Prediction of Stress Relaxation in Power Plant Components Based on a Constitutive Model

2017 ◽  
Author(s):  
Y. Kostenko ◽  
K. Naumenko
Keyword(s):  
Power Plant ◽  
Stress Relaxation ◽  
Constitutive Model ◽  
Evolution Equations ◽  
Material Behavior ◽  
Assessment Procedure ◽  
Reliable Prediction ◽  
Inelastic Material ◽  
Plant Components

Many power plant components and joint connections are subjected to complex thermo-mechanical loading paths under severe temperature environments over a long period. An important part in the lifetime assessment is the reliable prediction of stress relaxation using improved creep modeling to avoid possible integrity or functionality issues and malfunction in such components. The aim of this work is to analyze the proposed constitutive model for advanced high chromium steels with the goal of predicting stress relaxation over the long term. The evolution equations of the constitutive model for inelastic material behavior are introduced to account for hardening and softening phenomena. The material properties were identified for 9–12%CrMoV steels in the creep range. The model is applied to the stress relaxation analysis of power plant components. The results for long-term assessment, which are encouragingly close to reality, will be presented and discussed. An outlook on further developments of the model and assessment procedure is also provided.

A Unified Constitutive Model With Optimized Parameters for Base and Diffusion Bonded Alloy 800H

2020 ◽  
Author(s):  
Heramb P. Mahajan ◽  
Tasnim Hassan
Keyword(s):  
Elevated Temperature ◽  
Power Plant ◽  
Nuclear Power Plant ◽  
Constitutive Model ◽  
Nuclear Power ◽  
Parameter Determination ◽  
Alloy 800H ◽  
Inelastic Analysis ◽  
Creep Fatigue ◽  
Plant Components

Abstract Current ASME Section III, Division 5 code provides elastic, simplified inelastic and inelastic analysis options for designing nuclear power plant components for elevated temperature service. These analyses methods may fail to capture the complex creep-fatigue response and damage accumulation in materials at elevated temperatures. Hence, for analysis and design of the nuclear power plant components at elevated temperature, a full inelastic analysis that can simulate creep-fatigue responses may be needed. Existing ASME code neither provides guidelines for using full inelastic analysis nor recommends the type of constitutive model to be used. Hence, a unified rate-dependent constitutive model incorporating a damage parameter will be developed, and its parameters for base metal will be determined. In addition, a full inelastic analysis methodology using this model to analyze the creep-fatigue performance of components for nuclear power applications will be developed. Base metal 800H (BM800H) data are collected from literature to determine constitutive material model parameters. The parameter determination methodology for a constitutive model is discussed. The optimized parameter set for BM 800H at different temperatures will be presented in the paper. Recommendations are provided on the constitutive model selection and its parameter determination techniques. In the future, this work will be continued for diffusion bonded Alloy 800H (DB800H) material, and obtained parameters will be compared.

New methodology for long term creep data generation for power plant components

2007 ◽  
Vol 2 (2) ◽  
pp. 84-88 ◽  
Author(s):  
B. Wilshire ◽  
P. J. Scharning ◽  
R. Hurst
Keyword(s):  
Power Plant ◽  
Data Generation ◽  
Creep Data ◽  
Term Creep ◽  
Plant Components

Probabilistic Life Assessment Method of Low Cycle Fatigue for Power Plant Components

2003 ◽  
Vol 17 (08n09) ◽  
pp. 1704-1710
Author(s):  
Myung Soo Kang
Keyword(s):  
Power Plant ◽  
Low Cycle Fatigue ◽  
Operating Time ◽  
Assessment Method ◽  
Life Assessment ◽  
Assessment Procedure ◽  
Cycle Fatigue ◽  
Inspection Planning ◽  
Structural Failure ◽  
Plant Components

This study focuses on the probabilistic analysis method to the determination of low cycle fatigue life for power plant components. The analysis incorporates standard life assessment modeling techniques used in the determination analysis of the low cycle fatigue. The probabilistic life assessment is developed to increase the reliability of life assessment. A probabilistic life assessment procedure can provide the engineer with the probability of structural failure as a function of operating time given the uncertainties in the input data. The probabilistic life assessment involves some uncertainties, for example, initial crack size, aspect ratio, crack initiation time, crack location, structural geometry, material properties, and loading condition, and a triangle distribution function is used for random variable generation. The resulting information provides the engineer with an assessment of the probability of structural failure. This information can form the basis of inspection planning and retirement-for-cause decisions. This study forms basis of the probabilistic life assessment technique and will be extended to other damage mechanisms.

Robust Methods for Creep Fatigue Analysis of Power Plant Components Under Cyclic Transient Thermal Loading

2013 ◽  
Author(s):  
Yevgen Kostenko ◽  
Henning Almstedt ◽  
Konstantin Naumenko ◽  
Stefan Linn ◽  
Alfred Scholz
Keyword(s):  
High Temperature ◽  
Power Plant ◽  
Constitutive Model ◽  
Thermal Loading ◽  
Hold Time ◽  
Local Stress ◽  
Life Assessment ◽  
Heat Transfer Analysis ◽  
Turbine Component ◽  
Plant Components

The aim of this paper is to apply robust mechanisms-based material laws to the analysis of typical high-temperature power plant components during an idealized start-up, hold time and shut-down sequence under a moderate temperature gradient. Among others a robust constitutive model is discussed, which is able to reflect inelastic deformation, hardening/recovery, softening and damage processes at high temperature. The model is applied for a creep analysis of advanced 9–12%CrMoV heat resistant steels and calibrated in particular case against experimental data for 10%CrMoV steel type. For a steam temperature profile transient heat transfer analysis of an idealized steam turbine component is performed providing the temperature field. From the subsequent structural analysis with the inelastic constitutive model local stress and strain state variations are obtained. As an outcome a multi-axial thermo-mechanical fatigue (TMF) loading loop for one or several loading cycles can be generated. They serve as input for a fatigue life assessment based on the generalized damage accumulation rule, whose results come close to reality. In addition, the accuracy of a simplified method which allows a rapid estimation of notch stresses and strains using a notch assessment rule (NAR) [1] based on Neuber approach is examined.

Human reliability in non-destructive inspections of nuclear power plant components: modeling and analysis

2019 ◽  
Vol 7 (2B) ◽  
Author(s):  
Vanderley Vasconcelos ◽  
Wellington Antonio Soares ◽  
Raissa Oliveira Marques ◽  
Silvério Ferreira Silva Jr ◽  
Amanda Laureano Raso
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Human Factors ◽  
Nuclear Power ◽  
Power Plants ◽  
Failure Modes ◽  
Cooling System ◽  
Human Reliability ◽  
Non Destructive ◽  
Plant Components

Non-destructive inspection (NDI) is one of the key elements in ensuring quality of engineering systems and their safe use. This inspection is a very complex task, during which the inspectors have to rely on their sensory, perceptual, cognitive, and motor skills. It requires high vigilance once it is often carried out on large components, over a long period of time, and in hostile environments and restriction of workplace. A successful NDI requires careful planning, choice of appropriate NDI methods and inspection procedures, as well as qualified and trained inspection personnel. A failure of NDI to detect critical defects in safety-related components of nuclear power plants, for instance, may lead to catastrophic consequences for workers, public and environment. Therefore, ensuring that NDI is reliable and capable of detecting all critical defects is of utmost importance. Despite increased use of automation in NDI, human inspectors, and thus human factors, still play an important role in NDI reliability. Human reliability is the probability of humans conducting specific tasks with satisfactory performance. Many techniques are suitable for modeling and analyzing human reliability in NDI of nuclear power plant components, such as FMEA (Failure Modes and Effects Analysis) and THERP (Technique for Human Error Rate Prediction). An example by using qualitative and quantitative assessesments with these two techniques to improve typical NDI of pipe segments of a core cooling system of a nuclear power plant, through acting on human factors issues, is presented.

scholarly journals Effect of long term aging on Microstructure and precipitates of valve bolts in power plant

2021 ◽  
Vol 1802 (2) ◽  
pp. 022038
Author(s):  
Jiawei Wang ◽  
Qingsong Li ◽  
Xiufang Gong ◽  
Wensheng Yang ◽  
Tianjian Wang ◽  
...  
Keyword(s):  
Power Plant
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