A Reliability-Based Approach for Low-Cycle Fatigue Design of Class 2 and 3 Nuclear Piping

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
Kleio Avrithi ◽  
Bilal M. Ayyub
Keyword(s):  
Failure Probability ◽  
Design Methodology ◽  
Low Cycle Fatigue ◽  
Probabilistic Design ◽  
Cycle Fatigue ◽  
Reliability Level ◽  
Fatigue Design ◽  
Design Variables ◽  
Current Design ◽  
Acceptable Reliability

This paper presents a reliability-based low-cycle fatigue design approach for class 2 and 3 nuclear pipes. Initially, the methodology and background for the design of the pipes according to the ASME Boiler and Pressure Vessel (B&PV) Code is presented. Then a probabilistic design methodology based on the ASME B&PV Code and focused on straight pipes with butt-welds is presented. The method ensures an acceptable reliability level for piping by keeping the failure probability within some upper threshold and accounting for the uncertainties of the design variables. In opposition, the current design may result in diverse and often unknown probabilities of failure for piping. A computational example illustrates the developed method.

Review of Margins Needed to Develop Fatigue Design Curves From Laboratory Test Data

2003 ◽  
Author(s):  
W. A. Van Der Sluys
Keyword(s):  
Fatigue Testing ◽  
Low Cycle Fatigue ◽  
Light Water Reactor ◽  
Fatigue Properties ◽  
Low Alloy Steels ◽  
Test Results ◽  
Cycle Fatigue ◽  
Fatigue Design ◽  
Current Design ◽  
Alloy Steels

The PVRC has just completed a review of the effect of LWR (Light Water Reactor) coolant environment on the low cycle fatigue properties of carbon and low alloy steels. The PVRC has made recommendations to the ASME on changes to the boiler and pressure vessel codes to account for the environmental effects. In developing the recommendations, the margins used to produce the design curves from fatigue test results of laboratory specimens, were studied. This paper describes the margins used by the ASME in the development of the current design curves and discusses what margins should be applied when the laboratory fatigue testing includes tests in simulated LWR coolant environments.

scholarly journals RELIABILITY BASED DESIGN OF RUBBLE-MOUND BREAKWATER

1988 ◽  
Vol 1 (21) ◽  
pp. 153
Author(s):  
Masato Yamamoto ◽  
Kazumasa Mizumura ◽  
Taiji Endo ◽  
Naofumi Shiraishi
Keyword(s):  
Water Level ◽  
Optimum Design ◽  
Failure Probability ◽  
Design Methodology ◽  
Construction Cost ◽  
Probabilistic Design ◽  
Reliability Based Design ◽  
Rubble Mound ◽  
Reduced Risk

The object of this present research is to study probabilistic design of armor blocks protecting composite breakwaters and to produce optimum design methodology for S-shaped breakwaters in terms of failure probability and construction cost. Failure probability in the vicinity of the still water level is greatest in the case of uniform sloped breakwaters. Therefore,S-shaped breakwaters of which the slope near the still water level is milder have a reduced risk of damage compared to uniform sloped ones. The optimum design index presents good economics and reliability in rubble-mound breakwater design.

Pipe Elbows Under Strong Cyclic Loading

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
George E. Varelis ◽  
Spyros A. Karamanos ◽  
Arnold M. Gresnigt
Keyword(s):  
Cyclic Loading ◽  
Low Cycle Fatigue ◽  
Seismic Loading ◽  
Fatigue Curve ◽  
Design Codes ◽  
Loading Conditions ◽  
Cycle Fatigue ◽  
Finite Element Analyses ◽  
Fatigue Design ◽  
Process Piping

Motivated by the response of industrial piping under seismic loading conditions, the present study examines the behavior of steel process piping elbows, subjected to strong cyclic loading conditions. A set of experiments is conducted on elbow specimens subjected to constant amplitude in-plane cyclic bending, resulting into failure in the low-cycle-fatigue range. The experimental results are used to develop a low-cycle-fatigue curve within the strain-based fatigue design framework. The experimental work is supported by finite element analyses, which account for geometrical and material nonlinearities. Using advanced plasticity models to describe the behavior of elbow material, the analysis focuses on localized deformations at the critical positions where cracking occurs. Finally, the relevant provisions of design codes (ASME B31.3 and EN 13480) for elbow design are discussed and assessed, with respect to the experimental and numerical findings.

Evaluation of Low-Cycle Fatigue in Simulated PWR Environment

2006 ◽  
Vol 326-328 ◽  
pp. 1011-1014 ◽  
Author(s):  
Ill Seok Jeong ◽  
Sang Jai Kim ◽  
Taek Ho Song ◽  
Sung Yull Hong
Keyword(s):  
Fatigue Life ◽  
Nuclear Power ◽  
Power Plants ◽  
Low Cycle Fatigue ◽  
Water Environment ◽  
Fatigue Tests ◽  
Cycle Fatigue ◽  
Fatigue Design ◽  
Number Of Cycles ◽  
Measured Length

For developing fatigue design curve of cast stainless steel that is used in piping material of nuclear power plants, a low-cycle fatigue test rig was built. It is capable of performing tests in pressurized high temperature water environment of PWR. Cylindrical solid fatigue specimens of CF8M were used for the strain-controlled environmental fatigue tests. Fatigue life was measured in terms of the number of cycles with the variation of strain amplitude at 0.04%/s strain rates. The disparity between target length and measured length of specimens was corrected by using finite element method. The corrected test results showed similar fatigue life trend with other previous results.

Probabilistic Design of High Temperature Components Subjected to Low Cycle Fatigue Loads

1995 ◽  
Author(s):  
Ronald Pigott
Keyword(s):  
High Temperature ◽  
Factor Of Safety ◽  
Elevated Temperatures ◽  
Low Cycle Fatigue ◽  
Probabilistic Design ◽  
Cycle Fatigue ◽  
Single Factor ◽  
First Order Second Moment ◽  
Fatigue Loads ◽  
High Temperature Components

Abstract From the beginning, engineers have focused on the special case of determinism in the design process, and an enormous methodology has been developed to support this approach. Today, however, customers are demanding greater reliability and are imposing greater penalties for failure. In order to achieve higher reliability, and in order to asses risk of failure, probabilistic approaches will almost certainly have to be employed. While designers have always used probability in their work, it has usually been done with risk represented in a single factor of safety. This paper focuses on the application of probability theory to the design of high temperature components which are subjected to low cycle fatigue loads. Creep low cycle fatigue interaction and probabilistic design are both complex subjects. In order to make the probabilistic design of components subjected to creep and low cycle fatigue tractable, the calculation models must be as simple as possible without sacrificing too much on accuracy. In this paper, cumulative damage is determined using Miner’s Rule in conjunction with “range pair” cycle counting. The effect of operation at elevated temperatures is included using Coffin’s frequency modified approach. A first order second moment (FORM) method for including probabilistic effects is developed and some sample calculations are presented. It is shown that the traditional deterministic approach using a single factor of safety does not provide a uniform margin of safety for all design conditions.

Probabilistic Design Methodology and the Application of Probabilistic Fault Tree Analysis to Machine Design

1995 ◽  
Author(s):  
Landon C. Onyebueke ◽  
Chinyere Onwubiko ◽  
Feng C. Chen
Keyword(s):  
Design Methodology ◽  
Fault Tree ◽  
Fault Tree Analysis ◽  
Computer Code ◽  
Spur Gear ◽  
Probabilistic Design ◽  
System Construction ◽  
Tree Analysis ◽  
Design Variables ◽  
Structural Variables

Abstract This paper gives an overview of Probabilistic Design Methodology (PDM) with emphasis on quantification of the effects of uncertainties for structural variables and the evaluation of failure probability. The application of Probabilistic Fault Tree Analysis (PFTA) to the design of a shaft carrying a spur gear is also presented. The PFTA includes the development of a fault tree to represent the system, construction of an approximation function for bottom events, computation of sensitivity factors of design variables, and the calculation of the system reliability. The computer code employed for the analyses is known as “Numerical Evaluation of Stochastic Structures Under Stress” (NESSUS). NESSUS is developed under NASA probabilistic structural analysis program.

High-Cycle and Low-Cycle Fatigue Resistance of Girth Welds in Sour Service

2008 ◽  
Author(s):  
Jaime Buitrago ◽  
Stephen Hudak ◽  
David Baxter
Keyword(s):  
Low Cycle Fatigue ◽  
Water Injection ◽  
Fatigue Performance ◽  
Cycle Fatigue ◽  
Production Lines ◽  
Hydrocarbon Production ◽  
Steel Catenary Riser ◽  
Fatigue Design ◽  
Girth Welds ◽  
Constant Slope

The fatigue performance of fracture-critical production lines, such as risers and flowlines, has been shown to significantly degrade in the presence of sour hydrocarbon production caused by water injection of reservoirs. To ensure the reliability of the fatigue design under such conditions, experimental verification of the degradation effect on fatigue life due the presence of H2S is required. To that end and over the past several years, ExxonMobil has developed new testing methodologies to evaluate the riser fatigue performance for both in-air and sour conditions. This paper reviews the general elements of the fatigue qualification process and presents new sour fatigue data aimed at assessing performance at the high-cycle fatigue (HCF) and low-cycle fatigue (LCF) regimes. These new data are relevant to that seen in steel catenary riser (SCR) and flowline thermal responses, respectively. Testing methodologies for each regime are discussed and results presented. The new data are interpreted within the context of previous data in the intermediate-cycle fatigue (ICF) to provide a more robust basis for riser design. The main finding is that the new data support a constant slope S-N curve for the practical domain of fatigue lives to which offshore lines are typically designed under sour conditions.

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