• Tribology and Lubricants
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• 제34권1호
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• pp.16-22
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• 2018

Cylindrical turbine guide bearings (TGBs) with simple plain pads have conventionally been used in vertical hydro-power turbine-generator applications in order to provide turbine runner shafts with smooth rotation guides and supports. To overcome low-load/low-eccentricity performance drawbacks, such as very low film stiffness and lack of design credibility in the stiffness values themselves, of conventional cylindrical TGBs, the introduction of a rotational-directional leading-edge taper to each partitioned pad, simply pad leading-edge taper, has been found to be very effective in enhancing their design-application availability and usefulness. In this study, we investigate the effects of taper angle and length for given taper heights in detail in order to systematically establish the effectiveness of design on the performance improvement of vertical hydro-power application cylindrical TGBs with pad leading-edge tapers. The analysis results with $4-Pad{\times}1-Row$ cylindrical TGBs show that the lubrication performance of the cylindrical TGBs is optimized with an approximate taper angle ratio of 0.8 and taper length ratio of 0.9. We conclude that the introduction of pad leading-edge tapers along with the optimization of taper designs can be very effective in improving the overall operation reliability of cylindrical TGBs and the rotordynamic characteristics of vertical hydro-power turbine-generator rotor-bearing systems as well, to which the TGBs are applied.

• 한국광학회지
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• 제16권3호
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• pp.177-181
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• 2005

원통형 물체의 지름을 측정하는 방법에는 여러 가지가 있지만 본 연구에서는 두 가지 비접촉식 방법인 기하광학적 방법과 간섭${\cdot}$회절 방법으로 원통형 물체의 지름을 측정하였다. 기하광학적인 방법은 원통형 렌즈를 이용하여 기울인 레이저 광선을 원통형 물체의 옆면에 비추어 나타나는 곡선을 CCD 카메라로 포착하고 이 곡선을 기하학적인 방법으로 계산하는 것이며 간섭${\cdot} $회절에 의한 방법은 스크린에 나타난 물체에 의한 레이저광의 간섭${\cdot}$회절무늬를 측정하고 분석하는 방법이다. 버니어 캘리퍼스로 측정한 평균 지름이 $0.05\;mm\;\~\;100.50\;mm$ 인 원통형 물체를 기하광학적 방법과 간섭${\cdot}$회절 방법으로 측정한 결과 각각의 상대오차가 $2\%$ 와 $1\%$범위 이내였고 다량의 물체 지름을 신속히 측정하는데 응용될 수 있음을 확인하였다.

• Structural Engineering and Mechanics
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• 제87권5호
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• pp.461-473
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• 2023

This study aims to solve for nonlinear cylindrical shell systems with a semi-analytical and numerical approach implementing the P-T method. The procedures and conditions for such a study are presented in practically solving and analyzing the cylindrical shell systems. An analytical model for a nonlinear thick cylindrical shell (TCS) is established on the basis of the stress function and Reddy's higher-order shear deformation theory (HSDT). According to Reddy's HSDT, Hooke's law in three dimensions, and the von-Kármán equation, the stress-strain relations are developed for the thick cylindrical shell systems, and the three coupled nonlinear governing equations are thus established and discretized as per the Galerkin method, for implementing the P-T method. The solution generated with the approach is continuous everywhere in the entire time domain considered. The approach proposed can also be used to numerically solve and analyze the nonlinear shell systems. The procedures and recurrence relations for numerical solutions of shell systems are presented. To demonstrate the application of the approach in numerically solving for nonlinear cylindrical shell systems, a specific nonlinear cylindrical shell system subjected to an external excitation is solved numerically. In numerically solving for the system, the present approach shows higher efficiency, accuracy, and reliability in comparison with that of the Runge-Kutta method. The approach with the P-T method presented is practically sound especially when continuous and high-quality numerical solutions for the shell systems are considered.

• Journal of applied mathematics & informatics
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• 제5권3호
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• pp.811-818
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• 1998

A cylindrical elastic layer in finite deformation s con-sidered. The characteristics of the linear longitudinal wave and the nonlinear shear wave are investigated; the dependence of the later on the parameter of large deformation is given.

• Nonlinear Functional Analysis and Applications
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• 제28권4호
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• pp.1005-1015
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• 2023

In this paper, we establish the existence of at least two distinct solutions to a p-Laplacian problems involving critical exponents and singular cylindrical potential, by using the Nehari manifold.

• Structural Engineering and Mechanics
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• 제24권4호
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• pp.395-410
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• 2006

This paper reports the result of an investigation into wave propagation in orthotropic laminated piezoelectric cylindrical shells in hydrothermal environment. A dynamic model of laminated piezoelectric cylindrical shell is derived based on Cooper-Naghdi shell theory considering the effects of transverse shear and rotary inertia. The wave characteristics curves are obtained by solving an eigenvalue problem. The effects of layer numbers, thickness of piezoelectric layers, thermal loads and humid loads on the wave characteristics curves are discussed through numerical results. The solving method presented in the paper is validated by the solution of a classical elastic shell non-containing the effects of transverse shear and rotary inertia. The new features of the wave propagation in laminated piezoelectric cylindrical shells with various laminated material, layer numbers and thickness in hydrothermal environment and some meaningful and interesting results in this paper are helpful for the application and the design of the ultrasonic inspection techniques and structural health monitoring.

• Steel and Composite Structures
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• 제27권1호
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• pp.35-48
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• 2018

In this paper, the response of a sandwich cylindrical shell over any sort of boundary conditions and under a general distributed static loading is investigated. The faces and the core are made of some isotropic materials. The faces are modeled as thin cylindrical shells obeying the Kirchhoff-Love assumptions. For the core material it is assumed to be thick and the in-plane stresses are negligible. The governing equations are derived using the principle of the stationary potential energy. Using harmonic differential quadrature method (HDQM) the equations are solved for deformation components. The obtained results primarily are compared against finite element results. Then, the effects of changing different parameters on the stress and displacement components of sandwich cylindrical shells are investigated.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 춘계학술발표대회 논문집
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• pp.131-134
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• 2002

Supersonic flutter analysis of cylindrical composite panels with structural damping treatments has been performed using the finite element method based on the layerwise shell theory. The natural frequencies and loss factors of cylindrical viscoelastic composites are computed considering the effects of transversely shear deformation. The panel flutter of cylindrical composite panels is analyzed considering structural damping effect. Various damping characteristics for unconstrained layer damping, constrained layer damping, and symmetrically co-cured sandwich laminates are compared with those of an original base panel in view of aeroelastic stabilities.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 춘계학술발표대회 논문집
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• pp.29-32
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• 2005

Based on the full layerwise displacement shell theory, vibration and damping characteristics of cylindrical sandwich panels are investigated. The transverse shear deformation and the normal strain are fully taken into account for structural damping modelling. Modal damping factors and frequency response functions are analyzed for various structural parameters of cylindrical sandwich beams. Present results shows that full layerwise theory can accurately predict vibration and damping characteristics of cylindrical composite panels with surface damping treatments and constrained layer damping. The viscoelastic materials depending on elevated temperature environment and exciting frequencies can be fully considered.

• 한국소음진동공학회논문집
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• 제25권1호
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• pp.33-39
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• 2015

This paper investigates the underwater acoustic radiation from a periodically stiffened cylindrical shell excited resiliently mounted machinery. Underwater acoustic radiation is important to a submarine. Generally, submarine structure can be modeled as stiffened cylindrical shell immersed in water. Analytical model is derived for the far-field acoustic radiation from machinery installed inside cylindrical shell. The analytical model includes the effect of fluid loading and interactions between periodic ring stiffeners. Transmitted force from machine to a shell through isolator can be different by the impedance of shell. In this paper the effect of a shell impedance for acoustic radiation is investigated. Impedance of a shell should be considered if thickness of a shell is thin.