Transactions of the Japan Society of Mechanical Engineers Series A
Online ISSN : 1884-8338
Print ISSN : 0387-5008
Volume 61, Issue 581
Displaying 1-31 of 31 articles from this issue
  • Kenji Machida, Masanori Kikuchi, Yasuaki Matsushima
    1995 Volume 61 Issue 581 Pages 1-6
    Published: January 25, 1995
    Released on J-STAGE: February 21, 2008
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    Two- and three-dimensional finite-element analyses have been conducted on a compact normal and shear specimen under mixed-mode loading. This paper presents a comparison among stress-intensity factors and J-integrals for mixed-mode problems obtained through three different approaches : the displacement method, J-integral formulation and modified crack-closure integral. The accuracy of these methods is discussed. The mixed-mode J-integral and modified crack-closure integral estimate the J-integral components for an arbitrarily mixed-mode three-dimensional crack well. The accuracy of the displacement method is discussed with respect to plane strain and stress conditions.
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  • Masanori Kikuchi, Kenji Machida, Tomokazu Togo
    1995 Volume 61 Issue 581 Pages 7-12
    Published: January 25, 1995
    Released on J-STAGE: February 21, 2008
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    The constraint effect on fracture toughness is studied. Fracture toughness tests are conducted using CT and three-point-bend specimen. Their initial crack lengths are changed from a/W=0.1 to 0.6 in five cases, which means that the constraint at the crack tip changes. It is shown that a larger fracture toughness value is obtained by a short crack specimen than by the long crack one. Two-dimensional finite-element analyses are carried out. The crack tip stress fields are compared with HRR solutions, and it is shown that the crack-tip field deviates from the HRR solution as the crack length decreases. The Q factor is evaluated for these specimens, and the relation between JIC and Q is obtained. The conventional J-integral is compared with that obtained by the contour integral, and the experimental results are corrected. The results show the effect of crack tip constraint on the fracture toughness value clearly. The same problems are also analyzed using Gurson's constitutive equation taking into consideration the void behaviors. The effect of the constraint on void nucleation and growth is studied.
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  • Naobumi Sumi
    1995 Volume 61 Issue 581 Pages 13-19
    Published: January 25, 1995
    Released on J-STAGE: February 21, 2008
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    A solution is presented for the stress-wave response of a partially transparent finite elastic circular plate with a penny-shaped crack subjected to electromagnetic radiation. The radiation is assumed to occur at a constant rate for the duration of the pulse and to be deposited with a radial Gaussian distribution and to diminish exponentially with distance from the surface of the plate. The development is based on the equations of uncoupled dynamic thermoelasticity with heat conduction neglected. The numerical procedure employs the explicit finite-difference approximations with second-order accuracy based on the integration of the governing equations along the bicharacteristics. Numerical calculations are carried out for the dynamic behavior of the thermal stresses and the stress intensity factors, and the results are shown in figures.
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  • Koji Fujimoto, Yasuhide Hashimoto
    1995 Volume 61 Issue 581 Pages 20-27
    Published: January 25, 1995
    Released on J-STAGE: February 21, 2008
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    A crack problem near a circular inclusion is analyzed numerically. The method of continuously distributed dislocations model is applied to the present problem, and the boundary condition on the crack surface is reduced to a set of singular integral equations of the Cauchy type in which the dislocation density functions are unknown. The obtained singular integral equations are solved numerically and the stress intensity factors are obtained with changing the configuration parameters of the crack and/or the elastic moduli of the matrix and the circular inclusion. The normal stress and the shearing stress acting on the bimaterial interface are also calculated quantitatively. The numerical results are reliable and accurate enough to be used for the confirmation of the reliability and the accuracy of another analysis method. As a result of these calculations, it has been clarified that when the rigidity of the inclusion is high, the stress level on the interface becomes large in spite of the fact that the stress intensity factors of the crack become small.
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  • Ken-Ichi Takao, Kazuhiro Kusukawa
    1995 Volume 61 Issue 581 Pages 28-32
    Published: January 25, 1995
    Released on J-STAGE: February 21, 2008
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    Low-cycle fatigue tests have been carried out on an annealed commercially pure titanium under strain-controlled conditions with constant strain range. The initiation of fatigue cracks was observed successively with the aid of an optical microscope using the replication technique and microstructural deformations were measured. Results show that fatigue crack initiation was predominantly intergranular ; however, slip band cracks often appeared also in the low strain range. At the specified grain boundaries, irreversible steps attributed to a few slip systems formed under each strain cycle. The accumulation of irreversible steps due to strain cycling is thought to cause intergranular cracking.
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  • Kazuaki Shiozawa, Seiichi Nishino, Takeru Fujii, Kennichi Saito, Hisaf ...
    1995 Volume 61 Issue 581 Pages 33-38
    Published: January 25, 1995
    Released on J-STAGE: February 21, 2008
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    Low-cycle fatigue behavior of Cr-Mo-V steel used in a long-term under the biaxial strain condition at an elevated temperature was studied in this paper. A push-pull test, reversed torsion test and combined push-pull and reversed torsion test in Cr-Mo-V steel were performed at 823 K in air. The specimen was sampled from the high-temperature portion and coupling portion of 91 600 h experienced and 131 times start/stop operated turbine rotor. From this investigation, the following conclusions were obtained. (1) Low-cycle fatigue life of the high-temperature portion decreased in comparison with the coupling portion, particularly under the reversed torsion condition. (2) Cyclic yield stress obtained from the cyclic stress-strain curve decreased due to long-term use. (3) Crack propagation direction depends on the principal strain ratio and flaws in oxide film, and it was not affected by long-term use. (4) Flaw density of oxide film of the high-temperature portion was higher than that of the coupling portion. (5) Decrease in low cycle fatigue life of long-term-used Cr-Mo-V steel is explained by the decrease in cyclic yield stress and the increase in flaw density in oxide film.
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  • Etsuo Takeuchi, Saburo Matsuoka, Kensuke Miyahara, Hisashi Hirukawa, N ...
    1995 Volume 61 Issue 581 Pages 39-44
    Published: January 25, 1995
    Released on J-STAGE: February 21, 2008
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    The arrest function in fatigue crack propagation at 25∼550°C in air was investigated, using SUS 304 (18 Cr-8 Ni) and SUS 403 (12 Cr) stainless steels containing 0.2 weight percent dispersed lead particles. The Pmax-constant ΔK-decreasing test, where the minimum load, Pmin, increased with increasing crack length while the maximum load, Pmax, remained constant, was employed in order to avoid crack closure. The main conclusions obtained are as follows : (1) Fatigue crack propagation properties including the threshold were independent of the material at room temperature under the closure-free condition. Fatigue threshold values at temperatures higher than the load melting point of 327°C were about 40% higher for lead-particle-dispersed steels than for host steels. (2) The increase in threshold level at elevated temperatures was explained, considering that the oxide layer spalled at the fatigue crack tip was repaired by the molten lead. Accordingly, we concluded that dispersed lead particles could show the arrest function of the fatigue crack propagation at elevated temperatures.
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  • Mamtimin Geni, Masanori Kikuchi, Kazumi Hirano
    1995 Volume 61 Issue 581 Pages 45-51
    Published: January 25, 1995
    Released on J-STAGE: February 21, 2008
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    The fracture process of a whisker-reinforced aluminum alloy is simulated by the finite-element analysis using Gurson's model as a constitutive equation. The results show that the dimple fracture process after a large amount of plastic deformation is well simulated. It is found that the local nonuniform distribution of whisker fiber has a large effect on the quantitative evaluation. Its effect is studied by changing the whisker location and whisker fiber volume fraction on nonuniform models. The constraint effect and the effect of the debonding between the matrix and the whisker fiber are also considered.
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  • Dai-Heng Chen
    1995 Volume 61 Issue 581 Pages 52-58
    Published: January 25, 1995
    Released on J-STAGE: February 21, 2008
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    In this paper, the characteristics of the stress fields for a crack normal to and terminating at a bimaterial interface of isotropic and anisotropic half-planes are studied as a plane problem. The eigenequation, by which the order of stress singularity is determined, is given in an explicit form. It is found that the order of singularity is dependent not only on the elastic constants of the materials, but also on the deformation mode. An explicit closed-form expression is presented for the stress and displacement distribution near the crack tip.
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  • Dai-Heng Chen
    1995 Volume 61 Issue 581 Pages 59-64
    Published: January 25, 1995
    Released on J-STAGE: February 21, 2008
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    The plane elasticity problem of a point force and a dislocation acting at a point inside an elliptic inclusion in an infinite plate was solved by Warren in 1983. However, in this study, it is found that the solution by Warren does not converge for the case in which the point of action of the point force and dislocation is near to the interface. The solution applicable for all cases, including the case where the point force and dislocation are applied at a point on the interface, is obtained in this paper in the form of functions plus an infinite series. By carefully defining the functions, the infinite series attains an acceptable convergence.
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  • Tadanobu Inoue, Hideo Koguchi, Toshio Yada
    1995 Volume 61 Issue 581 Pages 65-72
    Published: January 25, 1995
    Released on J-STAGE: February 21, 2008
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    The stress fields near the apex in dissimilar materials composed of three isotropic homogeneous wedges with arbitrary angles subjected to surface tractions or thermal load are expressed by a linear combination of the singular solutions, no singularity ones and the particular ones. For the cases where the stresses near the apex of dissimilar materials subjected to thermal load represent the singularities of type γp-1, type log γ and no singularity, the stress distributions are examined theoretically and numerically. Moreover, the different influences of solutions with no singularity and the particular solutions on the stresses near the apex are theoretically clarified. It was examined how the characteristic of stress singularity clarified using FEM is changed by whether no singularity solutions and the particular solutions are taken into consideration in analyzing the stress singularity. Furthermore, the notable results on the stress singularity of type log γ in dissimilar materials formed from two rectangular wedges are shown.
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  • Tadanobu Inoue, Hideo Koguchi, Toshio Yada
    1995 Volume 61 Issue 581 Pages 73-79
    Published: January 25, 1995
    Released on J-STAGE: February 21, 2008
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    The characteristic of a singularity of the stress field near the apex in a bonded structure under surface traction has been theoretically clarified by Bogy and has so far been studied in detail by many investigators. The singularity of thermal stresses near the apex in a bonded structure under thermal load has been numerically examined, although it has not yet been examined theoretically. In this paper, the equations for thermal stresses near the apex in a three-phase bonded structure formed from three isotropic homogeneous wedges with arbitrary angles are deduced through thermoelastic theory. Moreover, a relevant parameter for thermal stresses in dissimilar materials is newly introduced. Then, the relationship between thermal stresses and elastic constants is shown, and the relationship between those stresses and coefficients of thermal expansion is studied in detail.
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  • Koh-Ichi Sugimoto, Mitsuyuki Kobayashi, Hidehiro Matsushima, Shun-ichi ...
    1995 Volume 61 Issue 581 Pages 80-86
    Published: January 25, 1995
    Released on J-STAGE: February 21, 2008
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    The effects of strain-induced transformation (SIT) on X-ray residual stress of retained austenite islands in TRIP-aided dual-phase steels were examined under uniaxial tension, and were discussed using a micromechanics theory. If the retained austenite particles are stable against the SIT and strain hardening, high tensile residual stress of 100 to 200 MPa occurs in the particles. The stress corresponds to that estimated from the micromechanics theory. In such a case, the retained austenite particles effectively increase the internal stress of the ferrite matrix similar to bainite and martensite particles. When the retained austenite particles easily transform to martensite during straining, the residual stress is decreased by plastic relaxation resulting from expansion and shear strains on transformation, although the strain-induced martensite increases the flow stress of the steels.
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  • Yoshiyasu Itoh, Masahiro Saitoh, Matsuo Miyazaki
    1995 Volume 61 Issue 581 Pages 87-92
    Published: January 25, 1995
    Released on J-STAGE: February 21, 2008
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    A low-pressure plasma spray coating process has been applied in gas turbines for use in hot parts (turbine blades, duct segments, etc. ) which are exposed to aggressive gases at elevated temperatures. Overlay coatings based on MCrAlY alloy system (M is Ni, Co or Fe) are employed commonly as oxidation-and corrosion-resistant coatings. In this paper, the microstructures and the residual stresses of five kinds of MCrAlY coatings sprayed by low-pressure plasma spray system and heat-treated at 1393 K for 2 h in Ar atmosphere were investigated by the X-ray diffraction method. It was found that the MCrAlY coatings were composed of the Ni-or Co-based solid solution and the precipitated Al intermetallic composite. Thermal and mechanical properties were also measured for investigating the characteristics of residual stress. It was confirmed by the X-ray diffraction that the residual stresses of some kinds of sprayed coatings could not be measured with high accuracy for the strongly layered structure. A convenient calculation technique for the determination of residual stress was investigated using an inherent strain model.
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  • Yoshihiro Ochiai
    1995 Volume 61 Issue 581 Pages 93-98
    Published: January 25, 1995
    Released on J-STAGE: February 21, 2008
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    Linear stress analysis without initial strain can be easily solved by 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 linear stress problem with initial strain can be approximated without the need for a domain integral. In order to solve the linear stress problem with complicated initial strain, contour lines of initial strain are used to divide the domain into small areas, where the distributions of initial strain are assumed to approximately satisfy the Laplace equation. A new computer program is developed and applied to some problems.
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  • Toshio Jingu
    1995 Volume 61 Issue 581 Pages 99-105
    Published: January 25, 1995
    Released on J-STAGE: February 21, 2008
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    This paper describes the transient response of a robotic arm which rebounds from a wall or is interrupted by the wall, after the free end of the arm comprising a beam attached to a hub gyrating about an axis, strikes the surface of a rigid wall. Two integro-differential equations are produced to use Hamilton's principle, providing the variational method upon which the finite-element weak form is built. The flexure energy of the beam is derived by using the Bernoulli-Euler beam theory. The kinetic energy caused by the moment of inertia of the hub is also taken into account. The finite-element method is used to discretize the equations of motion. The results of simulation are compared to time histories of bending strain measured by a strain gage. The variations of bending strain consist of the basic frequency mode and other frequency modes. The time histories of the simulated bending strain is in agreement with that from experiment, except in high-frequency modes.
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  • Nao-Aki Noda, Tadatoshi Matsuo, Hideo Ishii
    1995 Volume 61 Issue 581 Pages 106-113
    Published: January 25, 1995
    Released on J-STAGE: February 21, 2008
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    This paper deals with a row of equally spaced equal elliptical inclusions in a plate subjected to transverse and longitudinal tensions. Based on the concepts of the body force method, the problems are formulated as a system of singular integral equations with Cauchy-type or logarithmic-type singularities, where the densities of body forces distributed in an infinite plate having the same elastic constants of the matrix and inclusions are unknown functions. In order to satisfy the boundary conditions along the inclusions, eight kinds of fundamental density function proposed in our previous paper are used ; then the body force densities are approximated by a linear combination of the fundamental density functions and polynomials. In the analysis, elastic constants of matrix and inclusion are varied systematically ; then, the magnitude and position of the maximum stress are examined. For any fixed shape, size and elastic constant of inclusions, the maximum stress is shown to be linear with the reciprocal of the number of inclusions.
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  • Jin'ichiro Gotoh, Motohiro Kawai, Akihiro Misawa, Masahisa Takashi, Sh ...
    1995 Volume 61 Issue 581 Pages 114-119
    Published: January 25, 1995
    Released on J-STAGE: February 21, 2008
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    Wavy patterns of stress and temperature distribution are occasionally observed along the circumference of a rotating viscoelastic disk under a contact load. This phenomenon is caused by a combination of physical and mechanical features such as dynamic behavior, heat generation due to loss energy, heat conduction and various modes of vibrations in the viscoelastic disk including the loading system. This study attempts to give a rational explanation of the phenomenon, through experimental and theoretical approaches, by means of dynamic modeling of the entire vibrating system. The study by means of dynamic analysis revealed that the wavy stress pattern results from the resonant vibration of the loading mechanism which corresponded to its natural frequency. It is emphasized that the peculiar vibration is strongly influenced by temperature-dependent dynamic properties of the viscoelastic disk.
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  • Yoshihiro Tomita, Shigeyuki Tanaka
    1995 Volume 61 Issue 581 Pages 120-126
    Published: January 25, 1995
    Released on J-STAGE: February 21, 2008
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    The relation between the non-Gaussian molecular chain network structure and entanglement of chains and a simple evolution equation of the number of entanglement of chains during the deformation process are developed to cover a wide class of deformation processes of polymeric materials which manifest remarkable anisotropy according to the orientation of molecular chains. With the generalized Argon double-kink model of the intermolecular resistance, a three-dimensional constitutive equation is developed and the validity of the proposed constitutive equation has been examined through the comparison between the predicted results and experimentally obtained results. Application of the proposed constitutive equation to the prediction of deformation behavior of tension of polymeric materials is discussed.
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  • Hideo Morita, Hiroyuki Matsumoto
    1995 Volume 61 Issue 581 Pages 127-132
    Published: January 25, 1995
    Released on J-STAGE: February 21, 2008
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    The subperforation flatwise impact damage resistance on some types of carbon fiber/resin laminated composite systems under falling weight impact test was evaluated. Two graphite/epoxy systems (T300/#2500 and T800H/#3900-2) and two graphite/PEEK systems (APC-2/AS4 and APC-2+PEEK film interleaves) were tested. The stacking sequence of each system was (0/30)s, (0/60)s and (0/90)s. Specimens were impacted by an instrumented falling weight impactor. The damage area was measured with ultrasonic C-Scan. In all specimens, the relationship between damaged area (DA) and impact energy (IE) was linear. Therefore, the impact damage resistance capability of composite systems could be compared using the damaged area to impact energy ratio (DA/IE). Among the tested resin systems, the relative ranking of the DA/IE was T300/#2500>APC-2/AS4>T800H/#3900-2>APC-2+PEEK film. Lower difference in the fiber angle of laminates presented lower DA/IE.
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  • Hiroshi Suzuki, Hideki Sekine, Katsuhiro Yamada
    1995 Volume 61 Issue 581 Pages 133-138
    Published: January 25, 1995
    Released on J-STAGE: February 21, 2008
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    The tensile strength of injection-molded short glass fiber reinforced themoplastics which have been pigmented with a slight amount of titanium dioxide (TiO2) decreases. In this paper, on the basis of micromechanics, the strength deterioration of the unnotched composite and the load-displacement relation of the notched one were predicted. Damage developed in the composite was modeled as a fictitious crack with cohesive stress acting on the crack surface. The relationship between the cohesive stress and crack opening displacement, i. e., the tension-softening relation, was theoretically determined. The tensile strength of the unnotched composite was estimated using the maximum stress from the tension-softening relation. Characterizing the mechanical behavior of the damage developed at the notch tip as the tension-softening relation, the load-displacement curve was obtained. The predicted tensile strength and load-displacement curve were compared with experimental ones and good agreements were found between the predicted and experimental results.
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  • Ikuhiko Hayashi, Eisuke Seta, Shuuichi Ueda, Tadao Ichikawa
    1995 Volume 61 Issue 581 Pages 139-145
    Published: January 25, 1995
    Released on J-STAGE: February 21, 2008
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    Woven GFRP laminates composed of epoxy resin were used as specimens to investigate the effect of textile structure on growth of interlaminar delamination under repeated mixed-mode loading. Different shapes of specimens were prepared with mode ratios (GI/GII)=3.76, 1.33 and 0.500, and the reinforced fibers were of two different textures ; one was standard texture (ST), the other was loose-weft texture (LT). Results of static ELS test and fatigue ELS test showed that in the ST case, the fracture toughness of the specimen with GI/GII=0.500 was the lowest and the crack growth rate of the specimen with GI/GII=0.500 was the highest. In the LT case, however, the fracture toughness of the specimen with GI/GII=1.33 was the lowest and the crack growth rate of the specimen with GI/GII=1.33 was the highest. Results of microscopic observation showed that the fracture pattern of the specimen with GI/GII=1.33. was mixture of those of samples with GI/GII=3.76 and 0.500. In modeling of fracture by maximum stress theory, the deformation and failure of specimens with GI/GII=3.76 and 0.500 were simulated by FEM. The analytical results showed good agreement with the experimental results.
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  • Masaichiro Seika, Masakatsu Sugiura, Mitsugu Tsuboi
    1995 Volume 61 Issue 581 Pages 146-152
    Published: January 25, 1995
    Released on J-STAGE: February 21, 2008
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    Nickel foil strain gages are attached on the surface of a specimen subjected to repeated loads, and the elastic stresses are measured by observing slip bands in the foil gages resulting from repeated strains. Calibration studies with rotating-bending tests at various temperatures in the range of room temperature to 350°C are performed on round steel bars with nickel foil. The relationship between the threshold stress for the first appearance of slip bands and the number of stress cycles is examined at varying temperatures in a range of about 100°C, which provides the calibration values of the nickel foil tested at varying temperatures. Furthermore, assuming that the first appearance of slip bands is based on the linear cumulative damage law, the calibration values at varying temperatures are calculated from those established by the calibration tests at several constant temperatures. The calculated calibration values are compared with the results obtained by the calibration tests at varying temperatures.
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  • Hirotsugu Inoue, Kikuo Kishimoto, Tomoaki Nakanishi, Toshikazu Shibuya
    1995 Volume 61 Issue 581 Pages 153-160
    Published: January 25, 1995
    Released on J-STAGE: February 21, 2008
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    The wavelet transform is applied to time-frequency analysis of dispersive stress waves. The Gabor function is adopted as the analyzing wavelet. The magnitude of the wavelet transform of wave data takes its maximum value at the time when the stress wave reaches the observation point with its group velocity at each frequency. An experiment on the flexural wave in a beam shows that the dispersion relation for the group velocity can be accurately identified by the wavelet transform of measured data. In addition, the application of the wavelet transform to ultrasonic testing of a polymer alloy shows that changes in velocity and attenuation coefficient due to mechanical damaging can be evaluated at each frequency. These results suggests that the wavelet transform has potential ability to present more detailed evaluation of material damages.
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  • Masahiro Arai, Tadaharu Adachi, Hiroyuki Matsumoto
    1995 Volume 61 Issue 581 Pages 161-168
    Published: January 25, 1995
    Released on J-STAGE: February 21, 2008
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    In the boundary element method (BEM), analytic fundamental solutions with weight functions are use as the solution of the field equation. Since these functions have singularity, when an integral point is close to the source point, the accuracy is determined by that of the numerical boundary integration. In the present papar, all integral equations for the potential and gradient, are obtained by a technique based on the uniform gradient condition. As a result, all of the singlarities in the integral equations for potential, gradient and these of the internal point are normalized in the same manner. Through some numerical results of models under several boundary conditions, it is shown that unknown nodal values along the boundary are more accurate than those obtained by the usual methods, and the accuracy of the potential and gradient at internal points near the boundary, has clearly been improved.
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  • Shiro Kubo, Shinjiro Kuwayama, Kiyotsugu Ohji
    1995 Volume 61 Issue 581 Pages 169-176
    Published: January 25, 1995
    Released on J-STAGE: February 21, 2008
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    Inverse boundary value problems deal with the estimation of boundary values on incompletely prescribed boundaries. Numerical analysis of inverse boundary value problems using discretization methods can be reduced to solving simultaneous equations, which are ill-conditioned due to the ill-posedness of the problems. Errors included in prescribed boundary values are therefore magnified remarkably by inverse calculation without regularization. In this study, the mathematical structure of this error magnification behavior was studied theoretically for inverse boundary value problems of the Laplace field. Singular value decomposition was applied to evaluate the magnification amplitude called the condition number, which was given as the ratio of the maximum singular value to the nonzero minimum singular value of the coefficient matrix. The condition number was found to represent the magnification amplitude of the highest frequency fluctuation mode of variables. A regularization method using effective pseudoinverse was introduced, in which the rank of the coefficient matrix was reduced to effective rank and therefore small singular values were ignored. The effectiveness of the use of the effective pseudoinverse was explained using the singular values and the right singular vectors. An equation was proposed for evaluating the condition number. The admissible condition number method was proposed for determining the effective rank. Numerical simulations showed that the proposed equation and method were useful for estimating the condition number and the effective rank, and obtaining good estimates of boundary values.
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  • Hideki Sekine, Takanori Sasaki, Hisao Fukunaga
    1995 Volume 61 Issue 581 Pages 177-182
    Published: January 25, 1995
    Released on J-STAGE: February 21, 2008
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    Smart structures using induced strain actuators, for example, piezoelectric actuators or shape-memory alloys, may be expected to achieve active damage control. In particular, piezoelectric actuators have the capability to induce various amounts of strain upon being activated, therefore, it is possible to reduce the stress concentrations under varying external load conditions by distributing them in high stress regions in advance. In this paper, an adaptive structure model is proposed for reduction of stress concentrations by using piezoelectric actuators. The model is concerned with a simple actuator/substructure system in which the substructure is an infinite isotropic plate with a circular hole, and actuators are bonded to the plate surfaces around the hole. In order to examine the performance of the adaptive structure, optimally applied voltage to each piezoelectric actuator is calculated to minimize the maximum circumferential stress at the hole boundary in the cases of some external stress conditions.
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  • Hiroshi Hasegawa, Keishi Kawamo
    1995 Volume 61 Issue 581 Pages 183-190
    Published: January 25, 1995
    Released on J-STAGE: February 21, 2008
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    This paper presents a method for the shape and topology optimization (i. e., layout optimization)of mechanical structures by using a genetic algorithm. It may be difficult or not always possible to obtain the global optima for layout optimization problems by using the traditional gradient-based algorithms. The generic algorithm is known to be an excellent means to obtain the global optima for the problems. The algorithm, however, usually requires a large number of generations and individuals for the final layouts to be obtained certainly. We propose a method in which the behaviors of layouts are pursued for the optimum layout by selecting the layouts of the mechanical structures as individuals instead of the finite elements, and by adopting removal and addition parameters of elements as chromosomes. The efficiency and reliability of the method are demonstrated with various experiments for finite-element models of two-dimensional continuums and for minimum weight problems.
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  • Takukya Sato, Taeko Nomoto, Kenichirou Kado, Genki Yagawa, Shinobu Yos ...
    1995 Volume 61 Issue 581 Pages 191-197
    Published: January 25, 1995
    Released on J-STAGE: February 21, 2008
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    This paper describes a new user-friendly structural design system for pressure vessels which is based on finite element stress analyses. A basic concept of the developed system is to minimize the input data required for the finite element analyses and to perform the analysis quickly. To realize this, the system consists of the finite element modeling module based on fuzzy knowledge processing, the input data generation module, the finite element analyzer, the graphical user-interface module for analysis results and the stress evaluation module. Fundamental performances of the present system are clearly demonstrated through the analysis of a top nozzle.
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  • Nobuhiro Yoshikawa, Shigeru Nakagiri
    1995 Volume 61 Issue 581 Pages 198-204
    Published: January 25, 1995
    Released on J-STAGE: February 21, 2008
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    A new formulation for homology design is proposed based on the finite element sensitivity analysis. The constraint for homology design is neatly represented by a vector equation with respect to nodal displacements. Homology design to maintain a quadratic curve in a structure before and after the deformation can be efficiently carried out due to the straightforward representation of the constraint. An inequality constraint to maintain structural stiffness is added to the homology design. The inequality constraint is transformed into the equality constraint by introducing slack variables. The governing equation of the design variables is derived by the combination of these two equality constraints and solved by means of the Moore-Penrose generalized inverse. The first-order sensitivity analysis is utilized in the derivation. The validity of the proposed method is demonstrated in the numerical examples using a planar truss structure. Quadratic curves, such as the parabola and circular arc, are formed for the structure by assigning design variables to cross-sectional areas of the members. The limitation of nodal displacement is imposed as an inequality constraint to maintain the stiffness of the structure.
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  • Ryohei Ishida, Tetsuji Sato, Yoshihiko Sugiyama
    1995 Volume 61 Issue 581 Pages 205-210
    Published: January 25, 1995
    Released on J-STAGE: February 21, 2008
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    The present paper describes the applications of the genetic immune recruitment mechanism (GIRM) which is a combination algorithm of the genetic algorithm (GA) and immune recruitment mechanism (IRM) founded upon the immune network model. The GIRM is applied to the optimum design of a truss structure. Two optimization problems of a ten-member truss structure are examined. The problems are 1 ) to find nodal locations of the truss with minimum weight and 2 )to find combination of materials of truss members with minimum weight and minimum cost under the constraints of full stress and buckling. Simple GA is also applied to the same problems. Comparison of the results by GIRM and simple GA shows the effectiveness of the GIRM.
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