• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.295-302
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• 2000

Earthquakes not only produce additional load on the structures and underlying soil, but also change the strength characteristics of the soil. Therefore, in order to analyze soil structures for stability, the behaviour after earthquake must be considered. In this paper, a series of cyclic triaxial tests and monotonic triaxial tests were carried out to investigate the undrained shear strength and liquefaction strength characteristics of Nak-Dong River sand soils which were subjected to cyclic loading. The sample was consolidated in the first stage and then subjected to stress controlled cyclic loading with 0.1Hz. After the cyclic loading, the cyclic-induced excess pore water pressure was dissipated by opening the drainage valve and the sample was reconsolidated to the initial effective mean principal stress(p/sub c/'). After reconsolidation, the monotonic loading or cyclic loading were applied to the specimen. In the results, the undrained shear strength and liquefaction strength characteristics depended on the pore pressure ratio(Ur=U/p/sub c/'). The volume change following reconsolidation can be a function of cyclic-induced excess pore water pressure and the maximum double amplitude of axial strain.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.17 no.4
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• pp.160-164
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• 2007

Carbon nanofibers were deposited on silicon oxide substrate by thermal chemical vapor deposition method. For the enhancement of the characteristics of carbon nanofibers, the source gases ($C_2H_2,\;H_2$) flows were intentionally manipulated as the cyclic on/off modulation of $C_2H_2$ flow. By the cyclic modulation process during the initial deposition stage, the formation density of carbon nanofibers on the substrate could be much more enhanced. The diameter of as-grown carbon nanofibers was also reduced by the cyclic modulation process. The cause for the variation in the characteristics of carbon nanofibers by the cyclic modulation process was discussed in association with the hydrogen gas etching ability.

• Journal of the korean Society of Automotive Engineers
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• v.9 no.1
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• pp.69-76
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• 1987

This paper deals with the theoretical prediction and cyclic variation of combustion characteristics in a four stroke, single0cylinder, diesel engine. Theoretical calculations employed a simple empirical model of analysis of energy equation for the thermodynamic system of engine cylinder. The cyclic variation of combustion characteristics is investigated, in term of frequency distribution and standard deviation of peak characteristics, as obtained by combustion analyzer system. The results of theoretical prediction are shown to be in close agreement with the experimental data. The effect of fuel injection timing, engine speed, cooling water temperature, and the compression ratio on the cyclic variations of combustion characteristics were discussed.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.16 no.1
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• pp.1-10
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• 2020

This study proposed a simulated test method using ring specimen to evaluate the deformation and failure characteristics of pipe elbows under a large amplitude cyclic load. The validity of the test method was demonstrated by finite element (FE) analysis of pipe elbow and ring specimen under cyclic loads. The results showed that the proposed test method adequately simulates the distribution of circumferential strain at crown of pipe elbows where cracks occur under cyclic loads and presents the cyclic hardening behavior of pipe elbows. The parametric FE analysis showed that consistent simulated test results could be obtained when the test section of the ring specimen is longer than 1/2 of the inner diameter of the ring specimen and the radius of the inner loading jig is less than 1/4 of the inner diameter of the specimen.

• Journal of Welding and Joining
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• v.12 no.4
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• pp.151-161
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• 1994

FCAW has wide application in ship fabrication, maintenance and field erection. It has many advantages over SMAW.SAW and GMAW process. In many applications, the FCAW provides highquality weld metal. This method can reduce weld defects especially porosity and spatter. But the fatigue characteristics of those deposited metal have been rarely investigated. The purpose of this study is to investigate the cyclic stress-strain behavior and fatigue tests by the constant strain control were carried out on the rounded smooth specimen with deposited metal using the metal type flux cored wire. As the results of this study for the deposited metal welded by the metal type flux cored wire, the hardening or softening characteristics under cyclic load were investigated and cyclic stress-strain curve, strain-fatigue life curve, stress-strain function and fatigue life relation which are useful to estimate the fatigue life under the stress concentration condition were obtained.

• Geomechanics and Engineering
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• v.14 no.1
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• pp.1-8
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• 2018

This paper presents an investigation of the liquefaction characteristics and particle crushing of isotropically consolidated silica sand specimens at a wide range of confining pressures varying from 0.1 MPa to 5 MPa during undrained cyclic shearing. Different failure patterns of silica sand specimens subjected to undrained cyclic loading were seen at low and high pressures. The sudden change points with regard to the increasing double amplitude of axial strain with cycle number were identified, regardless of confining pressure. A higher cyclic stress ratio caused the specimen to liquefy at a relatively smaller cycle number, conversely producing a larger relative breakage $B_r$. The rise in confining pressure also resulted in the increasing relative breakage. At a specific cyclic stress ratio, the relative breakage and plastic work increased with the rise in the cyclic loading. Less particle crushing and plastic work consumption was observed for tests terminated after one cyclic loading. Majority of the particle crushing was produced and majority of the plastic work was consumed after the specimen passed through the phase transformation point and until reaching the failure state. The large amount of particle crushing resulted from the high-level strain induced by particle transformation and rotation.

• Geomechanics and Engineering
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• v.34 no.5
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• pp.481-489
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• 2023

Drained cyclic triaxial tests were conducted on a saturated sand to examine its deformation characteristics under either axial or lateral cyclic loading condition. To apply lateral cyclic loading, the cell pressure was cycled while maintaining a constant vertical stress. The strain accumulations and flow direction in the soil were presented and discussed considering various initial stress ratios (η₀), cyclic stress amplitudes and cyclic stress paths. The results indicate that axial strain accumulation shows an exponential increase with the maximum stress ratio (η^max). The initial deviatoric stress has comparable effects with lateral cyclic stress amplitude on the accumulated axial strain. In contrast, the accumulated volumetric strain is directly proportional to the lateral cyclic stress amplitude but not much affected by η₀ values. Due to the anisotropy of the soil, the accumulated axial and lateral bulging strains are greater in lateral cyclic loading when compared to axial cyclic loading even though η^max is the same. It is also found that η^max affects soil's lateral deformation and increasing the ratio could change the lateral deformation from contraction to bulging. The flow direction depends on η^max in the sand under lateral cyclic loading, regardless of η₀ values and the cyclic stress amplitudes, and a large η^max could lead to great deviatoric strain but a little volumetric strain accumulation.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.730-737
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• 2004

In this paper, in order to examine cyclic hehavior characteristics and safety of underground flexible pipes for electric cables subject to cyclic vehicle load, FEM analysis and cyclic soil box test were carried out. As results of the test, it was revealed that the vertical displacement of the test was larger than that of FEM analysis because thermal effect arising from power cables made reduction of rigidity of the pipe so that large deformation of the pipe induced by the heat occured. Moreover, it was shown that the final vertical displacement under about 0.4 million times of the cyclic load test was not satisfied with elastic allowable displacement of the pipe, and long term stability of the pipe was not stable since behavior characteristics of the pipe exists plastic strain range pasted clastic strain range.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.9-12
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• 2004

Coupling beams subject to cyclic loads exhibit different behavioral characteristics and energy dissipation capacity varying with re-bar layouts. In the present study, nonlinear analysis method was developed using analogous truss model. Using the numerical method, parametric studies were performed to investigate the behavioral characteristics and the energy dissipation mechanism of coupling beams with various re-bar layouts subject to cyclic loading. Based on the investigation, a simple and practical method for evaluating the energy dissipation capacity of coupling beams was developed and verified by experiments. The proposed method accurately predicted the dissipated energy during cyclic loading addressing design parameters such as re-bar layouts, re-bar ratio, and deformation. The proposed method can be easily applied to nonlinear static and dynamic methods for seismic analysis and design.

• Journal of KSNVE
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• v.10 no.3
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• pp.523-530
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• 2000

In this paper we present an efficient method for finite element vibration analysis of a structure with cyclic symmetry and applied it to calculating the natural vibration characteristics for a blower impeller. Blower impeller having a cyclically symmetric structure is composed of circumferentially repeated substructures., The whole-structure is partitioned into substructures and then finite element vibration analysis is performed for a substructure using transformed equations for each number of nodal diameter which are derived from discrete Fourier transform in consideration of the cyclic symmetry. natural vibration characteristics for three kinds of models which are blower impeller without support ring with small support ring and with large support ring are numerically analyzed and compared. Accuracy and efficiency of the present method are verified by comparison of results of the analysis with substructure and with whole-structure. Also the results of the analysis by cyclic symmetry module(SOL 115) of MSC/NASTRAN are presented and compared.