Practical and Technical Challenges of the Exhaust System Fatigue Life Assessment Process at Elevated Temperature

2017 ◽  
pp. 371-409 ◽  
Author(s):  
Mark T. Seitz ◽  
Jason D. Hamilton ◽  
Richard K. Voltenburg ◽  
Limin Luo ◽  
Zhigang Wei ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Elevated Temperature ◽  
Exhaust System ◽  
Life Assessment ◽  
Assessment Process ◽  
Fatigue Life Assessment ◽  
Technical Challenges

Handling Uncertainty in the Remnant Fatigue Life Assessment of Offshore Process Pipework

2016 ◽  
Author(s):  
Arvind Keprate ◽  
R. M. Chandima Ratnayake
Keyword(s):  
Fatigue Life ◽  
Crack Growth ◽  
Life Assessment ◽  
Assessment Process ◽  
Linear Elastic ◽  
Fatigue Life Assessment ◽  
Process Piping ◽  
Growth Laws ◽  
Elastic Fracture ◽  
Offshore Industry

A typical procedure for a remnant fatigue life (RFL) assessment is stated in the BS-7910 standard. The aforementioned standard provides two different methodologies for estimating RFL; these are: the S-N curve approach and the crack growth laws (i.e. using Linear Elastic Fracture Mechanics (LEFM) principles) approach. Due to its higher accuracy, the latter approach is more commonly used for RFL assessment in the offshore industry. Nevertheless, accurate prediction of RFL using the deterministic LEFM approach (stated in BS-7910) is a challenging task, as RFL prediction is afflicted with a high number of uncertainties. Furthermore, BS-7910 does not provide any recommendation in regard to handling the uncertainty in the deterministic RFL assessment process. The most common way of dealing with the aforementioned uncertainty is to employ Probabilistic Crack Growth (PCG) models for estimating the RFL. This manuscript explains the procedure for addressing the uncertainty in the RFL assessment of process piping with the help of a numerical example. The numerically obtained RFL estimate is used to demonstrate a calculation of inspection interval.

Extreme Value Distribution Theory and its Application in Durability Analysis

2012 ◽  
Author(s):  
Zhigang Wei ◽  
Pingsha Dong ◽  
Litang Gao ◽  
Robert Kurth
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Extreme Events ◽  
Extreme Value Theory ◽  
Value Theory ◽  
Extreme Value ◽  
Life Assessment ◽  
Assessment Process ◽  
Fatigue Life Assessment ◽  
Axial Fatigue

Risk based treatment of degradation and failure in engineering components is an important topic in recent years with an emphasis on obtaining more detailed information for extreme events. Fatigue damage and life degradation caused by variable amplitude cyclic loading is dominated by such extreme events, and can be properly treated with the extreme value theory, which could help understand the damage nature of the fatigue damage process as well as to provide more efficient and robust approaches for engineering applications. In this paper, advanced extreme value theory is reviewed first. Methods such as peak counting, block maxima, and peaks over thresholds are investigated and compared in this paper with an emphasis on the relationship between the extreme value theory and the existing methods for fatigue life assessment. A few simple examples of uniaxial and multi-axial fatigue life assessment process are provided and the results are discussed. It is found that, if properly used, the extreme value theories can improve the efficiency of fatigue life assessment. Finally, a hybrid time- and frequency-based multi-axial fatigue life assessment procedure is proposed for wide band loadings.

Automated Fatigue Life Assessment for Welded Cruciform Joint Considering Welding Residual Stress

2005 ◽  
Vol 297-300 ◽  
pp. 2800-2805
Author(s):  
Tak Kee Lee ◽  
Chae Whan Rim ◽  
Seung Ho Han ◽  
Jong Han Lee
Keyword(s):  
Residual Stress ◽  
Fatigue Life ◽  
Stress Distribution ◽  
Rational Design ◽  
Welding Residual Stress ◽  
Life Assessment ◽  
Assessment Process ◽  
Automated System ◽  
Fatigue Life Assessment ◽  
Cruciform Joint

For a rational design of a welded joint, it is necessary to repeatedly assess the fatigue life of the joint with various dimensions and welding conditions. In this paper, an automated, repeatable/repetitive fatigue life assessment process for a welded cruciform joint was studied. The process consists of a structural analysis to obtain the stress distribution in the vicinity of the weldtoe, a thermal elasto-plastic analysis to determine the welding residual stress, and a fatigue life assessment based on the analyzed stress distribution and welding residual stress. With changes in design conditions including dimensions and/or welding heat input, the aforementioned tasks have to be performed. Using a commercial tool for system integration, automation of a repeated process for a welded cruciform joint based on 2D modeling was achieved. In this automated system, data exchanges between programs, regardless of whether they are commercial or in-house, work well, and parametric studies for optimal design can be performed.

scholarly journals Fatigue life assessment of an exhaust system for naval gas turbines

2011 ◽  
Vol 10 ◽  
pp. 2548-2553 ◽  
Author(s):  
Rui F. Martins ◽  
João C. Viegas ◽  
Hildebrando J. Cruz
Keyword(s):  
Fatigue Life ◽  
Gas Turbines ◽  
Exhaust System ◽  
Life Assessment ◽  
Fatigue Life Assessment

Development of a Fatigue Life Assessment and Prediction Framework for a Bimetallic-Welded Thick-Wall Component of a Steam Turbine

2016 ◽  
Author(s):  
M.-H. Herman Shen ◽  
Sajedur Akanda ◽  
Xia Liu ◽  
Peng Wang
Keyword(s):  
Fatigue Life ◽  
Elevated Temperature ◽  
Steam Turbine ◽  
Room Temperature ◽  
Analytical Framework ◽  
Fatigue Tests ◽  
Life Assessment ◽  
Thick Wall ◽  
Fatigue Life Assessment ◽  
Control Constant

In this investigation, we have applied an integrated experimental-analytical framework for fatigue life assessment and prediction of a thick-wall component of a high-pressure (HP) steam turbine. Emphasis is placed on the development of an effective experimental and analytical procedure for life characterization on the basis of low cycle and high cycle fatigue (LCF/HCF) in order to improve the safety, reliability, and affordability of real world steam turbine operations. Stress-control constant amplitude fully reversed fatigue tests were performed in room temperature and 500°C to serve two purposes: (a) to obtain experimental stress-life (S-N) curves and (b) to assess the values of the parameters of the energy-based framework to predict the fatigue life. The experimental and the predicted S-N curves are compared with each other in case of both the room and the elevated temperature to examine the soundness of the present energy-based model to predict fatigue life. The present lifing model was found to be able to predict both the room and elevated temperature LCF/HCF life of the thick-wall component with excellent accuracy. Furthermore, the elevated temperature fatigue life is found to be lower than the room temperature fatigue life due to the lower fatigue toughness at elevated temperature.

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