• Journal of the Korean Society of Mechanical Technology
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• v.13 no.2
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• pp.31-37
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• 2011

Sheet aluminum alloys have been used in manufacturing of machine structures. In fatigue crack propagation behavior of thin sheet aluminum alloys, it is important that fatigue crack growth rate is affected by crack closure phenomenon. In this work, we analyzed the characteristics of fatigue crack propagation behavior in experiment of constant stress condition for thin sheet Al 2024-T3 alloys, and identified the retardation behavior of crack growth by comparing experimental results of thin and thick plate specimen. We attempt to operate the fatigue life estimating process using the fatigue related material constants from referred fatigue crack propagation analysis. And we analyzed the experimental and prediction results of fatigue life of thin sheet aluminum alloy in order to identify the relation between retardation behavior of fatigue crack growth and crack closure phenomenon.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.5 s.176
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• pp.1281-1287
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• 2000

The studies of probability distribution of the fatigue crack growth life have been somewhat reported. But the study on the probability distribution of the fatigue crack growth life considering the crack coalescence for three dimensional surface fatigue crack has apparently not been reported to date. In this study, the computer program has been developed to predict the probability distribution of the fatigue crack growth life considering the crack coalescence. The effects of parameters for the distribution of the fatigue crack propagation life were evaluated by using the program.

• Journal of Korean Society of Steel Construction
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• v.11 no.4 s.41
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• pp.409-416
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• 1999

The fatigue crack growth analysis based on the fracture mechanics is useful to the estimation of the fatigue life on welded structures under cyclic loading. The analysis procedure in fatigue crack growth under uniform axial loading is applicable to bending fatigue problem as well. The intent of the present study is to show the procedure for calculating the fatigue crack propagation lifetimes of deckplates under bending stress and to explain the crack growth rates for the two dimensional crack problems. It is shown that the fatigue crack grows at a decreasing rate and the fatigue life depends on the initial crack length and the crack shape. The numerically predicted crack growth agree with the experimental data.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.5
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• pp.1552-1561
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• 1996

It requires uch time and cost to obtain the fatigue crack growth life and fatigue crack growth path morphlogy from the fatigue crack growth tests. In this study, the Monte-Carlo simulation program was developed to predict the fatigue crack growth lofe and fatigue crack growth path morphology of metal matrix composites. Fatigue crack growth lives of 5%, 10%, 15%, 20%, 25% and 30% $SiC_w$/Al composites were predicted by usign the Monte-Carlo Simulation. And the fatigue crack growth lives of 25% $SiC_w$/Al and Almatrix from Monte-carlo simulation were compared with fatigue life from experiments in order to verify the accuracy of Monte-Carlo Simulation program.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.12
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• pp.2091-2099
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• 2001

Fatigue crack growth behavior of inclined cracked Al 6061-T6 thick aluminum plate(6mm) repaired with the bonded composite patch was studied. A 0°inclined crack bonded reinforced composite patch and 15°, 30°, 45°, 60°inclined crack plates were tested. The effect of patch and inclined angle were studied and compared to each other. Also we investigated to the crack propagation direction and debonding behavior during the fatigue crack growth test. In this paper. a study was con(ducted to get an fatigue life, fatigue crack growth ratio and crack growth direction. Finally, the effectiveness of composite patch on inclined cracked plate was investigated. The results demonstrated thats there was a definite variation in fatigue life and fatigue crack growth behavior depending on the inclined crack angle.

• Journal of the Society of Naval Architects of Korea
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• v.40 no.3
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• pp.45-53
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• 2003

Ships and ocean structures are subjected to random loads caused by irregular waves. The irregularity of amplitude from random loading affects on fatigue crack growth and fatigue life. However the effects of irregularity of loading on fatigue including random loading have not been explained exactly. Therefore in this paper crack growth tests on DENT specimens under constant-amplitude loading including a single tensile overload are conducted to investigate the effect of overload on crack growth rate. The size of plastic zone and crack growth rate before and after a single tensile overloading are measured using ESPI system. Crack growth retardation model that is characterized by crack growth length and the size of plastic zone was proposed and compared with test result. From the research, the validity of proposed model is examined on crack growth retardation, and consequently fatigue life.

• Journal of Welding and Joining
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• v.35 no.1
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• pp.61-67
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• 2017

Recent studies on the fatigue assessment of high strength steel weld based on the fracture mechanics have frequently raised the problems related to the conservatism in the fatigue crack growth rate specified in the relevant design code. The purpose of this study is to evaluate the effect of the fatigue crack growth parameter on the fatigue life for the low carbon steel weld. In order to do it, the fatigue tests with the constant stress ratio were performed to evaluate the fatigue crack growth rate in the butt weld of SM490. And the fatigue crack growth parameters of the weld were evaluated in accordance with ASTM E647. From the comparative fatigue assessment results, it was found that the fatigue crack growth rate specified in the relevant design code was too conservative to estimate the residual fatigue life of welded structure. So, in order to get the more reliable results, it was recommended that the fatigue life estimation based on the fracture mechanics be performed with the fatigue crack growth parameter specified by test.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.10a
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• pp.232-237
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• 2001

The evaluation of specimen thickness effect of fatigue crack growth life by the simulation of probabilistic fatigue crack growth is presented. In this paper, the material resistance to fatigue crack growth is treated as a spatial stochastic process, which varies randomly on the crack surface. Using the previous experimental data, the non-Gaussian(eventually Weibull, in this report) random fields simulation method is applied. This method is useful to estimate the probability distribution of fatigue crack growth life and the variability due to specimen thickness by simulating material resistance to fatigue crack growth along a crack path.

• International Journal of Precision Engineering and Manufacturing
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• v.1 no.2
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• pp.43-47
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• 2000

When estimating fatigue crack growth (FCG) life of structures, the use of crack growth models and knowledge of the values of their corresponding parameters are of vital importance. Inconsistency in using models with appropriate parameters can lead to enormous errors in FCG life prediction. In this paper examples are analyzed and compared with test results to show the possible problems, Consistency checks are necessary for avoiding some pitfalls, and also necessary for verifying the correct performance and accuracy of the used computer program.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.10a
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• pp.73-78
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• 2002

Ships and ocean structures are generally under random loading. Various type of variable-amplitude loading affects fatigue crack growth and fatigue life. However interaction effects due to irregularity of loading including random loading have not explained exactly and it is difficult to examined fatigue crack growth behaviour and fatigue life for this reason. Therefore in this paper crack growth tests with constant-amplitude loading including a single overload were conducted to measure plastic zone size near crack tip of DENT specimen. And the observed plastic zone sized were discussed in terms of crack growth rate. As a result of this the effect the plastic rue size due to the overload is examined on the effect on crack growth rate and, consequently, fatigue life.