In order to investigate the influence of peening on the surface durability of case-hardened steel gears, the case-hardened steel gears -peened with different velocities and diameters were fatigue-tested using a power circulating type gear testing machine. The hardness, the compressive residual stress and the surface roughness of the gears were increased by peening. The cause of failure of all the test gears was pitting due to surface cracking. The surface durability of the gear -peened under medium condition in this experimental range was higher than that of the non-peened gear. On the other hand, that of lightly or strongly -peened gear was just as high. Judging from the p_max-N curves and also the [A(σ_y/H_V)]_max-N curves, it is denoted in this experimental range that the surface durability of case-hardened steel gears was influenced by the hardness and the surface roughness of the gears. Therefore, it is proposed in this experimental range that the medium peening condition, that is, 60m/s velocity and 0.6mm diameter, should be selected in order to improve the surface durability of case-hardened steel gears.

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The present study describes the effect of heat treatment of functional graded material fabricated by fine particle peening treatment that is one of the surface modifications. Fine tungsten carbide particles accompanied with steel beads were penetrated on the target alloy steel surface by peening. Heat treatment was applied after the peening to melt and infiltrate of the penetrated tungsten carbide into the alloy steel. Results of indentation measurements showed that an applicable heat treatment was effective to improve the hardness. A thrust type rolling contact experiment was also applied to the modified surface, superior anti wear properties were found in the heat treated specimen.

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The present study describes the effect of heat treatment of functional graded material fabricated by fine particle peening treatment. Fine tungsten carbide particles accompanied with steel beads were penetrated on the target alloy steel surface by he peening. Heat treatment was applied after the peening to diffuse of the penetrated tungsten carbide into the alloy steel. Results of indentation measurements showed that an applicable heat treatment was effective to improve the hardness. A thrust type rolling friction experiment was also applied to the modified surface, a superior anti wear properties were found in the heat treated specimen.

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Two simple differential-type monostable multivibrators are proposed and demonstrated in this letter, where the first configuration operated under positive triggering mode utilizes EX-OR gates and the second configuration operated under negative triggering mode employs EX-NOR gates. Both realization methods make use of CMOS logic gates connected with a few passive elements to form as switching circuits. Experimental results show that the ranges of the output pulse widths are from several microseconds to milliseconds.

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In our previous algorithm, we proposed a home video summarization using importance. importance is defined by the duration and motion activity. The more important the is, the more number of Representative frames (R-frames) is retrieved. However, when the event of all shots are unrelated. It is desired to receive more information from more shots. In this paper, we propose an improved algorithm of our previous work. Our algorithm allows user to select the number of to be appeared in the summarized video. The experiment shows that our algorithm gives an acceptable summarized result.

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リュッツォホルム岩体は、中dP/dT変成コンプレックスで、東側から西側へ、角閃岩相～超高温変成岩へ変成度が高くなる累進変成地域である（Hiroi et al., 1991など）。その変成ピーク時期はジルコンU-Pb年代から600～500 Ma頃とされている（Dunkley et al., 2020）。天文台岩はプリンスオラフ海岸の1 km × 3 km程度の露岩で、角閃岩相と、角閃岩相・グラニュライト相漸移部のちょうど境界部にあたる（Shiraishi et al. 1984）。

　本研究は、第35次南極地域観測隊の調査において、天文台岩で採取した１個の岩石サンプル（TMD40）の解析結果である。TMD40は肉眼的には均質な岩石で、弱い片麻状構造をもつ。主としてザクロ石、スピネル（ヘルシナイト）、黒雲母、珪線石、斜長石、カリ長石、石英、イルメナイト、ルチルで構成され、少量の白雲母、アパタイト、ジルコンを含む。スピネルは石英と接することはなく、斜長石とシンプレクタイトをなして産する。

　鏡下の組織と鉱物化学組成などから、TMD40の変成ステージは、Stage-I（昇温期）、Stage-II（温度ピーク）、Stage-III（後退期）に分けることができる。これをさらに細分し、温度ピーク以降の変成ステージは以下のように区別することができる。

Stage-II:　ザクロ石斑状変晶のマントルの高X_Mg部と、Grt + Sil + Kfsの共生時期。

Stage-IIIa:　Grt + Kfs + H₂O = Bt + Sil、およびGrt + Rt = Ilm + Sil + Qzの反応により、ザクロ石斑状変晶が分解され始める時期。

Stage-IIIb:　スピネルの出現で定義され、Grt + Sil + Spl + Plの4相が共存する時期。

Stage-IIIc:　ザクロ石の消滅で定義され、ザクロ石に隣接するpressure shadowにBt + Msが形成される時期。

　Stage-IIの温度圧力条件は、ザクロ石斑状変晶とその包有物などとの共生関係に基づき、GASP圧力計やGRIPS圧力計などから得られ、800～840 ℃で800 MPa程度の圧力である。Stage-IIIaの圧力は、ザクロ石斑状変晶にIlm + Sil + Qzのドメインが湾入して形成されている組織に基づいて得られ、GRAIL圧力計により求めることができる。800 ℃で650 MPa程度である。Stage-IIIbの圧力は、Spl + Plシンプレクタイトの形成時期として、Grt-Sil-Spl-Pl圧力計（Shimura et al, , 2016; 志村ほか, 2021）から求めることができる。750 ℃で450 MPa程度である。

　Stage-IIIaの減圧組織は、もともとザクロ石とルチルが接していた場所に、

Grt + Rt = Ilm + Sil + Qz　・・・・・①

の反応が起きて形成されたことが読み取れる。一方、Stage-IIIbの減圧組織は、もともとザクロ石と珪線石が接していた場所に、

Grt + Sil = Spl + Pl　　・・・・・②

の反応が起きて形成されたことが読み取れる。①の反応が起きたドメインでは、ザクロ石斑状変晶は“薄膜状の石英”に囲まれ、ザクロ石と珪線石は直接には接しなくなり、基質から隔離されている。これにより、後の②の反応は起きていない。一方、②の反応が起きたドメインでは、ザクロ石やスピネルは斜長石に完全に囲まれ、基質から隔離されている。このためより後にザクロ石に接して白雲母や黒雲母が形成されていることはない。

　天文台岩の変成履歴は、Takamura et al. (2020)が苦鉄質変成岩で解析したように、時計回りの変成P-T-t経路であることが、泥質変成岩からも支持される。サンプルTMD40は、肉眼的にはほぼ均質な岩石にみえるが、ごく狭いドメイン内の反応前の組織や化学組成の違いにより、事後に形成される減圧組織が異なっている。この試料には、様々な段階の減圧プロセスが記録されている。

文献

Dunkley, D. J. et al. (2020) Polar Science, 26, 100606.

Hiroi, Y. et al. (1991) In: Geological evolution of Antarctica. Cambridge Univ. Press, 83–87.

Shimura, T. et al. (2016) Goldschmidt Conference 2016, abstract 2833.

志村俊昭 ほか (2021) 日本地球惑星科学連合2021年大会, SMP25-11.

Shiraishi, K. et al. (1984) Memoirs of NIPR Spec. Iss., 33, 126–144.

Takamura, Y. et al. (2020) Precambrian Research, 348, 105850.

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In photoacoustic imaging, laser power variation is one of the major factors in the degradation of the quality of reproduced images. A simple, but efficient method of compensating for the variations in laser pulse energy is proposed here where the characteristics of the adopted optical sensor and acoustic sensor were estimated in order to minimize the average local variation in optically homogeneous regions. Phantom experiments were carried out to validate the effectiveness of the proposed method.

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Several experiments were run to compare steel with glass on the characteristics of peened surface and surface layer. peening was performed on steel (0.45%C) by an air blasting machine. The results obtained from experiments are as follows : diameter of dent, surface roughness, hardness distribution, half width and surface residual stress produced by steel are from 5 to 70% more than by glass . The maximum hardness and the depth of work hardened layer by steel are from 4.4 to 8.7% and from 20 to 30% more than by glass respectively. Surface residual stress by glass is from -260 to -390 MPa and by steel is from -350 to -420 MPa.

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peening is applied to many manufactured parts to improve the fatigue strength of metals by introducing compressive residual stress near the surface. The distribution of compressive residual stress is mainly determined by diameter, velocity, angle of incidence, and peening time which affects coverage. In this study, the velocity was measured using particle image velocimetry (PIV) for shots fired at two different air pressures. The finite element method was used to analyze the residual stress distribution in a high strength aluminum alloy (A7075-T6) plate during peening. The was accelerated up to a standoff distance of approximately 200 mm from the nozzle outlet. The measured maximum velocity increased proportionally to the air pressure to the 0.59th power. The analyzed residual stress distributions using measured velocity with PIV through the thickness of the specimen agreed well with the measurements under two types of peening conditions with differing air pressure and angle of incidence. The velocity measurement technology and the numerical model for analysis of the peening residual stres were both validated in this study.

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peening, which imparts compressive residual stress, is a very effective means for improving the fatigue strength and is widely used for manufacturing process such as automobile industry and aircraft industry. In this study, with the aim of clarifying experimentally the microscopic residual stress distribution of a single dent by projecting a fine ceramic ball with a diameter of 3 mm onto an aluminum alloy material, and the existence of shear stress is clarified by triaxial stress analysis. Furthermore, the change of the residual stress distribution when multiple shots are given to the same position of single dent is also clarified. Obtained results are summarized as follows: (1) The central portion of the dent has a tensile residual stress in both radial and circumferential directions of the dent. A residual stress in the radial direction of the dent has a peak of compressive residual stress outside the dent mark, and a compressive residual stress is given up to an area up to about four times the dent diameter. On the other hand, a tensile residual stress is generated in the circumferential direction of the dent to the region of four times the dent diameter, and the peaks of the tensile residual stress are present on the central part of the dent and outer of the dent. (2) The macroscopic residual stress in the radial direction gradually changes to compressive stress in accordance with the number of projections, but does not change substantially in the circumferential direction. (3) As a result of triaxial stress analysis on a single dent, shear stress components σ₁₂ and σ₂₃ does not exist, but it became clear that shear stress σ₁₃ is generated at the dent boundary.

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This review describes on the types and characteristics of the main media for peening. peening is a cold working process impacting the work material using spherical particles and producing the surface texture covered with uncountable dents and surface integrity beneath the peened surface. As the working device of peening is small shots, the surface roughness is homogeneous and narrow area can be peened such as the inside of coil springs, pipes and deddendum flank of gears. As the results, peening improves the mechanical properties such as fatigue, stress corrosion cracking, wear, and also improves effects on the flow resistance coefficient of the peened surface and on the heat transfer characteristics. The types of peening media treated in this paper are cast steel, cut wire, conditioned cut wire, glass, ceramics, stainless steel, cemented carbide, high speed steel and amorphous.

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peening is widely applied in the automotive and aerospace industries in order to improve the fatigue strength of the metal components by compressive residual stress. In the case of large components, the peening process is generally performed by moving peening equipment that follows a trajectory on the component surface by means of a robot. In order to construct a robot program for the peening of complex components, this study aimed to obtain a functional approximation of the impact pressure distribution in the stream. The impact pressure distributions were measured with pressure measurement films (Prescale) and a pressure distribution mapping system. The dependence of the mean impact pressure in the stream on the mass was in good agreement with the dependence of the arc height of the Almen strip on the mass. The impact pressure distributions using various masses and standoff distances were measured and approximated by modified Gaussian distribution functions, which included the saturation curve. Three coefficients in the modified Gaussian distribution functions depended on the mass and the standoff distance. The modified Gaussian distribution functions were used to determine the impact pressure distributions of a twice- peened samples. These calculated values were in good agreement with the experimental results. However, for tilted peening, the impact pressure distributions were more complex because the standoff distance at each position on the film was different. The impact pressure distributions of the tilted conditions calculated by the modified Gaussian distribution function, which considered the variation in the standoff distance, were in good agreement with the experimental results for a tilt angle ranging from 30° to 90°.

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peening, which imparts compressive residual stress, is a very effective means for improving the fatigue strength and is widely used for springs. The relationship between fatigue strength and compressive residual stress by peening is well known and is a subject of many previous studies. Residual stress caused by peening is generally evaluated using X-ray stress measurement method, and it give rise to compressive residual stress macroscopically when the X-ray irradiation area is not small.　On the other hand, in order to investigate the microscopic stress distribution of dents around the vicinity, there are research and experiments with big steel ball simulating a , and studies using FEM method confirms that tensile residual stress is generated locally, such as the center of a dent. However, identifying the residual stress generation mechanism by peening using calculation alone is a very difficult task because there are many factors involved. In this study, with the aim of clarifying experimentally the microscopic residual stress distribution of peening surface with CCW(conditioned cut wire), which is widely used for the production of spring, we have developed an X-ray diffractometer which makes it possible to measure the microscopic stress distribution. We prepared as specimen SUP9 (JIS G 4801: spring steels), peened at coverage of 10%, 60% and 300%. The microscopic residual stress distribution is measured in an area of 0.8mm x 0.8mm with 0.1mm step on each specimen surface. Obtained results are summarized as follows: peened surface has average compressive residual stress present in large irradiation areas, but the tensile stress and compressive stress of the yield stress order has been distributed in local areas of 100μm or less. It became clear that, even if the coverage of the peening is increased, there is not much difference of macroscopic residual stress, and an overall uniform compressive stress distribution is not obtained; but there is a large residual tensile stress in the local area. There is no correlation between surface shape and residual stress distribution due to peening. In the stress distribution around the dent by single , unlike previous research results using peening of the sphere, it clearly indicates a residual stress distribution with no regularity.

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For Austempered Ductile Iron (ADI) gears, a -peening may be utilized to improve the bending fatigue strength. However, under some -peening conditions, the increase of surface roughness by -peening may decrease the surface durability of ADI gears. The authors investigated the influence of -peening on the surface durability of ADI rollers using a disk machine which simulates the rolling and sliding action of gears. Two types of -peenings were adopted, that is, the conventional -peening and the fine particle -peening. The results are summarized as follows : (1) The increase of surface roughness by the conventional -peening causes the decrease of surface durability. This is confirmed by testing rollers polished after the conventional -peening. (2) The surface roughness after the fine particle -peening is smaller than that after the conventional one. The surface durability of ADI rollers after the fine particle -peening is superior to that after the conventional one. (3) Consequently, if -peening is applied to improve the bending fatigue strength of ADI gears, the fine particle -peening is useful to prevent the decrease of the surface durability.

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Several experiments were run to determine the relations between peening variables ( size, velocity, impact angle, peening time) and surface residual stress. The surface residual stress was measured by X-ray diffraction method. The results are as follows : (1) The surface residual stress increases with peening time and then approaches a saturated value (-350-400 MPa) before full coverage. (2) Surface residual stress after full coverage depends slightly upon the peening conditions. (3) Surface residual stress shows the size effect to the thickness for the thin sheet of specimen. (4) Residual stress induced in the affected layer exists together with the non-affected zone and falls to zero where the depth of affected layer equals to the thickness of specimen.

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