Stochastic Models Related to Fatigue Damage of Materials

1991 ◽  
Vol 113 (4) ◽  
pp. 215-221
Author(s):  
C. Ihara ◽  
T. Misawa
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Damage ◽  
Fatigue Crack Propagation ◽  
Stochastic Models ◽  
Fiber Composite ◽  
Carbon Fiber Composite ◽  
Sample Paths ◽  
Propagation Law ◽  
Theoretical Results

The stochastic models for the fatigue damage phenomena are proposed. They describe the uncertainty caused by inhomogeneity of materials for fatigue crack propagation of metals and fatigue damage of carbon fiber composite (CFRP). The models are given by the stochastic differential equations derived from the randomized Paris-Erdogan’s fatigue crack propagation law and Kachonov’s equation of fatigue damage. The sample paths and life distribution of fatigue crack propagation in metals or of damage accumulation in CFRP are obtained by using the solution of the stochastic differential equation and the probability density function, respectively. These theoretical results are compared with the actual experiments—fatigue crack propagation of high tensile strength steel APFH 60 and fatigue test for a carbon eight-harness-satin/epoxy laminate—through numerical experiments.

Modeling of Fatigue Crack Propagation

2004 ◽  
Vol 126 (1) ◽  
pp. 77-86 ◽  
Author(s):  
Yanyao Jiang ◽  
Miaolin Feng
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Damage ◽  
Fatigue Crack Propagation ◽  
Fatigue Crack Initiation ◽  
Cyclic Plasticity ◽  
R Ratio

Fatigue crack propagation was modeled by using the cyclic plasticity material properties and fatigue constants for crack initiation. The cyclic elastic-plastic stress-strain field near the crack tip was analyzed using the finite element method with the implementation of a robust cyclic plasticity theory. An incremental multiaxial fatigue criterion was employed to determine the fatigue damage. A straightforward method was developed to determine the fatigue crack growth rate. Crack propagation behavior of a material was obtained without any additional assumptions or fitting. Benchmark Mode I fatigue crack growth experiments were conducted using 1070 steel at room temperature. The approach developed was able to quantitatively capture all the important fatigue crack propagation behaviors including the overload and the R-ratio effects on crack propagation and threshold. The models provide a new perspective for the R-ratio effects. The results support the notion that the fatigue crack initiation and propagation behaviors are governed by the same fatigue damage mechanisms. Crack growth can be treated as a process of continuous crack nucleation.

Description of Small Fatigue Crack Propagation in ODS Steel

2014 ◽  
Vol 891-892 ◽  
pp. 911-916
Author(s):  
Pavel Hutař ◽  
Ivo Kuběna ◽  
Miroslav Šmíd ◽  
Martin Ševčík ◽  
Tomáš Kruml ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Fatigue Testing ◽  
Low Cycle Fatigue ◽  
High Stress ◽  
Oxide Dispersion Strengthened ◽  
Ods Steel ◽  
Small Fatigue Crack ◽  
Propagation Law

The oxide dispersion strengthened (ODS) steels are widely studied as possible candidate material for fission and fusion technology. Due to application of the ODS materials, mainly low cycle fatigue is important. Therefore, small crack initiation and propagation for rather high stress amplitude are in focus. The main aim of the presented work is description of the small fatigue crack propagation for ODS-EUROFER steel. Due to limited quantity of ODS steel special miniaturized cylindrical specimens for fatigue testing were designed. Crack propagation law based on plastic part of J-integral is presented and applied for mentioned material. The resulting fatigue crack propagation rates for ODS-EUROFER steel and EUROFER 97 are compared and discussed.

Effect of Constraint on Fatigue Crack Propagation in Notched Plates

2010 ◽  
Author(s):  
Xin Wang
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Crack Tip ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Fatigue Crack Propagation Rate ◽  
Rate Model ◽  
Propagation Law ◽  
Crack Tip Constraint

It has been observed that the loss of crack tip constraint leads to enhanced resistance to both cleavage and ductile tearing. Recent developments on constraint-based fracture mechanics have enabled the practical assessment of defective components including the constraint effect. In fatigue analyses, it is common practice to use the Paris crack propagation law, which is based on the stress intensity factor alone. Although in recent years several research attempts have been made to investigate the effect of constraint on fatigue, how to quantify the effect of crack tip constraint on the fatigue crack propagation rate is still an open issue. In this paper, the effect of crack tip constraint on the fatigue crack propagation of small cracks at notched plates is investigated. A fatigue crack propagation rate model developed earlier which incorporates both low and high constraint conditions is used. It is shown that the effect of constraint on crack propagation rate is significant when the crack is small (within the stress concentration of the notches). This effect can be accounted for by using the fatigue crack propagation rate model.

Fatigue Characterization of Long Dynamic Risers in Deep Waters

2007 ◽  
Author(s):  
Mohammad Iranpour ◽  
Farid Taheri ◽  
J. Kim Vandiver
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Damage ◽  
Fatigue Crack Propagation ◽  
Current Profile ◽  
Variable Amplitude ◽  
Deep Waters ◽  
Continuous Current ◽  
Mode Vibration ◽  
Basic Approaches

Continuous current action on risers develops vortices. These vortices cause risers to respond in a dynamic manner, leading to relatively large oscillations in the flexural and circumferential stresses. Vortex-induced vibration (VIV) and the resulting changes in the level of stresses in a riser could therefore cause detrimental fatigue induced problems, ranging from leakage to catastrophic failure of the riser. As a result, the VIV induced fatigue has always been a critical parameter in the design of risers, particularly when considering risers in deep waters. An experimental investigation into the fatigue crack propagation was conducted using a series of field data obtained on the high mode vibration of a relatively long flexible model riser. The field test data clearly illustrated the variable amplitude nature of the loading imposed on the riser by the current profile. There are currently several methods available for consideration of the crack growth rate due to overload and/or underloads; however, none has been developed based on data obtained for an actual riser. Indeed, fatigue experimental data on risers subject to VIV are relatively scarce in the literature. In this study the influence of the different harmonics resulting from VIV on the overall fatigue damage of the material is investigated. It is shown that the available basic approaches for assessing the fatigue crack propagation of components under variable amplitude loadings may significantly underestimate the VIV-induced fatigue damage of risers.

A Weight-Functions Based Approach to Predict Rolling Contact Fatigue Sub-Surface Crack Propagation in Gears

2003 ◽  
Author(s):  
Mario Guagliano ◽  
Andrea Piazza ◽  
Laura Vergani
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Weight Function ◽  
Fatigue Crack Propagation ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Rolling Contact ◽  
Weight Functions ◽  
Propagation Law ◽  
Propagation Prediction

The problem of the rolling contact fatigue crack propagation in gear teeth is dealt with. An approach based on the weight function method for the determination of KI and KII of internal cracks was developed. The effect of the contact and of the friction between the crack faces was taken into consideration by using approximate relations. The results were compared with the ones obtained by finite element analyses and the agreement was found satisfactory. By means of the determined weight function several analyses were performed and an interpolating function of KII versus the crack length were found. An approach for rolling contact fatigue crack propagation prediction based on the obtained solution and on a short crack propagation law was developed and implemented in a computational routine. The results are critically discussed.

Fatigue Crack Growth Examinations on Austenitic Stainless Steel in Corrosive Environment and at Elevated Temperature

2010 ◽  
Vol 659 ◽  
pp. 49-54
Author(s):  
János Lukács
Keyword(s):  
Stainless Steel ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Crack Propagation ◽  
Hold Time ◽  
Corrosive Environment ◽  
Time Period ◽  
Propagation Law

There are different documents and standards containing fatigue crack propagation limit or design curves and rules for the prediction of crack growth. The background of the curves and the calculations consist of two basic parts: statistical analysis of numerous experiments and a fatigue crack propagation law. The research work aimed to measure basic data for limit curves on austenitic stainless steel, in corrosive environment and at elevated temperatures, and to determine the design curves based on statistical analysis of measured data and a fatigue crack propagation law. Experiments were performed on modified CT specimens, in water solution and at two different temperatures. The fatigue crack growth tests were executed by constant load amplitude method. In order to study the hold time effect, fatigue crack growth tests were terminated and hold time period was applied. It can be concluded that the modified CT specimens are suitable for fatigue crack growth tests in corrosive environment; the fatigue crack propagation characteristics are different at different testing temperatures; and stable crack propagation and/or crack tip blunting can be detected during the hold time period at the used higher testing temperature.

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