Fatigue Strength of Age-Hardened Al-Zn Alloys under Repeated Tensile Loading

Effect of the soft surface layer that was formed on low temperature aging of Al-Zn alloy on fatigue strength was studied under repeated tensile loading. Vickers microhardness test revealed that there existed less hardened region in the vicinity of grain boundary and surface, and that the region extends 50 to 100μm from the surface inward. From the plot of the stress amplitude against the number of cycles to failure, it is concluded that the presence of less hardened surface layer strengthens fatigue resistance of the age hardened Al-Zn alloys containing 8 to 16mass % Zn under the repeated tensile loading

Characteristics of solar flare effect in the high-latitude ionosphere as observed by the SuperDARN radars

Sudden perturbations of the ground magnetic fields at solar flares are called geomagnetic Solar Flare Effect (SFE). An SFE is the extra ionization produced by the X-ray emission from a solar flare. We analyzed 10 intense SFE events from 1996 to 1998 using SuperDARN HF radar network and other instruments located in the northern hemisphere. Two typical ionospheric signatures associated with the solar flares are revealed, one is a sudden fade-out of backscatter echoes, and the other is an appearance or variation of field-aligned irregularities. Sudden fade-out is observed only in the sunlit hemisphere, and the appearance or variation of irregularities are observed only near the terminator. In addition, we investigated one event out of ten in detail and found that there exists a discontinuity of the electric field or conductivity around the irregularity. This fact suggests that the variation of conductivity or electric field in the E region could affect the irregularity formation in the F region

Simultaneous ground-satellite observations of meso-scale auroral arc undulations

第2回極域科学シンポジウム/第35回極域宙空圏シンポジウム 11月16日（水） 統計数理研究所 3階リフレッシュフロ

Mult-wavelength, simultaneous observations of auroras at South Pole and McMurdo stations

The Tenth Symposium on Polar Science/Special session: [S] Future plan of Antarctic research: Towards phase X of the Japanese Antarctic Research Project (2022-2028) and beyond, Tue. 3 Dec. / Entrance Hall (1st floor) at National Institute of Polar Research (NIPR

Effect of Specimen Thickness on Aging and Fatigue Strength of Al-Zn Alloys

Repeated tensile fatigue strength of the low temperature age-hardened Al-Zn alloys is investigated varying the specimen thickness. Fatigue strength of the age-hardened specimens decreases with the specimen thickness when the specimen is thinner than a certain thickness, whereas fatigue strength of non age-hardened specimens, i.e., pure aluminum and dilute Al-Zn alloy, does not depend the specimen thickness. The dependence of fatigue strength on the thickness of age-hardened specimen is considered to be caused by the decrease of the strength of specimen as a whole, as a result of increase in volume ratio of the soft surface layer formed after age-hardening with decreasing specimen thickness

砥石作業面のインプロセス測定による研削作業の最適化に関する研究

本研究は,砥石作業面を加工目的に応じた最適な状態に維持することによって研削加工を最適化しようとするもので,(1)砥石作業面を機上測定できるシステムの構築;(2)加工目的に応じた砥石作業面の生成;(3)砥石作業面性状の定量化;(4)砥石作業面性状のインプロセス測定;という研究計画からなっている.最も使用頻度が高い超砥粒砥石およびビトリファイドアルミナ砥石を対象として行った研究成果を以下に示す.(1)砥石作業面を直接測定する\u27静的手法\u27として,触針式粗さ計(触針法)およびデジタルイメージスコープ(画像処理法)を研削盤の砥石ヘッドに装着して砥石作業面を観測するシステムを構築した.その結果,超砥粒砥石に対し,形直し・目直し直後の初期研削工程における砥粒先端の微小破壊による切れ刃の増加,切れ刃先端の摩滅摩耗,結合剤の除去によるチップポケットの増大などの過度的過程を詳細に観測することに成功し,定常研削へ移行する時期を正確に評価できた.(2)\u27動的手法\u27として,ドレス条件を段階的に変えて異なった状態の砥石(標準状態)を生成し,それらの砥石から発生する研削音や研削振動の特徴をニューラルネットワークによって学習・識別するシステムを構築した.その結果,研削抵抗や仕上面粗さに明確な差が生じる程度に相違がある場合には,砥石作業面状態は精度よく識別できることがわかった.また,標準状態以外の状態を入力した場合,ネットワークは最も近い標準状態を出力した.さらに,摩耗した砥石から研削音を入力した場合,ドレッサ送り速度が小さく砥粒先端がより平坦化した標準状態を識別結果として出力した.このことから,本手法には柔軟性があり,使用する砥石ごとにいくつかの標準状態をあらかじめ学習させることによって,インプロセスで砥石の状態を評価することができることを示した.The purpose of this study is to optimize the grinding operation by means of in-process measurement of the wheel surface. The outlines of the project are as follows.(1) Construction of the in-situ wheel monitoring system.(2) Characterization of the wheel surface corresponding to the measure ring method.(3) In-process evaluation of the wheel surface.Parameters for characterizing grinding wheel surface are classified into two categories : static and dynamic parameters. In the post-process static evaluation, the wheel surface is directly measured by means of the stylus profilometry and the microscopy. The circumferential profile trace and 2D-image of a wheel surface is measured by the stylus profilometer and the digital microscope, respectively. Here abrasive grains and cutting edges are identified according to arbitrarily defined criteria. The grain density, cutting-edge density, successive cutting-edge spacing, cutting-edge ratio and micro-morphology of abrasive grains can be measured wi th a good degree of accuracy. This technique enables to measure the wheel topography relatively easily so that it has the possibility to control the grinding operation by judging the suitability of the grinding condition and the timing of re-arrangement of the wheel.In the in-process dynamic measurement, on the other hand, the wheel condition is evaluated by analyzing the grinding sound, which is generated by the wheel-work interaction in the grinding zone. Several reference conditions of the wheel surface are formed by the appropriate dressing and the frequency spectrums of grinding sound emitted from the reference wheel surface are discriminated by the neural network learning algorithm. The overall recognition rate is at least 60%. The network also recognize the wheel wear as the wheel surface with flattened grain tips, which is equivalent to that of the wheel generated with lower dressing feed. Accordingly this system can recognize instantaneously the difference of the wheel surface.研究課題/領域番号:10650117, 研究期間(年度):1998-2000出典：「砥石作業面のインプロセス測定による研削作業の最適化に関する研究」研究成果報告書　課題番号10650117 (KAKEN：科学研究費助成事業データベース（国立情報学研究所）)　　　本文データは著者版報告書より作

砥石作業面のレーザコンディショニングを併用した研削焼入れの実現

(1)レーザによるメタルボンドダイヤモンド砥石作業面のコンディショニングに関する研究砥石作業面の状態を最適化するコンディショニングには,(1)結合剤を除去して砥粒を突き出させるドレッシング,(2)砥粒先端を成形して高さを整えるツルーイング,(3)目づまりを取り除くクリーニングがあるが,平成19年度は平成18年度に引き続き(1)のドレッシングを行うとともに,(2)に取り組んだ.まず(1)については,レーザと同時にエアジェットを砥石作業面に照射することによって,レーザの熱エネルギーで溶融した結合剤を吹き飛ばして効率的なドレッシングが可能なことを示した.H19年度はレーザの砥石表面からの反射光によるレーザヘッドへの熱損傷を防ぎ且つレーザとエアジェトの照射点を高精度に一致させるため,レーザ・エアジェット一体型照射ノズルを開発した.これにより任意の照射角度でのドレッシングが可能になり,実用化に向けて一歩前進した.一方,(2)のツルーイングは電着ダイヤモンド砥石を用いて行ったが,ダイヤモンド単結晶がYAGレーザ(λ=1μm)や半導体レーザ(λ=0.8μm)を透過することから,レーザエネルギーを効率的に熱に変換してダイヤモンド砥粒を除去することは難しい.ただし,一定の条件化では砥粒先端が黒鉛化し,この黒鉛層は容易に除去できるため,レーザ照射と研削加工を同時に行うレーザアシストツルーイングの可能性をみいだした.(2)研削熱を利用した鋼材の表面改質加工法(研削焼入れ)に関する研究クロム・モリブデン鋼を対象とした円筒外周プランジ研削での研削焼入れを行い,表面硬化加工法として有効であることを確認した.硬化深さに最も影響を及ぼすのは砥石切込み速度で,切り込み速度100μm/sで硬化層深さ160μmを得ることができる.一方,トラバース研削では,砥石幅と送り(mm/rev)を同一にし,工作物の同一箇所を重畳して研削しないようにすることで局部的な焼き戻しを回避し,ほぼ一様に焼入れを施すことが可能になる.実用的なレベルの焼入れ層深さを確保するためには,より剛性のある工作機械が必要である.In general, grinding heat canoes various types of thermal damage to the workpiece, such as burning, cracks, and phase transformation. In this study, the grinding operation is regarded as. a heat treatment process called Grind-hardening. This new heat treatment method enables the phase transformation from austenite to martensite in the surface layer of steels. The cylindrical grinding tests at several infeed rates are carried out A clear hardened layer is observed, where the martensitic structure is formed having the hardness of 700HV when the infeed rate is larger than 40μm/s. The depth of hardened layer increases as infeed rate increase. The hardened layer of approximately 0.16 mm is attained in plunge grinding of chrome-molybdenum steel SCM435. The oxidized film at the ground surface layer can be removed by the spark-out grinding and this process makes the surface smooth and good circularity of the workpiece.As the second approach, laser beam is used as a noncontact thermal dressing tool of a bronze bond diamond wheel. The pulsed-Nd:YAG laser beam is aligned in the normal direction and focused on the wheel surface The linear stage is fed in the axial direction and this motion is coordinated with the wheel rotation, laser pulse frequency and pulse duration so as to cover the overall wheel surface by laser beam The bond material is partially removed by laser irradiation only, in which melting and vaporizing take place. In order to efficiently remove the hand material, it is necessary to spray air jet on the laser irradiating spot so as to blow away the molten binder before it solidifies again less damage of diamond particles such as micro-cracks or graphitization is observed. In order to evaluate the grinding performance of a laser-dressed wheel, the plunge grinding tests of engineering ceramics are carried out The grinding forces are almost the same as the ordinary dressed wheel, and they are roughly kept constant up to 50 mm3/mm in stock removed per unit width of cut This shows that the diamond grits are anchored firmly in the bond without thermal deterioration_ Consequently, the effective laser dressing is expectable with the appropriate dressing conditions. For the purpose of practical use, the integrated laser-air head is designed in which laser beam and air jet are shot on the same axis. In grinding with the laser-dressed wheel, the grinding faces are almost the same as those for the conventionally dressed wheel.研究課題/領域番号:18560100, 研究期間(年度):2006-2007出典：「砥石作業面のレーザコンディショニングを併用した研削焼入れの実現」研究成果報告書　課題番号18560100 (KAKEN：科学研究費助成事業データベース（国立情報学研究所）)　　　本文データは著者版報告書より作

Visible-light-assisted selective catalytic reduction of NO with NH[3] on porphyrin derivative-modified TiO[2] photocatalysts

Accepted 16 Sep 2014.Porphyrin-derivative-modified TiO[2] photocatalysts showed high photocatalytic activity for the selective catalytic reduction of NO with NH[3] in the presence of O[2] under visible-light irradiation. Tetra(p-carboxyphenyl)porphyrin (TCPP) was the most effective photosensitizer among the five porphyrin derivatives investigated. NO conversion and N[2] selectivity of 79.0% and 100%, respectively, were achieved at a gas hourly space velocity of 50 000 h[−1]. UV–Vis and photoluminescence spectroscopies revealed the presence of two species of TCPP on the TiO2surface; one was a TCPP monomer and the other was an H-aggregate of the TCPP molecules. It was concluded that the TCPP monomer is an active species for the photo-assisted selective catalytic reduction (photo-SCR). Moreover, an increase in the fraction of H-aggregates with increasing TCPP loading amount resulted in a decrease in the photocatalytic activity of the photo-SCR

Observations of large flow shears around small-scale auroral beads observed at substorm onset

第2回極域科学シンポジウム/第35回極域宙空圏シンポジウム 11月16日（水） 統計数理研究所 3階リフレッシュフロ

Characteristics of polar mesosphere summer echoes observed with oblique incidence HF radars at Syowa Station

Polar mesosphere summer echoes(PMSE) are strong VHF-UHF radar echoes from the high-latitude cold mesopause at around 80-90km altitudes in summer. Although a number of in situ and radar observations of PMSE have been made until now, generation mechanisms of PMSE and scattering processes of radar waves due to PMSE-associated irregularities are still controversial. In this paper, PMSE detected for the first time in December 1997 and January 1998 with the oblique incidence SuperDARN HF radars at Syowa Station, Antarctica(69.0°S , 39.6°E ), are summarized to reveal the characteristics of PMSE at HF band. They appear at slant ranges of 180-315km with elevation angles of 15°-30° between 1030 and 1230UT or between 2100 and 0140UT, and are characterized by durations of 65-110min with intermittent subsidence and quasi-periodic oscillations of echo power with periods of 5-20min, due to short-period atmospheric gravity waves. Detailed analysis of the December 15, 1997 event reveals the followings: 1) echo power is less than 30dB, Doppler velocity between -40 and +40m/s, and spectral width less than 50m/s, respectively, 2) there exists no particular correlation among power, velocity and width, and 3) PMSE occurrence can be related to eastward neutral wind due to semi-diurnal tide that may induce the decrease in the mesospheric temperature