• Journal of the Korean Society for Precision Engineering
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• v.22 no.6 s.171
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• pp.152-158
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• 2005

The stress conditions acting on the practical structure are complex, and thus most cracks existing in the practical structures are under mixed-mode loading conditions. The effect of shear load component of mixed-mode loading acts more greatly in the stage of crack initiation and initial propagation than crack propagation stage. Hence, research on the behavior in the stage of crack initiation and initial propagation need to be examined in order to evaluate behavior of mixed-mode fatigue cracks. In this study, the crack tip displacement(CTD) was measured by using the direct measuring method(DMM). We examined the behavior at crack tip by determining crack opening load$(P_{op})$. From the test results, the propagation behavior of mixed-mode fatigue cracks was evaluated by considering mixed-mode crack closure. Also, we examined the characteristic of crack propagation under mixed-mode loading with crack propagation direction.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.481-484
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• 2000

Practical structures are subject not only to tension but also to shear and torsional loading. Even under uniaxial loading, when the load is not perpendicular to the crack plane, mixed mode crack can occur. Hence, it is necessary to evaluate the fatigue behavior under mixed mode loading. In this study, the propagation behavior of the fatigue crack of the STS304 steels under mixed mode loading condition was investigated. The mode I and II stress intensity factors of CTS specimen were calculated using elastic finite element method with experimental results. The fatigue crack propagation under mixed mode was evaluated by the effective stress intensity factor proposed by Tanaka.

• Journal of Korean Society of Transportation
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• v.11 no.2
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• pp.5-26
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• 1993

In order to analyze travel mode choice behavior, behavioral models including logit model, based on revealed preference theory, have been using easily measurable variables such as individual socioeconomic characteristics and physical attributes of travel modes. But some recent attitudinal models of travel choice behavior have implied that the negligence of individual psychological variables and individual choice constraints in travel mode choice might preclude better prediction of individual travel mode choice behavior. In this context, this study was attempted to reconstruct an attitudinal model(AM), especially focused on the decision rules in travel mode choice decision making process, consistent with the conceptual framework relating individual attitude and choice constraints to choice behavior. And to evaluate the strengths of the AM to other comparative models(logit, linear-additive, conjunctive, lexicographic model) in predicting travel mode choice bebavior, an empirical study of the mode choice in work-trip to CBD in Seoul was performed. According to the results the percent of correct prediction(PCP) derived from the AM was higher than those derived from comparative models by at least 7 to 20% in predicting travel mode choice. But each model produced a different prediction accuracy depending on market segmentation by travel modal users, individual socioeconomic characteristics, transportation system characteristics, and satisfaction levels. The finding that different groups divided by a certain criterion employ different decision rules supports the necessity of developing a choice model such as the AM combining compensatory and noncompensatory decision rules, and suggests that a proposed transportation system management plan or policy may have different effects on each group.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.11
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• pp.2287-2296
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• 2002

Most cracks in the structure occur under mixed mode loading and those fatigue crack propagation behavior heavily depends on the stress ratio. So, it is necessary to study the fatigue behavior under mixed mode loading as the stress ratio changes. In this paper, the fatigue crack propagation behavior was respectively investigated at stress ratio 0.1, 0.3, 0.5, 0.7 and we changed the loading application angle into 0$^{\circ}$, 30$^{\circ}$, 60$^{\circ}$ to apply various loading mode. The mode I and II stress intensity factor of CTS specimen used in this study was calculated by the displacement extrapolation method using FEM (ABAQUS). Using both the experiment and FEM analysis, we have concluded the relationship 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 ratio and loading mode condition, we have concluded the dominant factors of the crack propagation rate at each case.

• 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.

• Advances in concrete construction
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• v.7 no.1
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• pp.39-50
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• 2019

This study presents a comprehensive experimental investigation on mostly encountered types of Reinforced Concrete Haunched Beams (RCHBs) where three modes of RCHBs investigated; the diversity of studied beams makes it a pioneer in this topic. The experimental study consists of twenty RCHBs and four prismatic beams. Effects of important parameters including beam type, the inclination angle, flexure and compressive reinforcement, shear reinforcement on mechanical behavior and failure mode of each mode of RCHBs were examined in detail. Furthermore crack propagation at certain load levels were inspected and visualized for each RCHB mode. The results confirm that RCHBs have different behavior in shear as compared to the prismatic beams. At the same time, different mechanical behavior was observed between the modes of RCHBs. Therefore, RCHBs were classified into three modes according to the inclination shape and mode of failure (Modes A, B and C). However, it was observed that there is no significant difference between RCHBs and prismatic beams regarding flexural behavior. Moreover, a new and unified formula was proposed to predict the critical effective depth of all modes of RCHBs that is very useful to predict the critical section for failure.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.2
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• pp.276-282
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• 2012

This study looked for Mode status of each for fatigue crack growth behavior about the repeat load of mode I and the static load of mode II. The experiment was performed in the state of the repetition frequency of the sine wave 10Hz, the stress ratio 0.1, maximum load 300kg.f, a static load 0, 100, 200, 300kg.f, As the experimental results, in mode of static load, while the load value increases, the crack growth rate is slower as the energy of a crack mixing grows. Mode I and the power mode II get an influence each other in the direction of crack propagation path, but as they eventually get closer to the breaking point of the crack growth, it is dominated by the mode I.

• Smart Structures and Systems
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• v.32 no.1
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• pp.1-7
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• 2023

In modal analysis, the mode shape reflects the vibration characteristics of the structure, and thus it is widely performed for finite element model updating and structural health monitoring. Generally, the acceleration-based mode shape is suitable to express the characteristics of structures for the translational vibration; however, it is difficult to represent the rotational mode at boundary conditions. A tilt sensor and gyroscope capable of measuring rotational mode are used to analyze the overall behavior of the structure, but extracting its mode shape is the major challenge under the small vibration always. Herein, we conducted a feasibility study on a multi-mode shape estimating approach utilizing a single physical quantity signal. The basic concept of the proposed method is to receive multi-metric dynamic responses from two sensors and obtain mode shapes through bridge loading test with relatively large deformation. In addition, the linear transformation matrix for estimating two mode shapes is derived, and the mode shape based on the gyro sensor data is obtained by acceleration response using ambient vibration. Because the structure's behavior with respect to translational and rotational mode can be confirmed, the proposed method can obtain the total response of the structure considering boundary conditions. To verify the feasibility of the proposed method, we pre-measured dynamic data acquired from five accelerometers and five gyro sensors in a lab-scale test considering bridge structures, and obtained a linear transformation matrix for estimating the multi-mode shapes. In addition, the mode shapes for two physical quantities could be extracted by using only the acceleration data. Finally, the mode shapes estimated by the proposed method were compared with the mode shapes obtained from the two sensors. This study confirmed the applicability of the multi-mode shape estimation approach for accurate damage assessment using multi-dimensional mode shapes of bridge structures, and can be used to evaluate the behavior of structures under ambient vibration.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.2
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• pp.391-401
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• 1995

Several tests of the Double Cantilever Beam(DCB) were carried out for influence of the fiber orientation on the Mode I of the interlaminar fracture behavior in the Carbon/Epoxy composites. The interlaminar fracture toughness of Mode I was estimated based on the energy release rate of Mode I, $G_{I}$. The fracture toughness at crack initiation, $G_{IC}$, increases from type A to type E. The fracture toughness, $G_{IR}$ , is almost constant macroscopically for type A and type E when crack propagates. $G_{IR}$ for types B, C, D increases rapidly at the beginning of the crack growth then it decreases gradually. The fracture surface observation by SEM was also obtained the same results. Consequently the influence of the fiber orientation on the Mode I Interlaminar fracture behavior was made clear.ear.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.7
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• pp.899-906
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• 2011

Generally, load conditions of machine or structure in fatigue destruction is occurred not under single load conditions but under mixed load conditions. However, the experiment under mixing mode is insufficient because of no having test standard to the behavior of crack under mixing mode and variety of test methods, and many tests are required. In this paper measured crack direction path by created figure capture system when a experiment. Also, we studied by comparison the behavior of crack giving the change of stress ratio and inserting beach mark. Through the test under mixing mode, advancing path of crack is indicated that advancing inclined angle ${\Theta}$ (direction of specimen length) has increased depending on the increase of mixed mode impaction. It is indicated that according to the increase of mixed mode loading condition impaction under mixing mode, advancing speed of crack gets slow. Also, we found that inner crack(cross section of specimen) is progressed more rapidly than outer crack based on data through beach mark.