• Title/Summary/Keyword: Smooth Zone

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Evaluation on fracture toughness of high frequency electric resistance welded steel pipe by unloading compliance method (고주파 전기저항 용접강관의 제하 컴플라이언스법에 의한 파괴인성 평가)

  • 오세욱;윤한기;안광주
    • Journal of Welding and Joining
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    • v.5 no.2
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    • pp.44-52
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    • 1987
  • The fracture toughness, $J_{IC}$ of high frequency electric resistance welded steel pipe for smooth and side-grooved CT specimen was evaluated by unloading compliance method. The crack growth, .${\delta}a$ was obtained from the equation of Donald and Saxena & Hudak, and $J_{IC}$ was determined from the curve of J-${\delta}a$ relations. The crack growth on the experiment using unloading compliance method is underestimated as compared with ${\delta}a$ measured directly by the SEM, so the reliability of $J_{IC}$ from saxena & Hudak equation is large than that from Donald. The $J_{IC}$ value of side-grooved CT Specimen is estimated less than that of smooth, and this is the effect of the side-groove, the shear-lip of crack tip and the reduction of crack tunnelling phenomena.

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Characterization of High Temperature Strength of Si3N4 Composite Ceramics According to the Amount of SiO2 Nano Colloidal Added (SiO2 나노 콜로이달 첨가량에 따른 Si3N4의 고온강도 특성)

  • Nam, Ki-Woo;Lee, Kun-Chan
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.33 no.11
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    • pp.1233-1238
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    • 2009
  • This study analyzed the characterization of high temperature strength of $Si_3N_4$ composite ceramics additive based on variations in the amount of nano colloidal $SiO_2$ added. Semi-elliptical cracks about 100 ${\mu}m$ length were obtained from a Vickers indenter using a load of 24.5 N. The results showed that the heat-treated smooth specimens with $SiO_2$ nano colloidal coating exhibited the highest bending strength at 0.0 wt% $SiO_2$ nano colloidal added, which is amounted to a 187 % increase over that of smooth specimen. Limiting temperature for bending strength of crack-healed zone for bending strength was about 1273 K. However, the bending strength of SSTS-3 and SSTS-4 was considerably increased while that of SSTS-1 and SSTS-2 was decreased at a temperature of 1,573K.

Effects of Sodium Fluoride Exposure on the Stages of Amelogenesis and Ameloblast Modulation in Rat Incisors (흰쥐 절치의 법랑질형성과 법랑모세포 변환주기에 불소가 미치는 영향)

  • Jeong, Moon-Jin;Jeong, Soon-Jeong;Choi, Baik-Dong;Lim, Do-Seon
    • Journal of dental hygiene science
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    • v.8 no.2
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    • pp.89-96
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    • 2008
  • Effects of sodium fluoride exposure on the amelogenesis during fetal formation were investigated using 11 days rat incisor of control group and two experimental groups. According to results of morphological analysis using an electron microscope, enamel organ in the rat incisor consisted of presecretory, secretory, and maturation zone, especially maturation zone had ruffle-ended ameloblasts (rAB) that additionally supply inorganic ions and smooth-ended ameloblasts (sAB) that remove water and organic compounds. Such a histological composition was same in fetal and adult rats. According to experimental results using calcein (green fluorescence) in order to reveal the modulation cycle of ameloblast, modulation cycle of experimental group decreased on an average one time than control group, as increase of density of sodium fluoride indicated that thickness of smooth-ended ameloblast decreased. Also ratio of thickness on sagittal total length of sAB increased than rAB in experimental groups than control group. In total length of teeth, an injected 100 ppm sodium fluoride group was similar control group but as injected 200 ppm group became short. In experimental group, thickness of sAB and rAB became narrow to the tip of cutting edge. According to concentration of sodium fluoride grows, the modulation cycle and total length of teeth were decreased, finally it prevented teeth growth.

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Stress Corrosion Cracking Behavior under Cavitation Erosion-Corrosion in Sea Water-Part (II) (해수환경중 캐비테이션 침식-부식 하에서의 응력부식균열 거동 (II))

  • 안석환;임우조
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.36 no.2
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    • pp.139-146
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    • 2000
  • Cavitation can occur in pipes when liquid is moving at high velocity, especially at pittings where the smooth bore of the pipe is interrupted. The effect is usually to produce pitting on the downstream side of the turbulence. However, stress corrosion cracking behavior under cavitation erosion-corrosion was neatly unknown. In this study, therefore, some were investigated of stress corrosion cracking behavior, others were stress corrosion cracking behavior under cavitation erosion-corrosion of water injection. And datas obtained as the results of experiment were compared between the two. Mainresult obtained are as follows: 1) Stress corrosion cracking growth rate of heat affected zone under cavitation erosion-corrosion becomes most rapid, and stress intensity factor $K_1$becomes most high. 2) Stress corrosion cracking growth mechanism by cavitation erosion-corrosion is judgement on the strength of the film rupture model and the tunnel model. 3) The range of potential as passivation of heat affected zone is less noble than that of base metal, and that value is smaller. 4) Corrosion potential under cavitation erosion-corrosion in loaded stress is less noble than that of stress corrosion, and corrosion current density is higher.

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The Origin of the Southeastern United States Continental Margin: Is it Volcanic or Non-Volcanic? (미국남동부 대륙주변부의 기원 : 화산성 혹은 비화산성?)

  • Oh, Jinyong
    • Economic and Environmental Geology
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    • v.27 no.6
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    • pp.571-577
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    • 1994
  • It has been controversial whether the United States Atlantic margin, which developed during Mesozoic separation of Africa and North America, is a volcanic or non-volcanic rifted margin. To understand its nature, the basement images of multi-channel seismic profiles off the southeastern United States continental margin have been examined. One of prominent results is the presence of seaward-dipping reflector (SDR) wedges, the most diagnostic feature of volcanic rifted margins. Two sets of SDR wedges appear to exist here; one along the basement hinge zone ('the hinge SDR wedge') and another seaward of the East Coast magnetic anomaly ('the outer SDR wedge'). Seaward of the basement hinge zone, the lower crustal high-velocity body previously known as the 7.2 km/s layer and the underlying smooth Moho configuration are also observed. Based on the comparison of these basement images with the crustal structures of the well-known volcanic rifted margin, the southeastern United States Atlantic margin can now be characterized as a typical volcanic rifted margin.

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Some Remarkable Earth Surface Processes under the Morpho-climatic regime of Mongolian Steppe Zone (기후지형학 관점에서 본 몽골 스텝지역의 지형형성작용 특색)

  • OH, Kyong-Seob;YANG, Jae-Hyuk;CHO, Heon
    • Journal of The Geomorphological Association of Korea
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    • v.18 no.3
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    • pp.121-129
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    • 2011
  • This work is to elucidate in typological aspect main geomorphological processes in the morphogenetic system of Mongolian steppe zone. Its morphogenesis manifest interaction of intense gelifraction and active erosion either by slope run-off or by wind. Intense gelifraction owes both to cold temperature regime with great amplitude, and to moisture associated with snow fall. Erosion of material produced by gelifraction is assured by surface run-off of summer rainfall and spring eolian activities. The geomorphological landscape sculptured by such morphogenetic processes manifest low-relief smooth slopes. This feature reveals that intense gelifraction keeps abreast with removal of weathering product by surface run-off and wind.

Effect of Coating Weight on the Laser Weldability in the Welding of Aluminized Steels (레이저용접에서 알루미늄 도금량이 용접성에 미치는 영향)

  • Kim Ki Chol;Cha Joon Ho
    • Korean Journal of Materials Research
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    • v.14 no.1
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    • pp.1-8
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    • 2004
  • Laser weldability of aluminized steels for deep drawing application has been investigated. Test coupons for Nd:YAG laser welding and $CO_2$ laser welding were prepared trom the commercial steels. According to the test results, total penetration and back bead width of aluminized steels were sensitive to the welding conditions. Bead width at the half thickness of the overlap joint, however, was rather constant. Laser weldability of aluminized steels was superior to that of zinc coated steel. Weld microstructure revealed that overlap zone adjacent to the fusion line was filled with coated materials, which was thought to be desirable to protect weld from crevice corrosion. The aluminum coated materials was also found in the weld metal. Practically no spattering was observed in the laser welding of aluminized steels even when the welding was performed without joint gap. In the welding of zinc coated steel, however, spattering was so severe that it was difficult to get the acceptable weld. Bead quality of aluminized steel laser weld was smooth and stable.

Computational Treatment for Plotting of the Planar and the Linear Structures in Fault Zone (단층대내(斷層帶內)의 면(面) 및 선구조(線構造)의 도식화(圖式化)를 위한 전산처리(電算處理))

  • Sunwoo, Choon;Lee, Byung-Joo
    • Economic and Environmental Geology
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    • v.23 no.3
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    • pp.359-366
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    • 1990
  • Field sampling requires statistical description to draw inferences from data. Field data, or linear structures, are commonly analyzed by the graphical presentations, such as streonets and rose diagrams. For this purpose the DROPOL program is developed to analyze the data more efficiently with personal computer. DROPOL program written in FORTRAN 77 plots the structural data in points, poles or great circle on equalarea (Schmidt net) or equal-angle (Wulff net) projection surface. It is also capable to project the data from upper or lower hemisphere of stereonet and to draw pole contour diagrams from the plotted data. The rose diagram, representing the frequency of the strike and dip angle, can also be drawn in general or smooth type using $5^{\circ}$ or $10^{\circ}$ degrees interval.

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A study on the micro hole machining of Al2O3 ceramics ($Al_2O_3$ 세라믹의 미세구멍 가공에 관한 연구)

  • 윤혁중
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 1997.10a
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    • pp.37-42
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    • 1997
  • This paper describes result of experiment of parameters affecting the micro hole drilling time, kind of assisting gas and it's pressure. The result reveals that parameter value of 0.08J, 20Hz, dwell time of 300 microseconds can be a good machining condition to make micro hole diameter range of 50-70${\mu}{\textrm}{m}$, Assistant gas such air, O2, Ar, N2 was adapted. Assistant gas of air makes heat affected zone enlarge due to burning of material, also it makes hole irregular and damage because of refusion stick to caused by chemical reaction with Al2O3 ceramic material. O2(99.9%) has good characteristic to get good drilling and smooth surface on pressure of 0.2kgf/$\textrm{cm}^2$, but it is expensive. Ar, N2 makes material burn and crack severely and proved to be an appropriate but, Ar was better than N2.

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Numerical Resistivity Modeling Using Alpha Center Theory: A Case History for Field Resistivity Data (Alpha center를 이용한 전기비저항 수치 모델링 : 현장 탐사 자료에 대한 적용 예)

  • 윤왕중
    • Tunnel and Underground Space
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    • v.7 no.4
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    • pp.334-340
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    • 1997
  • Alpha center theory which was first proposed by Stefanescu has been proved to be effective for the detection of the location of the conductive orebody. A numerical forward modeling was conducted to verify the effectiveness of this method. Field works were carried out along the three profiles in two different areas for the purpose of finding fractured zone which might be accompanied with the presence of the groundwater. And the results were modeled by alpha center method, which was later testified by wellproven 2-dimensional finite difference inversion scheme. Field data could be successfully modeled with this alpha center algorithm, especially for the smooth-varying resistivity models. For the abrupt change of the resistivity values, the alpha center coefficients have a tendency to be negative to simulate the steep resistivity gradients. This method is quite simple and easy for the future applications. The numerical calculation can be performed very quickly with the personal computers.

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