Modelling Creep and Creep-Fatigue Damage for CSEF Power Plant Steels

在目前的市场条件下，联合循环燃气轮机(CCGT)工厂现在正在考虑双两班制运行，因此每年可能会有600多次开工。减少压力系统检查和维修的压力继续增加，最近的发电能力拍卖结算价格与前几年相比大幅下降。对于大型发电设施的运营商来说，关键考虑的是整个生命周期的收入回报，它将指导新工厂建设的决策和对当前运营的工厂的任何资本投资。在此基础上，显然需要有效的寿命预测和状态监测工具来支持供应链(设计者、制造者、操作员和技术服务提供商)。多年来，9-12%铬蠕变强度增强铁素体(CSEF)钢的研究取得了重大进展。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，由材料的低延性引起的低周蠕变疲劳失效已成为一个重要的问题。拟议的项目的目的是通过综合的理论、实验和计算程序来研究CSEF电厂钢的蠕变和蠕变疲劳行为。具体目标包括：1.数据采集/分析和对现有模型和评估程序的严格审查。通过实验/物理方法了解具有不同初始延性的CSEF电厂钢的蠕变和蠕变疲劳行为。建立了考虑延性变化的蠕变和蠕变疲劳模型。使用现代CCGT工厂的运行数据进行部件评估的模型的应用。高温机械测试和物理表征将使用完善的设施进行。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。

The current market conditions are such that combined cycle gas turbine (CCGT) plants are now considering double two-shift operation, so potentially accruing upwards of 600 starts per year. The pressure to reduce the extent of pressure system inspections and repairs continues to increase, with the most recent capacity auction clearing prices for generation showing a significant reduction when compared to previous years. For operators of large generation facilities the key consideration is the through life revenue return, which will guide decisions on new plant builds and any capital investments on plant currently operating. On this basis the need for effective life prediction and condition monitoring tools to support the supply chain (designer, fabricator, operator and technical service provider) is evident.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 proposed project is to investigate creep and creep fatigue behaviour which takes into account the variable ductility for CSEF power plant steels, through a comprehensive theoretical, experimental and computational programme.Specific objectives will include:1. Data acquisition/analysis and critical review on the currently available models and assessment procedure.2. Experimental/physical understanding of creep and creep fatigue behaviour of CSEF power plant steels with different initial ductility.3. Development of a novel creep and creep fatigue model which takes into account the variable ductility.4. Application of the model for component assessment using the operational data from a modern CCGT plant.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.