内压条件P92钢的多轴蠕变实验及模型研究

发布时间：2018-03-22 12:14

  本文选题：P92钢　切入点：多轴蠕变　出处：《华北电力大学(北京)》2017年硕士论文　论文类型：学位论文

【摘要】：随着环境逐渐恶化和能源格局的变迁,国家对发电企业的节能减排能力提出了更高的要求,发展高蒸汽参数的高效超超临界机组成为未来火电厂建设和改造的目标。随着蒸汽参数的提高,电站锅炉高温受热面对材料的性能提出了进一步的要求,蠕变性能作为材料的特性之一是影响高温高压管道寿命的重要因素。目前,国内外的许多学者对P92等高温受热面钢材进行了蠕变性能的研究,这些研究多是在单轴蠕变试验的基础上进行,考虑到电厂实际运行的状况,部件多处于多向应力状态,随即又进行了大量缺口试样的多轴蠕变试验。尽管缺口试样可以在缺口处形成一定的多轴应力状态,但是所形成的应力多轴度在缺口处分布不均程度大,可控性差,对于探究多轴应力状态下材料的蠕变寿命未能提供充分有效的实验结果,所以在单轴和缺口试验的基础上,本文以P92钢为研究对象,在650℃的条件下,进行了内压条件下的蠕变试验实验台搭建,设计适当的实验参数并与单轴及缺口试验对比,分析其轴向和环向的蠕变发展。观察内压试样的断口形貌和微观组织并与单轴和缺口试验结果对比,得出内压条件下的多轴蠕变规律。在试验结果的基础上,建立耦合损伤参数的K-R蠕变模型,通过单轴蠕变试验结果拟合得出相关参数,结合内压实验结果分析等效应力、第一主应力、应力多轴度和损伤随时间的分布和演变。利用有限元分析多轴度因子和内压管几何尺寸条件改变对内压条件下多轴试验结果的影响,并在有限元分析的基础上提出内压厚壁管道的寿命评估方法。结果表明:内压条件下的蠕变试验形成的应力多轴度范围在1/3到2/3之间,在相近应力水平下内压试样的寿命小于单轴和缺口试样,与缺口呈现的缺口增强效应相反。由于多轴应力对空洞生长的约束作用,内压试样的应变值介于单轴和缺口试样之间。内压试样断裂后的断口形貌韧窝较浅,呈准解离特征,微观形貌下观察到的孔洞和裂纹多分布于与轴向应力垂直方向的晶界及板条界上。在损伤模型的基础上利用有限元分析得出的断裂应力可以在一定范围内预测内压管道的寿命。
[Abstract]:With the gradual deterioration of the environment and the change of energy pattern, the state has put forward higher requirements for the energy saving and emission reduction capacity of power generation enterprises. The development of high-efficiency ultra-supercritical units with high steam parameters has become the goal of construction and transformation of thermal power plants in the future. With the increase of steam parameters, the high temperature heating surfaces of power plant boilers have put forward further requirements for the performance of materials. As one of the characteristics of materials, creep property is an important factor affecting the life of high temperature and high pressure pipeline. At present, many scholars at home and abroad have studied the creep property of high temperature heating surface steel such as P92. Most of these studies are carried out on the basis of uniaxial creep tests. Considering the actual operation of the power plant, most of the components are in multidirectional stress state. The multiaxial creep tests of a large number of notched specimens were carried out immediately. Although the notched specimens can form a certain state of multiaxial stress at the notch, the stress multiaxial degree formed by the notched specimen has a large uneven distribution at the notch, and the controllability is poor. The creep life of the material under multiaxial stress can not provide sufficient and effective experimental results. Therefore, on the basis of uniaxial and notch tests, this paper takes P92 steel as an object of study at 650 鈩，

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