Zhen-Zhe Li

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.

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.

Performance Prediction of Large Scale Vacuum Furnace Using Thermal Analysis

A method using thermal analysis has been recommeded to substitute the original method what was based on trial and error for manufacturing a high performance, low cost product. At first, a large scale vacuum furnace was modeled according to a real product, and it was simulated using the material properties in a previous study under the condition of having argon ambient gas. Finally, the performance of the large scale vacuum furnace was discussed using the obtained results of analysis. The method in this study will be used to produce an energy efficient, low cost product using optimization technique under the condition of fully satisfying users design requirements.

Modeling and Control of a Flywheel Energy Storage System Using Active Magnetic Bearing for Vehicle

This paper reports on the modeling and control of a flywheel energy storage system used for electric vehicle. First, by the experimental vibration analysis based on the rigid model with H-infinity control, it was found that the main cause of the flywheel rotor instability due to the influence of the first bending backward mode than that of gyroscopic effect. Subsequently, a flexible model was derived using the finite-element method and a mode separation method using the singular value decomposition was proposed for the gyroscopic matrix in order to obtain the reduced-order model. The effectiveness of the reduced-order flexible model and that of H-infinity controller were verified by the simulation. Keywordsmagnetic bearing; gyroscopic effect; H-infinity control; vibration analysis; singular value decompositio; reducedorder model

Cross-Feedback Backstepping Control for Vibration Suppression of Vehicle Magnetic Levitation Flywheel Battery Based on Root Locus Analysis

The goal of this paper is to research the vibration suppression of a vehicle magnetic flywheel battery system. It is found the flywheel rotor is always instability near a certain rotation speed controlled on the basis of the rigid model. Accordingly, the rotor regarded as a flexible rotor is investigated using the FEM and the original controller used for the rigid model is applied to the flexible model for analyzing the root locus. The result reveals the poles associated with the first bending backward mode move to the half right complex plane. Finally, a simple cross-feedback control is proposed instead of complex controller design based on the flexible model. The effectiveness is verified through the experiment.

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.

Time-dependent Optimal Heater Control Using NURBS and RSM

Thermoforming is one of the most versatile and economical processes available for shaping polymer products. To improve the competitive power of the products, the manufacturing fee should be continuously reduced. But, the required heat can not be freely reduced because of the temperature difference between surface and center of the sheets. In this paper, an optimal design using NURBS and RSM was carried out for decreasing the required heat. NURBS were used to design shapes for the time-dependent variation of heater power inputs, and D-optimal method was used to select experimental points to construct the response surfaces. The optimal results show that the developed method in this study can be used to reduce the required heat in the forming temperature range by the end of the heating process.

Notice of Retraction A Study on Steam Generator for Domestic Steam Cleaner with Cartridge Heater

The steam generation mechanism is the key technology of the domestic steam cleaner. Not only the weight and price of a steam cleaner but also the performance of a steam generation mechanism must be considered to improve the competitive power of the products. In this study, a new steam generator which using a cartridge heater was recommended for compensating the drawback of the spray boiling steam generator. The experimental and numerical results show that the warm-up time, the volume and weight of the cartridge steam generator were much smaller than the spray boiling steam generator. The experimental and numerical method in this study can be used to develop a high performance, low cost steam generator for the domestic steam cleaner.

A Method for Decreasing Preheating Time of Thermoforming

Thermoforming is one of the most versatile and economical processes to produce polymer products, and the key drawback is difficult to control the thickness of final products. The temperature distribution after the preheating process affects to the thickness distribution of final products. The cycle time must be decreased in order to improve the competitive power of the products, but the preheating time can not be decreased freely because of the key drawback. In this study, a new method for decreasing the preheating time under the condition of satisfying temperature of forming window was developed. At first, the relationship between temperature difference and preheating time was investigated. In order to check the possibility of decreasing the preheating time under the condition of satisfying temperature of forming window, finite difference method was applied under the condition of considering the effect of natural convection using optimal heating profiles expressed by exponential function form which was developed based on Duhamel’s Theorem and optimization technique in a previous study. The optimal results show that the preheating time can be decreased using the developed method in this study with satisfying temperature of forming window.