Effect of pigmentation on organic coating characteristics

The paper reviews the effects of pigmentation, i.e. type of pigment and pigment volume concentration, on organic coating characteristics, such as curing and film formation, mechanical properties, thermal expansion coefficient, glass transition temperature, stress development, physical ageing and water transport. The main families of pigments used in the fabrication of organic coatings and the effect of nanopigments incorporation in binders are also discussed.     

Y型管节点应力集中系数有限元分析

用有限元计算了位于渤海湾的BZ-28单点停泊系统导管架Y型管节点在轴向力，平面内弯矩以及平面外弯矩作用下的热点应力集中系数以及支管和弦管应力集中系数的分布，并将结果与常用的参数公式进行比较。     

Edge effects connected with thin interphases in composite materials

Different imperfect transmission conditions modelling a thin intermediate layer between two bonded materials in a dissimilar elastic strip are analysed from the point of view of possible free-edge effects. The type of imperfect model depends essentially on the mechanical properties of the interphase and can be classified as soft, comparable and stiff interfaces. Corresponding transmission conditions have been derived by asymptotic analysis. However, they are not valid, generally speaking, at a region near the free edge, where an additional boundary layer should be constructed. By using FEM the size of this region is estimated and all possible edge-effects phenomena are classified.     

Microstructure coarsening during thermo-mechanical fatigue of Pb-Sn solder joints

Phase coarsening in as-cast solder joints produced by isothermal annealing and by thermo-mechanical cycling (TMC) (-30 to 130°C) was determined and its influence on the plastic deformation kinetics of 63Sn37Pb solder joints was investigated by stress relaxation (SR) tests. The static, isothermal coarsening kinetics were in accord with Senkov-Myshlyaev’s theory. The rate of coarsening by TMC was appreciably greater than that by isothermal annealing. The SR curves following TMC exhibited two regions with a stress exponent n > 5 at high stresses (Region A) and n ≈ 2-3 at low stresses (Region B). In both regions, the stress exponent varied in an irregular manner with the mean phase size. In Region A the plastic strain rate at a constant value of τⁿ (τ = shear stress) was relatively independent of the average phase size, while in Region B the strain rate increased with increase in phase size. The activation energy in both regions appeared to be that for lattice diffusion. Possible reasons for the anomalous effects of phase size on the plastic deformation kinetics are offered.     

发展相似模型光波导应力应变测量技术的意义

模型物理力学参数测量问题是制约相似模拟技术推广应用的主要因素之一。论文在对平面相似模型应力应变测量技术全面分析的基础上 ,重点分析了用传统测量方法与手段进行三维物理模型内部应力应变测量时遇到的困难与问题 ,阐述了发展光波导应力应变测量技术的重要意义。     

旋转平板的应力分析

本文分析形状不规则旋转平板的应力状态．利用完备的双重三角级数作为试函数，运用数学规划加权残值法求得旋转板的位移和应力．数字计算结果表明尺寸不均匀旋转结构上的应力分布状况与尺寸匀称结构有很大的不同，因此更应注意其安全问题．     

Screening for posttraumatic stress disorder: An evaluation of two self-report scales among crime victims.

The validity of the Impact of Events Scale (IES) and the Posttraumatic Stress Disorder (PTSD) Symptom Scale, Self-Report version (PSS-SR) was examined among crime victims. Both instruments performed well as screeners for PTSD. For the IES, sensitivity ranged between .93 and 1.00; for the PSS-SR, sensitivity ranged between .80 and .90. Specificity for the IES ranged between .78 and .84 and for the PSS-SR ranged between .84 and .88. Some individual items from the 2 scales performed just as well as the total scales. The authors conclude that either of these short self-report instruments or their individual items are suitable as screeners for PTSD, specifically in settings where mental health professionals are unavailable. Cross-validation of these results is necessary because of the small sample size in this study. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A micromechanics approach for damage modeling of polymer matrix composites

A new model for damage evolution in polymer matrix composites is presented. The model is based on a combination of two constituent-level models and an interphase model. This approach reduces the number of empirical parameters since the two constituent-level models are formulated for isotropic materials, namely fiber and matrix. Decomposition of the state variables down to the micro-scale is accomplished by micromechanics. Phenomenological damage evolution models are then postulated for each constituent. Determination of material parameters is made from available experimental data. The required experimental data can be obtained with standard tests. Comparison between model predictions and additional experimental data is presented.     

Material forces for crack analysis of functionally graded materials in adaptively refined FE-meshes

This work describes the computation of fracture parameters in functionally graded materials (FGMs) with stationary cracks. To this end the continuum concept of material forces is employed, such that the corresponding balance equation can be discretized with a standard Galerkin finite element procedure. A domain-type formulation is used for evaluation of a vectorial J-integral, where in the practical implementation the material nodal forces of the finite element discretization are summed up in a finite region of the crack-tip. In this way the numerical calculation is completely independent from the alignment of the finite element mesh or any selected integration contour, which is most attractive for adaptively refined finite element meshes. For illustrative purpose the accuracy of the method is discussed for two examples based on comparison with available theoretical and numerical solutions.     

FE analysis of stresses and stress intensity factors of interfacial cracks in a CTS specimen

A plane stress finite element analysis was implemented to understand the stress fields for a crack lying at an aluminium/epoxy interface of a compact tension and shear specimen. The interaction integral method was used to separate the mixed-mode stress intensity factors at the interfacial crack-tip under different loading modes, which can have important implications for characterisation of interfacial crack growth.