著者

山本 勝太 牧野 一成 石塚 弘道

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.856, pp.17-00337-17-00337, 2017 (Released:2017-12-25)

参考文献数

10

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The integrity of railway axles is a critical aspect for ensuring the safety of a railway system. Therefore, non-destructive inspections such as ultrasonic testing and magnetic particle testing are conducted periodically. Some railway operators conduct ultrasonic tests directly on axles mounted on the train. However, the axles have to be disassembled for conducting magnetic particle testing. In the present study, the effects of variable amplitude stress acting on cracks and axle bending stress during ultrasonic test on ultrasonic response are discussed. An ultrasonic test was conducted using a full-scale axle specimen that had fatigue cracks and no artificial notches. The ultrasonic response was evaluated for the cracks whose lengths were 10 mm, 16 mm, and 19 mm. Under an unloaded condition, the ultrasonic response for the 16-mm-long and 19-mm-long cracks was approximately 4 or 7 times higher than that for the 10-mm-long crack, although the cross-sectional area of each of these cracks was approximately 2.5 or 3.5 times larger than that of the 10-mm-long crack. The obtained results indicate that the contribution of the reflection area to the ultrasonic response under a variable amplitude stress differs from that under a constant stress condition. Moreover, the influence of axle bending stress ranging between -50 MPa to +47 MPa on the ultrasonic response was investigated. A higher bending stress led to a higher ultrasonic response. However, the decreasing rate of ultrasonic response caused under compressive stress was lower than the increasing rate under tensile stress. For example, the ultrasonic response was approximately 2 dB lower than that under the unloaded condition at a compressive stress of -30 MPa; however, the ultrasonic response showed an increment of approximately 4 dB at a tensile stress of 30 MPa. A similar trend was observed in the crack of each length. The results denote that the crack position influences the precision of crack detection in ultrasonic inspection. However, considering that the maximum static bending stress of axles used in Japan is 30 MPa, its effect on inservice axle inspection is negligible.

著者

山本 勝太郎

出版者

The Japanese Society of Fisheries Science

雑誌

日本水産学会誌 (ISSN:00215392)

巻号頁・発行日

vol.51, no.11, pp.1755-1760, 1985

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To obtain a standard for rope usage, the tensile breaking strength of various ropes tied in ten different kinds of knots has been tested in both dry and wet conditions. The ropes tested were a polyethylene, a polypropylene, a mixed one consisting of polyethylene and vinylone which comprised a 3-strand laid rope, and a polyethylene 8-strand braided rope. The commercial size was 9mm in diameter for all ropes. "Dry condition" means that the knot samples were stored at normal temperature of a room, and "wet condition" means that the knot samples were soaked in water applying a pressure of 2.0kg/cm² for 12h. Results of tests for tensile breaking strength indicated that the optimum number of tucks in an eye splice was 4 tucks for the laid ropes, and 3 tucks for the braided rope. Percentages of the knot strength to the dry one of the eye splice although being somewhat different for both sample conditions and among the kinds of ropes tested, were roughly estimated as follows: 50% for the overhand knot and the single-sheet bend with end return, 55% for the double-sheet bend, 60% for the bowline knot and kakine-musubi and 95% for the short splice. Furthermore, percentages of the knot strength to the dry strength of the unknotted rope, if estimated as 90% for the eye splice, become 45%, 50%, 55% and 85% respectively.

著者

山本 勝太郎

出版者

公益社団法人 日本水産学会

雑誌

日本水産学会誌 (ISSN:00215392)

巻号頁・発行日

vol.51, no.11, pp.1755-1760, 1985-11-25 (Released:2008-02-29)

参考文献数

6

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To obtain a standard for rope usage, the tensile breaking strength of various ropes tied in ten different kinds of knots has been tested in both dry and wet conditions. The ropes tested were a polyethylene, a polypropylene, a mixed one consisting of polyethylene and vinylone which comprised a 3-strand laid rope, and a polyethylene 8-strand braided rope. The commercial size was 9mm in diameter for all ropes. “Dry condition” means that the knot samples were stored at normal temperature of a room, and “wet condition” means that the knot samples were soaked in water applying a pressure of 2.0kg/cm2 for 12h. Results of tests for tensile breaking strength indicated that the optimum number of tucks in an eye splice was 4 tucks for the laid ropes, and 3 tucks for the braided rope. Percentages of the knot strength to the dry one of the eye splice although being somewhat different for both sample conditions and among the kinds of ropes tested, were roughly estimated as follows: 50% for the overhand knot and the single-sheet bend with end return, 55% for the double-sheet bend, 60% for the bowline knot and kakine-musubi and 95% for the short splice. Furthermore, percentages of the knot strength to the dry strength of the unknotted rope, if estimated as 90% for the eye splice, become 45%, 50%, 55% and 85% respectively.

著者

吉野 博之 藤原 鉄弥 山本 勝太郎

出版者

公益社団法人 日本水産学会

雑誌

日本水産学会誌 (ISSN:00215392)

巻号頁・発行日

vol.76, no.5, pp.799-802, 2010 (Released:2010-11-01)

被引用文献数

1 1

著者

伊藤 敏晃 高木 力 平石 智徳 鈴木 健吾 山本 勝太郎 梨本 勝昭

出版者

日本水産工学会

雑誌

水産工学 (ISSN:09167617)

巻号頁・発行日

vol.32, no.1, pp.39-43, 1995-07-31

被引用文献数

2

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北海道では、エゾバフンウニやキタムラサキウニなどのウニ類を対象とし、種苗放流や、漁場造成によって資源を増加させようとする栽培漁業が積極的に推進されているが、地域によっては十分な成果が得られていない。その原因として波浪による稚ウニの打ち上げ、餌料の不足や海水交換の不良による死滅があげられる。これを防ぐために比較的静穏な海域に、稚ウニを集約的に放流し、給餌を行って育成する場を造ること、ウニが散逸しないようなフェンスを設けることなどが提案されている。また、ウニの食害による磯焼け現象が進むことも懸念されているため、ウニの行動領域を制限する安価で耐久性のあるフェンスの開発が強く要望されている。このようなウニ用フェンスを開発するためにはまずウニの行動特性を解明する必要がある。ウニの移動は管足先端部を付着基質に吸着させて管足全体を収縮させることによって行われるが、生態・行動学の分野における詳細な研究は少ない。外国産のウニについてはBullockによるアメリカムラサキウニの移動についての報告などがあるが、エゾバフンウニ、キタムラサキウニの行動学的な研究は非常に少ない。