Critical Remarks on the Validity of Fatigue Life Evaluation Methods Based on Local Stress-Strain Behavior

2009 ◽  
pp. 209-209-15
Author(s):  
D Schutz ◽  
JJ Gerharz
Keyword(s):  
Fatigue Life ◽  
Local Stress ◽  
Evaluation Methods ◽  
Stress Strain ◽  
Strain Behavior ◽  
Life Evaluation ◽  
Fatigue Life Evaluation

Comparison of Creep-Fatigue Evaluation Methods With Notched Specimens Made of Mod.9Cr-1Mo Steel

2011 ◽  
Author(s):  
Masanori Ando ◽  
Yuichi Hirose ◽  
Takanori Karato ◽  
Sota Watanabe ◽  
Osamu Inoue ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Fast Reactor ◽  
Evaluation Methods ◽  
Fatigue Tests ◽  
Test Results ◽  
Notched Specimens ◽  
Life Evaluation ◽  
Creep Fatigue ◽  
Fatigue Life Evaluation

In a component design at elevated temperature, creep-fatigue is one of the most important failure modes, and assessment of creep-fatigue life in structural discontinuity is important issue to evaluate structural integrity of the components. Therefore a lot of creep-fatigue life evaluation methods were proposed until now. To compare and assess these evaluation methods, a series of creep-fatigue tests was carried out with notched specimens. All the specimens were made of Mod.9Cr-1Mo steel, which it is a candidate material for a primary and secondary heat transport system components of JSFR (Japan Sodium-cooled Fast Reactor). Mechanical creep-fatigue tests and thermal creep-fatigue tests were performed by using conventional uni-axial push-pull fatigue test machine and thermal gradient generating system with an induction heating coil. Stress concentration levels were adjusted by varying the diameters of notch roots in the both tests. In the test, creep-fatigue lives, crack initiation and propagation processes were observed by digital micro-scope and replica method. Besides those, a series of elastic Finite Element Analysis (FEA) were carried out to predict the number of cycles to failure by several creep-fatigue life evaluation methods. Then these predictions were compared with test results. Several types of evaluation methods which are stress redistribution locus (SRL) method, simple elastic follow-up method and the methods described in JSME FR (Fast Reactor) code were applied. The applicability and conservativeness of these methods were discussed. It was appeared that SRL method gave rational prediction of creep-fatigue life with conservativeness when the factor of κ = 1.6 was applied for all the conditions tested in this study. Comparison of SRL method and simple elastic follow-up method indicated that SRL method applied factor of κ = 1.6 gave the smallest creep-fatigue life in practicable stress level. JSME FR code gave an evaluation 70∼100 times conservative lives comparing with the test results.

Fatigue Life Evaluation for Notched Components of Automatic Transfer Devices

2006 ◽  
Vol 324-325 ◽  
pp. 1269-1272
Author(s):  
Young Woo Choi ◽  
Byeong Wook Noh ◽  
Kyung Chun Ham ◽  
Sung In Bae
Keyword(s):  
Fatigue Life ◽  
Residual Life ◽  
Notch Root ◽  
Local Stress ◽  
Special Method ◽  
Stress Concentrations ◽  
Real Component ◽  
Element Analysis ◽  
Life Evaluation ◽  
Fatigue Life Evaluation

In this study, the fatigue life evaluation of automatic transfer devices under stress concentrations due to the notch effect is performed. To investigate residual life of a notched component, load histories were obtained through strain measurement. A fatigue test was performed on a specimen imitating a real component and results were compared with each notch root radius of the concentration area. Three-dimensional finite element analysis was also performed to evaluate the local stress fields. Miner’s rule was used to predict the fatigue life calculation. As a result, the predicted life of a notched component was in good agreement with a real component and introduced a special method for measuring load using real machine components.

Is it Possible to Get-Rid of S-N Curve for Fatigue Evaluation?: A Fully Mechanistic Model of 316SS Reactor Steel for Fatigue Life Evaluation

2017 ◽  
Author(s):  
Bipul Barua ◽  
Subhasish Mohanty ◽  
William K. Soppet ◽  
Saurindranath Majumdar ◽  
Krishnamurti Natesan
Keyword(s):  
Fatigue Life ◽  
3D Structure ◽  
Cyclic Plasticity ◽  
Fe Model ◽  
Plasticity Model ◽  
Modeling Framework ◽  
Stress Strain ◽  
Life Evaluation ◽  
Fatigue Life Evaluation ◽  
Cyclic Plasticity Model

The present methods for fatigue life evaluation of nuclear reactor components have large uncertainties due to the overdependence on approaches that involve empirical fatigue life estimation, such as use of test-based curves of stress/strain versus life (S∼N) and Coffin-Manson type empirical relations. To reduce the uncertainty in fatigue life evaluation, we are trying to develop a fully mechanistic modeling approach. The aim is to capture the time/cycle-dependent material ageing behavior such as stress hardening/softening through multi-axial stress-strain evolution of the components based on which the life of the component can be predicted. In this paper, we introduce an implementation of the ANL developed evolutionary cyclic plasticity model for 316 SS reactor steel within the commercial finite element (FE) software ABAQUS. A user subroutine is developed to enable the incorporation of the ANL developed evolutionary cyclic plasticity model [1] into ABAQUS. The FE model, developed in this work, can be used for predicting the time-dependent stress hardening/softening of 3D structure. A strain-controlled constant amplitude fatigue experiment scenario is 3D modeled using the developed ABAQUS based FE modeling framework and is verified through experimental data.

Comparison and Assessment of the Creep-Fatigue Evaluation Methods With Notched Specimen Made of Mod.9Cr-1Mo Steel

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
Masanori Ando ◽  
Yuichi Hirose ◽  
Takanori Karato ◽  
Sota Watanabe ◽  
Osamu Inoue ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Fatigue Test ◽  
Fast Reactor ◽  
Evaluation Methods ◽  
Test Machine ◽  
Test Results ◽  
Life Evaluation ◽  
Creep Fatigue ◽  
Fatigue Life Evaluation

In components design at elevated temperature, creep-fatigue is one of the most important failure modes, and assessment of creep-fatigue life in structural discontinuities is an important issue in evaluating the integrity of components. Therefore, a lot of creep-fatigue life evaluation methods were proposed until now. To compare and assess the evaluation methods, a series of creep-fatigue test was carried out with notched specimens. All the specimens were made of Mod.9Cr-1Mo steel, which is a candidate material for primary and secondary heat transport system components of the Japan sodium-cooled fast reactor (JSFR). Mechanical creep-fatigue tests and thermal creep-fatigue test were performed by using a conventional uni-axial push–pull fatigue test machine and a thermal gradient generating system with an induction heating. The stress concentration levels were adjusted by varying the notch radius in the each test. The creep-fatigue lives, crack initiation, and propagation processes were monitored by a digital microscope and the replica method. A series of finite element analysis (FEA) was carried out to predict the number of cycles to failure by the several creep-fatigue life evaluation methods. Then, these predictions were compared with the test results. Several types of evaluation methods such are stress redistribution locus (SRL) method, simple elastic follow-up method and the methods described in the design and constriction code for fast reactor (FR) published by the Japan Society of Mechanical Engineers (JSME FRs code) were applied. Through the comparisons, it was appeared that SRL method gave rational conservative prediction of the creep-fatigue life when the factor of κ = 1.6 was applied for all conditions tested in this study. A comparison of SRL method and simple elastic follow-up method indicated that SRL method applied factor of κ = 1.6 gave the smallest creep-fatigue life in practicable stress range level. The JSME FRs code gave an evaluation 70–100 times conservative lives comparing with the test results.

A Study on Fatigue Life Evaluation of Pressure Vessel Made of ASME SA240-316L Material Using Numerical Analysis

2019 ◽  
Vol 893 ◽  
pp. 1-5 ◽  
Author(s):  
Eui Soo Kim
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Pressure Vessel ◽  
Life Prediction ◽  
Pressure Vessels ◽  
Physical Damage ◽  
Element Analysis ◽  
Internal Damage ◽  
Life Evaluation ◽  
Fatigue Life Evaluation

Pressure vessels are subjected to repeated loads during use and charging, which can causefine physical damage even in the elastic region. If the load is repeated under stress conditions belowthe yield strength, internal damage accumulates. Fatigue life evaluation of the structure of thepressure vessel using finite element analysis (FEA) is used to evaluate the life cycle of the structuraldesign based on finite element method (FEM) technology. This technique is more advanced thanfatigue life prediction that uses relational equations. This study describes fatigue analysis to predictthe fatigue life of a pressure vessel using stress data obtained from FEA. The life prediction results areuseful for improving the component design at a very early development stage. The fatigue life of thepressure vessel is calculated for each node on the model, and cumulative damage theory is used tocalculate the fatigue life. Then, the fatigue life is calculated from this information using the FEanalysis software ADINA and the fatigue life calculation program WINLIFE.

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