When bonded dissimilar materials such as ceramics/metal are designed for enhancing bonding strength, it is desirable to design interface shapes which make the stress singularity that occurs near the edge of the interface disappear or decrease. However, the desirable design for interface shapeswhich was based on theoretical analysis indicated the possibility of the relaxation of residual stress. Therefore, data which were based on the experimental result were required, to obtain the guiding principle of joint design to achieve a high-strength joint. In this work, to clarify the desirable interface shapes which relax residual stress or enhance joint strength, the joint strength was evaluated. A comparison between experimental results using TiB₂-Ni joint and results obtained using theoretical and finite-element methods were performed.

抄録全体を表示

The present authors showed that the free-edge stress singularity in bonded dissimilar materials disappeared for certain combinations of wedge angles of the pair of materials. In the present study, the stress distributions on the interface of bonded dissimilar materials with smooth free-edges were calculated by the boundary element method, under the geometrical condition of the disappearance of free-edge stress singularity. The shape of interface or the shape of free-edges was changed systematically to find the shape minimizing the maximum normal stress or the maximum shear stress on the interface. The normal stress on the interface was concentrated at the center of the interface and near the intersection of the interface and free-edge. It was found that an optimum shape of the interface or the free-edges existed for which the maximum normal stress was minimized. The shear stress on the interface was concentrated at a point near the intersection of the interface and the free-edge. The maximum shear stress was decreased for small curvature of the interface or the free-edges near the intersection of the interface and free-edge. These findings can be used for shape design of bonded dissimilar materials.

抄録全体を表示

Singular stress analysis of a Si₃N₄/SUS304 joint with a copper sheet as the interlayer was performed for tensile and 4-point bending specimens with and without residual stress using the elastic-plastic finite-element method (FEM). It was found that the superposition principle is not applicable, by summing loading and residual stresses. The singular stress on the ceramic side near the interface can be expressed in the form of σ=K/x^λ (x : distance from interface). The values of the exponen λ and the intensity coefficient K were examined. With increasing loading stress, λ and Kvary nonlinearly reflecting the change of the plastic zone size in the interlayer. However, after the general yielding of the interlayer, λ becomes constant and K increases linearly for both cases with and without residual stress. A fracture assessment diagram on the λ - K plot is proposed to evaluate the crack initiation in a ceramic/metal joint.

抄録全体を表示

In this study, stress and displacement fields at the interface crack tip between dissimilar orthotropic materials are presented for the case where the principal axes of orthotropic materials are not aligned with the interface, based on the orthotropic elasticity theory. The correct form of the definition of stress intensity factors for the interface crack is clarified. This definition is consistent with that of orthotropic material and also of dissimilar isotropic materials. The extrapolation method to determine the stress intensity factors by numerical analysis is proposed based on this definition. Some interface cracks in a finite plate of dissimilar orthotropic materials are analyzed by BEM and the stress intensity factors are presented.

抄録全体を表示

In this study, the energy release rate is derived for interface debonding cracks in ceramic-matrix composites, using approximate solutions of an axisymmetric cylindrical fiber-matrix model. The energy release rate expression includes the important effects of compressive residual stresses and frictional sliding stress on the debonded interface in a closed-form equation. A parametric study of the energy release rate is carried out and the effects of various parameters on the energy release rate are clarified and compared with results of other studies. The method to determine the critical debonding length is proposed based on the energy release rate and the fracture criterion of the interface and fiber. The predicted debonding length gives good agreement with published experimental results.

抄録全体を表示

A bimaterial problem of strips which are bonded at their ends is solved. The strips have debondings at both sides of the interface and the debonding lengths are changed. Concentrated loads are applied at the tips of each strip. The complex variable method and a rational mapping function are used for the analysis. Stress distributions are shown for two cases in which locations of the interface are different. Stress intensity of debonding is defined and the values are obtained for some debonding lengths. Aspects of the debonding are investigated. The effect of material constants on debonding is also investigated.

抄録全体を表示

An equation was derived by which local stress distributions controlling interfacial crack behavior in dissimilar materials can be assessed from discontinuous displacements along a crack on the interface, based on the complex-valued formulas for the stress and displacement of a two-dimensional crack. The residual stress distribution along the interfacial crack was defined as the difference between this estimated local stress and the applied stress distributions, the validity of which was shown using FEM analysis. The stress intensity factor was also evaluated from the estimated stress distribution for the interfacial crack, using the equation which was derived based on the complex potential function with a Green's function. These values were compared with the stress intensity factor obtained from the extrapolation method in terms of the displacements near the crack tip calculated by the FEM analysis.

抄録全体を表示

In this study, a new method to evaluate the adhesive strength of the interface between resin liner film and cement mortar has been developed. The peel test for vinyl ester resin liner films on cement mortar surfaces was carried out. The critical energy release rate (G_c value) was obtained from the peel load and crack length measured during the peel test. G_c values were not affected by the crack length or the thickness of resin liner film. Therefore it was established that G_c values could be used to evaluate the adhesive strength of resin liner film. Furthermore, the effect of primer coats on the adhesive strength of resin liner film were revealed by obtaining the G_c value.

抄録全体を表示

In this study, a thermal stress problem is solved for a layered half-space when a portion of its surface is heated by temperature discontinuity. When the thermal conductivities of both materials are made equal, the solutions become those for a temperature field which does not produce any stress in the case of homogeneous material. Here it is verified whether there exists a condition for stresses to disappear between the coefficient of thermal expansion and elastic constants. As the result, we found that thermal stress disappears when α₂/α₁= 1 for plane stress, as expected, and when α₂/α₁= (1+ν₁)/(1+ν₂) for plane strain, which was not expected, α being the coefficient of thermal expansion, and ν Poisson's ratio. The physical meaning of the conditions and their extension to finite or three -dimensional bodies are discussed, and also a method of making combinations of materials of any coefficient of thermal expansion stress free is given.

抄録全体を表示

The arrest of delamination between the die pad and the resin is expected to be an efficient method to prevent resin cracking of LSI packages. In some LSI packages, dimples properly arranged on the die pad surface prove to be efficient for the arrest of delamination. In this study, the effect of dimples is examined based on BEM analyses of LSI package under conditions of uniform temperature variation and vapor pressure. To evaluate this effect, the stress intensity factor K₁ for an interface crack is calculated considering the contact of interface crack surfaces. The following results are obtained. (1)K_i. values for an interface crack along a dimple significantly decrease under both of the above conditions. (2) The decrease in K_i is mainly due to the contact of crack surfaces under uniform temperature variation and the change in the direction of crack extension along a dimple under vapor pressure condition. (3) The effect of delamination arrest increases as the dimple depth increases.

抄録全体を表示

The adhesion strength evaluation of molding compounds is a critical issue in structural design and material selection of IC plastic packages, because interface delamination is a main cause of package failure. We previously proposed a method that measures true adhesion strength without the effect of residual stress. This paper describes the dependence of true adhesion strength on adherend materials, temperature and molding compound moisture content as determined by this method. We have also tried to predict interface delamination within a package by comparing the measured strengths with thermal stress analysis results. The results suggest that interface delamination during soldering is caused by thermal stress and decrease in true adhesion strength caused by absorbed moisture rather than vapor pressure.

抄録全体を表示

Recently, adherend thickness has tended to decrease to lighten the adhesive composite structures. In this study, the mechanical behavior of CFRP adhesive joints was examined in the case in which a thin adherend was used. AE measurement and FEM analysis were performed. The adhesive-strength evaluation method that used the stress singularity parameter was applied to FEM results. Initial failure strength, which was an important factor applying the cyclic load, could be found by AE results. It was clarified that the initial failure strength decreased when thin adherend was used. According to FEM analysis, the initial failure strength could be evaluated by the intensity of the stress singularity. It was clarified that the initial failure strength decreased, since the intensity of the stress singularity at the adhesive edge increased when adherend thickness decreased, and that intensity increased, since the tensile deformation gap between the adherends became widened.

抄録全体を表示

Fatigue damage processes of continuous E-glass-fiber-reinforced epoxy laminates under tension-tension fatigue were compared between plain-weave roving fabric, cross-ply and quasi-isotropic laminates. The fatigue tests were performed for double-edge-notched parallel-plate specimens. The damage area was photographed at appropriate intervals, together with the measurement of compliance. For the unwoven unidirectional-ply laminates (the cross-ply and quasi-isotropic laminates), the damaged zones grew progressively in the form of delamination, fiber splitting and matrix cracking, and their shapes were characteristic of the ply configuration. The woven fabric laminate, on the other hand, was deteriorated by propagation of a single crack emanating from the notches, and the damaged zone was concentrated in the vicinity of the crack surface. An almost linear relation-ship between the delamination area and the compliance was observed. The rates of delamination and the characteristic delamination length for the unidirectional-ply laminates correlated well with the compliance in a power-law relation.

抄録全体を表示

AE monitoring tests are conducted on the specimens with different angles between the directions of applied load and the yarn of cross-ply CFRP or plain woven CFRP. Effects of water environment on the ratio of the loads P_b and P_c determined by the AE energy gradient method to the maximum load R_max are discussed. The crack initiation and propagation at notch tip are observed by a monitor microscope and the damage modes of constituents are investigated by AE frequency analysis at or near the points of P_b/P_max and P_c/P_max. The ratios of P_b/P_max and P_c/P_max are important points to clarify fracture mechanisms of CFRP.

抄録全体を表示

Fracture toughness for crack along a long fiber and the fatigue crack growth rate in the same direction were experimentally examined in Si-Ti-C-O fiber-reinforced aluminum composite under mixed-mode loading of modes I and II. The fracture curve under mixed-mode loading was expressed by the equation (K_I/12.0)²+(K_II/15.5)²=1, where modes I and II fracture toughnesses are 12.0 and 15.5 Mpa·m¹/2. In this case the fracture toughness of the composite material is not described by any fracture criteria proposed for common homogeneous materials. It, however, is best interpreted by the strain energy release rate criterion among these criteria. The scanning electron microscope observations showed that the crack extended through the aluminum matrix along the fiber-arranged direction under any mixed-mode loading conditions. Such a fracture mode might induce a characteristic fracture which is not dominated well by the common criteria. A fatigue crack under mixed-mode loading also extends through the aluminum matrix, leaving a striation, and its growth rate is governed well by the effective equivalent stress intensity factor range evaluated on the basis of the concept of strain energy release rate.

抄録全体を表示

Cavitation erosion tests were carried out for SiC-whisker-reinforced aluminum composites and their base metal using a vibratory apparatus. The matrix metals were pure aluminum and three aluminum alloys (A6061, A2024 and A7075). The volume fraction of whisker was about 20 percent for all composites. Erosion behaviors were discussed based on the measurements of mass loss, eroded surface profiles, and the distribution of erosion particles. The erosion resistance of composites is markedly higher than that of base metal and the increase is more effective for the matrix with lower hardness. This is because erosion particles become smaller and crack growth is prevented by the presence of whiskers, resulting in a low rate of particle removal. The effect of heat treatment was also studied for the A2024 base metal and the composite. The erosion resistance of the base metal sharply increased with an increase in hardness by the heat treatment. However, heat treatment did not improve the erosion resistance of the composite, because it did not eliminate defects at the tips of whiskers and did not effectively increase the hardness of matrix due to the presence of whiskers. Macroscopically, the erosion resistance increases with H_B²/E (H_B : Brinell hardness and E : Young's modulus) of the composites, but remains constant in the case of heat-treated composites.

抄録全体を表示

Rotating bending fatigue tests were carried out on specimens of an extruded aluminum alloy and a drawn aluminum alloy in air and in oil in order to investigate the effect of the oil environment on the fatigue strength. In the drawn aluminum alloy, the fatigue lives increase by the existence of oil under all stress levels. On the other hand, in the extruded aluminum alloy, the fatigue lives in oil and in air are nearly equal to each other under high nominal stresses, though the fatigue lives increase by the oil when the stress level is low. Moreover, S-N curves in the extruded aluminum alloy show the shape of the double stages in both environments. The crack propagates in the tensile mode, except for the extruded aluminum alloy under the high nominal stress, where the crack propagates in the shear mode, regardless of the environment. Therefore, the double stages of the S-N curve in the extruded aluminum alloy are caused by the change in the fracture mode depending on the stress level.

抄録全体を表示

The effect of macroscopic residual stress on the fracture of an Al-Al₃Ni functionally gradient material (FGM) has been studied. The material has a graded volume fraction of Al₃Ni intermetallic particles in a continuous Al phase. Specimens were machined from a thick-walled tube of in-situ Al-Al₃Ni FGM that was fabricated by centrifugal casting. The level of macroscopic residual stress present in the hoop direction can be modelled accurately using an uniform temperature change of 160K from an assumed stress free temperature of half the melting point (of the Al matrix). The residual stress distribution changes through-thickness from tension (inner surface) to compression (outer surface). By a superposition of applied and residual stresses a failure (crushing) stress of 130 MPa is obtained. Radial cracks are initiated symmetrically on inner surfaces at positions of maximum applied tensile stress. These cracks do not propagate catastrophically under a constant applied stress, but rather they arrest. Crack opening displacement measurements confirm that as cracks propagate they close under the action of residual stresses. Fractographs show that Al₃Ni intermetallic particles fail by transgranular cleavage, and they are surrounded by ductile failure of the continuous Al matrix. The crack path preferentially follows cracked Al₃Ni particles.

抄録全体を表示

Micromechanisms of fatigue crack growth in an Al-Al₃Ni functionally gradient material (FGM) have been investigated. The distribution of Al₃Ni intermetallic particles is graded radially through the continuous Al phase. Ring testpieces and bend testpieces have been machined from a thick-walled tube of FGM, and they have been subjected to cyclic loading under diametrical compression and four point (pure) bending, respectively. Fatigue cracks initiate more easily on the inner surfaces of the ring testpieces and their growth is affected by the residual stress state which changes through the ring from tension (at the inner surfaces) to compression (at the outer surfaces). For such testpieces the crack growth resistance curve is extremely difficult to determine. In testpieces subjected to cyclic bending, a stress ratio dependence of crack growth rates is observed, and Paris exponents of 8-10 have been determined. Crack paths are deflected along chains of brittle Al₃Ni particles. These particles appear to fail by transgranular cleavage, and this fraction of the fracture surface is then relatively smooth. Crack growth through the Al matrix produces rougher features, and striations are found occasionally. Of interest, periodic markings are also observed on Al₃Ni particles in some cases. It is concluded, that the high Paris exponents can be attributed to "static mode" failure of the intermetallic particles.

抄録全体を表示

Establishment of creep-fatigue life evaluation methods for high-temperature components in thermal power plants is important for assessment of remaining life. In this study, creep-fatigue tests were conducted by a high-temperature fatigue testing machine with two rotor materials and one boiler material. In order to study the creep damage mechanism during the stress relaxation process, a creep mechanism map was established based on the creep defomation theory. From the detailed comparison between the mechanism map and observed failure results, it was suggested that creep damage during relaxation should be divided into matrix creep damage and grain boundary creep damage. Considering these two types of damage for evaluation of creep damage during relaxation, a nonlinear damage accumulation model for creep-fatigue damage evaluation was newly proposed. Creep-fatigue life for all materials could be predicted well by a life prediction equation derived from the model.

抄録全体を表示

Fatigue failure of a hole notched glass FRP under tension-torsion combined cyclic loading is investigated in this paper. Thin cylindrical specimens were used. The composition of specimens was the same as that in part 1. As a quasi-crack growth had been observed under fatigue loading which led to the final failure, the fracture mechanics was applied to characterize the fatigue failure process. The energy release rate was used as a parameter for progressive failure. Fatigue life estimation under combined cyclic loading was attempted based on the fracture mechanics. Predicted S-N lines agree well with the experimental results except in a few cases.

抄録全体を表示

The influence of target thickness and projectile size on the projectile impact damage generated on SiC targets is investigated. The projectile impact generates several types of damage such as a ring crack, a crater or a cone crack. In the case of thick targets, the residual strength of the targets does not depend on target thickness. This is due to that damage is generated only near the impacted surface. On the other hand, in the case of thin targets, the residual strength drops drastically. This is due to the generation of "back surface cracks." In addition, the projectile size affects the residual strength and the cone crack size. However, the minimum impact velocity at which ring cracks are generated does not change with projectile size.

抄録全体を表示

Studies by using an acoustic emission (AE) method have been undertaken to elucidate the fracture mechanisms of AFRP in the static tensile test. The materials used were a unidirectional [0]₈ aramid fiber and a quasi-isotropic elastic [0/±45/90]_s aramid fiber reinforced plastic in which fiber volume fraction (V_f) was 55%. In this paper, the frequency of the detected AE waves has been studied. On tensile loading, it was recognized that the fracture mechanisms of AFRP were characterized by some microfracture phenomena such as delamination, fiber debonding (debonding at the interfaces between fibers and resin), matrix cracking and fiber breaking. In a unidirectional material, much fiber debonding has been found. On the other hand, much delamination has been seen in a quasi-isotropic elastic material. To generate the fracture mode which causes these phenomena, six-specimens were tested and AE waves were detected. Using the results of the frequency analysis, it was found that the frequency distributions of AE waves corresponding to matrix cracking, delamination, fiber debonding and fiber breaking are 20-50, 50-135, 135-180, and over 180 kHz, respectively. It was confirmed that the fracture phenomena were related to characteristics of the frequency distribution.

抄録全体を表示

The tensile impact tests of short-glass-fiber-reinforced polycarbonate (FRPC) specimens with fiber content of 30 wt%, which are molded under different conditions of screw design and number of screw rotations, are conducted using a tensile impact tester of the Hopkinson pressure bar system. The specific impact strength and the specific impact absorbed energy can be determined, and the significance probability of the tensile impact strength is evaluated.

抄録全体を表示

In this paper we describe a basic experimental study of the deformetion and strain in the vicinity of the crack tip under impact loading in an attempt to clarify the dynamic fracture mechanism of mild steel. The experimental apparatus was developed using an air gun for the high-speed three-point bend test which allowed the measurement of the displacement rate of the load point. We developed a new and simple method of measuring the displacement rate using a sliding variable resistor. The three-point bend tests were performed using the above apparatus with a high-speed impact load. Three-dimensional FEM calculations were performed to compare the experimental results with the simulated results. In the simulation computation of three-dimensional FEM, the constitutive equation of Johnston-Gilman type was proposed by the authors and has been used. Additionally, the dynamic responses of strain in the vicinity of the crack tip and the values of crack tip opening displacement (CTOD) were shown by both numerical calculations and experimental results. Finally, taking into consideration the FEM calculation results, we discussed the behavior of deformation near the crack tip.

抄録全体を表示

This paper describes the complementary relationship between stress and displacement solutions in nonlocal elasticity. It is derived from the definition of nonlocal stress and the equilibrium equation. The stress solution in an infinite plane subjected to a uniform compressed load is given. It is assumed that the nonlocal effects of the matrix and inclusion are the same, and these effects cross the boundary between the matrix and inclusion. The stress distribution around the hole is drawn graphically using this solution. One of the effects of nonlocal elasticity is the development of the stress relaxation zone around the hole.

抄録全体を表示

A flexible cantilever beam subjected to a rotational load is commonly encountered in mechanical elements, for example, a flat spring under a spring limit test, a leaf spring in a vibrating conveyor or a paper machine, a jib ( : boom) of a jib crane or a luffing crane, an arm of an industrial robot or a manipulator, and an aircraft wing. In such elastic elements, a large deflection is produced without exceeding the elastic limit of the materials. This property is of both analytical and technological interest. It is necessary to analyze the large deflection behavior to achieve high reliability of the structural components. The purpose of this report is to clarify the large deflection problem, namely elastica problem, of a cantilever beam. As an analytical example, an inclined concentrated load at the free end of a spring-hinged cantilever beam was solved in terms of elliptic integrals as well as by carrying out a large flexural-bending test. Experimental data agree very closely with the theoretical results.

抄録全体を表示

The demand for high-performance engineering materials with specific functions is constantly increasing. Accordingly various composite materials are being developed. This research deals with the clad sheet which is composed of stainless steel and aluminum, produced by pressure welding of hot rolling. The unique deformation properties of the clad material were discussed. Furthermore, the characteristics of the localized necking and the crack initiation of the individual materials composing the clad sheet were investigated separately. In this research, the relationship was determined from the result of the tensile test of clad sheet only. Next, the tensile test of an individual which was prepared by removing the other material from the clad sheet was carried out. The results of the above experiments show that the estimated and measured parameters of the stress-strain curves are in good agreement. Finally, the plastic instability was discussed.

抄録全体を表示

Changes in the specific resistance ratio due to the isothermal annealing treatment were investigated experimentally for the cold rolled Al-5 mass % Mg binary alloy. Isothermal annealing treatments were carried out at temperatures ranging from 373 to 573 K. The following findings were obtained from the present study : (1)Precipitation of β-phase was promoted by the strain induced by the cold rolling, leading to remarkable increments in the specific resistance ratio with increasing annealing time which were observed for the 90% cold rolled Al-5 mass % Mg alloy as compared to those of the 5083 alloy. (2) Microscopic strains in the cold rolled Al-5 mass % Mg specimens decreased with increasing in annealing time. On the otherhand, microscopic strains in the specimens annealed at 373 K for more than 120 ks increased. (3)Increasing the rate of the specific resistance ratio led to the peak value at the annealing temperature, 453 K.

抄録全体を表示

Anisotropic elastic constants of transversely isotropic aluminum composites reinforced with short alumina fibers have been determined based on ultrasonic velocities measured by the direct-contact normal incidence and water immersion methods. Two of the elastic stiffness values among a total of five were determined from ultrasonic velocities measured by the direct-contact method. The others were estimated from the quasi-transverse velocity obtained by the double-transmission immersion method. Young's moduli thus obtained are very close to those measured by the 4-point bending test. Experimental error in determining the elastic constants was discussed and the allow-able range of experimental parameters was quantitatively evaluated.

抄録全体を表示

In this paper, the authors present a new theory of propagation of ultrasonic waves in porous ceramics. The idea is based upon the arrival probability of ultrasonic rays. When incident rays impinge a pore, they creep around the pore surface and delay the propagation time. We studied this process from a probabilistic standpoint, and found that the propagated waveforms can be expressed as Gaussian functions. The Gaussian waveform is determined from the porosity, mean pore size and pore shape. This new finding revealed the following important laws. (1)The delay time of an ultrasonic wave passing through porous ceramics is proportional to the porosity ; (2)the pulse width of the wave becomes wider with the increase in mean pore size ; (3) the amplitude of the wave decreases with the mean pore size : and (4) the delay time and pulse width of the wave increase with the mean pore perimeter. Formulas for these relationships between ultrasonic and porous characteristics were derived, and an ultrasonic method to evaluate porosity and mean pore size was proposed.

抄録全体を表示

For the purpose of developping an ultrasonic method to nondestructively evaluate micro pores in ceramics, we have been studying the propagation mechanism of ultrasound in ceramics. In the first report, we proposed a theory of propagation of ultrasound based on a probabilistic new idea. In this second report, preparing alumina ceramics with different pore distributions, we verfied our theory experimentally. The experimental results proved our theory that the ultrasonic waveform propagating through porous ceramics is determined by the convolution integral of Gaussian function and the waveform propagating through non-porous ceramics. This new finding made the quantitative relationships clear between ultrasonic waveforms and pore distributions (porosity, pore size and pore shape), which enables us to nondestructively predict the porosities and mean pore sizes in ceramics.

抄録全体を表示

We investigated three-dimensional ultrasonic diffraction by numerical simulation, and derived the amplitude loss and phase shift caused by the diffraction. The simulation is based on the general solution and has been performed on a model in which a transducer consists of infinitesimally small openings, which independently satisfies the Dirichlet boundary condition on the transducer surface ; the ultrasonic wave incident from the back of the surface diffracts forward through these openings. This method is useful, when an analytical solution is unavailable. We simulated the case of near regional propagation where the wavelength is not necessarily small relative to the path length and also the case where the transducer has arbitrary geometry and strength distribution over the radiating area. These results are useful in correcting the diffractive effects in practical ultrasonic measurements.

抄録全体を表示

A new method was proposed for measuring normal strain using a high-frequency diffraction grating. A laser beam illuminated the grating attached on the surface of a specimen. The frequency of the grating was 900 lines/mm. The shift of diffracted beam spots from the grating was measured with two PCD linear image sensors connected to a personal computer in order to determine the normal strain caused by an applied load. The measured light intensity profile was approximated by a Gaussian function and the location of the intensity profile was determined as the main axis of the function. This method was applied to the measurement of elastic normal strain of a cantilever steel beam. The strain measured using this method agreed well with the strains measured using a strain gage and calculated from the elasticity theory.

抄録全体を表示

The authors have studied the shape-memory phenomena of ceramics, mainly of glass ceramics. They found that most polycrystalline ceramics exhibit shape-memory phenomenon. The starting temperature of shape recovery corresponded to the starting temperature of stress relaxation in every shape-memory ceramics. These experimental results showed the shape recovery process as follows. If a specimen is deformed in the high temperature range and cooled to the room temperature and released, the viscosity change of the glass matrix or boundary restrains the elastic deformation of the crystal. The specimen in this condition can recover its original shape upon reheating. The authors also found that two factors of mica glass ceramics enabled the network of mica crystals to behave like a high compliance mechanical spring system. One is the "card-house-type" microstructure ; the other is the connected form of mica crystals. This is why mica glass ceramics can recover their shape 5 to 20 times better than ordinary polycrystalline ceramics. Based on these results, this paper describes a guideline for designing the shape-memory ceramics and shape-memory composite materials.

抄録全体を表示

This paper deals with topological optimization of elastic frames by means of the boundary cycle used in the algebraic topology and genetic algorithm. The optimum frame is so defined in this study that the deformation of an interesting point of the frame is minimal for a given limit of weight, and that any members with a tip not connected to other members, except loading points, are eliminated. The optimum topology is searched efficiently through the boundary cycle which yields the one-dimensional simplicial complex without any tip, satisfying the topological condition of no idle tip present. The boundary cycle is derived from the chain and boundary homomorphism which plays an important role of decoding of the genotype into the phenotype in the genetic algorithm, and is included in the string used in the genetic algorithm for the representation of frame topology. The numerical examples are concerned with minimization of the deformation of two-dimensional frames subject to bending, and three-dimensional frames subject to torsion or expansion.

抄録全体を表示

This paper describes an application of a mutual combination-type neural network to the optimum design problems of statically indeterminate truss structures. In the problem, it is difficult to express the objective functions and restrictive conditions in the theory of neural networks. A special algorithm including the structural analysis and the neural network search is proposed. The hopfield model and the quadratic energy function are used to solve the optimum design problems. From the numerical examples of the 5-member truss and 14-member truss structures, it is shown that the proposed method is very useful.

抄録全体を表示