Plain fatigue and fretting fatigue tests were carried out using two types of sintered high-strength steel. The ratio of tensile strength σ_B and plain fatigue strengthσ_w, σ_w/σ_B, for sintered steel was rather low compared to melted structural steel. The ratio of plain fatigue strength σ_w and fretting fatigue strengthσ_wf, σ_wf/26σ_w, in sintered steel was significantly high compared to melted steel. The superior fretting fatigue property of sintered steel compared to melted steel is a result of its lower tangential force coefficient. The tangential force in sintered steel is induced by the lubricating effect of wear particles, which are trapped inside pores on the surface.

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We carried out internal pressure tests on a large number of thin-wall cylinders and CT tests of austempered ductile iron (ADI). As a result of internal pressure tests, we observed that the fatigue life distribution at the low-pressure level was divided into two groups : a short-life group below l x 10₆ cycles and a long-life group fracturing at near l x 10₇ cycles. At the high-pressure level and in the short-life group of the low-pressure level, the fatigue crack origins were the casting defects, and the √area distribution of these was fitted with the extreme value distribution. On the other hand, it was observed that the crack growth rate obeyed the Paris law in CT tests. Thus we explained the form of the fatigue life distribution using the √area distribution of the fatigue crack origins and the crack growth rate based on the Paris law.

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A chart for predicting thermal fatigue crack propagation behavior of semiconductor-chip-bonding solder layers is obtained by combining a damage model and a closed-form strain solution of chip-bonding layers. The predicted results show good agreement with experimental results. By using this chart, important chip-bonding structure design factors, such as the effects of bonding layer yield stress and bonded member compliance on the crack propagation behavior, are easily obtained. From this chart it is seen that the crack propagation rate of the first stage decreases when the bonded member compliance is increased.

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This paper describes the stress intensity factor for a semicircular surface crack embedded in a finite plate of Si single crystal, in consideration of anisotropy caused by the crystallographic texture. The correction factor F_I of the stress intensity factor was calculated by means of the 3D finite-element method (FEM). Crystal orientation influences the F_I value, especially at the deep points of the crack. At the deepest point of the crack, the F_I value varies with a period of 90°against the rotational angle, φ. The value of F_I for Si single crystal agrees with that for an isotropic body when the loading direction is the direction of crystal principal. The F_I value of Si single crystal, however, differs from that of the isotropic body when the loading direction does not agree with the crystal principal direction.

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The influence of the lattice orientation difference on the deformation and stress fields of the crack located at the grain boundary is considered by means of the finite-element method in consideration of finite deformation and finite lattice rotation. The plane strain calculations for a fcc crystal subjected to mode I loading are performed on the basis of the crystalline plasticity described by a planar three-slip model. For the crack-tip shapes and the dominant deformation modes on slip systems, some results of all the cases analysed here are in qualitative agreement with the earlier analytical and numerical solutions. Our results indicate that the lattice orientation difference exerts great influences on the shear stress along the grain boundary, which is related to grain-boundary sliding, while the normal stress along the grain boundary, which may induce cleavage fracture, is virtually insensitive to it.

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Analysis of the fracture surface using rotating bending fatigue tests was conducted on austempered ductile iron (ADI) and ferritic ductile iron (FDI) for comparison purposes. The difference in the configuration of crack propagation of ADI and FDI was clarified. Propagation of the surface crack progresses, while the crack initiated in graphite repeats cohesion. However, in ADI, the propagating crack expanding on the fracture surface is extended rather than controlled by graphite. On the other hand, in FDI, since the graphite is equivalent to a porous material, the Crack grows as in a complex surface and finally fractures. In relation to the fracture surface rate obtained from information on the fracture surface and cyclic life, ADI exhibited a characteristic of a double bend resembling the knee of an S-N curve, and the surface fracture growth rate in the neighborhood of the fatigue limit was about 88%.

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The effect of tempering temperature on crack surface morphology and crack growth rate under stress corrosion cracking (SCC) and fatigue interaction was investigated using 12CrMo stainless steel. The transition behavior of the cracking morphology showed various types depending on the susceptibility of the material to SCC. The interaction between cycle-dependent cracking and time-dependent cracking occurred only when the metallurgical crack path was the same for each cracking mode. The linear accumulation law was found to be appropriate only for this case.

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The relationship between fatigue crack propagation properties and thickness of films such as oxide film and passive film was analyzed. The data of fatigue crack propagation properties employed were obtained for carbon, low-alloy, high-strength and stainless steels in air at test temperatures between -25 and 550°C and in 3%NaCl aqueous solution, avoiding crack closure. When the relationship of fatigue crack propagation rate, da/dN, to effective stress intensity factor range, ΔK_eff, was expressed by da/dN=C^*{(ΔK_eff/E)^m-(ΔK_{eff, th}/E)^m}=C^*(ΔK_eff/E)^m-(da/dN)^*…(A) where C^* and m were constants, E was Young's modulus and ΔK_{eff, th} was the threshold, the following three equations were obtained : C^*=1.3×10⁵ζ^0.5…(B) (da/dN)^*=ζ…(C) ΔK_{eff, th}/E=6.7×10^-4η^0.25…(D) Here, ζ was the thickness of films formed at the crack tip for each loading cycling, which was estimated from oxidation behavior on the alumina-polished surface in air at elevated temperatures and from corrosion behavior on the bare surface in 3%NaCl aqueous solution. The films were the oxide film in air at elevated temperature and the water-adsorbed and passivated films in 3%NaCl aqueous solution. η was the film thickness measured on the fracture surface at the threshold level. Substituting Eqs. (B) and (C) into Eq. (A), and Eqs. (B) and (D) into Eq. (A), two predictions of fatigue crack propagation were obtained. Both predictions were in good agreement with the experimental data.

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The initial propagation behavior of small fatigue cracks initiated at a sharp notch as well as at the tip of a pre-crack has been investigated under constant push-pull loading with the stress ratio R -0 in sheet specimens of a commercially pure titanium. Growth rates of small fatigue craks (<0. 4 mm) varied over a wide range under the influence of the microstructure. In the case of a notched specimen, steady growth of a fatigue crack was preceded by initiation, early growth and joining of multiple cracks near the notch root. In the case of a pre-cracked specimen, steady growth was preceded by early growth of the pre-crack, initial craking at different sites remote from the growing crack, and their joints. Fractographic observation supports the above explanation of the behavior.

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The influence of microstructures on the growth behavior of small cracks is investigated using three kinds of heat-treated squeeze-cast aluminum alloys. A eutectic silicon particle becomes the initiation site for the crack and has a blocking effect upon crack growth. Although the growth behavior of the small crack is strongly influenced by microstructures in the early stage of crack propagation, the influence of microstructures decreases with increase in the crack length. The critical length at which the marked influence of microstructures is observed is about 200μm, which is nearly 8 times the dendrite arm spacing, regardless of heat treatment. Mean values of the crack growth rate in the growth process affected by microstructures, however, may be extrapolated from the crack growth rate in the range where the growth behavior is mainly controlled by a mechanical parameter alone.

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The general solutions for an elliptical crack in an infinite solid, subjected to arbitrary shear tractions on the crack surfaces were rederived. First, their applicabilities were demonstrated deriving the closed-form analytical solutions for an elliptical crack subjected to constant shear tractions, and for an elliptical crack subjected to torsion. Next, the present analytical solutions were used in the alternating method for solving multiple elliptical cracks subjected to arbitrary shear tractions. Numerical demonstrations are also given for interaction problems of several types.

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This paper deals with the axisymmetric torsion problem of an infinite hollow cylinder with externally and internally circumferential cracks lying in different planes. Expressing the stress component along the crack plane as an appropriate series, the problem is reduced to the solution of an infinite system of simultaneous equations. Numerical results are presented in order to illustrate the effect of the distance between two crack planes on the stress distributions at the crack tips and stress intensity factors.

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In order to investigate the corrosion fatigue strength and fracture mechanism of ceramic-sprayed steel, rotating bending fatigue tests have been conducted at room temperature in 3% NaCl solution using specimens of medium carbon steel (S45C) with sprayed coating layers of Ni-5%Al (undercoating) and chromia (topcoating). Corrosion fatigue strength of ceramic-sprayed steel was better than that of substrate steel. However, the coated layers contained many pores through which NaCl solution was supplied from the specimen surface to the substrate. Corrosion pits were initiated at the interface between the undercoating and substrate. Subsequently, cracks initiated from the pits and grew into the substrate. Tests were conducted on specimens whose pores were closed by shielding treatment. In this case, NaCl solution was supplied to the substrate through cracks initiated in the topcoating layer. The shielding treatment was effective under low stress levels where fatigue life was more than 10⁷ cycles, while it had no effect in improving corrosion fatigue strength under higher stress levels because of the great number of cracks initiated in the topcoating layer.

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Crack opening and closing behavior was analyzed on an external circular crack whose peripheral faces were heated axisymmetrically with constant heat flux. At the beginning of heating, crack faces start to contact at the peripheral region. Then, the region spreads inwards. The near-tip crack faces, on the other hand, open from the beginning of heating and the opening displacement increases with time for a certain duration. The displacement, however, tends to decrease after attaining the maximum until the crack closes completely. Correspondingly, the stress intensity factor increases with time and attains its maximum in the course of heating. Using externally cracked glass cylinders heated by a CO₂ laser beam, crack opening displacements were measured experimentally by the optical interference method. The measured displacements were consistent with the FEM analysis.

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The application of structural ceramics to gas turbine components is currently expected as a means of improving peformance. Due to its low toughness, however, an assessment of the resistance against damage caused by foreign objects is requied. In order to investigate the damage caused by impact from a projectile, we tentatively fabricate a particle impact test rig, which is a gas-gun-type accelerator operated with air or helium gas. It can accelerate projectiles up to a velocity that is almost equal to the speed of the tip of a gas tubine moving-blade. In this study, the single -particle fracture test for four kinds of materials was made on this test rig. Two types of fracture modes were obsreved. One is the fracture with cracks propagating conically from the contact point and the other is that with the cracks propagating radially from the opposite side of the impact location. The critical velocity of each fracture mode is explained as a function of projectile size, target thickness and mechanical properties such as flexural strength or fracture toughness. Furthermore, from the viewpoint of practical operation, the influence of compressive stress field on critical velocity is discussed.

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In electronic devices and magnetic disks, thin films are used in the form of films coated on substrates. In order to improve their mechanical reliability, it is necessary to evaluate the fracture strength of a thin film which is coated on a substrate. However, methods for evaluating it have not yet been established. In this paper, a method is proposed for evaluating fracture strength of thin films by means of indentation with a small spherical indenter, and usefulness of the method was investigated. A SiO₂ film coated on a stainless steel SUS440C plate by ion beam sputtering was indented with a SiC spherical indenter. The fracture strength of the film was evaluated by combining the ring crack initiation load obtained experimentally and the result of finite-element method (FEM) analysis.

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Ultrasonic testing using a normal incident longitudinal wave is conducted for sizing a three-dimensional closed crack. The crack results from fatigue and exists vertically on the back wall of the inspected plate. The echo height of the first back-wall echo is measured at several points on the plate surface under a no-load condition. The shape and size of the crack and the stress closing the crack are determined by solving the inverse problem which compares the measured distribution of the echo height with a theoretical one. It is shown that the crack shape and size are accurately evaluated independent of the stress ratio on the crack during fatigue. It is also proven nondestructively that the stress closing the crack is higher in the shallow part of the crack than in the deep part.

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In electronic devices, magnetic disks and micromechanical systems, thin films are widely used. Improvement of their mechanical reliability requires invetigations of methods for evaluating fracure strength of thin films coated on substrates. In order to develop a method for evaluation of fracture strength by means of indentation with a small spherical indenter, an elasto-plastic finite-element stress analysis for the case of an elastic film and a plastic substrate is carried out in this paper. The analysis shows that radial tensile stress or occurs in the film beyond the contact area. An approximate equation for the distribution of σ_r is derived, which is useful for evaluation of the fracture strength.

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In electronic devices, magnetic disks and micromechanical systems, thin films coated on substrates are widely used. In order to develop a method for evaluation of their fracture strengths by means of indentation by a small spherical indenter, it is necessary to study the stress distribution in a film subjected to such indentation. In this paper, an approximate expression for the elastic stress distribution is derived for the case where the film thickness is much smaller than the radius of the contact area. A finite-element analysis is also carried out to examine the accuracy of the approximate expression.

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In this paper, we propose a general higher-order 3-dimensional refined theory of plane stress problems with consideration of transverse components, which are neglected in classical 2-dimensional elasticity solutions. The theory is one of the mixed-type theories based upon the assumption of stress and displacement components. In this study, we consider not only in-plane (symmetric) but also out-of-plane (antisymmetric) behavior of plates under arbitrarily distributed loads on the edge. Other theories and analytical formulas proposed by many authors are reviewed with consideration of their interrelations.

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Abstract-In this paper, we consider the singular stress of G-10CR glass-epoxy laminates with a broken layer under tension at low temperatures. The composite material in generalized plane strain is assumed. Fourier transforms are used to formulate the problem in terms of a singular integral equation. The order of stress singularity around the tip of a crack which is normal to and ends at the interface between orthotropic elastic materials is obtained. The singular integral equation is solved by means of the Gauss-Jacobi integration formula. Numerical results for the stress intensity factor and the order of stress singularity at different temperatures are obtained and are presented in graphical form.

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Generally, the boundary element method (BEM) for thin elastic plate bending analysis uses two different types of integral equations for displacement and rotation. However, there is a different type of approach, based on a direct method, using only integral equations for displacement (single integral equation method). In this method, hyper-singularities do not arise, because there is no need to use integral equations for rotation. In the present paper, the regularizing operation using the rigid rotation mode, as suggested in the first report, is applied to the single integral equation method. Through the numerical results of a square plate under several boundary conditions, it is shown that results obtained using this method are more accurate in comparison with the without regularization.

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The paper deals with the inverse problem of identifying the elastic constants of anisotropic elastic materials. To solve the problem, the extended Kalman filter algorithm is combined with the finite element method. The effectiveness of the method is demonstrated by two simulations, I and II. The isotropic elastic constants are identified in simulation I. The orthotropic elastic constants are identified in simulation II. At the beginning of the identification processes, the materials are assumed to be orthotropic in simulation I and isotropic in simulation II. It was confirmed through the two simulations that the material constants were identified correctly.

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Supersaturated Al-10 and 15 mol% Li solid solutions were prepared by means of heat treatments under high pressure and high temperature, and the variations of elastic modulus, electrical resistivity and micro-Vicker's hardness in those solid solutions during isochronal ageing up to 673 K were investigated. The maximum shear modulus was observed during the precipitation of the δ' phase at 453 K ageing. The difference in the decomposition behavior of several specimens obtained by high-pressure solid solutioning and by conventional one is discussed based on the results of elastic modulus measurements.

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It is the purpose of the investigation to clarify mechanisms of facial expressions and formation of wrinkles on a face with a hyper elastic skin. In the present study, parameters of mechanical properties are identified by using the results of both in vivo experiments and calculation by the finite-element method (FEM). We also carried out in vitro experiments for formation of wrinkles with a rabbit skin and conducted analysis of wrinkles, in which formulations of hyper elasticity and large deformation for a skin-fat composite were incrementally made as buckling and post-buckling problems, using the same model of the experiments. Furthermore, we carried out in vivo experiments and FEM analysis of wrinkles in the forehead skin of a human being. The validity of the analysis method proposed in this study and the usefulness of the developed FEM programs are demonstrated by comparison with the series of experimental results.

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The thermocoupled flow localization of plane-strain compression blocks under high strain rate has been investigated. A phenomenological thermo-elasto-viscoplastic constitutive law accounting for the strain rate history dependence is developed to describe the material behavior under high strain rate with and without abrupt strain rate change. An inertial force is also considered in dealing with the deformation behavior at dynamic loading through the principle of virtual work. Results of the finite element analysis based on the proposed constitutive model show that the effect of inertial force causes the wiggles of the nominal stress versus nominal strain and significant retardation of shear band development. Flow localization starts at central part of a block and manifests itself as the viscoplastic strain development emanating from the inhomogeneity. With an abrupt change of the strain rate, the positive/negative strain rate history dependence causes shear band development to retard/accelerate.Plasticity,

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Composite pipes with structurally unsymmetric laminated configurations (SULC pipes) have been proposed by the authors. The deformation of a cantilevered SULC pipe under bending and twisting loads applied at its tip was analyzed, and it was shown that the SULC pipe has a torsionfree loading axis (TFLA), that is, a transverse load applied along this axis does not cause twist deformation, and such axis is concluded to be the elastic principal axis for the pipe. In this study, it is found the SULC pipe has a deflection-free loading axis (DFLA), that is, a transverse load applied along this axis does not cause deflection. This axis is different from the geometric principal axis of the pipe, and is a function of the laminate configuration. The relationship between positions of TFLA, DFLA, and the geometric principal axis is obtained. Structures made of isotropic materials generally do not have such DFLA. The relationship between the deflection curve of the pipe and loading condition is analyzed. The analytical results show good agreement with the experimental results. Coupling deformation produced by isotropic beams with unsymmetric elastic properties on the cross section is analyzed through comparison with the coupling deformation of the SULC pipes.

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Upsetting tests of sintered aluminium and iron powder preforms are carried out using a computer-controlled high-speed press which can generate a constant strain rate throughout an upsetting process. The effect of strain rate on the flow stress and the density change of these sintered metals are experimentally examined under various constant strain rates from 0.001 to 50/s. The effect of strain rate on the material constants N, a and b which are included in the plasticity theory of porous materials presented by Oyane and Shima is also discussed. Experimental results show that the strain rate hardly affects either the density change or the material constants in the Oyane and Shima plasticity theory, but that the flow stress of sintered metal increases with increasing strain rate. Such strain-rate dependence of the flow stress of sintered metals is estimated to result from that of the matrix itself, i.e., the strain rate sensitivity of pore-free aluminium and iron.

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Plastic strain distributions obtained from the hardness number distribution at the net section have been compared with those calculated using the finite element method. Notched bars with a U-shaped circumferential notch were made of austenitic stainless steel (SUS), Ni-Cr-Mo steel (SNCM)and low-carbon steel (S20C). In the deformation range up to the maximum tensile load P_max, the strain distribution obtained using the two methods agreed well for all notch radii and materials employed. In the deformation range beyond P_max of netched bars of SUS, the two strain distributions agreed well for high notch sharpness, while for low notch sharpness, the difference between the two strain distributions increased with increasing deformation and with initial notch radius. For SNCM, the two strain distributions agreed well beyond P_max. Approximately the same strain distribution was produced prior to P_max, in spite of the distinct difference in mechanical properties and notch strength ratio.

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Metal strips (mechanical spring) and multipurpose plastics are widely used as flexible linkage devices in engineering designs. The folding of thin elastic sheets (paper, sheet metal, cloth, carpeting, rubber, etc. ) is extremely important in manufacturing processes. In such elastic elements, a fairly large deflection characteristic is observed, but does not exceed the elastic limit of the materials. This property is of both analytical and technological interest. It is indispensable to analyze the large deflection behavior to achieve high accuracy and reliability of the mechanical components. In this report, we investigate the nonlinear large-deflection problem of a simply supported flexible beam subjected to bending moment at one edge, taking into account the effect of edge friction, and present the analytical formulae for arc length, vertical and horizontal displacements, bending moment, curvature and bending stress. Moreover, a large-flexural-bending test is performed on a thin PVC plate in order to assess the adequacy of the theoretical formulation. In addition, linear analyses are performed for comparison with large-deflection theoretical analyses. Experimental data agree very closely with theoretical results. Therefore, the nonlinear large-deflection theory proposed here is of direct relevance to the analysis and design of flexible components.

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Detecting plastic deformation area at crack tips of FRM is very important for understanding the mechanism of reinforcing matrix by fibers. Few method, however, are proposed to detect the plastic deformation inside the FRM. Recently, a scanning acoustic microscope has developed and this gives us chance to detect the plastic deformation area. In this study, several acoustic methods including a scanning acoustic microscope were examined to detect the image of it. As results, acoustic velocity change as a function of plastic strain of aluminum alloy was obtained and the change was discussed with a dislocation vibration model. The images with 50 MHz acoustic lens and 200 MHz acoustic lens were obtained and investigated in detail.

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This paper presents a method of analysis for deformation of the sheet in the space formed by guide plates. First, the formulation of deformation of the sheet is introduced using a spring-mass-beam model, Lagrange multiplier, and functions which express the configuration of guide plates. Then, the calculation results of deformation configuration and forces acting at contact points between the sheet and circular guide plates are compared with the experimental results. Furthermore, the calculation results of deformation configuration in the case of straight guide plates are shown. It is concluded that simulation using the method proposed here gives good results.

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Interlaminar fracture and breakdown of fibers in rectangular-cross-section beams made of carbon-fiber-reinforced plastic (CFRP) are investigated for the case in which the midspan of the beams, which are fixed at both ends, is bombarded by small projectiles. Interest is focused on the relationship between the internal shear stress and the failure mode of the beams. Also, the effects of projectile tip shape on damage initiation are examined. The internal shear stress is calculated by use of the computer code AUTODYN-2D by employing information included in the bending strain waves which are detected experimentally by strain gauges glued on the beam surface. The fracture of CFRP is inspected by means of an ultrasonic microscope and an optical microscope.

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In this paper, we report a numerical analysis method of mechanical behavior for three-dimensional reinforced composites on the basis of micromechanical analysis of the `unit cell', which is a small repeating unit of fiber weaving. We discussed a basic analytical model for evaluating the tensile elastic modulus in our first report. In the present paper, the strength properties of carbon/epoxy 3-D composites are estimated using an improved rigid-frame analytical model constructed of fiber-beam and matrix-beam elements. Elastic modulus, tensile strength, compressive strength and Poisson's ratio are calculated. Two weaving types of experimental fabric are prepared and tested to compare with the numerical results, and the varidity of the present analytical model is confirmed.

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In this study, the principle of structural analysis by the ε-method was investigated for three-dimensional multistoried and multispan rigid frames loaded vertically or horizontally, in cases where the bases of the columns of a rigid frame were all fixed. The ε-method is one of the slope-deflection methods and is of practical use in the structural analysis of rigid frames. An example of a digital computing program for these analysis was constructed on the basis of the ε-method and various quantities were computed through this program. The results calculated by this digital computing program are shown. Finally, these results are compared with the ones obtained by the finite-element method, and the effectiveness of applying the ε-method to the cases of three-dimensional rigid frames is confirmed.

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On October 16, 1992, a terrible explosion occurred at a VGO desulfurization unit at the Sodegaura petroleum refinement plant, Fuji Oil Co. Ten persons were killed and seven persons were seriously injured. The cause was delocking of a threaded lock ring which sustained a channel cover of a breech- lock-closure-type (BLC-type) heat exchanger. Failure analysis of the BLC-type heat exchanger was carried out. The cause and process of delocking of the lock ring were clarified.

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Resin engine covers have recently been used in some automobiles to reduce noise radiation. The sound insulation effect of resins is confirmed from experiments but the method of predicting by how much the noise will be reduced in the early design stages has not been established yet. In this paper, the finite element analysis of acoustic-structural coupling problems is introduced as the prediction method. The essential feature of the method presented here is that the material damping of a resin is considered using a set of viscoplastic constitutive equations that are determined by tensile tests at various strain rates. To demonstrate the effectiveness of the present method, some numerical examples are shown. The obtaind results suggest that the sound reduction due to a resin cover is greater than that due to an aluminium cover having the same surface density unless the frequency of sound is close to the natural frequencies of the resin cover.

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The contact stress analysis of elastic bodies is important for mechanical engineering in areas such as friction, wear and fatigue. The point-matching method is the well-known analytical model that satisfies Hertzian-contact theory. However, the point-matching method has critical problems, i.e., large amounts of computation time and memory are required as the number of cells increases. Although there have been many studies on its accuracy to date, there are a few studies on efficient processing of the point-matching method. This paper proposes an efficient discretization method for the contact region to accelerate processing time and save memory space in the point-matching method

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This paper is concerned with an asymmetric mixed boundary-value problem of an elastic half-space adhered by a rigid punch under shear stress. The behaviour of the adhesive layer is approximated by a combination of tension and shear springs. The normal and shear stresses on the adhesive region of the half-space are expressed by Jacobian polynomials. The problem is reduced to the solution of an infinite system of simultaneous equations. The distributions of stress and displacement on the surface of the half-space are illustrated for various values of the adhesion. The effects of the adhesion on the stress and displacement fields are also discussed.

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If surface mounted IC packages contain absorbed moisture, the vapor pressure generated inside the package when they are heated during the reflow soldering process may cause cracking. Our earlier report described how this vapor pressure could be determined by 1-dimensional analysis of the moisture diffusion in the plastic below the chip pad. Because package cracking due to moisture absorbed in the chip bonding paste has recently elicited of wide interest, we performed a 2-dimensional analysis of moisture diffusion in the plastic and in the paste. Using the method proposed in a previous report, we evaluated the strength of the plastic according to three types of models of the cracking mechanism. The present analysis investigates how package cracking is influenced by moisture absorbed into the paste.

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Vibratory cavitation erosion tests of carbon steel were conducted using two half-test-pieces in order to directly observe the growth processes of eroded holes on the cross section. The profiles of the eroded surfaces were digitized by tracing with a digitizer and were subsequently analyzed by a microcomputer. It is found that the surface is not uniformly eroded inward, and large holes are formed through a repeated cycle of rapid erosion and rest. This is because a large number of eroded cracks are generated and propagate further inward on the ferrite structure, resulting in the detachment of large particles.

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The fiber orientation angle has an important effect on flexural rigidities and buckling values of CFRP symmetric laminated plates, and this angle is one of the design variables of CFRP. However, it is hard to determine its correct value in the case of designing CFRP symmetric laminated plates having a specific buckling value. This decision becomes, so to speak, an inverse problem. This paper presents an application of a neural network to the buckling design of CFRP symmetric lamineted plates, and gives the solution to this inverse problem by use of a neural network.

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A new method to quickly determine weights in a layered neural network is introduced. By making use of the relation between the input of one unit in the (k+1) th layer and the output of all the units in the K th layer, all the weights can be obtained easily provided that the number of units in at least one layer is greater than or equal to the number of teacher sets plus 1. From two examples, it is shown that calculation time required by the new method is much shorter than that of back propagation method.

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Smart structures which have the ability to detect defects by themselves and which warn us of such danger have received wide attention. Smart structures with strain sensors such as piezo elastic ceramic films are especially attractive because the sensors are easily applicable to the structures in operution. Studies on the brain of smart structures with the strain sensors, however, have not been conducted. Recently, a back propagation model, a kind of neural network, has been the reported to be effective for an inverse problem. In this study, therefore, the back propagation model was examined for use it as the brain of the smart structures with strain sensors. For the smart structures which detect fatigue cracks, of a B747 airplane several parameters such as the learning method, neuron number at the hidden layer and the position of the strain sensors were surveyed by numerical simulations.

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The stress concentration problem of round and flat bars with V-shaped notches is important especially for the test specimen used to investigate the fatigue strength of materials. Accurate stress concentration factors have been given in a recent analysis of the body force method. However, the results of the solutions have been presented in tabular form which is not suitable for engineering applications. In this paper, convenient formulas which give the stress concentration factors of better than 1% accuracy are proposed using the Neuber formula and the solution of the V-shaped notch in the semi-infinite plate.

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