• Title/Summary/Keyword: Circular Plate

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Hybrid Stress Analysis around a Circular Hole in a Tensile Plate by Use of Phase Shifting Photoelasticity (광탄성 위상이동법에 의한 인장시편 원형 구멍주위 하이브리드 응력해석)

  • Baek, Tae-Hyun;Lee, Choon-Tae;Yang, Min-Bok
    • Journal of the Korean Society for Nondestructive Testing
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    • v.27 no.1
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    • pp.15-22
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    • 2007
  • A hybrid experimental-numerical method is presented for determining the stresses around a circular hole in a finite-width, tensile loaded plate. Measured fringe orders along straight lines provided the input information on the external boundary of the hybrid element. In order to see the effects of varying stress field, different numbers of terms in a power-series representation of the complex type conformal mapping stress function were tested. For qualitative comparison, actual isochromatic fringes were compared with reconstructed theoretical fringes using stress-optic law. For quantitative comparison, relative errors and standard deviations with respective to relative errors were analyzed for all measured points by changing the number of terms of stress function. The hybrid results are highly comparable with those predicted by FEA. The results show that this approach is effective and promising because isochromatic data along the straight lines in photoelasticity can be conveniently measured by use of phase shifting photoelasticity.

Detection and Analysis of Acoustic Emission Signal at the Epicenter on the Circular Glass Plate During Pencil Land Fracture (연필심 파괴시 유리원판의 진앙점에서 음향방출 신호의 검출 및 해석)

  • Lee, Jong-Gyu;Jang, Ji-Won;Park, Jeong-Man
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.26 no.1
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    • pp.1-7
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    • 1990
  • Theoretical evaluations of the vertical displacement at the epicenter on the circular glass plate have been carried out in the case of the unit point loading(1 dyne force strength) with the Heaviside step-function time dependency. Acoustic emission signals generated during pencil lead($\Phi$=0.5mm, HB) fracture on the soda-lime glass($\Phi$=22cm, thickness=2.8cm) were observed by the optical Michelson interferometer with the stabilized circuit, and then the source function of the observed acoustic emission signals was analyzed by the deconvolution method. The source function of acoustic emission during pencil lead fracture had a 'dip' of~0.7$\mu$sec duration time at the front portion and a step function of~0.5$\mu$sec rise time with a force strength of~4.5N.

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Study on Flow Structure of Turbulent Boundary Layer Over Semi-Circular Riblets (반원형 리블렛 상부 난류경계층의 유동 구조 연구)

  • Lee, Sang Hyun;Lee, Sang Joon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.23 no.7
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    • pp.937-944
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    • 1999
  • The near-wall flow structures of turbulent boundary layer over riblets having semi-circular grooves were investigated experimentally for the drag decreasing ($s^+=25.2$) and drag increasing ($s^+=40.6$) cases. The field of view used for tho velocity field measurement was $6.75{\times}6.75mm^2$ in physical dimension, containing two grooves. One thousand instantaneous velocity fields over the riblets were extracted for each case of drag increase and decrease. For comparison, five hundreds instantaneous velocity fields over a smooth flat plate were also obtained under the same flow conditions. To see the global flow structure qualitatively, the flow visualization was also performed using the synchronized smoke-wire technique. For the drag decreasing case ($s^+=25.2$), most of the streamwise vortices stay above the riblets, interacting with the riblet tips. The high-speed in-rush flow toward the riblet surface rarely influences the flow inside tho riblet valleys submerged in the viscous sublayer. The riblet tips seem to impede the spanwise movement of the longitudinal vortices and induce secondary vortices. The turbulent kinetic energy in the riblet valley is sufficiently small to compensate the increased wetted area of the riblets. In addition, in the logarithmic region, the turbulent kinetic energy are small or almost equal to that of a smooth flat plato. For the drag increasing case ($s^+=40.6$), however, the streamwise vortices move into the riblet valley freely, interacting directly with the riblet inner surface. The penetration of the high-speed in-rush flow on the riblets increases tho skin-friction. The turbulent kinetic energy is increased in the riblet valleys and even in the outer region compared to that over a flat plate.

A curved shell finite element for the geometrically non-linear analysis of box-girder beams curved in plan

  • Calik-Karakose, Ulku H.;Orakdogen, Engin;Saygun, Ahmet I.;Askes, Harm
    • Structural Engineering and Mechanics
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    • v.52 no.2
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    • pp.221-238
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    • 2014
  • A four-noded curved shell finite element for the geometrically non-linear analysis of beams curved in plan is introduced. The structure is conceived as a sequence of macro-elements (ME) having the form of transversal segments of identical topology where each slice is formed using a number of the curved shell elements which have 7 degrees of freedom (DOF) per node. A curved box-girder beam example is modelled using various meshes and linear analysis results are compared to the solutions of a well-known computer program SAP2000. Linear and non-linear analyses of the beam under increasing uniformly distributed loads are also carried out. In addition to box-girder beams, the proposed element can also be used in modelling open-section beams with curved or straight axes and circular plates under radial compression. Buckling loads of a circular plate example are obtained for coarse and successively refined meshes and results are compared with each other. The advantage of this element is that curved systems can be realistically modelled and satisfactory results can be obtained even by using coarse meshes.

Effect of cylinder aspect ratio on wake structure behind a finite circular cylinder located in an atmospheric boundary layer (대기경계층 내에 놓인 자유단 원주의 형상비가 후류유동에 미치는 영향에 관한 연구)

  • Park, Cheol-Woo;Lee, Sang-Joon
    • Proceedings of the KSME Conference
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    • 2001.06e
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    • pp.247-252
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    • 2001
  • The flow around free end of a finite circular cylinder(FC) embedded in an atmospheric boundary layer has been investigated experimentally. The experiments were carried out in a closed-return type subsonic wind tunnel with varying aspect ratio of the finite cylinder mounted vertically on a flat plate. The wake structures behind a 2-D cylinder and a finite cylinder located in a uniform flow were also measured for comparison. Reynolds number based on the cylinder diameter was about Re=20,000. A hot-wire anemometer was employed to measure the wake velocity and the mean pressure distributions on the cylinder surface were also measured. The flow past the FC free end shows a complicated three-dimensional wake structure and flow phenomenon is quite different from that of 2-D cylinder. The three-dimensional flow structure was attributed to the downwashing counter rotating vortices separated from the FC free end. As the FC aspect ratio decreases, the vortex shedding frequency is decreased and the vortex formation length is increased compared to that of 2-D cylinder. Due to the descending counter-rotating twin-vortex, in the region near the FC free end, regular vortex shedding from the cylinder is suppressed and the vortex formation region is hardly established. In the wake center region, the mean velocity for the FC located in atmospheric boundary layer has large velocity deficit, compared to that of uniform flow.

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Characteristics of Vertical Stress Distribution in Sandy Soil According to the Relative Compaction and Composition of the Soil Layer (사질토 지반의 상대다짐도 및 토층에 따른 연직지중응력 분포 특성)

  • Nam, Hyo-Seok;Lee, Sang-Ho
    • Journal of The Korean Society of Agricultural Engineers
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    • v.52 no.2
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    • pp.43-50
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    • 2010
  • This study was carried out to evaluate the vertical stress properties in sandy soil according to changes of foundation condition in soil bin compacted three layers. The following conclusions and comparisons have been made based on careful analysis from theoretical and experimental methods. : When sandy soil subjected to circular uniform load, the vertical stress increments ($\Delta\sigma_z$) was increased as load increasing, the maximum values of $\Delta\sigma_z$ was achieved at the point loading axis, and $\Delta\sigma_z$ was not shown over at a distance of three times of loading plate width (B). The vertical stress increments were achieved largely at 80 % relative compaction (Rc) compared to 95 % relative compaction due to stress concentration in sandy soil. When sandy soil subjected to circular uniform load, the $\Delta\sigma_z$ differences between theoretical and experimental values as load increased were more increased and its maximum differences were achieved at stress axis. When gravel surface macadamized over sandy soil subjected to load, the $\Delta\sigma_z$ was concentrated to load axis as load increasing, so that macadamization will be decreased load transmission.

Study on velocity profiles around spiral baffle plates in a horizontal circular tube without inner tubes

  • Chang, Tae-Hyun;Lee, Kwon-Soo;Choi, Yoon-Hwan;Lee, Yeon-Won
    • Journal of Advanced Marine Engineering and Technology
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    • v.40 no.5
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    • pp.403-411
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    • 2016
  • Usually shell and tube heat exchangers are employed to recover energy between fluids. Recently, numerous papers on these heat exchangers have been published; however, the velocity and temperature profiles or comparison of the features of the flow with or without inside tubes have rarely been described. In this research, experimental and numerical studies were carried out to investigate the characteristics of the flow around the spiral baffle plates without inside tubes in a horizontal circular tube using a particle image velocimetry method and ANSYS 14.0~15.0 version (Fluent). The results showed that swirling flow was produced between the spiral baffle plates. The tangential components were strong between the two spiral baffles; however, the axial or radial velocities components were indicating nearly zero. From the spiral motion in the space of the two baffles, it is considered that there were no dead zones between the spiral baffle.

A Study of Car Plate Recognition System on The Park (주차장 자동차번호 인식 시스템에 관한 연구)

  • 신강호
    • Journal of the Korea Society of Computer and Information
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    • v.8 no.4
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    • pp.87-91
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    • 2003
  • In this paper, a rotation invariant fingerprint identification system is implemented using the circular harmonic filter and phase only correlator. We extracted the phase component from input fingerprint image and correlate it with the circular harmonic filter of the reference fingerprint image by POC. The input image is obtained using a prism operating in the internal full reflection mode. Then the input image is transformed to two dimensional Fourier spectrum in optical way and the phase component is extracted using a digital system from the spectrum. Because composed of the optical system and digital algorithm, the proposed system has the advantages of the two technologies such as realtime parallel processing property of the optics and the flexibility of the digital system.

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Effect of Nozzle Configuration and Impinging Surface on the Impinging Tone Generation by Circular Jets (충돌면과 노즐의 형상이 원형충돌제트에 의한 충돌순음 발생에 미치는 영향)

  • Im, Jung-Bin;Kwon, Young-Pil
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.27 no.6
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    • pp.693-700
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    • 2003
  • The effect of the configuration of the nozzle and the impinging surface on the characteristics of the hole-tones has been experimentally investigated. It is found that the plate-tone is a special case of hole-tones, where the hole diameter is zero. The jet velocity range for hole-tones is divided into the low velocity region associated with laminar jet and the high velocity region with turbulent jet. The frequency of the tone is that for the shear layer instability at the nozzle exit or that attainable by a cascade of vortex pairing process with increase of the impinging distance. When the distance is longer than one diameter the frequency decreases to the terminal value near the preferred frequency of the column mode instability, in the range 0.23< $St_d$<0.53, where $St_d$ is the Strouhal number defined by $fd/U_J$, f the frequency, d the nozzle diameter, and $U_J$ the exit velocity. While the convection speed of the downstream vortex, in the present study, is almost constant at low-speed laminar jet, it increases with distance at high-speed turbulent jet. As the frequency increases, the convection speed decreases in the low frequency range corresponding to the preferred mode, in agreement with the existing experimental data for a free jet.

A study on fluid flow and heat transfer around the circular cylinder located on a flat plate in crossflow (횡단류 내 평판 위에 놓인 원형 실린더 주위의 유동장 및 열전달에 관한 연구)

  • Lee, Gi-Baek;Son, Jeong-Ho;Yang, Jang-Sik
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.20 no.4
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    • pp.1458-1471
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    • 1996
  • The present study is concerned with the heat transfer enhancement associated with a symmetrical or asymmetrical horseshoe vortex in front of and around the circular cylinder centered between the side walls of a wind tunnel. The static pressure measurements and the flow visualization in front of and around cylinders have been performed to determine the existence of horseshoe vortex. The hue-capturing method using the thermochromatic liquid crystals with great spatial resolution was used to obtain the local information of the endwall heat transfer coefficients. In case of one cylinder, the convective heat transfer coefficients of the region where the horseshoe vortex exists are larger than those of any other region. In case of two cylinders with tandem arrangement, the heat transfer rate of gap spacing (d/D= 1.5) is higher than that of gap spacings (d/D=2.0 or 2.5).