A Comparison of Linear with Nonlinear Viscoelastic Solutions for Shear Stress Concentration in Double Lap Joints

The correspondence principle based on the Maxwell model and a nonlinear viscoelastic solution involving an iterative scheme are used to describe the time dependent variation of the adhesive maximum shear stress in adhesively bonded double lap joints. The results indicate that if the correspondence principle is applied, the use of Maxwell chain is necessary to approximate the continuous change in the relaxation time and to coincide with the results calculated using the nonlinear viscoelastic theory.     

A Comparison of Linear with Nonlinear Viscoelastic Solutions for Shear Stress Concentration in Double Lap Joints

The correspondence principle based on the Maxwell model and a nonlinear viscoelastic solution involving an iterative scheme are used to describe the time dependent variation of the adhesive maximum shear stress in adhesively bonded double lap joints. The results indicate that if the correspondence principle is applied, the use of Maxwell chain is necessary to approximate the continuous change in the relaxation time and to coincide with the results calculated using the nonlinear viscoelastic theory.     

Prediction and experimental verification of damping in 3-D braided textile structural composites

The material damping characteristics of 3-D braided textile structural composites were investigated in this paper. A model for predicting damping in these materials was developed based upon the classical laminated plate theory. The model modified the existing models for predicting the static moduli of 3-D textile structural composites by using the elastic-viscoelastic correspondence principle. The basic engineering constants were replaced with their corresponding complex forms by applying the elastic-viscoelastic correspondence principle to them. In this study, the basic damping loss factors (i.e. η_L, η_T, η_LT and η_vLT) were obtaiend by a modified Hashin's theory, Rule-of-Mixture Laws, and an indirect method on the basis of empirical works. From complex numerical results, we concluded that axial damping, flexural damping, coupling damping, and in-plane shear damping coefficients were all functions of the yarn orientation angle and fiber volume fraction in 3-D braided textile structural composites. Experimental data supported theoretically predicted results.     

Combined experimental and DFT study on high-temperature thermochromism of Co-doped LaCrO3 coating for thermal indicator

Noncontact temperature measurement using thermochromic materials is vital in the field of temperature indication, but the related mechanisms behind thermochromic behavior are diverse and high complexity, and the color-temperature correspondence is poorly explored. This paper systematically studied the thermochromic mechanisms and color-temperature correspondence in the cobalt-doped LaCrO₃ coatings via experiment and density functional theory study. The coatings appear reversible thermochromism from green to black with temperature and composition, functions from room temperature to 700°C. This thermochromism is attributed to the lattice expansion and bandgap reduction as the temperature increase, and a model of temperature effect bandgap was proposed. Meanwhile, the coating temperature can be inferred from the color change because the CIE chromaticity coordinate of the coating varies linearly with temperature, and the mean relative error of thermochromic measurements is 8.28%. Furthermore, the cobalt doped introduces impurity energy levels and enhances the interaction between photons and carriers, which reduce the bandgap and increase the absorption in the visible spectrum resulting in darker colors. This work provides a stable and efficient high-temperature thermochromic coating that has a wide thermochromic temperature range and clear color-temperature correspondence, which shows broad application prospects in the field of thermal indication at high temperatures.     

量子化学中的内积及其模型

内积是量子化学中广泛应用的一个基本概念。首先对内积概念的产生进行了探讨,进一步对其进行了拓展,进而给出基本的模型和数学抽象,并结合具体的例子说明了内积的应用。最后还以德布罗意波来描述电子状态时的测不准原理,只能准确地描述电子的位置与动量之间的一个量来阐述了量子化学中内积与波函数的对应关系。     

Prediction of the Crevice Corrosion Incubation Period of Passive Metals at Elevated Temperatures: Part I — Mathematical Model

Previous researchers have numerically modelled the crevice corrosion of particular classes of metals and alloys. Applicable to passive metals immersed in an appropriate electrolyte, a new crevice corrosion model simulates the general passive crevice corrosion problem. Rapid approach of chemical equilibrium is assumed. Equilibrium constants and transport properties are adjusted for elevated temperature via the correspondence principle (Criss and Cobble, 1964) and the Nernst‐Einstein equation, respectively. The corrosion rate is adjusted for thermal and acidity effects via an Arrhenius expression and a Freundlich isotherm, respectively. Presented in a sequel publication, the predictions compare favourably with experimental results.     

Combined Thermometric Analysis of a Series of Highly Dealuminated USY Zeolites

A transient reactor model was used to consolidate and quantify the data of ammonia adsorption microcalorimetry and single ammonia TPD runs, using several members of the commercial CBV series of dealuminated HY zeolites. The model accounts for the competitive re-adsorption of molecules desorbing from multiple sites, using the microcalorimetric data to constrain the desorption energy parameters to physically meaningful values. All TPD profiles were well represented by models consisting of only two or three distinct site types, even though the differential heat plots imply a continuous distribution of sites in the 160-80 kJ/mol range for all catalysts. Increasing dealumination severity is evidenced by a decrease in total site density for sites 100 kJ/mol. While there was no evidence of an enhancement of adsorption strength within the series studied, the range of site strengths available remained the same. There is correspondence between the density of adsites = 100 kJ/mol and the framework Al³⁺ concentration, although the ratio of these is less than one, even for Si/Al80. The inherent limits in using ammonia adsorption as an acidity probe are briefly mentioned.     

The elastic moduli of particulate-filled polymers

The static and dynamic elastic moduli of particulate composites, consisting of two phases, one of which has isotropic–elastic and the other linear viscoelastic properties, were studied. For this purpose a model defining the approximate equations for determining the elastic modulus of a composite from the properties of the constituent materials was used. Classical theory of elasticity was applied to this simplified model of a composite-unit cell. The following assumptions are made: (i) filler particles are spherical; (ii) fillers are completely dispersed; and (iii) the volume fraction of fillers is sufficiently small, so that any interaction among fillers may be neglected. A class of iron-filled epoxy composites was subjected to tests in order to compare the theoretical values with the experimental results. The elastic modulus calculated by the expression derived in this study seems to corroborate with the experimental results fairly well. Finally, by applying the correspondence principle to this expression, theoretical relationships for the dynamic storage and loss moduli were also derived.     

Nonlocal Properties of the Phase-Separation Diagrams of Multiphase Systems

Relationships describing the nonlocal properties of phase-separation diagrams are derived for multiphase multicomponent systems. These relationships are based on the Euler equation, the correspondence principle, and the rule of contiguity of regions. A classification of phase-separation diagrams is suggested.     

A kinetic model for sulfur accelerated vulcanization of a natural rubber compound

Vulcanization kinetics for a natural rubber compound were studied by a kinetic approach using the cure meter and DSC methods. A simplified but realistic model reaction scheme was used to simulate induction, curing, and overcure periods continuously. Physically significant parameters of the model were extracted from isothermal experimental data using a cure meter. The calculation demonstrated a good correspondence with isothermal cure meter data over the temperature range studied. The length of induction time, variation of maximum modulus with temperature, and the reversion phenomena observed from cure curves can be predicted. DSC data were found to be incompatible with the cure meter test, because the complex vulcanization reaction system is multiexothermal and it is difficult to isolate the heat due to crosslinking. Hence, the cure meter technique is suggested for the study of crosslink formation. The kinetic approach provides a way to incorporate vulcanization kinetics into simulation of reactive processing operations. © 1996 John Wiley & Sons, Inc.     

Modeling Sintering of Multilayers Under Influence of Gravity

There is a tendency for multiple functional ceramic layers used in various applications to have increasing surface areas and decreasing thicknesses. Sintering samples with such geometry is challenging, as differential shrinkage of the layers causes undesired distortions. In this work, a model, which describes the combined effect of sintering and gravity of thin multilayers, is derived and later compared with experimental results. It allows for consideration of both uniaxial and biaxial stress states. The model is based on the Skorohod‐Olevsky viscous sintering framework, the classical laminate theory and the elastic‐viscoelastic correspondence principle. The modeling approach is then applied to illustrate the effect of gravity during sintering of thin layers of cerium gadolinium oxide (CGO), and it is found to be significant.     

Correspondence analysis of color–emotion associations

Emotions are often associated with colors, but what mediates color–emotion associations is not fully understood. This study examined associations between colors and emotions using correspondence analysis. The hypothesis that emotions are associated with colors through the correspondence between the hue circle and the circumplex model of emotion/affect was tested. Participants viewed 40 colors and reported a word that expressed an emotion that they associated with or felt in response to each color. Participants' responses were aggregated into a contingency table of colors and emotion words, and a correspondence analysis was conducted. An eight‐dimensional biplot was obtained. The first and second dimensions were related to hue, and the hue configuration was similar to colors' spectral trajectory in the CIE xy space or the CIELAB a*b* color space. The configuration of emotions was not consistent with the circumplex model of emotion, which rejected the above hypothesis. The associations in dimensions 1 and 2 appeared to be mediated by the perceived temperature of colors and emotions. In dimensions 3–6, dimensions that seemed to reflect secondary associations based on cultural convention or personal experiences (such as white with emotionless and purity and blue with depression) were obtained. These results also demonstrated the usefulness of correspondence analysis for analyzing color–emotion associations due to its ability to reveal the underlying statistical structure of associations.     

A micromechanical approach to elastic and viscoelastic properties of fiber reinforced concrete

Some aspects of the constitutive behavior of fiber reinforced concrete (FRC) are investigated within a micromechanical framework. Special emphasis is put on the prediction of creep of such materials. The linear elastic behavior is first examined by implementation of a Mori-Tanaka homogenization scheme. The micromechanical predictions for the overall stiffness prove to be very close to finite element solutions obtained from the numerical analysis of a representative elementary volume of FRC modeled as a randomly heterogeneous medium.The validation of the micromechanical concepts based on comparison with a set of experiments, shows remarkable predictive capabilities of the micromechanical representation.The second part of the paper is devoted to non-ageing viscoelasticity of FRC. Adopting a Zener model for the behavior of the concrete matrix and making use of the correspondence principle, the homogenized relaxation moduli are derived analytically. The validity of the model is established by mean of comparison with available experiment measurements of creep strain of steel fiber reinforced concrete under compressive load. Finally, the model predictions are compared to those derived from analytical models formulated within a one-dimensional setting.     

An experimental and theoretical study of creep of a graphite/epoxy woven composite

The creep behavior of woven fiber polymer composites has been investigated through both an experimental study and analytical modeling. In the modeling, the matrix is assumed to be a 4-parameter model (a Maxwell-Voigt combination) and the fibers to be elastic. The fiber undulation model developed by Ishikawa and Chou for elastic behavior of woven fiber composites has been extended to the viscoelastic system by the correspondence principle. This considers the longitudinal and transverse fibers separately. The weave geometry and dimensions are accounted for, thus bringing the model closer to the actual composite. While this model has been used previously to predict the composites elastic behavior, this is the first time it is considered as a viscoelastic solid, which helps determine its time dependent behavior. The resultant model takes into account the different parameters associated with the weave (the density of the fibers in the weave, the radius of the fibers and the profile of the fill and warp fibers), volume concentration of the fiber and matrix in the composite, and the elastic moduli of the fill and warp fibers and the viscoelastic properties of the polymer matrix. We have conducted creep tests on graphite fiber/epoxy composites to evaluate our model. Experiments have been conducted from room temperature (22°C) to 200°F (93°C). The results from experiments have been analyzed and an inverse simulation has been performed to obtain the unknown parameters of the matrix and fibers in the composite. The model is then used to predict the creep behavior of the woven fiber composite under other loading conditions and temperature levels, showing satisfactory agreement with the data.     

Phase-selective micro-structural effects on rheological-networks,segmental relaxation,and electrical conductivity behavior of melt-mixed polyamide-12/polypropylene-multi walled carbon nanotubes ternary nanocomposites

Morphological interpretations and their correlation with biphasic rheological networks and subsequent segmental relaxation, and electrical conductivity were comprehensively addressed for polyamide-12/polypropylene-multi-walled carbon nanotubes (PA-12/PP/MWNT) based ternary nanocomposites fabricated by melt mixing route. The partial migration of MWNT from PP to PA-12 phase is evident from the spreading coefficient estimations based on interfacial dynamics and transmission electron microscopy (TEM) analysis. Melt rheology measurements based on scaling parameters associated with various viscosity models such as, Cross model, Carreau-Yasuda model, and Berzin model indicated systematic variation in network rigidity that is in tune with dispersion-selective nano-morphology of the nanocomposites. The phase inversion was attained for composition in the range of 50 to 60 wt% of PP-MWNT content as indicated by Han plot and van-Gurp Palmen plots which is in direct correspondence to dispersed-phase-volume-fraction range of ~0.3-0.36. Broadening of loss-peaks vis-a-vis enhanced storage moduli in dynamic mechanical analysis (DMA) signifies the reduced mobility (of polyamide chains) and hence the enhanced stiffness. The electrical conductivity of the nanocomposites post-annealing decreased at temperatures above 100°C demonstrating the temperature-sensitive morphology disruption (of the conductive PP-MWNT channels) in the nanocomposites.     

碟式分离机转鼓零件的最宜超转速探讨

本文通过对超速处理后的AISI316L钢的碟式分离机转鼓零件在各种工况下的应力场分析,探讨了分离机转鼓超速自增强的最宜超转速问题,并提出了确定最宜超转速的基本原则和方法.通过分析表明:用本文方法所得到的最宜超转速与已知的国外数据是相当一致的.     

Refractory concretes of a new generation. Rheological aspect of their technology

The distinctive features of the rheological behavior of bonding systems and concrete mixtures are generalized and analyzed as applied to the technology of ceramoconcretes, low-cement refractory concretes, and liquid vibrocompacted thixotropic refractory mixtures. The foundations of the principle of rheotechnological correspondence in the technology of refractory concretes are formulated. An important role of vibrations for controlling the rheological properties (vibrorheology) is demonstrated. The principal factors decisive for the rheological properties of binders and concrete mixtures are analyzed. The important role of the temperature factor is considered and the problem of development of a “warm” technology of refractory concretes is posed. The processes of mixing in the technology of refractory concretes are also discussed. Translated from Ogneupory, No. 4, pp. 6 – 15, April, 1994.     

污垢热阻实时预测模型校正与应用

针对热阻法污垢热阻预测模型在操作条件变化较大时存在很大的原理误差,不能用于污垢实时监测的问题,提出了一种对热阻法污垢热阻预测模型的校正方法。实验研究表明,校正模型原理误差小于3.5%。并针对热学法污垢热阻测量误差与结垢程度有关的特点,推导了测量误差计算式,提出测量误差实时跟踪的测量方法,依据误差值判断测量结果的有效性,提高对高污垢热阻阶段监测结果的可靠性。应用于煤油冷却器的实时监测,表明测量可靠。     

Effect of polar solvents on dynamic moduli of concentrated solutions of polyethylacrylate

There have been many investigations on the effect of solvents on the dynamic moduli of concentrated polymer solutions. However, most of the polymers investigated were nonpolar, such as polystyrenes and polybutadienes. Moreover, the samples were usually model polymers of very narrow molecular weight distribution and were either linear or branched star. Our investigation was on a commercial polymer, which is polar and has long branches but is “gel free.” The solvents used were polar plasticizers. This study was motivated by the frequent observation that a small addition of plasticizers has little effect on the rubbery modulus or has an unexpectedly large reduction of the rubbery modulus, depending on a polymer–plasticizer pair. This work examines concentrated solutions of polyethylacrylate and three plasticizers (DBP, DHP, and DOP) at concentrations above 50% for DBP and DHP and above 80% for DOP. DOP did not dissolve the rubber at the lower concentrations. The temperature range was 30–150°C, and the frequency range was 10⁻²–10² rad/s. The time–temperature correspondence was applicable over the entire range of observation. The rubbery modulus was found to be independent of the plasticizer type at all concentrations. With dilution to 90% of polymer there was only small decrease of the modulus, and with further dilution the modulus decreased with a slope of 1.8 in the double-logarithmic plot of the modulus against concentration. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 69: 1727–1736, 1998