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        Micellization and aggregation properties of sodium perfluoropolyether carboxylate in aqueous solution

        Qiwen Yin,Wanxu Wang,Wei Xue,Yanyun Bai,Xiaoyuan Ma,Zhiping Du,Guoyong Wang 한국공업화학회 2016 Journal of Industrial and Engineering Chemistry Vol.42 No.-

        Sodium perfluoropolyether carboxylate (PFPE-Na) was synthesized via hydrolyzing the correspondinghexafluoropropylene oxide oligomer (PFPF). The structure of PFPE-Na was characterized by FT-IR and 19FNMR. The micellization and aggregation properties of PFPE-Na surfactant in aqueous solution werestudied systematically using equilibrium surface tension, electrical conductivity, dynamic surfacetension, steady-statefluorescence, transmission electron microscopy (TEM) and contact anglemethodologies. The results of equilibrium surface tension at 25 C showed that the critical micelleconcentration (CMC) and the surface tension at CMC (gCMC) of PFPE-Na aqueous solution are lower thansodium perfluorooctanoate [NaPFO, C7F15COONa], which revealing that as a kind of environment-friendly surfactant, PFPE-Na is a perfect substitute of NaPFO. Electrical conductivity measurementsimplied that the micellization of PFPE-Na in aqueous solution was an exothermic and entropy-drivenprocess in the range of temperature investigated. Steady-statefluorescence and transmission electronmicroscopy (TEM) may indicate that PFPE-Na self-assemble in aqueous solution to form larger sphericalaggregates with the increase of concentration. In addition, dynamic surface tension measurements ofPFPE-Na solution showed an extremely efficient adsorption at concentrations above CMC while thedetermination of contact angle of PFPE-Na showed the wetting ability was general.

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        Nonlinear fatigue life prediction model based on material memory

        Xu Xu,Qiwen Xue,Yiqian He 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.12

        New nonlinear fatigue damage accumulation model is established on the basis of material memory theory and fatigue driving energy damage parameters to evaluate highcycle fatigue life under multilevel variable amplitude loading. The loading interaction factor is constructed on the basis of damage degree and then the model is modified to consider the effect of loading interaction on fatigue damage accumulation. The two proposed models are convenient for calculation and have only two parameters that can be easily identified through experiments. In accordance with the test data of aluminum alloy Al-2024-T42, titanium alloy Ti-6Al-4V, nodular cast iron GS61, Q235B welded joint, and hot-rolled 16Mn steel, the two models developed in this study have been verified to predict fatigue life effectively. For multilevel loading, the modified model achieves higher prediction accuracy and its results are closer to the actual test data compared with those of the other models.

      • KCI등재

        Nonlinear fatigue life prediction models based on material damage state correction

        Bowen Wang,Qiwen Xue 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.12

        The determination of the interaction factor of adjacent loads under variable amplitude loading is difficult. In this paper, two new nonlinear accumulation damage models are proposed based on the material damage state. Besides considering loading sequence, load interference, and mean stress effect, the proposed models consider the effect of material damage state and then modify the key parameter δ by introducing the load cycle ratio and the amount of material memory degradation in order to express the damage state. Verifying by different materials' test data and comparing with the existing models shows the proposed models good predictive ability and reliability. Further, in this method, there are no new variables introduced, no complex nested calculations, and only one conventional parameter that is easy to obtain by experimental fitting. Furthermore, the proposed models are convenient for fatigue life prediction in practical engineering problems.

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