JOURNAL OF JAPANESE SOCIETY OF TRIBOLOGISTS
Online ISSN : 2189-9967
Print ISSN : 0915-1168
ISSN-L : 0915-1168
Volume 64 , Issue 7
Special Issue on Tribology in Our Immediate Surroundings (Part 4)
Showing 1-13 articles out of 13 articles from the selected issue
Announcement
Contents
The Inaugural Address by the President
Special Issue on Tribology in Our Immediate Surroundings (Part 4)
Explanation
  • ―Measurements of Milk, Fat Free Milk, and Processed Soy Milk―
    Yasuhito KAJITA, Keisuke MIYAMOTO
    2019 Volume 64 Issue 7 Pages 381-386
    Published: July 15, 2019
    Released: July 15, 2019
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    It is said that texture and mouth feel of food and beverages are very important to design them. In oral processing, food and beverages flow and also behave as lubricant or glue in mouth. For this reason, it is important to understand sensory perception of food, by rheological and tribological measurements. In this article, we performed the rheological and tribological measurement of milk, fat free milk and soy milk, respectively. And we found some differences in three samples in both rheological and tribological measurements and found no relationship between these measurements. This indicates that rheological and tribological measurement show us different aspect of food sensory perception, and both measurement can be important to understand the sensory perception of food.

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  • Saiko AOKI
    2019 Volume 64 Issue 7 Pages 387-393
    Published: July 15, 2019
    Released: July 15, 2019
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    Touch panels are used for various devices and products related to everyday life such as smartphones and tablet PCs. The system and structure of touch panels are selected according to applications for using the equipment and required performance. A manipulation with finger also changes according to the system and structure of touch panels. When people operate the touch panel,it is usually necessary to slide their finger on the surface of touch panel display. Thus, controlling friction between the finger and the surface of the display is a key technology to improve usability and operability of the tough panel. In this article, not only the system and structure of the touch panel but also the coating material used for the display are explained. In addition, the research regarding the friction behaviors between the display surface and the finger in manipulation of the touch panel are also described.

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  • ―Comparison between Edible Rice and Brewing Rice―
    Koji KAWAKAMI
    2019 Volume 64 Issue 7 Pages 394-399
    Published: July 15, 2019
    Released: July 15, 2019
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    Rice milling technology has a great influence on edible rice quality as well as sake brewing. The purpose of rice milling for edible rice is to remove an embryo, a pericarp, a seed coat and aleurone layers. A part of an endosperm is also milled for sake brewing. One of the milling function is grinding, the other is friction. The feature of grinding is high circumferential velocity of abrasive rollers and low pressure of a milling chamber. The characteristic of friction is low circumferential velocity of them and high pressure of it. The combination of abrasive and friction type what is called the compass system is suitable for edible rice of Japonica. Only abrasive type is used for the milling of brewing rice.

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  • Takashi NAKAE
    2019 Volume 64 Issue 7 Pages 400-405
    Published: July 15, 2019
    Released: July 15, 2019
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    This paper deals with the generation mechanisms of the low frequency squeals generated in a rigid type of a car and a bicycle disc brake experimentally. In the case of out-of-plane squeal generated in a car disc brake, the natural frequencies of the out-of-plane vibration of the disc and caliper are close to the squeal frequency, and the out-of-plane squeal was concluded to be caused by the excitation of the coupled out-of-plane vibration of the disc and caliper by Coulomb friction. The vibration modes of the brake units during squealing are also investigated. Additionally, the relationship between the rate of squeal occurrence and both the direction of disc rotation and the effect of pad cut area are investigated. And the effect of the rubber installation to the pads on squeal is also investigated. In the case of in-plane squeal generated in a bicycle disc brake, it has been made clear that the squeal is mainly a torsional vibration of the disc and hub in the in-plane direction of the disc surface caused by dry friction which the frictional characteristics have a negative slope with respect to the relative velocity.

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  • Tomoharu AKAGAKI
    2019 Volume 64 Issue 7 Pages 406-412
    Published: July 15, 2019
    Released: July 15, 2019
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    Bruxism during sleep causes tooth wear and fractures, gum damage, and dental-repair-material fractures. So far no simple cures or controls have been found for bruxism. In order to prevent the bruxism-related tooth wear and fractures, a mouthguard mainly made of Ethylene-Vinyl-Acetate (EVA) has commonly been applied in clinical practices. However, it has been well known that EVA is easily worn out and perforated due to the sleep bruxism. Thus the friction and wear of the mouthguard are important problems in dental tribology. This paper outlines EVA's tribological properties: the friction and wear behaviors of EVA under dry and lubricated conditions, and the effects of laser-textured surface with pits on the friction and wear.

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Explanation
  • Mitsuru URABE, Hirokazu MURATA
    2019 Volume 64 Issue 7 Pages 413-419
    Published: July 15, 2019
    Released: July 15, 2019
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    For the purpose of improving fuel economy of automobile engines, the case where friction reduction by using dimple micro texture will be explained. This technology is a case where the friction between the piston ring and the cylinder bore is reduced by dimple micro texture on the sliding surface of the inner wall of the cylinder liner. Since it was adopted as a diesel engine for the first time in the world, it has been expanded to gasoline engines. In the present technology, dimple shape, arrangement, depth,processing range, etc. are optimized to the characteristics of automobile engine, and friction loss energy is successfully reduced by 17%. In this explanation, SAE technical paper 2014-01-1661, JSAE20135625 and JSAE20156214 summarizing the mechanism of friction effect, the basis of optimization, etc. will be briefly described.

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Up-to-date News Essay for Overseas Experience in Tribology -Around the World-
Original Contribution on Technology
  • Yoshiaki OKAMURA, Kazuki IKOMA, Takafumi NAGATOMO, Hiroshi UTSUNOMIYA
    2019 Volume 64 Issue 7 Pages 424-433
    Published: July 15, 2019
    Released: July 15, 2019
    [Advance publication] Released: May 10, 2019
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    Axle journal bearings composed of an inner ring, a backing ring, etc. are used in railway applications. The axle bearings often show fretting wear due to slight relative slip between the inner ring and the backing ring. In this work, the authors have investigated the effects of segment-structured chromium nitride (CrN) film coated on the backing ring on the fretting wear. A rotation test using a full-scale railway axle bearing with a backing ring of a side face which is coated with the segment-structured CrN was conducted. As a result, the segment-structured CrN film had little effect on fretting wear prevention. This is presumably because the CrN film was formed in the groove between the segments. Therefore, when the backing ring was deformed due to the rotary bending of the axle, some cracks and decohesion occurred in the CrN film because the CrN film formed in the groove between the segments was not able to follow the deformation. It is conceivable that the fretting wear of the axle journal bearing can be prevented if it is possible to establish a method in which the CrN film is not formed in the groove between the segments.

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