Design Study of a Superheater Header Subjected to Cyclic and High Temperature Loading

2007 ◽  
Author(s):  
Jinhua Shi
Keyword(s):  
High Temperature ◽  
Fatigue Damage ◽  
Creep Damage ◽  
Operating Conditions ◽  
Design Code ◽  
Life Study ◽  
Interaction Diagram ◽  
Design Life ◽  
Time To Rupture ◽  
Creep Fatigue

A typical superheater header in a power station is normally subject to high pressure and high temperature loading. Due to increasing fuel prices, many stations especially gas fired power stations are operated cyclically to increase flexibility and to reduce the running costs. Accordingly, new design of heat recovery steam generators (HRSGs) has been required to undertake cyclic operations. For a base load superheater header, the design life is dominated by material creep properties (time to rupture). However, for a header subjected to two shift cyclic operating conditions, fatigue damage could be increased significantly. Therefore, creep-fatigue interaction should be considered. In this paper, a creep-fatigue design life study of a typical HRSG superheater header has been conducted under various cyclic conditions. Creep stresses for the header are calculated using a reverse design code method, and the creep damage is then obtained based on the time to rupture data. Meanwhile, fatigue calculations are carried out using the methodology given in a new European boiler design code BS EN 12952. The results of creep and fatigue damage obtained are presented in a creep-fatigue interaction diagram shown in ASME III Section NH (former N47 Case) for comparisons. After a brief discussion of the results, a conclusion is drawn.

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.

scholarly journals A New 3D Creep-Fatigue-Elasticity Damage Interaction Diagram Based on the Total Tensile Strain Energy Density Model

Metals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 274 ◽  
Author(s):  
Qiang Wang ◽  
Naiqiang Zhang ◽  
Xishu Wang
Keyword(s):  
High Temperature ◽  
Energy Density ◽  
Fatigue Damage ◽  
Strain Energy Density ◽  
Strain Energy ◽  
Life Prediction ◽  
Tensile Strain ◽  
Elastic Strain Energy ◽  
Interaction Diagram ◽  
Creep Fatigue

Fatigue damage, creep damage, and their interactions are the critical factors in degrading the integrity of most high-temperature engineering structures. A reliable creep-fatigue damage interaction diagram is a crucial issue for the design and assessment of high-temperature components used in power plants. In this paper, a new three-dimensional creep-fatigue-elasticity damage interaction diagram was constructed based on a developed life prediction model for both high-temperature fatigue and creep fatigue. The total tensile strain energy density concept is adopted as a damage parameter for life prediction by using the elastic strain energy density and mean stress concepts. The model was validated by a great deal of data such as P91 steel at 550 °C, Haynes 230 at 850 °C, Alloy 617 at 850 and 950 °C, and Inconel 625 at 815 °C. The estimation values have very high accuracy since nearly all the test data fell into the scatter band of 2.0.

Creep/Fatigue Interaction Correlation for 304 Stainless Steel Subjected to Strain-Controlled Cycling With Hold Times at Peak Strain

1971 ◽  
Vol 93 (4) ◽  
pp. 887-892 ◽  
Author(s):  
R. D. Campbell
Keyword(s):  
Fatigue Damage ◽  
Creep Damage ◽  
Fatigue Tests ◽  
304 Stainless Steel ◽  
Peak Strain ◽  
Interaction Diagram ◽  
Data Scatter ◽  
Creep Fatigue ◽  
Relaxation Curves ◽  
Life Fraction

A numerical integration of creep relaxation curves from strain-controlled fatigue tests with hold times introduced at peak strain is performed to sum creep damage by the linear life fraction rule. Fatigue damage is summed and an interaction diagram for creep and fatigue damage is constructed. Data scatter about the interaction curve is compared to scatter for independent creep rupture and fatigue tests from the identical heat of material.

Direct Method on Creep Fatigue Damage Assessment Considering Full Creep-Cyclic Plasticity Interaction

2017 ◽  
Author(s):  
Daniele Barbera ◽  
Haofeng Chen ◽  
Weiling Luan
Keyword(s):  
High Temperature ◽  
Fatigue Damage ◽  
Damage Assessment ◽  
Direct Method ◽  
Creep Damage ◽  
Load Cycle ◽  
Cyclic Plasticity ◽  
Assessment Procedure ◽  
Creep Fatigue ◽  
The Uk

This paper introduces the latest research and development of the Linear Matching Method (LMM) on the creep fatigue damage assessment of components subjected to high temperature and cyclic load conditions. The method varies from existing rule-based approaches in both the ASME Boiler and Pressure Vessel Code (NH) and the UK R5 high temperature assessment procedure, where the creep behavior/creep damage and cyclic plastic response /fatigue damage are analyzed separately. In support to these the extended Direct Steady Cycle Analysis (eDSCA) has been proposed to provide a more accurate description of the potentially dangerous interaction between creep and cyclic plasticity during the load cycle, and hence is able to accurately address creep enhanced plasticity and cyclically enhanced creep. The applications of the LMM eDSCA method for creep fatigue damage assessment to three practical problems are then outlined to demonstrate that the proposed direct method is capable of predicting an accurate component life due to creep fatigue and creep ratcheting damages by modeling cyclic plasticity and creep interaction using this new simplified direct method, providing a degree of accuracy and convenience in creep fatigue assessment hitherto unavailable and without the restrictions inherent in other methodologies.

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.

An Evaluation of Creep-Fatigue Damage for the Prototype Process Heat Exchanger of the NHDD Plant

2011 ◽  
Vol 133 (5) ◽  
Author(s):  
Hyeong-Yeon Lee ◽  
Kee-Nam Song ◽  
Yong-Wan Kim ◽  
Sung-Deok Hong ◽  
Hong-Yune Park
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
High Temperature ◽  
Fatigue Damage ◽  
Inlet Temperature ◽  
Alloy 617 ◽  
Element Analysis ◽  
Creep Fatigue ◽  
Process Heat ◽  
Very High

A process heat exchanger (PHE) transfers the heat generated from a nuclear reactor to a sulfur-iodine hydrogen production system in the Nuclear Hydrogen Development and Demonstration, and was subjected to very high temperature up to 950°C. An evaluation of creep-fatigue damage, for a prototype PHE, has been carried out from finite element analysis with the full three dimensional model of the PHE. The inlet temperature in the primary side of the PHE was 950°C with an internal pressure of 7 MPa, while the inlet temperature in the secondary side of the PHE is 500°C with internal pressure of 4 MPa. The candidate materials of the PHE were Alloy 617 and Hastelloy X. In this study, only the Alloy 617 was considered because the high temperature design code is available only for Alloy 617. Using the full 3D finite element analysis on the PHE model, creep-fatigue damage evaluation at very high temperature was carried out, according to the ASME Draft Code Case for Alloy 617, and technical issues in the Draft Code Case were raised.

Structural Evaluation With Elastic and Inelastic Analysis Methods on a High Temperature Storage Tank Subjected to Static and Dynamic Loadings

2020 ◽  
Author(s):  
Wen Wang ◽  
Xiaochun Zhang ◽  
Xiaoyan Wang ◽  
Maoyuan Cai
Keyword(s):  
High Temperature ◽  
Elevated Temperature ◽  
Molten Salt ◽  
Fatigue Damage ◽  
Storage Tank ◽  
Power Plants ◽  
Elastic Analysis ◽  
Inelastic Analysis ◽  
Analysis Methods ◽  
Creep Fatigue

Abstract The structural integrity of reactor components is very essential for the reliable operation of all types of power plants, especially for components operating at elevated temperature where creep effects are significant and where components are subjected to high-temperature alteration and seismic transient loading conditions. In this article, a molten salt storage tank in high temperature thorium molten salt reactor (TMSR) is evaluated according to ASME-III-5-HBB high temperature reactor code. The evaluation based on 3D finite element analyses includes the load-controlled stress, the effects of ratcheting, and the interaction of creep and fatigue. The thermal and structural analysis and the application procedures of ASME-HBB rules are described in detail. Some structural modifications have been made on this molten salt storage tank to enhance the strength and reduce thermal stress. The effects of ratcheting and creep-fatigue damage under elevated temperature are investigated using elastic analysis and inelastic analysis methods for a defined representative load cycle. In addition, the strain range and the stress relaxation history calculated by elastic and inelastic methods are compared and discussed. The numerical results indicate that the elastic analysis is conservative for design and a full inelastic analysis method for estimating input for creep-fatigue damage evaluation need to be developed.

A Damage Evaluation Model of Turbine Blade for Gas Turbine

2016 ◽  
Author(s):  
Dengji Zhou ◽  
Meishan Chen ◽  
Huisheng Zhang ◽  
Shilie Weng
Keyword(s):  
High Temperature ◽  
Real Time ◽  
Gas Turbine ◽  
Evaluation Model ◽  
Creep Damage ◽  
Operating Conditions ◽  
Damage Analysis ◽  
Damage Evaluation ◽  
Analysis Model ◽  
Estimation Model

Current maintenance, having a great impact on the safety, reliability and economics of gas turbine, becomes the major obstacle of the application of gas turbine in energy field. An effective solution is to process Condition based Maintenance (CBM) thoroughly for gas turbine. Maintenance of high temperature blade, accounting for most of the maintenance cost and time, is the crucial section of gas turbine maintenance. The suggested life of high temperature blade by Original Equipment Manufacturer (OEM) is based on several certain operating conditions, which is used for Time based Maintenance (TBM). Thus, for the requirement of gas turbine CBM, a damage evaluation model is demanded to estimate the life consumption in real time. A physics-based model is built, consisting of thermodynamic performance simulation model, mechanical stress estimation model, thermal estimation model, creep damage analysis model and fatigue damage analysis model. Unmeasured parameters are simulated by the thermodynamic performance simulation model, as the input of the mechanical stress estimation model and the thermal estimation model. Then the stress and temperature distribution of blades will be got as the input of the creep damage analysis model and the fatigue damage analysis model. The real-time damage of blades will be evaluated based on the creep and fatigue analysis results. To validate this physics-based model, it is used to calculate the lifes of high temperature blade under several certain operating conditions. And the results are compared to the suggestion value of OEM. An application case is designed to evaluate the application effect of this model. The result shows that the relative error of this model is less than 10.4% in selected cases. And it can cut overhaul costs and increase the availability of gas turbine significantly. Therefore, the physical-based damage evaluation model proposed in this paper, is found to be a useful tool to tracing the real-time life consumption of high temperature blade, to support the implementation of CBM for gas turbine, and to guarantee the reliability of gas turbine with lowest maintenance costs.

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