• Title/Summary/Keyword: Elliptical

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Vibration frequencies for elliptical and semi-elliptical Mindlin plates

  • Wang, C.M.;Xiang, Y.;Kitipornchai, S.
    • Structural Engineering and Mechanics
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    • v.3 no.1
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    • pp.35-48
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    • 1995
  • This paper presents new frequency results for elliptical and semi-elliptical Mindlin plates of various aspect ratios, thicknesses and boundary conditions. The results were obtained using the recently developed computerized Rayleigh-Ritz method for thick plate analysis. For simply supported elliptical plates, it is proposed that the penalty function method be used to enforce the condition of zero rotation of the midplane normal in the tangent plane to the plate boundary.

Study on Process Monitoring of Elliptical Vibration Cutting by Utilizing Internal Data in Ultrasonic Elliptical Vibration Device

  • Jung, Hongjin;Hayasaka, Takehiro;Shamoto, Eiji
    • International Journal of Precision Engineering and Manufacturing-Green Technology
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    • v.5 no.5
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    • pp.571-581
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    • 2018
  • In the present study, monitoring of elliptical vibration cutting process by utilizing internal data in the ultrasonic elliptical vibration device without external sensors such as a dynamometer and displacement sensor is investigated. The internal data utilized here is the change of excitation frequency, i.e. resonant frequency of the device, voltages applied to the piezoelectric actuators composing the device, and electric currents flowing through the actuators. These internal data change automatically in the elliptical vibration control system in order to keep a constant elliptical vibration against the change of the cutting process. Correlativity between the process and the internal data is described by using a vibration model of ultrasonic elliptical vibration cutting and verified by several experiments, i.e. planing and mirror surface finishing of hardened die steel carried out with single crystalline diamond tools. As a result, it is proved that it is possible to estimate the elements of elliptical vibration cutting process, e.g. tool wear and machining load, which are important for stable cutting in such precision machining.

Compensating the Elliptical Trajectory of Elliptical Vibration Cutting Device (타원궤적 진동절삭기의 타원궤적 보정)

  • Loh, Byoung-Gook;Kim, Gi-Dae
    • Journal of the Korean Society for Precision Engineering
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    • v.28 no.7
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    • pp.789-795
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    • 2011
  • In elliptical vibration cutting (EVC), cutting performance is largely affected by the shape of an elliptical path of the cutting tool. In this study, two parallel piezoelectric actuators were used to make an elliptical vibration cutting device. When harmonic voltages of $90^{\circ}$ out-of-phase are supplied to the EVC device, creation of an ideal elliptical trajectory whose major and minor axes are parallel to the cutting and thrust directions is anticipated from a kinematic analysis of the EVC device, however, the paths we experimentally observed showed significant distortions in its shape ranging from skew to excessive elongation of the major axis of the ellipse. To compensate distortions, an analytical model describing the elliptical path of the cutting tool was developed and verified with experimental results, and based on the analytical model, the distorted elliptical paths created at 100 Hz, 1 kHz, and 16 kHz were corrected for skew and elongation.

Effect of Flow Structure Inside Nozzle on the Liquid Jet Breakup of Elliptical Nozzle (타원형 노즐의 내부유동 구조가 액주분열에 미치는 영향)

  • Ku, K.W.;Hong, J.G.
    • Journal of ILASS-Korea
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    • v.18 no.1
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    • pp.44-54
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    • 2013
  • An experimental study was performed to investigate the liquid jet breakup of a circular nozzle and elliptical nozzles. Furthermore Numerical simulation was attempted to investigate the internal flow structure in the circular and elliptical nozzles. This study showed that the disintegration characteristics of the liquid jet of elliptical nozzles were much different from those of the circular nozzle. The liquid jet issued from the elliptical nozzles became more unstable at the same injection pressure. Surface breakup was observed at the jet issued from the elliptical nozzles with the increase of injection pressure. The disintegration of the liquid jet of elliptical nozzles was related with the internal flow structure which is revealed from the numerical simulation.

Stress Intensity Factor Analysis of Elliptical Arc Through Cracks at Mechanical Fastener Holes by Weight Function Method ( I ) - Development of Weight Function Method - (가중함수법에 의한 기계적 체결홀에 존재하는 타원호형 관통균열의 음력확대계수 해석 ( I ) - 가중함수법의 전개 -)

  • Heo, Seong-Pil;Yang, Won-Ho;Hyeon, Cheol-Seung
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.25 no.10
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    • pp.1659-1670
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    • 2001
  • It has been reported that cracks at mechanical fastener holes usually nucleate as elliptical corner cracks at the faying surface of the mechanical joints and grow as elliptical arc through cracks after penetrating the opposite surface. The weight function method is an efficient technique to calculate the stress intensity factors fur elliptical cracks using uncracked stress field. In this study the weight function method for three dimensional mixed-mode problem applied to elliptical comer cracks Is modified for elliptical arc through cracks and the stress intensity factors at two surface points of elliptical arc through cracks at mechanical fastener holes are analyzed by the weight function method. This study consists of two parts and in part I , the weight function method for elliptical arc through cracks is developed and verified.

Determination of Stress Intensity Factors for Embedded Elliptical Crack in Turbine Rotor (터빈축차내에 내재된 타원균열의 응력세기계수 결정)

  • 이강용;김종성;하정수
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.5
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    • pp.1229-1242
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    • 1995
  • The thermal shock stress intensity factors of semi-elliptical surface crack in finite plate and the stress intensity fractors of embedded elliptical crack in turbine rotor is determined by means of Vainshtok weight function method. In case of semi-elliptical surface crack, the solution is compared with previous solution. The stress intensity factor for embedded elliptical crack in turbine rotor loaded by centrifugal and thermal loading is also determined. In this case, the value of stress intensity factor is larger at crack contour near internal radius surface and is almost constant at the crack contour farther from internal radius surface.

On Perturbed Symmetric Distributions Associated with the Truncated Bivariate Elliptical Models

  • Kim, Hea-Jung
    • Communications for Statistical Applications and Methods
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    • v.15 no.4
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    • pp.483-496
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    • 2008
  • This paper proposes a class of perturbed symmetric distributions associated with the bivariate elliptically symmetric(or simply bivariate elliptical) distributions. The class is obtained from the nontruncated marginals of the truncated bivariate elliptical distributions. This family of distributions strictly includes some univariate symmetric distributions, but with extra parameters to regulate the perturbation of the symmetry. The moment generating function of a random variable with the distribution is obtained and some properties of the distribution are also studied. These developments are followed by practical examples.

PHOTOMETRIC EVOLUTION OF ELLIPTICAL GALAXIES

  • JUNG HEE;LEE SEE-WOO
    • Journal of The Korean Astronomical Society
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    • v.27 no.2
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    • pp.177-190
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    • 1994
  • We have examined the photometric evolution of elliptical galaxies, using stellar evolutionary models covering the wide ranges of metallicity and mass, and the different IMFs (simple IMP & time-dependent bimodal IMF). The model with a time-dependent bimodal IMF can reproduce the observed integrated magnitudes and colors at all wavelengths. The computed model shows that the star formation in elliptical galaxies is still going on, although the number of newly born stars is very small. The chemical evolutionary effect is clearly seen in the C-M diagram of computed elliptical galaxies.

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