• Smart Structures and Systems
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• 제16권5호
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• pp.853-872
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• 2015

Numerical analysis of large amplitude free vibration behaviour of laminated composite spherical shell panel embedded with the piezoelectric layer is presented in this article. For the investigation purpose, a general nonlinear mathematical model has been developed using higher order shear deformation mid-plane kinematics and Green-Lagrange nonlinearity. In addition, all the nonlinear higher order terms are included in the present mathematical model to achieve any general case. The nonlinear governing equation of freely vibrated shell panel is obtained using Hamilton's principle and discretised using isoparametric finite element steps. The desired nonlinear solutions are computed numerically through a direct iterative method. The validity of present nonlinear model has been checked by comparing the responses to those available published literature. In order to examine the efficacy and applicability of the present developed model, few numerical examples are solved for different geometrical parameters (fibre orientation, thickness ratio, aspect ratio, curvature ratio, support conditions and amplitude ratio) with and/or without piezo embedded layers and discussed in details.

• 대한조선학회논문집
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• 제42권2호
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• pp.113-123
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• 2005

A higher order panel method based on B-spline representation for both the geometry and the solution is developed for the analysis of steady flow around marine propellers. The self-influence functions due to the normal dipole and the source are desingularized through the quadratic transformation, and then shown to be evaluated using conventional numerical quadrature. By selecting a proper order for numerical quadrature, the accuracy of the present method can be increased to the machine limit. The far- and near-field influences are shown to be evaluated based on the same far-field approximation, but the near-field solution requires subdividing the panels into smaller subpanels continuously, which can be effectively implemented due to the B-spline representation of the geometry. A null pressure jump Kutta condition at the trailing edge is found to be effective in stabilizing the solution process and in predicting the correct solution. Numerical experiments indicate that the present method is robust and predicts the pressure distribution on the blade surface, including very close to the tip and trailing edge regions, with far fewer panels than existing low order panel methods.

• Steel and Composite Structures
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• 제28권1호
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• pp.25-37
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• 2018

For the first time, the parametric instability characteristics of tow-steered variable stiffness composite laminated (VSCL) cylindrical panels is investigated using B-spline finite strip method (FSM). The panel is considered containing geometrical defects including cutout and delamination. The material properties are assumed to vary along the panel axial length of any lamina according to a linear fiber-orientation variation. A uniformly distributed inplane longitudinal loading varies harmoni-cally with time is considered. The instability load frequency regions corresponding to the assumed in-plane parametric load-ing is derived using the Bolotin's first order approximation through an energy approach. In order to demonstrate the capabili-ties of the developed formulation in predicting stability behavior of the thin-walled VSCL structures, some representative results are obtained and compared with those in the literature wherever available. It is shown that the B-spline FSM is a proper tool for extracting the stability boundaries of perforated delaminated VSCL panels.

• Advances in aircraft and spacecraft science
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• 제5권1호
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• pp.21-49
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• 2018

In this paper, geometric nonlinear bending characteristics of single wall carbon nanotube reinforced composite (SWCNTRC) doubly curved shell panels subjected to uniform transversely loadings are investigated. The nonlinear mathematical model is developed for doubly curved SWCNTRC shell panel on the basis of higher-order shear deformation theory and Green- Lagrange nonlinearity. All nonlinear higher order terms are included in the mathematical model. The effective material properties of SWCNTRC are estimated by using Eshelby-Mori-Tanaka micromechanical approach. The governing equation of the shell panel is obtained using the total potential energy principle and a Newton-Raphson iterative method is employed to compute the nonlinear displacement and stresses. The present results are compared with published literature. The effect of SWCNT volume fraction, width-to-thickness ratio, radius-to-width ratio (R/a), boundary condition, linear and nonlinear deflection, stresses and different types of shell geometry on nonlinear bending response is investigated.

• 대한조선학회논문집
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• 제38권3호
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• pp.31-40
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• 2001

일반적으로 특이점들을 분포하여 물체주위 유동장을 해석할 때 저차패널법(Low-Order Panel Method)이 유용하게 사용되어져 왔다. 저차패널법과는 다르게 적분방정식의 계산정도와 해의 수렴성을 높일 수 있는 방법으로서, 물체경계의 형상을 2차 이상의 고차곡면요소로 표현하고 각 곡면요소 내에서 물리량의 변화를 동일한 차수를 갖는 고차경계요소법을 사용할 수 있다. 본 연구에서는 물체표면의 곡면요소와 물리량의 변화를 9절점 라그란지안(Lagrangian) 형상함수를 사용하여 정상 포텐셜유동 중에 작동하는 프로펠러 주위의 유동을 해석하였다. 개발된 프로그램을 프로펠러의 해석에 앞서 원형 날개에 대하여 Jordan의 선형 해석해와 비교하였으며, 두께의 영향을 관찰하였다. 프로펠러의 해석을 위해 DTRC 4119 프로펠러와 DTRC 4842 프로펠러에 적용하여 실험치와 계산치를 비교 검토하였다.

• Steel and Composite Structures
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• 제16권4호
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• pp.389-415
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• 2014

This study deals with dynamic model of composite sandwich panels with functionally graded flexible cores under low velocity impacts of multiple large or small masses using a new improved higher order sandwich panel theory (IHSAPT). In-plane stresses were considered for the functionally graded core and face sheets. The formulation was based on the first order shear deformation theory for the composite face sheets and polynomial description of the displacement fields in the core that was based on the second Frostig's model. Fully dynamic effects of the functionally graded core and face-sheets were considered in this study. Impacts were assumed to occur simultaneously and normally over the top and/or bottom of the face-sheets with arbitrary different masses and initial velocities. The contact forces between the panel and impactors were treated as internal forces of the system. Nonlinear contact stiffness was linearized with a newly presented improved analytical method in this paper. The results were validated by comparing the analytical, numerical and experimental results published in the latest literature.

• 대한조선학회논문집
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• 제37권2호
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• pp.57-69
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• 2000

기하학적 형상과 유동의 해를 B-스플라인으로 표현하는 3차원 고차 패널법은 프로펠러 주위의 유동을 해석하기 위해 개발되었다. 제어점이 패널내에 놓이는 경우, 고차의 다이폴과 쏘오스에 의해 유기되는 자기 유기 포텐셜의 특이 거동은 2차 변환(quadratic transformation)을 통하여 제거하였으며, 특이 부분은 해석적인 적분으로 비특이 부분은 정도 높은 Gauss 구적법으로 계산함으로써 유기 포텐셜을 정도 높게 구할 수 있음을 보였다. 또한, 날개 뒷날에서의 압력 점프의 값이 명시적으로 영이 되도록하는 동역학적 Kutta 조건식을 도입하고, 이의 적용이 안정된 해를 보장함을 확인하였다. 수치 실험을 통하여, 제안된 수치해석 기법이 안정적이고 정확한 해를 줌을 확인하였으며, 특히 저차 패널법과 비교하여 적은 수의 패널로 동일한 정도의 해를 유지할 수 있음을 보였다.

• 대한조선학회논문집
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• 제36권4호
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• pp.9-20
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• 1999

기하학적 형상과 유동의 해를 B-스플라인으로 표현하는 2차원 고차 패널법이 개발되어 수중익 문제의 해석에 적용되었다. 제어점이 패널내에 놓이는 경우, 고차의 다이폴과 쏘오스에 의해 유기되는 자기 유기 포텐셜의 특이 거동을 제거하기 위하여 피적분 함수를 특이 부분과 비특이 부분으로 나누어, 특이 부분을 해석적인 적분으로 비특이 부분은 정도 높은 Gauss 구적법으로 계산함으로써 유기 포텐셜을 정도 높게 구할 수 있음을 보였다. 또한, 날개 뒷날에서의 압력 점프의 값이 명시적으로 영이 되도록하는 동역학적 Kutta 조건식을 도입하고, 이의 적용이 안정된 해를 보장함을 확인하였다. 수치 실험을 통하여, 제안된 수치해석 기법이 안정적이고 정확한 해를 줌을 확인하였으며, 특히 저차 패널법과 비교하여 적은 수의 패널로 동일한 정도를 유지할 수 있음을 보였다.

• 대한조선학회논문집
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• 제47권3호
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• pp.398-409
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• 2010

This paper considers the numerical computation of added resistance on ships in the presence of incident waves. As a method of solution, a higher-order Rankine panel method is applied in time domain. The added resistance is evaluated by integrating the second-order pressure on the body surface. Computational results are validated by comparing with experimental data and other computational results on a hemi-sphere, a barge, Wigley hull models, and Series 60 hull, showing very fair agreements. The study is extended to the comparison between Neumann-Kelvin and double-body linearization approaches, and their differences are discussed.

• 대한조선학회논문집
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• 제47권3호
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• pp.306-320
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• 2010

Modern ultra-large container carriers can be exposed to the unprecedented springing excitation from ocean waves due to their relatively low torsional rigidity. Large deck opening on the deck of container carriers tends to cause warping distortion of hull structure under wave-induced excitation, eventually leading to the higher chance of resonance vibration between its torsional response and incoming waves. To handle this problem, a higher-order B-spline Rankine panel method and Vlasov-beam FE model was directly coupled in the time domain, and the coupled equation was solved by using an implicit iterative method. In order to capture the complicated behavior of thin-walled open section girder, a sophisticated beam-based finite element model was developed, which takes into account warping distortion and shear-on-wall effect. Then, the developed beam model was directly coupled with the time-domain Rankine panel method for hydrodynamic problem by using the fixed-point iteration method. The developed computational scheme was validated through the comparison with the frequency-domain solution on the container carrier model in linear springing regime.