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Taketoshi NOJIMA, Takayuki KUSAKA
1997 Volume 63 Issue 609 Pages
879-885
Published: May 25, 1997
Released on J-STAGE: February 21, 2008
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Fracture behaviors in mode I delamination tests of CFRP (T 300/2500) were studied at crosshead velocity V=0.005∼200mm/min. In low velocity regions, serrations due to repeated intermittent unstable crack extnsions appear on load P-displacement δ relations, and they become conspicuous as V becomes smaller. The crack resistance force R evaluated using the peak values of the serrated P-δ relation becomes larger with the decrease of V ; the rate dependence of R is negative (dR/dV<0). On the other hand, at velocities higher than the critical one (Vc), there are nothing but fluctuations on P-δ relations. Although the rate dependence of R is extremely small, it is a positive value (dR/dV>0). Relaxation tests were also performed for specimens deformed at lower or higher velocities than V
c ; at high velocity, load P decreases with time, while at low velocity, the load remains constant during the relaxation test. The rate dependence and fracture behaviors have been discussed using a model which takes the crack tip blunting effect into account.
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Hiroshi FUJINO, Syunichi KAWANO, Masahiro FUJII
1997 Volume 63 Issue 609 Pages
886-892
Published: May 25, 1997
Released on J-STAGE: February 21, 2008
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This paper is concerned with the toughness of ABS resin. The generally accepted method for evaluating the toughness of solid polymers with a notch or crack involves use of Izod Impact Test : the evaluation in terms of fracture mechanics is not yet prevalent for polymeric materials in japan. The authors have performed 3-point bending fracture toughness tests on ABS resin, which is a typical rubber toughened polymer alloy, and investigated the dependence of crosshead speed HS and of the duration Tr of constancy of the displacement of the crosshead on the J-integral. The results are as follows : (1) The dependence of both HS and Tr on J
IC should not be neglected. (2) Above all, HS has a large effect on the J
IC at a HS of 200 mm/min is 7.2 times higher than that at a HS of 0.5 mm/min and the relationship is approximately expressed by the following empirical formula : In J
IC=0.341 n HS-0.10, (0.5 mm/min⪈HS⪈200 mm/min : Tr=0) (3) J
IC increases with Tr, but the effect of Tr on J
IC is not as significant as that of HS.
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Kimiyoshi NAITO, Toru FUJII
1997 Volume 63 Issue 609 Pages
893-900
Published: May 25, 1997
Released on J-STAGE: February 21, 2008
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The effects of rubber modification and adhesive thickness on the fatigue-fractured surfaces of epoxy adhesives under mode I cyclic loading were examined using fractals. When the energy release rate range, ΔG
1 is higher than 100 J/m
2, the fractal dimension of fractured surfaces becomes high due to rubber modification under the same ΔG
1. The fractal dimension decreases with increasing fatigue crack growth rate, da/dN. A relationship is given by the following equation between the parameter, S (=da/dN×ΔG
1) and the fractal dimension, D for unmodified and rubber-modified adhesives. log S-log((da)/(dN)·ΔG
1)=α
4·D+β
4 where α
4 and β
4 are experimental constants. Whether the adhesives contain rubber particles or not, the fractal dimension as well as the da/dN-ΔG
1 relation is little affected by adhesive thickness.
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Hiroki HAMANO, Kenichi HIRASHIMA
1997 Volume 63 Issue 609 Pages
901-907
Published: May 25, 1997
Released on J-STAGE: February 21, 2008
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The authors already discussed the crack tip singularities of various kinds of open crack meeting at the interfaces of different isotropic materials for plane problems. Based on these results, this paper is concerned with singularities near the tip of an arbitrary open crack terminating at a bimaterial interface of three anisotropic materials. Using Williams' eigenfunction-expansion method, the crack tip singularities for mode I and mode II are computed. The characteristic determinant is derived using the boundary conditions and interface continuity conditions, and is solved directly using Mullers'method, which computes algebraic equations of high degree. The analytical process and some numerical results are given in figures.
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Toru TAKAHASHI, Kazushi SATO, Toshiyuki HASHIDA, Hideaki TAKAHASHI
1997 Volume 63 Issue 609 Pages
908-913
Published: May 25, 1997
Released on J-STAGE: February 21, 2008
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A method for determining microscopic strength distribution in rocks using an acoustic emission (AE) technique is proposed. The principle of the method is based on a statistical model for fracture analysis of quasi-brittle materials which has been developed by McClintock et al. [Int. J. Fract., 15 2 (1979), 107-118]. The statistical model assumes an inhomogeneous strength distribution of the material which is dictated by the fracture probability with Weibull distribution. Firstly, the principle of the statistical method is verfied by performing numerical simulations using a network model. Secondly, the method is applied to experimental results of uniaxial tension tests and AE measurements conducted on granite and marble. It is demonstrated that the numerical and experimental results support the validity of the proposed method for determining the microscopic strength distribution in rocks.
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Koji SHIMIZU, Masahiro SUETSUGU, Takeshi SENOO, Susumu TAKAHASHI
1997 Volume 63 Issue 609 Pages
914-919
Published: May 25, 1997
Released on J-STAGE: February 21, 2008
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A new technique is proposed for evaluating the optical constants of caustics under dynamic loading. In this technique, the optical constants are determined from the caustic pattern under a concentrated load and the dynamic value of the concentrated load, which is obtained using strain gages bonded to the surface of the falling weight. The optical constants of caustics c
0 for several polymers are accurately evaluated from the caustic pattern formed by a concentrated load acting on a half plane, and the dependence of c
0 on the loading rate is determined. The results show that the value of c
0 decreases considerably with increasing loading rate in Plexiglas and Araldite D containing 30% softening material. On the other hand, the values for polycarbonate. Araldite B and Araldite D not containing softening material decrease slightly with increasing loading rate.
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Mizuho ISHIDA, Norihiro TESHIMA, Susumu TAKAHASHI
1997 Volume 63 Issue 609 Pages
920-924
Published: May 25, 1997
Released on J-STAGE: February 21, 2008
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In the field of fracture mechanics, it is of great importance to obtain the stress intensity factor of a crack when the cracked material is under a load. In this paper, we report the results of a case of a block specimen with a crack under transient heating loads from both sides of the block. We experimentally inventigated the stress intensity factor for a block that is heated abruptly under a certain constant temperature. For the purpose of comparison, both caustic and photoelastic methods are employed and the effects on the stress intensity factor of block dimensions are considered and discussed.
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Youngmin HA, Tsutomu EZUMI, Susumu TAKAHASHI
1997 Volume 63 Issue 609 Pages
925-930
Published: May 25, 1997
Released on J-STAGE: February 21, 2008
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Stress intensity factors are important parameters affecting stress strain behavior in the vicinity of a crack tip. They are used for the strength evaluation of machines, structures, and various machine elements. In fracture problems, stress intensity factors obtained theoretically and experimentally have been effectively utilized in the analytical evaluation of the effect of cracks. The effect of surface crack of a cylindrical and a hollow cylindrical bar and an inclined crack of a hollow cylinder subjected to torsion. In this study, stress intensity factor K
III of mode III which expresses the stress state in the neighborhood of a crack tip is used. Stress analysis was conducted on the inside of a hollow cylinder in the axial direction of a three-dimensional crack tip subjected to torsion by combining the caustic method and the stress freezing method.
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Tadanobu INOUE
1997 Volume 63 Issue 609 Pages
931-938
Published: May 25, 1997
Released on J-STAGE: February 21, 2008
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The stress fields near the apex in bonded dissimilar materials under surface tractions or thermal loading are represented by a linear combination of the singular solutions, the no singularity ones and the particular ones. In this paper, equations for each solution of the stress fields near the apex in bonded two quarter planes under surface traction w
0 and those under a uniform temperature change ΔT are theoretically derived, and the relationship between the solutions under w
0 and those under ΔT is investigated. For each solution, w
0 is expressed as a function involving ΔT and mechanical properties (Young's modulus, Poisson's ratio and thermal expansion coefficient) for the two materials. The thermal stresses caused by ΔT can be replaced by the stresses caused by w
0, and a method to obtain the thermal stresses from the stresses caused by w
0 is presented. In addition, the method is verified by the finite element method (FEM).
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Kiyotaka SAKINO
1997 Volume 63 Issue 609 Pages
939-944
Published: May 25, 1997
Released on J-STAGE: February 21, 2008
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The strain rate sensitivity in FCC metals is known to increase dramatically when the strain rate exceeds about 3×10
3/s. Previous studies indicate that the flow stress above the critical strain rate depends strongly on instantaneous strain rate. It seems that this behavior is caused by a transition in a rate controlling mechanism of dislocation motion. A simplified model for the kinetics of dislocasione is used to consider the transition mechanism. The flow stress calculated using the expression derived from the model shows fairly good agreement with the directly measured flow stress over a wide strain rate range. It is concluded that the steep increase in the strain rate sensitivity of the flow stress is due to the transition in the rate controlling mechanism of the dislocation motion from a thermally activated process to phonon viscosity drag.
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Nobutada OHNO, M.ABDEL KARIM, Mineo KOBAYASHI, Toshihide IGARI
1997 Volume 63 Issue 609 Pages
945-953
Published: May 25, 1997
Released on J-STAGE: February 21, 2008
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This paper is concerned with the strain hardening of 316FR steel subjected to strain-controlled ratchetting deformation, i.e., cyclic straining with maximal strain increasing at every cycle. First. by discussing isothermal and nonisothermal experiments in this type of deformation, it is shown that the isothermal stress versus strain hysteresis loops close almost completely, and that maximal plastic strain is effective for the strain hardening in the ratchetting deformation while cyclic plastic strain has a negligible influence on it. Then, it is shown that the experiments are simulated well using the nonlinear kinematic hardening model proposed by Ohno and Wang if the model is extended by taking account of the isotropic hardening expressed in terms of maximal plastic strain.
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Kenichi OHGUCHI, Katsuhiko SASAKI, Hiromasa ISHIKAWA
1997 Volume 63 Issue 609 Pages
954-961
Published: May 25, 1997
Released on J-STAGE: February 21, 2008
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In this paper, we discuss the viscoplastic deformation and the constitutive model of 60Sn-40Pb solder alloys which is used for the connection of electronic packaging. The constitutive model is developed with the concept that the deformation includes the elastic, plastic, and creep deformation. which is caused from the strain rate effect on the deformation of the solder alloys. Namely, the constitutive model proposed in this paper combines the cyclic plastic model for the time independent part of deformation with the Norton's creep one for the time dependent part. The applicability of the model is verified from the comparison of the simulations based on the model for a series of tests, such as a pure tension and a cyclic loading under several strain rates. As a result, the constitutive model can predict the essential futures of the time dependent deformation of 60Sn-40Pb solder alloys.
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Eiichi TANAKA, Sumio MURAKAMI, Hiroshi ISHIKAWA
1997 Volume 63 Issue 609 Pages
962-967
Published: May 25, 1997
Released on J-STAGE: February 21, 2008
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An inelastic constitutive model of superplasticity taking account of grain and cavity growth is formulated. We first assume that an inelastic strain rate is expressed as the sum of the term related to superplastic deformation mechanism and that related to ordinary deformation mechanism ; each term is represented by a viscoplastic model of the Chaboche type. Then the evolution of drag stress in the superplastic term is formulated by taking account of the effects of grain and cavity growth. Comparison of the predictions with monotonic tension experiments in literature shows that the proposed model can describe the typical deformation behavior of superplasticity such as the dependence of the slope of hardening curve on the strain-rate conditions, the dependence of flow stress on strain-rate history in the presence of static grain growth, and the softening of flow stress due to cavity growth.
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Yan LIU, Sumio MURAKAMI, Masahiro MORITA
1997 Volume 63 Issue 609 Pages
968-975
Published: May 25, 1997
Released on J-STAGE: February 21, 2008
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After examination of the ill-natured stress sensitivity of the conventional creep damage model of Kachanov-Rabotnov, first the intrinsic limitations in the applicability of the damage model to reliable analyses of creep fracture processes are discussed. Then, improvement of the damage evolution equation and the development of a new constitutive equation based on micromechanics are ciscussed to facilitate rational creep fracture analyses and to suppress the mesh-dependence in Finite Element Analysis. Finally, the proposed model is applied to creep crack growth analysis, and the improvement in the mesh dependence of the numerical results is demonstrated.
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Kenichi KOBAYASHI, Haruyuki IMADA, Tamotsu MAJIMA
1997 Volume 63 Issue 609 Pages
976-982
Published: May 25, 1997
Released on J-STAGE: February 21, 2008
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Creep rupture in engineering materials is mainly controlled by the growth of creep voids and cracks. Although many experimental and theoretical studies on creep damage under uniaxial stress state have been performed over the last decade, the effect of multiaxial stress has not been fully examined. Circumferentially notched bars can easily produce a multiaxial stress state around the net section of notch roots. Several creep damage tests have been carried out using this kind of specimen. The surface and longitudinal section near the net section were inspected by means of scanning electron microscopy and optical microscopy. As a result of the measurement of the configuration of creep voids and cracks, it was shown that the maximum length of creep voids can be expressed as a function of the lifetime ratio.
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JangWook HUH, Hideo KOBAYASHI
1997 Volume 63 Issue 609 Pages
983-988
Published: May 25, 1997
Released on J-STAGE: February 21, 2008
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The effect of specimen geometry on the bending strength of β-Si
3N
4/S45C joints with copper interlayer was evaluated by the method of JIS R 1624-1995. The validity of the method was confirmed. Average bending strength of circular-section specimens was higher than that of rectangular-section spceimens. Average bending strength of one-interface specimens was higher than that of two-interface specimens. Crack initiation stress (σ
i) was successfully detected by the acoustic emission (AE) method and found to be approximately 60∼80% of the bending strength. The residual stresses near the interface at the ceramic side were measured before the bending test by the X-ray diffraction method. The bending strength and the crack initiation stress were found to decrease with the increase of residual stresses.
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Hidetoshi NAKAYASU, Satoshi ISONO
1997 Volume 63 Issue 609 Pages
989-996
Published: May 25, 1997
Released on J-STAGE: February 21, 2008
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This study deals with the nonlinear behavior of a limit state function for an evaluation space which is derived from nonnormality and correlation of design variables. An assumption of independence of strength from load cannot be made because the development of an intelligent structure which is able to control the strength depending on the load effect is expected in the future. We suggest that the diagram of FORM accuracy with curves for non-normal and correlated limit state functions is useful in design. Numerical analyses are performed to evaluate the effect of distribution combinations and the statistical dependence of strength on load. From the numerical analyses, it is found that the nonlinearity of the limit state function for the standardized space is strongly dependent on the measure of safety of structural systems and the accuracy of the prediction of failure probability. These nonlinearities arise from the non-normality of the distribution in which the curves of the limit state function are extremely different from those of a linear model.
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Peihon HOU, Akiyoshi CHATANI, Akihiro HOJO, Hiroshi TACHIYA
1997 Volume 63 Issue 609 Pages
997-1001
Published: May 25, 1997
Released on J-STAGE: February 21, 2008
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A method for the determination of dynamic stress-strain relation of materials by means of instrumented Charpy impact testing technique was proposed and its validity was shown by some measured examples. The dynamic strengths of steels (S55C, SCM3, SUJ2, SK3) hardened from HV340 to HV850 by heat treatment were obtained from stress-strain relations measured by the present method. As a result, it was found that the yield strength of hard steels increases roughly linearly with increasing hardness and that under dynamic loading was 20∼30% higher than that under static one. Those strengths are also found to become maximum in the vicinity of HV700.
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Kinya ITOH, Hideto SUZUKI
1997 Volume 63 Issue 609 Pages
1002-1007
Published: May 25, 1997
Released on J-STAGE: February 21, 2008
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The present paper is concerned with the torsion problem of composite annular plate the inclusion of which has an equivalent elastic constant. In particular, this paper is concerned with an annular thick plate sustaining a twisting moment along the outer portion. By employing Reissner's thick plate theory, expressions for stresses and displacements near the boundary of the composite annular plate are obtained and appropriate continuity conditions are satisfied at the boundary of that region. Numerical results of a specific example illustrate the marked improvement of the present treatment.
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Kinya ITOH, Hideto SUZUKI
1997 Volume 63 Issue 609 Pages
1008-1014
Published: May 25, 1997
Released on J-STAGE: February 21, 2008
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In this paper, the problem of annular thick plates sustaining an axisymmetric load is treated using Reissner's theory of plates. The general solutions obtained here contain the corresponding solutions for the case of classical theory predictions in limiting case of above general solutions. In order to determine the significance of effect of the transverse normal stress in addition to the effect of shear deformation, the maximum stresses and deflections for the case of simply supported annular thick plates are numerically obtained and compared with the results of classical plate theory. The numerical results are summarized as technological data. Comparison of corrective value for shearing stress and lateral load with the known exact solution indicates the sufficient accuracy for practical use.
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Kinya ITOH, Hideto SUZUKI
1997 Volume 63 Issue 609 Pages
1015-1021
Published: May 25, 1997
Released on J-STAGE: February 21, 2008
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This study is concerned with the axisymmetric bending of uniform, isotropic, elastic thick plates. In particular, we analyze an annular thick plates a portion of which is clamped between two smooth rigid plane surfaces. Using Reissner's theory of plates, expressions for the stresses in the region constrained within the clamp are obtained and appropriate continuity conditions are satisfied at the edge of that region. The numerical results for the case of axisymmetric bending of an annular thick plate taking into consideration the clamped edge condition are summarized as technological data.
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Masahiro FUNABASHI
1997 Volume 63 Issue 609 Pages
1022-1027
Published: May 25, 1997
Released on J-STAGE: February 21, 2008
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New gradient polymer composites were fabricated from epoxy resin filled with metal particles by applying the centrifugal force. Density and electrical conductivity measurements were carried out on samples filled with nickel particles, copper particles and a mixture of both metals. Centrifugal force was applied to samples by a centrifuge machine. Volume distributions of particles were derived from density measurement of samples. The centrifugal force produced the gradient particle distributions in the samples. Particle size markedly affected particle distributions. The electrical conductivity of samples varied in the direction of centrifugal force applied to samples. An additivity law for the volume contents of particles was established for samples filled with particles of different sizes.
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Yoshio AOKI, Yusuke FUKUSHIMA, Goichi(O-IL BEN
1997 Volume 63 Issue 609 Pages
1028-1035
Published: May 25, 1997
Released on J-STAGE: February 21, 2008
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In order to maximize the buckling load of FRP-laminated orthotropic-ply cylindrical shells, the optimization of stacking sequence in these shells is studied by use of evolutionary algorithms. Genetic algorithm parameters, for example the population size, the probability of mutation and the probability of crossover are tuned by numerical calculations and evolutionary algorithms, which means that the genetic algorithm taking account of the local search for an optimum is proposed. The advantage of this approach over conventional nonlinear programming is discussed. Some examples of optimal stacking sequences for FRP-laminated cylindrical shells under axial compression and/or external pressure are presented. As a result, it is shown that different optimal stacking sequences of the FRP-laminated cylindrical shells give the almost same buckling load.
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Shohei KAWAKUBO, Kenichi HIRASHIMA
1997 Volume 63 Issue 609 Pages
1036-1042
Published: May 25, 1997
Released on J-STAGE: February 21, 2008
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The effect of reinforcement in elastic materials is quite interest to engineers in designing structures. Existence of craze zone around the crack within medium such as polymers cannot also be neglected in the mechanism of fracture. Although the stress and displacement are able to obtain analytically following the muskhelishvili loading method, general expression in each mode and its numerical results have not been obtained because of dificulty about a geometry of ellipse. This paper presents general analytical solutions for both in-plane and out-of-plane loads.
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Yoshihiro OCHIAI
1997 Volume 63 Issue 609 Pages
1043-1049
Published: May 25, 1997
Released on J-STAGE: February 21, 2008
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Linear stress analysis without initial strain can be easily carried out using the boundary element method. However, in general, domain integrals are necessary to solve the linear stress problem with initial strain. This paper shows that the two-dimensional linear stress problem with initial strain can be solved without the need for a domain integral. In this paper, the distribution of initial strain is interpolated using a boundary integral equation. A new computer program is developed and applied to simple problems.
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Hideo CHO, Singo OGAWA, Kazushi YAMANAKA, Mikio TAKEMOTO
1997 Volume 63 Issue 609 Pages
1050-1056
Published: May 25, 1997
Released on J-STAGE: February 21, 2008
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Elastic properties of TiN films deposited on stainless steel SUS317J2 by three physical vapor deposition methods were estimated from the velocity dispersion of laser surface acoustic waves in the frequency range of 30 to 60 MHz. The velocity dispersion of Rayleigh waves was obtained by the Scanning Interference Fringes (SIF) and used to estimate the elastic stiffness of the films. Young's modulf of TIN films were found to increase in the order of activation reaction (ARE) method → hollow cathode discharge (HCD) → arc ion discharge (AID) method. The attenuation of Rayleigh waves was the highest for AID film due to the poor quality of the film.
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Singo OGAWA, Hideo CHO, Kazushi YAMANAKA, Mikio TAKEMOTO
1997 Volume 63 Issue 609 Pages
1057-1062
Published: May 25, 1997
Released on J-STAGE: February 21, 2008
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Damage progression of vapor deposited TiN films on SUS317J2 steel under compressive loading was estimated by continuous monitoring of acoustic emission (AE). AE source inversion revealed that the film fracture progresses during sequence of (1) Mode-II exfoliation at the edge of TiN film in the elastic strain, (2) Mode I exfoliation of TiN by an emergence of slip step in the plastic region, and (3) Mode-1 film fracture which allows the penetration of corrodent. The threshold strain that causes film damage was correlated with the mismatch of elastic modulus of TiN film to that of the steel substrate.
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Toshiharu NOMOTO, Toshio TERASAKI, Kazunobu MAEDA
1997 Volume 63 Issue 609 Pages
1063-1068
Published: May 25, 1997
Released on J-STAGE: February 21, 2008
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This paper deals with a buckling deformation caused by welding. The welding buckling is affected by welding conditions and sizes of plate. The parameter due to the moving heat source and that due to the residual stress were proposed for arranging the welding buckling. The experiments for making clear the parameter were done under changing welding conditions and plate sizes. The theory for calculating the welding buckling was derived and used for investigating the true parameter. It is clear from the experiment that the welding buckling is caused by the residual stress. The new parameter for arranging the welding buckling is proposed and is proved by the experiment.
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QingQing NI, Katsuhisa BABA
1997 Volume 63 Issue 609 Pages
1069-1075
Published: May 25, 1997
Released on J-STAGE: February 21, 2008
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A double cleavage drilled compression (DCDC) specimen has been analyzed using the boundary element method (BEM). At the same time, it was used as a CFRP model composite in order to examine the crack propagating behavior and interfacial fracture energy at the fiber/matrix interface. As a result, it was confirmed that the DCDC specimen with a symmetrical hole has a mode I stress distribution. It was shown that the DCDC test is a useful method for evaluating the interfacial behavior of fiber-reinforced plastic materials. However, both experimental and analytical approaches are needed to achieve a quantitative evaluation of the fiber/matrix interface.
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Michiya KISHIDA, Kazuaki SASAKI, Yutaka EKIDA
1997 Volume 63 Issue 609 Pages
1076-1082
Published: May 25, 1997
Released on J-STAGE: February 21, 2008
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In this paper, we propose a finite element model of an edge dislocation. The basic concept of the present model is based on the well-known mathematical dislocation model. That is, when two planes dislocated by b are joined to each other, the stress field obtained as a result of this procedure is equivalent to the one caused by dislocation with Burger's vector b. In the case of vector b being perpendicular to the planes, we can obtain the solution of edge dislocation. Some stress fields near the dislocation are calculated by FEM, and compared with the analytical results. From the results, it is shown that the present modeling of edge dislocation is satisfactory enough to analyze the problem caused by dislocation.
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Toshimichi FUKUOKA, Tomohiro TAKAKI
1997 Volume 63 Issue 609 Pages
1083-1088
Published: May 25, 1997
Released on J-STAGE: February 21, 2008
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In the tightening process of a bolted joint using torque control, the effect of friction on axial force and torque is an issue of great interest. In this study, the mechanical behaviors of a bolted joint during tightening, such as variations of axial force and torque, are investigated both experimentally and numerically. Hence, friction coefficients on pressure flank of screw thread and the nut bearing surface are estimated by measuring the total torque, axial force and torque applied to the bolt, and compared with variations of axial force and torque. The validity of the finite element approach proposed here for evaluating changes in torque and axial force is ascertained by comparing the numerical results to the experimental ones. It is shown that the size of grip length has some influence on the reduction of torque and axial force.
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Masaaki OTSU, Kenichiro MORI, Kozo OSAKADA
1997 Volume 63 Issue 609 Pages
1089-1095
Published: May 25, 1997
Released on J-STAGE: February 21, 2008
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Working conditions in mushy-state plane-strain upsetting of rectangular magnets contained in steel capsules with concave or convex dies are determined by numerical simulation using the distinct element method. The motion of the grains in the mushy state rare-earth magnet is calculated by the distinct element method and the plastic deformation of the capsule containing the magnet is calculated by the viscoplastic finite element method. In addition, a model experiment using acrylic resin grains, a Vaseline liquid phase and a plasticine capsule is carried out. The aspect ratio of the magnet, the volume ratio of the capsule and the die angle are chosen as the working conditions, and the degree of grain alignment and the crop loss for formed magnets are evaluated. Although the effect of the aspect ratio of the magnet is large, those of the volume ratio of the capsule and the die angle are comparatively small.
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Motoki NAKANE, Hiroyuki FUJINUMA, Kazuyuki SHIZAWA, Kunihiro TAKAHASHI
1997 Volume 63 Issue 609 Pages
1096-1103
Published: May 25, 1997
Released on J-STAGE: February 21, 2008
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In the previous papers, the authors proposed the concept of the mesodomain which connects microscopic kinematic quantities and macroscopic mechanical ones using an assumption of constrained gradient. However, stress and higher-order stresses obtained from the discussions are not defined as area averages but only as volume averages. In the present paper, mechanical balance equations in the mesodomains are derived based on the conservation law of an atom without the above assumption. Solids are modeled as spring-particle systems in the mesodomains. The averaged values of microscopic quantities over the domain are associated with the center of mass, and macroscopic mechanical balance equations are obtained using these averaged values. Since this model can be regarded as micromorphic continua, we can express Cauchy stress, volume-averaged stress and higher-order stress with microscopic quantities.
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Motoki NAKANE, Hiroyuki FUJINUMA, Kazuyuki SHIZAWA, Kunihiro TAKAHASHI
1997 Volume 63 Issue 609 Pages
1104-1111
Published: May 25, 1997
Released on J-STAGE: February 21, 2008
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In order to model a solid as an assembly of atoms, the mesodomain concept is effective to relate microscopic quantities of atoms with macroscopic quantities of solids. In previous papers, mechanical balance equations were derived on the basis of the equations of motion of atoms without the assumption of a constrained gradient. In the present paper, microscopic expressions of heat flux and internal energy are discussed, expressing the balance of energy with microscopic quantities in the mesodomains. The energy equation is formulated using averaged values of microscopic quantities over the domain by dividing the velocity of an atom into macroscopic motion and thermal motions. Heat flux is defined as an area-averaged value of thermal motions of atoms. Internal energy is described as the sum of the kinematic and potential energies of atoms in the mesodomain. Moreover, it is indicated from the microscopic expressions that the higher-order couple stress power and the moment of inertia are equivalent to the heat flux and the internal energy, respectively.
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Tetsuro OGI, Takashi MANDAI, Yasuhiro YABE
1997 Volume 63 Issue 609 Pages
1112-1118
Published: May 25, 1997
Released on J-STAGE: February 21, 2008
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Ultrasonic waveforms reflected by various kinds of defects were calculated by numerical analysis based on elastic wave theory. By using these calculated results as a knowledge base, the development of a nondestructive evaluation system which provides quantitative information, such as types, locations, sizes and shapes of the defects, is expected. In this study, a fuzzy reasoning method based on principal component analysis was proposed and a prototype system was developed. This method can be used to characterize waveforms using the principal components and to interpolate the wave data using the membership functions in the fuzzy rules. In addition, by adjusting the membership functions, the error which depends on the difference between the numerical analysis and the experiment can be absorbed. This method was applied to crack depth evaluation for perpendicular and inclined cracks. In each case, both the numerical analysis data and the experimental data were evaluated with high accuracy.
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Minoru MURAYAMA, Tetsuo SHOJI, Yutaka WATANABE, Yasumoto SATO
1997 Volume 63 Issue 609 Pages
1119-1125
Published: May 25, 1997
Released on J-STAGE: February 21, 2008
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Quantitative evaluation of fatigue damage accumulation and resultant crack initiation and propagation is one of the greatest concerns for plant life time management and license renewal in various industries. To develop a novel nondestructive evaluation method for fatigue damage evaluation, we applied Induced Current Focusing Potential Drop (ICFPD), which was developed for an inspection of defects, to processes of fatigue damage accumulation, small crack initiation and coalescence, and macroscopic crack growth. Measurements were performed on specimens fatigued under an axial strain controlled tension/compression load with various degrees of fatigue damage defined as a cycle ratio, N/Nc where Nc is a cycle giving a maximum crack size of 3 mm at surface. ICFPD can be used to clearly detect and differentiate all of these fatigue processes of damage accumalution without crack initiation and subsequent small crack initiation and macroscopic crack propagation.
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