Crack Growth Model under Creep-Fatigue Interaction

2011 ◽  
Vol 243-249 ◽  
pp. 241-244 ◽  
Author(s):  
Rui Zhang ◽  
Hong Liang Li
Keyword(s):  
Growth Rate ◽  
Crack Growth Rate ◽  
Crack Growth ◽  
Growth Model ◽  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Zone Model ◽  
J Integral ◽  
Creep Fatigue ◽  
Crack Growth Model

In the present paper, a new creep-fatigue crack growth model of J-integral criterion is proposed. The model is built based on the dislocation-free zone (DFZ) theory and cohesive zone model. The process of crack growth is viewed as the intermittent quasi-cleavage fracture of the DFZ. The microscopic void caused by creep will grow and join the dominant crack under creep-fatigue interaction. In this process, material’s plastic deformation induces the change of the dislocation’s density. The redistribution of dislocation will change the value of J-integral within the cohesive zone. When the value of J-integral attains the critical value Jc, crack will grow by the original width of DFZ. Based on it, a simple relation is employed to evaluate crack growth rate under creep-fatigue interaction. The calculated crack growth rate curve exhibits three different regimes, which is in agreement with the general crack propagation pattern under creep-fatigue interaction. The model gives a reasonable explanation for crack growth under creep-fatigue interaction. The calculated value is close to the value obtained by experiment.

Nickel Alloy Crack Growth Correlations in BWR Environment and Application to Core Support Structure Welds Evaluation

2008 ◽  
Author(s):  
Raj Pathania ◽  
Robert G. Carter
Keyword(s):  
Growth Rate ◽  
Stress Intensity ◽  
Crack Growth Rate ◽  
Crack Growth ◽  
Growth Model ◽  
Thickness Direction ◽  
Support Structure ◽  
Nickel Base ◽  
Crack Growth Model ◽  
Crack Growth Rates

An intergranular stress corrosion cracking (IGSCC) growth model for unirradiated nickel-base alloys (Alloys 82, 182 and 600) in boiling water reactor (BWR) environments has been developed by EPRI. This model has been used for assessment of the crack growth rates in BWR nickel base austenitic alloys with particular application to the BWR shroud support structure materials and welds, including attachments to the reactor pressure vessel fabricated from these alloys. However, the crack growth model can be used for other components with like materials in BWR environments provided that specific parameters such as stresses and stress intensity factor (KI) distributions are determined. The methodology involves development of crack growth disposition curves that can account for the variability of important IGSCC parameters to provide a conservative, yet realistic assessment of crack growth rate in BWR environments. An extensive nickel base alloy crack growth rate database was developed from data generated through the peer review process and includes both experimental data points and in-plant crack arrest verification system data. Most of the data in the database have reasonable definition of environmental conditions and other important crack growth parameters thus permitting a more realistic generic crack growth model to be developed. Although most of the data is for Alloy 182, it bounds the crack growth rate of Alloy 82 and Alloy 600. The database was used to derive crack growth disposition curves under normal water chemistry (NWC) and hydrogen water chemistry (HWC) conditions. The disposition curves have two stress intensity regimes; one for KI < 25 ksi√in where the crack growth is KI-dependent and one for KI > 25 ksi√in where the crack growth is KI-independent. The crack growth disposition curves were used together with a crack growth estimation methodology to determine the crack propagation of the BWR shroud support structure welds which are fabricated from Alloy 82/182. The steps involved in the development of the methodology include determination of residual stresses and operating stresses, development of stress intensity factor (KI) solutions for crack propagation in the through-thickness direction and estimation of crack growth rates. This methodology was applied specifically for crack growth in the through-thickness direction. Application of this crack growth model to BWR shroud support structure welds H8 and H9 indicates that there is an adequate time period between inspections before initial cracks of ≤10% through-wall thickness reaches the allowable flaw sizes, particularly for HWC conditions.

Predicting the Crack Growth Behavior in a Filled Elastomer

2006 ◽  
Vol 3-4 ◽  
pp. 273-278
Author(s):  
C.T. Liu ◽  
M. Yen ◽  
H.K. Ching
Keyword(s):  
Growth Rate ◽  
Crack Growth Rate ◽  
Crack Length ◽  
Crack Growth ◽  
Growth Model ◽  
Initial Crack ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Initial Crack Length ◽  
Crack Growth Model

In this study, single-edge cracked uniaxial specimens with an initial crack length of 0.1 in. or 0.3 in. and wedge-shaped sheet specimens with an initial crack length of 0.3 in were tested at a constant displacement rate of 50 in/min under 1000 psi confining pressure. The specimens were made of a highly filled polymeric material, containing 86% by weight of hard particles embedded in a rubbery matrix, which was made of polybutadiene-acrylic acid-acrylonitrile rubber. The uniaxial crack growth data were used to develop a crack growth model, relating crack growth rate da/dt and Mode I stress intensity factor KI. The developed crack growth model was used to predict the crack growth behavior in the wedge-shaped specimen. The results of the analysis indicated that the predicted crack growth rate compared well with the experiment

Numerical Simulation of Dynamic Ductile Fracture Propagation Using Cohesive Zone Modeling

2008 ◽  
Author(s):  
Do-Jun Shim ◽  
Gery Wilkowski ◽  
David Rudland ◽  
Brian Rothwell ◽  
James Merritt
Keyword(s):  
Finite Element ◽  
Crack Propagation ◽  
Crack Growth ◽  
Growth Model ◽  
Cohesive Zone ◽  
Zone Model ◽  
Pipe Material ◽  
Ductile Crack ◽  
Ductile Crack Growth ◽  
Crack Growth Model

This paper presents the development of a dynamic ductile crack growth model to simulate an axially running crack in a pipe by finite element analyses. The model was developed using the finite element (FE) program ABAQUS/Explicit. To simulate the ductile crack propagation, a cohesive zone model was employed. Moreover, the interaction between the gas decompression and the structural deformation was simulated by using an approximate three-dimensional pressure decay relationship from experimental results. The dynamic ductile crack growth model was employed to simulate 152.4 mm (6-inch) diameter pipe tests, where the measured fracture speed was used to calibrate the cohesive model parameters. From the simulation, the CTOA values were calculated during the dynamic ductile crack propagation. In order to validate the calculated CTOA value, drop-weight tear test (DWTT) experiments were conducted for the pipe material, where the CTOA was measured with high-speed video during the impact test. The calculated and measured CTOA values showed reasonable agreement. Finally, the developed model was employed to investigate the effect of pipe diameter on fracture speed for small-diameter pipes.

Estimation of Crack Growth Rate by J-Integral Range for Type SUS304 Stainless Steel Plate in Creep-Fatigue Tests at High Temperature

2014 ◽  
Author(s):  
Madoka Funai ◽  
Osamu Watanabe ◽  
Akihiro Matsuda
Keyword(s):  
Growth Rate ◽  
Crack Growth Rate ◽  
Crack Growth ◽  
Growth Rates ◽  
Fatigue Loading ◽  
Fatigue Tests ◽  
J Integral ◽  
Creep Fatigue ◽  
Integral Range ◽  
Crack Growth Rates

In structures having stress concentration under cyclic loading, a small crack initiates and it grows and propagates. Evaluating crack growth is important to estimate the remaining life of cracked components. The present paper shows the estimation of crack growth rate under creep-fatigue loading with some patterns of strain holding times. Creep-fatigue tests of the perforated plate having initial crack were conducted with the different strain holding time under strain-controlled loading at 550°C. The crack growth was observed from the photographs taken at each cycle. The crack growth per one cycle of creep-fatigue loading was evaluated by the creep-fatigue crack propagation law which used increment J-integral range. Comparing the crack growth rates of experimental with those of predicted, the crack growth rates were predicted by using increment J-integral range with the accuracy was factor of 2.

A CRACK GROWTH MODEL BASED ON FATIGUE DAMAGE ACCUMULATION

2010 ◽  
Vol 24 (15n16) ◽  
pp. 2774-2779 ◽  
Author(s):  
BAOXIANG QIU ◽  
XIAOGUI WANG ◽  
ZENGLIANG GAO
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Damage ◽  
Growth Model ◽  
Damage Accumulation ◽  
Fatigue Damage Accumulation ◽  
Crack Growth Model

A novel model for predicting the fatigue crack growth had been developed based on the concept of the fatigue damage accumulation. Fatigue crack growth was considered as a process of continuous crack nucleation. The crack tip failed to form a fresh crack while the accumulative fatigue damage reached the critical damage. A simplified model of the general crack growth model was proposed with the assumption that the damage zone can be divided into many different zones and each zone had the same crack growth rate. The model was applied to predict the crack growth of the compact specimen made of 16MnR steel under the constant amplitude loading. The predicted crack growth rate was in excellent agreement with the experimental observations.

Fracture and Fatigue Resistance of Ultrafine Grain CuCrZr Alloy Produced ECAP

2006 ◽  
Vol 503-504 ◽  
pp. 811-816 ◽  
Author(s):  
Alexei Vinogradov ◽  
Kazuo Kitagawa ◽  
V.I. Kopylov
Keyword(s):  
Growth Rate ◽  
Crack Growth Rate ◽  
Crack Growth ◽  
Stable Crack Growth ◽  
Ultrafine Grain ◽  
J Integral ◽  
Present Communication ◽  
Angular Pressing ◽  
Fatigue And Fracture ◽  
Anisotropy Of Mechanical Properties

Anisotropy of mechanical properties, fatigue and fracture resistance of precipitation hardened CuCrZr alloy ultrafine (UFG) grained by equal-channel angular pressing (ECAP) is in focus of the present communication. Fracture toughness was estimated in terms of J-integral and the fatigue crack growth rate was quantified. It was found that although the estimated JIC-value appeared lower than that reported in the literature for a reference alloy, the ductility, fracture and crack growth resistance remained satisfactory after ECAP while the tensile strength and fatigue limit improved considerably. The stable crack growth rate did not differ very much for ECAP and reference conventional CuCrZr and no remarkable anisotropy in the stable crack growth was noticed.

Investigation of Fracture Criterion for HTPB Propellant

2012 ◽  
Vol 591-593 ◽  
pp. 745-749
Author(s):  
Bo Han ◽  
Yu Tao Ju ◽  
Chang Sheng Zhou
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Cohesive Zone ◽  
Fracture Criterion ◽  
Cohesive Zone Model ◽  
Rate Effect ◽  
Zone Model ◽  
J Integral ◽  
Loading Rates ◽  
Htpb Propellant

The fracture toughness of HTPB propellant has a significant rate effect. In order to establish a fracture criterion considering rate effect for HTPB propellant, experiments were conducted at different loading rates. Two kinds of specimens were used to get the fracture properties. Stress intensity factor and J-integral were obtained by the single edge notched tension specimen test. A power law cohesive zone model was obtained by the experiment based inverse method. Through comparing we found that the stress intensity factor and J-integral cannot model the rate effect in fracture process. The cohesive zone model (CZM) has a constant critical separation distance at different loading rates and has a capability to model the rate effect during the crack initiation and propagation process. A finite element simulation in ABAQUS was given to demonstrate its capability to model the crack propagation.

Effect of Constraint Induced by Specimen Geometries on Crack Growth Behavior Under Creep-Fatigue Interaction

2018 ◽  
Author(s):  
Lei Zhao ◽  
Lianyong Xu
Keyword(s):  
Growth Rate ◽  
Crack Growth Rate ◽  
Crack Growth ◽  
Growth Rates ◽  
Crack Tip ◽  
Crack Growth Behavior ◽  
Growth Behaviour ◽  
Crack Growth Behaviour ◽  
Creep Fatigue ◽  
Crack Growth Rates

Creep-fatigue interaction would accelerate the crack growth behaviour and change the crack growth mode, which is different from that presenting in pure creep or fatigue regimes. In addition, the constraint ahead of crack tip affects the relationship between crack growth rate and fracture mechanics and thus affects the accuracy of the life prediction for high-temperature components containing defects. In this study, to reveal the role of constraint caused by various specimen geometries in the creep-fatigue regime, five different types of cracked specimens (including C-ring in tension CST, compact tension CT, single notch tension SENT, single notch bend SENB, middle tension MT) were employed. The crack growth and damage evolution behaviours were simulated using finite element method based on a non-linear creep-fatigue interaction damage model considering creep damage, fatigue damage and interaction damage. The expression of (Ct)avg for different specimen geometries were given. Then, the variation of crack growth behaviour with various specimen geometries under creep-fatigue conditions were analysed. CT and CST showed the highest crack growth rates, which were ten times as the lowest crack growth rates in MT. This revealed that distinctions in specimen geometry influenced the in-plane constraint level ahead of crack tip. Furthermore, a load-independent constraint parameter Q* was introduced to correlate the crack growth rate. The sequence of crack growth rate at a given value of (Ct)avg was same to the reduction of Q*, which shown a linear relation in log-log curve.

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