材料
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
49 巻 , 6Appendix 号
選択された号の論文の12件中1~12を表示しています
  • Yoshiaki OKUI, Hideyuki HORII
    2000 年 49 巻 6Appendix 号 p. 65-73
    発行日: 2000/06/15
    公開日: 2009/06/03
    ジャーナル フリー
    This article presents a review of the research work related to the micromechanical modeling of behavior of hard rock under compression. To this end, it initially provides observed macroscopic behavior of compressive rock for both time-independent and -dependent cases. It proceeds with a review of microscopic observations of rock failure including recent techniques in rock experiments. Crack growth laws in rock for both short- and long-term loading are next reviewed. Finally, micromechanical models employed in literatures and associated continuum theories based on micromechanics are introduced.
  • Shinzo KOBAYASHI, Hiroyuki SUZAKI
    2000 年 49 巻 6Appendix 号 p. 74-79
    発行日: 2000/06/15
    公開日: 2009/06/03
    ジャーナル フリー
    The subject of sliding friction is of great tribological importance and has been studied extensively on an engineering basis. However, effects of the underlying microscopic factors that control friction and wear have not been elucidated. The present study is a part of the effort relating to sliding deformation under impact and high speed conditions. The method used is to scratch a diamond quadrangular pyramid on the accurately finished (111) crystal face of αCu-Al single crystals using a single pendulum impact testing device. The study was made to examine the appearance of slip patterns and the topographical deformation on the surface caused by scratch. Then, dislocation patterns on the sub-surface exposed by electrolytical polishing were examined. Furthermore, comparisons of the experimental results obtained in the present study with the results obtained under the condition of static scratch were made. From the experimental results, the following conclusions were obtained. Slip traces with the slip systems of the (111) [101] [011], (111) [101] and (111) [011] are observed on the surface after the scratch in the [112] direction. While in the [110] scratch, (111) [101] and (111) [101] slip traces were observed. The curved slip traces which were not observed in the static scratch appeared around the scratched track in each scratch. These slips are active on the crystal {111} faces which have divergent arrangement towards the inside just below at the surface, and on the convergent faces in the deeper region.
  • Shigeru OGAWA, Shuichi HAMAUZU, Toshio KIKUMA
    2000 年 49 巻 6Appendix 号 p. 80-87
    発行日: 2000/06/15
    公開日: 2009/06/03
    ジャーナル フリー
    As a notion of strain compatible with the theory of plasticity having the plastic potential of von Mises type with the normality principle as flow rule, the strain tensor is defined by integrating the rate of deformation tensor considering the material spin with the rotation tensor. For a group of elastic-plastic continua exhibiting infinitesimal elastic and finite plastic deformation, elastic-plastic decomposition of the strain tensor is established, and it is proved that the elastic strain tensor has the exact physical meaning and that the stress tensor can be calculated through the generalized Hooke's law with the elastic strain tensor without any ambiguity.
  • Shigeru OGAWA, Shuichi HAMAUZU, Toshio KIKUMA
    2000 年 49 巻 6Appendix 号 p. 88-95
    発行日: 2000/06/15
    公開日: 2009/06/03
    ジャーナル フリー
    Based on an explicit definition of finite strain tensor, an implicit finite element formulation for finite deformation of elastic-plastic continua is proposed. Adopting the von Mises yield function, isotropic hardening rule and the generalized Hooke's law, the flow rule for the plastic strain rate is analytically integrated to complete the finite element formulation based on the Lagrangian description of virtual work principle. The performance of the finite element code is evaluated through the two dimensional analysis of a plane strain uniaxial tensile test of block-type specimens.
  • Tadashi ABE, Toshiaki SAWANO, Tetsukazu KIDA, Masaaki HOSHINO, Kiyoshi ...
    2000 年 49 巻 6Appendix 号 p. 96-103
    発行日: 2000/06/15
    公開日: 2009/06/03
    ジャーナル フリー
    Cracks and damage frequently occur in RC slabs of highway bridges due to the characteristics of the road surface, difference in the level of expansion joints, and other dynamic effects of running vehicles. In this research, the effect of running loads on the flexural load-carrying capacity of RC beams and the dynamic effects of running loads are experimentally evaluated. The conclusions are as follows: (1) A constant running load reduces the flexural load-carrying capacity of the RC beam by 10% compared to the case of a static load. (2) Both strain and deflection of reinforcement for a 10%-running vibration load and a 20%-running vibration load increase by 17%-19% and 33%-35%, respectively, compared to a constant running load. (3) The impact coefficients for a 10%-running vibration load and a 20%-running vibration load are 0.239 and 0.374, respectively, indicating values which are higher than the amplitude of the load applied on the beam.
  • Hideki YAMANE, Zen-ichiro MAEKAWA, Hajime SAKANO
    2000 年 49 巻 6Appendix 号 p. 104-109
    発行日: 2000/06/15
    公開日: 2009/06/03
    ジャーナル フリー
    Tensile properties and the phase morphologies of ABS resins with various rubber particle sizes and graft ratios of SAN are examined. Large rubber particles disperse well in ABS resins irrespective of the graft ratio. On the other hand, the graft ratio affects the dispersion state of the small rubber particle, particles with high graft ratio disperse well and those with low graft ratio tend to coalesce into large aggregates. These differences of the morphology strongly alter the deformation mechanism, such as craze formation and cavitation in the rubber particles. The effects of mixing of ABS resins with various graft ratio and particle size on the mechanical properties and phase morphology are also discussed.
  • Junko ITOH, Keizo KISHIDA, Koji NAKAMURA, Masayuki MIYAZAKI, Shigeo OH ...
    2000 年 49 巻 6Appendix 号 p. 110-115
    発行日: 2000/06/15
    公開日: 2009/06/03
    ジャーナル フリー
    Stress and deformation of cathode ray tubes (CRTs) under atmospheric pressure and implosion protection band tightening were analyzed using a finite element method (FEM). The stress and deformation of the tubes were measured experimentally by using strain gages and three-dimensional position measuring techniques. The experimental results showed close agreements with those of the simulation. The location of the highest tensile stress and the effects of tightening of the implosion protection bands on the stress and deformation of the tube were clarified. Long-term reliability of the tubes were also studied by using these simulation techniques and the strength characteristics of the CRT glass taking account of surface roughness and delayed fracture.
  • Atsuhiro KOYAMA, Atsushi SUGETA, Yoshihiko UEMATSU, Masahiro JONO
    2000 年 49 巻 6Appendix 号 p. 116-122
    発行日: 2000/06/15
    公開日: 2009/06/03
    ジャーナル フリー
    In order to investigate cyclic fatigue crack growth behavior of a gas-pressure-sintered silicon nitride under constant and variable amplitude load sequences, fatigue crack growth tests were carried out using compact type (CT) specimens. The crack length and macroscopic crack closure were measured using an unloading elastic compliance method. Grain interlocking was observed around crack wake in all fatigue test conditions, which implied fatigue crack growth of this material was associated with progressive degradation of the grain interlocking by cyclic loading. The fatigue crack growth rate, da/dn, under constant amplitude loading was controlled not only by the maximum stress intensity factor, Kmax, but also the stress amplitude, while Kmax was the most important factor in cyclic fatigue crack growth. The overload and high-level load excursion produced the acceleration of fatigue crack growth and the downward shift of crack closure point under low-level loading. This decrease was thought to result from much severer crash or frictional wear of grain interlocking and the crack closure could explain the acceleration behavior qualitatively.
  • Samsul RIZAL, Hiroomi HOMMA
    2000 年 49 巻 6Appendix 号 p. 123-130
    発行日: 2000/06/15
    公開日: 2009/06/03
    ジャーナル フリー
    The influence of the specimen thickness on fracture have been investigated under static loading and interpreted in terms of stress conditions near a crack tip, namely crack tip plasticity under plane strain to plane stress condition. This work investigates the effect of stress conditions on dimple fracture produced by impulsive stress intensity of 20, 40 and 80μs duration, experimentally and numerically. The fractographic observation shows that several voids nucleated at inclusions ahead of a crack tip coalescence with each others to form a large void, called a dominant void in this work, and that a size of the dominant void decrease as the pulse duration decreases from 40μs to 20μs, whereas the dominant void is nucleated at the constant distance from the crack tip. Finite element analysis shows that the hydrostatic stresses ahead of a crack tip can explain the experimental results that the dynamic fracture toughness of a 10mm thick specimen is much smaller than that of a 3mm thick specimen and that the void nucleation site is independent of the specimen thickness.
  • Nihat AKKUS, Masanori KAWAHARA
    2000 年 49 巻 6Appendix 号 p. 131-135
    発行日: 2000/06/15
    公開日: 2009/06/03
    ジャーナル フリー
    This paper reports on the improvement of the bending strength of thin circular pipes by reinforcing nodes. Thin composite pipes are attractive to the design of structural parts owing to their high stiffness and strength with less weight, and are applied to various mechanical parts such as rotating shafts, robot arms, and other sports and leisure goods. However, the bending stiffness of composite pipes are often reduced under heavy bending loads owing to the change in sectional shape. Specimen pipes with and without reinforcing nodes were fabricated by filament winding of carbon fibers impregnated with epoxy resin in different fiber angles and reinforcement spacings. Geometry of tested pipes were of 21 (diameter)×0.5 (thickness)×1000 (length) (mm). Reinforced specimens were fabricated by winding angles of 20, 30 and 45° with reinforcement spacings of 60, 90, 180mm. Four-point bending tests were conducted to examine the bending behaviors of the pipes. Experimental results revealed a distinct effect of the reinforcing rings to delay the onset of the sectional ovalization.
  • Sande GAO, Keijiro NAKASA, Masahiro KATO
    2000 年 49 巻 6Appendix 号 p. 136-143
    発行日: 2000/06/15
    公開日: 2009/06/03
    ジャーナル フリー
    In order to characterize the “Repeating-division type” cracking pattern which is often observed in the brittle coating on a ductile substrate under equi-biaxial tension, the bulge tests were carried out on steel disks with WC-Co coating which was deposited by high-velocity flame spraying. Moreover, an elastic-plastic analysis was applied to the division process of coating to derive the relation among crack interval, tensile stress and strain of substrate at the division, coating and substrate thickness, strength of coating, interfacial strength between coating and substrate, and material's constants. The characteristics of the division process calculated from the analytical equation agree semi-quantitatively well with the experimental results that the crack interval decreases with increasing tensile stress and increases with increasing coating thickness.
  • Effect of Glass Particle Size on Microstructure and Electrical Property
    Haruhisa SHIOMI, Kaori UMEHARA
    2000 年 49 巻 6Appendix 号 p. 144-149
    発行日: 2000/06/15
    公開日: 2009/06/03
    ジャーナル フリー
    An attempt was made to improve the electrical properties of SnO2-glass composites by dispersing Cu particles with low resistivity and positive temperature coefficient of resistance (TCR) in the glass matrix. Cu metal particles were precipitated by reducing Cu2O previously dissolved into the matrix glass by adding LaB6 as a reducing agent. The effect of the glass particle size, which influences the homogeneity of LaB6 dispersion in the powder mixture before firing, on the Cu precipitation in the glass matrices and the electrical properties of the glass composites was investigated. When fine glass powder was used, dense glass composites were obtained. When coarse glass powder was used, LaB6 easily reduced SnO2 as well as Cu2O and thus the amount of metal precipitation was larger than that in the glass composite made from fine glass powder. However, in the glass composites prepared by the coarse glass powder, large pores formed by the evaporation of SnO, a reduction intermediate from SnO2. The glass composite prepared by the fine glass powder showed higher electrical conductivity (σ) and smaller negative TCR than that made from the coarse glass powder although the amount of metal formed by reducing reaction was small. However, when the fine glass powder was used, the glass composite showed more significant decrease in the σ and TCR at high LaB6 content than the glass composite made from the coarse glass powder.
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