Stochastic Modeling of Fatigue Crack Damage for Risk Analysis and Remaining Life Prediction

1999 ◽  
Vol 121 (3) ◽  
pp. 386-393 ◽  
Author(s):  
Asok Ray
Keyword(s):  
Fatigue Crack ◽  
Probability Distribution Function ◽  
Life Prediction ◽  
Power Plants ◽  
Damage Model ◽  
Metallic Materials ◽  
Remaining Life ◽  
Wiener Integral ◽  
Model Predictions ◽  
Complex Mechanical Systems

This paper presents a stochastic model of fatigue crack damage in metallic materials that are commonly encountered in structures and machinery components of complex mechanical systems (e.g., aircraft, spacecraft, and power plants). The constitutive equation of the damage model is based on the physics of fracture mechanics and is validated by Karhunen-Loe`ve analysis of test data. The (nonstationary) probability distribution function (PDF) of fatigue crack damage is generated in a closed form without numerically solving stochastic differential equations in the Wiener integral or Itoˆ integral setting. The crack damage model thus allows real-time execution of decision algorithms for risk assessment and life prediction on inexpensive platforms such as a Pentium processor. The model predictions are in close agreement with experimental data of fatigue crack growth statistics for 2024-T3 and 7075-T6 aluminum alloys.

scholarly journals Uncertainty Modeling of Fatigue Crack Growth and Probabilistic Life Prediction for Welded Joints of Nuclear Stainless Steel

Materials ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3192 ◽  
Author(s):  
Haijun Chang ◽  
Mengling Shen ◽  
Xiaohua Yang ◽  
Junxia Hou
Keyword(s):  
Stainless Steel ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Crack Propagation ◽  
Welded Joints ◽  
Life Prediction ◽  
Power Plants ◽  
Test System

Welded joints are widely used in the pipeline connection of nuclear power plants. Defects in these joints are an important factor leading to the failure of welded joints. It is critical to study the fatigue crack growth and life prediction methods for the welded joints with defects, to reduce their likelihood. In this paper, we present our study of the uncertainty of fatigue crack propagation and probabilistic life prediction for welded joints of nuclear stainless steel. The standard compact tension (CT) specimens were fabricated according to the American Society for Testing and Materials (ASTM) standard. Fatigue crack propagation tests with different stress ratios were performed on CT specimens, using the Mei Te Si (MTS) fatigue test system. A fatigue crack propagation rate model considering the uncertainty of material parameters, and based on the Paris formula and crack propagation experimental data, was established. A probabilistic life prediction method based on Monte Carlo simulation was developed. The fatigue crack propagation prediction result of a CT specimen was compared with the actual tested result, to verify the effectiveness of the proposed method. Finally, the method was applied to an embedded elliptical crack in welded joints of nuclear stainless steel, to predict the fatigue crack growth life and evaluate the reliability.

Damage Evaluation and Life Extension of Structural Components

1986 ◽  
Vol 108 (3) ◽  
pp. 241-248 ◽  
Author(s):  
L. F. Coffin
Keyword(s):  
Structural Damage ◽  
Life Prediction ◽  
Nuclear Power ◽  
Power Plants ◽  
Past History ◽  
Life Extension ◽  
Remaining Life ◽  
Structural Components ◽  
Damage State ◽  
Critical Elements

This paper describes an approach to life prediction in which critical elements of major structural components are continuously monitored by appropriate damage indicators for structural damage, and, based on the indicated damage state, an on-line assessment is made of the remaining life. Concurrently alternative corrective measures can then be assessed and, if the life has been found wanting, appropriate actions taken. The process is viewed as a continuous one whereby the current remaining life of critical elements is known as the plant ages. The need for applying such procedures becomes increasingly important as some of our major structures approach their design life and concerns arise regarding retirement and replacement versus life extension. Important elements of this approach include definitions of damage, appropriate damage monitors, damage assessment, life prediction, and conseqeunces of corrective action. This paper treats these elements in the context of past history and current programs associated with pipe cracking in nuclear power plants.

Effects of Load Sequence on Fatigue Crack Growth in Pressure Vessels

2010 ◽  
Vol 160-162 ◽  
pp. 1217-1222 ◽  
Author(s):  
Shahrum Abdullah ◽  
S.M. Beden ◽  
Ahmad Kamal Ariffin ◽  
Zulkifli Mohd Nopiah
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Test Data ◽  
Life Prediction ◽  
Power Plants ◽  
Pressure Vessels ◽  
Low Alloy Steels ◽  
Variable Amplitude

Low alloy steels such as ASTM A508 and A533 and their equivalent materials have been extensively applied in fabricating pressure vessels due to their relatively excellent mechanical properties and moderately good weldability. The integrity of such materials governs the safety of the power plants. These vessels mainly are subjected to random loading in service and the load cycle interactions can have a significant effect in fatigue crack growth. Studying of fatigue crack growth rate and fatigue life calculation under spectrum loading is important for the reliable life prediction of vessels. Many models have been proposed, but as yet no universal model exists. In this paper, a fatigue life predicted under various load spectra, using three different fatigue crack growth models namely the Austen, modified Forman and NASGRO models. These models are validated with fatigue crack growth test data under various variable amplitude loadings. This application is performed with aids of three-point bend specimens. The results show clearly the load sequences effect and the predicted results agree with some discrepancies between the different models as well as with the test data. Neglecting, the cycle interaction effects in fatigue calculation under variable amplitude loading lead to invalid life prediction.

Case Study on the Remaining Life Analysis of a Power Generation Valve

2008 ◽  
Author(s):  
Daniel T. Peters ◽  
Eric Jones ◽  
Mario Berasi
Keyword(s):  
Life Prediction ◽  
Power Plants ◽  
Fatigue Life Prediction ◽  
Remaining Life ◽  
Success Story ◽  
Successful Management ◽  
Creep Fatigue ◽  
Useful Life ◽  
Life Analysis

Many components in power plants are nearing the end of their useful life. Management of cracking in these components can be critical to the successful management of many power plants. The work here presents a case study of a success story of the analysis of one of these components. The paper here discusses the study of a valve that was originally scheduled for replacement during a recent outage. The work comprised of the examination and accurate sizing of the cracking inside the valve, stress analysis using cutting edge modeling for quick turn around, and advanced creep-fatigue life prediction calculations to give accurate predictions regarding the remaining life of the component. The project culminated in the ability of the valve, with proper care and monitoring to be continued in service for many years and eliminating the need to extend the previous outage.

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