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Ono T.,Torishima Pump Manufacturing Co.
Nihon Kikai Gakkai Ronbunshu, C Hen/Transactions of the Japan Society of Mechanical Engineers, Part C | Year: 2013

This paper investigates the influences of the coupling element placed between nonlinear self-excited oscillators on synchronization. A simple model is newly developed by modifying the model treated in our previous report. The model consists of two oscillators subjected to Coulomb friction and a block installed in the coupling element. These elements are connected in series by coil springs and dashpots. In this model, stick-slip motions frequently occur due to the Coulomb friction. The synchronized solutions and the stability are analyzed accurately by the improved shooting method. The new model is validated by comparing the calculated results and the experimental results, and the features of the synchronized solutions are investigated. The results show that the frequencies and vibration patterns of the synchronized solutions closely correspond to the natural frequencies and natural modes of the three-degree-of-freedom system without the Coulomb friction, and that the existence regions of the synchronized solutions depend on the block mass as a parameter of coupling element. When the parameter is appropriately set, the existence regions expand. The mechanism is examined from the viewpoint of the energy transition between the oscillators. © 2013 The Japan Society of Mechanical Engineers. Source


Omori T.,Torishima Pump Manufacturing Co. | Morita T.,University of Zagreb | Okada K.,Goshokaido cho | Maeda H.,Torishima Pump Manufacturing Co.
Tribology International | Year: 2015

This study investigated the relationship between local stress amplitude generated at contact edges and the fretting fatigue strength of austenitic stainless steel SUS316. Fretting fatigue strength was examined using a new in-house experimental method. Local stress amplitude at contact edges was evaluated using finite element analysis (FEA) that allows for elastic-plastic behavior as well as contact friction. The fretting phenomenon generated from the application of plain fatigue strength significantly reduced fatigue strength. Although fretting fatigue strength decreased with increased contact stress, it became constant when the contact stress exceeded a specific value. The features of fracture surfaces showed that cracks originated from shallow regions at the contact edges because of stress concentration in that area. The results of FEA showed that local stress amplitude at the contact edges with each contact stress was similar under conditions of various fretting fatigue strengths. This finding suggested that the fretting fatigue strength can be evaluated from a mechanical standpoint by FEA. © 2015 Elsevier Ltd. Source


Omori T.,Torishima Pump Manufacturing Co. | Morita T.,Kyoto Institute of Technology | Okada K.,Kyoto Institute of Technology | Maeda H.,Torishima Pump Manufacturing Co.
Materials Transactions | Year: 2015

This study was conducted to investigate the effect of hybrid surface treatments on the fretting fatigue strength of austenitic stainless steel JIS SUS316. The hybrid surface treatments were composed of plasma nitriding (hereafter, PN) and fine particle bombarding (FPB) or PN and diamond-like carbon (DLC) coating. Although the combination of PN and FPB slightly increased the friction coefficient, it improved wear resistance through the formation of a hardened layer. The combination of PN and DLC coating markedly improved the friction-wear properties because the thin DLC layer was supported by the hardened layer formed below it. Neither treatment had any influence on mechanical properties. The above hybrid surface treatments greatly improved the fretting fatigue strength. The improvement percentage was 44% in the case of the combination of PN and FPB, and reached 54% with the combination of PN and DLC coating. To examine corrosion resistance, the hybridsurface- treated materials were fully immersed into 5% salt water held at 363K (90 degrees C). The results showed that their corrosion resistance was maintained for 2.42Ms (28 days) without surface damage. © 2015 The Japan Institute of Metals and Materials. Source


Omori T.,Torishima Pump Manufacturing Co. | Morita T.,Kyoto Institute of Technology | Okada K.,Kyoto Institute of Technology | Maeda H.,Torishima Pump Manufacturing Co.
Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals | Year: 2016

This study was conducted to improve fretting fatigue strength of austenitic stainless steel JIS SUS316 by the hybrid surface treatment composed of plasma nitriding (hereafter, PN) and fine-particle bombarding (FPB). In the study, finite element analysis (FEA) was also performed to investigate local stress-strain response induced at the contact edges in fatigue specimens. Since the above hybrid surface treatment didn't affect the microstructure in the substrate, there was no influence on the mechanical properties. Fretting fatigue strength was markedly improved by the hybrid surface treatment, and its improvement percentage reached 50%. The results of FEA showed that "shakedown" occurred at the contact edges under applied cyclic stress so that local mean stress there became zero. The formed hardened layer had no effect to improve wear condition at the contact edges. Accordingly, it was suggested that the improvement of fretting fatigue strength resulted from the increase in crystallographic slip resistance by the formed hardened layer. © 2016 The Japan Institute of Metals and Materials. Source


Kinoue Y.,Saga University | Shiomi N.,Saga University | Setoguchi T.,Saga University | Sawamura K.,Torishima Pump Manufacturing Co. | Maeda H.,Torishima Pump Manufacturing Co.
ASME-JSME-KSME 2011 Joint Fluids Engineering Conference, AJK 2011 | Year: 2011

Using the design method based on the design for axial-flow type turbomachine, the diagonal flow pump impellers were designed for two cases of the centrifugal effect parameter a. In addition, three-dimensional Navier-Stokes numerical calculations for single-phase were conducted in order to examine the tendency of the suction performance as well as the head performance. The head increases from the NS calculation of the impeller are the same between for a=0.4 and for a=1.0 because major specification are the same between for a=0.4 and for a=1.0. For the minimum pressure on the rotor blade, however, there is a difference between for a=0.4 and for a=1.0. The value of minimum pressure for a=0.4 is -324kPa, whereas the value for a=1.0 is -294 kPa. The blade geometry for a=1.0 is better than the one for a=0.4 in terms of the suction performance because the trough of the minimum pressure is shallower for a=1.0 than a=0.4. Furthermore, Navier-Stokes numerical calculations were also conducted for off-design flow rate. For all cases in this paper, the minimum pressure on the rotor blade occurred at both near the leading edge and near the tip on the suction side of the blade. In addition, for all cases in this paper, the blade geometry for a=1.0 is better than the one for a=0.4 in terms of the suction performance. Copyright © 2011 by ASME. Source

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