材料
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
53 巻 , 3 号
選択された号の論文の18件中1~18を表示しています
  • 足立 忠晴, 武本 剛, 荒木 稚子, 山路 昭彦
    2004 年 53 巻 3 号 p. 241-246
    発行日: 2004/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    We experimentally studied effect of ribs on impact energy absorption of thin-walled cylinders. Several kinds of the specimens with different intervals and numbers of ribs were made of aluminum alloy. The drop weight test was conducted to examine relations between impact force and displacement of the specimens. It was found that the crushing modes were dependent on distance between ribs. Axisymmetric and non-axisymmetric crushing modes occurred for short distance and for long distance, respectively. The mean crushing force for the axisymmetric mode was larger than one for non-axisymmetric mode. It was clarified that the crushing behavior in an interval of rib was independent of one in other interval. Therefore, a cylinder with a lot of short interval ribs has high ability for impact energy absorption.
  • 小林 秀敏, 臺丸谷 政志, 櫻田 浩司
    2004 年 53 巻 3 号 p. 247-253
    発行日: 2004/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    In this study, the compressive deformation behavior of water-resistant corrugated fiberboard was investigated by quasi-static and impact compressive tests using a stress bar apparatus. The effect of water absorbed in the corrugated fiberboards on the compressive strength and absorbed energy up to the beginning of the densification in the tests was also examined using dry and soaked specimens. It was found that the absorbed water ratio of corrugated fiberboard increases following a power law of soaking time. The strength and the absorbed energy for the corrugated fiberboards decrease linearly with the increase of the absorbed water ratio. These decreasing rates to each dry specimen show similar tendency regardless of waterproof property added to the individual corrugated fiberboards. The decrease of the strength and the absorbed energy due to the increase of absorbed water becomes small when corrugated fiberboards are compressed dynamically. The strength and the absorbed energy obtained from impact tests are much greater than those obtained from static tests.
  • 山内 良昭, 中野 元博, 尾崎 典雅, 田中 和夫
    2004 年 53 巻 3 号 p. 254-259
    発行日: 2004/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    We performed hyper-velocity impact tests that laser-accelerated aluminum flyer collided to carbon fiber reinforced plastics (CFRP) target. A short-pulsed intense laser beam can accelerate a small flyer as fast as LEO (low earth orbit) satellite velocity. We succeeded in observing the deformation and fracture behavior of the CFRP target with a high-speed framing camera. After the impact experiments, we investigated damages of the CFRP target with an optical microscope and a scanning electron microscope (SEM). As these results, the hyper-velocity impact fracture mechanism of CFRP was proposed as follows: (1) Under the impact back surface, spallations are caused by reflected tensile waves and the similar surfaces of the crack-opening mode I fracture are created. (2) The spalling cracks propagate along the direction of carbon fibers and produce the fracture surfaces of mode II or mixed-mode I/II. (3) At the center of the spalling layer, carbon fibers are kinked and broken by tension. For the lower laser energy, the above damages could not extend to carbon fiber breakage. On the basis of the fracture mechanism, we assembled a model for numerical analyses. Using the LS-DYNA3D, we conducted numerical simulation of the hyper-velocity impact tests. Displacement and velocity at back surface of the CFRP target calculated in the numerical analyses agreed comparably well with the results of the experiments.
  • 板橋 正章, 福田 博
    2004 年 53 巻 3 号 p. 260-265
    発行日: 2004/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    One of the causes of unexpected structural failure is material damage induced by fatigue and impact. So far, the effects of fatigue and impact on material behavior have been investigated independently. In fact, however, sequential impact loading after fatigue loading is seen frequently in practical use of structural materials. In this paper, such a phenomenon is simulated by dynamic tensile test after low-cycle pre-fatigue for a Rolled Steel for Building Structure (JIS G 3136-1994), SN490B and a Rolled Steel for Welded Structure (JIS G 3106-1999), SM490A. The pre-fatigue is given as sinusoidal pulsating tension (stress ratio: 0, frequency: 20Hz). Maximum stresses are 425MPa and 460MPa. Basing upon the property of SN490B steel, fatigue cycle ratios are 25% and 50%. After the pre-fatigue, dynamic tensile test is conducted at room temperature (19°C) and 0°C. Even in the case of triple severe conditions, that is, low-cycle pre-fatigue, high velocity tension and low temperature, both steels are not so degraded. Only yield ratios are increased up to 90%.
  • 臺丸谷 政志, 小林 秀敏, 石畑 祐輔
    2004 年 53 巻 3 号 p. 266-271
    発行日: 2004/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    Impact tensile strength of concrete at high strain rates is discussed by means of the experimental method of reflected tensile stress waves. The experiment is conducted by the Hopkinson bar technique using an air-gun arrangement and the measuring method is based on the superposition and concentration of tensile stress waves reflected both from the free ends of a striking bar and a specimen bar. The impact tensile test for mortar test specimen bars at wide strain rates was performed as well as static strength tests, and the experimental data for those strengths were analyzed statistically by a Weibull distribution. Strain rates were determined from the responses of both strain gages and crack gages pasted on the specimen bar. As a result, it was found that the effect of strain rates on impact tensile strength came out remarkably at strain rate 100sec-1 and the impact tensile strength was approximately proportional to strain rates throughout the range from 100sec-1 to 25sec-1.
  • 横山 隆
    2004 年 53 巻 3 号 p. 272-277
    発行日: 2004/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    Through-thickness compressive characteristics of laminated composites at high rates of strain are evaluated using the standard split Hopkinson pressure bar. Three types of laminated composites, namely symmetric cross-ply carbon/epoxy, plain-woven carbon/epoxy and plain-woven E-glass/epoxy with almost the same thickness are tested at room temperature. Cylindrical compression specimens are machined such that the longitudinal direction of each specimen is parallel to the thickness direction of the laminates. The effects of strain rate, type of reinforcing fiber and prepreg form on the secant modulus, ultimate compressive strength, ultimate compressive strain and absorbed energy are examined in detail. It is shown that the cross-ply carbon/epoxy laminated composite exhibits the highest strength characteristics at low and high rates of strain, and there is no correlation between the absorbed energies and the Charpy impact energies for the laminated composites tested.
  • 松島 康, 可児 弘毅
    2004 年 53 巻 3 号 p. 278-282
    発行日: 2004/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    Shock induced polymorphic transition of pure iron (99.5%) has been investigated experimentally using in-material self-made manganin gauges which has a shape of one-turn coil. A negative pulse is superposed on an output signal from the gauge in the pressure range above about 18GPa. The negative pulse is thought to be originated in shockinduced polymorphic transition (α-ε phase transition) because the polymorphic transition is followed by magnetic transition (ferromagnetic to paramagnetic). The iron plate specimens between which a manganin gauge is sandwiched are magnetized in the vicinity of the gauge by constant current applied to the gauge. The polymorphic transition behind shock front reduces magnetic flux near the gauge when the shock front passes through the gauge. This flux reduction generates the negative pulse. From the negative pulse superposed on a gauge signal, information on the polymorphic transition can be obtained. Experimental data show that the negative pulse appeared in the pressure range above 18GPa and the amplitude of the pulse increased with the applied pressure. It is inferred from the discussion about experimental data that the maximum rate of transition increases with applied pressure.
  • 二川 正敏, 直江 崇, 粉川 広行, 石倉 修一, 伊達 秀文
    2004 年 53 巻 3 号 p. 283-288
    発行日: 2004/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    A liquid-mercury target system for the MW-scale target is being developed in the world. The moment the proton beams bombard the target, stress waves will be imposed on the beam window and pressure waves will be generated in the mercury by the thermally shocked heat deposition. Provided that the negative pressure generates through its propagation in the mercury target and causes cavitation in the mercury, there is the possibility for the cavitation bubbles collapse to form pits on the interface between the mercury and the target vessel wall. In order to estimate the cavitation erosion damage, Split Hopkinson Pressure Bar (SHPB) impact tests were performed to impose the impact pressure to the interface between mercury and solid metals. In particular, the surface hardening treated samples: Kolsterising, some coatings are investigated. As results, it is confirmed that the pitting damage is suppressed by surface hardening treatments and relative hardness appeared to be a good correlating parameter on impact erosion resistances that are evaluated by both the SHBP and classical vibratory hone tests.
  • 田中 大之, 岡田 弘史, 成田 敏夫
    2004 年 53 巻 3 号 p. 289-292
    発行日: 2004/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    The laser beam microscopy was applied to the in-situ observation of thermal deformation of the tin-Kovar joint in heating and cooling processes over the temperature range between 298 and 423K. The surface displacement of the tin-Kovar joint was measured with accuracy at 0.1μm, and the crack initiation and propagation of the tin-Kovar joint was observed in-situ during the heating and cooling the joint. Using the axial symmetric 2-dimensional thermo-elasto-plastic analysis, the stress-strain distributions were calculated in the heating and cooling processes over the temperature range between 298 and 423K. The observed displacement and calculated one agreed in the heating process, whereas the calculated displacement differed from the observed one in the cooling process. The calculated displacement accumulated in the thermal cycle, not returning to the initial position, and the correlation between the observed displacement and calculated one in heating and cooling processes was discussed.
  • 永井 光輝, 臺丸谷 政志, 小林 秀敏
    2004 年 53 巻 3 号 p. 293-299
    発行日: 2004/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    The dynamic behavior of a circular tube subjected to high-rate moving internal pressure was examined experimentally and analyzed numerically with FEM code, LS-DYNA. The time histories of transient stress waves in both the circumferential and axial directions were observed from strain gauges pasted on the outer surface of several positions along the circular tube with a constant cross-section. Also, the time histories of high-rate moving internal pressures were measured by piezoelectric elements embedded in the inner surface layer of the circular tube. The moving internal pressure for the load conditions of the numerical analysis was based on the experimental observation and the analysis was carried out under the condition of two-dimensional model in the cylindrical coordinates. The numerical results showed comparatively good agreement with the experimental ones and the analytical model proposed in this study is effective. Additionally, the dynamic behavior of inner and outer surface of the circular tube was predicted.
  • 柏谷 賢治, 佐藤 幸雄
    2004 年 53 巻 3 号 p. 300-305
    発行日: 2004/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    Shearing deformation due to high cyclic rolling contact fatigue formes a unique texture below the contact surface. It is measured by means of X-ray diffraction and expresses as a pole figure. The pole figure shows a pattern which looks like that of a single crystal. That results from the deformation under the rule of the crystallographic easy slip plane/direction. Rolling contact fatigue tests with a pair of cylindrical test pieces made of cobalt, pearlitic steel and iron are performed in order to clarify the shearing plane/direction experimentally for development of the contact mechanics. The test pieces made of cobalt whose crystal structure is h. c. p. and whose crystallograpfic easy slip plane is only the bottom plane (0001) are used for determination of the shearing plane. The pole figure of the pearlitic steel reveals that the ferrite layer sandwiched between cementite plates in pearlite deforms as a result of a crystal easy slip αFe {211} ‹111› and that the shearing direction is the rolling direction on the shearing plane mentioned above. Furthermore, the shearing deformation of iron as a result of crystal easy slips (110) [111] and (110) [111] is clarified by the X-ray texture analysis.
  • 山際 謙太, 泉 聡志, 酒井 信介
    2004 年 53 巻 3 号 p. 306-312
    発行日: 2004/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    A numerical analysis of a fracture surface is needed in the fractography. The method proposed in this paper identifies quantitatively the striation region observed in the fatigue fracture surface, and the striated surface ratio is calculated. The method proposed characterizes the striation region by using the wavelet transform, and the degree of striation is calculated from the wavelet coefficient. The Gabor function is applied as the mother wavelet function and it can be used to extract the striped pattern which is the feature of a striation. In order to evaluate the validity of the method, it is applied to the virtual fracture surface and the SEM picture of the fatigue fracture surface of 2.25Cr-1Mo steel. Matching of the striation region calculated from the degree of striation and the result obtained from the human observation is performed. Consequently, good agreement between the judgment result by human observation and the judgment result by the method is obtained, and it is shown that the proposed degree of striation is appropriate to the evaluation of a striation region. Therefore, it becomes possible to evaluate a striation region using the method proposed, and it supports for the decision-making of an analyst who is unfamiliar with the fractography.
  • 李 成為, 加藤 昌彦, 中佐 啓治郎
    2004 年 53 巻 3 号 p. 313-320
    発行日: 2004/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    Decarburized layer was artificially formed on substrate specimens of tool steel (JIS: SKD5) by controlling the austenitizing time before quenching. The specimens were coated with WC-Co cermet by high-pressure high-velocity oxygen fuel (HP-HVOF) spraying. Tensile and edge-indent tests were carried out to evaluate the effect of decarburized layer on delamination strength of coating. During the tensile test, the coating is cracked parallelly many times with increasing load and finally delaminated along the interface between coating and decarburized layer. The tensile strength σc of coating has no remarkable change with decarburized layer thickness, while the interfacial fracture toughness Gc1/2 is lager for decarburized specimen than non-decarburized one and the Gc1/2 increases to an almost constant value with increasing layer thickness beyond 0.2mm. A Two-dimensional finite element method analysis reveals that the tensile stress and shear stress at the crack tip which are perpendicular and parallel to the interface and the tensile stress at the center of the coating are decreased by the existence of decarburized layer. The delamination energy Ed of decarburized specimens obtained by edge indent test is lower than that of non-decarburized specimen. The reason is that the decarburized layer is easy to be sheared during penetration of indenter.
  • 田邉 裕貴, 三好 良夫, 高松 徹, 粟野 仁
    2004 年 53 巻 3 号 p. 321-326
    発行日: 2004/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    A study on the effects of Ti interlayer on the characteristics of TiN films deposited by DC magnetron sputtering was carried out. Two type films, TiN/Ti bilayer film with Ti interlayer between S45C substrate and TiN film, and TiN monolayer film in which TiN film was deposited directly on the substrate, were prepared, and the micro-structure and the properties of these TiN films were compared. It was observed that the surface of TiN film became so smooth by depositing Ti interlayer. The adhesive strength of TiN/Ti bilayer film was larger than that of TiN monolayer film. It was confirmed Ti interlayer had the effect to improve the adhesive strength of TiN film. The residual stress of TiN/Ti bilayer film, which was thought to be introduced by bombardments of high-energy ions toward TiN film in coating process, was almost same as that of TiN monolayer film. Corresponding to it, hardness and toughness of TiN/Ti bilayer film were almost same as those of TiN monolayer film. Compared at relatively high bias voltage, the specific wear rate of TiN/Ti bilayer film was lower than that of TiN monolayer film. It was concluded that adhesive strength and specific wear rate were improved by using Ti interlayer without decreasing the other properties such as hardness and toughness.
  • 北川 正義, 石田 真一, 柴垣 憲吾, 山田 良穂
    2004 年 53 巻 3 号 p. 327-332
    発行日: 2004/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    It has been shown that the yield process is very different between the annealed and quenched samples of amorphous polymers. Many slip lines appearing just before yielding cause a specimen necking near the peak stress in asreceived and annealed samples, while it occurs without visible formation of slip lines in quenched samples. To investigate this difference may promote the understanding on the yield mechanism of amorphous polymers. In this paper, the results mentioned previously were confirmed at tensile and shear tests and some mechanical properties related to the yielding were measured using as-received (AR) and quenched (Q) samples of amorphous polymers, PC, PVC, PMMA and PET. It was shown that (1) the values of tanδ are higher in Q than in AR samples, (2) the diffusion rate of methyl alcohol to PMMA is greater in Q than in AR samples, (3) the specific gravities of Q samples are smaller than those of AR ones and (4) the yield mechanism is very different between AR and Q samples under both tension and shearing.
  • 齊藤 和宏, 藤山 一成, 秋国 康成, 藤原 敏洋, 児玉 寛嗣, 吉瀬 仁志, 岡崎 光芳, 川端 太郎
    2004 年 53 巻 3 号 p. 333-338
    発行日: 2004/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    Two approaches were investigated for evaluating unreliability functions of failure events in steam turbine components. One is the parameter normalizing approach to establish the unique relationship between normalized hours or normalized cycles and unreliability for various classes of steam turbine output capacity. Another is the parameter adjustment approach to seek modifying coefficients as the functions of steam turbine design parameters for evaluating the specific unreliability functions from the common master curve. The cumulative hazard function method is applied to evaluate the actual field data fittings of those approaches for turbine rotor bowing and nozzle erosion events respectively. The data fittings through those approaches are good enough to apply the probabilistic risk analysis in the case of small sample size or number of units in the objective type of steam turbines.
  • 古田 均, 堂垣 正博, 小山 和裕, 片岡 宏文, 杉本 博之
    2004 年 53 巻 3 号 p. 339-344
    発行日: 2004/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    Many existing bridges in Japan are suffering from damage due to the deterioration of materials, heavy traffics and aging. In the future, it is evident that serious social problems will arise as the number of damaged bridges increases. Considering the present social and economic situation of Japan, it is urgent and important to establish an optimal maintenance strategy for such existing bridges so as to ensure their safety in satisfactory levels. Life-Cycle Cost (LCC) has been paid attention as a possible and promising method to archive a rational maintenance program. Generally, LCC consists of initial cost, maintenance cost, and renewal cost. However, when considering Life-Cycle Cost in the region that frequent earthquakes occur, it is important to take into account the social and economical effects due to the collapse of structures as well as the minimization of maintenance cost. The loss by the collapse of structures due to the earthquakes can be defined in terms of an expected cost and introduced into the calculation of LCC. In this study, a stochastic model of structural response is proposed, which accounts for the variation due to the uncertain characteristics of earthquakes, and the probability of failure is calculated based on the reliability theory. Then, the expected cost can be obtained by multiplying the failure probability with the loss.
  • 林 知行
    2004 年 53 巻 3 号 p. 345-350
    発行日: 2004/03/15
    公開日: 2009/06/03
    ジャーナル フリー
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