• Proceedings of the KSME Conference
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• 2003.04a
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• pp.137-142
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• 2003

In this study, the propagation behavior of fatigue crack effected hole defects was investigated under mixed-mode I+II loading. To create mixed-mode stress field at crack tip, the compact tension shear (CTS) specimen and loading device were used in this tests. The propagation experiments of fatigue crack were performed by changing of the loading application angle(${\phi}$) and the distance(L) estimated from pre-crack tip to hole center located side by side by side with a pre-crack. As L changes, the variation for propagation aspect of fatigue crack, fatigue life and crack propagation rate were examined under mixed-mode loading. Under mixed-mode loading, the propagation rate of fatigue crack increased while the propagation direction changed dramatically because of the interference of hole defects.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.9
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• pp.131-139
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• 2001

The use of fracture mechanics has traditionally concentrated on crack growth under an opening mechanism. However, many service failure occur from cracks subjected to mixed mode loadings. Hence, it is necessary to evaluate the fatigue behavior under mixed mode loading. Under mixed mode loading conditions, not only the fatigue crack propagation rate is of importance, but also the crack propagation direction. The mode I and II stress intensity factors of CTS specimen were calculated using elastic finite element method. The propagation behavior of the fatigue crack of the STS304 steeds under mixed mode loading condition was evacuated by using stress intensity factors $K_I$ and $K_II. The MTS criterion and effective stress intensity factor were applied to predict the crack propagation direction and the fatigue crack propagation rate.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.11
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• pp.3498-3506
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• 1996

A loading device to be used in fracture experiment is presented. It's loading angle can be adjusted from $-45^{\circ}$ to $105^{\circ}$ at intervals of $15^{\circ}$ for a CTS ( compact tension-shear) specimen, so that it is to be useful to measure mixed mode toughness. The equations to give the $K_ I$, $K_ I1$ and J-integral for the experiment are evluated though finite elemetn analysis in which the loading procedure is simulated and the behaviors of the specimen such as load-displacement curve are estimated. In the course of the evaluation the values $K_ I$, $K_ I1$ and J-integral calculated through recentrly released numerical methods are employed as the reference ones.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.2A
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• pp.207-214
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• 2008

This study presents a way to validate the quality level of the proposed connection type and verify the experimental test, and performs a 3D nonlinear analysis corresponding to the experimental test. Two mixed-structure beams were cast and tested under a four-point static loading. Force-displacement relation, force-strain relation, force-opening width, and failure mode were observed from comparing the numerical results of the adopted FE model. Nonlinear analysis of mixed structures was carried out by utilizing the contact elements of a general purpose structural analysis computer program (ABAQUS). The results of numerical and experimental simulation show that the proposed L-shaped connection has greater stiffness under flexural loading and better structural performance with regard to the connection.

• Journal of Korean Society of Steel Construction
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• v.11 no.1 s.38
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• pp.33-42
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• 1999

In the present study, crack initiation criteria, static failure and tensile mode fatigue behavior for a rail steel are evaluated to assure the railway vehicle's safety. The transverse fissure, which is the most critical damage in the rail, is initiated by the maximum shear stress and its location is subsurface. In addition, the possibility of transition from the shear mode to the mixed mode increases with increasing the length of subsurface crack. Because of the brittleness by the welding, the fracture toughness of the welded part is lower than of the base metal. For low ${\Delta}K$, the stage II fatigue crack growth rates of the welded part is slower than of the base metal but, for high ${\Delta}K$, this different behavior for fatigue crack growth rate is nearly diminished. These trends are more remarkable for low stress ratio, R=0.1. It is believed that this behavior is caused by the change of the microstructure which that of the welded part is coarser than of base metal.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.286-291
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• 2001

Most cracks in the structure occur under mixed mode loadings and those propagation depend on the stress ratio very much. So, it is necessary to study the fatigue behavior under mixed mode loading as stress ratio changes. In this paper, fatigue crack propagation behavior was investigated respectively at stress ratio 0.1, 0.3, 0.5, 0.7 and we change loading application angle to $0^{\circ},\;30^{\circ},\;60^{\circ}$ to apply various loading. mode. The mode I and II stress intensity factors of CTS specimen used in this study were calculated by displacement extrapolation method using FEM(ABAQUS). Using both the study through the experiment and the theoretical study through FEM analysis, we studied the relation between crack propagation rate and stress intensity factor range at each loading mode due to the variation of stress ratio. Also, when the crack propagated under given stress condition and given loading mode condition, we studied what the dominant factors of the crack propagation rate were at each case.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.7
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• pp.4087-4092
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• 2014

The gangway connection of the articulated high speed railway vehicles (HSRV) is a double wrinkled rubber component to seal the air of the corridor under a range of angular deviations between the carriage end parts. From the results of non-linear structural analysis, one of the severe loading conditions for the connection is mixed mode (rolling+yawing) angular displacements while passing through the small-radius curved siding track of the HSRV depot. In this study, to ensure the safety enhancement of the component, the optimal design for the cross section of that was performed using the Solid Isotropic Material with Penalization (SIMP) method. Nonlinear finite element analysis confirmed that the decreases in the maximum principal strain of the optimized design under rolling and mixed modes are 68% and 39%, respectively, compared to the initial design.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.3A
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• pp.309-316
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• 2010

This paper proposed a nonlocal anisotropic damage model to simulate the behavior of plain and reinforced concrete structures that are predominantly tensile and compressive load. This model based on continuum damage mechanics, used a symmetric second-order tensor as the damage variable. For quasi-brittle materials, such as concrete, the damage patterns were different in tension and in compression. These two damage states were modeled by damage evolution laws ensuring a damage tensor rate proportional to the total strain tensor in terms of principal components. To investigate the effectiveness of proposed model, the double edge notched specimen experimented by nooru-mohamed and reinforced concrete bending beam were analyzed using the implementation of the proposed model. As the results for the simulation, the nonlocal anisotropic damage model with an adequate control of rupture correctly represented the crack propagation for mixed mode fracture. In the structural failure of reinforced concrete bending beam, the proposed model can be showed up to a very high damage level and yielding of the reinforcements.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.1
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• pp.78-84
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• 2015

The stress state acting on mechanical parts and structures is generally mixed stress. This complex stress state, which is subject to changes in the environment, will produce many. Cars running on roads with different road conditions will subject the automotive parts to combined stress state. In the x direction and the y direction, a different amplitude and frequency of the fatigue load can be present. However, the load amplitude for Mode I and Mode II in a 2-axis fatigue test is limited to a constant ratio; the load frequency is always the same for any mode. In this paper, it is verified how the variation of the load frequency for mode II affects the behavior of fatigue crack propagation under mixed mode.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.2
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• pp.146-151
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• 2001

The effects of slant interface in the hybrid specimen on the dynamic crack propagation behavior have been investigated using dynamic photoelasticity. The dynamic photoelasticity with the aid of Cranz-Shardin type high speed camera system is utilized to record the dynamic stress field around the dynamically propagating inclined interface crack tip in the three point bending specimens. The dynamic load is applied by a hammer dropped from 0.08m high without initial velocity. The dynamic crack propagation velocities and dynamic stresses field around the interface crack tips are investigated. Theoretical dynamic isochromatic fringe loops are compared with the experimental reults. It is interesting to note that the crack propagating velocity becomes comparable to the Rayleigh wave speed of the soft material of a specimen when slant angle decreases.