• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2000년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Spring
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• pp.63-69
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• 2000

Korea Institute of Geology Mining and Materials(KIGAM) cooperating with Southern Methodist University(SMU) has been operating seismo-acoustic array in Chul-Won area to discriminate man-made explosions from natural earthquakes since at the end of July 1999. In order to characterize propagation parameters of detected seismo-acoustic signal and to associate these signals as a blast event accompanying seismic and acoustic signals simultaneously it is necessary to understand infrasound wave propagation in the atmosphere. Two comparable Effective Sound Velocity Structures(ESVS) in atmosphere were constructed by using empirical model (MSISE90 and HWM93) and by aerological observation data of Korea Meteorological Administration (KMA) at O-San area. Infrasound propagation path computed by empirical model resulted in rare arival of refracted waves on ground less than 200km from source region. On the other hand Propagation paths by KMA more realistic data had various arrivals at near source region and well agreement with analyzed seismo-acoustic signals from Chul-Won data. And infrasound propagation in specific direction was very influenced by horizontal wind component in that direction. Linear travel time curve drawn up by 9 days data of the KMA in autumn season showed 335.6m/s apparent sound velocity in near source region. The propagation characteristics will be used to associate seismo-acoustic signals and to calculate propagation parameters of infrasound wave front.

• 한국정밀공학회지
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• 제18권9호
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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.

• 한국축산시설환경학회지
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• 제5권2호
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• pp.79-86
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• 1999

Recently more dairy farmers are interested in the utilization of stretch film for wrapping silage material. Most of stretch film are imported from abroad and one domestic product was developed, but its quality has not yet been tested. Therefore this study was executed to offer basic data on this material to the farmers. Measured items were tensile load, extension ratio, and tear propagation strength of stretch films. Comparisons were made among the white color of domestic product(Kw), and white(Fw), black (Fb) and green color(Fg) of foreign products. The result were summarized as follows: 1. Tensile loads of lengthwise direction in stretch films were 557.4, 377.4, 282.6 and 398.4kgf/$\textrm{cm}^2$ in Kw, Fw, Fb and Fg, respectively, and tensile loads of width direction were 415.9, 418.1, 360.2 and 433.0kgf/$\textrm{cm}^2$ in Kw, Fw, Fb and Fg, respectively. 2. Extension ratios of lengthwise direction were 650, 462.5, 512.5% and 537.5% in Kw, Fw, Fb and Fg, respectively, Extension ratios of width direction were 930, 962.5, 950 and 1,000% in Kw, Fw, Fb and Fg, respectively. 3 Tear propagation strength of lengthwise direction 187.9, 148.9, 157.3 and 142.8kgf/cm, and tear propagation strength of width direction were 141.4, 129.8, 140.4 and 106.6kgf/cm in Kw, Fw, Fb and Fg, respectively. 4. In the light transmittance, there was no difference between white and green color stretch film, but it was very low in black one. Therefore, it is thought that research on quality of roll bale silage treated with each stretch film would be needed.

• Journal of Welding and Joining
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• 제6권3호
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• pp.43-55
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• 1988

An experimental study was carried out to identify the fatigue fractue behavior of weld zone in generally rolled steel for marine structure. The bending an shear loads were applied simultaneously on the specimens to simulate real load condition for marine structure. The effect of the stress intensity factor under mode I with II loading condition on the initiation and the propagation of a crack were investigated, with particular emphaiss on mode II. When the $K_{II}$ stress intensiy factor in mode II was applied under mode I load condition, the growth behavior of a crack seems to be affected mainly by the anisotropic characteristic of materials. Especially, when the crack was located in and near the weld zone and parallel to th weld line, the propagation behaviour was turned out to be quite different from that of the base metal along the direction transverse to the weld line. In general, the propagation veiocity of the cracks in and near the weld zone was found to be slower that the velocity in base metal.

• 마이크로전자및패키징학회지
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• 제17권3호
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• pp.33-41
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• 2010

Crack propagation mechanisms of Sn-3.0Ag-0.5Cu solder were studied in strain controlled push-pull creepfatigue conditions using the fast-fast (pp) and the slow-fast (cp) strain waveforms at 313 K. Transgranular cracking was found in the pp strain waveform which led to the cycle-dominant crack propagation and intergranular cracking in the cp strain waveform that led to the time-dominant crack propagation. The time-dominant crack propagation rate was faster than the cycle-dominant crack propagation rate when compared with J-integral range which resulted from the creep damage at the crack tip in the cp strain waveform. Clear recrystallization around the crack was found in the pp and the cp strain waveforms, but the recrystallized grain size in the cp strain waveform was smaller than that in the pp strain waveform. The cycle-dominant crack propagated in the normal direction to the specimen axis macroscopically, but the time-dominant crack propagated in the shear direction which was discussed in relation with shear micro cracks formed at the crack tip.

• 한국자동차공학회논문집
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• 제16권3호
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• pp.15-22
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• 2008

Applications of bonded dissimilar materials such as integrated circuit(IC) packages, ceramics/metal and resin/metal bonded joints, are very increasing in various industry fields. It is very important to analyze the thermal stress and stress singularity at interface edge in bonded joints of dissimilar materials. In order to investigate the IC package crack propagating from the edge of die pad and resin, the fracture parameters of bonded dissimilar materials and material properties are obtained. In this paper, the thermal stress and its singularity index for the IC package were analyzed using 2-dimensional elastic boundary element method(BEM). From these results, crack propagation direction and path by thermal stress in the IC package were numerically simulated with boundary element method.

• 한국생산제조학회지
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• 제18권4호
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• pp.401-409
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• 2009

This paper presents a method of calculating the stress intensity factor (K) and crack propagation direction (${\theta}_0$) at the crack-tip that is associated with delamination in the large scale integration(LSI) package. To establish a reasonable strength evaluation method and life prediction, it is necessary to assess fracture parameters under various fracture conditions. Therefore, we conducted quantitative stress singularity analysis considering thermal stress simulating the changes of crack length (a), (h) and (v) in delamination using the 2-dimensional elastic boundary element method (BEM), and from these results predicted crack propagation direction and path.

• 천문학회보
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• 제38권2호
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• pp.96.1-96.1
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• 2013

A Forbush decrease(FD) is a depression of cosmic ray intensity observed by ground-based neutron monitors(NMs). The cosmic ray intensity is thought to be modulated by the heliospheric magnetic structures including the interplanetary coronal mass ejection(ICME) surrounding the Earth. The different magnitude of the decreasing in intensity at each NM was explained only by the geomagnetic cutoff rigidity of NM station. However, sometimes NMs of the almost same rigidity in northern and southern hemispheres observe the asymmetric intensity depression magnitudes of FD events. Thus, in this study we intend to see the effects on cosmic ray intensity depression rate of FD event recorded at different NMs due to different ICME propagation direction as an additional parameter in the model explaining the cosmic ray modulation. Fortunately, since 2006 the coronagraphs of twin spacecraft of the STEREO mission allow us to infer the propagation direction of ICME associated with the FD event in 3-dimension with respect to the Earth. We confirm that the asymmetric cosmic ray decreasing modulations of FD events are determined by the propagation directions of the associated ICMEs.

• Computers and Concrete
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• 제14권1호
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• pp.91-107
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• 2014

Using the principle of damage mechanics, zero-thickness pore pressure cohesive elements (PPCE) are used to simulate the casing-cement interface (CCI) and cement-rock interface (CRI). The traction-separation law describes the emergence and propagation of the PPCE. Mohr-coulomb criteria determines the elastic and plastic condition of cement sheath and rock. The finite element model (FEM) of delamination fractures emergence and propagation along the casing-cement-rock (CCR) interfaces during hydraulic fracturing is established, and the emergence and propagation of fractures along the wellbore axial and circumferential direction are simulated. Regadless of the perforation angle (the angle between the perforation and the max. horizontal principle stress), mirco-annulus will be produced alonge the wellbore circumferential direction when the cementation strength of the CCI and the CRI is less than the rock tensile strength; the delamination fractures are hard to propagate along the horizontal wellbore axial direction; emergence and propagation of delamination fractures are most likely produced on the shallow formation when the in-situ stresses are lower; the failure mode of cement sheath in the deep well is mainly interfaces seperation and body damange caused by cement expansion and contraction, or pressure testing and well shut-in operations.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1999년도 제29회 춘계학술대회
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• pp.297-302
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• 1999

Finite element analysis is peformed about the crack propagation in half-space due to sliding contact. The analysis is based on linear elastic fracture mechanics and stress intensity factor concept. The crack location is fixed and the friction coefficient between asperity and half-space is varied to analyze the effect of surface friction on stress Intensity factor for horizontal crack. The crack propagation direction is predicted based on the maximum range of shear and tensile stress intensity factor.