Creep of PVDF monofilament sutures: service performance prediction from short-term tests

Isothermal short-term creep of poly (vinylidene fluoride) (PVDF) monofilament sutures was determined at several temperatures between 10 and 90 °C under the stress of 10 MPa. Long term service performance was predicted for 10 decades of time. The compliance master curve as a function of time fits a hyperbolic sine equation. The temperature shift factor as a function of the temperature a_T (T) is accurately represented by a general equation based on free volume. A simple relationship between the two parameters of the equation is explored. The viscoelasticity of PVDF is also seen in dynamic mechanical analysis performed at the frequency of 1 Hz. The origin of the viscoelastic character well present in the deformability of the PVDF in service is due to the occurrence of the α_c relaxation that is active at ∼50 °C (E″ peak at 1 Hz).     

金属－橡胶硫化粘接过程中分子取向行为的间接证据

对金属－橡胶热硫化粘接复合体的剥离行为进行了研究，同一粘接试样的双向１８０°剥离试验显示出了巨大的差异。本文分析了弹性材料在硫化过程中的分子行为，并提出了相应的新假设，认为这是由于金属－橡胶在硫化粘接过程中分子取向交联行为所致。这种双向１８０°剥离破坏现象可被看作是金属－橡胶硫化粘接过程中分子取向行为的间接证据。     

关于超立方体网络的容错路径选择

文章给出ｎ－维超立方体网络的容错路径选择算法，该算法具有自适应性，可以防止死锁和活锁现象的发生，应用该算法，可求出一条基于安全优先策略的可行最短路径。     

MOSFET亚阈特性分析与低温按比例缩小理论的研究

器件尺寸按比例缩小是实现超大规模集成电路的有效途径，但寄生和二级效应却将器件限在一定的水平，本文在对比分析常温与低温下小尺寸器件效应的基础上，重点研究了ＭＯＳ器件亚阈特性对器件性能及按比例缩小的影响，并根据低温工作的特点，提出了ＭＯＳ器件一种低温按比例缩小规则，该原则对低温器的优化设计，从而更大程度在提高电路与系统性能具有重要的指导意义。     

From the individual element test to finite element templates: Evolution of the patch test

This paper starts a sequence of three articles that follow an unconventional approach in finite element research. The ultimate objective is to construct high-performance elements and element-level error estimators for those elements. The approach takes off from our previous work in high-performance elements and culminates with the development of finite element templates. The present paper concentrates on the patch test and evolved versions of the test that have played a key role in this research. Following a brief review of the historical roots, we present the Individual Element Test (IET) of Bergan and Hanssen in an expanded context that encompasses several important classes of new elements. The relationship of the IET to the multielement forms A, B and C of the patch test and to the single-element test are investigated. An important consequence of the IET application is that the element stiffness equations decompose naturally into basic and higher-order parts. The application of this decomposition to the “sanitization” of the non-convergent BCIZ element is described and verified with numerical experiments. Two sequel papers in preparation are subtitled ‘the algebraic approach’ and ‘element-level error estimation’. These apply the fundamental decomposition to the derivation of templates for specific mechanical elements and to the construction of element-level error estimators, respectively.     

Rheological behaviour of concentrated yeast suspension

The effect of yeast cell volumetric concentration on the rheological properties of the suspensions was measured in a pipe-flow viscometer at 30°C: at low microbial concentrations the suspensions were Newtonian; however, non-Newtonian behaviour, which could be described by the power-law equation, was observed with suspensions at high microbial volumetric concentrations. At conditions of constant microbial morphology and growth rate, the results also indicated that a relationship could be developed between the power-law constants and the microbial volumetric concentration.     

Tailored Microstructures: Can a Dream come True?

The mechanical properties of crystalline solids are determined by the spatial distribution of chemical elements and crystal defects, which is referred to as microstructure. Microstructure changes during processing, and its evolution can be influenced by processing conditions and external fields. Advanced microstructure codes can cover the through‐process microstructural evolution and allow first predictions of terminal materials properties.     

新型聚氨酯固-固相变储能材料的组成与热性能的关系

利用差示扫描量热仪、傅里叶红外光谱仪、广角X射线衍射仪研究了一种新型的以聚乙二醇为软段的聚氨酯相变储能材料。结果表明，当软段含量低于90％（质量分数，下同）时，即使温度高于聚乙二醇的熔点，此类材料仍不会熔化成液体，而表现出一种固-固相变行为。该聚氨酯储能材料相变焓较大，相变温度适中，且随着软段含量的减少，材料相变焓和相变温度呈递减趋势。其相变过程实质是聚氨酯软段聚乙二醇由结晶固态转变为无定形固态的过程。     

Effects of the cryogenic cooling on the fatigue strength of the AISI 304 stainless steel ground components

For environmental considerations, the substitution of the conventionally used oil-based grinding fluids has nowadays become strongly recommended. Although several alternatives have been proposed, cryogenic cooling by liquid nitrogen is the non-polluting coolant that has been given relatively more attention because of its very low temperature. In this investigation, in order to contribute to developing this promising cooling mode, its beneficial effects on the ground surface integrity of the AISI 304 stainless steel and their consequences on the fatigue lifetime are explored. Results of this investigation show that grinding under cryogenic cooling mode generates surfaces with lower roughness, less defects, higher work hardening and less tensile residual stresses than those obtained on surfaces ground under oil-based grinding fluid. These surface enhancements result into substantial improvements in the fatigue behaviour of components ground under this cooling mode. An increasing rate of almost 15% of the endurance limit at 2 × 10⁶ cycles could be realized. SEM analyses of the fatigue fracture surfaces have shown that the fatigue cracks observed on the specimens ground under cryogenic cooling are shorter (i.e., 30-50 μm) than those generated under oil-based cooling mode (i.e., 150-200 μm). The realized improvements in the surface integrity and in the fatigue behaviour are thought to be related to the reduction of the grinding zone temperature observed under cryogenic cooling, as no significant differences between the grinding force components for both cooling modes have been observed.     

Characterization of resol resins modified by the addition of PVC plastisols

Plastisols, which are a blend of poly(vinyl chloride) resin and a plasticizer (DEHP), were used as a toughening agent of a resol resin in order to improve the mechanical properties. It was not possible to formulate resol blends by adding more than 10 % of plastisol owing to a lack of apparent homogeneity in the systems, which also showed many air bubbles. The relationship between dynamic mechanical, mechanical and thermal properties and the amount of plastisol added was studied. It was determined from the infrared spectroscopy and dynamic mechanical results that the resol–plastisol blends seem to be formed by a reaction between the phenol and PVC giving a higher crosslinked structure. An improvement in the thermal resistance of the blends at lower temperatures was observed with an increase in the percentage of plastisol. Flexural analysis showed the elastic behaviour of the systems. However, it was not possible to observe the effect of the plasticizer (DEHP) owing to the low quantity of plastisol that was added to the resol. Copyright © 2004 Society of Chemical Industry