日本機械学会論文集 A編
Online ISSN : 1884-8338
Print ISSN : 0387-5008
74 巻, 748 号
選択された号の論文の13件中1~13を表示しています
  • 朝田 誠治, 平野 隆, 永田 徹也, 笠原 直人
    2008 年 74 巻 748 号 p. 1485-1492
    発行日: 2008/12/25
    公開日: 2011/03/02
    ジャーナル フリー
    A structural evaluation method by using elastic-plastic finite element analysis has been developed and published as a code case of Rules on Design and Construction for Nuclear Power Plants (The First Part : Light Water Reactor Structural Design Standard) in the JSME Codes for Nuclear Power Generation Facilities. Its title is “Alternative Structural Evaluation Criteria for Class 1 Vessels Based on Elastic-Plastic Finite Element Analysis” (NC-CC-005). This code case applies elastic-plastic analysis to evaluation of such failure modes as plastic collapse, thermal ratchet, fatigue and so on. Advantage of this evaluation method is free from stress classification, consistently use of Mises stress and applicability to complex 3-dimensional structures which are hard to be treated by the conventional stress classification method. The evaluation method for plastic collapse has such variation as the Lower Bound Approach Method, Twice-Elastic-Slope Method and Elastic Compensation Method. Cyclic Yield Area (CYA) based on elastic analysis is applied to screening evaluation of thermal ratchet instead of secondary stress evaluation, and elastic-plastic analysis is performed when the CYA screening criteria is not satisfied. Strain concentration factors can be directly calculated based on elastic-plastic analysis.
  • 河井 昌道, 張 剣奇, 肖 毅, 八田 博志
    2008 年 74 巻 748 号 p. 1493-1500
    発行日: 2008/12/25
    公開日: 2011/03/02
    ジャーナル フリー
    Formulation of a phenomenological viscoplasticity model that accounts for differences in tensile and compressive nonlinear rate-dependent behaviors of unidirectional carbon fiber-reinforced composites in a given off-axis direction is attempted. Effective stress and effective viscoplastic strain for transversely isotropic materials are derived from a three-dimensional pressure-modified Hill's anisotropic yield criterion, and they are reduced to the forms for plane state of stress. A plane-stress viscoplasticity model furnished with a capability to predict the phenomena raised above is formulated on the basis of the concept of overstress and the irreversible thermodynamics with internal variables. A shear constraint parameter, in which the influence of the compressive transverse stress on the shear flow resistance is reflected, is taken into account in defining a modified form of effective viscoplastic strain rate to enhance the predictive capability of the viscoplasticity model. The viscoplasticity model discussed in the present study is designed so as to be reduced to the viscoplasticity model of the Gates-Sun type developed in the previous study, which allows easy identification of material constants. Validity of the proposed viscoplasticity model is evaluated by comparing with results of off-axis tension and compression tests on a unidirectional carbon/epoxy composite at different strain rates.
  • 河井 昌道, 斎藤 覚
    2008 年 74 巻 748 号 p. 1501-1510
    発行日: 2008/12/25
    公開日: 2011/03/02
    ジャーナル フリー
    The off-axis compressive strength and its rate dependence of a unidirectional carbon/epoxy laminate are examined for various fiber orientations at high temperature. Static compression tests are carried out at two different strain rates of 0.1 and 10%/min for each fiber orientation. The fiber-orientation and strain-rate dependence of off-axis compressive strengths and associated failure modes are first discussed. The off-axis compressive strengths are compared with the off-axis tensile strengths at the same strain rates and test temperature, and differences between the ultimate off-axis strengths in tension and compression are quantified. Then, the Hoffman failure criterion that distinguishes between the off-axis strengths in tension and compression is tested for the accuracy of prediction of the different off-axis tensile and compressive strengths and the associated failure envelope at different strain rates. It is demonstrated that while the fiber orientation dependence of the off-axis tensile and compressive strengths are predicted with reasonable accuracy, the failure envelope associated with off-axis compression is poorly described using the Hoffman failure criterion. This observation suggests that consideration of the influence of the transverse compressive stress on the in-plane shear strength along fibers is essential for accurate prediction of failure envelope. Finally, a modified form of the Hoffman failure criterion that meets the requirement is proposed, and it is demonstrated to have an improved predictive capability compared with the original form.
  • 加藤 昌彦, 野間 正載, 谷田 芳夫, 菅田 淳
    2008 年 74 巻 748 号 p. 1511-1518
    発行日: 2008/12/25
    公開日: 2011/03/02
    ジャーナル フリー
    In order to clarify the influence of crack density on friction and wear properties of electroplated chromium molybdenum films, the films deposited on tool steel substrate under high and normal current densities were used. The crack density of the film electroplated at high current density was higher than that electroplated at normal current density. Friction and wear properties of the films were evaluated by using a pin-on-disk type wear testing machine under un-lubricated condition. The results showed that the wear rate of both the film and pin was decreased remarkably by increasing crack density. The friction coefficient of the films indicating about 0.2 at the beginning of the wear test increased with increasing the number of rotation cycles and reached a stable value. Detailed observation of wear scar and wear products showed that flake-like delamination of film occurred by repeating sliding load, and friction and wear properties had close relationship with the flake-like delamination property.
  • 三島 卓大, 姜 旻佑, 青野 雄太, 野口 博司
    2008 年 74 巻 748 号 p. 1519-1527
    発行日: 2008/12/25
    公開日: 2011/03/02
    ジャーナル フリー
    The fatigue crack growth property of prestrained carbon steels was investigated to predict the fatigue life of the structures and mechanical parts, the materials of which were prestrained by metal working such as machining, pressing, and forging. In this study, the relationship between the ultimate tensile strengthσ B of prestrained specimens and the crack growth rate dl/dN is the focus. The following results were obtained. Under the large-scale yielding (LSY) condition, there is a correlation between dl/dN and σB, where the dl/dN versus σnal characteristics are determined by σB regardless of the degree of prestrain. Under the small-scale yielding (SSY) condition, dl/dN appears to be determined by the stress intensity factor range ΔK rather than σB, in comparison with the case under the LSY condition. In addition, the relationship between σB and the cyclic yield strength σyc is discussed in terms of the cyclic stress-strain characteristics of prestrained 0.1% carbon steel and other nonstrained carbon steels. It is considered that σB represents the material resistance against the plastic deformation by which fatigue cracks propagate regardless of the existence of prestrain.
  • 松岡 三郎, 堤 紀子, 村上 敬宜
    2008 年 74 巻 748 号 p. 1528-1537
    発行日: 2008/12/25
    公開日: 2011/03/02
    ジャーナル フリー
    In order to investigate the influence of hydrogen and test frequency on fatigue crack growth rate, fatigue crack growth tests (R=0) were conducted on hydrogen charged and uncharged specimens of a 0.08 mass%C low carbon steel pipe at test frequency 0.001-10 Hz. Following the fatigue crack growth tests, the test for producing a stretch zone was carried out. Observing the morphologies of the striation and stretch zone on the fracture surface and slip bands on the specimen surface, it was revealed that uncharged specimens have no dependency of crack growth rate on test frequency and on the other hand, the crack growth rate of hydrogen charged specimens at the test frequency below 0.01 Hz is approximately 10 times faster than that of uncharged specimens. There exists an upper limit of the increase in crack growth rate of the hydrogen charged specimens at test frequency below 0.01 Hz. The degree of crack tip blunting is very different between uncharged and charged specimens. The crack tip is fully blunt and CTOD is large in uncharged specimens, while the crack tip is very sharp and CTOD is very small in charged specimens. Nevertheless, the stretch zone width of hydrogen charged specimens is approximately equal to that of uncharged specimens. Considering the increase in the crack growth rate and the morphology of the striation and stretch zone, it has been concluded that the acceleration of fatigue crack growth of hydrogen charged specimens is caused by the continuous hydrogen enhanced slip deformation ahead of crack tip (Hydrogen Enhanced Successive Fatigue Crack Growth, HESFCG).
  • 野田 尚昭, 吉村 慎平, 川原 啓史, 露成 正一
    2008 年 74 巻 748 号 p. 1538-1543
    発行日: 2008/12/25
    公開日: 2011/08/16
    ジャーナル フリー
    Usually, development of automobile brake hose and power steering hose has been realized through investigating several actual prototype hoses experimentally. Recently, high durability for brake hose has been required because periodic renewing the brake hoses has not been requested anymore. In this study, FEM stress analysis has been applied to the crimped portion of hydraulic brake hose in order to promote the development of the automobile hoses more efficiently. It is found that large normal stresses σn, which may be helpful for the sealing performance, appear at the crimped portion between the nipple and inner rubber. The results suggest that several grooves putting at the surface of nipple are effective for causing large σn, which may improve the sealing performance and hose life. The effect of compression set of the rubber on the sealing performance is investigated, and the life of hydraulic brake hose is estimated form the maximum stress appearing near the groove on the nipple.
  • 山下 恵太郎, 島本 聡
    2008 年 74 巻 748 号 p. 1544-1549
    発行日: 2008/12/25
    公開日: 2011/03/02
    ジャーナル フリー
    For utilizing SMA smart composite materials effectively it is essential to understand how shape recovery force is dynamically generated. However, the standard strain metrology for composite materials cannot accurately evaluate shape recovery force due to the thermal expansion of the matrix. For precise evaluation, electric resistance change by Joule heating and in its cooling process is emphasized in this research. Especially, significant points of electric resistance change are used as markers for the phase transformation progress of SMA. As a result, it is confirmed that there is an excellent correlation between shape recovery force and electric resistance. Measuring electric resistance change of SMA is very effective to evaluate dynamic behavior of shape recovery force of SMA in the composite materials. Using the proposed method, information regarding the shape recovery force formation of the SMA single fiber and the smart composite materials under different operation temperature is confirmed.
  • 回転曲げに静的ねじり負荷が重畳した場合
    小野 勇一, 李 成, 北岡 征一郎
    2008 年 74 巻 748 号 p. 1550-1556
    発行日: 2008/12/25
    公開日: 2011/03/02
    ジャーナル フリー
    A copper electroplating stress measurement method is applied to an element that changes the biaxial stress ratio in stress cycle over time. First, we originally produced a fatigue testing machine that was able to produce the combined stress state of rotating bending and static torsion. Since static torsion makes the biaxial stress ratio change over time, we examined the effect of static torsion on the grain growth by comparing the plane bending tests that do not change the biaxial stress ratio. The critical shearing stress at which grain growth occurs for a prescribed number of cycles and the grain growth rate almost the same values in the plane bending test and the rotating bending-static torsion test. These results mean that the static stress that is superposed on cyclic stress has no effect on grain nucleation and grain growth. The main reason for this result is that the magnitude and direction of the maximum shearing stress amplitude are equal in both cases.
  • 戸伏 壽昭, 櫻木 稔巳, 杉本 義樹, 齋木 努
    2008 年 74 巻 748 号 p. 1557-1564
    発行日: 2008/12/25
    公開日: 2011/03/02
    ジャーナル フリー
    In order to develop a rotary driving element with a shape-memory alloy (SMA) thin strip, the torsional deformation property, cyclic deformation property and torsional fatigue property of a TiNi SMA thin strip were investigated. The results obtained can be summarized as follows. (1) During twisting the SMA thin strip, the martensitic transformation appears along the edge of the thin strip and develops toward the central part. The rate of increase in the tensile strain of the edge increases gradually with an increase in angle of twist. (2) Torque increases with an increase in angle of twist. The torsional deformation properties change slightly under cyclic torsion. (3) With respect to the fatigue properties, the number of cycles to failure decreases with an increase in the angle of twist. The fatigue life in pulsating torsion is five times longer than that in alternating torsion at the same angle of twist. (4) The two-way rotary movement of an opening and closing door model was demonstrated. Therefore, a rotary driving element with a small and simple mechanism can be developed by using the SMA thin strip.
  • 高橋 航圭, 轟 章, 松崎 亮介
    2008 年 74 巻 748 号 p. 1565-1572
    発行日: 2008/12/25
    公開日: 2011/03/02
    ジャーナル フリー
    Delamination of CFRP structure is detected by means of electrical resistance change due to Joule heating in the present study. A CFRP beam is heated up by applying electric current through electrodes mounted on the surface. When the CFRP beam is heated up, the thermal expansion at the part with a delamination is different from that at the undamaged part, and the difference of the thermal expansion affects the electrical resistance change with elevated temperature because CFRP has piezoelectricity. The electrical resistance changes between the electrodes are measured using bridge circuits just like using conventional strain gauge. In addition, the effect of electrode's damage on the electrical resistance change is also considered because the quality of the electrode is important to identify delamination. Electrical resistance change due to Joule heating is measured using a cross-plied CFRP beam with a delamination and electrode's damage, and as a result, delamination detection is even possible with a damaged electrode.
  • 高橋 航圭, 轟 章, 松崎 亮介
    2008 年 74 巻 748 号 p. 1573-1579
    発行日: 2008/12/25
    公開日: 2011/03/02
    ジャーナル フリー
    Strain monitoring of CFRP structure by measuring electrical resistance change has attracted attention over the years. High electrical conductivity of carbon fibers enables to measure the strain by making electrodes on the structure's surface and using bridge circuit as conventional strain gauge. Electrical resistance change method, however, is difficult to specify the gauge length because electric current is applied directly to the structure, and the current path depends on the stacking sequences, fiber volume fraction, and electrode's location. It is also difficult to measure the electrical resistance changes at different parts simultaneously because the outputs may interfere with each other due to overlapping of current paths inside the structure. In this study, three electrodes are connected to each bridge circuit to prevent electrical interference when the electrical resistance changes are measured simultaneously, whereas electrical resistance measurements normally use two electrodes. The proposed method puts ground electrodes every other so that current path could be limited between the ground electrodes. Only the strain between ground electrodes affects the electrical resistance output, and it makes simultaneous measurements at different position possible.
  • 斉藤 一哉, 野島 武敏, 萩原 一郎
    2008 年 74 巻 748 号 p. 1580-1586
    発行日: 2008/12/25
    公開日: 2011/03/02
    ジャーナル フリー
    Dia-Core is a newly devised core panel formed by gluing/welding two same shaped panel pieces which have periodical indents. It has good cost performance due to easy press forming. Therefore, it is expected to become new core material which can be compete with honeycombs from the total points of view. The basic model of Dia-core is based on Octet-Truss developed by Fuller, and it consists of tetrahedra and octahedra. By varying the geometrical patterns that appear on the panel surfaces, various shaped modified models are devised systematically. In this paper, it is clarified that these pattern variations can be ruled by two geometric parameters, truncation [k ] and separation [s]. Next, by numerical simulation using FEM, effects of these two parameters on the representative properties of Dia-Core, bending and in-plane shear rigidity, are clarified.
feedback
Top