In this paper an elliptical crack vertical to a bimaterial interface is considered. The solution utilizes the body force method and requires Green's functions for perfectly bonded semi-infinite bodies. The formulation leads to a system of hypersingular integral equations whose unknown is a mode I type crack opening displacement. In the numerical calculation, the unknown body force density is approximated by using fundamental density functions and polynomials. The results show that the pressent method yields smooth variations of stress intensity factors along the crack front accurately. Distributions of stress intensity factors are indicated in tables and figures with varying the shape of crack, distance from the interface, and elastic constants. It is found that the stress intensity factors are mainly controlled by the root area parameter almost independent of the crack shape.

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In order to investigate the influence of loading frequency on the fatigue strength and fracture mechanism of a high strength Al alloy, ultrasonic fatigue tests were carried out for an extruded Al alloy 7075-T 6 and the results were compared with those of rotating bending fatigue tests. Fatigue strength of ultrasonic was higher than that of rotating bending. The crack initiation and the crack growth rate in ultrasonic fatigue were delayed compared with those of rotating bending fatigue. In case of ultrasonic fatigue, the direction of crack growth changed from tensile mode to shear mode and many voids were observed on the fracture surface in shear mode growth, whereas the crack propagated in tensile mode and striations were observed in rotating bending fatigue.

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Stress relaxation behavior of symmetric angle-ply laminates of T800H/3631 at large strain and high temperature has been examined. Stress relaxation tests are performed at 100°C on plain coupon specimens of three types of angle-ply laminates: [±30]s, [±45]s, [±60]s. For each ply orientation, the stress relaxation tests are carried out at three different tensile strain levels. Stress relaxation phenomenon clearly appears in all kinds of angle-ply laminate. Just after the total strain is kept constant, the stress rapidly relaxes with time in a short period. The stress relaxation rate of the angle-ply laminates tends to almost vanish. Simulation of the stress relaxation behavior of the angle-ply laminates is performed using the classic laminated plate theory with a phenomenological viscoplasticity model for elementary plies. Good agreements between the predicted and observed results on the angle-ply laminates are obtained by taking account of the local strain recovery measured with strain gauges. It is also demonstrated that the stress relaxation response is consistent with the creep response of the same material system.

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Effects of stress ratio on the off-axis fatigue strength of a unidirectional fiber-metal laminate GFRP/Al have been studied at room temperature. Tension-tension and tension-compression fatigue tests for three kinds of stress ratio: R=0.4, 0.1 and -0.2 are performed on GFRP/Al coupon specimens with different fiber orientations in the GFRP layers: θ=0, 5, 10, 15, 20, 30, 45, 60 and 90°. Also, a fatigue damage mechanics model is formulated which considers the effect of stress ratio. It is clearly observed that the fatigue strength is affected by stress ratio for every off-axis angle. Effects of the mean stress on the fatigue strength of GFRP/Al are examined on the basis of the constant fatigue life diagrams, and those diagrams are approximately described by the linear relationships of the Goodman type. Failure morphology of specimens indicates the fatigue failure of GFRP/Al is substantially governed by the fatigue strength of GFRP for the fiber orientations θ=0∼10°, while it is done by that of Al alloy for θ=30∼90°. It is demonstrated that the proposed fatigue damage mechanics model adequately describes the effect of stress ratio on the off-axis fatigue strengths of the unidirectional fiber-metal laminate.

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In this paper, two-dimensional electro elastic analysis are performed for isotropic piezoelectric materials containing multilayered elliptical inclusions under the out-of-plane mechanical and electrical loads at infinity. General solutions are provided in terms of complex functions and several numerical examples are shown by graphical representation.

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This paper proposes a new numerical model of lead material for finite element method to predict mechanical properties of isolation and vibration control devices using lead material. Shear loading tests and tensile loading of lead material tests were carried out. Shear loading test specimen were constrained from circumferential lead part and welded steel flange on it. Cyclic stress-strain relation was given from shear loading test results. The elastic modulus and the initial yield stress were given from tensile loading tests. Loading test results of the lead dampers and the isolated rubber bearings were simulated to evaluate applicability of our model.

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A fundamental study was carried out on an application of an area detector to neutron stress measurement. A neutron image plate (NIP) was used in this experiment to obtain neutron diffraction rings of polycrystalline steel specimen. The diffraction data were stored on a NIP and were converted to digital image data. Strains were obtained from these data and were analyzed to determine stress using the cosα method. Though these stresses were different from applied stresses, they increased in proportion to applied stresses. Namely, the differences between measured and applied stresses were almost constant during loading. Based on these experimental results, two practical methods were proposed for determining exact stress using a NIP. The stresses obtained using one of these methods showed good agreement with applied stresses. From these results, it is concluded that we can obtain mean stress in materials using neutron diffraction technique with an area detector.

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To examine an influence of the reduction in specimen thickness on hydrogen induced cracking in high strength bolts steels, ASTM A 490 and S 35 C, delayed fracture tests were carried out under hydrogen environment using solid bar, thin plate and thin walled hollow specimens. Cathodic hydrogen charging was used for introducing hydrogen in the specimen under sustained load conditions. The lifetime under delayed fracture depends on the plate or wall thickness. A brittle fracture due to hydrogen still occurs in extremely thin, t=0.3 mm, plate and thin walled hollow specimen. The QC cracks in thin walled hollow specimen, still develops at the subsurface of the specimen and the origin of cracks is shifted to the center of the specimen as the specimen thickness becomes thinner. The condition for brittle fracture in delayed fracture can be evaluated by the classical Griffith criterion employing fracture stresses and QC crack lenghs. Difference of hydrogen damages caused by the difference of mechanistic conditions, would make difference of fracture lives between thick and thin specimens.

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In the present paper, the analytical treatments of dynamic behavior of multispan curved beams of nonuniform section subjected to moving loads are shown by using transfer matrix method to determine the natural frequencies and mode shapes of the curved beams and application of mode superposition technique. In the case of simple curved beam under uniform section of hinge supported at both ends, the results of the present paper are compared with the exact solutions. It was found that good agreement was achieved. Dynamic responses of single-span and multispan curved beams of nonuniform section subjected to a moving load with constant velocity are calculated by transfer matrix method, and the several numerical results are illustrated.

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SiC films were deposited on titanium substrate specimens by using a helicon-sputtering apparatus. Wear tests were carried out on the specimens using a pin-on-disk type testing machine, and the delamination behavior of the films during the tests was discussed from a viewpoint of fracture mechanics. Amorphous SiC film is formed by the sputtering, while crystalline SiC film is formed when the substrate is heated. The wear resistance of titanium is greatly enhanced by the amorphous SiC film with lower frictional coefficient and higher interfacial fracture toughness than the crystalline SiC film. The wear depth of the amorphous SiC at delamination is much deeper than that of the crystalline SiC film. In the wear test, parallel cracks are initiated perpendicular to the frictional direction before partial delamination of the film occurs, and the delamination area extends all over the wear scar with a small increase in rotation cycles. The delamination of film starts when the interfacial strain-energy release rate, G₁₂, reaches the interfacial fracture toughness, G_C12, which is decreased by the accumulation of fatigue damage during the wear cycles.

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The simultaneous damages for Stellite, SCMnH 11, TiNi shape memory alloy, and SUS 304 were studied by using a test apparatus with a combination of an ultrasonic vibratory cavitation device and a slurry jet device. The tests were carried out in slurry having a concentration of 3 mass.% at flow velocities from 5 m/s to 13 m/s. The slurry was made of tap water and silica sand. For SUS 304, the volume loss rate of the simultaneous damage is higher than that of slurry wear without cavitation. On the other hand, the volume loss rate of the simultaneous damage is lower for stellite and SCMnH 11, which is work hardened by the cavitation bubble collapse pressure, thus a deceleration phenomenon appears. The simultaneous damage has no effect for TiNi shape memory alloy which shows a phase transformation during cavitation erosion. It was concluded that work hardening by cavitation bubble collapse pressure is responsible for the deceleration phenomenon of simultaneous damage.

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The authors investigated the refined surface characteristics and fatigue strength of Nitrocarburized (N) materials treated by Electro-polishing (EP), Double Shot Peening (DSP) and Stress Double Shot Peening (SDSP). The results obtained are summarized as follows: (1) Increased hardness with the diffusion layer between the surface and depth of 400 μm by DSP. (2) Remarkably high compressive residual stresses by DSP: Surface residual stres =-701 MPa, Maximum compressive residual stress=-733 MPa. (3) On the loading condition of stress ratio (R)=0, the fatigure limits of DSP and SDSP materials were 33% and 58% higher than that of N material, respectively. However, on the condition of R=-1, these were 28% and 39% higher than that of N material, respectively. (4) Same fatigue limit of both DSP and EP+DSP materials. (5) On the condition of R=0, the fatigue limit becomes high according to the lager compressive residual stress. However, on the condition of R=-1, the above relation is not necessarily valid to yield of the material by the compressive loading stress.

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The one-sided fastening systems of structures using plastic buckling of the thin pipe are studied in this paper. The plastic buckling occurs in a predetermined annealed area of the thin pipe when the axial compressive load is applied to the thin pipe. Estimations of buckling deformation, load and post-buckling behavior are very important, because the buckling deformations are used as the backside head of fastening the objects, and the post-buckling behavior affect the reliability and the strength of fastening system. The whole fastening process is studied by the nonlinear finite element analysis consistently. In order to evaluate the deformation behavior of pipes in fastening the objects, effects of the parameters such as the length and thickness of the pipe, the band and position of annealed area of the pipe are investigated. Two types of deformation modes of the pipe are found in the analysis, the position of annealed area of the pipe is dominant for the deformation mode, and the optimal values of the parameters are obtained in the analysis.

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This paper shows new fundamental solutions for axisymmetric torsion problems of elasticity. The new fundamental solutions are defined as solutions to the problems of an infinite elastic solid subjected to torsional body forces acting uniformly on area elements. The area elements used here are an annular plane and a cylindrical plane in an infinite elastic solid. A fundamental solution in elasticity is defined as a solution for a point force problem. A fundamental solution for axisymmetric torsion problems of elasticity as usual is defined as a solution to the problem of an infinite solid subjected to a torsional body force acting along a circle. The new fundamental solutions presented here may be regarded as solutions obtained from the fundamental solutions as usual by integrations on the area elements. To obtain the new fundamental solutions, here we use a method of solution for axisymmetric body force problems shown in a previous paper. Applying the new fundamental solutions, we consider the torsion problem of an elastic solid with a rigid cylindrical inclusion or disklike inclusion. Stress singularity at the corner of inclusion is investigated.

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Extreme value analysis has been applied to clarify the statistical nature of the ductile fracture surface associated with the fracture behavior of JIS SS 490 steel. Both the notched tensile specimens with different notch acuity and the unnotched specimens were employed to obtain a wide range of stress triaxiality. The ductile fracture surfaces were composed of variously sized dimples. The dimple size distributions were well expressed by the composite type of Weibull distributions. Whereas, the extreme value probability plots of the maximum dimple sizes in a given unit area were performed to correlate the dominant feature of the ductile fracture surface with the mechanical test results. As a consequence, the parameters that define the maximum dimple size distribution showed a clear dependence on the maximum stress and the fracture strains of the tensile specimens with stress triaxiality varied in four levels. Then, the extreme value analysis of the ductile fracture surface should be recommended as a powerful and effective tool for providing a quantitative information regarding the fracture behavior of the mechanical components.

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The effectiveness of the scleral buckling operation, which is one of those most frequently applied to clinical treatment of the rhegmatogenous retinal detachment in the eyeball, strongly depends on the surgeon's experience so that it is usually difficult to achieve a fully satisfactory effect. Aiming at computer-aided operation planning employing the FEM simulation technique, a 2-D FEM program for a coupling analysis of the hyperelastic solid and static liquid has been developed to qualitatively simulate the procedure of this kind of operation. In this paper, a 3-D FEM program that provides all the functions required for simulating the complicated 3-D procedure of the buckling operation, such as solid-liquid coupling analysis, contact treatment between deformed soft tissues and analyses of buckling and suturing process, is developed. An improved algorithm of the coupling analysis which can avoid the time and memory consuming problem existing in that used in the 2-D one as well as an effective approach in treating the contact between deformed soft tissues are employed in this program. After validating its analysis accuracy through a testing analysis, a simulation of the encircling buckling operation procedure is presented, and the results demonstrate the ability of the program to predict the most suitable factors for an effective clinical operation.

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This study aimed to develop a new cell micro-patterning method by controlling material surface affinity of the cell using atomic oxygen beam exposure. Surfaces of low-density polyethylene (LDPE) and tetrafluoroethylene-hexafluoropropylene (FEP) were exposed to the atomic oxygen beam. On the LDPE surface, the roughness measured by atomic force microscopy (AFM) did not change much, however, the oxygen concentration on the surface measured by X-ray photoelectron spectroscopy (XPS) significantly increased that resulted in increase in wettability. Contrary to this, on the FEP surface, the oxygen concentration showed no significant change, but roughness of the surface remarkably increased and the wettability decreased. As a result of the surface modification, affinity of the osteoblastic cells on the FEP surface increased, which was also confirmed by increase in the cell area. Finally, cell micro-patterning on the FEP surface was carried out based on difference in the affinity between modified and unmodified surfaces patterned by a masking method.

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In this paper, first of all, we investigate the linear elastic deformation of circular plate, membrane deformation of circular membrane and their intermediate deformation. It is shown that the deformation in the intermediate pressure range is close to the paraboloid. We describe the possibility of the generation of the paraboloid from circular flat membrane by inflation. When the parameter used for an actual parabola reflector is taken into consideration, it is also shown that corresponding deflection is in the pressure range of the solution of a membrane.

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