• Title/Summary/Keyword: Critical Geometry

Search Result 309, Processing Time 0.024 seconds

Effect of Crack Propagation Directions on the Interlaminar Fracture Toughness of Carbon/Epoxy Composite Materials (탄소섬유/에폭시 복합재료의 층간파괴인성에 미치는 균열진전각도의 영향)

  • Hwang, Jin-Ho;Hwang, Woon-Bong
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.23 no.6 s.165
    • /
    • pp.1026-1038
    • /
    • 1999
  • Interlaminar fracture toughness of carbon/epoxy composite materials has been studied under tensile and flexural loading by the use of width tapered double cantilever beam(WTDCB) and end notched flexure(ENF) specimens. This study has significantly examined the effect of various interfacial ply orientation, ${\alpha}(0^{\circ},\;45^{\circ}\;and\;90^{\circ})$ and crack propagation direction, ${\theta}(0^{\circ},\;15^{\circ},\;30^{\circ}\;and\;45^{\circ})$ in terms of critical strain energy release rate through experiments. Twelve differently layered laminates were investigated. The data reduction for evaluating the fracture energy is based on compliance method and beam theory. Beam theory is used to analyze the effect of crack propagation direction. The geometry and lay-up sequence of specimens are considered various conditions such as skewness parameter, beam volume, and so on. The results show that the fiber bridging occurred due to the non-midplane crack propagation and causes the difference of fracture energy evaluated by both methods. For safer and more reliable composite structures, we obtain the optimal stacking sequence from initial fracture energy in each mode.

Accelerated Seaward Growth of Tidal Sand Bar during Giant Dyke Construction off the Mangyung River Mouth, West Coast of Korea

  • Lee, Hee-Jun;Choi, Kang-Won;Eo, Dae-Su;Chu, Yong-Shik
    • Journal of the korean society of oceanography
    • /
    • v.36 no.3
    • /
    • pp.72-82
    • /
    • 2001
  • The progress of giant dyke construction off the Mangyung and Donajin rivers, has yielded enormous impact on the estuarine environment, both hydrodynamically and sedimentologically. Especially the inter-dyke gap in the northern Saemankeum area, 4 km wide between Yamido and Piungdo, has acted as an artificial tidal inlet. Due to such a changed geometry, tidal regime has been reversed from being flood- to ebb-dominated with a directional change from NE-SW to E-W. As a result, a large tongue-like tidal sand bar (named Saemankeum Bar) has conspicuously grown seaward through the artificial tidal inlet. The Saemankeum Bar composed of well-sorted very fine sands (3.0-3.5${\phi}$) has grown at a rate of 1.63 km/yr for the past three yews (1996-1998). Such a rapid growth of the sand bar is attributed to enhanced sediment supply derived from the degradation of former tidal sand bars at the mouth of the Mangyung River. Eventually the reworking of the tidal sand bars also caused the pre-existing tidal channels to be wider, deeper and more straightened. All of these phenomena well examplify the critical effect of artificial modifications on the natural estuarine environments.

  • PDF

A numerical deformation analysis of micro elements by stamping orders (스탬핑 순서가 미치는 미세요소 변형 수치해석)

  • Lee, Chang-Hee;Kim, Yong-Yun
    • Journal of the Korean Society for Precision Engineering
    • /
    • v.22 no.12 s.177
    • /
    • pp.156-162
    • /
    • 2005
  • In this paper, we study the mechanism of lead deformation by numerically simulating the stamping process by means of a commercial finite element code. It is very important to analyze effects that the lead shape makes on the lead deformation, because the lead shape is often modified in order to minimize the deformation or to increase the buckling critical load of the punch. Therefore the stamping process, first, numerically simulated by considering as a quasi-static problem. Second, the effect on the lead deformation due to the lead shape variation, a linear lead geometry and a bent lead, was numerically analyzed and discussed. Finally, the punching order was optimized fur multi-lead generating stamping process. The results show that the bent lead is little bit more shifted than the linear lead after the punching process. But the bent lead is vertically less deformed than the linear lead. The punching order to successively generate the lead is good to keep the lead space uniform. The results will be very effectively applied for the design of the blanking or punching dies in industry.

Lubrication of Contact Area in Ball Reducer with Waved Grooves (파형 구름볼 감속기의 접촉점에서의 윤활특성 해석)

  • Jang, Si-Youl;Park, Kyoung-Kuhn;Kim, Wan-Doo
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
    • /
    • 2002.05a
    • /
    • pp.143-149
    • /
    • 2002
  • Ball reducer with waved grooves has many advantages over other reducers for the high-reduction ratios, low noise and low energy loss, etc. The mechanism of force transmission is very similar to that of cam and follower in automobile valve train system especially in the contact geometry. In this study, we have investigated the traces of contact between ball and outer race and the working behaviors with a certain reduction ratio. In order to verify the contact behaviors between ball and outer race, which determines the critical endurance life the contact velocity and load are computed for a cycle. During some period of a cycle, the contact velocity reverses its direction very suddenly, which causes undesirable endurance performance of this machinery. From the computational investigation in this work, we hope to predict similar contact damages in other machinery due to this kind of contact behaviors, which is very common in many contact phenomena.

  • PDF

Numerical Evaluation of Hemming Defects Found on Automotive Door Panels (유한요소해석에 의한 자동차 도어패널의 헤밍 결함 평가)

  • Seo, O.S;Jeon, K.Y;Rhie, C.H;Kim, H.Y
    • Transactions of Materials Processing
    • /
    • v.24 no.4
    • /
    • pp.280-286
    • /
    • 2015
  • Hemming is used to connect two sheet metal components by folding the edge of an outer panel around an inner panel to create a smooth edge. The minimization of hemming defects is critical to the final quality of automobile products because hemming is one of the last operations during fabrication. Designing the hemmed part is not easy and is influenced by the geometry of the bent part. Therefore, the main problem for automotive parts is dimensional accuracy since formed products often deviate geometrically due to large springback. Few numerical approaches using 3-dimensional finite element model have been applied to hemming due to the small element size which is needed to properly capture the bending behavior of the sheet around small die corner and the comparatively big size of automotive opening parts, such as doors, hoods and deck lids. The current study concentrates on the 3-dimensional numerical simulation of hemming for an automotive door. The relationship between the design parameters of the hemming operation and the height difference defect is shown. Quality improvement of the automotive door can be increased through the study of model parameters.

Experimental Study and Correlation Development of Critical Heat Flux under Low Pressure and Low Flow Condition

  • Kim, Hong-Chae;Baek, Won-Pil;Kim, Han-Kon;Chang, Soon-Heung
    • Proceedings of the Korean Nuclear Society Conference
    • /
    • 1997.05a
    • /
    • pp.356-361
    • /
    • 1997
  • To investigate parametric effect on CHF and to get CHF data, experimental study has been performed with vertical round tubes under the condition of low pressure and low flow (LPLF). Test sections are made of Inconel-625 tube and have the geometry of 8 and 10 mm in diameter, and 0.5 and 1.0 m in heated length. All experiments have been conducted at the pressure of under 9 bar, the mass flux of under 250 kg/$m^2$ and the inlet subcooling of 350 and 450 kJ/kg, for stable upward flow with water as a coolant. Flow regime analysis has been performed for obtained CHF data with Mishima's flow regime map, which reveals that most of the CHF occur in the annular-mist flow regime. General parametric trends of the collected CHF data are consistent with those of previous studies. However, for the pressure effect on CHF, two different are observed; For relatively high mass flux, CHF increases with pressure and far lower mass flux, CHF decrease with pressure. Using modern data regression tool, ACE algorithm, two new CHF correlations for LPLF condition are developed based on local condition and inlet condition, respectively. The developed CHF correlations show better prediction accuracy compared with existing CHF prediction methods.

  • PDF

Design of a Magnet Assembly for an NMR Based Sensor Using Finite Element Analysis

  • Cho, S.I.;Chung, C.H.;Kim, S.C.
    • Agricultural and Biosystems Engineering
    • /
    • v.1 no.1
    • /
    • pp.49-53
    • /
    • 2000
  • A magnet assembly is a critical element of a nuclear magnetic resonance(NMR) based sensor. Magnetic flux density and homogeneity are essential to its optimum performance. Geometry and magnet material properties determine the magnetic flux density and homogeneity of the assembly. This study was carried out to develop the design for a magnet assembly. A 2-D finite element model for the magnetic assembly was developed using ANSYS and evaluated the effects of adding shimming frames and steel bars in the corners of the rectangular steel cover which surrounded the magnet. The assembly was manufactured and evaluated. According to the ANSYS model, modified pole frames increased magnetic flux density by 8.3% and increased homogeneity by 83%. Addition of steel bars in the corners increased the magnetic flux density by 1%, and improved homogeneity up to three times. The difference between simulated and measured magnetic flux densities at the center point of the air gap was within 2.4%.

  • PDF

Design of Roll-to-Roll Forming Process for Micro Pattern on the Thin Sheet Metal by Finite Element Analysis (유한요소해석을 이용한 마이크로 박판 미세 패턴 롤-롤 성형공정 설계)

  • Cha, S.H.;Shin, M.S.;Lee, H.J.;Kim, J.B.
    • Transactions of Materials Processing
    • /
    • v.19 no.3
    • /
    • pp.167-172
    • /
    • 2010
  • Roll-to-roll forming process is one of important metal processing technology because the process is simple and economical. These days, with these merits, roll-to-roll forming process is tried to be employed in manufacturing the circuit board, barrier ribs and solar cell plate. However, it is difficult to apply to the forming of micro scale or sub-micro scale pattern. In this study, the roll forming processing for the micro scale is designed and analyzed. The forming of micro pattern for small electric device such as LCD panel by incremental roll forming process is analyzed. Firstly, the optimum analysis conditions are found by several analyses. And then, formability is analyzed for various protrusion shapes at various forming temperatures. The formability is evaluated in terms of filling ratio and damage value. The filling ratio is defined from the tool geometry and critical damage is determined from the analysis of uniaxial tensile test. Finally, optimum forming conditions that guarantee the successful forming are found.

Numerical Study on Reduction in Frictional Loss for a Sandwitch Type of Pressure Regulator (정압기의 유체력 손실 저감에 대한 수치해석적 연구)

  • Seo, Dong-Kyun;Lee, Jung-Hoon;Hwang, Jung-Ho;Kim, Kwang-Soo;Kim, Kang-Dae;Kim, Dong-Soo
    • Journal of the Korean Institute of Gas
    • /
    • v.14 no.2
    • /
    • pp.47-52
    • /
    • 2010
  • The development of energy saving system with pressure regulator has recently been received interests. Since the internal geometry in the pressure regulator is small and complex, the frictional loss in it is critical. In this study, the pressure loss with tip size, tip position, and mass flow was investigated using numerical approaches(CFD). The aimed reduction in pressure were achieved as the ratio of t/T was more than 0.8. In addition, there was no effect of the tip position.

Robust Design of Shot Sleeve Wall Thickness for a Horizontal Pressure Die Casting Machine (수평형 고압다이캐스팅용 샷슬리브의 강건설계)

  • Park, Y.K.;Kim, J.G.
    • Journal of Power System Engineering
    • /
    • v.11 no.2
    • /
    • pp.51-57
    • /
    • 2007
  • As a shot sleeve in die casting plays a critical role in delivering molten metal to a die cavity, any disruption to its function in the injection stage results in deterioration of the quality of final castings. To guarantee a smooth operation of a shot sleeve, its structural stability should be maintained. Despite the simple geometry, design of shot sleeve is based on individual engineer's experience and no agreement on the design is present. In this study, we newly propose a systematic methodology to determine a minimum wall thickness of a shot sleeve to prevent yielding or plastic deformation. Analytical calculations incorporating numerical analysis produce a rational design rule for minimum thickness of a shot sleeve subject to metal intensification pressure and geometric die constraint. To validate the proposed design guideline, authors present real data on a collection of actual shot sleeves. Upon checking their conformity to the new design rule, we discovered a strong correlation between the design of wall thickness and premature failures.

  • PDF