Yiu-Yin Lee

Bio: Yiu-Yin Lee is an academic researcher from City University of Hong Kong. The author has contributed to research in topics: Vibration & Nonlinear system. The author has an hindex of 21, co-authored 92 publications receiving 1727 citations. Previous affiliations of Yiu-Yin Lee include Hong Kong Polytechnic University & Old Dominion University.

Flow Angle, Temperature, and Aerodynamic Damping on Supersonic Panel Flutter Stability Boundary

Abstract: The effects of flow yaw angle, temperature, and aerodynamic damping on supersonic flutter of plates are investigated. Quasisteady, first-order piston theory is employed for formulation of aerodynamic forces. The von Karman large-deflection plate theory is adapted for the aerothermal deflection. Two types of thermal effects are considered: 1) plate expansion by uniform temperature and 2) thermal moment induced by temperature gradient across the plate thickness. A finite element modal formulation and a two-step procedure are presented for the predictions of stability boundaries and nonlinear aerothermal deflection and shown to be efficient in solution. Results have shown that flow angle has lesser effect on stability boundaries as compared with temperature for isotropic square plates. However, both flow angle and temperature have a large influence on stability boundaries for rectangular isotropic and laminated composite plates. The presence of the ripple characteristics of stability boundaries for composite plates caused by the frequency coalescence of higher modes and the smaller effect of aerodynamic damping is investigated. The stabilization effects on panel motions induced by variations of flow angle, temperature, and aerodynamic damping are discussed.

The multi-level residue harmonic balance solutions of multi-mode nonlinearly vibrating beams on an elastic foundation

Abstract: In this paper, an efficient analytical solution method, namely, multi-level residue harmonic balance, is introduced and developed for the nonlinear vibrations of multi-mode flexible beams on an elastic foundation subject to external harmonic excitation. The main advantage of this solution method is that only one set of nonlinear algebraic equations is generated in the zero level solution procedure while the higher level solutions for any desired accuracy can be obtained by solving a set of linear algebraic equations. In other words, the computation effort to find more accurate nonlinear solutions is much less. In this paper, a multi-mode formulation, which represents the nonlinear beam vibration, is derived and set up. Then, the solution procedures are developed for obtaining the nonlinear multi-mode solution. The results from the multi-level residue harmonic balance method agree well with those from a numerical integration method. The effects of various parameters such as vibration amplitude, foundation ...

Introduction to the Finite Element Method

Abstract: This chapter introduces the finite element method (FEM) as a tool for solution of classical electromagnetic problems. Although we discuss the main points in the application of the finite element method to electromagnetic design, including formulation and implementation, those who seek deeper understanding of the finite element method should consult some of the works listed in the bibliography section.

Vibration of nonlocal Timoshenko beams

Abstract: This paper is concerned with the free vibration problem for micro/nanobeams modelled after Eringen's nonlocal elasticity theory and Timoshenko beam theory. The small scale effect is taken into consideration in the former theory while the effects of transverse shear deformation and rotary inertia are accounted for in the latter theory. The governing equations and the boundary conditions are derived using Hamilton's principle. These equations are solved analytically for the vibration frequencies of beams with various end conditions. The vibration solutions obtained provide a better representation of the vibration behaviour of short, stubby, micro/nanobeams where the effects of small scale, transverse shear deformation and rotary inertia are significant. The exact vibration solutions should serve as benchmark results for verifying numerically obtained solutions based on other beam models and solution techniques.

An efficient and simple higher order shear and normal deformation theory for functionally graded material (FGM) plates

Abstract: In this paper, an efficient and simple higher order shear and normal deformation theory is presented for functionally graded material (FGM) plates. By dividing the transverse displacement into bending, shear and thickness stretching parts, the number of unknowns and governing equations for the present theory is reduced, significantly facilitating engineering analysis. Indeed, the number of unknown functions involved in the present theory is only five, as opposed to six or even greater numbers in the case of other shear and normal deformation theories. The present theory accounts for both shear deformation and thickness stretching effects by a hyperbolic variation of all displacements across the thickness, and satisfies the stress-free boundary conditions on the upper and lower surfaces of the plate without requiring any shear correction factor. Equations of motion are derived from Hamilton’s principle. Analytical solutions for the bending and free vibration analysis are obtained for simply supported plates. The obtained results are compared with 3-dimensional and quasi-3-dimensional solutions and those predicted by other plate theories. It can be concluded that the present theory is not only accurate but also simple in predicting the bending and free vibration responses of functionally graded plates.