| 1. |
Fatigue failure by flow-induced vibration
The mechanism of fatigue failure by flow-induced vibration was studied by using a newly developed small wind tunnel. The necessary conditions of flow-induced vibration for a carbon steel specimen attached to a larger styrofoam cylinder were first investigated. Possible methods to detect indications of fatigue crack initiation and propagation were sought. A fatigue life prediction method was also developed. The change in natural frequency and amplitude of the test cylinder and strain history at the prospective crack initiation sites were measured. The 0.45 C steel specimen contained an artificial small hole which is expected to become the crack initiation site. A small portable service strain histogram recorder (Mini Rainflow Corder, MRC) developed in another project was used to monitor the variation of strains due to crack growth from the small hole. Fatigue damage accumulation based on Miner's rule was calculated and compared with the experimental results.. |
| 2. |
Measurement of service strains of the blade of "Wind-lens"
Measurement of service strains of the blade of Wind-lens turbine was conducted by using wireless strain measurement system in a wind tunnel apparatus. Wind-lens turbine has demonsrated power augmentation by a factor about 2-5 compared with a bare wind turbine, for a given turbine diameter and wind speed. Mean strain and vibrational strain variation range at the root of the blade was increased with the increase of uniform flow velocity of the wind tunnel. The phenomenon of vibration of the blades of Wind-lens turbine was due to a flutter or flow-induced vibration, selfexcited oscillation induced by vortices around the blades, in a certain range of flow velocity. The increase of strain variation range at the root of the blades in the case of intense variation of wind direction was caused by a gyro-moment due to a yawing movement of the Wind-lens turbine. The intense variation of wind velocity, in addition to that of wind direction, caused extreme large vibration amplitude, or strain variation.. |
| 3. |
Mechanical strength properties of Wind-lens blades
For the safety and reliability of small size Wind-lens turbine, several experiments of mechanical properties of blade's material, Dicyclopentadiene was conducted. Vickers hardness was Hv =13.8 independent of load times and load magnitudes. Fatigue strength of the specimen contained some scale voids were quite low compared to the plain specimen contained no voids. Fatigue strength of notched specimens was lower than that of plain specimen. Non-propagating fatigue crack was not observed on this material. Fatigue crack growth property was obtained by three point bending fatigue test. The relationship between fatigue crack growth rate and the stress intensity factor range, ΔK, was obtained. Charpy impact absorption energy of Dicyclopentadiene was three times as that of ABS resin. © 2012 The Japan Society of Mechanical Engineers.. |
| 4. |
Failure by Flow-Induced Vibration. |
| 5. |
Fatigue Failure by In-line Flow-induced Vibration and Fatigue Life Evaluation
The phenomenon of fatigue failure by the In-line flow-induced vibration was studied. A newly water-flow-induced vibration system was made and used to reproduce fatigue failure by flow-induced vibration. A medium carbon steel specimen was fixed to the experimental equipment. A small artificial hole was introduced onto the specimen surface. Fatigue crack initiated from the artificial hole. A small portable strain histogram recorder (Mini Rainflow Corder, MRC) developed in another project of the authors' team was used to acquire the service strain histogram at a critical point of the specimen and to measure the variation of natural frequency. Cumulative fatigue damage D defined by the Modified Miner Rule was calculated by using the strain histogram at the initial stage of test. The value of D was almost unity in the case of In-line vibration, while the values of D in the case of the Cross-flow vibration ranged from 0.2 to 0.8.. |
| 6. |
Effect of Small Defect on Fatigue Strength of Ferrite stainless Stell SUS405. |
| 7. |
S Odahara, Y Murakami, M Inoue, A Sueoka, Fatigue failure by in-line flow-induced vibration and fatigue life evaluation, JSME INTERNATIONAL JOURNAL SERIES A-SOLID MECHANICS AND MATERIAL ENGINEERING, 10.1299/jsmea.48.109, 48, 2, 109-117, 2005.04, The phenomenon of fatigue failure due to In-line flow-induced vibration has been investigated. In the experimental program an induced-vibration experimental set-up involving water flow was developed. This apparatus was used to produce fatigue failure resulting from In-line flow-induced vibration. The fatigue specimens were made of a medium carbon steel. A small hole was drilled into the specimen surface to localize the fatigue cracking process. A strain histogram recorder (Mini Rainflow Corder, MRC) was used to acquire the service strain histogram and also to detect any variations in natural frequency. The cumulative fatigue damage, D, as defined by the Modified Miner Rule, was determined by using the strain histogram of the early portion of the test record. The value of D was almost unity in the case of In-line vibration. In contrast, the value of D obtained in a previous investigation for the case of the Cross-flow vibration ranged approximately from 0.2 to 0.8.. |
| 8. |
Takumi Inoue, Atsuo Sueoka, Hiroyuki Kanemoto, Satoru Odahara, Yukitaka Murakami, Detection of minute signs of a small fault in a periodic or a quasi-periodic signal by the harmonic wavelet transform, MECHANICAL SYSTEMS AND SIGNAL PROCESSING, 10.1016/j.ymssp.2006.09.002, 21, 5, 2041-2055, 2007.07, If a machine in operation has a fault, signs of the fault appear in the monitored signal and are usually synchronised with the operating speed. The signs are very small when the fault is at an early stage. The fast Fourier transform (FFT) is often utilised to detect these signs, but it is very difficult to detect minute signs. In this paper, harmonic wavelet transform is utilised to detect the minute signs of small faults in a monitored signal. The monitored signal of a machine element, in ordinary operation, is regarded as periodic or quasi-periodic. It is important for the effectual detection of the minute signs to reduce the obstructive noise and the end effects in the signal. The end effect is a peculiar phenomenon to wavelet transform and hampers effective detection. Useful methods to reduce the obstructive noise and the end effects are devised herein by the authors. Even if no visible information pertaining to a fault appears in the monitored waveform, the present method is able to detect a minute sign of a small fault. It is demonstrated that the present method is capable of detecting minute signs arising from slight collisions caused by a loose coupling and a fatigue crack. (c) 2006 Elsevier Ltd. All rights reserved.. |
| 9. |
Satoru Odahara, Takahiro Yamauchi, Takayuki Fukuda, Effects of Notch Shape and Cyclic Loading Test Frequency of the Fatigue Strength Properties of Poly-Lactic Acid, 佐世保高専研究紀要, 45, 45, 11-14, 2009.01. |
| 10. |
Investigation and analysis of the cause of failure accident of Wind-lens turbine blades. |
| 11. |
Design and production of solar boat and investigation on the ship development in consideration of earth environment. |
| 12. |
Satoru ODAHARA, Takumi INOUE, Fatigue Failure by In-line Flow-induced Vibration (Fatigue Crack Detection and Fatigue Life Evaluation), International Conference on Nuclear Engineering 19th (ICONE19), 2011.05. |
| 13. |
Wen-Xue Wang, Terutake Matsubara, Satoru Odahara, Yuji Ohya, Takashi Karasutani, Effects of the Flanged Diffuser on the Dynamic Behavior of CFRP Blade of a Shrouded Wind Turbine, Grand Renewable Energy 2014 International Conference and Exibition, 10.11333/jwea.38.4_A_98, O-Wd-18-1, 4, A_98-A_104, 2014.07, Wind tunnel experiment was conducted to investigate the influence of the flanged diffuser on the dynamic behavior of the blade of a 3kW wind turbine shrouded with a flanged diffuser. Three wind velocities (6.9 m/s to 11.6 m/s) and three different yawing angles (0-degree to 30-degree) were tested to investigate the effects of the flanged diffuser and the yawing angle on the dynamic behavior of blade. Three blades were fabricated by the skin of carbon fiber reinforced plastic (CFRP) and Piocelan core. The blade rotation speed and the dynamic strain at the blade were measured under the conditions with and without the flanged diffuser. Two telemeter systems of transmitter and receiver were used in the measurement of the dynamic strains at the rotating blade. Experimental results reveal that the rotation speed and the dynamic strain at the blade of the wind turbine with the flanged diffuser are much higher than those without the flanged diffuser. On the other hand, the rotation speed and the dynamic strain at the blade decrease as the yawing angle increases. Furthermore, the influence of the flanged diffuser on the variation of the tensile strain within one rotation is relatively slight. The CFRP blade is available for small wind turbine with relatively high rotation speed to reduce the centrifugal force.. |
| 14. |
Satoru ODAHARA, Effect of Variations of Yaw Angle on the Service Strains of Blade of Wind-lens Turbine, Grand Renewable Energy 2014 International Conference and Exibition, P-Wd-2-29, 2014.07. |
| 15. |
Effects of the Flanged Diffuser on the Dynamic Behavior of CFRP Blade of a Shrouded Wind Turbine
Wind tunnel experiment was conducted to investigate the influence of the flanged diffuser on the dynamic behavior of the blade of a 3kW wind turbine shrouded with a flanged diffuser. Three wind velocities (6.9 m/s to 11.6 m/s) and three different yawing angles (0-degree to 30-degree) were tested to investigate the effects of the flanged diffuser and the yawing angle on the dynamic behavior of blade. Three blades were fabricated by the skin of carbon fiber reinforced plastic (CFRP) and Piocelan core. The blade rotation speed and the dynamic strain at the blade were measured under the conditions with and without the flanged diffuser. Two telemeter systems of transmitter and receiver were used in the measurement of the dynamic strains at the rotating blade. Experimental results reveal that the rotation speed and the dynamic strain at the blade of the wind turbine with the flanged diffuser are much higher than those without the flanged diffuser. On the other hand, the rotation speed and the dynamic strain at the blade decrease as the yawing angle increases. Furthermore, the influence of the flanged diffuser on the variation of the tensile strain within one rotation is relatively slight. The CFRP blade is available for small wind turbine with relatively high rotation speed to reduce the centrifugal force.. |
| 16. |
Wen-Xue Wang, Terutake Matsubara, Junfeng Hu, Satoru Odahara, Tomoyuki Nagai, Takashi Karasutani, Yuji Ohya, Experimental investigation into the influence of the flanged diffuser on the dynamic behavior of CFRP blade of a shrouded wind turbine, RENEWABLE ENERGY, 10.1016/j.renene.2015.01.028, 78, 386-397, 2015.06, Wind tunnel experiments were conducted to investigate the influence of the flanged diffuser on the dynamic behavior of the blade of a 3 kW wind turbine shrouded with a flanged diffuser. The blade was fabricated by the skin of carbon fiber reinforced plastic and solid foam core. Tests were carried out for three wind velocities (6.9 m/s to 11.6 m/s) and three different yawing angles (0-degree to 30-degree) to investigate the effects of the interactions of the flanged diffuser and the yawing angle on the blade. The rotational speed of the blade and the dynamic strain near the blade root were measured under the conditions with and without the flanged diffuser. Two telemeter systems of transmitter and receiver were used in the measurement of the dynamic strains of the rotating blade. The mechanical tests of the blade and the skin of the blade were also performed to obtain basic data for the estimation of the strength of the blade. Experimental results reveal that the rotational speed and the dynamic strain of the blade of the wind turbine with a flanged diffuser are much higher than those without a flanged diffuser. (C) 2015 Elsevier Ltd. All rights reserved.. |
| 17. |
Characteristics of In-line Flow-Induced Vibration in Case of Two Circular Cylinders. |
