scholarly journals Studying the Effect of Thermal Fatigue on Multiple Cracks Propagating in an SS316L Thin Flange on a Shaft Specimen Using a Multi-Physics Numerical Simulation Model

2019 ◽  
pp. 565-573 ◽  
Author(s):  
Fariha Mukhtar ◽  
Faisal Qayyum ◽  
Hassan Elahi ◽  
Masood Shah
Keyword(s):  
Numerical Simulation ◽  
Crack Propagation ◽  
Simulation Model ◽  
Thermal Fatigue ◽  
Power Plants ◽  
Thermal Loading ◽  
Plastic Material ◽  
Fatigue Cracking ◽  
Fatigue Loading ◽  
Multiple Cracks

After more than a decade of research on thermal fatigue cracking in nuclear reactor components, the science remains incomplete. It is essential to understand the crack propagation behaviour and the influence of multiple cracks on the fatigue life of a component due to thermal fatigue load. Accurate numerical simulation modelling can help in better understanding the influence of different factors on failure propagation. In this research, a finite element-based numerical simulation model has been developed using ABAQUS commercial software to obtain insight into crack propagation and crack arrest in an SS316L thin flange on shaft specimen; the assembly is cooled internally, and cyclic thermal loading is applied on the flange rim. The experiment was carried out on a specially designed rig using an induction coil for heating the outer rim. Thermocouples were attached radially on the rim to collect detailed temperature profiles. Real-time temperature-dependent elastic-plastic material data was used for modelling. The boundary conditions and thermal profile used for the numerical model were matched with experimental data. The stresses responsible for crack initiation, the effect of crack number and crack lengths on stresses, energy absorbed at the crack tip after every thermal cycle and the threshold values of cracks are evaluated in the current work. The obtained simulation results were validated by comparing experimental observations. The developed simulation model helps in better understanding the evolution of stresses and strains in uncracked and cracked SS316L discs mounted on a flange due to thermal cycling. It also helped in better understanding the crack propagation behaviour and the evolution of energy release at crack tips. Such a model can help future researchers in designing components undergoing thermal fatigue loading, for example, in nuclear power plants.

Example Application of Code Case N-894 Rules for Weld Overlay of Thermal Fatigue Cracking

2020 ◽  
Author(s):  
Christopher Lohse ◽  
Richard Bax ◽  
Minji Fong ◽  
Charles Fourcade ◽  
Do Jun Shim
Keyword(s):  
Stainless Steel ◽  
Thermal Fatigue ◽  
Thermal Loading ◽  
Fatigue Cracking ◽  
Fatigue Loading ◽  
Pressurized Water ◽  
Weld Overlay ◽  
Water Reactors ◽  
Filler Metals ◽  
Weld Overlays

Abstract The ASME Code, Section XI is working on guidance for application of weld overlay repairs to repair thermal fatigue cracking in nuclear piping systems. This new guidance will eventually be published as Code Case N-894 with the original technical basis in PVP2019-93360. Weld overlays have been extensively used in boiling water reactors (BWRs) and pressurized water reactors (PWRs) to mitigate stress corrosion cracking (SCC). The weld overlays applied to date mitigate SCC by putting the flaw into compression and they use materials that are resistant to SCC. Mitigation of thermal fatigue requires the crack to be in compression so that it does not achieve tensile cycling under the thermal fatigue loading condition. Code Case N-894 allows for the use of either stainless steel or nickel alloy filler metals to repair thermal fatigue flaws. This paper will evaluate the use of both filler metals for the weld overlay process to assess the performance difference between the two filler metals such that the welding advantages of stainless steel over nickel alloys can be quantified. Specifically, this paper assesses the residual stress state difference for nominal sized weld overlays on a six-inch pipe. Various cyclic thermal loading conditions are postulated, and the stress intensity factors are determined for both filler metals to assess the difference in mitigation of thermal fatigue flaws.

Investigation of Thermal Fatigue Cycling in Drain Lines

2007 ◽  
Author(s):  
Robert O. McGill ◽  
Arthur F. Deardorff ◽  
David W. Peltola ◽  
Shannon Chu
Keyword(s):  
Thermal Fatigue ◽  
Thermal Stratification ◽  
Thermal Loading ◽  
Small Diameter ◽  
Fatigue Cracking ◽  
Thermal Conditions ◽  
Cyclic Behavior ◽  
Bending Moments ◽  
Model Predictions ◽  
Insight Into

Several instances of thermal fatigue cracking in small-diameter PWR branch lines off reactor main loop piping led to an industry program to evaluate the loading mechanisms responsible for the cracking. It was found that swirl penetration of hot reactor coolant into the normally stagnant drain lines can result in cyclic thermal stratification in the horizontal run of the drain driving the thermal loading. Models were developed to predict the thermal conditions and cyclic behavior that resulted in the cracking. Thermal transient and stress analysis was conducted to test the model predictions and to assure that cracking could be predicted. Further review was conducted for the related piping events where leakage had occurred. These investigations provided considerable insight into how to evaluate the larger populations of lines in operating plants where there have been no indications of cracking. These investigations have shown that two cases of cracking were due to un-insulated configurations that resulted in high cycling temperature differentials in the region of cracking. In addition, the lines where cracking occurred had rigid vertical supports in the region of stratification, leading to high elbow bending moments as a result of the constraint.

Analysis of Thermal Fatigue Distress of Asphalt Concrete Pavements

1996 ◽  
Vol 1545 (1) ◽  
pp. 43-49 ◽  
Author(s):  
N. Mike Jackson ◽  
Ted S. Vinson
Keyword(s):  
Thermal Fatigue ◽  
Asphalt Concrete ◽  
Thermal Loading ◽  
Test Procedure ◽  
Fatigue Cracking ◽  
Thermal Cracking ◽  
The United States ◽  
Tensile Creep ◽  
Concrete Pavements ◽  
Test Procedures

Thermal cracking of asphalt concrete pavements is responsible for millions of dollars in annual maintenance and rehabilitation costs in the United States and Canada. Thermal cracking typically is associated with low temperatures in northern climates and at high elevations. Another form of thermal cracking, known as thermal fatigue cracking, has been proposed by several researchers as a potential mode of distress in regions with relatively moderate climates. The objectives were to evaluate the possibility of the occurrence of the thermal fatigue cracking mode of distress and to identify a suitable laboratory test procedure to facilitate a mechanistic analysis of this mode of distress. The most promising test procedures evaluated included the direct tensile creep test and the thermal stress restrained specimen test. The results suggest that thermal fatigue distress in asphalt concrete mixtures is not a viable mode of distress in the absence of environmental aging. From the data presented and results documented by others, it is evident that distress often attributed to thermal fatigue cracking is more likely the result of low-temperature cracking of environmentally aged mixtures or subgrade-related distress. It is concluded that fatigue distress due to thermal loading of semirestrained pavements does not occur.

Numerical Evaluation of Wall Temperature Measurement Methods Developed to Investigate Thermal Fatigue at T-Junction Pipe

2012 ◽  
Author(s):  
Koji Miyoshi ◽  
Akira Nakamura ◽  
Nobuyuki Takenaka
Keyword(s):  
Numerical Simulation ◽  
Thermal Fatigue ◽  
Temperature Fluctuation ◽  
Fatigue Cracking ◽  
Temperature Fluctuations ◽  
Measured Data ◽  
Inner Surface ◽  
Simulation Results ◽  
The Difference ◽  
Sinusoidal Temperature

Thermal fatigue cracking may initiate at a T-junction pipe where high and low temperature fluids flow in from different directions and mix. Thermal stress is caused by a temperature gradient in a structure and its variation. The accurate simulation of the temperature distribution in structures is, therefore, important for estimating thermal fatigue. In this study, an experimental method using a T-junction pipe with thermocouples was developed. Wall temperatures in the experiment have to be obtained at the inner surface of the pipe to validate numerical simulation results. The difference of position between the inner surface and the measurement point where using thermocouples may, however, have an effect on temperature data. The numerical simulation results showed that the amplitude of temperature fluctuations was reduced to 54% and the difference of phase was 0.91 radians when the sinusoidal temperature fluctuation of 5Hz was applied from the inner surface to the thermocouple measurement points. These results showed that wall temperatures at the inner surface should be estimated from measured data obtained by the thermocouples. A transfer function was, therefore, obtained to calculate wall temperatures at the inner surface from measured data. In addition, the numerical simulation results showed that the amplitude and the phase of temperature fluctuations differed depending on existence of voids around thermocouples. Respective differences of it in the amplitude and the phase were about 5% and 3% when the sinusoidal temperature fluctuation of 5Hz was applied at the inner surface. These results showed that thermocouples should be installed in pipes without voids to measure accurate temperature fluctuations. A mock-up test showed that voids stayed behind the thermocouples when the thermocouples were brazed into the pipe wall at atmospheric pressure, but the voids disappeared when thermocouples were brazed in a vacuum atmosphere into the inner surface of the pipe.

Field and Theoretical Evaluation of Thermal Fatigue Cracking in Flexible Pavements

2005 ◽  
Vol 1919 (1) ◽  
pp. 87-95 ◽  
Author(s):  
Imad L. Al-Qadi ◽  
Marwa M. Hassan ◽  
Mostafa A. Elseifi
Keyword(s):  
Thermal Fatigue ◽  
Thermal Loading ◽  
High Stress ◽  
Fatigue Cracking ◽  
Field Measurements ◽  
Flexible Pavement ◽  
Heat Transfer Analysis ◽  
Experimental Program ◽  
Fe Model ◽  
Pavement Response

Thermal cracking in flexible pavement occurs when the tensile stress exceeds the tensile strength of hot-mix asphalt at a given temperature or when fluctuating stresses and strains caused by temperature variation lead to a buildup of irrecoverable deformations over time. The objective of this study was twofold: ( a) to quantify the measured strain magnitude associated with thermal fatigue through field measurements and ( b) to present a three-dimensional, finite element (FE) model that accurately simulated thermal fatigue in flexible pavement. Results of the experimental program indicated that pavement response to thermal loading was associated with a high strain range, reaching a maximum recorded value of 350 μm/m. This finding confirms the hypothesis that the criticality of thermal fatigue arises from the high stress–strain level exhibited in each cycle rather than its frequency, which is usually the critical factor in load-associated fatigue cracking. Moreover, the developed FE model accurately simulated pavement response to thermal loading by conducting a sequential coupled heat transfer analysis. Results of the developed FE model were in agreement with field measurements and demonstrated the model's capability to simulate both the temperature and stress fields associated with thermal loading. This model may be used to evaluate pavement performance against transverse cracking induced by thermal fatigue.

Analysis of the Thermal Fatigue Cracking of 316L Model Pipe Components at Fast Reactor Temperatures

2011 ◽  
Author(s):  
Elena Paffumi ◽  
Karl-Fredrik Nilsson
Keyword(s):  
Fatigue Damage ◽  
Thermal Fatigue ◽  
Nuclear Power ◽  
Power Plants ◽  
Tensile Load ◽  
Fatigue Cracking ◽  
Experimental Conditions ◽  
Additional Constant ◽  
Maximum Temperatures ◽  
High Cycle Thermal Fatigue

In order to assess the high-cycle thermal fatigue damage risk of the nuclear power plants mixing zones, the knowledge of the temperature fluctuations effect on the structure surface is necessary. To advance the accuracy and reliability of thermal fatigue load determination, a combined experimental and numerical investigation has been conducted on cylindrical components of 316L stainless steel subject to cyclic thermal shocks of varying intensity. Slightly different experimental conditions were applied in each test to explore the effect of ΔTmax values of increasing severity, addressing also higher temperatures typical for fast reactors, the effect of a superimposed static axial load to study the effect of a constant pressure on the thermal fatigue damage and a reduced test piece wall thickness. A comparison between thermal down-shock tests with and without additional constant tensile load and with different maximum temperatures are analysed in details here below.

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