日本機械学会論文集A編
Online ISSN : 1884-8338
ISSN-L : 1884-8338
78 巻, 791 号
選択された号の論文の19件中1~19を表示しています
材料力学,機械材料など
研究随想
研究展望
一般論文
  • 樋口 理宏, 足立 忠晴, 福島 庸介, 荒木 稚子
    2012 年 78 巻 791 号 p. 945-954
    発行日: 2012年
    公開日: 2012/07/25
    ジャーナル フリー
    An approximate method for evaluating the absorbed impact energy of a cylindrical tube with varying cross-section was proposed by using dynamic behaviors of uniform cylindrical tubes subjected to axial impacts. The cylindrical tubes with varying cross-section were approximated as a tube connected with many infinitesimal uniform cylindrical tubes to analyze the crushing behaviors. The crushing of the cylindrical tube with varying cross-section was assumed to progress due to minimum load of the infinitesimal uniform tubes. The dynamic behaviors of the uniform tubes were evaluated by finite element analysis or theoretical analysis. Relations between mean force and displacement for cylindrical tubes with varying cross-section could be analyzed by the approximate method. To confirm the validity of the method, the results of a drop weight impact test for cylindrical tubes with varying cross-section were compared to the analyzed results. The approximate absorbed energy-displacement curve showed good agreement with the experimental results. Moreover, it was clarified that the energy absorption characteristic could be controlled by varying the taper angle of the tubes.
  • 田中 泰明, 宮田 佳織, 田坂 誠均, 中澤 嘉明, 富田 俊郎
    2012 年 78 巻 791 号 p. 955-965
    発行日: 2012年
    公開日: 2012/07/25
    ジャーナル フリー
    The effects of cross sectional shape of polygonal shell members and material properties on impact deformation behavior of ultra high strength steel members were studied by dynamical impact tests and numerical analysis. The result of dynamical impact tests have shown that the buckling behavior is influenced by the width of plane regions and material properties. The buckling load increases as the ratio of the width of plane regions to sheet thickness (Wp/t) decrease, which is well correlated with the flow stress of 7% strain of the material. On the other hand, decrease in the Wp/t makes ultra high strength steel members more susceptible to fracture resulting in reduction in the buckling load. FEM calculations show that reduction in the Wp/t leads to increase in principal strain at ridgelines on the top of buckling wrinkle, which is a major site of initiation and propagation of fracture. With the materials having good uniform or local elongation, the fracture on impact can be suppressed.
  • 遊佐 泰紀, 片岡 俊二, 河合 浩志, 吉村 忍
    2012 年 78 巻 791 号 p. 966-975
    発行日: 2012年
    公開日: 2012/07/25
    ジャーナル フリー
    To analyze large-scale fracture mechanics problems effectively, we apply the partitioned iterative coupling algorithm which has been successfully utilized for multi-physics coupling problems. In the algorithm, the analysis domain is first decomposed into two domains. The one domain contains a crack, while the other does not. The two domains are analyzed separately and alternately with assumed boundary conditions on the boundary between the two domains. By updating the assumed boundary conditions repeatedly, the converged solution is finally obtained. In crack propagation analyses, this coupling iteration is performed at each crack propagation step. In a numerical experiment of an edged crack tension plate model of 1.96 million degrees of freedom, stress intensity factors are computed 4.52 times faster than using a conventional finite element method. This is because, in the partitioned iterative coupling algorithm, the stiffness matrix on the domain far from the crack is constant through the whole crack propagation analysis.
  • 鶴来 昌樹, 青池 聡, 大城戸 忍, 福田 ゆか, 折谷 尚彦
    2012 年 78 巻 791 号 p. 976-988
    発行日: 2012年
    公開日: 2012/07/25
    ジャーナル フリー
    In order to prevent initiation of stress corrosion cracking (SCC) at the inner surface of the butt-weld region of a small-diameter pipe, a residual stress improvement process called delta-T process has been developed. During delta-T process, the outer surface of pipe is heated by an external device and the inner surface is rapidly cooled by flashing water. The large thermal stress due to temperature difference between outer and inner surface could improve tensile stress to compressive one at inner surface. In this paper, the thermal elasto-plastic finite element analysis (FEA) was conducted to clarify the mechanism of delta-T process for piping system with 50A schedule 80 in nominal pipe size. The FEA results showed good agreements with experimentally measurements of temperature and residual stress in delta-T process. In addition, the management criterion to verify the application of delta-T process to piping system by measurement of temperature at outer surface of pipe was discussed by various parametric numerical analyses.
  • 中根 直樹, 眞喜志 隆, Anggit MURDANI, 宮﨑 達二郎, 真壁 朝敏
    2012 年 78 巻 791 号 p. 989-999
    発行日: 2012年
    公開日: 2012/07/25
    ジャーナル フリー
    Fatigue limit is related to the crack initiation and growth process. The length of a surface crack at fatigue limit is related to the size of a single crystal in the case of a plain specimen of low carbon steel, copper, etc. However, the initial crack length is independent of the crystal size in the case of pure aluminum, a lamellar pearlitic steel, etc. So, the relationship between the initial crack length and fatigue limit was investigated in this study by using tool steel SK5. The original microstructure of this material includes spherical microstructure. However, after annealing under some temperatures, that microstructure changed to a lamellar microstructure. It was found that the fatigue limit of a plain specimen of this material could not be evaluated by average hardness. However, its fatigue limit could be evaluated by a relation in which the parameters are the hardness and size of the crack initiation area, independent of the heat treatment conditions. This result was discussed based on the observations of crack growth behavior and fracture surface.
  • 細井 厚志, 高村 啓吾, 佐藤 成道, 川田 宏之
    2012 年 78 巻 791 号 p. 1000-1012
    発行日: 2012年
    公開日: 2012/07/25
    ジャーナル フリー
    A method to predict quantitatively the first of transverse cracks accumulated in the various types of [0m/90n]s cross-ply carbon fiber reinforced plastic (CFRP) laminates subjected to fatigue loading was proposed. On the basis of the assumption that the mechanism of transverse crack initiation is equivalent to that of transverse crack increase in the earlier stage of fatigue within low transverse crack density, the cycles at which a transverse crack initiates are calculated by applying the normalized modified Paris law, which shows the relationship between the transverse crack density growth rate and the normalized energy release rate range associated with the transverse crack formation. When the constants of the normalized modified Paris law are given with an arbitrary cross-ply laminate, the proposed method makes possible to predict the initiation of a transverse crack in the other various types of cross-ply laminates under fatigue loading by only measuring the stress at which a transverse crack initiates under static tensile loading.
  • 橋村 真治, 山田 直樹, 戸田 均
    2012 年 78 巻 791 号 p. 1013-1022
    発行日: 2012年
    公開日: 2012/07/25
    ジャーナル フリー
    In this study, influence of nut configuration on fatigue characteristic of bolt/nut assembly under transverse vibration has been investigated. In the experiments, the apparent fatigue limits were investigated for two bolt/nut assemblies tightened with a flange nut and a tapered nut. The results showed that the apparent fatigue limit of the bolt/nut assembly tightened with the tapered nut was higher than that of the flange nut. Its causes were revealed by FE Analyses. As the result, it could be seen that a difference of nut inclinations when the assembly received the transverse load caused the difference of fatigue limits. It was also seen that the nominal stresses at root of the first thread were different even if the same transverse load was applied to the bolt/nut assembly.
  • 服部 修次, 角一 将也
    2012 年 78 巻 791 号 p. 1023-1032
    発行日: 2012年
    公開日: 2012/07/25
    ジャーナル フリー
    In steam piping system containing liquid droplets, pipe wall is sometimes damaged by droplet impingement. One of the most important parameters affecting erosion is impact angle. No research has been conducted for the impact angle dependence on erosion for pipe steels. In this study, jet nozzle was used for the high pressure impingement tests of S15C, SUS304 and STPA24, and spray nozzle for the tests of pure aluminum. The MaxDER (Maximum Depth of Erosion Rate) for these three steels was expressed as sinnθ and the exponent is 1.2 - 2.5 irrespective of type of steels. Jet nozzle tests with 90°specimen showed that liquid droplet impingement was weakened possibly due to the liquid film formation. Spray nozzle tests revealed that the erosion can be estimated safely in terms of V=V0sinθ .
  • 仁村 彰宏, 矢田 浩基, 服部 修次
    2012 年 78 巻 791 号 p. 1033-1043
    発行日: 2012年
    公開日: 2012/07/25
    ジャーナル フリー
    Research on cavitation erosion in liquid metal is very important to confirm the safety of fast breeder reactor and industrial machinery. However, the researches on the cavitation erosion in liquid metal have not been achieved as compared with the study in water. In this study, the effect of temperature on cavitation erosion in liquid metal was clarified. A new cavitation erosion apparatus was developed to carry out erosion test at high temperature in liquid metal, and was confirmed to offer a stable test performance. Test liquid was lead-bismuth alloy and specimen was 9Cr steel and SUS304 steel. The results showed that cavitation erosion rate increases with an increased temperature and reached a peak value at a relative temperature of about 70 degree (the relative temperature was defined as 0° for freezing temperature and 100° for boiling temperature). The erosion rate prediction was discussed for sodium. The erosion rate in sodium was estimated to be located halfway from the rates between lead-bismuth and deionized water.
  • 石塚 和則, 高橋 剛, 柴野 純一, 三浦 節男, 小林 道明, 岩渕 義孝
    2012 年 78 巻 791 号 p. 1044-1055
    発行日: 2012年
    公開日: 2012/07/25
    ジャーナル フリー
    It has been reported that pitting corrosion occurs in stainless steel under the specific conditions which a corrosion factor superimposes. In cold and snowy area, welded structures on the outdoors are exposed to combinational environment of the salt damage and the freezing damage, in which the corrosive solution containing Cl- chlorine ions from the sea breeze and snow melting agents undergo freezing-thawing cycles during the winter. The cause of pitting corrosion phenomenon which occurs in the welded stainless steel under such a combinational environment has not yet been clarified. In the previous report, accelerated pitting corrosion is confirmed to have occurred as a result of concentration cell corrosion due to a local concentration of Cl- chlorine ion around a weld bead during freezing and thawing of the solution. In the present study, it is investigated that the effect of corrosive factors on the progression of pitting corrosion in welded austenitic stainless steel under freezing and thawing corrosive environment. Austenitic stainless steel SUS 304 plates with bead-on-plate welding are used as specimens. The specimens are fully immersed in FeCl3 solution. The freezing-thawing environment is created by temperature cycling form 20°C to -20°C. One cycle of freezing-thawing is 12 hours and 24 hours. As a result, in the austenitic stainless steels under a freezing and thawing corrosive environment, it became evident that sensitive metallographic structures influences an occurrence of large scale pitting corrosion, and a stress level influences an accelerated progression of the pitting corrosion.
  • 小林 志好, 大塚 年久, 岸本 喜直, 矢口 尚之助, 齋藤 茂
    2012 年 78 巻 791 号 p. 1056-1064
    発行日: 2012年
    公開日: 2012/07/25
    ジャーナル フリー
    In a previous paper, it was reported that the tensile strength of optical glass fiber spliced by arc fusion method decreased due to the decrease of fracture toughness in a heat affected zone. In this study, tensile tests of heat treated optical glass fibers changed the heating temperature and heating time were carried out. Obtained results were as the follows: The tensile strength of optical glass fiber began to decrease from heating temperature of about 500K and reached the bottom at the heating temperature of about 600K. Moreover, it decreased with the increase in the heating time. In order to clarify the reason of tensile strength reduction, heat flows of optical glass fiber and optical glass fiber spliced by arc fusion method were compared by using the differential scanning calorimetry. It was found that the structure of heated optical glass fiber transformed from 500K to 600K. Therefore, the structure education of optical glass fiber spliced by arc fusion method was performed by using Raman spectroscopy. As a result, the tensile strength reduction of heat affected zone resulted from a thermal residual stress due to a transformation from the three-membered ring to the six-membered ring.
  • 村松 眞由, 志澤 一之
    2012 年 78 巻 791 号 p. 1065-1078
    発行日: 2012年
    公開日: 2012/07/25
    ジャーナル フリー
    We modeled previously a crystal lattice as an elastic bar with equivalent atom mass. Applying such a lattice model to recrystallization phenomena, we developed conservation laws of mass, momentum, angular momentum and energy for mixture consisting of recrystallized phase and matrix. Also, the increase law of entropy for mixture was obtained. However, in the previous works, only general principles are formulated and material properties are not introduced into them. Moreover, it is still unclear which conservation laws are corresponding to the governing equations of phase-field models. In this paper, balance equations of mass for single phase and spin angular momentum are rewritten by use of order parameter and crystal orientation, respectively. Constitutive equations for fluxes of order parameter and crystal orientation are thermodynamically derived so that the entropy inequality is not violated. Substituting the constitutive equations of flux into the balance equations, basic equations are obtained. In these equations, the mass source term and diffusion coefficients are modeled so as to synchronize with the temporal change of grain boundary energy. Neglecting the conservative term of the equation of crystal orientation and then integrating it with respect to time, three-dimensional KWC type phase-field equations are derived. Finally, reducing the obtained equations to two-dimensional ones, it is shown that the present equations result in the conventional KWC type phase-field model.
  • 吉田 圭吾, 池田 忠繁, 上田 哲彦
    2012 年 78 巻 791 号 p. 1079-1089
    発行日: 2012年
    公開日: 2012/07/25
    ジャーナル フリー
    A simple constitutive model for temperature dependent behavior of ferroelectric materials is developed. To model the temperature dependent behavior of the ferroelectric materials, the paraelectric phase is considered in addition to four types of ferroelectric variants in the ferroelectric phase. These ferroelectric variants are assumed to be connected in series to each other, whereas the paraelectric phase is assumed in parallel to the ferroelectric phase. Volume fraction of the paraelectric phase is to increase with increase in temperature up to the Curie temperature. To verify the validity of the present model, relationships of electric displacement and strain versus electric field were measured at several temperatures and the results from the model were compared with those by the measurement. The comparison reveals that the present constitutive model can well predict the temperature dependent behavior quantitatively. This implies that the present simple model can make it easy to understand the physical mechanism of ferroelectric materials and provides a convenient tool to design smart structures containing the ferroelectric materials over the wide range of temperature.
  • 中楯 浩康, 馬橋 洋人, 張 月琳, 角田 陽, 青村 茂
    2012 年 78 巻 791 号 p. 1090-1099
    発行日: 2012年
    公開日: 2012/07/25
    ジャーナル フリー
    Diffuse axonal injury (DAI), a major component of traumatic brain injury, has been suggested to result from inertial forces applied on the head. DAI is a manifestation of microstructural cellular trauma and is accompanied by distinct morphological changes. Focal axonal swellings are the morphological hallmarks of DAI pathology and lead to the disconnection of neurons from target tissues resulting in neuronal death. Our goal is the understanding of the quantitative relation between strain acting on the axons and generation of axonal swellings. In present study, we developed an in vitro two dimensional stretch device that reproduced axonal swellings of in vivo DAI, and verified the input-output relation of the device. Then using this device, we exposed PC12 cells, which extend structurally axon-like cylindrical protrusions in culture, to 10% or 20% strains and measured the length of neurites and number of swellings in PC12 cells until 48 hours after the exposure to stretch by microscope observation. As a result, the length of neurites transiently shortened at 5 minutes and 1 hour after exposure to strain compared to those before exposure to strain. On the other hand, swellings were generated at 5minutes after exposure to strain and were the most in number at 1 hour after exposure to strain compared to swellings in normal neurites. Moreover, the number of swellings in neurites exposed to 20% strain was significantly larger than that exposed to 10% strain at 5 minutes after exposure to strain. These results suggest that production of axonal swellings correlate with strain magnitude acting on the axons.
技術論文
  • 町田 秀夫, 荒川 学, 波木井 順一, 濱中 鉄也
    2012 年 78 巻 791 号 p. 1100-1114
    発行日: 2012年
    公開日: 2012/07/25
    ジャーナル フリー
    Deformation of piping system subjected to dynamic seismic load is restricted by many supports, and it may not deform as large as total elongation even if excessive dynamic seismic load acts on it. This tendency was verified based on many experimental results, and limitation on primary stress was removed and fatigue evaluation was only required for dynamic seismic loads in revised aseismic design codes (JEAC4601-2008). Thus, structural integrity evaluation method for unflawed pipes has been clear, but that for flawed pipes is not established until now. This paper describes the examinations on the fracture assessment method in case dynamic seismic load acts on the pipes having circumferential cracks. If plastic deformation occurs in piping elements, increase of response stress in the elements will decline compared with elastic condition, but response displacement does not decline greatly. That is, the response of piping system subjected the dynamic seismic load is close to deformation control conditions. This aspect was checked by using the finite element analysis for some piping elements and piping systems, and the fracture assessment methods of pipes having circumferential flaws subjected to dynamic seismic loads was proposed.
ノート
  • 高瀬 康, 野田 尚昭, 蘭 欣, 道中 健吾, 小田 和広
    2012 年 78 巻 791 号 p. 1115-1119
    発行日: 2012年
    公開日: 2012/07/25
    ジャーナル フリー
    Although a lot of interface crack problems were previously treated, few solutions are available under arbitrary material combinations. This paper deals with an edge interface crack in a bonded finite plate under bending. Then, the effects of material combination on the stress intensity factors are discussed. To obtain the interface stress intensity factor very accurately, a useful method is presented on the basis of the stress values at the crack tip calculated by the finite element method. The stress intensity factors are indicated in charts and compared with the ones under tension. The maximum and minimum values of the stress intensity factors are also discussed under arbitrary material combinations.
  • 髙田 剛, 日出間 るり, 古川 英光
    2012 年 78 巻 791 号 p. 1120-1124
    発行日: 2012年
    公開日: 2012/07/25
    ジャーナル フリー
    After 2001, several methods have been devised to improve the mechanical strength of gels extraordinarily. It was a trigger to use gels as a new industrial materials, since gels had been considered difficult for industrial materials because of their weakness. The purpose of this study is to create novel composite materials, which realizes the further high strength of gels by adding fiber to the gels. We evaluated the mechanical properties of the gels, containing a very small amount of the fiber, in order to quantify how the fiber works for enhancement of the gels. It is found that to improve the adhesion between fiber and the gel matrix is important for increasing the mechanical strength of the newly proposed gels. Since there are many kinds of gels and fibers, it becomes possible to achieve a dramatic enhancement of the strength if we find an appropriate combination for rigid adhesion.
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