共查询到18条相似文献,搜索用时 187 毫秒
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为研究锈蚀钢筋力学性质的衰变规律,基于概率统计学理论,采用人工加速锈蚀法对五种直径的HRB400钢筋实施锈蚀处理,并利用除锈剂除锈后进行室内拉伸试验。结果表明,随着钢筋锈蚀程度的增大,钢筋的名义屈服强度、名义极限强度均呈线性退化规律,钢筋断后伸长率呈先急后缓退化,非线性变化规律明显;在相同锈蚀条件下,大直径钢筋的名义屈服强度、名义极限强度和断后伸长率的退化速度较快,但与小直径钢筋无显著统计学差异。研究成果可为已建混凝土结构的承载力、耐久性等服役效能评价提供理论依据,对结构的加固补强、工程续建等施工方案的制定有重要的参考价值。 相似文献
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为研究混杂纤维混凝土与锈蚀钢筋粘结性的关系,通过电化学加速锈蚀,获取4组不同钢筋锈蚀率(0~6.89%)的钢—聚乙烯醇纤维混凝土试件。采用中心拉拔试验,得到不同锈蚀率情况下钢筋与混杂纤维混凝土的粘结强度,分析锈蚀率、混杂纤维体积率对钢筋与混凝土粘结性能的影响,并根据试验结果提出了混杂纤维混凝土粘结强度系数和滑移值系数与钢筋锈蚀率之间的数学关系式。结果表明,在一定范围内混杂纤维体积率越大,钢筋与混凝土之间的粘结性能越好,粘结强度随着锈蚀率的升高呈现先增加后下降的趋势。 相似文献
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以驻马店未来科技城工程基础桩试验方案为例,基于钢筋混凝土有限元分离式模型及William-Warnke五参数混凝土强度准则,应用有限元分析软件ANSYS对形状优化后的复杂配筋静载试桩的桩帽进行了数值模拟分析。结果表明,桩帽的位移、混凝土强度、钢筋强度均满足要求;桩帽的最大位移发生在千斤顶作用位置;桩帽内环向钢筋的应力较大,桩帽设计时应适当增大环向钢筋的配筋率;桩帽裂缝主要出现在千斤顶作用面周边,可在千斤顶下部设置钢垫板,以避免裂缝的产生。 相似文献
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为研究新老混凝土中抗剪钢筋锈蚀的相关特性,采用通电加速锈蚀方法分析了设计锈蚀率分别为5%、10%条件下新老混凝土中抗剪钢筋的锈蚀特性,探究了不同位置处钢筋锈蚀的异同。结果表明,混凝土浇筑面锈蚀率大于非浇筑面;钢筋锈蚀率和锈蚀效率与混凝土强度呈正相关关系;设计锈蚀率10%较5%的锈蚀效果更好;新老混凝土结合面处钢筋锈蚀情况较其他地方严重。 相似文献
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TC4是钛合金中两相合金的典型代表,在航空领域的应用十分广泛,主要是用在制造压气机叶片、盘件、设备紧固件等方面。而随着TC4合金组织与性能的不断优化,其用途越来越宽泛,工业前景广阔。钛合金在使用过程中,热处理工艺是有效调整材料强塑比的主要方式,其中固溶处理与时效强化相结合,可以在很大程度上提高材料强度,并降低塑性。现阶段,我国对于TC4钛合金的高温性能、热温性能、蠕变性能等研究十分重视,但是,基于热处理工艺满足航空用TC4合金使用性能的相关探究却寥寥无几。因此,通过不同热处理制度在TC4合金组织与性能中的影响研究,得出结果,在固溶温度不断升高的趋势下,显微组织从两相区固溶转变成了单相区固溶,其中的σ1和σ2也显著提高了,断后伸长率与断面收缩率都在一定程度上有了缩减。而且在时效温度不断上升的趋势下,显微组织开始越来越均匀,其中α相的等轴化程度有所提升,而σ1和σ2都呈现下降趋势,断后伸长率与断面收缩率都逐渐升高。 相似文献
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工况下交联聚乙烯电缆绝缘材料的老化会导致其较预期相对较早达到寿命终点,威胁输电系统的可靠运行。采用热老化来模拟工况环境下电缆的老化过程,选取100 ℃、120 ℃和140 ℃和160 ℃ 4个不同的老化温度,在每个温度点选取6个老化阶段,研究不同老化温度和老化时间对XLPE电缆绝缘试样性能的影响。通过热重和拉伸测试研究电缆的热性能、机械性能及其结构随老化程度的变化,得到电缆绝缘试样的热老化活化能、起始分解温度、最快分解温度、终止分解温度、断裂伸长率和拉伸强度等参数。研究结果表明:活化能、起始分解温度、最快分解温度和断裂伸长率对电缆老化状态较为敏感;随着老化温度从100 ℃增加到160 ℃,这些参数均呈现先略微增大后迅速减小的趋势,说明XLPE电缆绝缘材料热老化在低温范围以结晶作用为主,而在高温范围以热裂解为主。 相似文献
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富春江水电站运行40多年,电站开关站混凝土构架出现混凝土剥蚀和裂缝。针对实际情况,对混凝土构架进行无损检测,检测内容包括凝土裂缝深度、混凝土强度、混凝土碳化深度、构架内部钢筋保护层厚度和构架内部钢筋锈蚀检测等,并根据检测的情况提出了补强加固方案。该技术对于水电站混凝土构架的检测和加固具有一定指导意义。 相似文献
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《International Journal of Hydrogen Energy》2020,45(15):9128-9136
Under the tensile loading, the damage of metals in the corrosive medium is the most destructive and harmful. In this study, the stress corrosion cracking behavior of H-charged high-strength steel in 3.5 wt% NaCl solution after electropulsing treatment was investigated. The experimental results from elongation, yield strength, fracture morphology, and polarization curves all demonstrate the positive effect of the pulsed processing, as it reduced the susceptibility of steel to stress corrosion cracking by removing hydrogen by electropulsing. The reduction in hydrogen content of the pulsed high–strength steels was attributed to electromigration and increased system free energy, which drove the hydrogen atoms in the steel to de–trap and reduced the susceptibility to stress corrosion cracking. 相似文献
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AbstractCarbon steel is one of the candidate overpack materials for geological disposal of high-level radioactive waste in Japan. Corrosion of carbon steel is classified into two types: general corrosion and localised corrosion. In this study, propagation of general and localised corrosion (pitting corrosion and crevice corrosion) were investigated by immersion tests of carbon steel under the aerobic conditions. The results of the immersion tests showed that the corrosion growth rate was strongly dependent on the environmental conditions and type of steel. However, the upper limit of the pitting factor, the ratio between the maximum corrosion depth and the average corrosion depth, was determined approximately using only average corrosion depth. Based on the experimental and literature data, an empirical model that predicts the maximum corrosion depth of an overpack from average corrosion depth was developed by applying the extreme value statistical analysis using the Gumbel distribution function. 相似文献
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Renchao Wei Xuedong Chen Zhibin Ai Youhai Jin 《International Journal of Hydrogen Energy》2018,43(18):9059-9067
Constant displacement loading tests using wedge opening loading specimens were carried out in aqueous hydrogen sulfide solution containing sodium chloride to investigate the susceptibility of stress corrosion cracking (SCC) of FV520B precipitation hardening martensitic stainless steel. Results of the SCC tests indicated that the stress corrosion critical stress intensity factor (KISCC) dramatically decreased in the corrosion medium investigated and decreased with the increasing of H2S concentration. Microstructures of fracture surfaces were analyzed using a scanning electron microscope (SEM) with an energy dispersive X-ray spectroscopy (EDS). The fracture surface was typical of sulfide stress corrosion fracture. In addition, large amount of intermittent arc-crack on the side surfaces around the tip of main crack formed even no main crack propagated.A sequentially coupling finite element analysis (FEA) program was utilized to simulate the stress field and calculate the diffused hydrogen concentration distribution of specimen exposed to the corrosion medium investigated. The FEA results indicated that corrosion pit affected the stress and diffusion hydrogen distribution around the corrosion pit where large stress gradients formed. Side surface cracks initiated from those corrosion pits and propagated under the synergy of stress and hydrogen. The effect of the corrosion pit on hydrostatic stress distribution was limited in superficial zone near the side surface, thus side surface cracks propagated along the hoop direction rather than along the direction of specimen thickness. Based on the morphology observation and FEA results, it can be concluded that the SCC mechanism of FV520B steel was hydrogen embrittlement mainly and combination of anodic dissolution. Simultaneously, corrosion pitting was the precondition of side surface crack formation while the stress induced hydrogen diffusion was the dominant factor. 相似文献
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A calcium chloride solution with a different extender, which is made up of either pure calcium chloride, calcium chloride with expanded graphite, or calcium chloride with activated carbon, acts differently on stainless steel. The mass ratio between calcium chloride with expanded graphite or activated carbon is almost 4∶1, which is demonstrated to be the optimum ratio. The experimental research in this paper reveals that, of the three solutions, which are pure calcium chloride, calcium chloride with expanded graphite, and calcium chloride with activated carbon, the strongest oxidation creation and pitting corrosion happened in the solution of calcium chloride with expanded graphite, the weakest oxidation creation happened in the solution of calcium chloride with activated carbon, and pitting corrosion was stronger than oxidation creation in the solution of pure calcium chloride. This paper gives the reasons for these phenomena. Furthermore, based on theory analysis, multiple means and approaches are provided to prevent stainless steel from further corroding. 相似文献
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AbstractThe Supercontainer design is the preferred option for the underground disposal of high level nuclear waste in Belgium. It consists of a carbon steel overpack surrounded by a thick concrete buffer. In this high alkaline environment and under normal conditions (without the ingress of aggressive species), the carbon steel overpack will be protected by a passive oxide film, which is believed to result in very low uniform corrosion rates. The backbone of the RD&D strategy, which aims to provide confidence that the integrity of the overpack will be maintained at least during the thermal phase, is based on demonstrating that each localised corrosion mechanism (e.g. pitting corrosion, crevice corrosion and stress corrosion cracking), other than uniform corrosion, cannot take place under the high pH conditions prevailing within the Supercontainer (the ‘exclusion principle’). This paper gives an overview of the status of the RD&D programme related to the anaerobic uniform corrosion of the carbon steel overpack. The outcome of the modelling efforts simulating the evolution of various parameters (temperature, pH, degree of saturation, corrosion potential and composition of aggressive species) that can potentially influence the corrosion processes, over geological timescales, is addressed. 相似文献
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Lv Xu Yuanyang Hu Liwei Wang Ruzhu Wang 《Frontiers of Energy and Power Engineering in China》2010,4(2):181-184
A calcium chloride solution with a different extender, which is made up of either pure calcium chloride, calcium chloride
with expanded graphite, or calcium chloride with activated carbon, acts differently on stainless steel. The mass ratio between
calcium chloride with expanded graphite or activated carbon is almost 4:1, which is demonstrated to be the optimum ratio.
The experimental research in this paper reveals that, of the three solutions, which are pure calcium chloride, calcium chloride
with expanded graphite, and calcium chloride with activated carbon, the strongest oxidation creation and pitting corrosion
happened in the solution of calcium chloride with expanded graphite, the weakest oxidation creation happened in the solution
of calcium chloride with activated carbon, and pitting corrosion was stronger than oxidation creation in the solution of pure
calcium chloride. This paper gives the reasons for these phenomena. Furthermore, based on theory analysis, multiple means
and approaches are provided to prevent stainless steel from further corroding. 相似文献