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911.
针对CO2腐蚀环境下P110套管材料性能动态变化的难题,基于腐蚀实验与拉伸实验,对含腐蚀损伤的P110套管进行了力学性能分析。根据现场资料对钻井液注入CO2配置腐蚀液,将腐蚀后试件与现场失效套管的腐蚀产物进行EDS能谱分析对比,确定了腐蚀液的适用性。设置固定井深,在100℃高温时不同的腐蚀实验周期内,将所得的含腐蚀损伤试件进行质量损失测试及拉伸实验,分析了材料力学性能的变化。由MTS液压式万能试验机得出应力-应变曲线,并拟合得到了等效屈服强度变化公式及等效抗拉强度变化公式。结果表明:套管试样腐蚀后的屈服强度和抗拉强度随着失重率增大而减小,当套管试样经腐蚀后失重率低于15%时,材料的力学性能,如等效屈服强度和等效抗拉强度随失重率的增加会以较大幅度降低;而当试样失重率大于15%时,随着失重率的增加,等效屈服强度急剧减小,等效抗拉强度则以较为平缓的趋势降低。 相似文献
912.
Dmitry G. Luchinsky Halyna Hafiychuk Vasyl Hafiychuk Kenta Chaki Hiroya Nitta Taku Ozawa Kevin R. Wheeler Tracie J. Prater Peter V. E. McClintock 《Journal of polymer science. Part A, Polymer chemistry》2020,58(15):2051-2061
We consider an atomistic model of thermal welding at the polymer-polymer interface of a polyetherimide/polycarbonate blend, motivated by applications to 3D manufacturing in space. We follow diffusion of semiflexible chains at the interface and analyze strengthening of the samples as a function of the welding time tw by simulating the strain–stress and shear viscosity curves. The time scales for initial wetting, and for fast and slow diffusion, are revealed. It is shown that each component of the polymer blend has its own characteristic time of slow diffusion at the interface. Analysis of strain–stress demonstrates saturation of the Young's modulus at tw = 240 ns, while the tensile strength continues to increase. The shear viscosity is found to have a very weak dependence on the welding time for tw > 60 ns. It is shown that both strain–stress and shear viscosity curves agree with experimental data. 相似文献
913.
Over the past 2 decades, tight restriction has been imposed on strength criteria of concrete by the combination of plasticity and damage in one theory. The present study aims at constructing plastic/damage loading functions for elastoplastic damage models for concrete that can perform more satisfactorily in 3D stress states. Numerous strength criteria of concrete are reorganized according to their simplest representations as Cartesian, cylindrical, mixed cylindrical-Cartesian, and other forms, and the homogeneity of loading functions discussed. It is found that under certain supplementary conditions from physical meanings, an unambiguous definition of the cohesion in a strength criterion, which is demanded in an elastoplastic damage model, is usually available in an explicit or implicit form, and in each case the loading function is still homogeneous. To apply and validate the presented theory, we construct the respective homogeneous damage and plastic loading functions and implant them into some widely used elastoplastic damage models for concrete, and their performances in triaxial compression prove to have improved significantly. 相似文献
914.
光学窗口的强度分析是光电设备设计的重要依据,而现有文献中只提供材料泊松比为0.3的简化的计算公式,而针对不同泊松比的简支矩形板强度原始计算公式以复杂的级数形式表示不方便直接应用,为了方便设计者得到准确的强度理论分析结果,提供了一种简单的方法推导出适用于不同泊松比的简支式矩形保护窗口的强度简化计算公式,并验证了该方法推导... 相似文献
915.
《Particuology》2014
Approximately 70% of the applied urea fertilizer may be lost into the environment. This loss is due to leaching, decomposition and ammonium volatilization in soil, water and air. Through coating, the slow release technology can be used to reduce losses and to increase the fertilizer efficiency. Sulfur has been used as a coating material, but the coating cracks easily because of its friability, sometimes being peeled off from the urea surface. In this study, four types of materials, namely, gypsum, cement, sulfur and zeolite, were mixed and used as coating materials to search for the most effective and cheap coating materials. The primary reasons for selecting these materials were improving fruit quality and preventing plant diseases, providing a plant nutrient, increasing soil fertility and water retention. The materials were also selected based on their availability, processiblity and price. The effects of the coating materials, thickness, drying time, sieving and sealant on the crushing strength and dissolution rate of urea were investigated. Coated urea with the same proportion of gypsum–sulfur exhibited high crushing strength and lower dissolution rate. However, the performance was further enhanced by applying molten paraffin wax on the hot urea surface. SEM images demonstrated that the micro-structure of gypsum–sulfur coated urea after sieving resulted in a smoother coated layer. The efficiency of the coated urea was improved by 26% using gypsum–sulfur (20% total coating), 3% paraffin wax and sieving the coating materials before application. 相似文献
916.
The mechanical properties of bicrystalline graphene nanoribbons with various tilt grain boundaries (GBs) which typically consist of repeating pentagon–heptagon ring defects are investigated based on the method of molecular structural mechanics. The GB models are constructed via the theory of disclinations in crystals, and the elastic properties and ultimate strength of bicrystalline graphene nanoribbons are calculated under uniaxial tensile loads in perpendicular and parallel directions to grain boundaries. The dependence of mechanical properties is analyzed on the chirality and misorientation angles of graphene nanoribbons, and the experimental phenomena that Young's modulus and ultimate strength of bicrystalline graphene nanoribbons can either increase or decrease with the grain boundary angles are further verified and discussed. In addition, the influence of GB on the size effects of graphene Young's modulus is also analyzed. 相似文献
917.
Moritz T. Lessmann Aida Calvo Christopher D. Hardie Michael Porton Nerea Ordás Carmen García-Rosales 《哲学杂志》2016,96(32-34):3570-3585
The brittle fracture strength of a self-passivating W-Cr10-Ti2 alloy (in wt.%) was measured through un-notched cantilever bending at the microscopic scale. The material behaved purely elastic and fractured catastrophically in an unstable fashion. An average nominal strength of 5.9 GPa was measured. The scatter in strength was shown to be significantly higher than the sum of all random errors indicating an inherent variability of the material’s strength. The measurements from 28 tests followed a Weibull distribution with a modulus of m = 12. Results from a size effect study at the microscopic scale were successfully predicted through Weibull scaling. Extrapolation into the macroscopic range overestimated the measured three-point bend strength, which is likely due to the presence of large-scale heterogeneities. The test technique sampled a material thickness of only several micrometres and is hence suitable for future ion irradiation studies. 相似文献
918.
Shijun Liang Wenfang Xie H.A. Sarkisyan A.V. Meliksetyan Huaya Shen 《Superlattices and Microstructures》2012
Optical properties of a nanoring with Winternitz–Smorodinsky confinement potential in the presence of an external magnetic field have been studied theoretically. Our results demonstrate that energy, oscillator strength and the linear, nonlinear and total absorption are strongly affected by size of the nanoring. Also, we found that magnetic field has little influence on energy difference, oscillator strength and optical absorption of the nanoring. 相似文献
919.
Sergio Enrique Moya Joseba Irigoyen 《Journal of polymer science. Part A, Polymer chemistry》2013,51(14):1068-1072
The combination of Quartz Crystal Microbalance and ellipsometry to quantify polyelectrolyte brush hydration and how this impacts on the study of brush collapse is discussed here. Recent articles study collapse after quantifying hydration of poly (2-methacryloyloxy ethyl trimethyl ammonium chloride) (PMETAC) and poly(potassium sulfo propyl methacrylate). Water lost increases with ionic strength but only a 50% of their water content is lost at 1 M NaCl. For PMETAC brushes the exchange of Cl− by ClO4− is more effective, causing 50% lost at 0.05 M. The hydration and water lost for PMETAC brushes synthesized from thiol monolayers with variable density of initiators from 1 to 100% show that the freely entrapped water of the brushes is around a 10%. Irrespectively of initiator percentage the brush does not lose at 1 M NaCl more than 50% of the original water content. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1068–1072 相似文献
920.
《Composite Interfaces》2013,20(4):197-211
The experimental technique of single-fiber electromechanical pull-out testing was introduced and used to study the interface between steel fiber and cement. The technique involves measuring both the contact electrical resistivity between fiber and matrix and the shear bond strength in a fiber-matrix interface sample. Samples that are identically prepared differ in contact resistivity and bond strength, which correlate. The correlation allows determination of even small differences in bond strength due to differences in sample preparation conditions, such as fiber surface treatment, cement curing age and admixtures to the cement paste. It also gives information on the structure of the interface and allows the bond strength to be non-destructively determined by measuring the contact resistivity. 相似文献