Effect of Metal Coating on FRP Blade Lightning Failure for Wind Power Generators

In Japan, with the recent increase in wind power generator installations, the incidence of lightning damage to FRP blades is increasing. Lightning damage is a significant issue in Japan since lightning in Japan seems severer than that in Europe or the US. In Kochi, Japan, six 600-750 kW grade generators have been installed, and some have been damaged by lightning several times. To resolve this problem, the Kochi University of Technology received a request in 2002 from the Kochi prefectural government for research into lightning protection. After surveying the literature and questioning related organizations such as NREL and Toray USA, experiments to protect against lightning damage to FRP blades of wind power generators were planned. Half size models and two 1/4 parts of a full size 250kW blade were prepared as specimens for this research. The method investigated to protect against lightning damage was metal coating. The aim being to protect against blade failure by using metal coating in actual field situations; by using a 1/2 size model and the full size blade specimens in an experimental situation. As in previous experiments, these ones were mainly conducted in the Toshiba Hamakawasaki High Voltage High Power Testing Laboratory. This Testing Laboratory is one of the biggest test laboratories for experiments involving high voltages and large currents.

Free Flexural Vibrations Response of Composite Mindlin Plates or Panels With a Centrally Bonded Symmetric Double Lap Joint (or Symmetric Double Doubler Joint)

The present study is concerned with the “Free Flexural Vibrations Response of Composite Mindlin Plates or Panels with a Centrally Bonded Symmetric Double Lap Joint (or Symmetric Double Doubler Joint). The plate “adherends” and the plate “doublers” are considered as dissimilar, orthotropic “Mindlin Plates” with the transverse and the rotary moments of inertia. The relatively, very thin adhesive layers are taken into account in terms of their transverse normal and shear stresses. The mid-center of the bonded region of the joint is at the mid-center of the entire system. In order to facilitate the present solution technique, the dynamic equations of the plate “adherends” and the plate “doublers” with those of the adhesive layers are reduced to a set of the “Governing System of First Order ordinary Differential Equations” in terms of the “state vectors” of the problem. This reduced set establishes a “Two-Point Boundary Value Problem” which can be numerically integrated by making use of the “Modified Transfer Matrix Method (MTMM) (with Interpolation Polynomials)”. In the adhesive layers, the “hard” and the “soft” adhesive cases are accounted for. It was found that the adhesive elastic constants drastically influence the mode shapes and their natural frequencies. Also, the numerical results of some parametric studies regarding the effects of the “Position Ratio” and the “Joint Length Ratio” on the natural frequencies for various sets of support conditions are presented.

A Comparison Study of Mahalanobis-Taguchi System and Neural Network for Multivariate Pattern Recognition

The Mahalanobis-Taguchi System is a diagnosis and predictive method for analyzing patterns in multivariate cases. The goal of this study is to compare the ability of the Mahalanobis-Taguchi System and a neural network to discriminate using small data sets. We examine the discriminant ability as a function of data set size using an application area where reliable data is publicly available. The study uses the Wisconsin Breast Cancer study with nine attributes and one class.

Comparison of Analytical and Empirical Models to Capture Variations in Off-Road Vehicle Dynamics

This paper develops two analytical models that describe the yaw dynamics of a farm tractor and can be used to design or improve steering control algorithms for the tractor. These models are verified against empirical data. The particular dynamics described are the motions from steering angle to yaw rate. A John Deere 8420 tractor, outfitted with inertial sensors and controlled through a PC-104 form factor computer, was used for experimental validation. Conditions including different implements at varying depths, as would normally be found on a farm, were tested. This paper presents the development of the analytical models, validates them against empirical data, and gives trends on how the model parameters change for different configurations.

Periodic Motions in a Periodically Forced Oscillator Moving on the Oscillating Belt With Dry Friction

In this paper, periodic motion in an oscillator moving on a periodically vibrating belt with dry-friction is investigated. The conditions of stick and non-stick motions for such an oscillator are obtained in the relative motion frame, and the grazing and stick (or sliding) bifurcations are presented as well. The periodic motions are predicted analytically and numerically, and the analytical prediction is based on the appropriate mapping structures. The eigenvalue analysis of such periodic motions is carried out. The periodic motions are illustrated through the displacement, velocity and force responses in the absolute and relative frames. This investigation provides an efficient method to predict periodic motions of such an oscillator involving dry-friction. The significance of this investigation lies in controlling motion of such friction-induced oscillator in industry.

FEM Stress Analysis and Sealing Performance in Pipe Flange Connections With Adhesive Subjected to Internal Pressure and External Bending Moments

This study deals with the stress analysis and the estimation of sealing performance of the pipe flange connections with an adhesive under an internal pressure and an external bending moment are analyzed by using the 3-dimensional elastic finite element method (FEM). The experiment of the leakage test of the connections with an adhesive was carried out by applying the above loads to the connections. From the FEM analysis, the following results were obtained; (1) when an internal pressure is applied to the flange connections, the compressive stress at the interface between a flange and an adhesive increases proportionally from the inner side of the interface to outside, and (2) when an internal pressure and a bending moment apply to the flange connections, the stress distribution at the half part of the interface increases as the external bending moments increase and also Young’s modulus of the adhesive increases. From the experiments, the following results were obtained: (1) sealing performance of the pipe flange connections with an adhesive under an internal pressure and an external bending moment increases as the flange thickness and an initial clamping force of bolts increases and (2) the sealing performances were not found between the connections with an adhesive and that with a gasket combining an adhesive. Furthermore, the numerical results are in fairly good agreement with the experimental results.

Structural Analysis of Utility Boiler Waterwall

The safe structural design of boiler waterwalls with various loadings such as dead weight, fluid pressure, gas pressure and thermal differences is an extensive problem demanding the use of sophisticated computation methods due to the complexity of the geometric structure and the large size of the walls. To evaluate the operating reliability of boiler waterwalls, it is essential to know not only overall behavior of the whole structure but also the stress states at the critical zones. In this paper, the structural soundness for the Korea standard 500MW boiler waterwalls is preliminary examined. The equivalent orthotropic plate model is used to investigate the structural behavior of boiler waterwalls under thermal differences. Submodeling technique for part model of boiler waterwalls is proposed to accurately compute stresses of waterwalls at the critical zones under gas pressure. The computed stresses are combined and finally compared with the allowable stress limits according to the criteria of ASME Code.

Quasi-Static Lap Shear and Dynamic Impact of High Performance VHB™ Acrylic Foam and Adhesive Transfer Tape Bonded Aluminum Joints Subjected to Environmental Degradation

A range of 3M™ VHB™ acrylic foam tapes and high performance adhesive transfer tapes were used to bond 1” × 1/8″ (25.4 mm × 3.175 mm) aluminum 2024 T-4 adherends in single-lap joint (SLJ) and three-point end-notched flexure (ENF) configurations. Three types of 0.045” thick double-coated acrylic foam tapes: Foam 41, 50 and 52 (firm, soft and softer), and three types of adhesive transfer tapes: Adhesives 69, 73 and 85 (0.005”, 0.01” and 0.005” thick, respectively) were used for this study. The samples were subjected to two types of aggressive environments simulating extreme service conditions: freeze-thaw cycling from 10°F to 50°F at 6 cycles per day (ASTM C666 Procedure A) for 21 days with samples immersed in water; heat-cool cycling (with 90% of maximum recommended temperature by the manufacturer of both acrylic foam and adhesive transfer tapes attained at 70% relative humidity) and 3 cycles per day for 21 days. Initially the impulse-frequency response vibration and electrochemical impedance spectroscopy (EIS) techniques were used for monitoring bond quality nondestructively and selecting the best out of 250 fabricated samples. After obtaining baseline data, the specimens were subjected to quasi-static lap-shear and dynamic impact loading to compare their lap-shear failure loads and shear energy along with the impact load and energy absorbed.

Impulse-Frequency Response and EIS Based NDE for Characterizing Bond Integrity of Adhesive Joints Subjected to Environmental Degradation

Single-Lap Joint (SLJ) and three-point end-notched flexure (ENF) joint configurations were used to bond 1” × 1/8″ (25.4mm × 3.175mm) aluminum 2024 T-4 adherends using a range of 3M™ high performance pressure sensitive adhesives (Adhesives 69, 73 and 85) and VHB™ acrylic foam tapes (Foam 41, 50, 52). Batches of bonded specimens were subjected to two types of aggressive environments simulating extreme service conditions: freeze-thaw cycling from 10°F to 50°F at 6 cycles per day (ASTM C666 Procedure A) for 21 days with samples immersed in water; heat-cool cycling (with 90% of maximum recommended temperature by the manufacturer of both acrylic foam and adhesive transfer tapes attained at 70% relative humidity) and 3 cycles per day for 21 days. Electrochemical Impedance Spectroscopy (EIS) and Fast Fourier Transform (FFT) based impulse frequency response vibration Non-Destructive Evaluation (NDE) techniques were used to monitor overall bond integrity.

Hybrid Stepper Motor Backstepping Control in Micro-Step Operation

A nonlinear position controller based on backstepping control technique is proposed for a hybrid stepper motor in micro-step operation. Backstepping control approach is adapted to derive the control scheme, which is robust to parameter uncertainties and external load disturbance. Simulation results clearly show that the proposed controller can track the position reference signal successfully under parameter uncertainties and load torque disturbance rejection.