Peculiarities of rheological behavior of filled polymer melts in uniaxial stretching

The peculiarities of theological behavior of filled polymer melts in uniaxial extension in a wide range of strain rates (from 2× 10^–5 to 1 × 10^–1 s^–1) have been studied. Linear polyethylene and 1,4-polybutadiene containing up to 21.5 vol.% of carbon black, silica, calcium carbonate or glass fibers were used. It has been found that the transition from uniform to nonunion stretching due to the neck formation is typical of all specimen compositions, when they approach steady-state straining. Depending on the structure and rheological characteristics of the compositions general conditions for this transition have been established. The general regularities for varying the rheological characteristics of filled polymers in the course of their uniform stretching have been recognized. These regularities depend on the molecular characteristics of the polymer matrix and the presence in the compositions of the structural framework of high disperse filler or the network formed by the entangled fibers. Using polyethylene compositions it has been shown that the introduction of small amounts of disperse or fibrous fillers can give rise to acceleration of the relaxation process in filled polymers.     

酚醛玻璃钢动态本构关系的实验研究

本文叙述了在轻气炮上作高速撞击实验,使用碳膜压阻传感器,一次记录多个应力历史波形,用Lagrange分析和路径线方法,求材料动态本构关系的方法。给出了应力在2 GPa、应变率4105S-1以下酚醛玻璃钢的数值形式本构关系。探讨了强应力脉冲在酚醛玻璃钢中传播衰减的物理原因。     

两种再生粗骨料混凝土单轴受压性能研究

为研究影响再生混凝土力学性能的因素,将建筑结构中使用最为广泛的C30与C40两种强度等级的废混凝土破碎成再生粗骨料RCA(recycled coarse aggregate),根据实测RCA吸水率调整了配合比。以RCA来源和RCA取代率为变量,设计了9组再生混凝土试件,进行立方体抗压强度及棱柱体单轴受压试验。基于试验数据,得到了两种不同来源RCA的再生混凝土弹性模量、峰值应变等重要力学性能参数,绘制了再生混凝土应力-应变曲线。结果表明,随着RCA取代率的增加,两种不同来源RCA再生混凝土弹性模量和立方体抗压强度均表现为下降,RCA强度对再生混凝土各项力学性能均有影响。     

Calculating the Linear Creep Strains of Viscoelastic Fibers under Tension

The linearity domain for the viscoelastic properties of high-molecular organic fibers is determined. The linearity criteria are coincidence of experimental compliance curves and linearity of isochronic creep curves. Statistical criteria are used to establish linearity. The influence function in the constitutive equation of linear viscoelasticity is an Abel-type power kernel. The calculated and experimental creep strains are in good agreement both at the initial stage of deformation and after long-term loading__________Translated from Prikladnaya Mekhanika, Vol. 41, No. 5, pp. 97–106, May 2005.     

压应力状态下细观非均匀性岩石的损伤局部化和应力应变关系分析

利用摩擦弯折裂纹模型研究了受压条件下细观非均匀性岩石的损伤局部化问题和全过程应力应变关系．模型考虑了裂纹相互作用对损伤局部化和全过程应力应变关系的影响,确定了损伤局部化发生的条件,分析了产生损伤局部化的原因．研究表明全过程应力应变关系包括线弹性阶段、非线性强化阶段、应力降和应变软化阶段．通过和实验对比分析验证了模型的正确性和有效性．     

Propagation and interaction of ultra-short pulses in quadratic crystals with controlled dispersion

Propagation of ultra-short optical pulses in an environment with quadratic nonlinearity and modulated dispersion is studied. It is shown that periodic modulation of the velocity-mismatch sign and of the third-order dispersion coefficient allows one to suppress pulse scattering and decompression, which noticeably increases their interaction efficiency. Original Russian Text ? A.A. Ivanov, B.B. Petrov, C.C. Sidorov, 2009, published in Vestnik Moskovskogo Universiteta. Fizika, 2009, No. 1, pp. 90–92.     

Retarded thermal oxidation of strained Si substrate

Strained Si is recognized as a necessary technology booster for modern integrated circuit technology. However, the thermal oxidation behaviors of strained Si substrates are not well understood yet despite their importance. In this study,we for the first time experimentally find that all types of strained Si substrates(uniaxial tensile, uniaxial compressive,biaxial tensile, and biaxial compressive) show smaller thermal oxidation rates than an unstrained Si substrate. The possible mechanisms for these retarded thermal oxidation rates in strained Si substrates are also discussed.