• 한국공작기계학회논문집
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• 제15권4호
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• pp.98-104
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• 2006

In this paper, for the purpose of investigation the acoustic emission(AE) behaviors during resistance spot welding process and tension test of spec steels. As the results present the resistance spot welding method that can get suitable welding qualities or structural integrity estimating method. The resistance spot welding process consists of several stages: set-down of the electrodes; squeeze; current flow; forging; hold time; and lift-off. Various types of AE signals are produced during each of these stages. For tensile-shear test and cross tensile test in resistance spot welded specimens, fracture pa 야 ems are produced: tear fracture; shear fracture; and plug fracture. Tensile-shear specimens strength appeared higher than cross tensile specimens one. In case of tensile-shear specimen happened tear fracture that crack happens in most lower plate. Also, in case of cross tensile specimens, upper plate and lower plate are detached perfect fracture was exposed increases a little as acting force is lower than ordinary welding condition. Therefore, the structure which is combined by resistance spot welding confirmed that welding design must attain so that shear stress may can interact mainly.

• Composites Research
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• 제32권1호
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• pp.6-12
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• 2019

본 논문에서는 Cross-ply 탄소섬유/에폭시 복합재 적층판의 모드 I 층간분리 특성을 분석하였다. 이를 위하여 Cross-ply 시편에 대한 Double-Cantilever Beam(DCB) 시험을 수행하였다. Cross-ply DCB 시편의 경우 층간 및 층내 파괴를 포함한 복합적인 균열 성장과 기하학적 대변형에 의한 비선형성을 수반하였다. 따라서 변형률 에너지 해방률과 유한요소해석을 기반으로 비선형성을 수반한 DCB 시험에서도 적용되는 모드 I 층간 파괴인성 평가방법을 제안하고 기존의 선형이론으로 구한 결과와 비교 분석하였다. 본 연구에서 제안한 방법으로 Cross-ply DCB 시편의 모드 I 층간 파괴인성과 모드 I 층내 파괴인성을 분류하였고 모드 I 층내 파괴인성이 더욱 낮음을 확인하였다.

• 한국자동차공학회논문집
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• 제16권2호
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• pp.74-79
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• 2008

The fracture strength of cross groove type constant velocity joint is largely determined by the fracture strength of the cage having window-like pockets for retaining the torque transmitting balls. A stress distribution acting on the cage is influenced by rigidities of the rim portion and of the column members, therefore requires a calculation such as FEA. To analyze fracture strength of cage, a 3-D elasto-plastic finite element analysis and a submodeling technique are used to achieve both computational efficiency and accuracy. The results are in reasonably good agreement with experiment.

• 한국분무공학회지
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• 제18권1호
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• pp.35-43
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• 2013

The empirical correlations for the prediction of breakup length of liquid jet in uniform cross flow are reviewed and classified in this study. The breakup length of liquid jets in cross flow was normally discussed in terms of the distances from the nozzle exit to the column breakup location in the x and y directions, called as column fracture distance and column fracture height, respectively. The empirical correlations for the prediction of column fracture distance can be classified as constant form, momentum flux ratio form, Weber number form and other parameter form, respectively. In addition, the empirical correlations for the prediction of column fracture height can be grouped as momentum flux ratio form, Weber number form and other parameter form, respectively. It can be summarized that the breakup length of liquid jet in a cross flow is a basically function of the liquid to air momentum flux ratio. However, Weber number, liquid-to-air viscosity ratio and density ratio, Reynolds number or Ohnesorge number were incorporated in the empirical correlations depending on the investigators. It is clear that there exist the remarkable discrepancies of predicted values by the existing correlations even though many correlations have the same functional form. The possible reasons for discrepancies can be summarized as the different experimental conditions including jet operating condition and nozzle geometry, measurement and image processing techniques introduced in the experiment, difficulties in defining the breakup location etc. The evaluation of the existing empirical correlations for the prediction of breakup length of liquid jet in a uniform cross flow is required.

• Restorative Dentistry and Endodontics
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• 제29권3호
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• pp.267-272
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• 2004

The purpose of this in vitro study was to evaluate the effect of surface defects and cross-sectional configuration of NiTi rotary files on the fatigue life under cyclic loading. Three NiTi rotary files ($K3^{TM},{\;}ProFile^{\circledR},{\;}and{\;}HERO{\;}642^{\circledR}$) with ＃30/.04 taper were evaluated. Each rotary file was divided into 2 subgroups : control (no surface defects) and experimental group (artificial surface defects), A total of six groups of each 10 were tested. The NiTi rotary files were rotated at 300rpm using the apparatus which simulated curved canal (40 degree of curvature) until they fracture. The number of cycles to fracture was calculated and the fractured surfaces were observed with a scanning electron microscope. The data were analyzed statistically. The results showed that experimental groups with surface defects had lower number of cycles to fracture than control group but there was only a statistical significance between control and experimental group in the $K3^{TM}$ (p<0.05), There was no strong correlation between the cross-sectional configuration area and fracture resistance under experimental conditions. Several of fractured files demonstrated characteristic patterns of brittle fracture consistent with the propagation of pre-existing cracks. This data indicate that surface defects of NiTi rotary files may significantly decrease fatigue life and it may be one possible factor for early fracture of NiTi rotary files in clinical practice.

• Structural Engineering and Mechanics
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• 제71권2호
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• pp.153-163
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• 2019

Longitudinal fracture behavior of non-linear elastic beam configurations is studied in terms of the strain energy release rate. It is assumed that the beams exhibit continuous material inhomogeneity along the width as well as along the height of the crosssection. The Ramberg-Osgood stress-strain relation is used for describing the non-linear mechanical behavior of the inhomogeneous material. A solution to strain energy release rate is derived that holds for inhomogeneous beams of arbitrary cross-section under combination of axial force and bending moments. Besides, the solution may be applied at any law of continuous distribution of the modulus of elasticity in the beam cross-section. The longitudinal crack may be located arbitrary along the beam height. The solution is used to investigate a longitudinal crack in a beam configuration of rectangular cross-section under four-point bending. The crack is located symmetrically with respect to the beam mid-span. It is assumed that the modulus of elasticity varies continuously according a cosine law in the beam cross-section. The longitudinal fracture behavior of the inhomogeneous beam is studied also by applying the J-integral approach for verification of the non-linear solution to the strain energy release rate derived in the present paper. Effects of material inhomogeneity, crack location along the beam height and non-linear mechanical behavior of the material on the longitudinal fracture behavior are evaluated. Thus, the solution derived in the present paper can be used in engineering design of inhomogeneous non-linear elastic structural members to assess the influence of various material and geometrical parameters on longitudinal fracture.

• Geomechanics and Engineering
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• 제14권2호
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• pp.187-193
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• 2018

Water inrush through the destruction of water resisting rock mass structure was divided into direct water inrush, key block water inrush and splitting water inrush. In the direct water inrush, the Reynolds numbers has a significant effect on the distribution of the water flow and vortex occurred in the large Reynolds numbers. The permeability coefficient of the fracture is much larger than the rock, and the difference is between 104 and 107 times. The traditional theory and methods are not considering the effect of inertia force. In the position of the cross fracture, the distribution of water flow can only be linearly distributed according to the fracture opening degree. With the increase of Reynolds number, the relationship between water flow distribution and fracture opening is studied by Semtex.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2004년도 임시총회 및 추계학술발표회
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• pp.155-158
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• 2004

To investigate the in-situ REV, cross-correlations between the ablsolute value of iu/outflux in tested boreholes and fracture frequency with various window widths were calculated. The changes of vertical flow rates can be considered as iu/outflux into/out of borehole. The results of cross-correlation analysis shows that 7m can be the most appropriate width of the appliable window.

• 한국임상수의학회지
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• 제29권2호
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• pp.198-201
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• 2012

한달 된 한우 수송아지가 오른쪽 뒷다리 체중부하를 못하는 문제를 가지고 전북동물의료센터에 내원하였다. 방사선검사와 CT 검사 상에서 Salter-Harris III형의 먼쪽 정강뼈 성장판 골절로 진단하였다. 개방골절정복 후 교차핀을 이용하여 고정한 후 임시 외부 골격 고정장치를 이용하여 5주 동안 추가적인 지지를 실시하였다. 수술 5주 후 방사선사진 검사에서 골절된 뼈의 유합이 관찰 되었다. 수술2년 후 과도한 움직임 뒤에 미약한 체중부하 파행이 관찰 되었지만, 거의 정상 수준으로 보행이 가능하였다. 송아지에서 이와 같은 증례는 매우 드물고 교차핀과 추가적인 임시 외부 골격 고정장치를 이용한 골절 정복법은 먼쪽 정강뼈 골절 치료에 유용하게 사용될 거라고 생각 된다.

• 한국해양공학회지
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• 제13권4호통권35호
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• pp.63-74
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• 1999

This study has been investigated about the influence of moisture environment on the mechanical properties in the carbon fiber cross laminates. And it has been also investigated the effect of unit ply thickness of the carbon fiber cross laminates on the mechanical properties in distilled water of $80^{\circ}C$ for a certain period of time. As a results, it was found that the weight gain of water was increased with the immersion time and the bending strength and fracture toughness were decreased with the weight gain of water. And it was also shown that the bending strength and fracture toughness were decreased with the increasing of the unit ply thickness of carbon fiber cross laminates through the immersion time.