L1₀ type TiAl. The elongation increases exponentially with temperature and reaches 6% at 873 K. The strain rate sensitivity parameter against temperature is similar to those found in silver and copper, where the non-zero minimum is centered in a broad basin. This indicates that the temperature-dependent deformation in the range of RT to 1073 K is analogous to that of some face-centered cubic metals, but significantly different from that of L1₀ TiAl. The deformation structure investigated by TEM shows that slip and twinning are the two major deformation mechanisms. The identified slip systems include ; and . The slip system, however, is only active at very low temperatures, e.g. 77 K. The twin system was identified as type. No pseudo-twinning was found in this alloy. The deformation below RT is mainly carried out by both superdislocations and ordinary dislocations, while above 673 K, it is carried out mainly by ordinary dislocations. The morphology of these dislocations in the entire temperature range indicates that the dislocations do not experience a high Peierls stress contrary to that observed in TiAl. No self-dissociation of superdislocations or APB cross-slip onto cube planes was observed under weak beam conditions.     

Comparisons of experimental and theoretical frequencies for rectangular plates with various boundary conditions and added masses

This paper is concerned with a vibration analysis of rectangular plates with masses mounted on various locations. The edges of the plates may either be clamped or simply supported. The study is particularly useful in the understanding of the vibration of printed circuit boards used in the electronics industry. An energy method is developed to obtain analytical frequencies of the plates with various edge support conditions. The analytical procedure using the Rayleigh-Ritz approach is adopted in which each of single and multiple trigonometric series terms is used to represent the shape function. Two experimental methods, a spectrum analyser and a TV-holographic system, are used to study the behaviour of the plate vibrations. The holographic image produced at the corresponding mode frequencies by using the TV-holography technique has been applied to verify the frequency spectra obtained from the spectrum analyser. The experimental results have been used to illustrate the validity of the analytical model. The comparisons show that the analytical model predicts natural frequencies reasonably well, in which the EM 100-term model is suggested for vibration plates with higher modes or heavier loads.     

Axisymmetric response of circular plates with piezoelectric layers: an exact solution

Electromechanical responses of symmetric circular laminates consisting of piezoelectric layers are studied, and the influence of surface and interlayer electrodes are involved. The laminates are traction-free on the top and bottom surfaces, but may be subjected to external forces at the lateral edge and to voltages applied across certain layers. Under axisymmetric deformation conditions, an approximate model which employs Kirchhoff hypothesis and incorporates the charge equation of electrostatic is established. Then, a closed-form three-dimensional solution of the laminates is generated in a very straightforward manner by the solution of the approximate model. The three-dimensional solution fulfills all field equations and interface or surface conditions as well as the specified electric edge boundary conditions; the only restriction is that the mechanical edge boundary conditions are satisfied in an average manner, rather than point by point. Thus, according to Saint-Venant's principle the proposed solution is exact in the interior region of the laminates.     

基于数学形态学的图像形态滤波

文中定义了多结构元素腐蚀、膨胀、开、闭四种多结构元素数学形态学滤波器,讨论了它们的性质和滤波性能,指出多结构元素腐蚀滤波和膨胀滤波在噪声滤除,尤其是滤除附着在目标图像边缘上的噪声方面优于多结构元素开、闭滤波;多结构元素开滤波和闭滤波在目标图像的细节保护方面则优于多结构元素的腐蚀滤波和膨胀滤波;多结构元素的腐蚀、膨胀、开、闭滤波在细节保护方面均优于单一结构元素的开、闭滤波。最后根据形态学表示理论给出了基于多结构元素的数学形态学滤波器设计方法。     

Pulsed laser deposition of Y2O3 : Eu thin film phosphors

Thin films of Y₂O₃ : Eu cathodoluminescent (CL) phosphors were deposited using pulsed laser deposition using deposition temperature between 250°C and 800°C, O₂ pressures between residual vacuum (2×10⁻⁵ Torr) and 6 Torr, and post annealing up to 1200° for 1 h in air. The CL efficiency of the best thin film was about one third that of the starting powder. The brightness and efficiency of the thin films improved as the deposition temperature, O₂ pressure and post annealing temperature were increased, except that O₂ pressures above 600 mTorr did not significantly improve the CL properties. At deposition temperatures >600°C, the surface morphology changed from a smooth film to a nodular deposit for O₂ pressures >200 mTorr, with nodule dimensions ≈100 nm. Simultaneously, the CL properties improved dramatically because of enhanced optical scattering out of the thin film. Optical scattering was discussed in terms of anomalous diffraction. The CL properties also improved dramatically with high temperature post annealing. This effect was interpreted in terms of improved crystallinity and activation of the Eu. The low brightness and efficiency of thin films versus powder was affected by depletion of the Eu in the thin films owing to the deposition process.