Development of Fatigue Crack Growth Prediction Model in Reactor Coolant Environment

2018 ◽  
Vol 140 (4) ◽  
Author(s):  
Terushi Ishizawa ◽  
Satoshi Takeda ◽  
Takanori Kitada ◽  
Takao Nakamura ◽  
Masayuki Kamaya
Keyword(s):  
Crack Initiation ◽  
Crack Growth ◽  
Strain Range ◽  
Crack Size ◽  
Growth Behavior ◽  
Crack Coalescence ◽  
Reactor Coolant ◽  
Crack Growth Curve ◽  
Fatigue Life Reduction ◽  
The Relationship

In order to conduct effective and rational maintenance activity of components in nuclear power plants, it is proposed to manage fatigue degradation based on crack size corresponding to an extent of cumulative fatigue effect. This study is aimed at developing a prediction model for fatigue crack growth in simulated reactor coolant environment. In order to investigate influence of reactor coolant environment on crack initiation and crack growth, two-step replica observations were conducted for environmental fatigue test specimens (type 316 stainless steel) subjected to three kinds of strain range. Crack initiation, growth, and coalescence were observed in the experiments. It is clarified that crack coalescence is one of the dominant factors causing fatigue life reduction, and fatigue life reduction depends on crack size and distance of two coalescing cracks. Then, a model was developed for predicting statistical crack initiation and growth behavior. The relationship between dispersion of crack initiation life and strain range was approximated by the Weibull model to predict crack initiation. Then, the statistical crack growth was modeled using the relation of crack growth rate and strain intensity factor. Furthermore, the crack coalescence was taken into account to the crack growth prediction considering the distance between two cracks. Finally, the crack growth curve, which is the relationship between crack size and operation period, was derived through Monte Carlo simulation with the developed model. The crack growth behavior and residual life in the simulated reactor coolant environment can be reviewed by the crack growth curve obtained with crack initiation, and the growth model developed was compared with the fatigue test results.

Effects of Loading Spectra on High pH Crack Growth Behavior of X65 Pipeline Steel

CORROSION ◽  
10.5006/3472 ◽  
2020 ◽  
Vol 76 (6) ◽  
pp. 601-615 ◽  
Author(s):  
Hamid Niazi ◽  
Karina Chevil ◽  
Erwin Gamboa ◽  
Lyndon Lamborn ◽  
Weixing Chen ◽  
...  
Keyword(s):  
Free Surface ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Strain Rate ◽  
Crack Growth ◽  
Pipeline Steel ◽  
Crack Tip ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Secondary Crack

The effects of mechanical factors on crack growth behavior during the second stage of high pH stress corrosion cracking in pipeline steel were investigated by applying several loading scenarios on compact tension (CT) specimens. The main mechanism for stage 2 of intergranular crack propagation is anodic dissolution ahead of the crack tip which is highly dependent on crack-tip strain rate. The maximum and minimum crack growth rates were 3 × 10−7 mm/s and 1 × 10−7 mm/s, respectively. It was observed that several factors such as mean stress intensity factor, amplitude, and frequency of loading cycles determine the crack-tip strain rate. Low R-ratio cycles, particularly high-frequency ones, enhance secondary crack initiation, and crack coalescence on the free surface. This mechanism accelerates crack advance on the free surface which is accompanied with an increase in mechanical driving force for crack propagation in the thickness direction. These findings have implications for pipeline operators and could be used to increase the lifespan of the cracked pipelines at stage 2. For those pipelines, any loading condition that increases the strain rate ahead of the crack tip enhances anodic dissolution and is detrimental. Additionally, secondary crack initiation and coalescence could be minimized by avoiding internal pressure fluctuation, particularly rapid large pressure fluctuations.

A Flaw Tolerance Concept for Plant Maintenance Using Virtual Fatigue Crack Growth Curve

2013 ◽  
Author(s):  
Masayuki Kamaya ◽  
Takao Nakamura
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Curve ◽  
Growth Behavior ◽  
Plant Design ◽  
Flaw Tolerance ◽  
Plant Maintenance ◽  
Crack Growth Curve

Incorporation of the flaw tolerance concept in plant design and maintenance is discussed in order to consider the reduction in fatigue life due to the high-temperature water environment of class 1 components of NPPs. The flaw tolerance concept has been included in Section XI of the ASME BPVC. The structural factor (safety factor) for the flaw evaluation is considered in the stress, whereas it was considered in the design fatigue curve in Section III of the ASME BPVC. In order to apply the flaw tolerance concept to plant design and maintenance, it is necessary to assume the crack initiation and growth behavior. In this study, first, crack initiation and growth behavior during fatigue tests was reviewed and a relationship between the crack growth and fatigue life was quantified. Then, the safety factor was considered in the crack growth curve. It was shown that the crack size could be correlated to the usage factor and the flaw tolerance concept was reasonably considered in the plant maintenance by using the proposed virtual fatigue crack growth curve.

Study on the Influence of Strain Rate on Crack Initiation and Growth in Simulated Reactor Coolant Environment of Type 316 Stainless Steel

2018 ◽  
Author(s):  
Takahisa Nose ◽  
Takao Nakamura ◽  
Takanori Kitada
Keyword(s):  
Crack Initiation ◽  
Strain Rate ◽  
Nuclear Power ◽  
Power Plants ◽  
Fatigue Crack Initiation ◽  
Crack Size ◽  
Strain Rates ◽  
3 Dimensional ◽  
Reactor Coolant ◽  
Cumulative Fatigue Damage

In order to conduct effective and rational maintenance activity of components in nuclear power plants, it is proposed to manage fatigue degradation based on crack size corresponding to an extent of cumulative fatigue damage. The purpose of this study focuses on the influence of strain rate in simulated reactor coolant environment for fatigue crack initiation and growth. 3-dimensional replica observations were conducted for environmental fatigue test specimens in different strain rates. Crack initiation and growth were observed in the experiments. It is clarified that low strain rate influences crack propagation and coalescence and increases crack growth rate that finally decrease fatigue life.

Study on the Influence of Crack Growth Behavior on Fatigue Life in Simulated Reactor Coolant Environment of Different Temperature

2020 ◽  
Author(s):  
Tatsuru Misawa ◽  
Takanori Kitada ◽  
Takao Nakamura
Keyword(s):  
High Temperature ◽  
Fatigue Life ◽  
Crack Propagation ◽  
Crack Growth ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Reactor Coolant ◽  
Different Temperatures

Abstract It has been clarified that the fatigue life is decreased in the fatigue test of high-temperature and high-pressure water that simulates PWR reactor coolant environment compared to that in the atmosphere. Temperature, strain rates, dissolved oxygen concentration, etc. affect the decrease of fatigue life. The influence of crack growth behavior on the fatigue life of Type 316 austenitic stainless steel [1] in simulated PWR reactor coolant environment of different temperatures was investigated in this study. Fatigue tests were conducted under different temperatures (200°C and 325°C) in a simulated PWR reactor coolant environment with interrupting, and cracks generated on the specimen surface were observed with two-step replica method. From the results of observation, the influence of crack growth behavior in different temperatures on the fatigue life was clarified. As a result, it was confirmed that the decrease of the fatigue life due to high temperature is mainly caused by the acceleration of crack propagation rate in the depth direction by the increase of crack coalescence frequency due to the increase of crack initiation number and crack propagation rate in the length direction.

Non-Relaxing Crack Growth and Fatigue in a Non-Crystallizing Rubber

1974 ◽  
Vol 47 (5) ◽  
pp. 1253-1264 ◽  
Author(s):  
P. B. Lindley
Keyword(s):  
Crack Growth ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Maximum Deformation ◽  
Fatigue Data ◽  
Tentative Explanation ◽  
Tearing Energy ◽  
Relationship Of ◽  
The Relationship ◽  
Unique Relationship

Abstract The crack growth behavior of a non-crystallizing rubber, SBR, is investigated in terms of the tearing energy T, the energy available for crack growth. For cyclic deformations in which the minimum tearing energy is zero (relaxing conditions), a unique relationship is obtained between the growth per cycle and T at the maximum deformation. This rubber also exhibits crack growth at constant tearing energies. The relationship of the crack growth rate as a function of tearing energy, when the minimum tearing energy of the cycle is not zero, can be superimposed on the relaxing relationship by scaling the rates, and a tentative explanation is proposed for the scaling factor. Fatigue data are consistent with this.

Crack Growth Characteristics of Pure Copper for Smart Stress Memory Patch

2007 ◽  
Vol 353-358 ◽  
pp. 2045-2048
Author(s):  
Shoichi Nambu ◽  
Manabu Enoki
Keyword(s):  
Crack Propagation ◽  
Crack Length ◽  
Crack Growth ◽  
Stress Amplitude ◽  
Pure Copper ◽  
Growth Behavior ◽  
Growth Characteristics ◽  
Crack Growth Behavior ◽  
Stress Memory ◽  
The Relationship

A new sensing method called “smart stress memory patch”, which could estimate the maximum stress, the stress amplitude and the fatigue cyclic number simultaneously using Kaiser effect of Acoustic Emission (AE) and crack length of this patch, was developed. In this study, the crack growth characteristics of this patch was evaluated. Pure copper was used for this patch because its good corrosion resistance, stable crack propagation and so on. Two kinds of samples which were rolled and electrodeposited copper were prepared to investigate the effect of microstructure on crack growth behavior. Fatigue test was performed under constant stress amplitude to evaluate the crack growth behavior using the relationship between stress intensity factor range and crack propagation rate. The scattering in fatigue crack growth was also investigated to obtain the relationship between crack length and the fatigue cyclic number including two-sided 95% confidence interval. The effect of thickness and grain size on the scattering was discussed. Finally, good crack growth behavior was obtained and the fatigue cyclic number could be estimated by this patch.

A Probabilistic Micromechanical Code for Predicting Fatigue Life Variability: Model Development and Application

2005 ◽  
Vol 128 (4) ◽  
pp. 889-895 ◽  
Author(s):  
K. S. Chan ◽  
M. P. Enright
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Fatigue Crack Growth ◽  
Crack Initiation ◽  
Crack Growth ◽  
Model Development ◽  
Fatigue Crack Initiation ◽  
Crack Size ◽  
Crack Initiation Life ◽  
Variability Model

This paper summarizes the development of a probabilistic micromechanical code for treating fatigue life variability resulting from material variations. Dubbed MICROFAVA (micromechanical fatigue variability), the code is based on a set of physics-based fatigue models that predict fatigue crack initiation life, fatigue crack growth life, fatigue limit, fatigue crack growth threshold, crack size at initiation, and fracture toughness. Using microstructure information as material input, the code is capable of predicting the average behavior and the confidence limits of the crack initiation and crack growth lives of structural alloys under LCF or HCF loading. This paper presents a summary of the development of the code and highlights applications of the model to predicting the effects of microstructure on the fatigue crack growth response and life variability of the α+β Ti-alloy Ti-6Al-4V.

scholarly journals Crack Initiation and Small Crack Growth Behavior of Age-Hardened Cu-6Ni-2Mn-2Sn-2Al Alloys

2004 ◽  
Vol 53 (2) ◽  
pp. 223-229 ◽  
Author(s):  
Masahiro GOTO ◽  
Seung-Zeon HAN ◽  
Chang-Joo KIM ◽  
Takaei YAMAMOTO ◽  
Norio KAWAGOISHI
Keyword(s):  
Crack Initiation ◽  
Crack Growth ◽  
Growth Behavior ◽  
Small Crack ◽  
Crack Growth Behavior ◽  
Small Crack Growth

Incorporation of Materials’ Sensitive Simulation Technique Into the PINTIN-CAM Code for Integrity of Nuclear Piping System

2010 ◽  
Author(s):  
Debashis Datta ◽  
Changheui Jang
Keyword(s):  
Crack Initiation ◽  
Stress Corrosion ◽  
Crack Growth ◽  
Development Process ◽  
Crack Coalescence ◽  
Individual Growth ◽  
Piping System ◽  
Outlet Nozzle ◽  
Failure Location ◽  
Combined Failure

Previously, the development process of a combined probabilistic fracture mechanics code for nuclear piping system was proposed based on some pre-assigned (by default) crack initiation and crack growth techniques e.g. assumption of preexisting cracks in case of no initiated cracks resulted from either fatigue or stress corrosion crack mechanisms and individual growth of those cracks by fatigue or stress corrosion cracking phenomenon without considering crack coalescence criteria. In one sense this type of approach might produce conservative results. To reduce the undue conservatism, in this version, materials’ sensitive crack initiation and subsequent crack growth of these simulated cracks along with crack coalescence criteria have been given prior importance. The logic behind this revised version of PINTIN-CAM PFM code has been presented and one previously published NUREG benchmark numerical problem has been reinvestigated by the improved features of this code. Based on design condition stress data, a typical PWR RPV outlet nozzle section shows the circumferential and axial through wall crack combined failure probability in the order of about 10−2 and 10−3 respectively. Among individual locations of a RPV ON section, the Inconel part shows relatively highest susceptible failure location followed by SS and LAS locations.

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