Damage Mechanisms and Life Assessment of High-Temperature Components

1989 ◽  
Author(s):  
R. Viswanathan
Keyword(s):  
High Temperature ◽  
Turbine Blades ◽  
Material Behavior ◽  
Life Assessment ◽  
Damage Mechanisms ◽  
Remaining Service Life ◽  
Property Data ◽  
Creep Fatigue ◽  
Temperature Damage ◽  
High Temperature Components

Damage Mechanisms and Life Assessment of High-Temperature Components deals with the underlying causes of high-temperature failures and their effect on component life and reliability. The first few chapters develop the theory necessary to understand and analyze high-temperature damage phenomena, including fracture, creep, and fatigue. Various forms of embrittlement and corrosion are also addressed as are creep-fatigue, thermal fatigue, and welding defects. The chapters that follow discuss the practical implications of these phenomena, explaining how to assess damage and estimate the remaining service life of boiler tubes, turbine blades, reactor vessels, nozzles, and other components. Life-assessment procedures draw on a knowledge of design, material behavior, and nondestructive inspection techniques, which are covered as well. The book makes extensive use of data plots, diagrams, and images and includes many worked-out examples and case histories. It also serves as a ready source of material property data. For information on the print version, ISBN 978-0-87170-358-3, follow this link.

High temperature fatigue and creep-fatigue behaviors in a Ni-based superalloy: Damage mechanisms and life assessment

2019 ◽  
Vol 118 ◽  
pp. 8-21 ◽  
Author(s):  
Run-Zi Wang ◽  
Shun-Peng Zhu ◽  
Ji Wang ◽  
Xian-Cheng Zhang ◽  
Shan-Tung Tu ◽  
...  
Keyword(s):  
High Temperature ◽  
Life Assessment ◽  
Damage Mechanisms ◽  
High Temperature Fatigue ◽  
Creep Fatigue

Damage Assessment and Management in Reformer Furnaces

1997 ◽  
Vol 119 (4) ◽  
pp. 423-427 ◽  
Author(s):  
T. L. da Silveira ◽  
I. Le May
Keyword(s):  
High Temperature ◽  
Damage Assessment ◽  
Damage Accumulation ◽  
Operating Conditions ◽  
Life Assessment ◽  
Damage Mechanisms ◽  
Temperature Damage

The mechanisms of damage accumulation and methods of life assessment in reformer furnaces are discussed. Such furnaces are key elements in petrochemical plants, receiving a mixture of hydrocarbons and steam and producing a hydrogen-rich reaction gas in the presence of a catalyst. At the operating conditions of 800 to 900°C, high-temperature damage takes place in the reformer columns inside the furnace radiation chamber, as well as in the external outlet pipes. The damage mechanisms and methods of assessment are described for the various components involved.

Creep Deformation and Failure Assessment of Steel Weldments

2007 ◽  
Author(s):  
Bilal Dogan
Keyword(s):  
High Temperature ◽  
Crack Initiation ◽  
Residual Life ◽  
Axial Stress ◽  
Creep Crack Growth ◽  
Material Behavior ◽  
Life Assessment ◽  
Creep Ductility ◽  
Creep Crack ◽  
High Temperature Components

The effect of weldments in service performance of high temperature components has been subject to intensive research due to the fact that in the majority of cases where high temperature failure occurs, defects predominate in the vicinity of weldments. Cracking occurs in service due to reduced creep ductility of HAZ and weld metal due to ageing in service, combined with the action of multi-axial stress fields that reduce the creep ductility further. The defects detected or assumed to exist through minimum allowable limits of detectable flaws using non-destructive testing methods is required for structural integrity and residual life assessment of high temperature components. The assessment relies on information obtained from the material’s high temperature tensile, uniaxial creep, crack initiation and growth properties. The concepts used for time dependent fracture analysis of homogeneous bodies are commonly applied for creep crack growth in weldments that show multi-crack initiation and crack branching. This calls for study of deformation behavior and applicability of fracture mechanics parameters for high temperature assessment of weldments. The present paper reports on the material behavior and methodology followed for testing and assessment of the high temperature steel weldments.

Recent Developments in High Temperature Codes

2009 ◽  
Author(s):  
Bilal Dogan ◽  
R. A. Ainsworth
Keyword(s):  
High Temperature ◽  
Power Plants ◽  
Laboratory Data ◽  
Material Behavior ◽  
Life Assessment ◽  
Creep Fatigue ◽  
Recent Developments ◽  
The Subject ◽  
Static And Cyclic Loading ◽  
Assessment Procedures

The codes and standards specify design rules and methods for assessing defects in structures in service. Recent international effort on design and assessment of components subjected to quasi-static and cyclic loading at high temperatures has focused on the issue of Creep-Fatigue damage and condition assessment, which to date have not been comprehensively addressed in codes. The work has concentrated on basic understanding of material behavior and methods for analyzing laboratory data in order to address the need for service life assessment of components in ageing plants. This recognizes that power plants, on average 35 years in service, are facing increased operational demands imposed in order to respond to the increasing electricity demand. This paper gives an overview of the subject procedures and recent developments in codes and standards. Novel features of the procedure developments relative to the existing high temperature assessment procedures are highlighted.

scholarly journals Creep Fatigue Life Assessment of a Pipe Intersection with Dissimilar Material Joint by Linear Matching Method

2016 ◽  
Vol 853 ◽  
pp. 366-371
Author(s):  
Daniele Barbera ◽  
Hao Feng Chen ◽  
Ying Hua Liu
Keyword(s):  
High Temperature ◽  
Fatigue Life ◽  
Direct Method ◽  
Life Assessment ◽  
Dissimilar Material ◽  
Matching Method ◽  
Fatigue Life Assessment ◽  
Creep Fatigue ◽  
The Impact ◽  
Linear Matching Method

As the energy demand increases the power industry has to enhance both efficiency and environmental sustainability of power plants by increasing the operating temperature. The accurate creep fatigue life assessment is important for the safe operation and design of current and future power plant stations. This paper proposes a practical creep fatigue life assessment case of study by the Linear Matching Method (LMM) framework. The LMM for extended Direct Steady Cycle Analysis (eDSCA) has been adopted to calculate the creep fatigue responses due to the cyclic loading under high temperature conditions. A pipe intersection with dissimilar material joint, subjected to high cycling temperature and constant pressure steam, is used as an example. The closed end condition is considered at both ends of main and branch pipes. The impact of the material mismatch, transitional thermal load, and creep dwell on the failure mechanism and location within the intersection is investigated. All the results demonstrate the capability of the method, and how a direct method is able to support engineers in the assessment and design of high temperature component in a complex loading scenario.

Application of Damage Mechanics and Polynomial Chaos Expansion for Lifetime Prediction of High-Temperature Components Under Creep-Fatigue Loading

2020 ◽  
Author(s):  
Felix Koelzow ◽  
Muhammad Mohsin Khan ◽  
Christian Kontermann ◽  
Matthias Oechsner
Keyword(s):  
High Temperature ◽  
Power Plants ◽  
Damage Mechanics ◽  
Fatigue Loading ◽  
Probabilistic Methods ◽  
Lifetime Prediction ◽  
Model Parameters ◽  
Creep Fatigue ◽  
High Temperature Components ◽  
Mechanics Concepts

Abstract Several (accumulative) lifetime models were developed to assess the lifetime consumption of high-temperature components of steam and gas turbine power plants during flexible operation modes. These accumulative methods have several drawbacks, e.g. that measured loading profiles cannot be used within accumulative lifetime methods without manual corrections, and cannot be combined directly to sophisticated probabilistic methods. Although these methods are widely accepted and used for years, the accumulative lifetime prediction procedures need improvement regarding the lifetime consumption of thermal power plants during flexible operation modes. Furthermore, previous investigations show that the main influencing factor from the materials perspective, the critical damage threshold, cannot be statistically estimated from typical creep-fatigue experiments due to massive experimental effort and a low amount of available data. This paper seeks to investigate simple damage mechanics concepts applied to high-temperature components under creep-fatigue loading to demonstrate that these methods can overcome some drawbacks and use improvement potentials of traditional accumulative lifetime methods. Furthermore, damage mechanics models do not provide any reliability information, and the assessment of the resultant lifetime prediction is nearly impossible. At this point, probabilistic methods are used to quantify the missing information concerning failure probabilities and sensitivities and thus, the combination of both provides rigorous information for engineering judgment. Nearly 50 low cycle fatigue experiments of a high chromium cast steel, including dwell times and service-type cycles, are used to investigate the model properties of a simple damage evolution equation using the strain equivalence hypothesis. Furthermore, different temperatures from 300 °C to 625 °C and different strain ranges from 0.35% to 2% were applied during the experiments. The determination of the specimen stiffness allows a quantification of the damage evolution during the experiment. The model parameters are determined by Nelder-Mead optimization procedure, and the dependencies of the model parameters concerning to different temperatures and strain ranges are investigated. In this paper, polynomial chaos expansion (PCE) is used for uncertainty propagation of the model uncertainties while using non-intrusive methods (regression techniques). In a further post-processing step, the computed PCE coefficients of the damage variable are used to determine the probability of failure as a function of cycles and evolution of the probability density function (pdf). Except for the selected damage mechanics model which is considered simple, the advantages of using damage mechanics concepts combined with sophisticated probabilistic methods are presented in this paper.

Elevated-Temperature Life Assessment

2021 ◽  
pp. 146-166
Author(s):  
Arun Sreeranganathan ◽  
Douglas L. Marriott
Keyword(s):  
High Temperature ◽  
Elevated Temperature ◽  
Stress Relaxation ◽  
Damage Mechanics ◽  
Elevated Temperatures ◽  
Constitutive Models ◽  
Life Assessment ◽  
Remaining Life ◽  
High Temperature Components ◽  
Remaining Life Assessment

Abstract This article provides some new developments in elevated-temperature and life assessments. It is aimed at providing an overview of the damage mechanisms of concern, with a focus on creep, and the methodologies for design and in-service assessment of components operating at elevated temperatures. The article describes the stages of the creep curve, discusses processes involved in the extrapolation of creep data, and summarizes notable creep constitutive models and continuum damage mechanics models. It demonstrates the effects of stress relaxation and redistribution on the remaining life and discusses the Monkman-Grant relationship and multiaxiality. The article further provides information on high-temperature metallurgical changes and high-temperature hydrogen attack and the steps involved in the remaining-life prediction of high-temperature components. It presents case studies on heater tube creep testing and remaining-life assessment, and pressure vessel time-dependent stress analysis showing the effect of stress relaxation at hot spots.

Defect Assessment Procedure for Low to High Temperature Range

2003 ◽  
Author(s):  
Bilal Dogan ◽  
Robert Ainsworth
Keyword(s):  
High Temperature ◽  
Growth Conditions ◽  
Life Assessment ◽  
Assessment Procedure ◽  
High Temperature Range ◽  
Temperature Range ◽  
Defect Assessment ◽  
Creep Fatigue ◽  
Recent Developments ◽  
Assessment Procedures

There are many similarities between available procedures used for defect assessment. They have been developed as a result of experience gained from material-specific programs and have often been verified using the same data. One recently updated document covering life assessment procedures under creep and creep/fatigue crack growth conditions is BS 7910. This document takes into account some of the most recent developments in the subject, including some from the British Energy R5 Procedure. Future developments in defect assessment procedures will follow the route of simplified and unified codes covering defect behaviour in the low to high temperature range. In this paper, the relevance of the insignificant creep curves in RCC-MR for defect free structures and the creep exemption criteria in BS7910 are examined. Then, an overview is given of some European developments in defect assessment methods for Fitness-for-Service assessment, based on recent and current projects such as the EC thematic network FITNET.

Failure Mechanisms of High Temperature Components in Power Plants

2000 ◽  
Vol 122 (3) ◽  
pp. 246-255 ◽  
Author(s):  
R. Viswanathan ◽  
J. Stringer
Keyword(s):  
High Temperature ◽  
Power Plants ◽  
Failure Mechanisms ◽  
Laboratory Data ◽  
Broad Perspective ◽  
Section Size ◽  
Creep Fatigue ◽  
Ultimate Failure ◽  
High Temperature Components ◽  
Utility Deregulation

The principal mechanisms of failure of high temperature components include creep, fatigue, creep-fatigue, and thermal fatigue. In heavy section components, although cracks may initiate and grow by these mechanisms, ultimate failure may occur at low temperatures during startup-shutdown transients. Hence, fracture toughness is also a key consideration. Considerable advances have been made both with respect to crack initiation and crack growth by the above mechanisms. Applying laboratory data to predict component life has often been thwarted by inability to simulate actual stresses, strain cycles, section size effects, environmental effects, and long term degradation effects. This paper will provide a broad perspective on the failure mechanisms and life prediction methods and their significance in the context utility deregulation. [S0094-4289(00)00103-1]

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