材料
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
30 巻 , 337 号
選択された号の論文の15件中1~15を表示しています
  • 篠原 孝順, 松本 桂一
    1981 年 30 巻 337 号 p. 951-962
    発行日: 1981/10/15
    公開日: 2009/06/03
    ジャーナル フリー
  • 大久保 勝夫
    1981 年 30 巻 337 号 p. 963-974
    発行日: 1981/10/15
    公開日: 2009/06/03
    ジャーナル フリー
  • 石川 雄一, 尾崎 敏範, 保坂 信義, 西田 脩
    1981 年 30 巻 337 号 p. 975-980
    発行日: 1981/10/15
    公開日: 2009/06/03
    ジャーナル フリー
    The present paper concerns with the method of prediction of the maximum pit depth expected for a component based on the results of laboratory test program. The method is typically illustrated with an example of determination of pitting corrosion life of air cooled heat exchanger tubes.
    Various scale component models are exposed to the condition simulating the service condition of the component. The maximum pit depth is measured for each model as a function of time. The results are analyzed by means of the extreme value statistics and the maximum pit depth expected in the actual component is estimated by the concept of return period and is plotted as a function of time. Curve fitting by the least square method yields the corrosion life curve of the component. Furthermore, safety factor is statistically determined and incorporated into the prediction, which can be useful in determination of the thickness of the tube to be employed. The corrosion life curve of an air cooled aluminum heat exchanger tube predicted by the laboratory test program is compared with its field performance. A safety margin is indicated in the prediction and is attributed to a higher corrosion aggressivity of the environment to which the model is exposed.
  • 小若 正倫, 山中 和夫
    1981 年 30 巻 337 号 p. 981-987
    発行日: 1981/10/15
    公開日: 2009/06/03
    ジャーナル フリー
    The effect of minor elements (C, N, P and S) on stress corrosion cracking (SCC) of high purity carbon steels has been investigated by SCC tests of U-bend, constant load and slow strain rate technique (SSRT) in boiling 60% Ca(NO3)2 solution. The fracture surface was fractographically investigated by scanning electron microscopy. The results obtained are as follows:
    (1) The threshold stress of steels containing carbon more than its solubility limit increased with increasing carbon content.
    (2) The threshold stress of carbon steels decreased when the carbon content was reduced to the solubility limit. However, when the carbon content was reduced below about 0.002%, the threshold stress increased again and SCC was hard to occur.
    (3) Therefore, carbon had a beneficial effect in the precipitated state at the grain boundary as carbides, but had a detrimental effect in the segregated or very fine precipitated state at the grain boundary.
    (4) Nitrogen had a detrimental effect on SCC in the composition range of 0.0025∼0.0375%, but its effect was small as compared with carbon.
    (5) Phosphorus had a detrimental effect on SCC in the composition more than about 0.035% for the steels water-quenched from 1203K. On the other hand, both phosphorus and sulfur had detrimental effects on SCC for the steels furnace-cooled from 1203K. However, no effect of phosphorus and/or sulfur was observed on SCC for the steels air-cooled from 1203K.
    (6) Manganese promoted SCC susceptibility of the extra low carbon steels.
  • 内田 仁, 山本 一巳, 小寺沢 啓司, 山田 巌, 川辺 秀昭
    1981 年 30 巻 337 号 p. 988-994
    発行日: 1981/10/15
    公開日: 2009/06/03
    ジャーナル フリー
    The effects of cold working and heat treatment on the stress corrosion cracking (SCC) susceptibility of SUS 304 stainless steel in boiling 35% MgCl2 solution at 398K were studied by the constant loading method.
    The SCC susceptibility of specimens subjected to cold working depends on the amount of α'-martensite; especially when a large amount of α'-martensite is formed by prestraining at low temperature, the susceptibility shows a marked increase. In this case, the fracture surface morphology is closely related to the presence of strain-induced martensite (ε, α'), which contributes considerably to the susceptible path for cracking. On the other hand, the SCC susceptibility of specimens subjected to a prior cold working and subsequent heat treatment also depends on the degree of α'→γ reverse transformation, and thus on the amount of residual α'-martensite. By sensitizing the specimens containing a large amount of α'-martensite, the susceptibility to intergranular corrosion by Strauss test decreases. Consequently, this susceptibility does not necessarily agree with that to intergranular cracking in the SCC test solution.
    Based on the above results, the role of strain-induced martensite in SCC behaviour of metastable austenitic stainless steel was discussed.
  • 駒井 謙治郎, 中村 誠, 遠藤 吉郎
    1981 年 30 巻 337 号 p. 995-1000
    発行日: 1981/10/15
    公開日: 2009/06/03
    ジャーナル フリー
    The influence of hydrogen-supply and hydrogen-diffusion on the crack growth of a high-strength steel (SNCM 439) was investigated under repetitional stresses and under a sustained-load by changing hydrogen-diffusion conditions (ie, Pre-Charge, Bulk-Diffusion and Tip-Diffusion conditions). Under the Pre-Charge condition, hydrogen was fully charged into metal from all the surfaces of the specimen before and during the test, so that hydrogen could be supplied from the crack tip as well as from the bulk metal. Under the Bulk-Diffusion condition, hydrogen was supplied not from the crack tip but only from the bulk metal. Under the Tip-Diffusion condition, hydrogen was supplied only from the crack tips. The summary of the results obtained is as follows:
    (1) Under the Pre-Charge condition, the crack-growth-rate was highly accelerated.
    (2) In the case of KFSCCKmax<KISCC cyclic SCC crack growth was much more accelerated by the hydrogen supply of Tip-Diffusion than by that of Bulk-Diffusion. In the case of KmaxKISCC the acceleration of crack growth depended on the cooperative effect of Tip- and Bulk-Diffusions.
    (3) The acceleration of crack growth promoted by hydrogen diffusion was observed under repetitional stresses. The greater the cycle frequency was, the more remarkable the acceleration became. The promotion of hydrogen diffusion by cyclic stresses was also supported by the fractographical observation.
  • 岩佐 美喜男, 上野 力, R. C. BRADT
    1981 年 30 巻 337 号 p. 1001-1004
    発行日: 1981/10/15
    公開日: 2009/06/03
    ジャーナル フリー
    The fracture toughness (KIC) was measured for quartz and sapphire single crystals as a function of crystal orientation at room temperature. The controlled surface flaw method popularized by J. J. Petrovic et al. was employed in this experiment. Knoop indentor was used to introduce a semicircular microflaw on the surface of the specimen. Then the 3-point bending rupture strength was measured and KIC was calculated from the flaw size and strength.
    Five kinds of crystal orientations, namely (0001), (0110), (0111), (1120) and (1121) planes as fracture surface, were used for quartz, and four crystal orientations, namely (0001), (1100), (1102) and (1120) planes as fracture surface, were used for sapphire. The relation between KIC and the Young's elastic modulus (E) perpendicular to the fracture surface was investigated.
    It is expected from the theoretical consideration that KIC follows a linear dependence of E. The linear relation between KIC and E was actually observed for both quartz and sapphire single crystals. This kind of relation was also reported for MgAl2O4 single crystal. The KIC vs. E plot shows different lines for different crystals, namely quartz, sapphire and MgAl2O4. As a consequence, it is concluded that the proportional constant of this relation is dependent on the crystal structure.
  • 本間 克彦, 立野 常男, 岡田 広, 河合 伸泰, 西原 正夫
    1981 年 30 巻 337 号 p. 1005-1011
    発行日: 1981/10/15
    公開日: 2009/06/03
    ジャーナル フリー
    Four kinds of sintered Si3N4 were HIP'ed without container. The effects of HIP condition on density, weight change, microstructure and flexural strength were studied. The results showed that nitrogen was more preferable than argon as the pressure medium of HIP, and crystal grains of Si3N4 were considerably grown by HIP treatment at high temperatures around 1900°C. Moreover, the flexural strength and Weibull modulus of sintered Si3N4 which contained 6% Y2O3, 2% Al2O3 and 3% MgO as sintering additives were improved from 537 to 805MPa and from 5.2 to 8.0, by HIP treatment, respectively.
  • 西川 友三, 岡本 泰則, 岡田 伸義
    1981 年 30 巻 337 号 p. 1012-1018
    発行日: 1981/10/15
    公開日: 2009/06/03
    ジャーナル フリー
    Plastic deformation of Mn-Zn ferrite single crystal was investigated by constant stress and constant strain rate tests. The crystal samples were compressed along[001], [110]and[111]axes at temperatures between 1000°and 1400°C. The samples deformed along[001]axis were quenched and their etched surface was observed. Rows of etch pits on (110) plane were thought to represent slip dislocations.
    In the constant strain rate tests, yield drop was observed at relatively low temperatures, accompanied by a drastic increase of etch pit density just after the upper yield point.
    At a constant strain rate (1.9×10-4sec-1), {110} slip was thought to cause yielding for[001]compression at the temperatures tested (1000°to 1450°C). For[110]and[111]compressions, it appeared that different slip systems caused yielding depending on temperature. It was indicated that {111} planes were slip planes at yielding in the higher temperature region. However, yielding in the lower temperature region was caused by slips on {110} planes for[110]compression, and by slips on {100} planes for [111]compression.
    The activation volume for flow under[001]compression ranged from 20b3 at lower stresses to 5b3 at higher stresses. The activation energy at lower temperatures (≤1200°C) was 60 to 80kcal/mol and was extrapolated to 135kcal/mol at τ=0. The rate-controlling mechanism at lower temperatures was thought to be thermally activated overcoming of Peierls-Nabarro stress rather than dislocation climb (diffusion). The low activation energy (10 to 30kcal/mol) was obtained at higher temperatures. It was suggested that interpenetration on intersecting slip planes, diffusion and cross slip occured.
  • 伊藤 正治, 酒井 清介, 伊藤 勝
    1981 年 30 巻 337 号 p. 1019-1024
    発行日: 1981/10/15
    公開日: 2009/06/03
    ジャーナル フリー
    The three point bending tests were carried out on hot-pressed Si3N4 containing Y2O3 and Al2O3 to grasp the characteristics of mechanical strength of ceramics, and the probability density distribution of failure stress for 415 specimens was obtained. Then, the fracture origins were observed by a scanning electron microscope. The relation between the type of fracture origin and the bending strength was investigated. The results are as follows:
    (1) The experimental probability density for the most fitted well the theoretical Weibull distribution, but for several percents of low strength, the experimental failure probability did not fit and was higher than the theoretical one.
    (2) There were four main types of fracture origins, and the same three types of fracture origins appeared in the low strength specimens. Therefore, the difference in the failure probability for the low strength region could not be explained by the difference in the type of fracture origin.
    (3) As the results of investigating all fracture surfaces, the surface fracture was 18% of all bars, and the internal fracture was 79%. The mean strength and the Weibull modulus of each group were almost equal, respectively. Therefore, the true stress at the internal fracture origin equalled the average of about 90% of that at the surface fracture origin.
  • 石川 博幸, 新開 紀彦
    1981 年 30 巻 337 号 p. 1025-1031
    発行日: 1981/10/15
    公開日: 2009/06/03
    ジャーナル フリー
    Crack formation around Vickers indentation has been studied on PbO-ZnO-B2O3 glasses with a wide range of KIc and commercial silicate glasses; fused silica, Pyrex, and float glasses.
    Observations of crack initiation indicated that the Palmqvist type radial cracks generated in the lower loading range, and median cracks were formed in the higher loading range. Fused silica and Pyrex glasses showed cone cracks in addition to the radial and median cracks in all over the loading range.
    The relationship between the initiation load for the median crack and the material parameters (KIc and HV) obtained in this study supported the Lawn-Evans model. The magnitude of the initiation load was, however, considerably higher than that calculated by their theory, suggesting a necessity of some corrections for the parameters related to the deformed zone beneath the indenter. The initiation load increased with an increase in plastic zone size estimated from the Dugdale model, indicating that less plastically deformable glasses require lower load to form the median crack because of greater mismatch at the elastic/plastic boundary beneath the indenter. In spite of little plastic deformation, fused silica showed slightly higher initiation load than the other glasses probably due to densification.
    Resistance to the crack formation in the indentation was discussed in terms of fracture toughness and elastic/plastic properties of glasses.
  • 宮田 昇, 神野 博
    1981 年 30 巻 337 号 p. 1032-1037
    発行日: 1981/10/15
    公開日: 2009/06/03
    ジャーナル フリー
    A theoretical analysis is made to the indentation hardness of two-phase, glass matrix composites containing spherical crystalline or glass particles. It is hypothesized that glass is an elastic-plastic solid on a microscopic scale. In the case of a hard particle dispersion, the composite hardness depends on the matrix hardness, the volume fraction of dispersed phase, the elastic properties of the two phases and also the matrix flow stress. In the case of a soft particle dispersion, however, the hardness and the elastic moduli vary in parallel with the volume fraction of dispersed phase. Experimental results of the Vickers hardness of phase-separated PbO-B2O3 glasses are used for the varification of the theory. Attempts are also made to interpret published hardness data for glass-ceramics in terms of their microstructure and the properties of the constituent phases. The theory explains well the hardness behavior of phase-separated glasses and glass-ceramics having particulate microstructure.
  • 生島 弘志
    1981 年 30 巻 337 号 p. 1038-1043
    発行日: 1981/10/15
    公開日: 2009/06/03
    ジャーナル フリー
    Mechanical properties of piezoelectric ceramic transformers were investigated as an example of the dynamic behavior of piezoelectric ceramics under large amplitude operation. The static and dynamic strengths were measured on the driver and generator sections of the transformer. The difference in heat production between the sections was recognized, which proved to be derived from an orientation discrepancy between the poling and stressing directions.
    A large non-linearity common to the mechanical strength and the heat-generation phenomenon was found to be associated with the non-linearity in resonance characteristics of resonators.
    Mechanical fracture of piezoelectric ceramic transformers, which is the ultimate event under large amplitude stress, occurred mainly in the secondary portion. This phenomenon is understandable from the difference in static tensile strength between the primary and secondary portions.
    The mechanical strength of piezoelectric ceramics also depended on their grain size as in the case of other ceramics. The propagation path of the crack generated was transgranular or intergranular depending upon grain size. Griffith cracks were hardly observed in any specimen tested. The existence of etch pits, which may be due to dislocations, was discovered for the first time in piezoelectric ceramics. Strain-hardening was also recognized.
    From the above experimental results, a new model for the mechanical break-down mechanism in piezoelectric ceramics was proposed.
  • 岩崎 秀夫, 泉 守
    1981 年 30 巻 337 号 p. 1044-1050
    発行日: 1981/10/15
    公開日: 2009/06/03
    ジャーナル フリー
    In the hot-press sintered ceramics, their longitudinal and transverse wave velocities exhibited anisotropies characterized by the “Quasi-uniaxial symmetry” represented by the principal axis parallel to the pressure direction in hot-pressing. Velocities propagating perpendicular to the hot-press direction were somewhat faster than those propagating parallel to the hot-press direction. Velocity differences between the “parallel” and the “perpendicular” directions were estimated to be about 5% in Si3N4. For convenience' sake, elastic constants were evaluated from the velocity values measured in the hot-press direction. The propagation loss factors at room temperature were measured by longitudinal and transverse waves in the frequency range of 30 to 130MHz. Loss factors exhibited the frequency dependent characteristics proportional to the square of frequency.
    Acoustic Emission (AE) associated with slow crack growth was observed at room temperature in the atmosphere by using the double torsion technique in which the cross-head speed of 10μ/min was adopted. A close relationship between the AE patterns and the fracture surface structure was clearly recognized. Averaged crack growth velocities and stress intensity factors were calculated to be 10-4m/s and 5.1×105kgm-3/2, respectively. In addition, it was confirmed that the AE count rate, dN/dt, was linearly proportional to the crack growing velocities in the range of the order of 10-4m/s.
    The Si3N4 cylinder (168mm diameter with 15mm thickness and 93mm axial length) with the thin hole-type-model defects processed by the laser drilling was prepared to confirm the performance of the conventional ultrasonic NDT apparatus. The sizes of the model defects were chosen as 150, 320, and 500μ. Detectability of the defects with the size of about 50μ was confirmed by echo detection due to refracted transverse waves of 5MHz in the water immersion method.
  • 永守 正道, 三木 光範
    1981 年 30 巻 337 号 p. 1051-1057
    発行日: 1981/10/15
    公開日: 2009/06/03
    ジャーナル フリー
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