• Journal of Mechanical Science and Technology
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• v.17 no.6
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• pp.796-804
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• 2003

The use of fracture mechanics has traditionally concentrated on crack growth under an opening mechanism. However, many service failures occur from cracks subjected to mixed-mode loading. Hence, it is necessary to evaluate the fatigue behavior under mixed-mode loading. Under mixed-mode loading, not only the fatigue crack propagation rate is of importance, but also the crack propagation direction. In modified range 0.3$\leq$a/W$\leq$0.5, the stress intensity factors (SIFs) of mode I and mode II for the compact tension shear (CTS) specimen were calculated by using elastic finite element analysis. The propagation behavior of the fatigue cracks of cold rolled stainless steels (STS304) under mixed-mode conditions was evaluated by using K$\_$I/ and $_{4}$ (SIFs of mode I and mode II). The maximum tangential stress (MTS) criterion and stress intensity factor were applied to predict the crack propagation direction and the propagation behavior of fatigue cracks.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.119-124
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• 2003

In this study, retardation behavior of fatigue crack under single overloading of the mixed mode I+II state was experimentally investigated. To produce single overload in the mixed mode I+II state, the compact tension shear (CTS) specimen and loading device were used. The propagation tests for fatigue crack were performed under mode I loading overloading afterwards. We examined the observed deformation aspects, variation of fatigue life and crack propagation rate, and the aspects of retardation behavior from tests. The retardation effect of mixed-mode single overload on fatigue crack propagation behavior was smaller than that of mode I single overload. It has been confirmed that the retardation behavior did not immediately appear and the retardation length was short when the component of mixed-mode overload was changed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1508-1512
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• 2003

In this study, retardation behavior of fatigue crack under single overloading of the mixed mode state was experimentally investigated. To produce single overload in the mixed mode I+II state, the compact tension shear (CTS) specimen and loading device were used. The propagation tests for fatigue crack were performed under mode I and mixed-mode loading overloading afterwards. We examined the observed deformation aspects, the variation of fatigue life and crack propagation rate, and the aspects of retardation behavior from tests. The retardation effect of mixed-mode single overload on fatigue crack propagation behavior was smaller than that of mode I single overload. Also the loading modes of variable and constant amplitude loads have influence on the retardation behavior of fatigue cracks.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.7
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• pp.1217-1226
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• 2003

The purpose of this paper is to investigate fatigue crack behavior under shear(Mode II) loading. Various specimens and devices have been used in order to produce Mode II loading in fatigue experiments for shear crack propagation. But, there is not sufficient comparisons of experimental results between Mode II and others loading modes, because of characteristics of applied loads and specimens. So, compact tension shear(CTS) specimens were used in this paper to investigate the propagation behavior of Mode II by comparing the experimental results between loading modes. We firstly observed the characteristics which was showed in Mode II experiment using CTS specimens. The experimental results under Mode II loading were compared with fatigue crack behavior under Mode I and Mixed-mode I＋II loading. The characteristics for initiation and propagation behavior under Mode II loading was investigated by such comparisons.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.6
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• pp.109-116
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• 2004

In this study, when variable-amplitude load with various applying mode acts on the pre-crack tip, we examined how fatigue cracks behave. Hence aspects of the deformation caused by changing the applying mode of single overload and propagation behavior of fatigue crack were experimentally examined: What kinds of the deformation would be formed at pre-crack and its tip\ulcorner What aspects of the residual plastic deformation field would be formed in front of a crack\ulcorner How aspects of the plastic zone could be evaluated\ulcorner As applying mode of single overloading changes, the deformation caused by tensile and shear loading variously showed in each applying mode. The different aspects of deformation make influence on propagation behavior of cracks under constant-amplitude fatigue loading after overloading with various modes. We tried to examine the relationship between aspects of deformation and fatigue behavior by comparing the observed deformation at crack and crack propagation behavior obtained from fatigue tests.

• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.4
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• pp.129-137
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• 2002

In this study, mixed-mode fracture behavior is simulated effectively through the numerical method using the axial defomation link elements which can predict the behavior of quasi-brittle material. The behavior of quasi-brittle material is modeled numerically using the exponential tension softening constitutive equation and verified by comparing with the result of published experimental result. In order to verify the mixed-mode fracture behavior through the developed numerical method, analysis of mode I is formulated and the result is compared with those of FEM first, and then mixed-mode analysis is analyzed and compared with existing theories and experimental data. Also the characteristics of fracture behavior is examined through the analysis of crack generation with respect to various mode mixity.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.359-364
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• 2004

In this study, experiments were tried on the mixed-mode I+II single overloading model which changes the loading mode of overload and fatigue load. Aspects of deformation field in front of the crack which is formed by mixed-mode I+II single overloading were experimentally studied. Then the shape and size of mixed-mode plastic zone were approximately calculated. The propagation behavior of fatigue crack was examined under the test conditions combined by changing the loading mode. The behavior of fatigue cracks were greatly affected by shapes of plastic deformation field and applying mode of fatigue load. Accuracy of prediction and evaluation for fatigue life may be improved by considering all aspects of deformation and behavior of fatigue cracks.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.214-219
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• 2004

Crack tip behavior of single mode loading condition(mode I)depend on tensile loading component but one of mixed mode loading condition(mode I+II) have influenced on shear loading component like the practical structure. Because crack closure is caused by shear loading component under mixed-mode loading a research on the behavior in the stage of crack initiation and propagation require to be evaluate about crack closure effect by fatigue crack surface friction. For that reasion we examined the behavior at the crack tip by direct measuring method. Measured behavior at the crack tip was analyzed through vector crack tip displacement. As a result, crack propafation equation was corrected by considering with crack closure effect. In addition we compared fatigue fracture crack surface and crack closure level.

• Journal of Korean Society of Transportation
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• v.28 no.4
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• pp.119-128
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• 2010

Mode choice behavior is associated with travelers' latent behavior that is an unobservable preference to travel behavior or mode characteristics. This paper specifically addresses the problem of unobservable factors, that is latent behavior, in mode choice models. Consideration of latent behavior in mode choice models reduces the errors that come from unobservable factors. In this study, the authors defined the latent variables that mean a quantitative latent behavior factors, and developed the combined RP/SP model with latent variables using the mode choice behavior survey data. The data has traveler's revealed preference of existent modes along the Han River and stated preference of new water transit on the Han River. Also, The data has travelers' latent behavior. Latent variables were defined by factor analysis using the latent behaviour data. In conclusion, it is significant that the relationship between traveler's latent behavior and mode choice behavior. In addition, the goodness-of-fit of the mode choice models with latent variables are better than the model without latent variables.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.6 s.165
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• pp.1039-1047
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• 1999

It is necessary to evaluate the fatigue behavior of rail steel under the multi-axial stress state to assure the railway vehicle's safety. For this purpose, the stress analysis to investigate the crack initiation criteria, static failure and fatigue behavior under mixed-mode are performed. The stress analysis results show that the initiation of the transverse fissure depends on the maximum shear stress below the surface. For the mixed mode, the fatigue crack growth behavior which is represented by the projection crack length and comparative S.I.F, ${\Delta}K_v$, shows the more conservative results. Also, its rate is lower than that of the case of the mode I, and this difference decreases with increasing the stress ratio, R.