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.

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.

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.

Assessment of thermal behavior of a cooling system to reduce thermal fatigue cracks in aluminum injection molds

2020 ◽  
pp. 75-86
Author(s):  
Sergio Antonio Camargo ◽  
Lauro Correa Romeiro ◽  
Carlos Alberto Mendes Moraes
Keyword(s):  
Thermal Fatigue ◽  
Cooling System ◽  
Fatigue Cracks ◽  
Cooling Water ◽  
Thermal Conditions ◽  
Thermal Gradients ◽  
Ansys Software ◽  
Cooling Systems ◽  
Thermal Fatigue Cracks ◽  
Number Of Cycles

The present article aimed to test changes in cooling water temperatures of males, present in aluminum injection molds, to reduce failures due to thermal fatigue. In order to carry out this work, cooling systems were studied, including their geometries, thermal gradients and the expected theoretical durability in relation to fatigue failure. The cooling system tests were developed with the aid of simulations in the ANSYS software and with fatigue calculations, using the method of Goodman. The study of the cooling system included its geometries, flow and temperature of this fluid. The results pointed to a significant increase in fatigue life of the mold component for the thermal conditions that were proposed, with a significant increase in the number of cycles, to happen failures due to thermal fatigue.

scholarly journals Multiscale thermomechanical modeling of short fiber-reinforced composites

2017 ◽  
Vol 24 (5) ◽  
pp. 765-772 ◽  
Author(s):  
Dawei Jia ◽  
Huiji Shi ◽  
Lei Cheng
Keyword(s):  
Thermal Loading ◽  
Volume Fraction ◽  
Numerical Procedure ◽  
Thermal Conditions ◽  
Cyclic Hardening ◽  
Short Fiber ◽  
Fiber Reinforced Composites ◽  
Reinforced Composites ◽  
Fiber Reinforced ◽  
Thermomechanical Modeling

AbstractA study of the micromechanical behavior to predict the overall response of short fiber-reinforced composites under cyclic mechanical and thermal loading is presented. The instantaneous average over a “representative volume” of the material is considered. The influence of the short fiber’s aspect ratio, volume fraction, and spatial orientation has been investigated. The linear combined hardening model is used to describe the cyclic hardening effects in the case of metal matrix. A numerical procedure is used to predict the response of composites under mechanical and thermal conditions. The results of the numerical procedure have been compared to the results of three different models and to published experimental data.

An Experimental and Numerical Methodology to Investigate Crack Growth in a 304L Austenitic Stainless Steel Pipe Under Thermal Fatigue

2010 ◽  
Author(s):  
Pauline Bouin ◽  
Antoine Fissolo ◽  
Ce´dric Gourdin
Keyword(s):  
Finite Element ◽  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Crack Growth ◽  
Thermal Fatigue ◽  
Thermal Loading ◽  
Steel Pipe ◽  
Design Stage ◽  
Inner Surface ◽  
Stainless Steel Pipe

This paper covers work carried out by the French Atomic Energy Commission (CEA) to investigate on mechanisms leading to cracking of piping as a result of thermal loading existing in flow mixing zones. The main purpose of this work is to analyse, with a new experiment and its numerical interpretation, and to understand the mechanism of propagation of cracks in such components. To address this issue, a new specimen has been developed on the basis of the Fat3D experiment. This thermal fatigue test consists in heating a 304L steel pre-cracked tube while cyclically injecting ambient water onto its inner surface. The tube is regularly removed from the furnace for a crack characterisation. Finally, the crack growth is evaluated from the crack length differences between two stops. In parallel, a finite element analysis is developed using the finite element Cast3M code. A pipe with a semi-elliptical crack on its inner surface is modelled. A cyclic thermal loading is imposed on the tube. This loading is in agreement with experimental data. The crack propagates through the thickness. A prediction of the velocity of the crack is finally assessed using a Paris’ law type criteria. Finally, this combined experimental and numerical work on 304L austenitic stainless steel pipes will enable to improve existing methods to accurately predict the crack growth under cyclic thermal loadings in austenitic stainless steel pipe at the design stage.

Thermal Fatigue of Pwr Coolant System Loop Drain Lines Due to Outflow Activities

2021 ◽  
Author(s):  
Yue Zou ◽  
Brian Derreberry
Keyword(s):  
Thermal Fatigue ◽  
Operating Experience ◽  
Fatigue Cracking ◽  
Screening Methods ◽  
Primary Coolant ◽  
Pressurized Water ◽  
Thermal Transients ◽  
Piping Systems ◽  
Class 1 ◽  
Coolant System

Abstract Thermal cycling induced fatigue is widely recognized as one of the major contributors to the damage of nuclear plant piping systems, especially at locations where turbulent mixing of flows with different temperature occurs. Thermal fatigue caused by swirl penetration interaction with normally stagnant water layers has been identified as a mechanism that can lead to cracking in dead-ended branch lines attached to pressurized water reactor (PWR) primary coolant system. EPRI has developed screening methods, derived from extensive testing and analysis, to determine which lines are potentially affected as well as evaluation methods to perform evaluations of this thermal fatigue mechanism for the U.S. PWR plants. However, recent industry operating experience (OE) indicate that the model used to predict thermal fatigue due to swirl penetration is not fully understood. In addition, cumulative effects from other thermal transients, such as outflow activities, may also contribute to the failure of the RCS branch lines. In this paper, we report direct OE from one of our PWR units where thermal fatigue cracking is observed at the RCS loop drain line close to the welded region of the elbow. A conservative analytical approach that takes into account the influence of thermal stratification, in accordance with ASME Class 1 piping stress method, is also proposed to evaluate the severity of fatigue damage to the RCS drain line, as a result of transients from outflow activities. Finally, recommendations are made for future operation and inspection based on results of the evaluation.

Evaluation of Susceptibility to Thermal Fatigue Cracking in High Temperature Alloys for Refinery Olefin Applications

2021 ◽  
Author(s):  
Yuxiang Zhang ◽  
Ryan J. Buntain ◽  
Jacob D. Edwards ◽  
Boian Alexandrov ◽  
Jorge Penso
Keyword(s):  
High Temperature ◽  
Thermal Fatigue ◽  
Fatigue Cracking ◽  
High Temperature Alloys
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