A lifing method based on R5 and viscoplasticity modelling and its application to turbine rotor under thermomechanical loading

Abstract

An integrated life assessment procedure for structures operating under thermomechanical loading has been developed. The methodology uses a viscoplasticity based framework combined with the R5 life assessment code. The viscoplastic constitutive model used for the stress-strain analysis is derived from the Chaboche-Lemaitre formulation that allows to directly obtain the required parameters for the R5 assessment as stress relaxation per cycle and the elastic follow-up factor. The R5 procedure is therefore significantly simplified. The proposed life assessment procedure is demonstrated on a martensitic steel (FV566) industrial gas turbine rotor under a typical start up -shut down operation. The effect of creep-fatigue interaction at different locations within the rotor structure is assessed and the remaining life at each location is calculated. A sensitivity study is performed at half load, which shows an increase in lifetime of the rotor.

Macro/micro Cyclic Constitutive Models and Their Application in Engineering Structures

“…SALEEB 等 [92] ，CHABOCHE 等 [93] ，KANG 等 [51] 和 YUAN 等 测的重要组成部分，受到了许多疲劳寿命领域研究 者的关注 [3] 。近些年来，随着计算机水平的高速发 展，研究者们逐步推进了宏观循环本构模型和晶体 塑性本构模型的工程应用，基于传统和新型的宏观 唯象和晶体塑性本构模型的疲劳寿命预测，成为失 效分析领域的研究热点。 基 于循环应力范围与塑性应变范围相关的循环本构方 程，采用有限元法模拟了汽轮机转子的蠕变-疲劳行 为，并耦合损伤分析了转子在蠕变疲劳载荷下的损 伤 演 化 过 程 。 WANG 等 [103] 提 出 弹 黏 塑 性 CHABOCHE-NAUAIHAS-OHNO-WANG 本构模型 并进行有限元实现，分析和模拟了某汽轮机转子的 多轴蠕变-疲劳行为，发现蠕变损伤主导了该转子应 力集中区域的蠕变-疲劳损伤。FENG 等 [104] 基于经 典的 CHABOCHE 热黏塑性本构模型，描述了汽轮 机焊接转子结构的残余应力在启停疲劳条件下的松 弛和应力重分布规律，分析了该行为对转子构件的 寿命影响。BONETTI 等 [105] 同样基于 CHABOCHE- 建立了镍基合金 C263 的多晶塑性有 限元模型，考虑了晶粒形貌和晶体取向等微结构特 征。同时，利用累积塑性滑移作为疲劳指示因子， 很好地预测了均匀模型的高低周疲劳萌生寿命。 CHEN 等 [109] 指出累积滑移和储存能量密度是识别…”