• Journal of the Society of Naval Architects of Korea
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• v.29 no.2
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• pp.103-114
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• 1992

A study result of buckling reliability is presented for the axially compressed imperfect elastic cylinder. Multi-mode analysis program is developed from Karman-Donnell Equation for the calculation of the buckling load of the cylindrical she1l. Geometric intial imperfection is approximated by double Fourier series of which coefficients are assumed random variables with jointly normal distribution characteristics. Crude Monte Carlo simulation technique is used to calculate the probabilistic failure properties of several cases with various imperfection Conditions.

• Steel and Composite Structures
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• v.1 no.4
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• pp.411-426
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• 2001

This paper treats the failure analysis of prestressing steel wires with different kinds of localised damage in the form of a surface defect (crack or notch) or as a mechanical action (transverse loads). From the microscopical point of view, the micromechanisms of fracture are shear dimples (associated with localised plasticity) in the case of the transverse loads and cleavage-like (related to a weakest-link fracture micromechanism) in the case of cracked wires. In the notched geometries the microscopic modes of fracture range from the ductile micro-void coalescence to the brittle cleavage, depending on the stress triaxiality in the vicinity of the notch tip. From the macroscopical point of view, fracture criteria are proposed as design criteria in damage tolerance analyses. The transverse load situation is solved by using an upper bound theorem of limit analysis in plasticity. The case of the cracked wire may be treated using fracture criteria in the framework of linear elastic fracture mechanics on the basis of a previous finite element computation of the stress intensity factor in the cracked cylinder. Notched geometries require the use of elastic-plastic fracture mechanics and numerical analysis of the stress-strain state at the failure situation. A fracture criterion is formulated on the basis of the critical value of the effective or equivalent stress in the Von Mises sense.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.5
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• pp.1505-1516
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• 2014

In this study, a cylinder embedded within cemented soils was used to cause directly tensile failure of cemented soils. An existing dumbbell type direct tensile test and a split tensile test that is most general indirect tensile test were also carried out to verify the developed built-in cylinder tensile test. Testing specimens with two different sand/cement ratios (1:1 and 3:1) and two curing periods (7 and 28 days) were prepared and tested. Total 10 specimens were prepared for each case and their average value was evaluated. Unconfined compression tests were also carried out and the ratio of compressive strength and tensile strength was evaluated. The tensile strength determined by built-in cylinder tensile test was slightly higher than that by dumbbell type direct tensile test. The dumbbell type test has often failed in joint part of specimen and showed some difficulty to prepare a specimen. Among three tensile testing methods, the standard deviation of tensile strength by split tensile test was highest. It was shown that the split tensile test is applicable to concrete or rock with elastic failure but not for cemented soils having lower strength.

• Journal of the Korean Geotechnical Society
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• v.19 no.5
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• pp.35-47
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• 2003

In the conventional axial load transfer analysis for composite piles (i.e., steel pipe pile filled with concrete), it was assumed that the concrete's strain is same as the measured steel's strain and the elastic modulus of the steel and the concrete calculated by formular as prescribed by specification is used in calculation of pile axial load. But, the pile axial load calculated by conventional method had some difference with the actual pile load. So, the behavior of a composite pile could not be analyzed exactly. Thus, the necessity to measure the strain for each pile components was proposed. In this study, the verification test for DRS (Deformable Rod Sensor) developed to measure the strain of each pile component (i.e., the steel and the concrete) was performed. In the calculation of pile axial load using the DRS, elastic modulus of concrete could be determined by the uniaxial compression test for the concrete cylinder samples made in the test site and an average tangential modulus in the stress range of (0.2∼0.6)f$_ck$ was taken.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.4
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• pp.621-629
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• 1992

This study is concerned with an application of the Boundary Element Method to 2-dimensional elastoplastic stress analysis on the material nonlinearities. The boundary integral formulation adopted an initial stress equation in the inelastic term. In order to determine the initial stress increment, the increment of initial elastic strain energy due to elastic increment in stressstrain curve was used as the convergence criterion during iterative process. For the validity of this procedure, the results of B.E.M. with constant elements and NISA with linear elements where compared on the thin plate with 2 edge v-notches under static tension and the thick cylinder under internal pressure. And this paper compared the results of using unmedical integral with the results of using semi-analytical integral on the plastic domain integral.

• Smart Structures and Systems
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• v.26 no.5
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• pp.619-629
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• 2020

Solar towers, which often has a large aspect ratio and low fundamental natural frequency, were extremely prone to large amplitude of wind-induced vibrations, especially Vortex-Induced Vibration (VIV). A tiny Tuned Mass Damper (TMD) with conveniently adjustable eddy current damping was specially designed and manufactured for elastic wind tunnel tests of a solar tower. A series of numerical simulations by using the COMSOL software were conducted to determine three key parameters, including the thickness of the back iron plate and the conductive plate (T_b and T_c), the distance between the magnet and the conductive plate (T_d). Based on the results of numerical simulations, a tiny TMD was manufactured and its structural parameters were experimentally identified. The optimized values of the tiny TMD can be conveniently realized. The tiny TMD was installed at the top of the elastic test model of a 243-meter-high solar tower, and a series of wind tunnel tests were carried out to examine the effectiveness of the TMD in suppressing wind-induced responses of the test model. The results showed that the wind-induced responses could be obviously reduced by the TMD, especially in the cross-wind direction. The cross-wind RMS and peak responses at the critical wind velocity can be reduced by about 86% and 75%, respectively. However, the maximum reduction of the responses at the design wind velocity is about 45%, obviously less than that at the critical wind velocity.

• Journal of the Korean Society of Safety
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• v.18 no.1
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• pp.76-80
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• 2003

There will be a big problem in disposing of waste tie coming from the cars. Because many of these have been thrown away to the field and environmentally polluted. New, We need to find out how to dispose or recycle these waste material. It is thought that recycling this material especially mixing with concrete will be a good idea. This study is focused how each material do its behavior due to the size of waste type particle and its amount into concrete material. 0.4mm-10mm range of particle has been applied to the material : Also, 1.0%, 1.5%, 2.0% range of tyre particle proportion has been applied to make cylinder molds. The concrete mold with waste-tyre particle has vibration-absorbing ability. It is found that 0.4 -0.6mm particle mixing concrete has been more solid organized. And this waste tyre material could be applied to the general concrete, it is found.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.176-181
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• 2002

The continuous Gabor wavelet transform (GWT) has been utilized as a useful time-frequency analysis tool to identify the rapidly-varying characteristics of some wave signals. In the application of GWT, it is important to select the Gabor wavelet with the optimal shape factor by which the time-frequency distribution of a signal can be accurately estimated. To find the signal-dependent optimal Gabor wavelet shape factor, the notion of the Shannon entropy which mesures the extent of signal energy concentration in the time-frequency plane is employed. To verify the validity of the present entropy-based scheme, we have applied it to the time-frequency analysis of a set of elastic bending wave signals generated by an impact in a solid cylinder.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.05a
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• pp.239-244
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• 2001

Hot hydrostatic extruder was developed. The main objective of the development is forming fine wire and tube. On account of effectiveness and high performance, the extruder was designed to have double action. Therefore the main cylinder and mandrel can be driven independently. To cope with severe condition of high temperature and pressure, wire-wound container equipped with heater was used. Sealing technique also is important in this process, so seal ring was made of super-elastic metal. Another key for successful forming is choice of proper pressure medium. Fine wire and tube produced by the extruder can be used in semiconductor industry and medicine.

• Journal of the korean Society of Automotive Engineers
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• v.11 no.5
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• pp.76-89
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• 1989

With the objective of studying the response of brain tissue in a transient rotational acceleration of the head, as occurs in car crash, the problem of a cylindrical case containing a prototype brain material of silicone gel and subjected to a rotational acceleration around the axis of the cylinder is analysed. The prototype material is considered to be homogeneous and isotropic, and is modeled alternatively as a linear elastic or a linear viscoelastic solid. The computational model for the present problem consists of a 3-dimensional isoparametric finite element model, wherein large deformations and large strains are treated through the updated Lagrangian approach. A comparison of the results of the present 3-dimensional computations, with the attendant assumptions on material data, is made with the results of independent experimental study. The deformation profiles and the major characteristics of response of the brain material are in good agreement with the test results. Moreover, the study suggests the possibility that the use of more accurate material data may yield very useful results even appropriate for accurate quantification of deformations.