材料
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
54 巻 , 3 号
選択された号の論文の20件中1~20を表示しています
論文
  • 武石 洋征, 中山 昇, 三木 寛之
    2005 年 54 巻 3 号 p. 233-238
    発行日: 2005年
    公開日: 2006/04/07
    ジャーナル フリー
    A new concept of solidification method by compression shearing is developed. By this method the grain size of the fabricated material is fined to nanometer scale, and the strength of the specimen is improved. Appling compression shearing process to powder Aluminum under room temperature and in the atmosphere, we can obtain a thin plate specimen consist of ultra fine crystal grains with preferred orientation. By following conventional ways, it was not possible to obtain such specimen under room temperature.
    In this paper, we described the structural and mechanical properties of fabricated specimen with 100-200nm crystal grain size, which is obtained by Compression Shearing Method.
  • 中出 且之, 黒田 敏雄
    2005 年 54 巻 3 号 p. 239-244
    発行日: 2005年
    公開日: 2006/04/07
    ジャーナル フリー
    The effect of sigma phase on hydrogen embrittlement in 329J3L duplex stainless weld metal was studied. In addition, in order to clarify the mechanism, hydrogen behavior was also investigated by means of internal friction and fractography technique. The internal friction measurements were conducted over the temperature range from 77K to 373K by using an inverted torsion pendulum for a frequency of about 1.5Hz. After hydrogen charging, almost hydrogen can be diffused easily into the austenite through the ferrite and ferrite/austenite interfaces. Consequently, a sharp significant peak due to hydrogen in austenite was detected at 245K in the as-welded specimen. In the case of as-welded specimen a little reduction of strength was recognized, while the significant loss of strength was observed in the weld metal containing significant sigma phase after hydrogen charging.
    The sigma phase clearly accelerated hydrogen embrittlement. In the hydrogen-charged specimen containing significant sigma phase, the internal friction analysis revealed that hydrogen entered in the sigma phase lattice and hydrogen was also trapped sigma/austenite phase boundaries. Furthermore, on the fracture surface, the many secondary cracks associated with interaction between sigma phase and hydrogen were observed. Therefore, it could be concluded that sigma phase itself and sigma/widmanstätten austenite phase boundaries were preferential hydrogen cracking sites. It was found that the reduction of notch tensile strength was mainly attributed to many secondary cracks associated with hydrogen and sigma phase.
  • 鎌倉 光利, 戸梶 惠郎, 柴田 英明, 別宮 宣克
    2005 年 54 巻 3 号 p. 245-250
    発行日: 2005年
    公開日: 2006/04/07
    ジャーナル フリー
    This paper describes the grain refinement due to controlled extrusion and the fatigue behaviour of the extruded materials in two magnesium alloys, AZ61A and AZ31B. Billets of both alloys were extruded at an extrusion ratio of 67 under controlled conditions with three different outlet temperatures, i.e. working temperatures. It was found that grain refinement was attained in both alloys whose grain size decreased with decreasing working temperature, in particular remarkably in AZ31B for which the grain size of approximately 2μm was obtained. Thus it was concluded that extrusion was a very useful method for refining grain size in magnesium alloys. Rotating bending fatigue tests were then performed using smooth specimens of the extruded materials. In AZ61A, the fatigue strength of the extruded materials did not depend on grain size, while in AZ31B, increased with decreasing grain size. Fatigue crack initiation and subsequent small crack growth were examined in AZ31B. Consequently, grain refinement improved significantly both crack initiation resistance and small crack growth resistance, resulting in increase in fatigue strength. Furthermore, it was indicated that fatigue strength was expressed properly by the Hall-Petch relationship in AZ31B, but not in AZ61A.
  • 陳 錦祥, 小河 昭紀, 橋本 良作, 吉田 豊明, 西澤 敏雄, 福山 佳孝, 横川 忠晴, 原田 広史
    2005 年 54 巻 3 号 p. 251-256
    発行日: 2005年
    公開日: 2006/04/07
    ジャーナル フリー
    In order to make the best use of Ni-base single-crystal (SC) superalloys for the gas turbine blades and vanes, the finite element method was used to analyze the difference in the structural strength between SC superalloys and hypothetical isotropy (HI) for the blades and vanes of an actual turbine. As the results, it is found that the structural strength characteristic of the blades and vanes are almost the same for SC superalloys TMS-75 and for CMSX-4. The structural strength characteristic of SC superalloys is quite different from that of the HI material. For the vanes, creep rupture time of SC superalloys is extended substantially compared to that of HI material because of the anisotropy elastic coefficient of SC superalloy. For the blades, structure strength of the frangible part (leading edge and tips) has similar structural strength characteristic with that of the vanes. The structural stress of the blade root depends on the relationship between the thermal and centrifugal stresses. It is possible that when the revolution speed is higher, the stress at the blade root made of the SC superalloys is higher and the creep rupture time becomes short. Because of this phenomenon, special consideration is needed in the blades design.
  • 岡田 満利, 餌取 良幸, 久松 暢, 高橋 毅
    2005 年 54 巻 3 号 p. 257-264
    発行日: 2005年
    公開日: 2006/04/07
    ジャーナル フリー
    In aluminized CoCrAlY coatings used for oxidation tests and for in-service gas turbine blades, a boundary diffusion layer is found at the boundary between the coating and the substrate. The square of the layer thickness is roughly proportional to time. By means of this relationship, there is a possibility that the temperature at any observed area of a blade can be estimated by measuring the layer thickness. However, application of this temperature estimation is limited due to change of diffusion behavior. Regardless of operating time and of observed locations in gas turbine blades, Al-content in the coating decreases almost proportionally to the thickness of the boundary diffusion layer. From this relationship, by finding the time when the boundary diffusion layer reaches the thickness corresponding to an Al-content equal to that in substrate, there is a possibility to predict the time when the Al-content in the coating decreases below that in the substrate. An estimation of Al-content was tried by examining two blades with different operating hours. As a result, the estimated Al-contents are almost equal to the measured ones. As for aluminized CoNiCrAlY coating, the behavior of the Al-content in the coating and of the boundary diffusion layer was examined in oxidation tests, and the possibility of estimating temperature and predicting Al-content is also shown.
  • 岡崎 正和, 平野 一美, 山崎 泰広
    2005 年 54 巻 3 号 p. 265-270
    発行日: 2005年
    公開日: 2006/04/07
    ジャーナル フリー
    Behavior of thermo-mechanical fatigue (TMF) failure of a new generation titanium alloy matrix composite, SP700/SCS-6, was studied, based on a series of investigations on ; (i) mechanical properties under monotonic loading of the SP-700/SCS-6 composite and the matrix alloy; (ii) fiber push-out tests to represent the fiber/matrix interfacial strength at elevated temperatures ; (iii) isothermal low cycle fatigue (ILCF) tests, (iv) interfacial reaction zone to characterize the microscopic damage evolution under the TMF test and the thermal cycle test without external load. A special focus was paid to understand both the mechanisms of TMF failure, and the dissimilarities and the similarities between the TMF and ILCF failures. From the results of these tests, it was shown that the differences of damage characteristics may be concerned with the degradation of the fiber/matrix interface by the crack propagation and reaction layer due to thermal cycles. These systematic investigations showed that the lives and the failure mechanisms of the TMF should be clearly distinguished from those of the isothermal ILCF, whereas there were a few similarities between them. It was also suggested the difference should be primarily originated from the cracking by the repeat of the thermal cycle and the resultant change in fiber/matrix adhesion strength.
  • 岡崎 正和, 井加田 朗, 山崎 泰広
    2005 年 54 巻 3 号 p. 271-278
    発行日: 2005年
    公開日: 2006/04/07
    ジャーナル フリー
    Damage evolution process of a new generation titanium alloy matrix composite, SP-700/SCS-6, was studied when the composite was subjected to thermal cycles at elevated temperatures. Two types of damages were focused on : one is the macroscopic damage, or thermal cycle cracking induced by the repeat of thermal stress ; and the other is the microscopic damage, or microstructural change of the fiber/matrix interface characterization. The investigation on the former showed that the cracks were originated and propagated, associated with the following behavior : the crack propagation rates almost linearly increased with the crack length at the early growth stage, and then they gradually decreased and finally arrested in the most cases. This behavior was shown to be rationalized on the basis of fracture mechanics law. The analysis of the interface by means of a transmission electron microscope and an energy dispersive X-ray spectrometer (EDS) demonstrated that the products of the interface reaction zone, as well as the thickness, were changed by the repeat of thermal cycles. However, the thickness was still significantly thinner, compared with that in other kinds of titanium alloy matrix composite systems.
  • 鹿間 共一, 須崎 嘉文, 江島 正毅, 井手 泰明, 吾妻 俊良, 田中 治, 梶谷 孝啓, 鯉沼 秀臣
    2005 年 54 巻 3 号 p. 279-283
    発行日: 2005年
    公開日: 2006/04/07
    ジャーナル フリー
    Under atmospheric pressure, homogenous non-equilibrium cold plasma was generated by rf (27.12MHz) excitation of He (1700ml/min) and O2 (0-15ml/min) gases. Bis-dipivaloylmethanato zinc (Zn(O2C11H19)2) was vaporized and carried with the He gas flow into the plasma zone to be deposited as a thin film on a glass substrate at room temperature. To assist the decomposition and oxidation of Zn (O2C11H19)2 for creation of the ZnO film, a heat treatment tube was placed between the vaporizer and the plasma torch and oxygen gas was added to the system either before or after the heat treatment. XRD, AFM, and AES analyses verified fabrication of a polycrystalline ZnO film.
  • 中井 善一, 橋本 晃久, 竹谷 彰彦
    2005 年 54 巻 3 号 p. 284-289
    発行日: 2005年
    公開日: 2006/04/07
    ジャーナル フリー
    Fatigue test system with electrolytic-polishing apparatus was developed to study the effect of specimen diameter on the fatigue strength of metallic micro-materials. In the system, a specimen with small cross-section was formed after the wire with 1.0mm in diameter was gripped to the fatigue test machine, where the formation was conducted by the electro-polishing. Commercially pure aluminum or commercially pure iron wires were employed for the present experiment. In either metal, variations of fatigue lives were very large compared with those of bulk specimens. In the pure aluminum, fatigue lives were shorter and the scatters of fatigue lives were larger for smaller specimens at the same stress amplitude, while there were small effects on the specimen size in pure iron. Two types of fracture morphologies were observed. Those were with or without fatigue fracture surface. The latter were necked at the final stage of the life.
  • 成瀬 友博, 服部 敏雄, 山口 幸宏, 金井 哲也, 関谷 太志
    2005 年 54 巻 3 号 p. 290-295
    発行日: 2005年
    公開日: 2006/04/07
    ジャーナル フリー
    Chlorosulfonated polyethylene rubber (CSM) is used in tubes and wire covers among many other uses. Generally, rubber shows considerable changes in mechanical properties over time and in temperature. To confirm the reliability of these products, we must evaluate how they degrade in humidity, sunlight, and under thermal loading. We therefore studied the thermally degrading properties of CSM. We first measured thermal reduction of the elongation and of the fatigue strength of CSM. To evaluate these degrading properties, we used the Arrhenius's equation to confirm the relationship between the temperature and the time. Using these evaluation methods we can predict thermal reduction of fatigue strength taking temperature and exposure time into account. The time-temperature shift factor of thermal degradation of the elongation agrees well with that of the fatigue strength. Viscoelastic behavior of virgin CSM and that of thermally degraded one were evaluated. Arrhenius's equation was found to describe the temperature dependence of thermal degradation of complex modulus. The time-temperature shift factor of thermal degradation of a complex modulus does not agree with that of elongation and fatigue strength.
  • 吉成 仁志, 榎並 啓太郎, 菅 満春, 金田 重裕
    2005 年 54 巻 3 号 p. 296-301
    発行日: 2005年
    公開日: 2006/04/07
    ジャーナル フリー
    It is known that the ductility of steel lowers, when the prestrain is given to steel product. In the other, it has been clarified that the generation of the ductile crack of virgin steel can be evaluated by ductility limit curve presented by the relationship between stress triaxiality and equivalent plastic strain. In this paper, by using As-Rolled steel and TMCP steel for the sample material, the effect of the prestrain on the ductile fracture behavior was investigated. In the As-Rolled steel, the lowering of the ductility limit curve by the prestrain was confirmed. And, local cleavage crack was observed only in the fracture surface of test piece in which ductility limit curve lowers. From these results, it was clarified that the main factor of the ductility limit curve lowering was the generation of local cleavage crack. Then, we developed the technique which could uniformly evaluate the generation of the ductile crack by ductility limit curve of the virgin material by considering local cleavage crack.
  • 辻上 哲也, 堀川 武, 束田 英信
    2005 年 54 巻 3 号 p. 302-307
    発行日: 2005年
    公開日: 2006/04/07
    ジャーナル フリー
    In order to investigate the relation between a stress cycle and a temperature change of metallic materials, a computer-aided platinum wire temperature measurement system was used for taking the data of temperature, stress and strain into the computer memory simultaneously. Fatigue tests have been conducted using the smooth round bar specimen made of carbon steels (S55C, SCM435) and stainless steels (SUS304). The temperature changes under an elastic stress range are agreed well with the value calculated by the thermo-elastic theory. On the other hand, the temperature changes under a plastic stress range are larger than the calculated values, because of the plastic stress-strain works. As the result, the crack initiation life is explained by the equations ; S55C material : Δq · Nc = 1.5 × 109J/m3, SCM435 : Δq · Nc = 2.6 × 108J/m3, SCM435 Material : Δq · Nc = 9.0 × 108J/m3.
  • 酒井 信介, 岡島 智史, 泉 聡志, 岩崎 篤
    2005 年 54 巻 3 号 p. 308-313
    発行日: 2005年
    公開日: 2006/04/07
    ジャーナル フリー
    Recently, importance of risk assessment has greatly increased. However, data of failure probability do not exist sufficiently in our country. Therefore, the method to obtain the probability of failure from inspection data is required. This paper investigates the method to estimate the mother distribution of failure life of structures by inspection data using Bayesian inference. Though Bayesian inference is widely said to be effective for the estimation from small samples, the effectiveness greatly depends on the initial setting of a prior distribution. In this paper, the applicability of Bayesian inference is examined first. For this purpose, Bayesian inference is applied for estimating fatigue life by the inspection data of boiler parts. Next, influence of the initial prior distribution on the results is studied systematically by giving variation to mother parameters. Weibull distribution is assumed for the fatigue life distribution and the investigation is made on scale parameter and shape one. In order to assist the inspection planning, the estimations of MTBF and hazard rate are also investigated. As the result, the relation between the initial prior distribution and the effective range by Bayesian inference is clarified.
  • 松保 明憲
    2005 年 54 巻 3 号 p. 314-319
    発行日: 2005年
    公開日: 2006/04/07
    ジャーナル フリー
    This paper considers efficiency of a hit-or-miss Monte Carlo (MC) method in which each relevant event is simulated on computer. For instance, a failure probability of a system is evaluated as a relative frequency of the failure state occurrence. The method is not efficient, but can be easily applied to various problems without restriction. The method is also robust. Therefore, consideration on its computational efficiency is significant. This paper proposes two methods to improve the efficiency of the above method for structural reliability evaluation. One method is called an Uncommon-Events-Sampling (UES) method in this paper. This method calculates a relative frequency of the failure state occurrence by using nothings but samples corresponding to uncommon events that are significant for reliability evaluation. Next, by considering a ratio of this relative frequency and the required failure probability, this method evaluates the failure probability. Another method is called an Assigning-Pseudorandom-Numbers (APN) method. Although a general MC method uses pseudorandom numbers in their generating order, the proposed method assigns the pseudorandom numbers to basic variables according to their relationship with which the failure state easily occurs. In a numerical example, reliability analysis of a steel truss bridge designed based on Japanese current code is carried out by using the proposed methods. Effectiveness of the proposed methods is illustrated through the numerical example.
  • 花岡 大伸, 宮里 心一, 矢野 真義, 守分 敦郎
    2005 年 54 巻 3 号 p. 320-325
    発行日: 2005年
    公開日: 2006/04/07
    ジャーナル フリー
    This study was to establish the rational repair technology in consideration of the corrosion cell formation pattern (local corrosion or uniform corrosion) and the chloride ion penetration depth of reinforced concrete. The two types of specimen were used; one was the local corrosion specimen with crack and the other was the uniform corrosion specimen without enough cover. During the exposure periods to the accelerated chloride environment, the specimen was performed by some repair methods under the different situations of the chloride ion penetration. The repair methods were the injection method, the surface sealing method, and the local repair method. The conclusions were as follows. The injection method for local corrosion and the surface sealing method for uniform corrosion were rational under the shallow chloride ion penetration. While, it was worry to re-corrode using the injection method and the surface sealing method after the chloride ion penetrated into the deep concrete. Therefore, it was confirmed that the early repair was useful for both the local corrosion and uniform corrosion.
  • 種 健, 平島 健一, 浜野 浩幹
    2005 年 54 巻 3 号 p. 326-332
    発行日: 2005年
    公開日: 2006/04/07
    ジャーナル フリー
    This paper presents analytical solutions for anisotropic elastic medium with multi-layered elliptic inclusions. An arbitrary direction of principal axes of elasticity is considered in the anisotropic matrix. In the model, it is assumed that only the normal stress whose direction is parallel to a generator of inclusion affects a matrix. The relationship between inclination angles of principal elastic axes and stress distribution around the boundary are discussed. In addition, the problem under pure three-dimensional loadings can be solved as quasi three-dimensional analysis.
  • 大城戸 忍, 林 眞琴, 秋庭 義明, 田中 啓介, 皆川 宣明, 森井 幸生
    2005 年 54 巻 3 号 p. 333-338
    発行日: 2005年
    公開日: 2006/04/07
    ジャーナル フリー
    Residual stress generated in an aluminum-alloy shrink fitted specimen was measured by neutron diffraction method and compared with calculated values by FEM analysis. The measured values agree with calculated ones when the diffraction has high intensity and sharp profile. However, the diffraction intensities were dependent on the measurement directions since the specimen possessed texture. Diffraction profiles in directions having a weak diffraction intensity caused an inaccurate evaluation of the residual stress. The measured strain can be modified with the ratio of elastic constant when the Poisson's ratio independ on diffraction plane like as Al alloy. The accuracy of residual stress measurement by the proposal method has better result than conventional method, if measured sample has strong texture.
  • 鈴木 裕士, 盛合 敦, 皆川 宣明, 森井 幸生
    2005 年 54 巻 3 号 p. 339-345
    発行日: 2005年
    公開日: 2006/04/07
    ジャーナル フリー
    In a conventional method of a neutron stress measurement, it is required to know the stress-free lattice constant accurately in order to calculate lattice strains. A new stress measurement method, which does not need the lattice constant of the strain-free material, was proposed. In this study, this proposed method was applied to evaluate the residual stress distributions in welded sample. Utilizing Neutron Diffractometer for Residual Stress Analysis (RESA) in JRR-3 (Japan Research Reactor-3) at Japan Atomic Energy Research Institute (JAERI), the distribution of lattice constant of welded sample was measured by using the coupon samples which was cut from the welded sample. The measured lattice constant was increasing near the weld zone since the martensitic transformation occurred in heat affected zone (HAZ). On the other hand, the lattice constant distribution which was measured by using our proposed method showed an increase as close to the weld zone, and the absolute value of the lattice constant was almost the same as the lattice constant of the coupons. Therefore, it is possible to predict the lattice constant by using our proposed method even if the lattice constant distribution is existed in the materials. The residual stress distributions were evaluated by using conventional method and our proposed method. As a result, the residual stress distributions decided by our proposed method almost agreed with those measured by conventional method. This proposed method can be applied to determination of the residual stress states in the samples with the complex residual stress states.
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