著者

村上 敬宜 町田 尚 宮川 進 髙城 壽雄

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.853, pp.17-00231-17-00231, 2017 (Released:2017-09-25)

参考文献数

29

被引用文献数

4

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Recently, recalls for mass production products such as car components have been frequently reported even for the case that the rate of defects is only of the order of ppm or less. The objective of this paper is to propose the solution to avoid the recall problem of the order of ppm for mass production products. Even if the defect rate is of the order of ppm or less, most of remaining safe products have to be recalled and be replaced by new components. Such a recall causes a great cost deficit if the very rare defect is possibly related to fatal accident. However, it is very difficult by the conventional quality control methods to find the defects of the order of ppm or less at the stage of design and production. This paper proposes a new practical quality control method to avoid the defects of the order of ppm or less for mass production products based on the statistics of extremes which has been successfully applied to fatigue strength evaluation of defective materials. First, several examples of the quality control method to avoid the troubles mainly caused by failures and damages of components will be presented. Next, it will be shown that the same approach also can be applied to other problems such as the optimum control of operational parameters and the selection of optimum materials through the index based on the statistics of extremes. It will be also shown that the same method can be applied not only mass production components but also to avoid the troubles and failure accidents for large machine components of small number production. The stress-strength model approach will be reviewed from the viewpoint of the statistics of extremes.

著者

周 世栄 村上 敬宜 福島 良博 ベレッタ ステファノ

出版者

社団法人日本鉄鋼協会

雑誌

鐵と鋼 : 日本鐡鋼協會々誌 (ISSN:00211575)

巻号頁・発行日

vol.87, no.12, pp.748-755, 2001-12

被引用文献数

2

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It is well known that the scatter of fatigue strength of high strength steels is caused by nonmetallic inclusions. The lower bound of the scatter of fatigue strength can be predicted by considering the maximum size of nonmetallic inclusions. Thus, it is of practical importance to estimate the maximum size of nonmetallic inclusions by appropriate inclusion rating methods. Most rational and convenient method to predict the maximum size of inclusions is the one based on the statistics of extremes. Therefore, recently the inclusion rating based on the statistics of extremes has been used by many industries, though the rating methods are mostly two-dimensional (2D) optical methods. It is known that the accuracy of the 2D method is lower than the exact 3D method. In addition, when multiple type inclusions having different chemical composition are contained in a material, the statistics of extremes distribution does not necessarily become a single straight line but become a bilinear line. The objectives of the present study are (1) to clarify the validity of the 2D method and (2) to establish the method to predict the maximum inclusion size when the statistics extremes distribution becomes bilinear. The results obtained show that the 2D method is basically correct as predicted by the computer simulation. When a bilinear distribution is obtained, it is necessary to determine the minimum inspection area S_<crit> for predicting the maximum size of the larger type inclusions, which become the fatigue fracture origins of components.

著者

村上 敬宜 高橋 宏治 山下 晃生

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 A編 (ISSN:03875008)

巻号頁・発行日

vol.63, no.612, pp.1612-1619, 1997-08-25 (Released:2008-02-21)

参考文献数

21

被引用文献数

10 43

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In order to investigate the effect of surface roughness on fatigue strength, fatigue tests for a medium carbon steel, which was annealed and free of residual stress (HV&cong;170) and quenched and tempered (HV&cong;650). were carried out. To simulate the actual surface roughness, extremely shallow periodical notches with a constant pitch but irregular depth were introduced. The equivalent defect size √(area)R for roughness was defined to evaluate the effect of irregularly shaped roughness using the √(area) parameter model. The fatigue limits of the annealed medium carbon steel specimens with artificial surface roughness are much higher than those of the specimen with a single notch because of the interference effect of notches. The fatigue limits predicted by the √(area) parameter model are in good agreement with the experimental results.

著者

宮本 昭彦 村上 敬宜

出版者

公益社団法人 日本材料学会

雑誌

材料 (ISSN:05145163)

巻号頁・発行日

vol.47, no.8, pp.830-835, 1998-08-15 (Released:2009-06-03)

参考文献数

7

被引用文献数

1 1

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On crime scenes, plate glass is frequently shot by bullets. The fracture of plate glass by a pachinko ball (steel ball) impact also occurs. Experiments were carried out to obtain basic data for estimating the impact velocities of projectiles from the morphology of the fracture. Projectiles {11mm dia. steel balls and 0.38 inch (9mm dia.) lead bullets} were shot onto ordinary glass plates firmly held around a circular periphery.It was assumed that projectile kinetic energy would all be converted into surface energy of fractured glass. The relationship between crack area Af and kinetic energy of projectiles was investigated. A strong experimental correlation was found between Af and the change in kinetic energy. A unique relationship was obtained between crack area and energy consumed during fracture regardless of the projectile material (steel and lead).

著者

村上 敬宜 金崎 俊彦 福島 良博 田中 裕之 戸室 仁一 久保山 孝治 松栄 雅樹 伊藤 義雄 安藤 晴彦

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 A編 (ISSN:03875008)

巻号頁・発行日

vol.75, no.749, pp.93-102, 2009-01-25 (Released:2017-06-09)

参考文献数

6

被引用文献数

4 7

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The fatigue failure analysis of SUS316L flexible hose of the hydrogen station which was demonstrated during EXPO 2005 in Nagoya was carried out. The fatigue fracture surface where hydrogen leakage was detected showed clear striations which revealed a unique evidence of hydrogen effect on the ratio of striation height and spacing. The number of striations observed on the leakage fracture surface was 270. Considering that the number of hydrogen supply to the fuel cell buses was 280, it can be concluded that the fatigue fracture process during the demonstration is completely controlled by microplasticity resulting ductile fracture contrary to the conventional concept expressed with a term of decohesion or hydrogen embrittlement. The striation data were used to make the fatigue crack growth rate equation which was applied to the life prediction and structural integrity assessment for a new hydrogen station. The fatigue crack growth data showed the evidence of a strong frequency effect of fatigue crack growth rate of SUS316L used in the hydrogen environment with 8 minutes hydrogen supply time at the hydrogen station.

著者

村上 敬宜 遠藤 正浩

出版者

公益社団法人 日本材料学会

雑誌

材料 (ISSN:05145163)

巻号頁・発行日

vol.35, no.395, pp.911-917, 1986-08-15 (Released:2009-06-03)

参考文献数

67

被引用文献数

28 57

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The dependence of ΔKth on crack size and material properties under stress ratio R=-1 was studied on various materials and microstructures. The values of ΔKth for all the materials investigated were standardized with one geometrical and one material parameter.The geometrical parameter, √area, is the square root of the area which is occupied by projecting defects or cracks onto the plane normal to the maximum tensile stress. The relationship between ΔKth and √area is expressed as follows:ΔKth∝(√area)1/3 (a)The most relevant material parameter to standardize the data was the Vickers hardness, and the following relationship was obtained:ΔKth∝(HV+C) (b)The constant C in Eq. (b) reflects the difference of nonpropagation behavior of small cracks in soft and hard metals.By combining Eqs. (a) and (b), the following equations were derived for predicting ΔKth and the fatigue limit σω of cracked members.ΔKth=3.3×10-3(HV+120)(√area)1/3 (c)σω=1.43(HV+120)/(√area)1/6 (d)where the units are ΔKth: MPa·m1/2, σω: MPa, √area: μm and HV: (kgf/mm2). Equations (c) and (d) are applicable to a crack having √area approximately less than 1000μm.

著者

橋村 真治 村上 敬宜

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 C編 (ISSN:03875024)

巻号頁・発行日

vol.68, no.671, pp.2137-2144, 2002-07-25 (Released:2008-02-26)

参考文献数

8

被引用文献数

3

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The clamping force of a bolted joint is usually controlled by torque or angle at tightening. However the fatigue failure of bolted joints occures if the clamping force is loosened in service. Therefore the clamping force in service after tightening must be checked to avoid failure of bolted joints. In this study, a new method to detect the clamping force of bolted joints after tightening has been proposed, in which the clamping force is detected by pulling the protruding thread of the bolt through the nut on a bolted joint. The relationship between the pulling force and the displacement at the pulling point is measured to detect the apparent spring constant of the bolt. When the pulling force reaches the clamping force of bolted joint, the apparent spring constant varies markedly. Thus the clamping force of the bolted joint can be defined on the basis of the variation of the apparent spring onstant. The basic theory and the experimental verifications are presented.

著者

野田 尚昭 安達 修平 柳下 誠 村上 敬宜

出版者

九州工業大学

雑誌

九州工業大学研究報告. 工学 (ISSN:04530357)

巻号頁・発行日

vol.71, pp.9-13, 1999-03

著者

村上 敬宜 横山 ナンシー尚子 高井 健一

出版者

社団法人日本材料学会

雑誌

材料 (ISSN:05145163)

巻号頁・発行日

vol.50, no.10, pp.1068-1073, 2001-10-15

被引用文献数

10 23

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The mechanism for fatigue failure in extremely high cycle fatigue in the regime of <i>N</i>>10⁷ is studied on a bearing steel, JIS SUJ2. Special focus was given to the fracture morphology in the vicinity of fracture origin (subsurface nonmetallic inclusion) of a heat treated bearing steel (Specimen QT). The particular morphology looks dark during optical microscopic observation. Specimens with short fatigue life of the order of <i>N_f</i>=10⁵ did not have such a dark area, ODA (optically dark area). To investigate the influence of the hydrogen trapped by nonmetallic inclusions on fatigue properties, specimens heat treated in a vacuum followed by quenching and tempering (Specimen VQ) were prepared. Specimens VQ contained 0.07ppm hydrogen as compared to 0.80ppm hydrogen for conventional Specimens QT. Specimens VQ had a slightly smaller ODA than Specimens QT. Hydrogen was detected by a Secondary Ion Mass Spectrometer around the inclusion at fracture origin of Specimens QT and Specimens VQ. Thus, it can be concluded that the formation of ODA is closely related to hydrogen trapped by nonmetallic inclusions. Estimations of fatigue limit by the √<i>area</i> parameter model based on the original size of inclusions for fatigue limit defined for 10⁷ cycles are -10% unconservative. Considering the size of ODA into fatigue limit estimation, the √<i>area</i> parameter model can predict the mechanical fatigue threshold for small cracks without influence of hydrogen. The mechanism of duplex <i>S-N</i> curve is also discussed.

著者

文部科学省科学技術学術政策局基盤政策課 村上 敬宜

出版者

時評社

雑誌

大学と学生 (ISSN:02864657)

巻号頁・発行日

no.63, pp.54-59, 2009-01

著者

金崎 俊彦 楢崎 千尋 峯 洋二 松岡 三郎 村上 敬宜

出版者

一般社団法人日本機械学会

雑誌

日本機械学會論文集. A編 (ISSN:03875008)

巻号頁・発行日

vol.72, no.723, pp.1717-1724, 2006-11-25

被引用文献数

11 17

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The effect of hydrogen on fatigue crack growth behavior of four stainless steels has been investigated from the viewpoint of martensitic transformation. The crack growth rates in hydrogen-charged SUS304 and SUS316 were accelerated. The crack growth rate in hydrogen-charged SUS316L was slightly higher than uncharged SUS316L. However, the crack growth rate in SUS405 hardly changed in comparison with uncharged specimens. The matensitic transformation on fatigue fracture surface was detected by X-ray diffraction both in hydrogen-charged and uncharged specimens of SUS304, SUS316 and even in SUS316L. However, the fracture surface of SUS316L, in which the crack growth rate was increased slightly by hydrogen, showed less martensitic transformation than that of SUS304 or SUS316. It is presumed that martensitic transformation in the vicinty of fatigue crack tip contributed to the effect of hydrogen on crack growth rate. Fatigue tests of SUS304 and SUS316L, which were pre-strained at -70℃ to enhance a martensitic transformation, were carried out to study the influence of hydrogen and martensite on crack growth. Crack growth rate was remakably increased by hydroggen in not only pre-strained SUS304 but also in pre-strained SUS316L. The hydrogen content of pre-strained hydrogen-charged specimen was much higher than unstrained hydrogen-charged specimens due to the increase in martensite through which hydrogen diffuses much easier and faster than through austenite. The slip bands around crack tip in the hydrogen-charged specimens were less and more discrete than that in the uncharged specimens.

著者

村上 敬宜 堤 一也 藤嶋 正博

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. A編 (ISSN:03875008)

巻号頁・発行日

vol.62, no.597, pp.1124-1131, 1996-05-25

被引用文献数

15 19

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In order to investigate the effect of surface roughness on the fatigue strength, fatigue tests for maraging steel which was subjected to aging treatment and was free of residual stress, were carried out. As an artificial surface roughness, extremely shallow periodical notches with notch radii P=0 and 200μm, and notch depths a=12, 22, 40 and 65μm were introduced. In addition to the effect of surface roughness, the effect of nonmetallic inclusions was also considered. The equivalent defect size (√(area<SUB>R</SUB>)) which controls the fatigue limit of specimen containing the surface roughness is defined by the function of depth and Pitch of the roughness. The lower bound of the fatigue limit for various levels of roughness can be predicted by substituting the equivalent maximum defect size (√(area<SUB>m</SUB>axt)) to the √(area) parameter model. The value of √(area<SUB>m</SUB>axt) can be evaluated by considering the interaction effect between the maximum inclusion size and roughness. The predicted values were examined by experiments and it is shown that the method of prediction is available for practical applications.