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Kita Kyushu, Japan

Matsuzaki K.,Kagoshima University | Ryu T.,Oita University | Sueoka A.,Kyushu Polytechnic College | Tsukamoto K.,Ayabo Corporation 1 Hosogute
International Journal of Machine Tools and Manufacture

Boring and Trepanning Association (BTA) deep hole drilling is used for producing holes with high aspect ratios. In this process, chatter vibration sometimes occurs, and a rifling mark is formed on the bore surface. The rifling mark generating phenomenon is considered to be a result of self-excited vibration caused by time delay. An analytical model is proposed considering the supporting condition of the boring bar in detail. In a real machine for BTA drilling, the boring bar is supported at the oil pressure head and the supporting pad, as well as at the base. The stability of the self-excited vibration is analyzed numerically, and the result is compared with the experiment. The theoretical and experimental results agree well with each other. Furthermore, the effect of an additional guide pad proposed by the authors as a countermeasure is evaluated theoretically and experimentally. © Elsevier Ltd. All rights reserved. Source

Rosbi S.,Oita University | Ryu T.,Oita University | Nakae T.,Oita University | Matsuzaki K.,Kagoshima University | And 3 more authors.
MOVIC 2014 - 12th International Conference on Motion and Vibration Control

This paper analyzes a suppression method for nonlinear vibration called subharmonic vibration of order 1/2 in car powertrains by using a dynamic absorber. In car powertrains, the torsional forced vibration caused by engine combustion leads to reduced ride quality. Thus, in the torque converter of an automatic transmission car, a piecewise-linear spring called a damper is used to reduce the transmission of the forced vibration into the vehicle frame. However, subharmonic vibration occurs in the actual vehicle when the spring restoring characteristics are around the switching point. The fundamental vibration frequency of the subharmonic vibration is half of the engine forced vibration frequency. Although the design of the dynamic absorber used to suppress the forced vibration has been established for linear systems, the optimum design for suppressing subharmonic vibration of order 1/2 has not yet been investigated. In this study, the powertrain is modeled using a multi-degree-of-freedom system for the actual vehicle, including the engine, torque converter, transmission gears, and wheels. An equation of motion is developed by also considering the restoring force of the piecewise-linear spring. The numerical result shows that subharmonic vibration occurs when the engine excitation frequency is almost twice the second mode of the natural frequency, and the result shows good agreement with the experimental data. Then, the dynamic absorber is introduced to suppress the occurrence of subharmonic vibration. In this paper, the optimum design of the dynamic absorber used to suppress the subharmonic vibration is discussed. The numerical results show that with the appropriate natural frequency and damping ratio, the optimally designed dynamic absorber is capable of suppressing the occurrence of subharmonic vibration. © 2014 The Japan Society of Mechanical Engineers. Source

Makino T.,Nippon Steel & Sumitomo Metal Corporation | Kato T.,Nippon Steel & Sumitomo Metal Corporation | Hirakawa K.,Kyushu Polytechnic College
Engineering Fracture Mechanics

Railway axles are one of the most important components in railway systems since a fail-safe design is not available. In the present paper, the fatigue tolerance of the high-speed railway axle in Japan is reviewed. To maintain the safety, the fatigue strength of the axle has been extensively studied. Theses case histories and consequent improvements in manufacturing process are presented. The crack propagation behavior of the induction hardened axle is studied based on the fracture mechanics. Concerning the powered railway axles, the fatigue design method in Japan is compared with that in Europe and the effect of the train velocity on the allowable load is discussed. © 2010 Elsevier Ltd. Source

Seama N.,Kobe University | Seama N.,Japan Agency for Marine - Earth Science and Technology | Tada N.,Japan Agency for Marine - Earth Science and Technology | Goto T.-N.,Kyoto University | Shimoizumi M.,Kyushu Polytechnic College
Earth, Planets and Space

We propose to use an approximately vertical bipole electric current towed by a ship as a source for a Magnetometric Resistivity (MMR) method. This proposal requires the precise positioning of the bottom electrode for the bipole source, and our newly developed MMR system achieved this. We conducted an MMR experiment in the central Mariana Trough, and we obtained data using two different methods along a survey line: one method towed a bipole source transmitting continuously along the survey line, and the other used a conventional vertical bipole source transmitting at several stationary transmission stations along the survey line. We found that the towed bipole source tilted from the vertical by an angle of 8 degrees at the maximum during the MMR experiment. We compared the results from the two methods to evaluate the towed bipole source method. Our results indicate that the tilted bipole source approximates well with the vertical bipole source at the mid-point between the surface and the bottom electrodes. Since the towed bipole source method requires much less survey time and the results show a higher spatial resolution, it is a powerful tool for MMR experiments to image a shallow oceanic crustal resistivity structure efficiently. Copyright © The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS). Source

Makino T.,Nippon Steel & Sumitomo Metal Corporation | Kato T.,Nippon Steel & Sumitomo Metal Corporation | Hirakawa K.,Kyushu Polytechnic College
International Journal of Fatigue

Shelling is one of the typical rolling contact fatigue (RCF) failures of railway wheels. Creepage between wheels and rails due to rolling radius difference in curves is inevitable on railway tracks. Therefore, there are tangential stresses and slip phenomena on wheel treads. Eventually, initiation of RCF cracks being the origin of shelling is accelerated by creepage. The objective of the present paper is to evaluate RCF property of railway wheel steel. The effect of the slip ratio on the RCF strength of the railway wheel steel was evaluated. RCF tests were conducted using two cylindrical contact specimens under water lubrication at a slip ratio of 0.0-1.0%. The range of slip ratio is determined to assume a creepage between wheel and rail during curving. As a result, it was found that the traction coefficient increased with the increase in the slip ratio, and the fatigue strength decreased simultaneously. The results were evaluated by a shakedown map and Hirakawa's RCF map. Experimental fatigue limits could be expressed more precisely by the criterion of Hirakawa's RCF map than that expressed by the well-known shakedown map. Stress intensity factors (SIFs) of the cracks produced by the RCF test were calculated by finite element (FE) analysis where the effect of water pressure due to the penetration of water into the cracks is taken into account. Two peaks of the maximum tangential SIF occurred during one cycle of rolling contact. The direction of the crack propagation was estimated by the maximum tangential stress criteria. The results of the RCF test showed that the cracks were initiated at the surface, propagated obliquely in the depth direction and then branched into two directions. One was towards the surface and the other was towards the depth. These two crack directions were inspected experimentally, corresponding to the estimated crack directions from the two peaks of SIF by FE analysis. The effect of slip ratio on RCF crack propagation was discussed by using the SIFs of the RCF cracks where water penetration into the cracks was considered. © 2011 Published by Elsevier Ltd. Source

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