ASME Code Case 2843技术基础分析

ASME Code Case 2843(以下简称为“案例”)提供了针对高温工况和交变载荷下承受蠕变和疲劳损伤交互作用的受压元件进行评定的方法。在应用该案例方法的过程中,如不能理解这些方法的技术基础,则可能造成评定结果的不安全。案例中所提出的蠕变-疲劳损伤评定方法主要利用线弹性分析得到的结果对弹塑性材料构成的受压元件进行评定。整套方法包括载荷控制极限的判定、应变控制极限的判定以及蠕变-疲劳损伤极限的判定三个步骤,每个步骤中采用的方法均依据多年来有关研究人员发表文献中的理论和实验结果。拟对案例中所采用方法的技术基础进行分析,为工程中应用案例的方法对承受高温和交变载荷作用的压力容器进行设计提供一定的参考。

Fatigue Verification of Class 1 Nuclear Power Piping According to ASME BPV Code

In this paper, fatigue verification of Class 1 nuclear power piping according to ASME Boiler ＆ Pressure Vessel Code, Section III, NB-3600, is addressed. Basic design requirements and relevant verification procedures using Design-By-Analysis are first reviewed in detail. Thereafter, a so-called simplified elastic-plastic discontinuity analysis for further verification when the basic requirements found unsatisfactory is examined and discussed. In addition, necessary computational procedures for evaluating alternating stress intensities and cumulative damage factors are studied in detail. The authors＇ emphasis is placed on alternative verification procedures, which do not violate the general design principles upon which the code is built, for further verification if unsatisfactory results are found in the simplified elastic-plastic analysis. An alternative which employs a non-linear finite element computation and a refined numerical approach for re-evaluating the cumulative damage factors is suggested. Using this alternative, unavoidable plastic strains can be correctly taken into account in a computationally affordable way, and the reliability of the verification will not be affected by uncertainties introduced in the simplified elastic-plastic analysis through the penalty factor Ke and other simplifications.

More on Fatigue Verification of Class 1 Nuclear Power Piping According to ASME BPV Code

Fatigue verification of Class 1 nuclear power piping according to ASME Boiler and Pressure Vessel Code, Section III, NB-3600, which is often discussed in connection to power uprate and life-extension of aging reactors in recent years, is dealt with. Key parameters involved in the fatigue verification, e.g., the alternating stress intensity Salt, the penalty factor Ke and the cumulative damage factor U, and relevant computational procedures applicable for the assessment of low-cycle fatigue failure using strain-controlled data, are particularly addressed. A so-called simplified elastic-plastic discontinuity analysis for alternative verification when fatigue requirements found unsatisfactory, and the procedures provided in NB-3600 for evaluating the alternating stress intensity S,j,, are reviewed in detail. An in-depth discussion is given to alternative procedures suggested earlier by the authors using nonlinear finite element analyses, which uses a nonlinear finite element analysis for directly determining the alternating stress, thus eliminating uncertainties resulted from the use of the penalty factor Ke. Using this alternative, unavoidable plastic strains can be correctly taken into account in a computationally affordable way, and the reliability of the verification will not be affected by uncertainties introduced in the simplified elastic-plastic analysis.

考虑蠕变作用的2.25Cr-1Mo-V钢加氢反应器设计方法

以某台2.25Cr-1Mo-V钢加氢反应器为例,从工程角度介绍现行设计方法与ASME Code Case 2605-3在反应器设计中的应用,说明过去留有一定余量的设计是设备安全运行的原因之一。探讨了压力和温度载荷对蠕变参数的影响,其中压力对三轴度系数影响较大,而温度对蠕变松弛影响显著。最后提出在业主非强制要求进行完整分析的前提下,ASME Code Case 2605-3在工程上的简化应用。