To investigate the effect of non-metallic inclusions on the fatigue properties of quenched and tempered 0.46% carbon steel (HV≅650) in the super-long life fatigue range (N≤5.0×10⁸), tension-compression fatigue tests were carried out. The fatigue strength was discussed based on the √area parameter model.
The results obtained are:
(1) Fatigue fracture origins were mostly at a non-metallic inclusion.
(2) However, the locations of the inclusion at fracture origin were not uniformly distributed over the specimen section due to the nonuniform distribution of residual stress induced by heat treatment.
(3) The fatigue limit defined by the cycle N=5.0×10⁸ can be predicted by the √area parameter model, i.e. with three parameters, the Vickers hardness, HV, of the matrix, the square root of the projected area of inclusions, √area, and residual stress.
(4) The expected value of inclusion size √area_max of 0.46% carbon steel in a definite number of specimens can be estimated using the statics of extreme values. The lower bound of the scatter of fatigue strength was predicted with the combination of the √area parameter model and the value of √area_max.

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【はじめに】当院では、乳癌手術症例に対しクリニカルパス（以下パス）を作成し、術後1週間で退院するスケジュールで運用している。そこで、退院までの短期間に肩関節運動機能の回復と、日常生活活動（以下ADL）の再獲得が必要となったため、平成14年10月より乳癌術後のパスに合わせて、リハビリテーション部門独自のパス（以下リハビリパス）を作成し運用してきた。今回、リハビリパスの使用経験を若干の考察を加えて報告する。
【対象および方法】当院にて平成14年10月から平成15年10月までに、乳癌に対する手術を施行した女性入院患者36名、平均年齢56.2±12.1歳を対象とした。その内訳は胸筋温存型乳房切除術が14例、乳房温存術が22例であった。方法は、対象患者の術前および退院時の肩関節屈曲可動域（以下ROM）測定と術後入院期間を、乳房切除術と乳房温存術で調査しT検定にて比較検討した。
【乳癌術後リハビリパスの内容】乳房切除術と乳房温存術の2種類作成した。両パスとも術後1週間で退院予定とし、手術前日に理学療法オリエンテーションおよび理学療法評価を実施している。術後1日目は、肩関節より遠位の運動のみとし、術後2日目より肩関節運動を開始する。乳房温存術では、制限なく可及的にROM訓練を実施するのに対し、乳房切除術は術後2日目は屈曲90度までとし、その後段階的に改善を図っている。退院時にはADLに支障のないとされる屈曲160度を目標とし、達成困難であれば外来継続とする。
【結果】術後平均入院期間は乳房切除術7.9±2.0日、乳房温存術6.0±1.3日と優位に乳房切除術で長い結果となった（＜0.05）。肩関節屈曲角度は、乳房切除術術前平均161.4±24.4度で術後平均152.9±22.2度、乳房温存術術前平均171.8±13.3度で術後平均169.8±9.4度と、術後ROMは乳房切除術で優位に低下する結果となった（＜0.05）。退院時に目標角度に達しなかった症例は、乳房切除術で3例、乳房温存術で1例あり、外来継続を行った症例は、脳梗塞や肩関節周囲炎の既往歴がある乳房切除術の2例であった。
【考察】乳癌手術は肩関節に直接侵襲を加えないため、術後肩関節ROM制限の原因は、疼痛や恐怖心によるものが大きいとされている。今回、術前よりオリエンテーションを行うことで患者の恐怖心を軽減させ、理学療法士による運動療法により術後早期にADL再獲得が可能であった。乳房切除術は乳房温存術に比べ組織の切除量が多く、術後伸張痛が強くなるため術後ROMの低下と入院期間の延長が出現したと考える。今後、さらに入院期間の短縮化が予測される。そのため入院期間中のROM改善とADL再獲得が困難になると考えられ、退院後の運動指導の充実が課題と考える。

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【目的】肩腱板修復術後の筋力について、prerotational glide(以下pre R.G)、rotational glide(以下R.G )、postrotational glide(以下post R.G)の3相における筋トルク値の回復について検討した。
【対象】2000年6月から2002年6月までに腱板損傷にて手術を行い、6ヶ月以上追跡できた11例（男性2例、女性2例）である。平均年齢61.8±9.9歳　手術側は、右5例　左6例、術後追跡期間11.7±2.9ヶ月である。
【方法】肩の筋力測定には、バックレストが110°の椅子に体幹と骨盤をベルトにて固定し、測定機器CybexII+を用い肩屈曲と外転筋力を測定した。入力棹の軸は、肩90°挙上位と水平挙上位で肩峰の高さとし、入力棹は90度挙上し肘伸展位で把持させた。ダイナモメータの回転速度は、60°/秒とし内外旋中間位で測定した。測定に際し被検者には、2～3回のウォーミングアップを行い「できるだけ早く腕を動かすように」と口頭で指示し3回測定した。
肩屈曲トルク値は、pre R.Gとして伸展45°から屈曲60°までの最大トルク値と発揮角度R.G として屈曲80°から120°までの最小トルクと角度、post R.Gとして屈曲135°から180°までの最大トルク値と角度を計測した。肩外転トルク値は、pre R.Gとして外転0°から60°までの最大トルク値と発揮角度、R.G として外転80°から120°までの最小トルクと角度、post R.Gとして外転135°から180°までの最大トルク値と角度について計測した。
【結果】肩屈曲トルクは、pre R.Gで患側3.9±1.4Kgm、健側4.2±1.4Kgm、 R.Gで患側1.9±.0.8Kgm、健側2.5±0.8Kgm、post R.Gで患側2.3±1.0Kgm、健側2.8±1.1Kgmで、患側および健側ともR.Gと post R.Gはpre R.G より有意（p＜0.01）に低く、また患側RGは、健側RGに比して有意（p＜0.01）に低値であった。
　肩外転トルクは、pre R.Gで患側2.3±1.1Kgm、健側2.3±0.8Kgm、R.Gで患側0.9±.0.6Kgm、健側1.4±0.5Kgm、post R.Gで患側1.2±0.7Kgm、健側1.9±1.0Kgmであった。患側および健側ともR.Gと post R.Gはpre R.G より有意（p＜0.01）に低く、またRGとpost R.Gでは、患側が健側に比して有意（p＜0.01）に低下していた。
【考察】腱板修復術後の筋力回復は、pre R.G に比してR.Gやpost R.Gで不十分であり、損傷による廃用性障害や腱板の機能回復の遅延などが残存しているものと推察された。術後の理学療法は、長期にわたりR.Gやpost R.Gでの筋力強化の必要性が示唆された。

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The addition of alloy elements such as silicon, chromium and molybdenum is effective in the restraint of temper softening in martensitic steels. The martensitic steel containing such alloy elements is known to have excellent resistance to temper softening in low and high temperature tempering treatments. However, the effects of the compound addition and its mechanism have not yet been satisfactorily revealed. In this study, the effect silicon, chromium, and molybdenum on resistance to the temper softening of the medium-carbon martensitic steel was investigated. As a result, it is revealed that the temper softening resistance quantity is maximum at the tempering temperature 773 K in the martensitic steel containing silicon, chromium, and molybdenum; this is because of the miniaturization of cementite (θ) and clustering of (Cr,Mo,Mn) 2C. Moreover, it is revealed to form this cluster at a tempering temperature lower than the temperature at which the alloy carbide usually precipitates (823 K-873 K).

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Torsional fatigue tests under shear mean stress (τ_m) and tensile or compressive mean stress (σ_m) were carried out on the 0.47% C steel (JIS S45C) specimens containing an initial small crack. An initial small semi-elliptical crack was introduced by the preliminary tension-compression fatigue tests using specimens which contain a hole of 40 μ_m diameter. The initial branching angle of cracks that emanated from the initial crack tip was approximately ±70.5°to the initial crack plane, where the local tangential stress σ_o has the maximum value. The branched cracks eventually propagated perpendicularly to the plane where the range of normal stress has the maximum value, i.e. ±45°to the specimen axis. The torsional fatigue limit under mean stress is determined by the threshold condition for non-propagation of Mode I branched cracks emanating from the initial crack tip. The prediction method for torsional fatigue limit of specimens containing an initial small crack is proposed by the extended application of the √area parameter model with a combination of the maximum tangential stress (σ_omax) criterion.

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Since in superlong fatigue failure with N_f≥10⁸, the average fatigue crack growth rate is much less than lattice spacing (-0.1Å or 0.01nm or 10^-11--12m/cycle), we cannot assume that crack growth occurs cycle by cycle in the early stage of fatigue process.
In this paper, possible mechanisms for extremely high cycle fatigue are discussed. A special attention was paid to a newly found particular fatigue fracture morphology in the vicinity of fracture origin (nonmetallic inclusions) of a heat treated alloy steel, SCM435. The particular morphology looks a dark area inside fish-eye mark by optical microscopic observation. Specimens with short fatigue life of N=-10⁵ do not have such dark area in fish-eye mark. SEM and AFM observations revealed that the dark area has a rough surface quite different from usual fatigue fracture surface in martensite lath structure. The predictions of fatigue limit by the √area parameter model are -10% unconservative for fatigue limit defined for N=10⁷. Thus, the fatigue failure for N≥10⁸ is presumed to be caused by a mechanism which induces breaking or releasing of fatigue crack closure phenomenon in small cracks. The breaking or releasing crack closure mechanism is presumed to be caused by environmental effects such as hydrogen embrittlement coupled with extremely high cycle fatigue. Some indirect evidences to support this hypothesis are shown.

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Reversed torsional fatigue tests were carried out on the 0.47%C steel specimens containing an initial small crack. The initial small semi-elliptical cracks ranging from 200μm to 1000μm were introduced by the preliminary tension-compression fatigue tests using specimens which contains a hole of 40μm diameter. The crack growth behaviour from a semi-elliptical surface crack was investigated. The effects of artificial small defects on torsional fatigue strength are also reviewed in relation with those of small cracks. The conclusions are summarized as follows:
(1) In rotating-bending and tension-compression fatigue, the effects of artificial small defects and small cracks are identical from the viewpoint of fatigue limit. However, in torsional fatigue these effects are not identical.
(2) Cracks leading to fracture were Mode I branched cracks initiated at crack tips. Initiation of Mode II cracks at the pre-crack tip was also observed in most cases in addition to Mode I branched cracks. However, these cracks stopped propagating as the Mode I branched cracks propagated.
(3) Torsional fatigue limit for a semi-elliptical small cracks is determined by the threshold condition for non-propagation of Mode I branched cracks.
(4) Torsional fatigue limit of specimens containing a small crack can be successfully predicted by the √area parameter model with a combination of σ_θmax criterion.

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This paper discusses the questions of how scholars in the media and communication research fields can contribute to society after its being damaged by the Great East Japan Earthquake and tsunami that occurred on 11 March, 2011. Defined mainly by the explosion of the nuclear power station in Fukushima, it was a disaster that divided Japanese history into everything that happened before and everything that happened after it, raising radical questions concerning the advancement of science and technology in the modern era. As an academic association with a history of 60 years and more than 1,000 members, the Japan Society for Studies in Journalism and Mass Communication has taken the initiative through the holding of workshops and symposiums in tackling such themes as risk communication at times of disaster and corporate media's role and social responsibility in the face of unprecedented disasters. However, what has been decidedly lacking so far is the critical reflection of the approaches implemented to conduct communication research in the disaster-stricken areas, or the evaluation of how research results affect the flow of actual information and communication activities within local communities. While outlining some of the characteristics of this catastrophe, I argue that we should pursue an interdisciplinary and pragmatic approach based upon interaction with people at disaster-stricken sites in order to meet the critical needs of those most in need, and engage with a wide variety of subtle, local problems in the disaster-stricken areas. In addressing the challenges we face in the area of media and communication research, I also mention present difficulties in accessing past television data in Japan, which prevents us from conducting systematic research on television. The media's reluctance to make television data available for the use of research constitutes a serious obstacle to scholarly advancement in this field.

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Gigacycle fatigue characteristics of high speed tool steel, JIS SKH 51, was investigated under cantilever-type rotary bending fatigue tests in an open environment at room temperature. As a result of fatigue tests, S-N curve was clearly classified into two types of fracture modes by the different crack origins. One fracture mode occurred at the surface inclusion in the region of short fatigue life and high stress amplitude level. The other was at the subsurface inclusion in the region of long fatigue life and low stress amplitude level. The transition of crack initiation site from surface to subsurface appeared at about 2×10⁴ cycles and the stress amplitude for the transition was affected by the tempering temperature of the specimen. On the other hand, difference on fatigue life for internal fracture mode between specimens treated by different tempering temperature did not observed. Fatigue fracture mechanisms were discussed through the detailed observation of subsurface crack initiation site.

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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≅170) and quenched and tempered (HV≅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.

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