A Combined Creep and Fatigue Damage Estimation Tool for Power-Plant Monitoring

2016 ◽  
Author(s):  
Noel M. Harrison ◽  
Adelina Adams ◽  
Padraic E. O’Donoghue ◽  
Sean B. Leen
Keyword(s):  
Power Plant ◽  
Fatigue Damage ◽  
Creep Damage ◽  
Remaining Life ◽  
Visual Basic For Applications ◽  
Creep Fatigue ◽  
Time Histories ◽  
Rainflow Cycle Counting ◽  
Stress Fatigue ◽  
User Friendly

A user-friendly creep-fatigue damage calculation tool is developed in Visual Basic for Applications (VBA) with the familiar Microsoft Excel® user interface for power plant operators. Operational pressure and temperatures (steam and pipe exterior) are directly input and automatically converted to stress-time histories based on the summation of thermally- and mechanically-induced stresses. The stress history is automatically analysed and segregated into periods of sustained stress levels (creep range) and periods of fluctuating stress (fatigue range). Total damage is determined by summing the creep damage fraction (via Larson-Miller equation and Robinson’s rule) and fatigue damage fraction (via a rainflow cycle counting subroutine, the Smith-Watson-Topper fatigue parameter and Miner’s rule). Pre-existing damage fraction can be incorporated into the calculations. The remaining life estimates based on repetition of the load profile are outputted for the user. Finally, the estimated damage and remaining life are compared to that determined via the ASME, EN and TRD codes, where applicable.

Estimation of Creep-Fatigue Damage Through Indentation Test Method

2011 ◽  
Author(s):  
Raghu V. Prakash
Keyword(s):  
Tensile Properties ◽  
Fatigue Damage ◽  
Indentation Test ◽  
Creep Damage ◽  
Test Method ◽  
Specimen Preparation ◽  
Creep Fatigue ◽  
Critical Components ◽  
The Cost

Creep, creep-fatigue damage is often estimated through in-situ metallography, tensile testing of specimens. However, these methods require specimen preparation which includes specimen extraction from critical components. Automated ball indentation testing has been used as an effective tool to determine the mechanical properties of metallic materials. In this work, the tensile properties of materials subjected to controlled levels of damage in creep, creep-fatigue is studied. It is found that the tensile properties such as yield strength and UTS deteriorates with creep damage, whereas the same specimens show an improved UTS values (at the cost of ductility) when subjected to creep-fatigue interactions.

Creep-Fatigue Damage and Crack Initiation for a Mod 9Cr-1Mo Structure With Weldments

2007 ◽  
Author(s):  
Hyeong-Yeon Lee ◽  
Se-Hwan Lee ◽  
Jong-Bum Kim ◽  
Jae-Han Lee
Keyword(s):  
Fatigue Crack ◽  
Crack Initiation ◽  
Fatigue Damage ◽  
Hold Time ◽  
Fatigue Crack Initiation ◽  
Creep Damage ◽  
Steel Specimen ◽  
Structural Test ◽  
Creep Fatigue ◽  
Creep Fatigue Crack

A structural test and evaluation on creep-fatigue damage, and creep-fatigue crack initiation have been carried out for a Mod. 9Cr-1Mo steel structural specimen with weldments. The conservatisms of the design codes of ASME Section III subsection and NH and RCC-MR codes were quantified at the welded joints of Mod.9Cr-1Mo steel and 316L stainless steel with the observed images from the structural test. In creep damage evaluation using the RCC-MR code, isochronous curve has been used rather than directly using the creep law as the RCC-MR specifies. A y-shaped steel specimen of a diameter 500mm, height 440mm and thickness 6.35mm is subjected to creep-fatigue loads with two hours of a hold time at 600°C and a primary nominal stress of 30MPa. The defect assessment procedures of RCC-MR A16 guide do not provide a procedure for Mod.9Cr-1Mo steel yet. In this study application of σd method for the assessment of creep-fatigue crack initiation has been examined for a Mod. 9Cr-1Mo steel structure.

Comparison of R5 and ASME NH Creep-Fatigue Damage Assessment Methodologies

2013 ◽  
Author(s):  
Michael Sheridan ◽  
David Knowles ◽  
Oliver Montgomery
Keyword(s):  
Fatigue Damage ◽  
Structural Integrity ◽  
Temperature Response ◽  
Creep Damage ◽  
Basic Principles ◽  
Metallic Structures ◽  
Reference Stress ◽  
Creep Fatigue ◽  
Design Generation

The R5 volume 2/3 procedures [1] were developed by British Energy (now EDF Energy) to assess the high temperature response of uncracked metallic structures under steady state or cyclic loading. They contain the basic principles of: • Application of reference stress methods • Consideration of elastic follow up • A ductility exhaustion approach to calculate creep damage accumulation. These considerations represent a fundamental distinction from ASME BPVC Section III, Subsection NH [2]. This paper draws on literature review and experience to explain the principal differences in the limits of application, cycle construction and damage calculation between these codes/procedures focusing on creep-fatigue damage determination. The implications of the differences between the codes and standards are explored. The output of this work is aimed at two groups of structural integrity engineers; those using these codes and standards to assess existing conventional and nuclear plant, and also those looking to ASME and R5 to design Generation IV PWRs with design temperatures much elevated from those of Generation III and III+. The conclusions from this paper offer some practical guidance to structural integrity engineers which may assist in selecting the more appropriate procedure to assess creep-fatigue damage for a particular situation.

Findings on Creep-Fatigue Damage in Pressure Parts of Long-Term Service-Exposed Thermal Power Plants

1985 ◽  
Vol 107 (3) ◽  
pp. 260-270 ◽  
Author(s):  
F. Masuyama ◽  
K. Setoguchi ◽  
H. Haneda ◽  
F. Nanjo
Keyword(s):  
Fatigue Damage ◽  
Power Plants ◽  
Thermal Power ◽  
Field Experiences ◽  
Creep Damage ◽  
Thermal Power Plants ◽  
Damage Analysis ◽  
Creep Fatigue ◽  
Fatigue Damage Analysis

The increase of long-term service exposure to thermal power plants, the tendency toward intermediate and cyclic operation to meet the change in electric power demand and supply situation, and the requirement to develop higher-temperature and higher-pressure plants have led to increasing attention towards the reliability improvement. This paper presents findings from field experiences of cracking or failure and two types of damage analyses—(1) creep-fatigue damage analysis based on the life fraction rule and (2) metallurgical damage analysis—of boiler pressure parts that have been exposed to long-term elevated temperature service. The field experiences are (1) cracking or failure of thick-walled Type 316 stainless steel pressure parts in the main steam line of an ultra-supercritical thermal power plant and (2) dissimilar metal weld joints for boiler tubing. The creep-fatigue damage analysis of these pressure parts showed a reasonable correspondence with the field experience. According to the creep-fatigue damage analysis and the metallurgical damage analysis, most of damage was restrained creep mode phenomenon without deformation. The creep damage was composed of metallurgical damage and mechanical damage such as microvoids and structural defects. One method of simulating field experienced creep damage was proposed and performed. As a result, the process of creep voids being generated and growing into cracks without deformation was successfully observed. Also a review of the current status of nondestructive detecting methods of creep damage suggests that detecting the creep voids metallurgically is more practical at the present time than doing so analyzing the changes in physical properties of the material. It is also suggested that, in the metallurgical approach, detecting the creep voids and cracks by replica method and anlayzing precipitates for evaluation of material deterioration by precipitate extraction method will make it possible to successfully address the problem of plant equipment creep damage evaluation and life prediction.

A Basic Study on Creep-Fatigue Damages Interaction for Sn-3.0Ag-0.5Cu as Lead Free Solder Material

2015 ◽  
Author(s):  
Hirokazu Oriyama ◽  
Takashi Kawakami ◽  
Takahiro Kinoshita
Keyword(s):  
Solder Joint ◽  
Fatigue Damage ◽  
Solder Joints ◽  
Mechanical Design ◽  
Low Cycle Fatigue ◽  
Creep Damage ◽  
Lead Free ◽  
Lead Free Solder ◽  
Creep Fatigue ◽  
Free Solder

Sn-Ag-Cu solder materials have been widely used for the mount process of electronics devices or semiconductor packages on print circuit board (PCB). The solder joints are sometimes opened under thermal cyclic loads as low cycle fatigue phenomenon. The fatigue life of solder joint has been investigated by many researchers with experimental and numerical methods. Generally, the induced thermal stress in solder joints should be relaxed as soon and creep damage is considered to be ignored in order to estimate lives of joints. However, it is probable that long term stress is applied to solder joints by the elastic follow-up phenomenon which are depending on the stiffness ratio between solder joints and the electronics device, because the elastic strain in PCB or the electronics device shifts to creep strain in solder joints gradually during a long time. Then the creep damage of solder joint should be counted for the mechanical design of mounted PCBs. And it is known that the interaction between creep damage and fatigue damage significantly shorten the life. In this study, it was discussed whether the interaction between fatigue damage and creep damage has to be considered or not for the mechanical design of the lead free solder joint with basic creep-fatigue tests at an elevated temperature.

Failure Analysis of SA-213 T91 HRSG Superheater Tube Weld

2019 ◽  
Author(s):  
Peter S. Jackson ◽  
Andreas Fabricius ◽  
Alexandria Wholey
Keyword(s):  
Power Plant ◽  
Flow Pattern ◽  
Gas Turbine ◽  
Gas Flow ◽  
Creep Damage ◽  
Combined Cycle ◽  
Process Data ◽  
Left Hand ◽  
Root Cause ◽  
Creep Fatigue

Abstract The root cause of a series of similar failures in SA-213 T91 Superheater tubes of an Heat Recovery Steam Generator (HRSG) is investigated using a combination of engineering analysis and review of process data. The HRSG at the Combined Cycle Gas Turbine (CCGT) Power Plant power plant in question had suffered from frequent tube-to-header fatigue failures over the past 10 years. Metallurgical analyses had never identified any sign of creep damage in, or near, any of the failure locations. Recently, the Gas Turbine (GT) exhaust gas flow pattern upstream of the SH tubes changed slightly. Subsequently there were a large number of HPSH tube to header failures (> 10) on one side of the gas duct. Metallurgical analysis showed that the tube-to-header welds failed by creep-fatigue damage; analyses of tubes from the left-hand side of the boiler did not show any signs of similar damage being present. Further investigation confirmed that the root cause was identified as higher temperatures resulting from small changes in the GT outlet flow pattern.

Thermomechanical fatigue life prediction method for nickel-based superalloy in aeroengine turbine discs under multiaxial loading

2019 ◽  
Vol 28 (9) ◽  
pp. 1344-1366 ◽  
Author(s):  
Fang-Dai Li ◽  
De-Guang Shang ◽  
Cheng-Cheng Zhang ◽  
Xiao-Dong Liu ◽  
Dao-Hang Li ◽  
...  
Keyword(s):  
Fatigue Damage ◽  
Cyclic Deformation ◽  
Deformation Behavior ◽  
Life Prediction ◽  
Prediction Method ◽  
Creep Damage ◽  
Damage Mechanism ◽  
Thermomechanical Fatigue ◽  
Nickel Based Superalloy ◽  
Creep Fatigue

The multiaxial thermomechanical fatigue properties for nickel-based superalloy GH4169 in aeroengine turbine discs are investigated in this paper. Four types of axial–torsional thermomechanical fatigue experiments were performed to identify the cyclic deformation behavior and the damage mechanism. The experimental results showed that the creep damage can be generated under thermally in-phase loading while it can be ignored under thermally out-of-phase loading, and the responded stress increasing phenomenon, that is, non-proportional hardening, can be shown under the mechanically out-of-phase strain loading. Based on the analysis of cyclic deformation behavior and damage mechanism, a life prediction method was proposed for multiaxial thermomechanical fatigue, in which the pure fatigue damage, the creep damage, and the interaction between them were simultaneously considered. The pure fatigue damage can be calculated by the isothermal fatigue parameters corresponding to the temperature without creep; the creep damage can be calculated by the principle of subdivision, and the creep–fatigue interaction can be determined by creep damage, fatigue damage, and an interaction coefficient which is used to reflect the creep–fatigue interaction strength. The predicted results showed that the proposed method is reasonable.

A Comparison of Creep-Fatigue Assessment and Modelling Methods

2014 ◽  
Author(s):  
Rami H. Pohja ◽  
Stefan B. Holmström
Keyword(s):  
Fatigue Damage ◽  
Rupture Strength ◽  
Creep Damage ◽  
Creep Rupture ◽  
Design Codes ◽  
Diagram Method ◽  
Fatigue Assessment ◽  
Interaction Diagram ◽  
Fatigue Damage Accumulation ◽  
Creep Fatigue

Design codes, such as RCC-MRx and ASME III NH, for generation IV nuclear reactors use interaction diagram based method for creep-fatigue assessment. In the interaction diagram the fatigue damage is expressed as the ratio of design cycles over the allowable amount of cycles in service and the creep damage as the ratio of time in service over the design life. With this approach it is assumed that these quantities can be added linearly to represent the combined creep-fatigue damage accumulation. Failure is assumed to occur when the sum of the damage reaches a specified value, usually unity or less. The fatigue damage fraction should naturally be unity when no creep damage is present and creep damage should be unity when no fatigue damage is present. However, strict fatigue limits and safety factors used for creep rupture strengths as well as different approaches to relaxation calculation can cause a situation where creep-fatigue test data plotted according to the design rules are three orders of magnitude away from the interaction diagram unity line. Thus, utilizing the interaction diagram methods for predicting the number of creep-fatigue cycles may be inaccurate and from design point of view these methods may be overly conservative. In this paper the results of creep-fatigue tests carried out for austenitic stainless steel 316 and heat resistant ferritic-martensitic steel P91, which are included in the design codes, such as RCC-MRx, are assessed using the interaction diagram method with different levels of criteria for the creep and fatigue fractions. The test results are also compared against the predictions of a recently developed simplified creep-fatigue model which predicts the creep-fatigue damage as a function of strain range, temperature and hold period duration with little amount of fitting parameters. The Φ-model utilizes the creep rupture strength and ultimate tensile strength (UTS) of the material in question as base for the creep-fatigue prediction. Furthermore, challenge of acquiring representative creep damage fractions from the dynamic material response, i.e. cyclic softening with P91 steel, for the interaction diagram based assessment is discussed.

An Overview of Creep-Fatigue Damage Evaluation Methods and an Alternative Approach

2008 ◽  
Author(s):  
Tai Asayama ◽  
Robert Jetter
Keyword(s):  
Fatigue Damage ◽  
Test Specimen ◽  
Creep Damage ◽  
Evaluation Methods ◽  
Damage Evaluation ◽  
Aging Effects ◽  
Correlation Parameter ◽  
Calculated Parameter ◽  
Creep Fatigue ◽  
Cycles To Failure

Renewed interest in elevated temperature nuclear reactors has occasioned a reassessment of creep-fatigue damage evaluation methods. Points to be improved in the current methods employed in Subsection NH of the ASME B&PV Code and other design codes are discussed as well as an alternate approach which avoids some of these problems. Most current creep-fatigue damage evaluation methods separately evaluate cyclic fatigue damage and creep damage and assess the combined damage through interaction diagrams. Typically test data are evaluated through a Miner’s Rule summation of fatigue damage and either a time fraction summation of creep damage or a ductility exhaustion approach in order to establish the appropriate interaction curve. In these approaches, cycles to failure can be counted directly but creep damage is a calculated parameter, subject the limitations of the evaluation technique. There can be considerable scatter in the results. The process is reversed for design and the methodology chosen to assess creep damage will have a major impact on the viability of the design process. This was found to be particularly true for advanced alloys such as Mod9Cr-1Mo-V, aka Grade 91. An alternate approach to determination of cyclic life has been proposed which avoids parsing the damage into creep and fatigue components. This approach, called the Simplified Model Test (SMT), employs a test specimen with elastic follow-up sized to represent the stress and strain redistribution encountered in more complex structures. The correlation parameter between test and design is the elastically calculated strain and the dependent test variable is the observed cycles to failure. The SMT approach has two major advantages. First, because the correlation parameter is elastically calculated strain, it is not necessary to calculate the inelastic stress-strain history for a design evaluation; either directly through inelastic analysis or indirectly through manipulation of elastic analyses. Second, because the test specimen itself incorporates the hardening, softening and aging effects of the structure it represents, it is not necessary do rely on theoretical modeling of these effects in an artificial separate accounting of creep and fatigue damage.

Online Fatigue and Creep Monitoring System for 2-D Axis-Symmetry Components in Power Plants

2011 ◽  
Vol 130-134 ◽  
pp. 3866-3869
Author(s):  
Heng Liang Zhang ◽  
Dan Mei Xie ◽  
Chu Nie ◽  
Yang Heng Xiong
Keyword(s):  
Stress Responses ◽  
Power Plants ◽  
Damage Index ◽  
Creep Damage ◽  
Analytical Models ◽  
Aging Effects ◽  
Creep Fatigue ◽  
Material Creep ◽  
Rainflow Cycle Counting ◽  
Creep Degradation

This paper presents a system developed for online monitoring of various aging effects, such as fatigue, creep and fatigue–creep interaction. An appropriate life prediction methodology has been used to address the various aspects of creep, fatigue and creep fatigue interaction, creep and fatigue crack growth. The system converts the plant transients to temperature and stress responses using the analytical models modified by FEM. The fatigue usage factor is computed using the rainflow cycle counting algorithm. The creep damage index is evaluated from the computed temperature and stress histories and the material creep rupture curve. This system has already been installed at Henan Jiaozuo power plant in china for monitoring the fatigue and creep degradation.

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