• Title/Summary/Keyword: cross fracture

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A Case Study of Correlation between Inflows and Geological Structures around Underground Caverns (지하 유류저장 공동의 지질구조와 공동누수량 상호관계에 관한 사례)

  • 전한석
    • The Journal of Engineering Geology
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    • v.10 no.1
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    • pp.79-93
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    • 2000
  • When caverns are excavated, it is very important to understand the distribution and charateristics of geological structures because the structures have an significant effect on grouting, rock reinforcement, and groundwater flow, etc. The main water bearing fractures have an orientation of N50~60W and these fractures are known as tension fractures. Their orientation coincides with a long elliptical axis ofpumping test, and they cross the tension fractures of N10~30E. They have typical fracture systems ofrhombic type in this area.

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Design of the Stiffened Punch for Stamping of Lead Frame by Buckling Analysis (좌굴해석을 이용한 리드프레임 타발용 펀치의 보강설계)

  • Ko, Dae-Cheol;Lee, In-Soo;Ahn, Byung-Hwan;Kim, Byung-Min
    • Journal of the Korean Society for Precision Engineering
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    • v.23 no.9 s.186
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    • pp.68-75
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    • 2006
  • The lead frame manufactured by stamping process plays an important role in connecting semiconductor to PCB board. As a result of the miniaturization of semiconductor, its corresponding lead frame punch has been narrow. In case of the punch with high slenderness ratio such as lead frame punch, the punch can be broken suddenly due to buckling. To prevent the fracture of lead frame punch, some manufacturers have experientially attached stiffeners to weak parts of punch. The purpose of this study, therefore, is to suggest the guideline far design of stiffened punch. The optimal position and the number of stiffeners to be attached to punch are investigated by elastic buckling analysis. The elastic buckling analysis consists of the eigenvalue buckling analysis and nonlinear buckling analysis. The critical buckling load of elastic buckling analysis is compared with that of buckling test. Finally, the guideline far attaching stiffeners is suggested through analysis of cross section of lead frame punch such as moment of inertia and eccentricity.

Process Design of Multi-Pass Shape Rolling for Manufacturing Piston Ring Wire (피스톤 링 제조용 선재의 다단 형상 압연공정 설계)

  • Kim, N.J.;Lee, K.H.;Lim, S.H.;Lee, J.M.;Kim, B.M.
    • Transactions of Materials Processing
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    • v.26 no.1
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    • pp.28-34
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    • 2017
  • Multi-pass shape rolling is performed to produce long products of arbitrary cross-sectional shapes. In the past, the multi-pass shape rolling process has been designed by the trial and error method or the experience of experts based on the empirical approach. Particularly, the design of roll caliber in shape rolling is important to improve product quality and dimensional accuracy. In this paper, the caliber design and pass schedule of multi-pass shape rolling were proposed for manufacturing piston ring wire. In order to design roll caliber, major shape parameter and dimension was determined by analysis of various caliber design. FE-simulation was conducted to verify effectiveness of proposed process design. At first, forming simulation was performed to predict shape of the product. Then, fracture of the wire was evaluated by critical damage value using normalized Cockcroft-Latham criteria. The experiment was carried out and the results are within the allowable tolerance.

Prediction Model of Surface Residual Stress for Multi-Pass Drawn High Carbon Steel Wire (고탄소강 다단 신선 와이어의 표면 잔류응력 예측모델)

  • Kim, D.W.;Lee, S.K.;Kim, B.M.;Jung, J.Y.;Ban, D.Y.;Lee, S.B.
    • Transactions of Materials Processing
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    • v.19 no.4
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    • pp.224-229
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    • 2010
  • During the multi-pass wire drawing process, wires suffer a great amount of plastic deformation that is through the cross-section. This generates tensile residual stress at surface of drawn wires. The generated residual stress on surface is one of the problems for quality of wires so that prediction and reduction of residual stresses is important to avoid unexpected fracture. Therefore, in this study, the effect of process variables such as semi-die angle, bearing length and reduction ratio on the residual stress was evaluated through Finite Element Analysis. Based on the results of the Analysis, a prediction model was established for predicting residual stress on the surface of high carbon steel(AISI1072, AISI1082). To identify the effectiveness of the proposed model, X-ray diffraction is used to measure the residual stresses on the surface. As the result of the comparison between calculated residual stresses and measured residual stresses, the model could be used to predict residual stresses in cold drawn wire.

Impact Analysis of the Cervical Spin using a Finite Element Model (유한요소 모델을 이용한 충격력에 따른 경추부의 응답특성 해석)

  • 김영은;박덕용;이춘기
    • Transactions of the Korean Society of Automotive Engineers
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    • v.7 no.5
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    • pp.249-257
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    • 1999
  • A three dimensional finite model of a human neck has been developed in an effort to study the mechanics of cervical spin while subjected to vertical impact. This model consisting of the vertebrae from C1 through C7 including posterior element and ligaments was constructed by 2mm thick transverse CT cross-sections and X-ray film taken at lateral side. Geometrical nonlinearity was also considered for the large deformation on the disc. ABAQUS package was used for calculation and its results were verified comparing with responses of a model under static loading condition with published in-vitro experimental data. There were more cervical fracture in the restrained (compression) mode than in the nonrestrained (flexion-compression and extension-compression) mode. Upper cervical(C1-C2) injuries were observed under compression-extension modes, while lower cervical injuries occurred undjer compression-flexion modes. Posterior ligament distraction without bony damage at the upper cervical spin(C1-C2) were observed secondary to C5-C7 trauma in compression-flexion modes.

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Accelerated the environmental stress cracking (ESC) study of polymer materials using a plastic ruler and a PVC eraser (플라스틱 자와 지우개를 이용한 고분자재료의 환경응력파괴(ESC) 가속실험 방법에 관한 연구)

  • Park, Joon Hyung;Ahn, Won Bae;Yoo, Jin Seong;Kim, Kyoung Mun;Nam, Kyoung Hyun
    • Journal of Applied Reliability
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    • v.13 no.2
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    • pp.141-151
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    • 2013
  • The study of environmental stress cracking (ESC) by contact with plastic rulers and PVC erasers which was artificially added to the external stress was carried out in order to accelerate the chemicals crack. To analyze a blooming plasticizer that migrates from the inside of blended eraser to the surface of the eraser, the ESC experiments were carried out at room temperature and $50^{\circ}C$ conditions. The chemicals crack shape caused by the plasticizer and the brittle fracture shape resulted from the external stress were observed in consequence with the cross-sectional surface analysis of the ruler crack by the ESC. The bending strength of the plastic rulers were fractured prior to the yield point and it had low bending flexure stress. We presented that ESC of polymer materials was affected by the polarity of the chemicals and polymer, the exposure time to chemicals, the exposure temperature and the level of strain on the polymer.

Mechanical Property and Process Variables Optimization of Tube-to-Tube Friction Welding for Steel Pipe with 36 mm External Diameter (외경 36mm 강관의 관대관 마찰용접 특성과 공정 변수 최적화)

  • Kong, Yu-Sik;Park, Young Whan
    • Journal of Power System Engineering
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    • v.18 no.2
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    • pp.50-56
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    • 2014
  • Friction welding is a very useful joining process to weld metals which have axially symmetric cross section. In this paper, for the friction welding with tube-to-tube shape, the feasibility of industry application was determined using analyzing mechanical properties of weld and optimized welding variables was suggested. In order to accomplish this object, rotating speed, friction heating pressure, and friction heating time were selected as the major process variables and the experiment was performed in three levels of each parameter. Weld characteristic was investigated in terms of weld shape and metal loss, and 7mm of metal loss was regarded as the optimal metal loss. By tensile test, tensile strength and yielding strength was measured and fracture was occurred at base metal. In order to optimize the welding condition, fitness function was defined with respect to metal loss and yielding strength and the fitness values for each welding condition could be calculated in experimental range. Consequently, we set the optimal welding condition as the point which had maximum value of fitness function. As the result of this paper the optimal welding variables could be suggested as rotating speed was 1300 rpm, friction heating pressure was 15 MPa, and friction heating time was 10 sec.

Mechanical Strength and Ultransonic Testing of End Cap Welds in Pressurized Heavy Water Reactor Fuel (중수로핵연료 봉단마개 용접부의 기계적 특성과 초음파 시험)

  • 이정원;최명선;정성훈;고진현
    • Journal of Welding and Joining
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    • v.9 no.4
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    • pp.60-68
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    • 1991
  • The weld quality of end cap welds in Pressurized Heavy Water Reactor (PHWR) Fuel is extremely important for the fuel performance in the nuclear reactor. The quality of resistance upset welds is currently evaluated mainly by the metallographic examination although it reveals only two weld cross-sections in a circumference welds. This investigation was, firstly, carried out to determine whether the ultrasonic examination would be applied to detect weld defects in the end cap welds and, secondly, to measure the mechanical strength of upset butt welds as a function of phase shift percentage. The major results obtained in this study are as follows: 1. The weld current and amount of upset shrinkage linearly increased with increasing the phase shift percentage. 2. Above the phase shift 55%, the defects in the welds were completely eliminated with increasing the phase of sound weld was over the thickness of cladding tube. 3. The ultrasonic testing well detected such defects in the end cap welds as upset external crack, upset split, corner crack and irregular weld flash comparing with the results of metallography. 4. The micro-fissure in the corner of the end cap welds was reliably detected by ultrasonic testing. 5. The mechanical strength in the welds increased with increasing phase shift percentage but the fracture did't occur in the welds above 55%.

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The Weldability of Magnesium Alloys for Car Industry

  • Lee, Mok-Young;Chang, Woong-Seong;Yoon, Byung-Hyun
    • Proceedings of the KWS Conference
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    • 2005.06a
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    • pp.370-376
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    • 2005
  • Magnesium alloys are becoming important material for light weight car body, due to their low specific density but high specific strength. However they have a poor weldability, caused high oxidization tendency and low vapor temperature. In this study, the welding performance of magnesium alloys was investigated for automobile application. The materials were rolled magnesium alloy sheet contains Al and Zn such as AZ3l , AZ6l and AZ9l. Three types of welding process were studied, that were GTAW, Laser beam welding and FSW. To evaluate the weldability, we examined the appearance of welding bead. Also we checked bead shape and internal defects such as crack and porosity on cross section of welding bead. The mechanical property was measured for welded specimen by tensile test. For determination of the strength change by welding process, the hardness profile across the welding center was measured. For the results, the tensile properties of welded specimen were decreased obviously on all welding process. For the fusion welding process such as GTAW and laser beam welding, the surface of the welding bead was covered with oxidized magnesium dust but it was removed by simple cleaning work as wipe-out with tissue. Also under cut, that caused vaporization of base metal was occurred. for the friction stir welding, there was no oxidation, under-cut or internal defects. However it had poor weld performance, the reason was cleavage fracture occurred at plastic deformation zone. For welding of magnesium alloy, the laser beam welding process was recommended.

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Effect of Surface Condition on the Bonding Characteristics of 3Y-$ZrO_2$-Metal Bracket System (3Y-$ZrO_2$ 세라믹과 교정용 브라켓계에서 세라믹의 표면 조건에 따른 접착 거동의 변화)

  • O, Seon-Mi;Kim, Jin-Seong;Lee, Chae-Hyun
    • Journal of Technologic Dentistry
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    • v.33 no.1
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    • pp.47-54
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    • 2011
  • Purpose: To investigate shear bonding strength between dental zirconia ceramics with different surface treatment and metal bracket. Methods: Zirconia ceramics(LAVA, 3M ESPE, USA) were divided to 4 groups according to their surface treatment; no surface treatment(G1), sand blasting(G2), silane coating(G3), and sand blasting+silane coating(G4). Specimens were bonded to metal bracket using resin bond($Transbond^{TM}XT$, 3M Unitek, USA). Shear bond strength was measured using universal test machine(3366 INSTRON. U.S.A) with cross head speed of 1 mm/min. Microstructural investigation for fracture surface was performed after shear test. Results: Shear bonding strengths of single surface treatment groups (G2 and G3) were higher than no treatment group(G1). Combined Treatment Group (G4) showed the highest shear bond strength of 9.15MPa. Microstructural observation shows that higher shear bonding strength was obtained when debonding was occurred at metal bracket/resin interface rather than zirconia ceramic/resin interface. Conclusion: Surface treatment of zirconia is necessary to obtain higher bonding strength. Combined treatment can be more effective when surface the surfaces are kept clean and homogeneous.