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.

Assessment of Power Plant Components With Flaws and Defects Operating in the Long-Term Creep Range

2019 ◽  
Author(s):  
Magdalena Speicher ◽  
Thorben Bender ◽  
Andreas Klenk ◽  
Falk Mueller ◽  
Christian Kontermann ◽  
...  
Keyword(s):  
High Temperature ◽  
Fracture Mechanics ◽  
Crack Initiation ◽  
Crack Growth ◽  
Creep Crack Growth ◽  
Material Behavior ◽  
Critical Crack Length ◽  
Creep Crack ◽  
Combining Data ◽  
Crack Problems

Abstract Originating from defects and flaws in high temperature components crack initiation and crack propagation under service conditions can occur. Fracture mechanics data and procedures are needed to study crack problems and to support an advanced remnant life evaluation. During subsequent research in the past 35 years, data were determined for different high temperature materials. Methodologies and concepts taking into account the specific material behavior were developed in order to be able to describe crack initiation and crack growth and have appropriate assessment methods available. For creep crack initiation two criteria principles were used and for creep crack growth assessment based on the integral C* parameter were applied. Furthermore, a method for determination of critical crack length was developed allowing decisions whether modified stress analysis methods are sufficient or more complicated fracture mechanics methods are needed. To provide data and methodologies in a user-friendly way, a program system combining data and methods was implemented. The paper describes developed features and shows comparisons to other methods. The methods can be applied for design purposes as well as remnant life assessments.

Assessment of Power Plant Components With Flaws and Defects Operating in the Long-Term Creep Range

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Magdalena Speicher ◽  
Thorben Bender ◽  
Andreas Klenk ◽  
Falk Mueller ◽  
Christian Kontermann ◽  
...  
Keyword(s):  
High Temperature ◽  
Fracture Mechanics ◽  
Crack Initiation ◽  
Crack Growth ◽  
Creep Crack Growth ◽  
Material Behavior ◽  
Critical Crack Length ◽  
Creep Crack ◽  
Combining Data ◽  
Crack Problems

Abstract Originating from defects and flaws in high temperature components crack initiation and crack propagation under service conditions can occur. Fracture mechanics data and procedures are needed to study crack problems and to support an advanced remnant life evaluation. During subsequent research in the past 35 years, data were determined for different high temperature materials. Methodologies and concepts taking into account the specific material behavior were developed in order to be able to describe crack initiation and crack growth and have appropriate assessment methods available. For creep crack initiation, two criteria principles were used and for creep crack growth assessment based on the integral C* parameter were applied. Furthermore, a method for determination of critical crack length was developed allowing decisions whether modified stress analysis methods are sufficient or more complicated fracture mechanics methods are needed. To provide data and methodologies in a user-friendly way, a program system combining data and methods was implemented. The paper describes developed features and shows comparisons to other methods. The methods can be applied for design purposes as well as remnant life assessments.

Estimation of Creep Crack Growth Properties Using Circumferential Notched Round Bar Specimen for 12CrWCoB Rotor Steel

2005 ◽  
Vol 297-300 ◽  
pp. 397-402
Author(s):  
Je Chang Ha ◽  
Joon Hyun Lee ◽  
Masaaki Tabuchi ◽  
A.Toshimitsu Yokobori Jr.
Keyword(s):  
Crack Growth ◽  
Axial Stress ◽  
Creep Crack Growth ◽  
Turbine Rotor ◽  
Rotor Steel ◽  
Creep Ductility ◽  
Crack Growth Behaviour ◽  
Creep Crack ◽  
Round Bar ◽  
Growth Properties

Most heat resisting materials in structural components are used under multi-axial stress conditions and under such conditions ductile materials often exhibit brittle manner and low creep ductility at elevated temperature. Creep crack initiation and growth properties are also affected by multi-axial stress and it is important to evaluate these effects when laboratory data are applied to structural components. Creep crack growth tests using circumferential notched round bar specimens are a simple method to investigate multi-axial stress effects without using complicated test facilities. Creep crack growth tests have been performed using a 12CrWCoB turbine rotor steel. In order to investigate the effects of multi-axial stress on creep crack growth properties, the tests were conducted for various notch depths at 650°C. The circumferential notched round bar specimen showed brittle crack growth behaviour under multi-axial stress conditions. Creep crack growth rate was characterized in terms of the C* parameter. A 12CrWCoB turbine rotor steel has been tested using circumferential notched round bar specimens with different multi-axiality. Circumferential notched round bar specimens show increased brittle creep crack growth behaviour due to the multi-axial stress condition. Creep crack growth properties could be predicted by allowing for the decrease of creep ductility under multi-axial conditions.

Specimen Geometry Effects on Creep Crack Initiation and Growth in Parent Materials and Weldments

2011 ◽  
Author(s):  
Catrin M. Davies ◽  
Robert C. Wimpory ◽  
David W. Dean ◽  
Kamran M. Nikbin
Keyword(s):  
High Temperature ◽  
Crack Initiation ◽  
Crack Growth ◽  
Creep Crack Growth ◽  
Parent Material ◽  
Crack Growth Behaviour ◽  
Creep Crack ◽  
Significant Difference ◽  
Constraint Effects

High temperature crack growth in weldments is of great practical concern in high temperature plant components. Cracking typically occurs in the heat affected zone (HAZ) and often propagates into adjacent parent material (PM). Recently, the importance of constraint effects on creep crack growth behaviour has been recognised and creep crack growth testing on a range of specimen geometries has been performed. Experimental crack growth testing has been performed at 550 °C on a range of fracture specimens using sections taken from a non-stress-relieved 316 steel weldment. These specimens include the compact tension, C(T), middle tension, M(T) and circumferentially cracked bar, CCB, geometries. Results are presented from two long-term creep crack growth (CCG) tests performed on M(T) weldment specimens and these are compared with available data on C(T) and CCB weldment specimens together with both long and short term tests on parent material for a range of specimen geometries. The creep crack initiation (CCI) and growth (CCG) behaviour from these tests has been analysed in terms of the C* parameter. As high levels of residual stress exist in non-stress-relieved weldments, the residual stresses remaining in the weldment specimens have therefore been quantified using the neutron diffraction technique. Long-term (low-load) tests are required on PM specimen to observe specimen constraint effects in 316 steel at 550 °C. When interpreted in terms of the C* parameter the CCG behavior of PM and Weldment materials follow the same trendline on low constraint geometries. However, significant difference is observed in the CCG behavior of PM and weldments on the high constraint C(T) geometry. Long term tests on C(T) specimen weldments are required to confirm the results found.

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.

Residual Life Assessment of In-Service High Temperature Components by Small Punch Creep Test

2007 ◽  
Author(s):  
Jianhua Shan ◽  
Xiang Ling ◽  
Zhenmai Qian
Keyword(s):  
High Temperature ◽  
Residual Life ◽  
Assessment Method ◽  
Life Assessment ◽  
Analysis Method ◽  
Creep Life ◽  
Uniaxial Creep ◽  
Life Analysis ◽  
High Temperature Components ◽  
Residual Life Assessment

The knowledge of mechanical long term behaviour under static loading for high temperature components requires methodologies for residual life assessment in order to employ the full potential of materials, particularly in non-destructive methods. In this paper, in order to apply small punch creep (SPC) test to the residual creep life assessment of in-service high temperature components, a variety of SPC tests for Cr5Mo steel in a protective Argon atmosphere were carried out, which used disc test specimens of 10mm in diameter and 0.5mm in thickness extracted both new material and in-service high temperature components. The relationship of the creep deflection curve, the test load, rupture time and ductility of miniature specimens were investigated. Based on SPC test and finite element numerical analysis methods, a novel residual life assessment method was proposed to substitute conventional uniaxial creep life analysis method by introducing an initial creep damage parameter. Moreover, the fractographic observation and the structural damage detection analysis were examined. Finally, the results using conventional uniaxial creep life analysis method were studied to validate the reliability of SPC life assessment method.

Creep Crack Growth Predictions in 316H Steel Over a Wide Range of Stresses and Temperatures

2014 ◽  
Author(s):  
A. Mehmanparast ◽  
C. M. Davies ◽  
K. M. Nikbin ◽  
G. A. Webster
Keyword(s):  
Crack Growth ◽  
Elevated Temperatures ◽  
Prediction Models ◽  
Creep Crack Growth ◽  
Life Assessment ◽  
Creep Ductility ◽  
Crack Growth Behaviour ◽  
Creep Crack ◽  
Uniaxial Creep ◽  
Wide Range

The prediction of the creep crack growth (CCG) behaviour in engineering materials is of great importance in the life assessment of power plant components. The conventional technique to predict CCG is to employ uniaxial creep properties and appropriate damage models in finite element (FE) simulations or analytical CCG prediction models. Uniaxial creep trends for Type 316H SS have been recently estimated for a wide range of stresses and temperatures in [1] and FE CCG predictions have been made at 550 °C and validated through comparison with the experimental data. In this paper, FE CCG predictions using the developed uniaxial creep trends for a wide range of stresses and temperatures are presented and the results are compared with the predicted CCG trend at 550 °C and also with the analytical constant creep ductility NSW CCG prediction models. The results from FE predictions are discussed in terms of the temperature effects on the creep deformation and crack growth behaviour of components operating at elevated temperatures.

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