Taihong Cheng

Vibration and Damping Analysis of Composite Fiber Reinforced Wind Blade with Viscoelastic Damping Control

Composite materials are increasingly used in wind blade because of their superior mechanical properties such as high strength-to-weight and stiffness-to-weight ratio. This paper presents vibration and damping analysis of fiberreinforced composite wind turbine blade with viscoelastic damping treatment. The finite element method based on full layerwise displacement theory was employed to analyze the damping, natural frequency, and modal loss factor of composite shell structure. The lamination angle was considered in mathematical modeling. The curved geometry, transverse shear, and normal strains were exactly considered in present layerwise shell model, which can depict the zig-zag in-plane and out-of-plane displacements. The frequency response functions of curved composite shell structure and wind blade were calculated. The results show that the damping ratio of viscoelastic layer is found to be very sensitive to determination of magnitude of composite structures. The frequency response functions with variety of thickness of damping layer were investigated. Moreover, the natural frequency, modal loss factor, and mode shapes of composite fiber reinforced wind blade with viscoelastic damping control were calculated.

Vibration Analysis of Cylindrical Sandwich Aluminum Shell with Viscoelastic Damping Treatment

This paper has applied the constrained viscoelastic layer damping treatments to a cylindrical aluminum shell using layerwise displacement theory. The transverse shear, the normal strains, and the curved geometry are exactly taken into account in the present layerwise shell model, which can depict the zig-zag in-plane and out-of-plane displacements. The damped natural frequencies, modal loss factors, and frequency response functions of cylindrical viscoelastic aluminum shells are compared with those of the base thick aluminum panel without a viscoelastic layer. The thickness and damping ratio of the viscoelastic damping layer, the curvature of proposed cylindrical aluminum structure, and placement of damping layer of the aluminum panel were investigated using frequency response function. The presented results show that the sandwiched viscoelastic damping layer can effectively suppress vibration of cylindrical aluminum structure.

Force characteristic of a magnetic actuator for separable electric connector based on conical airgap

This article presents a magnetic actuator for use in a separable electric connector based on conical airgap. The magnetic flux lines in conical airgap are almost vertical to the edge face of the yoke and armature, showing that the actual flux length in conical airgap is smaller than the axial stroke, which reduces magnetic reluctance over large stroke. Parameter improvement is analyzed based on modeling, and optimal results of the magnetic actuator are adopted to improve the rate of force to volume. The experimental results show that there is friction force of 10–12 N existing in the moving armature of the prototype, and the nominal value is in accordance with the simulation one. The results show that the design of conical airgap in the magnetic actuator is available to improve the initial force and reliability of the separating process and has the advantages of compact structure, short transmission, high reliability, large force with 50 N at the initial displacement of 2.5 mm, and fast response with 16.5 ms over the traditional actuator.

Optimal Heater Control with Technology of Fault Tolerance for Compensating Thermoforming Preheating System

The adjustment of heater power is very important because the distribution of thickness strongly depends on the distribution of sheet temperature. In this paper, the steady state optimum distribution of heater power is searched by numerical optimization in order to get uniform sheet temperature. In the following step, optimal heater power distribution with a damaged heater was found out using the technology of fault tolerance, which will be used to reduce the repairing time when some heaters are damaged. The merit of this work is that the design variable was the power of each heater which can be directly used in the preheating process of thermoforming.

Piezoelectric Material Based Energy Generator Using Bistable Cantilever Beam

Recently, the vibration induced by nonlinear energy harvesting systems has been studied. This paper describes an energy generator employing bistable piezoelectric cantilever beam. The system consists of a piezoelectric material attached on cantilever, a permanent magnet fixed at tip of the cantilever beam and two magnets placed at both side of the tip magnet. The bistable phenomenon was investigated by changing the gap between the tip magnet and side magnet. The trend of output energy from bistable piezoelectric cantilever beam was studied experimentally by considering the different gap distance and different initial displacement. As shown in results, the bistable cantilevered beams show a wider range of power than the linear vibrating system.