Life Prediction of Power Plant Components

近年来，9-12%铬强化铁素体(CSEF)钢的蠕变强度得到了长足的发展。传统上，在电厂构件的材料开发中，蠕变延性作为抗损伤性能受到的关注较少。然而，由于低损伤容忍度导致的灾难性故障的风险是一个真正的挑战，特别是在存在机械和冶金约束的情况下。此外，由于电厂主蒸汽管道的启动和关闭等循环操作的频率越来越高，材料的低周蠕变疲劳破坏已成为一个重要的问题。PHD项目的目的是通过一个综合的理论、实验和计算程序，研究CSEF电厂钢在实际工厂负荷循环下的蠕变和蠕变疲劳行为。预测部件的使用寿命将与自动化现有的电力、天然气和其他能源矢量、先进控制和仪器仪表的研究领域保持一致。具体目标包括：1.数据采集和分析以及对现有模型和评估程序的文献综述。候选电厂钢/焊缝(可能为MARBN)低周疲劳性能和微观组织特征的实验研究。建立了考虑循环软化和损伤的PM、WM和HAZ循环粘塑性模型。利用工厂运行数据，并考虑典型工厂部件几何形状和工厂操作员要求进行状态评估，应用该模型进行部件评估。探索造成损坏的早期寿命因素，如严重的工厂运行、糟糕设计的影响和蠕变脆性。将使用完善的设施进行高温力学测试和物理表征。理论和建模工作将通过用户自定义子程序使用有限元程序ABAQUS进行。

Over the years, significant development has been made on the 9-12%Cr creep strength enhanced ferritic (CSEF) steels. Traditionally, in material development for power plant components, creep ductility, which can be treated as resistance to damage, has received much less attention. However, the risk of catastrophic failure due to low damage tolerance is a real challenge, in particular, in the situation where mechanical and metallurgical constraints are present. In addition, due to the increasing frequency of cyclic operations, i.e. starts up and shut downs for main steam pipelines of power plants, low cycle creep fatigue failure due to low ductility of the materials has become an important concern.The aim of the PhD project is to investigate creep and creep fatigue behaviour which takes into account the variable ductility for CSEF power plant steels subject to realistic plant loading cycles, through a comprehensive theoretical, experimental and computational programme. Predicting the useful life of components will align with the research area of automating existing electricity, gas and other energy vectors advanced controls, and instrumentation.Specific objectives include:1. Data acquisition and analysis and literature review on the currently available models and assessment procedure.2. Experimental investigation of LCF behaviour and microstructure characterization of the candidate power plant steel/weld (possibly MARBN).3. Development of a cyclic visco-plasticity model for PM, WM and HAZ which takes into account the cyclic softening and damage.4. Application of the model for component assessment using plant operational data and considering typical plant component geometries and plant operator requirements for condition assessment.5. Exploring early life contributors to damage such as severe plant operation, impact of poor design and creep brittle properties.High temperature mechanical testing and physical characterization will be carried out using well-established facility. The theoretical and modelling work will be carried out using finite element package ABAQUS through user defined subroutines.