The effect of anisotropy on fatigue properties of notched carbon fiber reinforced plastic laminates has been studied. The off-axis angle of carbon fiber was varied from 0° to 45°. The ultimate tensile strength and the tensile elastic modulus drastically decreased when increasing the off-axis angle of carbon fiber to 30°. When the off-axis angle of carbon fiber increased over 30°, these values approached approximately constant values. The maximum tensile strain also increased and saturated to a constant value when the off-axis angle of the carbon fiber increased. The fatigue strength of notched CFRP laminates showed a similar dependence of ultimate tensile strength on the off-axis angle. The decrease of fatigue strength results from the fatigue damage in relation to the off-axis angle. The fatigue damage process was analyzed in terms of AE measurement and fractography. These results indicate that the fatigue damage process of CFRP laminates was significantly affected by the off-axis angle of carbon fiber.

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For the purpose of establishing an integrated explanation of fracture mechanism in the material, the authors have discussed several features of crack growth threshold in an epoxy resin which shows remarkable time-and temperature-dependent mechanical behaviors. Namely, using a wide strip specimen having a long (semi-infinite) crack perpendicular to the free edge, slow and stable crack growth behavior was carefully observed under a constant rate of displacement and several temperatures over the viscoelastic range of the material. Then a time-and temperature-independent crack growth resistance was successfully obtained from crack growth curves and an extended J-integral for a linearly viscoelastic material. Minute fracture surface roughness was measured quantitatively with a double-beam interference microscope. The characteristic feature of the fracture surface was seen in the neighborhood just ahead of the initial crack front. Taking the temperature and rate-dependent mobility of molecular entanglement around the moving crack front into account, some features of the submicroscopic mechanism of crack growth in this type of material are also discussed.

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When tensile stress is applied to a material, the activation energy for the generation of submicrocracks decreases and the submicrocracks are thermally generated at the tip of the crack. These submicrocracks remain stable by relaxing the elastic energy around them. The submicrocracks grow by coalescence and become unstable as the density of submicrocracks increases. The submicrocracks at this stage are considered to be disk shaped and are called microcracks in this paper. Since the stress is intensified around the microcracks, the microcracks grow by the generation of submicrocracks around them. The microcracks at this stage grow in a self-similar manner, statistically. The radius γ of the disk-shaped microcrack is found to grow in time as γ ∝ t^α, where α is a positive number. The author postulated that the initiation of the crack propagation is controlled by the growth of the microcrack generated at the tip of the crack. This postulate predicts the existence of two different velocities of the crack at initiation, when the stress intensity factor remains close to the fracture toughness. When the crack velocity is controlled by the growth of the submicrocracks at the tip of the crack, the velocity of the crack is very slow, while it becomes of the order of 10² m/s when it is controlled by the microcracks which grow in a self-similar manner, statistically. Such behavior of crack velocity was observed by Takahashi in 1987.

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In this paper, the problem of an infinite body with a crack and a fiber is analyzed. The fiber is composed of anisotropic material. The method of analysis is the body force method. The stress field caused by the fiber is expressed by the stress fields due to force doublets. The stress intensity factors for the crack are shown graphically.

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The mechanism of grain boundary (GB) crack initiation in low-cycle fatigued 70/30 brass is investigated on the basis of the observation of dislocation structures and surface topography by means of transmission and scanning electron microscopy. The dislocation structures are almost the same as those observed in a high-cycle fatigue test. Although typical dislocation structures are not indicative of strain localized regions (SLRs), the SLRs are recognized in the favorably oriented grains. At the intersections of such SLRs with the GB, extrusion-type GB deformations are frequently observed. These GB deformations are considered to be responsible for GB cracking. Based on the observations, the possible mechanism for the GB cracking in low-cycle fatigued 70/30 brass is discussed.

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The relationship between the crack surface morphology and the crack growth rate under stress corrosion cracking (SCC) and fatigue interaction was investigated using 12CrMo steel tempered at 400°C. The transition of cracking morphology from transgranular to intergranular was observed as SCC component increased. The crack growth rate was determined by fatigue process in the transgranular region and determined by SCC process in the intergranular region. SCC and fatigue contributed independently to the crack growth rate and no interaction was observed. The linear accumulation law on crack growth rate provided a conservative estimation of SCC·fatigue interaction.

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Rotating bending fatigue tests of dual-phase steels having various microstructures were carried out in order to investigate the effect of microstructures on the crack growth resistance. The fatigue lives of plain specimens in dual-phase steels are nearly equal to each other under the same relative stress σ_a/σ_B, regardless of the differences in martensite morphology and grain sizes of the ferrite and the martensite at high stress levels, (where σ_a and σ_B are the nominal stress amplitude and the tensile strength of each material, respectively). This is explained from the fact that most of the fatigue life is consumed by the growth of small cracks which are controlled by the small-crack growth law, dl/dN∝σⁿ_al (l : crack length, n : constant), and the crack growth resistance is evaluated by σ_B of each material using this law.

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This paper considers the plane problem of metal/ceramic composite media under external normal loading. One half-plane contains a crack lying parallel to, and at a given distance from the interface. The numerical results of stress intensity factors are obtained and, by applying the maximum cleavage stress criterion at the crack tip, the direction of crack propagation is predicted in various metal/ceramic composites for various distances from the interface. The influences of bimaterial properties and the distances from the interface on the characteristics of the crack are also discussed. A finite element analysis with the automatic crack growth tracking method is also used to describe the kinking behavior of the crack initially parallel to the interface. When the distance of the crack from the interface is small compared to the crack length and to other length scales characterizing the geometry, it is shown that for the sub-interface crack the numerical results are in agreement with the results given by Hutchinson et al.

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The behavior of initiation and growth of small cracks were investigated in creep fatigue at 1273K (1000°C) using a smooth round-bar specimen of an oxide (Y₂O₃) dispersion-strengthened (ODS) superalloy, Inconel MA 754, produced by means of the mechanical alloying process. The elongated grain structure was attained by extrusion and isothermal annealing. The experimental results are summarized as follows : (1) Multiple traverse cracks (Type A) were initiated on the surface along grain boundaries perpendicular to the stress axis from the early stage to the middle stage of life. However, most of them were arrested immediately after the initiation by the grain boundary along the stress axis. (2) Transgranular cracks (Type B) began to appear from the middle stage of life. Although the grain boundary along the stress axis interfered with the growth of the Type B crack, the crack broke through the barrier and formed a main crack which brought about failure of the specimen. (3) While the elongated grain structure worked to prevent the growth of Type A cracks, it showed little effect on that of Type B cracks.

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Load-controlled fatigue crack growth tests were carried out under reversed and pulsating repeated variable amplitude loadings in post-yield region. Crack growth increment and crack closure were measured by the minicomputer-aided unloading elastic compliance method. The effects of load variation on the elastic-plastic fatigue crack growth behavior and the application of range-pair counting method to j-integral, ΔJ^*, for estimation of crack growth rates, where both one-directional and cyclic plastic deformation were observed remarkably, was discussed. It was found that fatigue crack growth rates under reversed varying loadings were estimated by the linear summation rule based on ΔJ^*, and fracture mechanics parameter ΔJ^*/(1-J_max/C), where J_max is the maximum J-integral, should be used for estimation of growth rates of fatigue cracks where residual one-directional plastic deformation occurred as was observed under pulsating varying loadings.

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The solution method for a two-dimensional piezothermoelastic problem of orthotropic solids exhibiting crystal class mm2 is proposed in the present paper. The method consists of two piezothermoelastic potential functions, three piezoelastic potential functions and a piezoelectric potential function. Three coupled second-order differential equations for those functions are derived from the equilibrium equation of stresses and the equation of electrostatics. The three differential equations can be reduced to an uncoupled sixth-order homogeneous differential equation from which one of the piezothermoelastic potential functions is obtained. Without loss of generality, the nonhomogeneous part of it can be divided into three uncoupled second-order differential equations by which the three piezoelastic potential functions are governed. The other piezothermoelastic and piezoelectric potential functions are derived from the previously obtained piezothermoelastic and piezoelastic potential functions.

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There are generally two methods, static and dynamic, for measuring an elastic modulus. However, for brittle materials, the static method was less accurate in measurement than the dynamic method because destruction occurred even before much strain was applied. In this paper, the elastic modulus was measured using ultrasonic waves propagating inside the specimen by the pulse sine wave potentiometer and oscilloscope and by the applied ultrasonic wave pulse superimpose method to calculate various elasticities. Further, the above method was applied for a thin specimen of soda lime glass and Young's modulus was measured. As a result, comparing the values measured by the deflection method to that of the static method, there were differences of about 3-8% between measurement values of both methods.

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In the conventional boundary element technique, all the boundaries of the body including those of inclusions must be discretized even when the inclusions are comparatively small. Therefore the size of the coefficient matrix of the resulting system of linear algebraic equations becomes quite large for a problem with many small inclusions. The authors have previously proposed an approach to circumvent the discretization of the boundaries of small inclusions for two-dimensional potential problems. In that approach the distribution of the potential over circular inclusions is approximated with a simple harmonic function with a small number of freedoms. In the present paper, this approach is extended to the small circular inclusions in two-dimensional elastostatic fields. The effectiveness of the present formulation is illustrated in several numerical examples.

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This paper presents analytical solutions to axisymmetric contact problems of two rigid spheres coated with elastic layers. The elastic layer is assumed to be either bonded or unbonded to the rigid sphere. In the analysis, dual integral equations are reduced to infinite systems of simultaneous equations using the technique of expanding the normal contact stress to an infinite series. Numerical calculations are performed for several values of the layer thickness and for several values of Poisson's ratio. These effects on the stress distribution and the external load are discussed.

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The macroscopic elastic-plastic deformation behaviour of inhomogeneous material is affected by the microscopic distribution of stress and strain in respective heterogeneous regions of the material. Several parameters are considered to describe the deformation behaviour of inhomogeneous material, and their relationship is discussed analytically. A model of inhomogeneous material with inclusions imbedded in a matrix is adopted for the numerical simulation of the present study. The changes of the parameters during elastic-plastic deformation are calculated and compared. Among the parameters, the constraint ratio and the plastic accommodation parameter are not affected by the degree of inhomogeneity. A modified plastic accommodations parameter is also proposed, which is uniquely related to the constraint ratio. The constraint model based on the constraint ratio is extended to describe the elastic-plastic deformation behaviour of inhomogeneous material.

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The resin for plastic packaging is experimentally investigated for viscoelastic deformation at various temperature conditions. The elastic constants are represented in terms of temperature conditions. The creep compliance is formulated by a viscoelastic model of four elements. The temperature dependency is included in the parameters of the model. The stress and strain of the resin model in the cooling process are analyzed by the finite-element method with heat transfer analysis. The deformation of a two-layered model of resin and metal in the cooling process is compared with the experimental results. The thermal deformation is predicted well by the analyzed results. The thermal residual stresses of the resin block and the plastic packaging model in the cooling process are analyzed. The resin block has large thermal internal stresses from the temperature gradient between the outer surface and the central part. The plastic packaging model also contains large thermal stress in the resin as well as at the interfaces among resin, chip and lead frame.

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Characteristic anisotropy is induced in sheet metals through the production process of rolling. Since such an anisotropy has a predominant influence on the forming limit of sheet metals, initial anisotropy must be taken into account in order to evaluate the formability of sheet metals as well as the laminated sheet metals whose layers comprise such anisotropic materials. The aim of this paper is to formulate a rational constitutive relationship for initially anisotropic (particularly orthotropic) materials and to apply it to the formability analysis of laminated composite sheets. An orthotropic yield function is formulated based on the representation theorem for isotropic tensors, and equivalence to Hill's quadratic form is shown. An application is made to the material design of a laminated sheet, particularly focusing on the variation of the γ-value which reflects the formability of sheet metals.

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In general, there are two situations bringing about multiplicity : one is statically admissible multiplicity and the other is kinematically admissible multiplicity. The former appears first, followed by the latter. They correspond to diffuse and localized neckings, respectively. When the plastic deformation of the element in a body is not largely constrained such as under plain stress, there is the possibility that multiplicity appears at the stage that the load in first principal direction becomes stationary. The condition for statical collapse of unique solution is discussed here from the phenomenal aspects of view, especially, in the case that the loading path is restricted by surrounding constraint. Then, the modified criterion is proposed which describes plastic instability occurring under the condition that maximum principal nominal stress becomes stationary. It gives multiplicity having plastic and rigid solutions on a restricted loading path. The statical collapse is demonstrated on the process of sheet formability with straight strain path.

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Rotating bending fatigue tests were carried out on quenched and low temperature tempered SAE 9254 spring steels having two kinds of microstructure in which either isolated defects (retained ferrite) or connected defects (proeutectoid ferrite) are dispersed, with a special interest in the transition of surface to subsurface fracture known as "Fish-eye fracture" in high strength steel. Discussions were made of the relationship between the fatigue fracture mode transition and the surface conditions, and also of the role of the microstructure in the formation of the Fish-eye pattern. Results show that (1) the fracture mode transition occurs in the material having isolated defects in the microstructure when a surface fracture mode is prevented by strengthening the surface layer with mechanical polishing and, (2) such a fracture mode transition is associated with the change in fatigue crack initiation process from slip band cracking of surface retained ferrite to cleavage cracking of internal retained ferrite.

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Impact fracture experiments were performed using three CT-type specimens made of PMMA with the size ratio 1 : 2 : 3 for an analogous geometry with each other. A precrack was introduced artificially in each specimen, which was impacted by a wedge bar. The impact bar was accerelated by a gas gun to impose an impact force to the wedge bar, and the fracture behavior was measured with a strain gage pasted at the crack tip of each specimen. Based on the diagram of dynamic strain history, the impact fracture toughness K_{I, IC} was evaluated. The results showed that the K_{I, IC} value of a small specimen was lower than that of a large one, and K_{I, IC} values decreased with increased of impact velocity. When a specimen was partially supported, the K_{I, IC} value increased, except for the S-size specimen. At low temperatures K_{I, IC} values increased for both size specimens. A parabola pattern was observed more densely on the fracture surface of large specimens.

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An elastic-plastic finite element analysis of the crack-tip field in a WC-Co alloy was performed to achieve a detailed understanding of ductile fracture in a Co-phase. A model in which a Co-phase was embedded at the crack tip in an elastic solid was employed, and Gurson's constitutive equations for porous plastic material were used for the Co-phase in order to take into account the nucleation and growth of the microvoids. The effects of the shape of the Co-phase and the stress state (plane stress or plane strain) on the distributions of hoop stress, hydrostatic stress and microvoid volume fraction were discussed using the computational results. The process of ductile fracture under constraints of deformation was also discussed.

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The fracture process of whisker-reinforced aluminum alloys is studied. First, tensile tests are carried out on specimens of various orientations. Dimple fracture occurs at the edge of the whisker fiber due to the stress concentration. It is also found that delamination occurs at the whisker matrix interface in the T-specimen. Then the fracture process is simulated by FEM. For the constitutive equation, Gurson's yield fuction is used. Void volume fraction is used as a fracture parameter and a conventional fracture analysis is carried out. Numerical results qualitatively agree with those of experiments. The delamination effect between the base metal and the whisker fiber is considered. It is concluded that the effect of the delamination is very small before fracture of the specimen.

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A simple technique was developed to introduce fatigue precrack to a through-notched compact specimen of Si₃N₄ and SiC. First, a compressive load was applied to introduce damage at the notch tip. Nucleation of damage can be easily detected by a pop-in sound. Then, a fatigue crack was introduced by cyclic tensile loading. By using precracked specimens, usefulness was confirmed for fracture toughness, fatigue crack growth, and stress corrosion cracking tests. In both cases, it was found that fracture mechanics characteristics are successfully evaluated when the fatigue crack increment from the notch tip was larger than the notch tip radius.

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Microcircular holes made in electrodeposited copper foil resulted in profound improvement in the copper electroplating method of stress analysis with respect to detection of the principal stress amplitudes in the machine parts under biaxial stress conditions. In this paper, with the goal of wide application of this idea, a practical method is presented which is applicable when the directions and locations of combined acting loads are unknown. The accuracy of this method is also ascertained by the combined load tests of cyclic torsion and plane bending to the plate element.

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Although the copper electroplating method of stress analysis can only detect the shearing stress amplitude, microcircular holes made in electrodeposited copper foil enable separation and measurement of the first and second princical stresses with biaxial stress conditions of a negative biaxial stress ratio. In this paper, developing the above idea, a method of detecting both principal stresses at the stress-concentrated location with a positive biaxial stress ratio is presented. The accuracy of this method is ascertained by examining the stress state near the hole in a plate under uniaxial tension and that at the bottom of a chircular groove in a shaft under bending.

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An alternative form of the modified kinematic hardening creep constitutive model is developed for a precise description of anisotropic creep behavior of type 316 stainless steel under repeated multiaxial nonproportional loading conditions. This model is characterized by the unified-type constitutive structure and the auxiliary creep hardening rule. The auxiliary hardening rule is formulated using the memory surface in which the isotropic creep hardening is suppressed and the kinematic type promoted. Different definitions of the memory surface and its evolution equations are proposed based on the same concept as in the previous study. The validity of the creep model is shown by the comparison between the predicted and the typical experimental results on repeated multiaxial nonproportional creep. Also shown are the simulated results of the purely isotropic-hardening model and the purely kinematic-hardening model which are derived as special cases of the present model.

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The stress distributions induced by an applied stress σ₀ in five bonded plate specimens (silicon nitride to copper) with different thicknesses were calculated by using the three-dimensional (3-D) finite element method (FEM) stress analysis and the results were compared with those of the two-dimensional (2-D) FEM stress analysis. Along the center line perpendicular to the interface on the surface of the specimen, a maximum stress of approximately 1.3σ₀ calculated with the 3-D FEM appeared in the interfacial region in silicon nitride, with a minimum stress of 0.9σ₀ appearing in copper ; these values were almost independent of the thickness of the specimen. On the other hand, the 2-D FEM predicted only slight change in the stress in the interfacial region, giving a value close to the applied stress σ₀. As the thickness of the specimen decreased, the maximum stress decreased more rapidly, and the stress value agreed more closely with the value calculated by the 2-D FEM at a point farther from the interface.

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It is suggested that strain aging is one of the important factors for deriving the inelastic constitutive equation of metal materials used in structure. To investigate the effect of aging on the flow stress level in plastic deformation, under uniaxial loading using SUS316 stainless steel, which is a typical metal used in structure, and A7075-T6 aluminum-alloy, which shows a strong strain aging, the authors analyzed the intensity of temporary hardening after stress relaxation and calculated the behavior. The intensity behaves as a function of prestraining history, and calculated results agree with experimental responses.

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In the present paper, the plane problem for three-phase materials formed from three isotropic homogeneous wedges with arbitrary angles is analyzed. In particular, the eigenequation for the three-phase bonded structure analytically derived in the previous paper is used for investigating the effect of the elastic property for intermediate material on the order of singularity in the stress field near the apex. For the several cases in which wedge angles ψ₁, ψ₂, ψ₃ are equal and those in which ψ₁+ψ₃ and ψ₂ are constant, the order of singularity in the stress field for different material combinations and that for different wedge angles of regions 1 and 3 are studied in detail.

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This paper deals with the singular stress field near the tip of a V-shaped single-edged notch in an infinite strip under tension and in-plane bending. The order of the stress singularity is dependent on the deformation mode. For mode I deformation, the stress singularity is 1/γ^1-λ₁, and for mode II deformation, it is 1/γ^1-λ₂. Thus, the stress field around the singular point must be described in terms of two constants K_{I, λ1} and K_{II, λ2}. In this study, the parameters K_{I, λ1} and K_{II, λ2} are calculated using the body force method. In the numerical analysis, the singularities of stress field are characterized by introducing the proper basic density functions of the body forces. The use of the basic density functions enables one to obtain accurate solutions.

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The recovery stress associated with the R-phase transformation in TiNi shape memory alloy was investigated experimentally with respect to constant maximum strain and residual strain. The results are summarized as follows. (1) The lower the shape memory processing temperature, the larger the recovery stress under constant maximum strain. (2) The higher the shape memory processing temperature, the larger the recovery stress under constant residual strain. If the reverse transformation based on partial pseudoelasticity occurs in the unloading process, the recovery stress decreases. (3) The recovery stress in the heating process increases along the reverse transformation line on the stress-temperature plane. (4) The recovery stress under constant maximum strain is larger than that under constant residual strain.

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The thermal stress during pulling and the residual stress after pulling in a single crystal grown by the liquid-encapsulated Czochralski (LEC) technique are analyzed by a new method which changes the numerical solution of temperature to a theoretical one through the use of the least squares method. The method is proven to be valid. The thermal effect of the liquid encapsulant on the maximum stress which the crystal undergoes during the growth process is investigated. It is found that the cross-sectional pattern of a total of twelve resolved shear stresses and the resolved shear stress direction pattern obtained from the maximum stress agree qualitatively with the dislocation density and array patterns.

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Unsteady thermal stresses in a plate made of functionally gradient material were discussed. Firstly, the new analytical method of one-dimensional unsteady heat transfer problem for heterogeneous materials was proposed. This method was performed with proper displacement of variables, Laplace transform and the perturbation method. Secondly, the accuracy of this method was examined for the functionally gradient material composed of ZrO₂ and Ti-6Al-4V. Finally, unsteady thermal stresses were calculated for the mechanical boundary condition that the elongation and bending were free.

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Unsteady thermal stresses in a functionally gradient material plate were discussed. Firstly, a one-dimensional unsteady heat transfer problem for heterogeneous materials was analyzed with the newly proposed method using the proper transformation of variable, the Laplace transformation and the perturbation method. The one-cycle temperature boundary condition was asumed ; both surfaces of the plate were heated from the initial state of room temperature, and after the steady state was reached, both surfaces were cooled until the initial state was attained. During the cooling process, large tensile stresses appeared on the ceramic surface at the earlier stage, but the damage region was restricted to the thin layer on the surface. The influence of the mechanical boundary conditions was also discussed.

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A SQUID (superconducting quantum interference device) apparatus for nondestructive inspection, which is a highly sensitive magnetic sensor, is used to measure the thermal aging degradation in a duplex stainless steel and sensitization of stress corrosion cracking in an austenitic stainless steel. The thermal aging degradation and sensitization of stress corrosion cracking were successfully detected from the magnetic characterization measurements. Also a method using a ferrofluid to observed material damage is developed. The method can be used to obtain the change of magnetic domains with thermal aging and sensitization in these steels. Magnetic domains in the duplex stainless steel are subdivided during thermal aging, while magnetic phases precipitate near grain boundaries of the austenitic stainless steel during heat treatment for the sensitization.

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A compact of TiB₂ was fabricated by sintering powder TiB₂ with less sinterability by use of a high pressure technique. Densification of the sintered compact was made at a pressure of 5.4 GPa and temperatures up to 1600°C for 5 hours. The sinterability was estimated from mechanical and electrical properties. The properties of compacts were improved by increasing sintering temperature, and the results were obtained in the sample sintered at 1600°C. The bulk density was 4.47g·cm^-3, i.e. 99% of the theoretical density. The Vickers microhardness and the electrical resistivity were 2462 and 10.6μΩ-cm, respectively. These values were aproximately equal to those of a single crystal.

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The bonding of ceramics-metal is a useful practical method to take advantage of ceramics properties. However, there are some serious problems, one of which is the thermal stress concentration occurring near the edge of the interface bonding two materials with different thermal expansion coefficients. In this paper, changing the strength of the bonded structure by modifying the shape of metal, which was easy to manufacture, was evaluated by tensile testing. The change of strength of the bonded structure on application of a heat cycle was also evaluated. In addition, the thermoelastic-plastic analysis of residual thermal stresses near the edge of the interface was conducted using the finite-element method (FEM). The contents in this paper were summarized as follows. The bonding strength of Si₃N₄ and Ni can be increased by modifying the edge angle of the metal, and the strength of the joint with an edge angle of 45° was about three times that of 90°. In addition, the result of FEM analysis supported the experimental result of bonding strength. The bonding strength for joints undergoing the heat cycle dropped remarkably with alteration of the thermal stress between expansion and contraction.

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The strength of unidirectionally reinforced carbon/epoxy composites (CFRP) subjected to the compressive impact load was measured by the Split Hopkinson Pressure Bar Method (S. H. P. B. M), then the effect of fiber orientation on the compressive impact strength was investigated. Stress of the specimen, caused by multiple reflected stress waves at its ends in contact with the incident bar and transmitter, was analysed based on one-dimensional stress wave theory. The resulting formulation can be used to evaluate either the linear or nonlinear stress-strain relation. The strength of a specimen of zero-degree fiber is the greatest. The strain of a specimen of 45-degree fiber is the largest. A split fracture parallel to the fiber appeared in the specimen of zero-degree fiber. Inclination of the fracture surface of specimens of 30-, 45- and 60- degree fiber is in alignment with the fiber orientation. Tat of 90 degrees is not. The impact strength is about 80 MPa larger than the static strength. In contrast, the dynamic elongation is smaller than the static elongation.

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This paper is concerned with a compression experiment in the case of equal eccentric at upper and lower ends of carbon steel square pipes, each with a circular hole in a short column range, supported by a spherical seat. An empirical formula for calculating eccentric compressive buckling stress σ_che of the carbon steel square pipes with a circular hole is presented as follows ; σ_che/σ_cr=(K₀/K)/{1+2(e/c)} where K and K₀ = coefficients of axial compressive buckling stress on carbon steel square pipes without and with a cicular hole, e = eccentricity, c = distance between walls. Consideration has been given to the diagram which is the combinatison of the analysis based on the energy method with the experimental results. The measurement results show that this diagram represents good design data and is in good agreement with the results obtained experimentally for a short column range.

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There is a growing problem in solid mechanics related to electromagnetic devices of large magnetic forces such as linear motor cars, MHD systems and fusion reactors. In order to analyze the electromagnetic field, a FEM-BEM coupling method(Combination method) was proposed and has been prooved to be a promising method. However, there remains such problems that the continuity as well as compatibility on the FEM-BEM boundary are exactly satisfied or not, and that the relative advantage and disadvantage of the method are not clarified. The aim of this study is to present the formulation for applying a combination method to closed space problems using a reduced matrix and examin the compatibility of both elements by using a modified 0-1 degree boundary element. The results show the effectiveness of this method in the analysis of 2D static magnetic field.

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Stress-induced martensitic transformation was applied to produce a monolithic, magnetic-functionally gradient material (magnetic-FGM). Wedge-shaped plates of SUS304 austenitic stainless steel with inclination angles of 1 and 3 degrees were deformed in tension at room temperature. A less slanted specimen showed strain distribution graded nearly linearly along the tensile axis, which provided a good gradient of magnetic property resulting from the formation of ferro-magnetic α' martensite. A specimen with an inclination angle of 3 degrees, however, exhibited more inhomogeneity of plastic deformation which is unsuitable for the magnetic-FGM. A theoretical evaluation for the distributions of strain and saturation magnetization was conducted using a simple model, which turned out to be in good accordance with the experimental results. Other processing methods and engineering applications of the magnetic-FGM were also discussed.

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Slurry weae behavior determined using a liquid jet containing Yellow River sand was compared with that containing silica sand with an average grain diameter of 150μm. Sand contained in tap water was 37 kg/m³, which is equivalent to the average value of the Yellow River over a year. The mass loss rates or MDPR of various test materials are in proportion to the n-th power of jet velocity ; n is 3.0 for silica sand and 2.5 for Yellow River sand. Slurry wear resistances of various kind of steel (reciprocal of mass loss rate or MDPR) have a linear relationship with (V)^-n×(HV²/E), regardless of the type of sand.

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We reinvestigate the optimization problem of a clamped-clamped column under buckling loads which was previously dealt with by Tadjbakhsh & Keller and Olhoff & Rasmussen. Both single and bimodal formulations are used in investigating the behavior of the optimum eigenvalues with respect to the minimum constraint of cross-sectional area. The optimum column under the single modal formulation is defined. The bimodal optimum column together with two mutually symmetrical eigenfunctions is obtained. Furthermore, on the basis of the obtained mutually symmetrical eigenfunctions, we deduce the 1st-and the 2nd-order optimum eigenfunctions which are orthogonal, having symmetrical and an antisymmetrical configuration, respectively. Finally, from Keller's solution, we derive analytical solutions of several critical eigenfunction for columns under the single modal formulation.

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X-ray stress measurement is a very useful method to evaluate the residual stress in polycrystalline materials. In the practical measurements, many conditions, such as the diffraction plane and scanning method of the detector, must be determined. These conditions are totally dependent on the purpose of measurements, and it requires much technical knowledge to set the conditions properly. Thus, an expert system for X-ray stress measurement was developed in the present paper, which can be utilized to determine the measuring conditions. The residual stress of the low carbon steel was measured employing the conditions suggested by the system. The experimental results were quite satisfactory, and the residual stress was evaluated reasonably. It can be said that the present system will help users to determine the measuring conditions for the various purposes of studies.

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This paper describes the development of a three-dimensional automatic FEM (Finite Element Method) mesh generation system using the shape recognition technique. In this system a solid model is analyzed, and cubes are put together to construct a similar model to it in human thinking way, which is expressed by membership functions defined in fuzzy set theory. Then, hexahedral meshes are generated by mapping cubes into the solid model. The major advantages are described as follows. (1) A solid model is divided into only hexahedral meshes by single input data, that is mesh size. (2) It takes only about five minutes to divide a solid model into thousands of hexahedral meshes using an engineering work station. Hence, the system can be applied for practical use. The performance of the system is demonstrated through automatic mesh generation for some mechanical parts.

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A certain geometrical relation holds for a given number of structural points before, during and after deformation of a structure when the structure is designed to realize homologous deformation. The realization of such a homologous deformation is effective to enhance precise function of the structure and to mitigate laborious toil of structural control. This paper presents a new formulation to determine the structural parameters for realizing the homologous deformation. The structure is discretized by finite elements, and a modified stiffness matrix in rectangular form is derived based on the constraint matrix describing the homologous deformation. The Moore-Penrose generalized inverse is employed to treat the rectangular matrix. The proposed method is verified valid by numerical examples concerned with a planar lattice structure.

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A fracture callus changes the structural style by affecting the dynamic loading condition during the fracture healing process. The purpose of this research is to grasp the behaviour of the intelligent material system during the process. In this paper, the stress wave propagation behaviour of the fracture callus is investigated using finite-element analysis to estimate the form of the structural change. It was concluded from the numerical result that the structural changes of the fracture callus relate closely to the difference in mechanical impedances between the constitutive materials in the callus. The result was experimentally verified by means of the fracture model using the femur of a rat.

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This study aims to develop an image processing system for the estimation of trabecular strength and to investigate the relationship between the loads and the trabeculae in the femoral head. The trabecular system is a useful source of knowledge for the mechanical environment of bone which is important in using orthopedic treatment. In this paper, the distribution of principal stress obtained by the finite-element model based on Pauwels' theory is compared with that of trabecular strength estimated using the image processing technique. It is found that the result of finite-element method is similar to the configuration of trabeculae in both magnitude and direction. This result shows that unknown applied loads to bone may be estimated using the inverse finite-element method.

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