JSME International Journal Series A Solid Mechanics and Material Engineering
Online ISSN : 1347-5363
Print ISSN : 1344-7912
ISSN-L : 1344-7912
Volume 42 , Issue 2
Showing 1-19 articles out of 19 articles from the selected issue
  • Hideaki KASANO
    1999 Volume 42 Issue 2 Pages 147-157
    Published: April 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    In this paper, recent works on impact perforation of fiber composite laminates struck by foreign objects traveling at high speed have been reviewd. The review focuses on two major subjects in impact perforation research, i.e., an assessment of perforation characteristics and an understanding of the perforation process and its mechanisms. The target materials include glass, carbon, and aramid fiber-reinforced plastic composites, while the foreign objects consist of steel ball projectiles and cylindrical projectiles with a conical, hemispherical or flat tip. The ballistic limit velocity, residual velocity, and perforation energy obtained from the impact tests and predicted from the analytical and computer models are reviewed first. Then the perforation process and mechanisms are discussed based on the experimental observations and computer simulations. The present article provides state-of-the-art information in the rapidly developing field of impact perforation of fiber composite laminates, by referring mainly to literature published over the past decade.
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  • Yoshitada ISONO, Takeshi TANAKA
    1999 Volume 42 Issue 2 Pages 158-166
    Published: April 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    This paper describes the effect of the material used for a tool on atomic scale indentation and cutting mechanisms of metal workpieces, by means of molecular dynamics simulations. The interatomic force between the tool and workpiece is assumed to be a two-body interatomic potential using parameters based on the ab-initio molecular orbital calculation for a(Cr, Ni)-(C, Si)6H9 atom cluster. Molecular dynamics simulated the atomic scale indentation and cutting process of the chromium and nickel workpieces using the diamond, silicon and diamond-like carbon(DLC) tools. The diamond and DLC tools formed the indentation mark. Young's modulus of the chromium and nickel in indentation simulations was larger than that in experiments. This was qualitatively explained by the effect of the surface energy for the workpiece on the elastic modulus. The machinability of the chromium and nickel with the diamond tool was better than that of the silicon tool in atomic scale cutting simulations. The depth of the cut for the workpieces in nano scale cutting experiments with AFM, was similar to that in atomic scale cutting by molecular dynamics simulations.
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  • Shiro BIWA, Kazunobu OGAKI, Toshinobu SHIBATA
    1999 Volume 42 Issue 2 Pages 167-175
    Published: April 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    Indentation problems for an elastic half-space admit similarity analysis when the local shape of the contacting body can be expressed by a homogeneous function. In this situation, the solution for curved punches can be obtained by the cumulative superposition of the solution to a single auxiliary problem which amounts to indentation by a flat-ended punch. This procedure avoids treating the moving and unknown contact boundary explicitly, so that the contact region can be determined in an accurate manner. In this study, advantages of this procedure are explored from analytical and numerical points of view. Although the theoretical basis is first described for frictionless indentation of an elastic half-space by a rigid punch, the method is subsequently shown to be applicable to the contact between two elastic bodies and for more general frictional behavior. To demonstrate the use of this superposition principle, the three-dimensional indentation by a punch with elliptic cross-section, as well as the plane-strain indentation by an asymmetric punch are solved by this method. Numerical accuracy of the present procedure is verified employing some examples of plane-strain problems, together with its effectiveness in combination with the application of the boundary element analysis for the reduced flat-punch problem.
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  • Toshiaki HATA
    1999 Volume 42 Issue 2 Pages 176-182
    Published: April 15, 1999
    Released: February 18, 2008
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    When an infinite elastic medium with a spherical inclusion is suddenly subjected to a uniform temperature rise, stress waves occur at the interface of spherical inclusion the moment thermal impact is applied. The stress wave in an inclusion proceeds radially inward to the center of the inclusion. The wave may accumulate at the center and cause very large stress magnitudes, even though the initial thermal stress should be relatively small. This phenomenon is called the stress-focusing effect. The stress wave in an infinite medium proceeds radially to infinity. This paper analyzes, in an exact manner, the effects of these waves using the ray integrals. The results give a clear indication of the mechanism of stress-focusing effect in an inclusion embedded in the infinite elastic medium. In the special case, if the elastic compliances of the spherical inclusion tend to be zero, the problem becomes the problem of wave motion in the infinite medium with a spherical cavity.
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  • Seiichi YAMAJI, Hirokazu MATSUDA, Muturou UENO
    1999 Volume 42 Issue 2 Pages 183-190
    Published: April 15, 1999
    Released: February 18, 2008
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    The boundary element method requires only discretization on the boundary but demands a memory capacity equivalent to the square of the total degrees of freedom and a computation time proportional to the cube of the total degrees of freedom. For a large-scale problem, since much time is consumed by communication between the main computer and an external memory device, the elapsed time is much longer than the CPU time. With the aim of reducing the elapsed time, we propose herein a new"diagonal escalation"method, which enables solving of simultaneous linear equations using about 1/4 of the normally required memory capacity. We also explored the possibility of using the present method to optimize the solution to both contact and eigenvalue problems, and cited examples of computations that demonstrate the present method's efficiency.
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  • Tomoshi MIYAMURA, Yutaka TOI
    1999 Volume 42 Issue 2 Pages 191-200
    Published: April 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    Appropriate positions of plastic hinges can be evaluated by using the adaptively shifted integration(ASI) technique in the elastic-plastic analyses of framed structures. In this paper, the ASI technique is applied to the degenerated Timoshenko beam element developed by Dvorkin et al., which is considering the effect of large rotations/displacements. By slightly modifying the shape functions of the Dvorkin's element, the effect of large rotations can be precisely taken into account even when the ASI technique is used. Therefore, precise rigid body rotation about a plastic hinge can be represented by the proposed element. Stresses at the hinge are also evaluated appropriately.
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  • Xian CHEN, Kazuhiro NAKAMURA, Masahiko MORI, Toshiaki HISADA
    1999 Volume 42 Issue 2 Pages 201-208
    Published: April 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    In the analysis of frictional contact problems with large deformation, the use of a convected coordinate system is a natural approach, by which the frame indifference of friction law can be maintained. However, in the case of the finite element method, a problem arises due to the discontinuity of the local coordinates between elements when sliding extends over the element boundary. In this work, a method is proposed to solve this problem, i.e., although the formulation is essentially based on a convected coordinate system, the sliding term is redefined as a spatial vector and is calculated using the reference configuration. Thus, finite sliding due to large deformation can be treated, regardless of the limitations of element coordinate systems. Also, the corresponding consistent tangent stiffness is derived to obtain quadratic convergence. The effectiveness of the proposed method is verified in this study by two numerical examples, including an elastoplastic frictional contact problem with large deformation.
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  • Osamu OKUDA
    1999 Volume 42 Issue 2 Pages 209-215
    Published: April 15, 1999
    Released: February 18, 2008
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    In this paper we describe an algorithm for generating a triangular mesh within an arbitrary planar domain. When is applied the finite element method to numerical simulation, the discretization of the domain becomes on essential part of the procedure. There are many reports on automatic mesh generation methods, such as coordinate transformation, blending function, the Quadtree method, the Delaunay method, and the advancing front method. The main characteristic of the proposed algorithm is that the position of the nodes is generated in the original polygonal region as much as possible in the form of an equilateral triangle and the triangulation of the inner nodes is carried out by the bucket method of computational geometry prior to the global construction of the triangular mesh model. Then the triangulation of the remaining region is carried out utilizing the advancing front method. The processing scheme is developed and applied to several examples. The numerical results are demonstrated and the effectiveness is discussed.
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  • Toshio TERASAKI, Jun CHEN, Tetsuya AKIYAMA, Katsuhiko KISHITAKE
    1999 Volume 42 Issue 2 Pages 216-223
    Published: April 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    A non-destructive method is proposed for estimating residual stress distribution in an object part due to shot peening. The method involves measuring the eigen strain distribution in a small test piece made of the same material and peened under the same shot peening conditions as the object part using the layer removal technique. The residual stress distribution in the part is calculated from this eigen strain. An experiment was carried out to estimate axisymmetric residual stresses in a shot peened cylinder. The results measured directly from the cylinder show good agreement with the results predicted by the proposed method.
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  • Keisuke TANAKA, Yoshiaki AKINIWA, Toshimasa ITO, Kaoru INOUE
    1999 Volume 42 Issue 2 Pages 224-234
    Published: April 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    A new X-ray method is proposed to measure the residual stress in cubic polycrystalline films having the fiber texture with the axis of<111> <100>and<100>perpendicular to the film surface. The elastic constants of textured thin films were calculated on the bases of Reuss and Voigt models. According to the analysis based on Reuss model, the relation between the strain measured by X-ray, ε^-L<33> and sin2 ψ for the equi-biaxial stress is linear for the cases of<111>and<100>fiber textures. For the other cases, the relation is non-linear. A method to determine the stress from non-linear relations is proposed. The analysis based on Voigt model gives the linear relation between ε^-L<33> and sin2 ψ for any case of fiber texture. In thin films made of materials with low anisotroy, the both models give nearly identical relation.
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  • Nobuo NAGASHIMA, Kensuke MIYAHARA, Saburo MATSUOKA
    1999 Volume 42 Issue 2 Pages 235-242
    Published: April 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    The hardness of cementite spheroidized S25C steel was measured, using an AFM ultramicro hardness tester and a special lever that has a three-sided pyramidal diamond indenter with an apical angle of 60°. A clear AFM image of the specimen surface etched in a solution of 3% nitric acid and 97% alcohol enabled us to distinguish small cementite particles with a diameter of less than 1μm. Using AFM imaging, we obtained force-penetration curves for small cementite particles as well as the ferrite portion of S25C steel. The curves show yield behavior. Below the yield force where the penetration depth was less than 30nm, the experimental curve agrees well with the theoretical one. The normalized yield stress, τY/G, is 0.46 for cementite particles and 0.24 for the ferrite portion. These values are nearly equal to those for glass and silicon, and for SNCM439 steel, respectively. It is concluded that the hardness measurement of the materials containing small particles was realized in the nanoscopic region, using the AFM ultramicro hardness tester with a special lever having a three-sided pyramidal diamond indenter with an apical angle of 60°.
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  • Osamu OYAMADA, Kazuo AMANO, Kunio ENOMOTO, Naoto SHIGENAKA, Jun MATSUM ...
    1999 Volume 42 Issue 2 Pages 243-248
    Published: April 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    Shape memory alloys(SMAs) are designed to be used as structural elements at elevated temperatures. The material used in this study was Ni-Ti-Nb SMA with a chemical composition of 51 wt% Ni, 38 wt% Ti, and 11 wt% Nb. The shape-recovery finishing temperature was around 350 K. When the material was heated from room temperature(293 K)to high temperature(561 K), the tensile strength and 0.2%-proof stress slightly decreased, while the elongation and reduction of area increased. Young's modulus increased with the temperature, up to 673 K. The fatigue strength at 561 K in air and in water was slightly higher than at 293 K in air. The fatigue limit in water was close to that in air at 561 K. The fatigue limits at 561K were about 290, 240, and 150 MPa for stress ratios of -1, 0, and 0.5 respectively. Fatigue cracks were found to initiate in the Ti-rich precipitates in the sub-surface, indicating that the fatigue strength is affected by the mean stress. The Ni-Ti-Nb SMA was found to have sufficient mechanical and fatigue strengths to be used as a structural element at elevated temperatures in water.
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  • Gyuhae PARK, Kazuhisa KABEYA, Harley H. CUDNEY, Daniel J. INMAN
    1999 Volume 42 Issue 2 Pages 249-258
    Published: April 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    A new structural health monitoring technique capable of in-service, on-line incipient damage detection has been proposed by the Center for Intelligent Material Systems and Structures, Physical changes in a structure cause changes in the mechanical impedance. Due to the electromechanical coupling in piezoelectric materials, this change causes a change in the electrical impedance of the piezoelectric sensor. Hence, by monitoring the electrical impedance and comparing this to a baseline measurement, we can determine when structural damage has either occurred or is imminent. However, in almost all practical health monitoring applications, the structure being monitored is constantly undergoing change due to the effect of external boundary conditions. One of the important factors that leads to this change is the temperature variations. In this paper, temperature effects on the electrical impedance of piezoelectric materials and the structures have been investigated. A computer algorithm was developed which incorporates temperature compensation into our health monitoring applications. Three experimental investigations were performed successfully under the temperature varying condition, in the range of 25 to 75°C, including a bolted pipe structure, composite reinforced aluminum and precision part such as gears. It was found that, by this compensation procedure, the impedance based health monitoring tehcnique is able to detect damage in the incipient stage, even with the presence of significant temperature variation.
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  • Toshiyuki MESHII, Katsuhiko WATANABE
    1999 Volume 42 Issue 2 Pages 259-264
    Published: April 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    Characteristics of the stress intensity factor of a circumferential crack in a cylinder under radial temperature distribution, which can be regarded as linear, were investigated systematically. The simplified method previously developed by the authors enabled our systematical approach. The investigation was conducted to comprehend the previously reported fact on the stress intensity factor. That is, the stress intensity factor under a given linear temperature distribution tends to decrease monotonously as the crack becomes longer than a specific value. It was shown that this tendency was a fundamental characteristic of the stress intensity factor for the problem and it was concluded that the cause of this was moment redistribution due to the increase in crack length. In addition, it was pointed out that the stress intensity factor of the crack for a specific cylinder length was larger than that for an infinite length.
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  • Hiroshi HATTA, Yasuo KOGO, Hideyuki ASANO, Hiroyuki KAWADA
    1999 Volume 42 Issue 2 Pages 265-271
    Published: April 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    Carbon/Carbon(C/C) composites have attractive mechanical properties such as superior specific strength and high elastic modulus at high temperature exceeding 2000°C in an inert atmosphere. However, mainly due to lack of knowledge of design criteria, C/C composites have not been used in primary heat resistant structures. For example, almost no unified explanation has been given about the fracture behavior of C/C composites. The objective of this paper is to examine the adequacy of the linear elastic fracture mechanics(LEFM) as the fracture criterion of notched C/C composites. Thus the LEFM was tried to be applied to fracture behavior in tensile tests of double-edge-notched and compact tension specimens and in four-point bending tests of single-edge-notched specimens. It was found that the results of three kinds of fracture tests can be consistently and rationally explained in terms of the LEFM concept with the aid of R-curve behavior if the pre-crack length is long enough to be able to neglect the notch tip radius. From fractographic observation it was found that R curve behavior of C/C composites was mainly attributed to the fiber-bridging effect near the notch tip.
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  • Ken KAMINISHI, Makio IINO, Motoharu TANEDA
    1999 Volume 42 Issue 2 Pages 272-279
    Published: April 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    Fatigue tests on solder joints of surface mount type electronic package models were carried out at different temperatures, cycling frequencies and controlled displacement amplitudes in order to examine the crack initiation life Nc, crack extension rate da/dN, crack extension path and crack extension life. The crack initiation life(Nc)cal of solder joints was estimated using maximum equivalent inelastic strain calculated by three-dimensional elasto-inelastic finite element method(3D-FEM). The ratios Nc/(Nc)cal were found 2.4-9.8. Further, 2D-FEM crack extension analyses were performed to examine crack extension behavior. The FEM analyses showed that crack extension path and rate were controlled by maximum opening stress range at crack tip, Δσθmax in plastic zone under rather complicated stress tensor field. Experimentally obtained crack extension rate was found to be related to Δσθmax in FEM analysis as da/dN=β[Δσθmax]α, with α=2.0 and β=2.65×10-10mm5/N2 being determined independently of the test conditions. The calculated values of crack extension life by the FEM analyses using the above equation were in good agreement with the experimental ones.
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  • Kenji HATANAKA, Alief Noor YAHYA, Isamu NONAKA, Hideo UMAKI
    1999 Volume 42 Issue 2 Pages 280-287
    Published: April 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    High temperature creep damage is caused by voids generated at grain boundary at elevated temperatures. Creep void formation is greatly influenced by stress-state as well as metallurgical factors. In this paper, the notched components of 2.25%Cr-1% Mo steel, of which microstructure was prepared to be characteristic of the heat-affected zone in the welded joint by heat treatments, was creep-tested at 630°C. Then the creep void density and total length of creep voids to grain boundary length fraction were measured in the area of 1×1mm2 settled around the notch root in association with the inclined angle of grain boundary against loading axis and the stress state around the root of notch, which was calculated using inelastic finite element method. Consequently, it was found that creep void tended to initiate much more at the grain boundary more perpendicular to loading axis and with the greater normal stress, and seemed to originate and grow almost independent of the shear stress on the grain boundary. The much easier initiation and growth of creep voids at welded joint and/or notch roots are considered to be due to the much higher normal stress to the grain boundary developed under the greater stress triaxiality.
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  • Shuhei OSAKI, Makio IINO, Kazunori KOBAYASHI, Toshimasa SAKAMOTO
    1999 Volume 42 Issue 2 Pages 288-293
    Published: April 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    A series of stress corrosion cracking(SCC) tests were carried out on the peakaged Al-Li-Cu 2090 alloy plates to examine the effect of zinc addition on static- and dynamic-SCC properties. The alloy with 0.7% zinc addition showed an improved static-SCC resistance in the S-L direction. The reference 2090 alloy exposed to aqueous sodium chloride solution exhibited an accelerated dynamic-SCC growth in the T-L direction, relative to exposure to laboratory air, while the alloy with zinc addition revealed a reduced environment-sensitive crack growth. The dynamic-SCC was transgranular, showing a repetitive saw-tooth crack path, which is assumed resulting from localized planar slip associated with{110}<211>texture and inhomogeneous distribution of T1-precipitates. It was found that Zn addition is effective in reducing the slip planarity and preferential dissolution along slip bands.
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  • Li-Tung CHANG, Chih-Han CHANG, Guan-Liang CHANG
    1999 Volume 42 Issue 2 Pages 294-300
    Published: April 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    The chin bar of a motorcycle helmet protects the rider from facial and head injuries. An experimental model was developed to evaluate the behavior of the chin bar on direct facial impact, and compared this model with the Snell Memorial Foundation and British Standard tests. In the model, a headform was secured against the interior of the chin bar, then dropped to impact a flat anvil. The maximum acceleration and Head Injury Criterion(HIC) were measured to assess the impact-absorbing capability of the chin bar. The results showed that this approach provides a more realistic and accurate assessment of the ability of the chin bar to protect against head injuries than the Snell or British Standard systems. A chin bar consisted only of plastic shell and comfort foam offers inadequate protection. An impact-absorbing liner is essential to increase the protective performance of chin bar. An appropriate cushioning structure at impact shell area could further improve the impact-absorbing capability. The stiffness at the connected portion between the chin bar and the helmet should be reduced to enhance the cushioning effect.
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