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.

scholarly journals On Creep Fatigue Interaction of Components at Elevated Temperature

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Daniele Barbera ◽  
Haofeng Chen ◽  
Yinghua Liu
Keyword(s):  
High Temperature ◽  
Mechanical Load ◽  
Direct Method ◽  
Bending Moment ◽  
Strain Range ◽  
Cyclic Plasticity ◽  
Element Analysis ◽  
Total Strain Range ◽  
Creep Fatigue ◽  
A Direct Method

The accurate assessment of creep–fatigue interaction is an important issue for industrial components operating with large cyclic thermal and mechanical loads. An extensive review of different aspects of creep fatigue interaction is proposed in this paper. The introduction of a high temperature creep dwell within the loading cycle has relevant impact on the structural behavior. Different mechanisms can occur, including the cyclically enhanced creep, the creep enhanced plasticity and creep ratchetting due to the creep fatigue interaction. A series of crucial parameters for crack initiation assessment can be identified, such as the start of dwell stress, the creep strain, and the total strain range. A comparison between the ASME NH and R5 is proposed, and the principal differences in calculating the aforementioned parameters are outlined. The linear matching method (LMM) framework is also presented and reviewed, as a direct method capable of calculating these parameters and assessing also the steady state cycle response due to creep and cyclic plasticity interaction. Two numerical examples are presented, the first one is a cruciform weldment subjected to cyclic bending moment and uniform high temperature with different dwell times. The second numerical example considers creep fatigue response on a long fiber reinforced metal matrix composite (MMC), which is subjected to a cycling uniform thermal field and a constant transverse mechanical load. All the results demonstrate that the LMM is capable of providing accurate solutions, and also relaxing the conservatisms of the design codes. Furthermore, as a direct method, it is more efficient than standard inelastic incremental finite element analysis.

Structural Integrity Assessment of Weldments at High Temperature: A Proposed New Approach for R5

2008 ◽  
Author(s):  
N. G. Smith ◽  
D. W. Dean ◽  
M. P. O’Donnell
Keyword(s):  
High Temperature ◽  
Fatigue Damage ◽  
Structural Integrity ◽  
Fatigue Crack Initiation ◽  
Current Approach ◽  
Assessment Procedure ◽  
New Approach ◽  
Integrity Assessment ◽  
Creep Fatigue ◽  
Match Effect

The majority of problems associated with the structural integrity of components, particularly those operating at high temperature, are associated with welds. The R5 procedures provide a comprehensive methodology for the assessment of structures operating within the high temperature creep regime. This includes advice on the modifications required to the basic procedure to account for weldments in creep-fatigue crack initiation assessments. The current approach is based on the use of a Fatigue Strength Reduction Factor (FSRF) which has a value according to the particular class of welded joint. The FSRF affects the calculation of creep and fatigue damage. However, the current approach can be excessively conservative for as-welded weldments which are the main type of weldments in plant. This paper outlines the proposed changes to R5, which seek to achieve the following objectives: • to simplify and clarify the current advice for creep-fatigue initiation assessments of weldments, whilst maintaining a conservative assessment procedure; • to have a robust procedure which can be applied to complex components and loading conditions. The new approach separates the FSRF into two components which are as follows: • the geometric strain enhancement due to the weldment geometry (if applicable) and the material mis-match effect between parent material and weld metal, which is called the Weld Strain Enhancement Factor (WSEF), and • the fatigue endurance reduction effect due to the presence of small imperfections (e.g. inclusions, porosity, etc.) in the weldment constituent materials, which is called the Weld Endurance Reduction (WER). The WSEF is used to determine the stress at the start of a dwell or hold period and, because it has a lower value than the FSRF (due to the removal of the WER), results in less conservative calculations of creep damage compared to the current procedure, which uses the full FSRF. For fatigue damage predictions, the modified route is broadly similar to the current route, since the combination of the WER and the WSEF in the modified route corresponds to the FSRF used in the current route. Assessments to demonstrate the improved endurance predictions using the proposed new approach have been performed on several creep-fatigue weldment features tests and examples are provided in this paper.

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.

Simplified HTHA Evaluation Using Larson Miller Parameter Concepts

2021 ◽  
Author(s):  
Sujay Krishnamurthy ◽  
Benjamin F. Hantz
Keyword(s):  
High Temperature ◽  
Damage Assessment ◽  
Creep Damage ◽  
Assessment Procedure ◽  
Methane Pressure ◽  
Hydrogen Attack ◽  
Temperature Dependent ◽  
Exponential Relationship ◽  
Damage Process ◽  
Life Fraction

Abstract Researchers have been developing mechanistic approaches describing High Temperature Hydrogen Attack (HTHA) damage for quite some time. Although there are a variety of approaches, all of them make use of describing HTHA as a time and temperature dependent phenomena that is sensitive to methane pressure. HTHA research shows the damage process is a phenomenon that is very similar to creep damage which has an exponential relationship to the applied stress and temperature. Based on these observations, the authors propose an HTHA damage assessment procedure that uses the familiar Larson Miller Parameter (LMP) approach and employs the well-known Linear Life Fraction Rule for evaluating operating condition variations in hydrogen partial pressure and temperature.

Creep-Fatigue Interaction Effects On Pressure-Reducing Valve Under Cyclic Thermo-Mechanical Loadings Using Direct Cyclic Method

2021 ◽  
Author(s):  
Nak-Kyun Cho ◽  
Youngjae Choi ◽  
Haofeng Chen
Keyword(s):  
High Temperature ◽  
Power Plant ◽  
Fatigue Failure ◽  
Material Properties ◽  
Structural Integrity ◽  
Direct Method ◽  
Element Model ◽  
Critical Loading ◽  
Creep Fatigue ◽  
Pressure Reducing Valve

Abstract Supercritical boiler system has been widely used to increase efficiency of electricity generation in power plant industries. However, the supercritical operating condition can seriously affect structural integrity of power plant components due to high temperature that causes degradation of material properties. Pressure reducing valve is an important component being employed within a main steam line of the supercritical boiler, which occasionally thermal-fatigue failure being reported. This research has investigated creep-cyclic plastic behaviour of the pressure reducing valve under combined thermo-mechanical loading using a numerical direct method known as extended Direct Steady Cyclic Analysis of the Linear Matching Method Framework (LMM eDSCA). Finite element model of the pressure-reducing valve is created based on a practical valve dimension and temperature-dependent material properties are applied for the numerical analysis. The simulation results demonstrate a critical loading component that attributes creep-fatigue failure of the valve. Parametric studies confirm the effects of magnitude of the critical loading component on creep deformation and total deformation per loading cycle. With these comprehensive numerical results, this research provides engineer with an insight into the failure mechanism of the pressure-reducing valve at high temperature.

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.

A Direct Method on the Evaluation of Cyclic Steady State of Structures With Creep Effect

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
Haofeng Chen ◽  
Weihang Chen ◽  
James Ure
Keyword(s):  
Fatigue Damage ◽  
Mechanical Load ◽  
Direct Method ◽  
Load Condition ◽  
Hysteresis Loops ◽  
Strain Range ◽  
Cyclic Behavior ◽  
Direct Evaluation ◽  
Plastic Strain Range ◽  
Creep Fatigue

This paper describes a new extension of the linear matching method (LMM) for the direct evaluation of cyclic behavior with creep effects of structures subjected to a general load condition in the steady cyclic state, with the new implementation of the cyclic hardening model and time hardening creep constitutive model. A benchmark example of a Bree cylinder and a more complicated three-dimensional (3D) plate with a center hole subjected to cyclic thermal load and constant mechanical load are analyzed to verify the applicability of the new LMM to deal with the creep fatigue damage. For both examples, the stabilized cyclic responses for different loading conditions and dwell time periods are obtained and validated. The effects of creep behavior on the cyclic responses are investigated. The new LMM procedure provides a general purpose technique, which is able to generate both the closed and nonclosed hysteresis loops depending upon the applied load condition, providing details of creep strain and plastic strain range for creep and fatigue damage assessments with creep fatigue interaction.

Progress of EASICS Validation Experiments and Code Comparison of R5, RCC-MRX and ASME III Division V

2021 ◽  
Author(s):  
Peter James ◽  
David Coon ◽  
Colin Austin ◽  
Nicholas Underwood ◽  
Caroline Meek ◽  
...  
Keyword(s):  
High Temperature ◽  
Fatigue Tests ◽  
Guidance Document ◽  
High Temperature Creep ◽  
Temperature Creep ◽  
R Ratio ◽  
Creep Fatigue ◽  
The Uk ◽  
The Impact ◽  
Relevant Component

Abstract The “Establishing AMR Structural Integrity Codes and Standards for UK GDA” (EASICS) project was established in 2019 to help support the acceptance of Advanced Modular Reactors, or AMRs, which are typically based on high temperature Generation IV reactors. The EASICS project is aiming to provide guidance on the requirements for codes and standards for the design of AMRs for use in the UK, to ensure that state-of-the art knowledge will be brought to bear on developing the required design and assessment methodologies. The EASICS project started in July 2019 and is looking to complete by December 2021. To support this aim, the work presented in this paper provides an overview of two interacting aspects of the programme. The first is to perform validation tests for high temperature creep-fatigue assessments of a plant relevant component. The second aspect is to use these results, to provide a comparison of internationally recognised approaches for the assessment of high temperature (creep regime) components. This approach will be repeated for two other case scenarios deemed to be plant relevant components. This paper builds upon the initial overview paper presented at the 2020 conference providing an update on progress. One of the cases presented herein, described as the Thin Walled Welded Pipe Test uses specialist testing of a plant relevant component under high temperature loading conditions is underway with some initial results available. The validation testing includes both fatigue tests and creep-fatigue tests on 316H welded thin section tubes. The tubes have been subjected to strain-controlled tension/compression (R-ratio of −1), with some including a displacement controlled dwell. The tests are being conducted at 525°C. An update to the progress of these tests is included herein. To help enhance interaction with the code bodies, and to understand the impact of differences in the approaches, comparative assessments have been performed when adopting R5, ASME Section III Div 5 and RCC-MRx. One comparison will be based around the tests detailed above (tube test). A further assessment comparison will consider the Evasion mock-up tests provided by CEA (sodium based thermal shock tests). The third assessment case is loosely based around a plant relevant assessment within one of the UK Advanced Gas Reactors (AGRs). This paper provides an overview of the results from all these cases using R5, ASME Section III Div 5 and RCC-MRx. The subsequent discussions covers results, differences and potential impact to the codes which will all help to inform a guidance document to support assessing AMRs within a UK regulatory framework.

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.

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