Multiple Fatigue Crack Growth Prediction Using Stress Intensity Factor Solutions Modified by Empirical Interaction Factors

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Shinji Konosu ◽  
Kyosuke Kasahara
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Intensity Factor ◽  
Crack Growth ◽  
The Body ◽  
Multiple Cracks ◽  
Growth Prediction ◽  
Interaction Factors

It is generally believed that multiple fatigue crack growth prediction is difficult with the use of conventional stress intensity factor (SIF) solution calculations because of issues such as SIF magnification and shielding effects. Therefore, almost all the existing Fitness for Service (FFS) rules such as the ASME Code Section XI and JSME Code adopt the procedure whereby multiple cracks grow independently after applying a certain alignment rule based on the initial crack configuration and are combined immediately into an enveloping crack when the crack tips touch. In some cases, the results of the procedures in the existing FFS rules are less accurate in predictions of the service life of cracked components. Therefore, there is still room for improvement, although the procedures are simple for utilities. This paper describes a new approach to predict fatigue crack growth life of multiple nonaligned cracks by the use of SIF solutions modified by empirical interaction factors. Several examples of two nonaligned cracks illustrate the accuracy and effectiveness of the procedure by comparison with numerical analysis by the body force method for two-dimensional problems and with the experimental results given in the literature for three-dimensional problems.

Multiple Fatigue Crack Growth Prediction Using Standard Stress Intensity Factor Solutions

2010 ◽  
Author(s):  
Shinji Konosu ◽  
Kyosuke Kasahara
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Intensity Factor ◽  
Crack Growth ◽  
The Body ◽  
Multiple Cracks ◽  
Growth Prediction ◽  
Dimensional Models

It is generally believed that multiple fatigue crack growth prediction is difficult with the use of standard stress intensity factor (SIF) solution calculations because of the complicated nature of such issues as magnification and shielding effects. Therefore, almost all the existing FFS rules such as the ASME Section XI Code and JSME Code adopt the procedure whereby multiple cracks grow independently after applying a certain alignment rule based on the initial crack configuration and are combined immediately into an enveloping crack when the crack tips touch. In some cases, the results of the procedures in the existing FFS rules can be unrealistic and may lead to unreliable predictions of the service life of cracked components. This paper describes a new approach to predicting multiple nonaligned fatigue crack growth life by the use of standard SIF solutions. Several examples, as compared with numerical analysis by the body force method for two-dimensional models and experimental results in the literature for three-dimensional models, illustrate the accuracy and effectiveness of the procedure.

Effect of Temperature on Fatigue Crack Growth in CPVC

2003 ◽  
Vol 125 (1) ◽  
pp. 71-77 ◽  
Author(s):  
Muhammad Irfan-ul-Haq ◽  
Nesar Merah
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Intensity Factor ◽  
Crack Growth ◽  
Effect Of Temperature ◽  
Stress Intensity Factor Range ◽  
Crack Growth Behavior ◽  
Different Temperatures

This study addresses the effect of temperature on fatigue crack growth (FCG) behavior of CPVC. FCG tests were conducted on CPVC SEN tensile specimens in the temperature range −10 to 70°C. These specimens were prepared from 4-in. injection-molded pipe fittings. Crack growth behavior was studied using LEFM concepts. The stress intensity factor was modified to include the crack closure and plastic zone effects. The effective stress intensity factor range ΔKeff gave satisfactory correlation of crack growth rate (da/dN) at all temperatures of interest. The crack growth resistance was found to decrease with temperature increase. The effect of temperature on da/dN was investigated by considering the variation of mechanical properties with temperature. Master curves were developed by normalizing ΔKeff by fracture strain and yield stress. All the da/dN-ΔK curves at different temperatures were collapsed on a single curve. Crazing was found to be the dominant fatigue mechanism, especially at high temperature, while shear yielding was the dominant mechanism at low temperatures.

Mechanisms of Fatigue Crack Growth in WC-Co Cemented Carbides

2005 ◽  
Vol 297-300 ◽  
pp. 1120-1125 ◽  
Author(s):  
Myung Hwan Boo ◽  
Chi Yong Park
Keyword(s):  
Growth Rate ◽  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Intensity Factor ◽  
Crack Growth ◽  
Stress Ratio ◽  
Cemented Carbides ◽  
Stress Intensity Factor Range

In order to study the influence of stress ratio and WC grain size, the characteristics of fatigue crack growth were investigated in WC-Co cemented carbides with two different grain sizes of 3 and 6 µm. Fatigue crack growth tests were carried out over a wide range of fatigue crack growth rates covering the threshold stress intensity factor range DKth. It was found that crack growth rate da/dN against stress intensity factor range DK depended on stress ratio R. The crack growth rate plotted in terms of effective stress intensity factor range DKeff still exhibited the effect of microstructure. Fractographic examination revealed brittle fracture at R=0.1 and ductile fracture at R=0.5 in Co binder phase. The amount of Co phase transformation for stress ratio was closely related to fatigue crack growth characteristics.

Fatigue Damage Analysis on Crack Growth and Fatigue Life of Welded Bridge Members with Initial Crack

2006 ◽  
Vol 324-325 ◽  
pp. 251-254 ◽  
Author(s):  
Tai Quan Zhou ◽  
Tommy Hung Tin Chan ◽  
Yuan Hua
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Fatigue Life ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Intensity Factor ◽  
Crack Growth ◽  
Fatigue Damage ◽  
Initial Crack ◽  
Traffic Loading

The behavior of crack growth with a view to fatigue damage accumulation on the tip of cracks is discussed. Fatigue life of welded components with initial crack in bridges under traffic loading is investigated. The study is presented in two parts. Firstly, a new model of fatigue crack growth for welded bridge member under traffic loading is presented. And the calculate method of the stress intensity factor necessary for evaluation of the fatigue life of welded bridge members with cracks is discussed. Based on the concept of continuum damage accumulated on the tip of fatigue cracks, the fatigue damage law suitable for steel bridge member under traffic loading is modified to consider the crack growth. The proposed fatigue crack growth can describe the relationship between the cracking count rate and the effective stress intensity factor. The proposed fatigue crack growth model is then applied to calculate the crack growth and the fatigue life of two types of welded components with fatigue experimental results. The stress intensity factors are modified by the factor of geometric shape for the welded components in order to reflect the influence of the welding type and geometry on the stress intensity factor. The calculated and measured fatigue lives are generally in good agreement, at some of the initial conditions of cracking, for a welded component widely used in steel bridges.

Hydrogen Assisted Fatigue Crack Growth in a Precipitation-Hardened Martensitic Stainless Steel Under Gaseous Hydrogen

2014 ◽  
Author(s):  
Giovambattista Bilotta ◽  
Mandana Arzaghi ◽  
Gilbert Hénaff ◽  
Guillaume Benoit ◽  
Clara Moriconi ◽  
...  
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Intensity Factor ◽  
Crack Growth ◽  
Martensitic Stainless Steel ◽  
Gaseous Hydrogen ◽  
Crack Growth Behavior ◽  
Loading Frequency

In this study, the effect of gaseous hydrogen on the fatigue crack growth behavior in a precipitation-hardened martensitic stainless steel is investigated. It is known that the degradation in fatigue crack growth behavior derives from a complex interaction between the fatigue damage and the amount of hydrogen enriching the crack tip, which is dependent on the hydrogen pressure, loading frequency, and stress intensity factor amplitude. Therefore, fatigue crack growth tests were performed in a range of 0.09 to 40 MPa under gaseous hydrogen at a frequency of 20 and 0.2 Hz. The fatigue data as well as fracture morphologies obtained so far indicate a sharp increase in crack growth rates in a narrow range of stress intensity factor amplitudes. Also, it is shown that by decreasing the loading frequency to 0.2 Hz at a given pressure of hydrogen the transition occurs at lower values of stress intensity factor amplitudes accompanied by a change in fracture mode. Scanning electron microscope (SEM) observations of the fracture surfaces are used to support the explanations proposed to account for the observed phenomena.

An Efficient Way to Characterize the Fatigue Crack Growth Based on Numerical Analysis

2009 ◽  
Vol 417-418 ◽  
pp. 653-656
Author(s):  
Ya Zhi Li ◽  
Jing He ◽  
Zi Peng Zhang
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Intensity Factor ◽  
Crack Length ◽  
Crack Growth ◽  
Crack Closure ◽  
Load Ratio ◽  
Specimen Thickness

The behavior of plasticity induced fatigue crack closure (PICC) in middle tension specimen was analyzed by the elastic-plastic finite element method. For the constant-K (CK) loading cases, the opening stress intensity factor are independent of crack length. The level of increases with the maximal applied stress intensity factor for given load ratio and increases with for fixed . The in plane strain state is much smaller than that in plane stress state. The results under CK loadings can be deduced to constant amplitude cyclic loading case during which the load ratio, maximal load level, crack length and specimen thickness are all the factors affecting the crack closure effect. The phenomena revealed in the analysis are beneficial in understanding the driving force mechanism of the fatigue crack growth.

A Superposition Approach for Time-Dependent Fatigue Crack Growth

2012 ◽  
Author(s):  
Fashang Ma
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Intensity Factor ◽  
Crack Growth ◽  
Growth Rates ◽  
Time Dependent ◽  
Crack Growth Rates ◽  
Time Dependent Crack Growth

High temperature fatigue crack growth is a combination of fatigue, creep and environmental attack, which greatly enhance fatigue crack growth. In order to understand the damage mechanisms and develop a physically based crack growth model, systematic experimental research has been conducted under various loading conditions for different specimen geometries made from a high strength nickel alloy. Test results from this work showed that time-dependent fatigue crack growth rates differ significantly from those observed in conventional fatigue crack growth tests. Crack geometry and loading history significantly affect fatigue crack growth rate. These results suggest the need for a change in the K based superposition approach for time-dependent crack growth modeling. A phenomenological model has been developed to predict time-dependent crack growth under various loading histories and crack geometries. In this model an effective stress intensity factor is defined to account for the effects of constraint loss of fracture mechanics due to crack-tip plasticity, and the creep stress relaxation on stress intensity factor. It is found the model can accurately predict the dwell crack growth rates for different crack geometries under various loading conditions.

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