Papers by Keyword: Creep

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Authors: Yi Qi, Xiao Ming Rui, Jian Cheng Wan, Jun Hui Li
Abstract: Through many samples of 1000mm2 large section conductor creep test, the creep characteristics of 1000mm2 large section conductor is summarized. Temperature reduction value for transmission line stringing construction of 1000mm2 large section conductor is determined as 30°C based on creep value and conductor characteristics, which will give some reference to the real projects.
Authors: Jean-Louis Chermant, F. Doreau, Jean Vicens
Authors: Vladimír Křístek, Lukáš Kadlec
Abstract: Due to increase of requirements on accuracy of structural analyses, practically applicable computational tools for reliable determination of the real structural performance of bridges are needed. A method is proposed for the true full 3D analysis which can be applied to achieve the real spatial behaviour of concrete bridge structures taking into account rheological phenomena and changes of structural systems. Particularly, the effects of shear lag, shear performance of webs of box girders, warping torsion, warping of cross-sections, distortional effects, state of stresses in the singular regions, the real prestress loss, etc., can be correctly determined. The method combines conventional approaches (based on the elementary beamtype assumptions) for calculating the time development of the internal forces due to rheological phenomena and changes in the structural system during construction and routine commercial FEM software intended for calculating spatial shell structures. The method is capable to give the true 3D prediction of structure behaviour by using only commercially available software. The primary advantage of the proposed method is its ease of application which allows the true 3D performance to be determined from simple calculations. The method offers the designers of concrete bridge girders an ideal design tool. The correct 3D simulation can lead to more efficient and economical designs.
Authors: Petr Král, Jiří Dluhoš, Pavel Peřina, Tomáš Barták
Abstract: Experiments were conducted to determine microstructure changes occurring during thermal exposure in metals processed by equal-channel angular pressing (ECAP). The ECAP pressing was performed at room temperature by route Bc. Static annealing and constant load creep tests in tension were conducted at 0.3-0.5 Tm. The microstructure was examined by scanning electron microscope combined with focus ion beam - TESCAN LYRA 3 equipped with electron back scatter diffraction (EBSD). It was found that creep behaviour is influenced by synergetic effect of additional creep mechanisms like grain boundary sliding, more intensive diffusion processes or recrystallization.
Authors: Wei Shen Zhu, Jian Hua Liu, Shu Cai Li
Abstract: A brief description is given to the visco-plastic constitutive model of 3-D FLAC software and some treating methods for the numerical analysis. The excavation steps and the exerting time of excavation loads are determined in the light of the real construction process. The rockmass mechanical parameters are determined according to back analysis of in-situ measured displacement data. The analysis results of displacement and stability of the opening complex surrounding rocks in the construction process and in a long period of time after excavation completion are given.
Authors: Osvaldo Vallati, Fabrizio Gara, Gianluca Ranzi, Graziano Leoni
Abstract: This paper presents a comparison of available numerical structural formulations for the short-and long-term analysis of composite beams with partial shear interaction. Four methods of analysis are considered and these include the finite difference method, the finite element method, the direct stiffness method and the exact analytical model. The results obtained using these formulations are compared qualitatively and their accuracy is estimated, adopting the exact analytical model as a benchmark reference with the objective of establishing the minimum spatial discretisations required to keep the error within an acceptable tolerance. These comparisons are carried out for two static configurations, i.e. simply-supported beams and propped cantilevers, from which the qualitative behaviour of these formulations in the modelling of continuous beams can also be deduced.
Authors: Danieli A.P. Reis, Carlos de Moura Neto, Antônio Augusto Couto, Cosme Roberto Moreira Silva, Francisco Piorino Neto, M.J.R. Barboza
Abstract: Thermomechanical and electrical properties of zirconia-based ceramics have led to a wide range of advanced and engineering ceramic applications like solid electrolyte in oxygen sensors, fuel cells and furnace elements and its low thermal conductivity has allowed its use for thermal barrier coatings for aerospace engine components. A comparison between CoNiCrAlY bond coat and zirconia plasma sprayed coatings on creep tests of the Ti-6Al-4V alloy was studied. The material used was commercial Ti-6Al-4V alloy. Yttria (8 wt.%) stabilized zirconia (YSZ) with a CoNiCrAlY bond coat was atmospherically plasma sprayed on Ti-6Al-4V substrates by Sulzer Metco Type 9 MB. Constant load creep tests were conducted on a standard creep machine in air on coated samples, at stress levels of 520 MPa at 500°C to evaluate the oxidation protection on creep of the Ti-6Al-4V alloy. Results indicate that the creep resistance of the ceramic coating was greater than metallic coating.
Authors: Wei Wang, Jun Lv, Hai Cheng Wang
Abstract: Based on the results obtained by the triaxial creep test, a creep-damage constitutive model for sandstone is presented by using the damage theory and by introducing the concept of “the whole process of damage” into Burgers creep model. The parameters of the model are determined by fitting the creep test data. The result shows that the proposed model can not only describe efficiently the variation of decay and steady creep under relatively low stress condition, but also give a satisfied representation of damage behavior in accelerated creep stage.
Authors: A. Hartmaier, Markus J. Buehler, Hang Gao
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