scholarly journals Linear Matching Method for Parametric Studies of Weldments Creep-Fatigue Endurance

2013 ◽  
Author(s):  
Yevgen Gorash ◽  
Haofeng Chen
Keyword(s):  
Bending Moment ◽  
Evaluation Procedure ◽  
Geometrical Parameters ◽  
Matching Method ◽  
Individual Parameter ◽  
Creep Fatigue ◽  
Parametric Studies ◽  
Fatigue Evaluation ◽  
Fatigue Endurance ◽  
Linear Matching Method

This paper presents parametric studies on creep-fatigue endurance of the steel AISI type 316N(L) weldments defined as types 1, 2 and 3 according to R5 Vol. 2/3 Procedure classification at 550°C. The study is implemented using the Linear Matching Method (LMM) and based upon previously developed creep-fatigue evaluation procedure considering time fraction rule. Several geometrical configurations of weldments with individual parameter sets, representing different fabrication cases, are developed. For each of configurations, the total number of cycles to failure N* in creep-fatigue conditions is assessed numerically for different loading cases. The obtained set of N* is extrapolated by the analytic function dependent on normalised bending moment M̃, dwell period Δt and geometrical parameters. Proposed function for N* shows good agreement with numerical results obtained by the LMM. Therefore, it is used for the identification of Fatigue Strength Reduction Factors (FSRFs) intended for design purposes and dependent on proposed variable parameters.

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 Novel Fatigue Evaluation Approach with Direct Steady Cycle Analysis (DSCA) Based on the Linear Matching Method (LMM)

2019 ◽  
Vol 795 ◽  
pp. 383-388 ◽  
Author(s):  
Xiao Tao Zheng ◽  
Zhi Yuan Ma ◽  
Hao Feng Chen ◽  
Jun Shen
Keyword(s):  
Fatigue Life ◽  
Evaluation Method ◽  
Low Cycle Fatigue ◽  
Effective Strain ◽  
Strain Range ◽  
Matching Method ◽  
Evaluation Approach ◽  
Perfectly Plastic ◽  
Fatigue Evaluation ◽  
Linear Matching Method

The traditional Low Cycle Fatigue (LCF) evaluation method is based on elastic analysis with Neuber’s rule which is usually considered to be over conservative. However, the effective strain range at the steady cycle should be calculated by detailed cycle-by-cycle analysis for the alternative elastic-plastic method in ASME VIII-2, which is obviously time-consuming. A Direct Steady Cycle Analysis (DSCA) method within the Linear Matching Method (LMM) framework is proposed to assess the fatigue life accurately and efficiently for components with arbitrary geometries and cyclic loads. Temperature-dependent stress-strain relationships considering the strain hardening described by the Ramberg-Osgood (RO) formula are discussed and compared with those results obtained by the Elastic-Perfectly Plastic (EPP) model. Additionally, a Reversed Plasticity Domain Method (RPDM) based on the shakedown and ratchet limit analysis method and the DSCA approach within the LMM framework (LMM DSCA) is recommended to design cyclic load levels of LCF experiments with predefined fatigue life ranges.

scholarly journals Evaluation of Primary-Load Effects on Creep-Fatigue Life of Alloy 617 Using Simplified Model Test Method

2021 ◽  
Author(s):  
Yanli Wang ◽  
Peijun Hou ◽  
Robert I. Jetter ◽  
T.-L. Sham
Keyword(s):  
Fatigue Life ◽  
Internal Pressure ◽  
Model Test ◽  
Test Method ◽  
Simplified Model ◽  
Evaluation Procedure ◽  
Alloy 617 ◽  
Creep Fatigue ◽  
Fatigue Evaluation ◽  
Primary Load

Abstract Current creep-fatigue evaluation approaches based on the creep-fatigue Damage-diagram are complex and very conservative. Simplified Model Test (SMT) method is an alternative approach to determine cyclic life at elevated temperatures. The SMT-based creep-fatigue evaluation methodology avoids parsing the damage into creep and fatigue components and greatly simplifies the evaluation procedure for elevated-temperature cyclic service. In this study, the effects of sustained primary-stress loading are evaluated in support of the development of SMT-based creep-fatigue design curves for Alloy 617. Experiments were designed and performed using internal pressurized tubular specimens at 950 °C on Alloy 617. The sustained primary-load was introduced by the internal pressure. A newly developed SMT technique, single-bar SMT, was extended to these tests and SMT creep-fatigue test data were generated with various elastic follow-ups, internal pressures and strain ranges. The test results from this study along with the original SMT data on Alloy 617 demonstrate that, although internal pressure is within the allowable stress limit per ASME Section III Division 5 Code Case N-898, the SMT creep-fatigue cycles to failure were reduced for the cases tested with primary-pressure load. The reduction of SMT creep-fatigue life due to primary-load was found to be dependent on strain ranges and elastic follow up. Approaches to handle the primary-load effect on SMT design curves are discussed.

Creep-Cyclic Plasticity and Damage Assessment of an SS304 Weldolet

2021 ◽  
Author(s):  
Manu Puliyaneth ◽  
Haofeng Chen
Keyword(s):  
Thermal Load ◽  
Damage Assessment ◽  
Creep Behaviour ◽  
Life Assessment ◽  
Cyclic Plasticity ◽  
Matching Method ◽  
Damage Mechanisms ◽  
Creep Fatigue ◽  
Dwell Period ◽  
Linear Matching Method

Abstract Creep-fatigue and creep-ratcheting life assessment of an SS304 weldolet considering full creep-cyclic plasticity interaction is investigated using the extended Direct Steady Cycle Analysis (eDSCA) within the Linear Matching Method Framework (LMMF). The creep behaviour is modelled using the Norton relationship, which is modified by the Arrhenius rule to account for the temperature variation within the weldolet. The introduction of a creep dwell increases the reverse plasticity resulting from the creep relaxation. This leads to both creep-fatigue and creep-ratcheting damage mechanisms at different regions within the weldment. For thermal load dominated loading combinations, creep ratcheting due to both cyclically enhanced creep and creep enhanced plasticity are observed based on the dwell period. The effect of dwell period, load and temperature on the creep-fatigue and creep-ratcheting interaction of a weldolet are presented. The simultaneous presence of various damage mechanisms at different locations within the weldment highlights the importance and requirement of the proposed creep-cyclic plasticity investigations at weld locations.

The Application of the Linear Matching Method to the Life Assessment Method R5: A Comparison

2005 ◽  
Author(s):  
Haofeng Chen ◽  
A. R. S. Ponter ◽  
R. A. Ainsworth
Keyword(s):  
Failure Modes ◽  
Limit Load ◽  
Detailed Comparison ◽  
Assessment Method ◽  
Life Assessment ◽  
Distinct Advantage ◽  
Matching Method ◽  
Creep Fatigue ◽  
Linear Matching Method

The Life Assessment Method R5 is widely used for the assessment of power plant at high temperatures. The procedure involves the application of a sequence of rules that provide margins of safety against a range of possible failure modes, plastic collapse, ratchetting, fatigue failure, creep rupture and creep/fatigue interaction. Within R5 this is achieved by using limit load and shakedown methods, combined with Neuber’s rule and the evaluation of elastic follow-up factors. In recent years, the Linear Matching Method has been developed so that it is capable of providing optimal solutions for each of these criteria, thereby giving less conservative margins of safety, but adopting the same use of material data as R5. The paper describes a detailed comparison between the approach currently used in R5 and the result of the application of the Linear Matching Method, for the entire range of failure modes and for a simple example. The purpose of this comparison is to assess the circumstances where Linear Matching Methods may have a distinct advantage over current methods. The example consists of a square plate containing a circular hole. The plate is subjected to uniaxial loading and a radial varying temperature field. For all failure modes the Linear Matching Method gives less conservative results compared with standard R5 methods. The differences can be very significant, particularly for the prediction of strength limits; limit load, shakedown load and ratchet limit. Significantly lower and less conservation elastic follow-up factors were also obtained. The comparison demonstrates the advantages of the Linear Matching Method in this context.

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