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.

Vibration and Sound Radiation from Plates Excited by Piezoelectric Actuators

Abstract: Theoretical analysis of the vibration of plates excited by piezoelectric actuators is presented in this paper. The geometric non-linear finite element model and the loading model of the piezoelectric actuators were developed for non-linear analysis. It is found that non-linear analysis is more accurate than linear analysis for large displacement vibration. A comparison of the results of the numerical model with experiment results shows that the numerical model and the computer program are correct. The vibration excited by piezoelectric actuators is also compared with the sound radiation generated by actuators.

Thermal Buckling Suppression of Supersonic Vehicle Surface Panels Using Shape Memory Alloy

Abstract: An efficient finite element method for the prediction of critical temperature, postbuckling deflection, and vibration characteristics is presented for traditional composite plates embedded with prestrained shape memory alloy (SMA) wires. The temperature-dependent material properties of SMA and composites and the large deflections are considered in the formulation. An iterative eigensolution is presented to determine the critical temperature, the Newton-Raphson method is employed to obtain postbuckling large deflection, and the eigensolver is used to predict free vibration frequencies about the thermally buckled equilibrium positions. Results show that the critical buckling temperature can be raised high enough and that the postbuckling deflection can be completely suppressed for surface panels of supersonic vehicle applications by the proper selection of SMA volume fraction, prestrain, and alloy composition. Weight savings based on critical temperature in the use of SMA as compared with the traditional composite and titanium plates are demonstrated.

Convergence Study of Minimizing the Nonconvex Total Delay Using the Lane-Based Optimization Method for Signal-Controlled Junctions

Abstract: This paper presents a 2D convergence density criterion for minimizing the total junction delay at isolated junctions in the lane-based optimization framework. The lane-based method integrates the design of lane markings and signal settings for traffic movements in a unified framework. The problem of delay minimization is formulated as a Binary Mix Integer Non Linear Program (BMINLP). A cutting plane algorithm can be applied to solve this difficult BMINLP problem by adding hyperplanes sequentially until sufficient numbers of planes are created in the form of solution constraints to replicate the original nonlinear surface in the solution space. A set of constraints is set up to ensure the feasibility and safety of the resultant optimized lane markings and signal settings. The main difficulty to solve this high-dimension nonlinear nonconvex delay minimization problem using cutting plane algorithm is the requirement of substantial computational efforts to reach a good-quality solution while approximating the nonlinear solution space. A new stopping criterion is proposed by monitoring a 2D convergence density to obtain a converged solution. A numerical example is given to demonstrate the effectiveness of the proposed methodology. The cutting-plane algorithm producing an effective signal design will become more computationally attractive with adopting the proposed stopping criterion.

Structural Vibration Suppression Using the Piezoelectric Sensors and Actuators

Abstract: An experimental study for the active vibration control of structures subject to external excitations using piezoelectric sensors and actuators is presented. A simply supported plate and a curved panel are used as the controlled structures in two experiments, respectively. The Independent Modal Space Control (IMSC) approach is employed for the controller design. In order to increase the adaptability, the time-domain modal identification technique is incorporated into the controller to real-time update the system parameters. The adaptive effectiveness of the time-domain modal identification technique is tested by fixing an additional mass on the simply supported plate to change its structural properties. The vibration suppression performances of the controller are 5.7 dB and 10.8 dB for the simply-supported plate with/without the mass subject to a chirp sine excitation, respectively. For the experiment of the curved panel subject to a sinusoidal excitation, the vibration attenuation of the control scheme is 5.0 dB even the control circuit is subject to some noise generated by electrical and magnetic interferences.

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.